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The Solar Bill of Rights

2011-09-12T16:06:00.000-07:00

From: http://www.solarbillofrights.us/solar-bill-of-rights.html

We declare these rights not on behalf of our companies, but on behalf of our customers and our country. We seek no more than the freedom to compete on equal terms and no more than the liberty for consumers to choose the energy source they think best.

1. Americans have the right to put solar on their homes or businesses

Millions of Americans want to put solar on the roof of their home or business, but many are prevented from doing so by local restrictions. Some homeowners associations have prevented residents from going solar through neighborhood covenants, which allow for the association to veto any changes to a property’s aesthetics. Some utilities and municipalities have also made it prohibitively time-consuming and/or expensive to have a system permitted or inspected.

2. Americans have the right to connect their solar energy system to the grid with uniform national standards

Currently, each state (in some cases, each utility) has a unique process for connecting solar systems to the local electricity grid. National interconnection standards will create a uniform process and paperwork, creating a simple process for the homeowner and a standardized physical connection for manufacturers. Connecting a home solar system shouldn’t be any more complicated for the homeowner than setting up an Internet connection.

3. Americans have the right to Net Meter and be compensated at the very least with full retail electricity rates

Residential solar systems generate excess electricity in the middle of the day, when the owners aren’t usually at home. Net metering requires the utility company to credit any excess generation to the customer at full retail rates at a minimum – effectively running the electricity meter backwards when the system is generating more electricity than the occupants of the house are using. Allowing customers to net meter is critical to making solar an economically viable option for most homeowners.

4. The solar industry has the right to a fair competitive environment

The highly profitable fossil fuel industries have received tens of billions of dollars in subsidies from the federal government for decades. In addition, fossil fuel industries are protected from bearing the full social costs of the pollution they produce. The solar energy industry and the public expect a fair playing field, with all energy sources evaluated based on their full, life-cycle costs and benefits to society. Therefore it is critical that solar energy receive the same level of support, for the same duration, as the fossil fuel industry.

5. The solar industry has the right to produce clean energy on public lands

America has some of the best solar resources in the world, which are often on public lands overseen by the federal government. But even though oil and gas industries are producing on 13 million acres of public lands, no solar permits have been approved. Solar is a clean, renewable American resource and solar development on public lands is a critical component of any national strategy to expand our use of renewable energy.

6. The solar industry has the right to sell its power across a new, 21st century transmission grid

Over the last 100 years, the transmission grid in the United States has been built as a patchwork of local systems, designed and planned to meet local needs. As the needs of customers have changed, so has the way the electric industry does business. What haven’t changed are the rules crafted in an era of coal-fired power plants. What is needed now is an investment in infrastructure to connect areas rich in solar resources with major population centers.

7. Americans have the right to buy solar electricity from their utility

Many utility companies have never considered offering their customers the option to purchase clean solar energy, rather than dirty energy from coal or other fossil fuels. Nation-wide over 90 percent of people support increased use of solar energy, and over three-quarters believe it should be a major priority of the federal government. Despite this, only around 25 percent of utility customers in the U.S. have the ability to actually purchase clean, renewable power from their utility, and only a fraction of those programs offer solar energy. Utilities should be required to offer the electricity source that their customers want.

8. Americans have the right to – and should expect – the highest ethical treatment from the solar industry
Solar energy systems are an investment as much as a physical product. Consumers deserve top-quality information and treatment from solar energy providers and installers. Consumers should expect the solar industry to minimize its environmental impact and communicate information about available incentives in a clear, accurate and accessible manner. Finally, consumers should expect that solar systems will work better than advertised, and that companies will make every good faith effort to support solar owners over the life of their systems. Read SEIA’s code of ethics.

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DSSC..Similar to Semiconductors

2011-09-01T10:44:00.000-07:00

The basic dye cell manufacturing steps also resemble the approaches taken by the semiconductor and packaging industry. For example, a screen printer is typically used to apply titania and other layers to the Transparent Conductive Optical (TCg or TCO) glass. Nanocrystalline TiO2 pastes are screen printed onto the TCO glass, then dried and fired in a continuous belt furnace. The sintering process allows the titanium dioxide nanocrystals to partially “melt” together, in order to ensure electrical contact and mechanical adhesion on the glass. All these furnaces are typically modified from standard thick film furnaces.

After dye staining and anode side application of proprietary current collectors, platinum catalyst is obtained by using the Pt-Catalyst T/SP product which can either be squeegee printed or screen-printed using a polyester mesh of 90. The solar cell needs to be dried at 100°C for 10 minutes before being fired at 400°C for 30 minutes. During the assembly, sealing and filling processes, TCO glass with the completed Titania layer is mated to the cathode current collector, protective glass plate, sealed, busbar attached to the cell and then the cell is filled with electrolyte. Custom designed, fully automated and efficient cell assembly, sealing and electrolyte filling machine sets are required for these production steps.

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Solar Cell Manufacturing in the Second Generation

2011-08-31T13:17:00.000-07:00

Second generation solar cell, also known as thin-film solar cell (TFSC) or thin-film photovoltaic cell (TFPV), is made by depositing one or more thin layers (thin films) of photovoltaic material on a substrate. The most advanced second-generation thin film materials in use today are amorphous silicon (aSi), cadmium telluride (CdTe), and copper indium gallium selenide (CigS). The thickness range of such a layer is wide and varies from a few nanometers to tens of micrometers. is thin-film now the way to go? There are certainly many good reasons for moving to thin films for the solar cell manufacturing process.

1. Thin film deposition.

Copper indium gallium selenide (CigS) is used for the thin film active layers in CigS solar cells, commonly formed using

sputter deposition. During this vacuum-based process, a plasma of electrons and ions is created from inert argon gas. These ions dislodge atoms from the surface of a crystalline material which is then deposited to form an extremely thin coating on a substrate. Depositing thin film by sputtering is the same process used in semiconductor manufacture and in packaging.

2. Thin film annealing.

After sputtering, the thin film needs to be annealed to achieve optimum results. it is also possible to inject additional chemicals during the annealing process. An annealing furnace is similar to the brazing furnace commonly used in packaging industries. The muffle is typically made of SUS 316L material to ensure good corrosion resistance for the thin film solar panel’s corrosive environment. A typical belt furnace can anneal up to 600 x 1200mm (23.6 x 47.2-in.) thin film solar panels after thin film deposition.

3. Metallization.

Like its first generation cousin, the manufacture of thin film solar cells need Al or Ag screen printing metallization, originally invented for the thick film process. Such metallization pastes or inks can be used on both rigid (glass, silicon) and flexible (polyimide, polyester, stainless steel) substrates. The metallization can be accomplished through either thermal curing or firing.

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The Screen-Printing Method

2011-08-30T09:51:00.000-07:00

The screen-printing method consists of a thick film metal paste that is composed of metal powder, glass fritt, solvent and non-volatile polymers that are blended together in a three roll mill. A squeegee applies a downward force on the paste moving it across the screen that has a deposition pattern within. This action creates a reduction in viscosity of the paste so it can penetrate into the screen holes. This way, the metal paste is deposited in select patterns onto the substrate. The factors that affect the screen-printing process include snap off distance, squeegee pressure and squeegee speed.

The snap off distance is the distance between the screen and the wafer. During the printing process, when the paste is printed onto the screen, a downward force is applied to the screen. The screen, being elastic, restores its shape and this upward movement aids in the deposition of the paste. If the snap off distance was too high, then pressure will have to be applied to force the paste onto the wafer. If it is too low, the paste might not get released from the screen. The pressure applied also plays an important role in the deposition of the paste. When too much pressure is applied, excessive paste from the screen could be deposited which can break the wafer. On the contrary, when too little pressure is applied, the paste might not get released from the screen at all. The speed of the squeegee movement also determines the print quality. If the speed is too high, the paste can miss many holes and lead to a non-uniform deposition.

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Principles and Advantages of Ultrasonic Belt Cleaning

2011-08-29T09:59:00.000-07:00

In an ultrasonic belt cleaner, the solvent vibrates at ultrasonic frequencies. These ultrasonic waves cause extremely rapid pressure decreases and increases in the fluid. The sudden decrease develops instants where the water can no longer exist in a fluid state and, as a result, gas bubbles form. In other words, water can only exist in a liquid state above a minimum pressure (the threshold of cavitation). When the pressure decreases below the critical pressure, the water becomes a gas and evaporates. Then, at the ensuing increase in pressure, the gas bubbles will collapse again. This process of creating minute bubbles in the liquid is known as cavitation and it is responsible for the scrubbing effect that propagates ultrasonic cleaning.

Simply put, the advantages of using ultrasonic belt cleaning technology have to do with precision, speed, and consistency. Ultrasonic energy infiltrates obscure regions of the belt, which means that all areas of the belt will be categorically cleansed. Ultrasonic cleaning also works faster than any other conventional cleaning procedure in the elimination of contaminants. Due to the efficiency of ultrasonic antisepsis, the labor saving advantages designate ultrasonic technology as the preeminent economical design in cleaning furnace belts. And, unlike manual cleaning (like using a steel brush) ultrasonic technology offers incomparable cleaning consistency throughout the entire belt.

Using a steel brush as a tool for cleaning the belt, on the other hand, can often be time-consuming, imprecise, and inconsistent. A steel brush uses steel wire bristles to clean the surface area around the belt, however, due to its abrasive nature and inability to reach abstruse regions of the belt, it does not obtain the cleaning capabilities that an ultrasonic belt cleaner can easily handle.

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What a DSSC is!

2011-08-25T09:42:00.000-07:00

A dye-sensitized solar cell is composed primarily of three parts. The first part, the substrate, is the negative terminal. The substrate has a layer of transparent glass on the outside and a coating of transparent conductive oxide (TCO) on the inside. This warrants sunlight to pass through. In the center sector, a layer of dye sensitizers bind to a layer of nano-structured titanium dioxide (TiO2), where the TiO2 is connected to the negative terminal to collect sunlight. All of the layers are then immersed in an electrolyte solution to allow charge transportation. The top part is the positive terminal and it contains a coating of carbon (graphite) or platinum for the purpose of transferring electrons. The outside layer is made of transparent glass and the top and bottom divisions are joined together to prevent the centered portion from leaking.

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A Typical Schematic of a Belt Furnace

2011-08-16T10:20:00.000-07:00

Solar Cell Process Applications for Belt Furnaces

2011-08-15T16:37:00.000-07:00

Thick Film Processing

After a paste is screened onto a substrate and it settles for 5–15 minutes at room temperature, it undergoes oven drying at 100-150°C for 10–15 minutes to remove solvents. Firing is then completed in conveyor belt furnaces at temperatures between 500-1000°C.

Crystalline Silicon Solar Cell Manufacturing

Electrical contacts are usually formed by screen printing. The firing is done in conveyor belt furnaces at a temperature of about 700°C for a few minutes. Upon firing, the organic solvents evaporate and the metal powder becomes a conducting path for the electrical current.

Thin Film Solar Cells Manufacturing
A transparent conducting glass, coated with doped SnO2 or ITO film, is used as a substrate. A thin film, such as CdS, is then deposited through CSS or CBD techniques. The CdS film is heat treated by a conveyor belt furnace in a reducing atmosphere or in the presence of CdCl2 at 400-500°C.

Dye Sensitized Solar Cells (DSSC) Manufacturing
TiO2 nanoparticles have been used extensively to increase the interfacial surface area in Dye Sensitized Solar Cells. Nanoparticle films are generally made by screen printing a paste of titania nanocrystals and then sintering the particles together at 450-500°C in a conveyor belt furnace.

From Wikipedia: http://en.wikipedia.org/wiki/Conveyor_belt_furnace

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What is a Conveyor Belt Furnace?

2011-08-12T14:07:00.000-07:00

A conveyor belt furnace is a furnace that uses a conveyor or belt to carry process parts or materials through the primary heating chamber for rapid thermal processing. It is designed for fast drying and curing of products and is nowadays widely used in the firing process of thick film and metallization processes of solar cell manufacturing. Other names for conveyor belt furnace include metallization furnace, belt furnace, atmosphere furnace, infrared furnace and fast fire furnace, to just list a few.

Normally a conveyor furnace adopts tunnel structure and is composed of multiple controlled zones which include, but not limited to, preheating zone, binder burn out zone, heating zone, firing zone and cooling zone. A conveyor furnace also features fast thermal responses, uniform and stable temperature distribution; it can heat treated parts to 1050 deg. C. (may vary for different model). Belt speed of a conveyor furnace can be up to 6000mm/min. Products are heated efficiently by infrared radiation (it can also be ceramic heaters or IR lamps) and are dried and fired after passing through the controlled zones, followed by rapid cooling.^[1]

^{For more info on belt furnaces please go to www.beltfurnaces.com}

An Educational Video on THT Furnaces

2011-08-11T12:49:00.000-07:00

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CdTe PV panel maker First Solar to supply Sempra's 150MW Nevada plant expansion for PG&E

2011-08-09T15:31:00.000-07:00

This post is from: http://www.semiconductor-today.com/news_items/2011/AUG/FIRSTSOLAR_040811.html

Pacific Gas and Electric Company of San Francisco, CA, USA (a subsidiary of PG&E Corp) and Sempra Generation (a subsidiary of San Diego-based Sempra Energy) have entered into a 25-year contract for 150MW of renewable power from an expansion of Sempra Generation's Copper Mountain Solar complex in Boulder City, NV.

First Solar Inc of Tempe, AZ, USA will provide the ground-mounted cadmium telluride (CdTe) thin-film photovoltaic (PV) panels and serve as the engineering, procurement and construction (EPC) contractor for the project.

Construction on the 1100-acre solar plant should begin in early 2012. The first 92MW of panels at Copper Mountain Solar 2 should be installed by January 2013, with the remaining 58MW due for completion by 2015. Under the terms of the contract, PG&E has the option to accelerate the commercial operation date of the second phase. When fully developed, Copper Mountain Solar 2 will produce enough electricity to power about 45,000 homes.

Copper Mountain Solar 2 is a step in Sempra’s plan to construct 1000MW of additional renewable capacity by 2015, says its president & CEO Jeffrey W. Martin. The plant is Sempra’s third and largest solar project in Nevada, and will supply power to California consumers. The power supply contract between PG&E and Sempra is subject to approval by the California Public Utilities Commission.

“The combination of First Solar’s advanced thin-film PV modules with our industry-leading EPC capabilities enables us to rapidly deploy utility-scale solutions like Copper Mountain Solar 2, bringing down the cost of renewable energy,” says Jim Lamon, First Solar's senior VP of EPC, operations & maintenance.

Sempra Generation and First Solar have previously teamed-up on the construction of two other large-scale solar projects in Nevada, including Copper Mountain Solar 1. The 48MW installation was completed in late 2010 and is currently the largest photovoltaic solar power plant in the USA. PG&E is currently delivering the power produced at the plant to its customers.

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Competitive Market Advantages for DSSC Manufacturing

2011-08-02T10:24:00.000-07:00

The production of DSSCs incur relatively low cost: new patented technologies will result in less than $1.5 ppw for module manufacturing cost at initial production, dropping to about half this figure ($0.7 ppw) on the basis of economy of scale from multiple plants as opposed to more than $3 ppw today.

DSSCs have an additional advantage in that they are particularly suited to warmer climates. When hot, crystalline silicon modules lose efficiency far more than do dye cells.

DSSCs also work well in a wide range of lighting conditions and orientation, and they are less sensitive to partial shadowing and low-level illumination compared to silicon.

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Furnace for Firing Operation in Silicon Solar Cell Manufacturing

2011-08-01T13:41:00.000-07:00

A microprocessor based PID controller controls the furnace. Type K thermo-couples are used for determining the zone temperatures. Controls are located on the right hand side and can be viewed from the entrance of the furnace. The central processing unit (CPU) is mounted under the exit table. The furnace is controlled by a microprocessor based controller system and the CPU is loaded with a Windows operating system that allows for easy computing. The computer system comes with a pre-installed program for controlling the Confurnace parameters including the belt speed and the zone temperatures. Temperature profiles can be stored and retrieved for future purposes. Thermocouple ports are located at the entrance table for connecting the profiling thermocouple directly to the microprocessor. This feature allows the monitoring and recording of the actual temperature experienced by the part. Software is also provided with the computer to capture, display, printout and store the furnace profile. The furnace is equipped with a redundant overheat safety protection system which incorporates an additional type “K” thermocouple in the center of each controlled zone and the multi-loop alarm.

For more information and specifications go to http://www.beltfurnaces.com/HSHsolar.html

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Improving Energy Conversion Efficiency for Solar Cells

2011-07-28T11:35:00.000-07:00

This is an excerpt from "Study of the Effect of the Firing Process to the Energy Conversion Efficiency of Solar Cells" by KIC and Top Solar...

Over the last few years, solar cell manufacturers have strived to improve energy conversion efficiency at a lower cost. Optimizing the metal electrodes firing process in furnaces is a common way to achieve this goal. This was overlooked in the past. Most of the time, such thermal process work was done mainly by experienced engineers without much in-depth engineering study and development.

In summary, the accurate measurment of the cell profiles and optimization of the furnace’s temperature settings during production play an important role in process control. Frequent tracking on the furnace’s temperature, collecting and analyzing measurement data can help optimize the firing process and find a suitable process window. The end result is the production of higher efficiency cells, stable production quality and reduced production cost.

To read the entire whitepaper go to http://www.beltfurnaces.com/KIC_Topsolar.html

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Wafers: Thermal Process Development

2011-07-25T10:26:00.000-07:00

This is an excerpt from..

A Practical Guide for Improving Crystalline Solar Cell Efficiencies through
Optimization of the Firing Process

by Bjorn Dahle, KIC

As opposed to more mature industries such as semiconductor and electronics assembly, the solar industry currently does not have a clear understanding of the ideal wafer profile or process window for each unique application (wafer, silver paste, furnace and other variables). There may be numerous wafer properties and variables in the processes upstream from the metallization furnace that affect the ideal wafer profile. Therefore, each manufacturer must perform a design of experiment (DOE) to identify the best wafer profile or range of profiles (Process Window). Such a DOE typically involves changing the wafer profile while the cell efficiency, fill factor and other quality measurements are measured. The profile is changed numerous times (on identical wafers that have been processed up to the firing furnace) in a “trial and error” approach until the responsible engineer is satisfied with the cell efficiency.

The wafer profile itself is a result of the furnace settings and how the thermodynamic properties of the furnace heat and cool the wafer. A modern metallization (firing) furnace can be set up using tens of millions of alternative recipes (combination of zone temperatures and conveyor speed), making the DOE both difficult and time consuming. Even worse, when changing one profile parameter, e.g. the peak temperature, all the other parameters such as time above 500°C, time above 600°C, ramp rate, etc. also change. As a result, it becomes difficult to determine what caused the improvement in the cell efficiency.

Finally, the traditional methods to record the wafer profile suffer from inaccurate and non-repeatable measurements. This problem is caused by the method used to attach the thermocouples (TC) to the wafer. It is not uncommon to get a 50°C difference in peak temperature readings from one profile to the next when taken only minutes later. Clearly, a new TC attach method is required before any purposeful DOE can take place.

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Furnace for Thick Film Application

2011-07-21T09:42:00.000-07:00

HSK series belt furnaces serve diverse industries such as microelectronics packaging, which include IC, SMT, HIC, MCM and MEMS applications, and advanced materials, including thick film, electronic component, photovoltaic cells, ceramics and metals processing applications.

The HSK series fast fire furnace heats from ambient to 1050°C in approximately 40 minutes and is designed to sustain continuous on/off heating and cooling cycles resulting from alternating periods of production and non-use. It features an ultra-clean low-mass refractory heating chamber equipped with FEC (Fully Enclosed Coil) heaters formed into ceramic insulation panels. With the use of advanced insulation materials, lower thermal capacity enables the furnace to warm up and cool down very quickly and lose less heat to the environment.

The furnace is monitored by type “K” thermocouples in the center of each heated zone. Each temperature zone is control-led by its own SHIMADAN SR94 single loop intelligent temperature controller with full auto-tuning PID. The single wave, zero trigger method enables precise and stable temperature control, avoiding damages to the peripheral equipment while prolonging the life of controlling devices at the same time.

The furnace belt is balanced spiral Nichrome V mesh. The belt speed is programmable in IPM with readout right on the monitor and deviation from set point alarm is also programmable. Stepless speed regulation is controlled by FUJI frequency converter and is digitally displayed.

The furnace is equipped with entrance/exit curtains and an exhauster to improve drying/firing temperature stability, as well as, to keep the firing chamber clean. The 200mm (8”) diameter air powered Venturi exhauster supports full chamber width exhausting. There are removable condensate collection traps and the exhaust flow can be adjusted by the flow meter.

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Firing in the Thick Film Process

2011-07-20T15:52:00.000-07:00

After the paste is screened onto the substrate, it is commissioned to level for 5 to 15 minutes at room temperature, followed by oven drying at 100°C to 150°C for another 10 to 15 minutes. Firing takes place in continuous furnaces.

Air-fired and nitrogen-fired systems are more commonly used. In the initial firing phase (200°C to 500°C), organic resins are burned off in the burnout zone. In air-fired systems, the polymer decomposes by simple oxidation. The byproducts of the burnout zone are primarily CO₂ and H₂O, as well as, lightweight fly ash. In the nitrogen-fired system, cleavage of the polymer at the ethyl groups and dehydrogenation take place. This produces a complex mixture of polymers, monomers, and gases that burn off as gases, vapors, and droplets.

As the climate rises to peak firing temperature, metal particles begin to sinter, glass frits begin to soften and flow, and a film is gradually formed. The material is held at peak temperature for 10 minutes then cooled down. After it cools down, pastes are formed firmly onto the substrate. The entire cycle lasts for about 30 to 60 minutes.

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Printing in the Thick Film Process

2011-07-19T10:02:00.000-07:00

The selective deposition of thick-film materials onto a substrate essentially depends on forcing ink through a stencil, screen, or mask mounted under tension on a metal frame. Stainless steel mesh screens are the most commonly used for hybrid thick-film printing while etched metal masks are sometimes used for high precision purpose.

The circuit pattern is formed photographically on the mesh using ultraviolet (UV)-sensitive filler emulsion. The appropriated paste to be printed is placed on one side of the screen. A polyurethane squeegee is used to force the paste through the open meshes. The pressure applied to the squeegee must be sufficient to ensure complete filling of each aperture before the squeegee edge passes over the aperture, but not high enough to cause spreading of the paste between the screen and the substrate.

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Thick Film Hybrids

2011-07-18T09:28:00.000-07:00

Thick-film hybrids are generally used to substitute, interface or interconnect ICs. Hybrid constructions can be either single layer or multilayer. Single-layer circuits are conductor traces printed and fired onto a substrate with the utilization of crossover and pads of insulating dielectric. Three to five layers are common in multi-layer circuit. Connections between different layers are achieved by vias.

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Thick Film Pastes

2011-07-15T09:35:00.000-07:00

Thick film technology is traditionally an additive process, that is the various components are produced on the substrate by applying ‘pastes’ (or ‘inks’) and are added sequentially to produce the required conductor patterns and resistor values. Different formulations of paste are used to produce conductors, resistors and dielectrics (for crossovers or, occasionally, capacitors).

Each paste contains:

- A binder, a glassy frit

- The carrier, organic solvent systems and plasticizers

- The materials to be deposited, typically pure metals, alloys, and metal oxides

The metal particles are bound together and to the substrate by the glassy phase, and this is particularly important at the substrate-ink interface. Fired surfaces are usually not even or homogeneous on a micro scale, a fact which can lead to problems when wire bonding.

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Thick Film Materials (Substrate)

2011-07-14T10:02:00.000-07:00

The majority of substrates are ceramic for their mechanical strength, electrical resistivity over broad range, thermal conductivity and chemical inertness. Alumina has become the most widely used because it to has an excellent combination of all these properties. The 96% Al₂O₃ composition has become an industry standard and is used in 90% of all circuits. The 4% impurities are selected to accomplish complete densification without grain growth and to maximize electrical properties. The most common additives are magnesia and silica. Magnesia inhibits grain growth of alumina crystals and silica is used to form a glassy matrix with alumina that binds the system together.

For high frequency application, ultralow-loss alumina substrate is made by eliminating the glassy phase. This is accomplished by sintering 99.5% pure Al₂O₃ at 1800-1900°C to form high-purity dense substrate.

New substrate materials continue to appear, including ‘porcelainised steel’ (vitreous-enameled steel), organic materials such as epoxies, flexible substrates, and even synthetic diamond.

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Introduction to Thick Film Technology

2011-07-12T09:20:00.000-07:00

Thick film technology is an established method for efficiently manufacturing hybrid microelectronic circuitry. The thick film process can be defined as the sequential printing and firing of conductor, resistor, and dielectric paste formulations onto a substrate.

Thick films are typically in the range 5–50µm thick. This distinguishes a hybrid from thin film technology in which films are deposited by vacuum evaporation or sputtering processes and the thickness is usually less than 1µm. the range of resistivities is 10Ω/square to 10MΩ/square, there are considerable possibilities for building multi-layer structures.

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Advantages and Disadvantages of Glass to Metal Seals

2011-07-11T10:34:00.000-07:00

Advantages of Glass to Metal Seal:

- Extremely high durability
- Mechanical stress and strain resistance
- High shock and vibration resistance
- Chemical stability and resistance
- Absolute hermetic
- Inexpensive and easy to manufacture
- Electrical insulation

Disadvantages of Glass to Metal Seal:

- Unable to cope with large CTE mismatch
- Precise control of glass composition needed

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Copper-to-Glass Seals

2011-07-08T09:27:00.000-07:00

Copper-to-glass seals: Although the CTE difference between glass and copper is large, a satisfactory vacuum seal can be made which utilizes the property of glass to “wet” copper oxide, some of which diffuses into the glass and forms a transition phase. For a satisfactory seal, the oxide layer should be no more than a few tenths of a micron thick and may consist of various oxides.

1. The copper piece is tapered down to a very thin feather edge in order to follow the expansion and contraction of the glass. The feather edge must be smooth and polished.

2. Degreasing and hydrogen-firing at 800°C.

3. The copper piece is usually borated by heating to redness in air and quenching in a concentrated solution of sodium borate. The color of the copper at the seal site should have a uniform deep red to purple sheen.

4. The copper and glass are heated to 1000°C in air and brought together. This is a process called beading

5. Copper-glass seals must be carefully annealed in an oven immediately after glassing

6. The assembly is chemically cleaned to remove the excess copper oxides.

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Housekeeper Seals

2011-07-07T09:37:00.000-07:00

Housekeeper seals can be made with any kind of glass (usually soft glass) if the materials used fulfill the following requirements:

1.     The expansion of the metal part must be larger than that of the glass in order to assure that the stresses normal to the glass-metal interface will always be compressive

2.     The metal used must be soft enough and thin enough to be able to deform plastically, in order to allow dimensional changes which take place in the glass as it cools

3.     The metal must form a strong bond with the glass

4. The shape and dimensions of the seal must be designed so, as to provide a large contact area between metal and glass, avoiding at the same time any tensile stress perpendicular to the surface or too great stresses in any direction

The metal fulfilling all the requirements is copper, but in some such seals platinum, iron (steal) and molybdenum can also be used. Using one or the other of these metals, the seal can be made in various shapes: wire seal, ribbon seal, feather-edge seal or dics seal.

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Fabrication of Glass-to-Metal Seals

2011-07-06T09:25:00.000-07:00

In most glass-to-metal seals, the procedure involves:

1) Oxides formation on metal surface by heating to the proper temperature

2. 2) “Wet” the oxides by fused glass to form a glass-oxide-metal transition

3. 3) Seal the metal-glass bond

It is worth to note that a good hermetic seal can be made without the presence of oxide, e.g., as in the case of platinum.

For more information go to http://www.beltfurnaces.com

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Types of Glass-to-Metal Seals

2011-07-05T09:50:00.000-07:00

There are many types of glass-to-metal seals. These seals can be categorized by their structures.

Internal seals are those in which the metal, in the form of wire, rod, ribbon, or tube, is surrounded by glass.

External seals are those in which a band, tube, or cup of metal adheres to the edge of a glass insert, which may be a round button or disc or it may be square or any other shape, in which ease the stresses are always greater and more complex than in a simple round button or disc. Since glass is much stronger in compression than in tension, the differences in coefficients of expansion of the glass and metal components may be somewhat greater in external than in internal seals. Where expansion mismatch occurs, the ratio between the outside diameter of the tube in an external seal and its wall thickness should not be less than 15:1, with a maximum wall thickness of 0.01 inch. Where expansion coefficient differentials are small, as in Kovar-to-metal seals, these restrictions do not apply.

Tubular seal is “inside tubular” when the metal is surrounded by glass and “outside tubular” when the glass is surrounded by metal. The tubular seals are so-called “Housekeeper” seals. The metal, such as copper or stainless steel, having a widely different expansion coefficient, is formed to a thin edge so that it is able to yield as it expands with heat relative to the glass, and the stresses in the glass do not exceed its tensile strength.

Edge seals are those in which the edge of the metal is embedded in glass. These resemble tubular seals in that they may be either normal edge or “Housekeeper” type, but the geometry and applications differ.

Butt seals are made by sealing a metal disc or ring to the end of a piece of glass tubing.

Window seals may be of any shape, although the round window is subject to less severe and complex stresses.

Combinations of different types of the seals is also possible.

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Intro to Glass-to-Metal Seals

2011-06-30T10:02:00.000-07:00

A true glass-to-metal seal is defined as one in which inorganic glass is heated to the point where intimate contact (“wetting”) is attained upon a hot metal surface and is retained when the glass and metal are cooled to room temperature. The glass and metal components usually have similar Expansion coefficients and rates of expansion.

The glass layer is electrically insulated. Its resistance depends on the types of the glass, the temperature, and the condition of the surface. On the other hand, glass can be given a metallic oxide coating that conducts electricity. The glass can perform under high pressure, vacuum, high temperature, thermal cycling, radiation, shock and vibration, totally inorganic. They will not degrade with time.

Stay tuned for the Glass-to-Metal Seals series of blogs

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From Solarfeeds.com: Making Microchips at 1,300 Degrees C

2011-06-29T12:58:00.000-07:00

This is an article from solarfeeds.com...

"Today's microchips are marvels of nanoscale engineering. A modern microprocessor contains hundreds of millions of transistors packed onto a thumbnail-size piece of silicon. However, our customers are hard at work on designs that will make today’s chips seem crude by comparison.

The semiconducting channel at the heart of each transistor is created, or activated, by quickly heating up the wafer to a set high temperature and cooling it down again, selectively turning the top few atomic layers from an insulator to a semiconductor.

This critical process is called rapid thermal processing, or RTP. Differences of just a few degrees Celsius will change the channel depth enough to affect the whole chip. The effect is small, but at the leading edge, small effects make a major difference.

Applied Materials' Shankar Muthukrishnan discusses the role of RTP in manufacturing microchips and the progression of the technology from the simple furnaces of the 1970s all the way to the state of the art - the Applied Vantage Vulcan RTP system - that was unveiled today."

To read the entire article:

http://www.solarfeeds.com/index.php?option=com_content&view=article&id=17375&catid=321&Itemid=524

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From Solarfeeds.com: Plastic Photovoltaic Film

2011-06-27T15:20:00.000-07:00

Solar Cells have always been very rigid silicon cells, however, now they are being made into flexible plastic films for the purpose of being able to form them into a multitude of shapes. Oh how far we are coming along in the world of photovoltaics. Check out the entire article right here..

http://www.solarfeeds.com/ecofriend/17331-in-focus-plastic-photovoltaics

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What is CIGS?

2011-06-22T09:58:00.000-07:00

This is great information on CIGS! This is an excerpt from an article written by ISET

What is CIGS?

CIGS is a compound semiconductor made up of the elements Copper, Indium, Gallium and Selenium. This material is a very powerful absorber of the Sun’s rays, with demonstrated conversion efficiencies approaching 20% for small-scale CIGS solar cells produced at the National Renewable Energy Laboratory (NREL). A CIGS absorber film requires only 1-2µm of material to convert sunlight into electricity, offering potential for significantly reduced material costs over conventional silicon solar cells.

CIGS films are coated onto substrates that have been metallized with Molybdenum as a back contact to collect electric current. A thin buffer layer of Cadmium Sulfide (CdS) is deposited onto the absorber film, forming a junction between a p-type semiconductor (CIGS) and an n-type CdS layer. A transparent conductive window layer, typically doped zinc oxide (ZnO), forms the top contact of the device, resulting in a complete CIGS solar cell.

As light passes through the ZnO layer, it is absorbed by the CIGS, creating electron-hole pairs. An electric field created at the CIGS/CdS junction draws negatively charged electrons to the ZnO layer, which generates a flow of positive charges in the opposite direction, producing an electric current.

CIGS solar cells can be fabricated on both rigid and flexible substrates, adding to their desirability as the next generation photovoltaic material of choice. When properly sealed and laminated, CIGS modules can deliver stable performance while withstanding exposure to the elements as well as direct solar radiation for over 20 years in the field.

For the entire article go to http://www.isetinc.com/technology-overview.php

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Furnace Brazing Atmosphere

2011-06-20T09:55:00.000-07:00

The furnace atmosphere can be divided into two major parts; Gaseous and Vacuum. The gaseous atmospheres include both active and neutral gases. The neutral gas is generally nitrogen and the active gas will consist of one or several of the carbon monoxide, hydrogen, and hydrocarbon. The gases can be categorized as Reducing, Oxidizing, Carburizing, and Decarburizing atmospheres.

Each active gas can effect the brazing materials. The reducing effect can be balanced by the oxidizing effect. Similarly, the carburizing effect can be balanced by the decarburizing effect. It's important to keep the balance between those active gases in order to achieve atmosphere control.

The brazing atmospheres can also influence the heat transfer and post-braze cooling. The type of gas, the pressure, and the gas flow rate will also influence the heat transfer rate.

Although oxidation should be avoided, an atmosphere with low oxygen and low moisture levels will allow the filler metal to melt and flow into very tightly jointed clearances. The oxygen or moisture present in the joining environment will negatively interfere with wetting. Therefore, the quality of the joint will degrade if the oxygen and moisture levels rise.

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Brazing Thermal Cycle

2011-06-16T09:58:00.000-07:00

Brazing liquifies the alloy at temperatures higher than 450 degrees C and below the melting point of the substrate material. The typical processing temperature is 540-1620 degrees C. The typical brazing process includes preheating (optional), holding, ramp to temperature, brazing, cool down and, finally, exit.

Preheating and Holding- Preheating is done to the temperature below the melting point of the filler metal. It helps stabilize the temperature before heating. The time required for this stage is determined by the parts' thickness and volume.

Ramp to Temperature- The parts should heat quickly and uniformly. The heating time is limited due to the risk of creating distortion from thermal stress build up.

Brazing- Brazing time is the minimum time in which the braze alloy is allowed to flow through the joint. It should be controlled within suitable range depending upon the brazing situation. Theoretically, the joint between the filler and the base form quickly. Extending the processing time can lead to excessive interactions between the filler metal and the base metal, grain growth, and recrystallization.

Cooling and Exit- A controlled cool down within a protective atmosphere allows the joint to solidify. Usually, a temperature of about 150 degrees C will avoid discoloration of parts exiting the furnace.

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Types of Furnaces used for Brazing

2011-06-15T10:41:00.000-07:00

Various types of furnaces are used for brazing which mostly employ either a gaseous atmosphere or a vacuum. The overall furnace construction is based on either batch type or continuous operation. Batch operation includes retort type furnaces used for hydrogen brazing and vacuum chambers for vacuum brazing.

Retort-type Furnaces- Different from other batch-type furnaces in that they make use of a sealed lining called a retort. The retort is made of heat resistant alloys that resist oxidation. It is filled with the desired atmosphere (hydrogen, sometimes mixed with inert gas for safety reasons) and then heated externally by conventional heating elements. Due to the high temperatures, the retort is usually made of heat resistant alloys that resist oxidation. Retort furnaces are often used in batch or semi-continuous versions.

Vacuum-type Furnaces- These are a high capital investment but are extremely versatile and safe, as well as, produce high quality. It offers excellent oxide prevention and is usually used to braze materials with very stable oxides; Such as aluminum, titanium, and zirconium. The three types of Vacuum Furnaces are "single-wall hot retort", "double-walled hot retort", and "cold-wall retort". Furnaces used today are usually based on a cold-wall construction.

Continuous-type Furnaces- These are the best suited for a steady flow of similar sized parts. Often conveyor fed, these furnaces allow parts to move through the hot zone at a controlled speed. IT is common to use either a controlled atmosphere or a pre-applied flux in continuous furnaces. With very low manual labor requirements, these types of furnaces are best suited for large-scale production operations.

For more information visit us at http:www.beltfurnaces.com or contact Torrey Hills Technologies at 858.558.6666

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An Introduction to Furnace Brazing

2011-06-14T16:27:00.000-07:00

Brazing is the oldest method for joining metals, other than mechanical means. It has many advantages over other metal-joining techniques. First, it does not melt the base metal of the joint. It allows tighter control over tolerances and produces a clean joint without the need for secondary finishing. Additionally, dissimilar metals and non-metals (i.e. metalized ceramics) can be brazed. Also, brazing can be easily adapted to mass production which is favored by industries.

Furnaces brazing is a semi-automatic brazing process which has the advantages of mass production. In addition, the process offers the benefits of controlled heat cycle and does not need post braze cleaning.

For more information please contact Torrey Hills Technologies, LLC 858.558.6666

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Videos of Belt Furnaces in Action

2011-06-13T11:33:00.000-07:00

If you want to see belt furnaces in action check out these videos! They will give you a close-up look into how they function and what they're used for!

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THT HSG Series Thick Film Drying Belt Furnace

2011-06-09T07:05:00.000-07:00

Features

Infrared Heating
SUS Belt Conveyor and Tunnel
Long Entrance and Exit Table
Perfect Exhaust Design

Applications

Drying and curing, such as thick film circuit, paste on SMD terminal, etc.

Advantages

Highly efficient; Super light insulation materials; Energy efficient; Multi-zone control; Convenient adjustment.

HSG Series Drying Furnace Models

Model Control Zone Belt Width Overall Length
HSG2705D-0304 3 270mm 8150mm
HSG3004-0304 3 300mm 3260mm
HSG5502-0404 4 550mm 4890mm
HSG6002-0304 3 600mm 3700mm
HSG6006-0303 3 600mm 4075mm
HSG6310-0503 5 630mm 7335mm
HSG6005-0304 Drying Furnace Specifications

Specification HSG6005-0304
Rate Temperature 350 deg.c
Operation Temperature RT+20-300 deg.c
Belt Width 600mm/24"
Heating Length 1500mm/59"
Control Zones 3
Speed Range 100-500mm(4"-20")/min (other speed range as required)
Outside Dimension L3700mm/146" x W1040mm/41" x H1390mm/55"
Net Weight 500kg
Power 240V, 3 phase, 60HZ, 5 wire, 15KVA
Spare Part 2 heating tubes
Options and Customizations

Available Options
Belt Speed Range
Other Power Utility
UPS

Our dedicated engineers will always take the extra step to work with clients for customized designs.

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Advantages of THT's RSA1310-6NH11 Atmosphere Conveyor Series Furnace

2011-06-07T16:07:00.000-07:00

Rated to 1,050° C, the RSA Series has a high-temperature muffle for clean application and features an ultra-clean low-mass refractory heating chamber. The RSA1310-6NH11 heats from ambient to 1,050° C in approximately 60 minutes, and is designed to sustain continuous on/off heating and cooling cycles resulting from alternating periods of production and nonuse. HengLi RSA Series is an energy efficient precision thermal processing system that provides unequaled performance through features such as:

1. 6 channel temperature profiler unit for independent temperature profiling. Includes 3 T.C.,
sampling unit and analyses software, LCD data display and check, RS232 interface to computer.
2. Atmosphere distribution and management system eliminate thermal shock and process
contamination.
3. High-temperature muffle for a clean application.
4. Ultrasonic belt cleaning system including drying system.
5. Windows XP DSC based profiling and monitoring system for monitoring, recording the firing
process, including temperature and speed.
6. UPS for the computer system and conveyor drive for power failure.
7. Extraction of burn-off effluents across entire chamber width improves yields.
8. Stable, special temperature uniformity control ensures consistent "firing" results.

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DSSC Processing Furnaces

2011-06-06T09:53:00.000-07:00

TiO2 nanoparticles have been used extensively to increase the interfacial surface area in Dye Sensitized Solar Cells. Nanoparticle films are general made by screen printing a paste of titania nanocrystals and then sintering the particles together at 450-500°C.

Torrey Hills HENGLI furnaces have secured a dominating position in the supply of DSSC application furnaces. The furnaces' uniform and high-precision heating is indispensible for the improvement of DSSC performances.

For specs and more info on THT/Hengli Furnaces for DSSC go here..

http://www.beltfurnaces.com/dsscfurnace.html

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THT and KIC Working Together

2011-06-03T13:27:00.000-07:00

Torrey Hills Technologies, LLC (THT) and KIC announced in March an agreement to form a strategic business alliance to speed up the optimal thermal process setup of THT belt furnaces through the use of KIC thermal profilers. Under the terms of the agreement, THT will introduce KIC thermal profilers to its current and prospective furnace customers, while KIC will perform all sales and service support associated with the profilers.

"KIC is recognized as the market leader for thermal profilers," said Joyce Zhang, THT’s Marketing Manager. "We welcome their technical expertise, state-of-the-art products and the industry’s best customer support. KIC thermal process tools will help deliver faster furnace setup and higher efficiencies in both high volume production lines and development labs.”

Based in San Diego, KIC is the leader in thermal process development and control products. For nearly three decades it has advanced industries worldwide with their innovative technology firsts. KIC thermal profilers, including KIC Explorer, KIC Vision, and SlimKIC 2000, are great accessories for THT’s belt furnaces. These profilers remove the complexities typically associated with thermal process setup, allowing furnace operators to easily acquire an accurate product thermal profile and quickly achieve the optimal process.

THT will also endorse KIC’s recently developed profiling and thermal process optimization tools for the solar cell manufacturing industry. These tools take advantage of KIC’s extensive technology platform developed in the semiconductor and SMT industries. They are designed for quick and accurate profiling and process optimization for higher efficiency cell manufacturing. The product range includes the SunKIC profiler, the e-Clipse TC attachment fixture, and the Spectrum process optimization software.

"We are pleased to be in partnership with THT and have great confidence that our profilers will enable THT furnace customers to easily reach a whole new level of process improvement and control." said Bjorn Dahle, President of KIC.

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Technological Description of DSSC's

2011-06-02T17:20:00.000-07:00

A schematic depiction of the components and operating mechanism of a typical PV dye cell can be seen at http://www.beltfurnaces.com/dssc.html. The photoanode (facing the light source) is a glass plate whose inner surface has been coated with a thin layer (0.5 micron) of transparent conducting tin oxide (TCO). Onto this layer is coated (e.g. by sintering, other low temperature methods are available such as Electrophoresis) a several micron thick porous layer of nanocrystalline titanium dioxide (particle size about 20 nanometers) on which a monolayer of sensitizer dye is absorbed (ruthenium complex). The cell also comprises electrolyte containing a redox species based on iodide/tri-iodide, and a counter electrode (cathode) consisting of a glass plate also with a conducting tin oxide layer, coated with a few mono-layers of catalyst (platinum was originally used and can be replaced with carbon-based alternatives). In our approach the carbon layer can be applied directly on the Titania. This eliminates the need for a second sheet of FTO glass in the cell.

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Market Advantages for DSSC

2011-06-01T16:07:00.000-07:00

DSSCs have an additional advantage in that they are particularly suited to warmer climates. When hot, crystalline silicon modules lose efficiency far more than do dye cells.

DSSCs also work well in a wide range of lighting conditions and orientation, and they are less sensitive to partial shadowing and low-level illumination compared to silicon.

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Educational Video on Belt Furnaces by THT/Hengli

2011-05-31T10:47:00.000-07:00

If you want to see how belt furnaces work and why they're used check out this educational video on the technology

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What is a Dye Sensitized Solar Cell (DSSC)

2011-05-27T09:53:00.000-07:00

The electrochemical dye solar cell was invented in 1988 by Professor Graetzel of Lausanne Polytechnique, Switzerland. The “Graetzel” dye cell is based on a layer of nano-sized titanium dioxide particles impregnated with dye. Dye cells have been a subject of intense academic interest as more than 50 university research teams around the world have worked to enhance their lifetime, size and efficiency.

Dye cells generate electricity from solar energy using nano-sized titanium dioxide particles impregnated with dye, rather than silicon or similar semiconductors. Using DSSCs will result in unprecedented low costs, both manufacturing line capital cost and module cost per peak watt (ppw). Other solar cell technologies (silicon, thin film) rely on complex vacuum deposition techniques for cell active layer preparation. Not only is the production line for these systems large, complex and very expensive, but the raw materials (such as silicon) are costly and undersupplied. By comparison, dye requires simple equipment (screen printing, air ovens) and benign materials like Titania powder available at low cost.

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Furnace Process Applications and Temperature Profiles

2011-05-26T13:47:00.000-07:00

Efficient design and customization capabilities have enabled our furnaces to be applied in a wide range of processes such as firing, brazing, annealing, sintering, hardening, glass to metal seal, reflow soldering, epoxy curing, hermetic sealing, LTCC (Low Temperature Co-fired Ceramics ), etc.

Thick Film
After a paste is screened onto a substrate and it settles for 5-15 minutes at room temperature, it undergoes oven drying at 100-150°C for 10-15 minutes to remove solvents. Firing is then completed in conveyor belt furnaces at temperatures between 500-1000°C.

Typical Temperature Profile:

Recommendations:
HSG Series Thick Film Drying Furnace
HSK Series Thick Film Firing Furnace

Thin Film Solar Cells
Take CIGS solar cells for example, thin film active layers are commonly formed using sputter deposition. After sputtering, the thin film needs to be annealed at 400-500°C to achieve optimum results. It is also possible to inject additional chemicals during the annealing process.

Typical Temperature Profile:

Recommendations:
HSG Series Photovoltaic Drying Furnace
HSH Series Photovoltaic Fast Response Furnace

Crystalline Silicon Solar Cell
Electrical contacts are usually formed by screen printing. The firing is done in conveyor belt furnaces at a temperature of about 700°C for a few minutes. Upon firing, the organic solvents evaporate and the metal powder becomes a conducting path for the electrical current.

Typical Temperature Profile:

Recommendations:
HSG Series photovoltaic Drying Furnace
HSH Series Photovoltaic Fast Response Furnace

Dye Sensitized Solar Cells (DSSC)
TiO2 nanoparticles have been used extensively to increase the interfacial surface area in Dye Sensitized Solar Cells. Nanoparticle films are generally made by screen printing a paste of titania nanocrystals and then sintering the particles together at 450-500°C.

Typical Drying and Firing Temperature Profiles:

Recommendations:
HSG Series Photovoltaic Drying Furnace
HSK Series Photovoltaic Fast Response Furnace
HSH Series Photovoltaic Fast Response Furnace

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Furnace for Firing Operation

2011-05-25T08:42:00.001-07:00

The HSH series furnace is a specially designed infrared furnace that caters to the needs of the photovoltaic metallization firing requirements. The heating in this furnace is achieved with the help of short wave infrared lamp heaters. The fast response of the IR lamps allow for quick heating. The furnace is rated at 1000 oC and can operate very well in the 750-800 oC range required for sintering of front contact metallization. The belt width comes in various standard sizes, including, 250mm, 300mm and 380mm to match with the requirements of the wafer size. Cooling can be achieved through forced air, as well as, water per requirement. The presence of a muffle helps to control the atmosphere within the furnace, as well as, prevent the external atmosphere from entering. In short, the muffle design helps maintain a cleaner furnace atmosphere. As a standard feature, this furnace is equipped with a steel brush and helps in the cleaning process of the conveyor belt. Ultrasonic belt cleaning is available as an extra option as well.

A microprocessor based PID controller controls the furnace. Type K thermo-couples are used for determining the zone temperatures. Controls are located on the right hand side and can be viewed from the entrance of the furnace. The central processing unit (CPU) is mounted under the exit table. The furnace is controlled by a microprocessor based controller system and the CPU is loaded with a Windows operating system that allows for easy computing. The computer system comes with a pre-installed program for controlling the Confurnace parameters including the belt speed and the zone temperatures. Temperature profiles can be stored and retrieved for future purposes. Thermocouple ports are located at the entrance table for connecting the profiling thermocouple directly to the microprocessor. This feature allows the monitoring and recording of the actual temperature experienced by the part. Software is also provided with the computer to capture, display, printout and store the furnace profile. The furnace is equipped with a redundant overheat safety protection system which incorporates an additional type “K” thermocouple in the center of each controlled zone and the multi-loop alarm.

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Torrey Hills Technologies' photostream

2011-05-20T11:19:00.001-07:00

Torrey Hills Technologies' photostream on Flickr.

If you're interested in seeing photos of our furnaces check out our flickr photostream! Tons of belt furnace pictures from the inside out!

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The HSK Series Furnace for DSSC Application

2011-05-19T09:51:00.000-07:00

The HSK series furnace is an energy efficient precision thermal processing system specifically designed, and most often used, for DSSC applications. It has six channel temperature profiling units for independent temperature profiling with an LCD data display and check, analysis software, sampling unit, 3 T.C., and an RS232 CPU interface. The HSK Series is designed to support continuous on/off heating and cooling cycles resulting from alternating production periods and inactive operation. The heating length of the HSK Series is 3220mm (127”) and includes seven independently controlled heat zones. Process materials are transported through the furnace on a belt that is 350mm (14”) in length with 50mm (2”) of product clearance. The speed of the belt ranges from 40-200mm (2”-8”) per minute and is administered using a digitally displayed variable frequency motor controller. The belt speed is also programmable in IPM with readout right on the PC. The belt material on the HSK Series furnace is Nichrome V mesh (Balanced Spiral) and operates from 480V, 3 phase, 5 wire, 60Hz with a maximum load connection of 42kVA.

The performance of the HSK Series furnace is unparalleled as it can protect itself from over heating, over loading, and low gas pressure. It has an ultra-clean low-mass refractory heating chamber that can increase heat from ambient temperature to 1,050°C in approximately 40 minutes. The temperature of the furnace is controlled by a microprocessor that typically operates from 200-900°C. Each zone is managed using a high performance, single ASIC full auto-tuning PID and a single loop intelligent temperature controller. The HSK Series atmosphere distribution and management system can terminate thermal shock and process contamination, as well as, extract burn-off effluents across the entire width of the chamber for yield improvement. The HSK Series is assembled with entrance/exit curtains and an air powered Venturi exhauster (200mm /8” in diameter) to keep the firing chamber clean while, at the same time, improving temperature stability for drying and firing. The exhaust flow can also be easily adjusted using the flow meter. The HSK Series is readied with a redundant overheating safety protection system that incorporates a type “K” thermocouple (located in the center of each heated zone) and a multi-loop alarm. It ensures consistent ‘firing’ results because of its exceptionally reliable temperature uniformity control. The HSK Series furnace has a removable condensate collection trap and provides emergency off buttons located at each end of the furnace (connected to a 24v emergency off circuit). To see a complete list of the HSK Series specifications please see the chart below.

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Equipment Maintenance and Belt Cleaning Specifics

2011-05-18T10:00:00.000-07:00

- Keep the belt speed under 150 mm/min while cleaning
- Use distilled water rather than tap water as the solvent. Tap water can have impurities, but distilled water that has been degassed allows for a more even distribution of cavitations
- Always monitor the quality of the solvent
- After use, clean out the rinse tanks
- After use, change out the filters

For more on Ultrasonic Belt Cleaning check out the "Technical Data" page at www.beltfurnaces.com

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Steel Brush verses Ultrasonic Belt Cleaner

2011-05-17T13:57:00.000-07:00

Using a steel brush as a tool for cleaning the belt can often be time-consuming, imprecise, and inconsistent. A steel brush uses steel wire bristles to clean the surface area around the belt, however, due to its abrasive nature and inability to reach abstruse regions of the belt, it does not obtain the cleaning capabilities that an ultrasonic belt cleaner can easily handle.

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Advantages of Ultrasonic Belt Cleaning

2011-05-16T10:40:00.000-07:00

Simply put, the advantages of using ultrasonic belt cleaning technology have to do with precision, speed, and consistency. Ultrasonic energy infiltrates obscure regions of the belt, which means that all areas of the belt will be categorically cleansed. Ultrasonic cleaning also works faster than any other conventional cleaning procedure in the elimination of contaminants. Due to the efficiency of ultrasonic antisepsis, the labor saving advantages designate ultrasonic technology as the preeminent economical design in cleaning furnace belts. And, unlike manual cleaning (like using a steel brush) ultrasonic technology offers incomparable cleaning consistency throughout the entire belt.

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Principles of Ultrasonic Belt Cleaning

2011-05-13T10:46:00.000-07:00

What is an Ultrasonic Belt Cleaner

2011-05-11T13:54:00.000-07:00

An ultrasonic belt cleaner is an appliance that uses ultrasound technology and a cleaning solvent to thoroughly scour the furnace belt. The intention is to remove all traces of contamination deposited onto the belt. Sound waves are submitted into a cleaning liquid by means of transducers that are positioned within the cleaning tank. A transducer is an instrument that transforms one form of energy into another. It produces ultrasonic waves in the fluid by altering stature in harmony with an electrical signal vibrating at ultrasonic frequencies. The sound travels throughout the tank creating waves of compression and expansion in the liquid, leaving behind an immense amount of microscopic bubbles that implode before dislodging impurities from the furnace belt. Ultrasonic technology is significantly valuable in furnace belt sanitation as it can deliver ultra-precise and efficient cleaning capabilities.

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The Process of Cavitation in Ultrasonic Belt Cleaning

2011-05-10T16:25:00.000-07:00

Cavitation (essentially a microscopic brush) is the process in ultrasonic cleaning creating rapid formations and violent collapses of gas bubbles or cavities in a cleaning liquid (solvent). Cavitation is responsible for the scrubbing effect, which produces ultrasonic cleaning. It is basically a method of using a transducer in a cleaning solution to create bubbles that literally implode around the parts of the belt that needs to be cleaned. These bubble implosions create a scrubbing action that causes contaminants to dislodge from the belt. The agitation by countless small and imploding bubbles create a highly effective scrubbing action of both exposed and hidden areas of the belt immersed in the cleaning solution. As the frequency increases, the number of these bubbles also increases, while, at the same time, the energy released by each bubble decreases. This means that higher frequencies are ideal for small particle removal without damaging the belt. Cavitation will occur throughout the cleaning solvent if the energy intensity is sufficient. It will also accelerate chemical reactions and the rate at which surface films are dissolved.

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Cavitation: a process that ultrasonic cleaning depends on

2011-05-09T11:09:00.000-07:00

Ultrasonic cleaning depends upon this process of cavitation, the rapid formation and violent collapse of minute bubbles or cavities in a cleaning liquid. This agitation by countless small and intense imploding bubbles creates a highly effective scrubbing of both exposes and hidden surfaces of parts immersed in the cleaning solution. As tyhe frequency increases, the number of these cavities also increases but the energy released by each cavity decreases making higher frequencies ideal for small particle removal without damage of the items being clean.

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THT installation for IBM Research

2011-05-06T09:39:00.000-07:00

Ultrasonic Belt Cleaner

2011-05-05T11:38:00.000-07:00

An ultrasonic belt cleaner, or a sonicator, is a cleaning device that uses ultrasound (usually from 20–400 kHz) and an appropriate cleaning solvent (sometimes ordinary tap water) to clean delicate items. However, ultrasonic cleaners are often used to clean industrial parts and electronic equipment such as a belt furnace! They are even more effective than using a steelbrush. Stay tuned over the next few days as we go more in depth on the details, uses, and pros and cons of using an ultrasonic belt cleaner.

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Temperature Profile and The Temperature Upper Limit

2011-05-04T09:35:00.000-07:00

The temperature profile comparisons clearly indicate that higher sintering temperatures result in larger TiO2 nanoparticles. Which, in turn, result in an overall improvement on the efficiency of the solar cell. The reason being that the larger particles allow for prominent dye absorption, producing higher electron generation. The temperature upper limit is around 600 oC. As you can see, the efficiency drops suddenly due to the instability of the TiO2 nanoparticles. In conclusion, a sintering temperature between 400 oC and 500 oC will result in a highly efficient DSSC.

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Influence of Sintering Temperature on DSSC Performance

2011-05-03T10:06:00.000-07:00

Extensive research has been accumulated on the effects of various temperatures and the efficiency of the DSSC. The current ideal firing temperature is preferred around 450-500 oC, as shown below. High sintering temperatures at 450 oC result in a more desirable contact between the nanoparticles and a stronger adhesion to the substrate than those sintered at lower temperatures. It is important to keep in mind, however, that the DSSC will become unstable at very high temperatures because they have an upper limit of 600 oC to 650 oC.

Process of Sintering in a Belt Furnace

2011-05-02T09:37:00.000-07:00

First, the titanium dioxide layer is prepared by sintering TiO2 nanoparticles at temperature range from 300 oC to 500 oC. The sintering process takes place on the transparent conductive oxide (TCO) glass plate, which is put into furnace heated uniformly for about twenty minutes. This process gets rid of the ambient moisture within the Titania layer, which is needed to ensure electrical contact between the titanium dioxide nanoparticles, and a good adhesion to the TCO (transparent conductive oxide) glass plate. Sintering of the layer can be done at 150 oC, however, it results in less performance than those sintered at 450 oC as mentioned in the research paper written by P.M. Sommeling in ECN Solar Energy. Then the layer is soaked in the dye solution to let the dyes get absorbed into the TiO2 surfaces. At last, the layer is put into a drying furnace. The titania is baked at 100 oC, and allowed for cooling.

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Advantages of DSSC

2011-04-29T14:04:00.000-07:00

The advantages of DSSC compared to other solar electrical generation are that DSSC has a high price/performance ratio, which means it is less expensive to make; it is also light and mechanically robust due to its materials’ properties. With its ultra thin profile, the cells can be made into different shapes to meet specific needs, such as curved or other creative designs. And due to its robustness, DSSCs maintain its efficiency at high temperatures as well. The DSSCs have efficiency between 10%-11%, higher than other thin-film solar panels having efficiency of 5%- 13% in average. What makes it even more attractive is that they work even in low-light conditions, such as during cloudy weather where there is non-direct sunlight.

Materials Selection

2011-04-28T10:08:00.000-07:00

The transparent coating for the negative terminal is made of a thin layer of fluorine-doped tin oxide. It is a substrate that allows sunlight to pass through, meanwhile conducts electricity.
As for the semiconductor, either zinc oxide (ZnO) or titanium dioxide (TiO2) can be used. TiO2 is used and preferred because its surface is highly resistant to continued electron transfer. But it is not sensitive to visible light; it only absorbs small amount of solar photons, therefore, dye sensitizers are needed to attach to the titanium dioxide layer to harvest large portion of the sun light. ZnO has a higher electron mobility compared to TiO2, but has a limited selection of organic dyes, which makes it less desirable until better alternative sensitizers are discovered. Dye-sensitizers can be made of different types of materials. One option is the natural dye, which come from various resources such as blue berries, blackberries, and raspberries. They are easy to come by and good for school training courses or testing purposes. Another option is the synthetic dye, which gives better performance due to its optimized light collection property. The material for the positive terminal layer or the cathode layer can be from either platinum or carbon (graphite). The platinum has a higher efficiency; however, the carbon alternative is easier and less expensive, good for school works or testing purposes.

Electricity Generation Schematics

2011-04-27T14:54:00.000-07:00

Initially, sunlight passes through the transparent conductive oxide (TCO) layer into the dye-sensitized layer causing the electrons within the molecules to excite. The electrons rapidly get injected into the TiO2 particles, which act as a semiconductor, transporting light induced electrons toward the negative terminal. The negative terminal layer, or, the TCO layer, is where all the electrons are collected. Then, the electrons get further transported toward the external circuit, generating electricity. Afterwards, the electrons get reintroduced into the solar cell through the positive terminal into the electrolyte. From here, The electrolyte transports the electrons back into the dye molecules, where the process is repeated. Make sure to Like us on Facebook www.facebook.com/torreyhillstechnologies

Description of a Dye Sensitized Solar Cell

2011-04-25T11:17:00.000-07:00

A dye sensitized solar cell is mainly composed of three parts. The first part, The substrate, is the negative terminal. It has a layer of transparent glass outside, and a coating of transparent conductive oxide (TCO) inside that allows sun light to pass through. The middle part: a layer of dye sensitizers is attached to a layer of nano-structured titanium dioxide (TiO2), which is attached to the negative terminal to collect sunlight, all of which are immersed in an electrolyte solution to allow charge transportation. The top part is the positive terminal. It contains a coating of carbon (graphite) or platinum for electron transfer, and an outside layer made of transparent glass. The top and bottom parts are joined together to prevent the middle portion from leaking.

DSSC

2011-04-22T10:16:00.000-07:00

Dye-sensitized solar cell is the most cost-effective third-generation solar technology available. It was invented in 1991 by Michael Gratzel and Brian O’Regan. Recently, it has attracted more interest due to its low material cost, ease of production, and high conversion efficiency compared to other thin-film solar technologies. However, due to its technical constraints, the actual maximum efficiency is only half the efficiency of crystalline silicon-based solar cells. In an effort to replace the current existing solar technologies, improving its efficiency is critical to widespread adoption of this technology. The process parameters have been reported as having a significant impact in determining the efficiency of the solar cell, as well as, the materials being used.

Crystalline Silicon Solar Cell vs. DSSC

2011-04-21T09:46:00.000-07:00

In manufacturing crystalline silicon solar cells, Electrical contacts are usually formed by screen printing. The firing is done in conveyor belt furnaces at a temperature of about 700°C for a few minutes. Upon firing, the organic solvents evaporate and the metal powder becomes a conducting path for the electrical current. For crystalline silicon solar cells, Torrey Hills Technologies recommends our HSG Series Photovoltaic Drying Furnace or our HSH Series Photovoltaic Fast Response Furnace. In manufacturing DSSC, TiO2 nanoparticles have been used extensively to increase the interfacial surface area in Dye Sensitized Solar Cells. Nanoparticle films are generally made by screen printing a paste of titania nanocrystals and then sintering the particles together at 450-500°C. For DSSC, Torrey Hills Technologies recommends our HSG Series Photovoltaic Drying Furnace, HSH Series Photovoltaic Fast Response Furnace, or our HSK Series Photovoltaic Fast Response Furnace. MAke sure to follow us on twitter www.twitter.com/torreyhillstech

Belt Furnace for CIGS Processing

2011-04-18T09:45:00.000-07:00

A furnace that processes CIGS solar cells should be capable of operating to 650°C or higher. The aim is for a wider belt with superior cross belt uniformity so that larger substrates can be contained in the future. More over, a muffle is required to ensure a cleaner operating environment because various processes in CIGS processing, such as Sulpharization, involves the introduction of different gasses at different time periods. The muffle needs to have the capability to control the gas type and gas flow in each zone. With all of this in mind, Torrey Hills Technologies has designed a furnace that is well suited to match the requirements for thin film solar applications. Figure 4 illustrates a firing furnace that is capable of processing CIGS solar cells and Table 3 lists the technical specifications for the ideal CIGS furnace.

The designed HSA furnace uses ceramic heater boards in order to achieve elevated temperatures. Aside from the standard belt size of 350 and 650mm, wider belts have been designed as well to accommodate wider glass substrates. While a 700mm wide belt has been successfully engineered, efforts are underway to build a belt as wide as 1000mm. As a standard feature, this furnace is equipped with a steel brush for cleaning the conveyor belt, however, Ultrasonic belt cleaning is available as an extra option.

A microprocessor based PID controller is what controls the furnace. Type K thermo-couples are used in determining the zone temperatures and the controls are located on the right hand side of the furnace which can be viewed from the entrance. The central processing unit (CPU) is mounted under the exit table and the CPU is primed with a Windows operating system for easy computing. The computer system is pre-installed with a program for controlling the furnace parameters, including the belt speed and the zone temperatures. Temperature profiles can be stored and retrieved as well for future purposes. Thermocouple ports are located at the entrance table for connecting the profiling thermocouple directly into the microprocessor. This feature allows for the monitoring and recording of actual temperatures experienced by the part. Software is also included with the computer to capture, display, printout and store the furnace profile. Additionally, the furnace is equipped with a redundant overheat safety protection system which incorporates an additional type “K” thermocouple in the center of each controlled zone and the multi-loop alarm.

Effect of Selenization Profile on Solar Cell Efficiency

2011-04-15T09:13:00.000-07:00

The temperature and soaking times play two very important roles in determining the final efficiency of the CIGS solar cell. Many researches have revealed significant evidences for how the different sintering temperatures and soaking times have a direct impact on the efficiency outcome. The results of the experiment by Kadam et al demonstrate that a sintering temperature above 500 oC and a soaking period between 30 and 60 minutes can improve the efficiency of the cell significantly.In his experiments, when the samples were selenized at 400 °C for 10 minutes with a temperature ramp of 6°C per minute, it resulted in smaller, non-faceted grains. This is an indication that either the temperature or the soaking time is inadequate. When the soaking time was increased from 10 to 15 minutes, no significant improvements were noted in the results. Therefore, the ramp rates can be construed as having a larger impact on efficiency. In addition, Kadam et al studied the impact of various heating rates. Changes in the parameters were made: heating rate was increased from 6 °C per minute to 20 °C per minute and the temperature was increased to 425 °C with a soak period of 30 minutes. The resulting solar cell film appeared to be more homogeneous. Furthermore, the temperature was increased to see the effects on the grain size and cell efficiency, which indicated that at 475 °C, the grain size ranged from 0.5 um to 1.5 um with an efficiency of 5.56%. At the same time, they detected that increasing the peak temperatures above 500 °C could also help with improving efficiency. However, at higher temperatures the grains become well faceted and less thick. It is fair to conclude that high quality CIGS solar cells should be prepared at temperatures above 500 °C with an ideal soaking time between 30 and 60 minutes. Understanding that the heat rate, temperature, and soaking times are important factors in determining the ultimate cell efficiency, a belt furnace with a wide range of firing temperatures and a fast heat rate design are desired for constructing highly efficient solar cells.

A little about Torrey Hills Technologies

2011-04-14T10:05:00.000-07:00

Torrey Hills Technologies, LLC is the leader in developing and delivering innovative yet affordable industrial furnace equipment to diverse industries. Our firing and drying conveyor belt furnaces have been widely used in solar cell (photovoltaic's) manufacturing, semiconductor packaging, circuit board assembly, and advanced materials processing (thick film, metals, ceramics, and various electronic components). We have customers located around the world in North America, South America, Europe, Asia, and Australia.Today, we have become a significant player in the supply of fast fire furnaces to silicon, thin film, and 3rd generation solar cell manufacturers. Especially in the production of low-cost 3rd generation Dye Sensitized Solar Cells (DSSCs), our furnaces have secured a dominating position.

Processing CIGS in a Belt Furnace

2011-04-13T10:32:00.000-07:00

The fabrication of CIGS solar cells within a production environment contains the deposition of copper, indium and gallium on the selected substrate material while annealing them at elevated temperatures in controlled atmospheres. First, the substrate material is cleaned and then heated to an elevated temperature. Afterwards, copper, indium, gallium and selenium are deposited through a sputtering process and then the deposited parts are selenized in an elevated temperature profile. The selenization process involves ramping up from room temperature to 450°C in about 4 minute’s. The samples are soaked at this temperature for 7 minutes and then elevated to 550°C for approximately 4 minutes. The samples are then held at 550°C for another 7 minutes and then cooled down. Finally, while held at an elevated temperature, hydrogen sulphide gas is introduced to sulphurization. Make sure to follow us on twitter www.twitter.com/torreyhillstech

Furnace for Firing Operation

2011-04-12T09:34:00.000-07:00

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Belt Furnace Parameters

2011-04-11T10:38:00.000-07:00

Apart from the firing conditions, studies have reported a correlation between the furnace parameters and the efficiency of the solar cell. Edward Bruce has done studies on the influence of belt furnace parameters and solar cell efficiency. He observed that the cleanliness of the furnace has a significant impact on cell efficiency. The common source for furnace impurities include carbon residue, impurities from air inlet, foreign materials picked up by the conveyor due to contact, etc. Solar cells that were fired immediately after cleaning the furnace have been reported as being more efficient than their counterparts that had been fired on a furnace with impurities. The thickness of the oxide layer has also been reported as having a significant impact on cell efficiency. The oxide layer thickness can be controlled, as well, by controlling the atmosphere inside of the muffle. Hilai et al has reported an increase in the conductivity of the silicon solar cell fired within a reduced atmosphere with a small percentage of Hydrogen. The substrate carrier boat has been reported as having very little impact in determining cell efficiency. Results from Bruce et al studies have shown no significant impact in efficiency for directly placing the silicon substrate onto the nichrome belt and firing them on a quart carrier. Check out the full whitepaper http://www.beltfurnaces.com/efficiency_of_silicon_cells.html

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Effect of Soak Time

2011-04-08T09:33:00.000-07:00

Soak time refers to the time at which the substrates with metallization printed on them are held at peak temperature. The soak time is an important parameter in determining the cell efficiency because the diffusion of silicon and silver is a function of time and temperature. Research done by Lee et al, Cooper et al, and Hilai et al have demonstrated the effects of soak time on the efficiency of the solar cell. From the results in the published literature, it is understood that there is a significant interaction between soak time and peak temperature. The highest efficiencies have always been reported for shorter soak time. It has been reported that increasing the soak time will increase the contact resistance. A study, done by Cooper et al, of the interface and bulk metallurgies of the contact, has demonstrated an increase in the thickness of the interfacial glass layer with an increase in soak time. The thicker contact layer results in an increase of contact resistance. Make sure to "like" us on Facebook www.facebook.com/torreyhillstechnologies

Effect of Peak Temperature

2011-04-07T10:24:00.000-07:00

The peak temperature of the sintering process is observed as having a significant impact in determining the efficiency of the silicon solar cell. Studies by Carroll et al have reported a direct correlation between peak temperature and cell efficiency. The results from this study have shown that the ideal peak temperature range for metallization firing is 780-800 oC. Cheng et al has also studied the effects of various peak temperatures on the efficiency of solar cells and has confirmed the same results. The study observed that when the silicon solar cells are under fire, one half of the cells display high contact resistance while the other half displays low contact resistance. At the same time, when the solar cells are fired within the optimum range of 780-800 oC, the contact resistance has been reported as being uniform throughout the entire cell at higher efficiency. However, when the solar cells were over fired, there was an overall decrease in efficiency due to shunting. An investigation by Hilai et al has demonstrated similar phenomena. At lower temperatures, the distribution of Ag was irregular and the contact formed was very small with high specific contact resistance. However, at high temperatures, the excessive shunting resulted in a decrease in efficiency. Thus, from the results of the above studies, it can be observed that the peak firing temperature has an important role in determining the efficiency of the silicon solar cells.

The Firing Process (Sintering) in Silicon Solar Cell Manufacturing

2011-04-06T13:25:00.000-07:00

The firing process, also referred to as sintering, is one of the key steps with which the front-metal contact is formed in a silicon solar cell. In this process, the thick film paste is dried at about 150oC to remove much of the solvents. The presence of solvents can cause excessive out gassing which can lead to cracks and voids. The dried substrates are then fired inside a firing furnace. The firing process consists of four primaries. The first step is the initial temperature ramp up where the paste solvents are volatilized. The second step is the burn out. The objective of the burn out phase is to remove all of the organic binder that was used in paste formation. The burn out phase is carried out at 300-4000C. The third step is the sintering, or the firing process, which is done between the ranges of 700-800C. During this process, the Ag metal forms a bond with the underlying silicon substrate to form metal contact. The final step in the firing process is the wafer cool down phase. The mechanism behind contact formation in a fire through contact is very complex and not fully understood [4]. According to Mohammed Et al, the process starts by evaporating the solvent between 100-200C and then burning out the polymer between 200 and 400C. Later, from 400-600C, the glass frit melts and the sintering of the Ag particles take place. Furthermore, from 600-800C, molten glass with some amount of dissolved Ag etches the silicon nitride anti reflection coating and then reaches the Si surface. Here, it reacts and etches a very thin layer of Si. Ag in the glass will then precipitate onto the Si surface in the form of crystallites. The quality of the contact influences the shunt resistance, series resistance and junction leakage current, which have a significant impact on the efficiency of the solar cell. Hence, it is very important to understand various aspects of the firing process to be able to achieve higher efficiencies. Some of them include; peak temperature, dwell time, and the temperature at which Si –Ag alloy formation happens. Over the next few blogs I will discuss these! Make sure to follow us on twitter www.twitter.com/torreyhillstech

Factors Affecting Screen-Printing Process: Snap Off Distanc, Squeegee Pressure and Squeegee Speed

2011-04-05T09:45:00.000-07:00

Screen Printing

2011-04-04T09:29:00.000-07:00

Torrey Hills Technologies And The Solar Cell Market

2011-04-01T09:27:00.000-07:00

At one time, Torrey Hills Technologies sold in-line continuous furnaces mostly for thick film and brazing applications. Several years ago, in response to the growing demands of the solar manufacturing industry, the company’s engineers reinvented the original technology and adjusted it to different types of solar cell processing. A critical step in solar cell manufacturing is metallization through screen printing. By changing the specifications of thick film drying and firing furnaces, the company stepped comfortably into the solar cell market. Solar technologies have created compelling technical challenges and business opportunities for assembly and packaging engineers. The traditional thick film, thermal treatment and assembly techniques play key roles in solar cell manufacturing. Many skill sets possessed by electronics engineers can be easily reinvented and applied to the solar cell industry. Like us on facebook and join our discussions.. www.facebook.com/torreyhillstechnologies

Dye Cell Manufacturing Similar to Semiconductors

2011-03-31T13:13:00.000-07:00

sintering process allows the titanium dioxide nanocrystals to partially “melt” together, in order to ensure electrical contact and mechanical adhesion on the glass. All these furnaces are typically modified from standard thick film furnaces. After dye staining and anode side application of proprietary current collectors, platinum catalyst is obtained by using the Pt-Catalyst T/SP product which can either be squeegee printed or screen-printed using a polyester mesh of 90. The solar cell

needs to be dried at 100°C for 10 minutes before being fired at 400°C for 30 minutes. During the assembly, sealing and filling processes, TCO glass with the completed Titania layer is mated to the cathode current collector, protective glass plate, sealed, busbar attached to the cell and then the cell is filled with electrolyte. Custom designed, fully automated and efficient cell assembly, sealing and electrolyte filling machine sets are required for these production steps.

Third Generation Solar Cell

2011-03-30T09:56:00.000-07:00

The electrochemical dye solar cell was invented in 1988 by Professor graetzel of Lausanne Polytechnique, in Switzerland. The “Graetzel” dye cell uses dye molecules adsorbed onto the nanocrystalline oxide semiconductors such as TiO2 to collect sunlight. Dye cells employ relatively inexpensive materials including glass, Titania powder and carbon powder. Graetzel’s cell is composed of a porous layer of titanium dioxide nanoparticles, covered with a molecular dye that absorbs sunlight, like the chlorophyll does in green leaves. The titanium dioxide is immersed in an electrolyte solution, above which is a platinum-based catalyst. As in a conventional alkaline battery, an anode (the titanium dioxide) and a cathode (the platinum) are placed on either side of a liquid conductor (the electrolyte). Sunlight passes through the cathode and the conductor, and then withdraws electrons from the anode, at the bottom of the cell. These electrons travel through a wire from the anode to the cathode, creating an electrical current.

Metallization (2nd Generation Solar)

2011-03-29T13:19:00.000-07:00

Thin Film Annealing

2011-03-28T10:20:00.000-07:00

Thin Film Deposition

2011-03-25T10:20:00.000-07:00

Copper indium gallium selenide (CIGS) is used for the thin film active layers in CIGS solar cells, commonly formed using sputter deposition. During this vacuum-based process, a plasma of electrons and ions is created from inert argon gas. These ions dislodge atoms from the surface of a crystalline material which is then deposited to form an extremely thin coating on a substrate. Depositing thin film by sputtering is the same process used in semiconductor manufacture and in packaging.

Second Generation Solar Cell

2011-03-24T10:20:00.000-07:00

Second generation solar cell, also known as thin-film solar cell (TFSC) or thin-film photovoltaic cell (TFPV), is made by depositing one or more thin layers (thin films) of photovoltaic material on a substrate. The most advanced second-generation thin film materials in use today are amorphous silicon (aSi), cadmium telluride (CdTe), and copper indium gallium selenide (CigS). The thickness range of such a layer is wide and varies from a few nanometers to tens of micrometers. Is thin-film now the way to go? There are certainly many good reasons for moving to thin films for the solar cell manufacturing process. Over the course of the next few blogs we will discuss Thin Film Deposition, Thin Film Annealing, and Metallization.

Solar Module Assembly

2011-03-23T09:25:00.000-07:00

Solar module assembly usually involves soldering cells together to produce a 36-cell string (or longer) and laminating it between toughened glass on the top and a polymeric backing sheet on the bottom. Frames are usually applied to allow for mounting in the field, or the laminates may be separately integrated into a mounting system for a specific application such as integration into a building. The basic process is very similar to the SMT process assembly that packaging engineers are already familiar with, albeit on a larger scale. The packaging industry’s lean manufacturing methodology can be applied directly to solar module assembly.

Silicon Wafer Metallization

2011-03-22T15:28:00.000-07:00

Electrical contacts are formed through squeezing a metal paste through mesh screens to create a metal grid. This metal paste (usually Ag or Al) needs to be dried so that subsequent layers can be screen-printed using the same method. As a last step, the wafer is heated in a continuous firing furnace at temperatures ranging from 780 to 900°C. This completes the metallization process, removes solvent and binder, and forms electrical contacts. Metallization is the most critical step. The challenge of reducing wafer thickness for higher efficiency has created stringent requirements for both the equipment and the process itself.

Phosphorus Diffusion

2011-03-21T14:33:00.000-07:00

There are two main layers that are essential to the solar cell’s function. One is a p-type layer, which means that the wafers are boron doped, and an n-type layer created by introducing phosphorus. The silicon wafer usually already starts off by already being doped with boron. in order to form the n-type layer, phosphorus has to be introduced to the wafer at high temperatures of around 870°C for 15-30 minutes in order for it to penetrate into the wafer. The excess n-type material is then chemically removed. These diffusion processes are usually performed through the use of a batch tube furnace or an in-line continuous furnace. According to BTU, detailed cost of ownership models have shown that in-line diffusion can deliver per wafer costs of as low as one third the cost of a batch diffusion furnace. The basic furnace construction and process are very similar to the process steps used by packaging engineers.

First Generation Solar Cells

2011-03-17T15:36:00.000-07:00

Elemental or crystalline silicon is the principal component of most semiconductor devices, most importantly integrated circuits or microchips. Silicon’s ability to remain a semiconductor at higher temperatures has made it a highly attractive raw material for solar panels. Silicon’s abundance, however, does not ease the challenges of harvesting and processing it into a usable material for

microchips and silicon panels. At least three standard manufacturing processes mean that there are technical opportunities for assembly and packaging engineers; Phosphorus Diffusion, Silicon Wafer Metallization, and Solar Module Assembly. We will discuss these three standard manufacturing processes over the course of the next few blog entries!

A brief history on solar cells and the generations of solar cell manufacturing today

2011-03-16T11:22:00.000-07:00

Solar cells grew out of the 1839 discovery of the photovoltaic effect by French physicist A. E. Becquerel. However, it was not until 1883 that the first solar cell was built, by Charles Fritts, who coated the semiconductor selenium with an extremely thin layer of gold to form the junctions. The device was only about 1 percent efficient. Subsequently Russian physicist Aleksandr Stoletov built

the first solar cell based on the outer photoelectric effect (discovered by Heinrich Hertz earlier in 1887). Albert Einstein explained the photoelectric effect in 1905 for which he received the Nobel Prize in Physics in 1921. Russell Ohl, working on the series of advances that would lead to the transistor, developed and patented the junction semiconductor solar cell in 1946. Thin film solar cell annealing furnace. Today’s solar cells can be described as the co-existence of three different generations: crystalline silicon, thin film, and dye. Along with the development of solar cells, there has also been a parallel development of solar cell manufacturing technologies. Assembly and packaging engineers have played a significant role in developing these manufacturing techniques, creating incredible potentials in every generation of the solar business.

Screen Printing and its impact on cell efficiency

2011-03-15T09:46:00.001-07:00

The ideal width of a belt furnace for CIGS processing

2011-03-14T16:04:00.000-07:00

Standard belt size is usually from 350-650mm. However, wider belts have been designed to accomodate wider glass substrates. A 700mm wide belt has been successfully built, however, efforts are underway to build a 1000mm wide belt! For more info on this check out our website at www.beltfurnaces.com

Furnaces by Torrey Hills Technologies

2011-03-10T14:48:00.000-08:00

Check out this video and catch a glimpse of our furnaces!!

Temperature and Soaking time in CIGS solar cell efficiency

2011-03-10T10:09:00.000-08:00

Processing CIGS in a Belt Furnace

2011-03-09T09:37:00.000-08:00

A Typical Fabrication of a CIGS Solar Cell

2011-03-08T10:37:00.000-08:00

A typical fabrication of a CIGS solar cell encompasses the sputtered deposition of molybdenum back contact material on a substrate. The substrate material can be a rigid soda lime glass or a flexible polyimide. The sputtering of the back contact is followed by the deposition of the CIGS absorber layer, CDS buffer layer and the final Zno contact layer. Molybdenum is primarily used as a back contact due to its ability to form an ohmic contact, as well as, inert behavior to corrosive gasses. Cadmium sulphide is used with CIGS material to form an n-type semiconductor material along with a p-type CIGS absorber material. Some of the widely used methods for depositing CdS include chemical bath deposition (CBD), sputtering and closed space sublimation (CSS). Zno is used as the front contact material due to its superior electrical and optical properties.

Thin Film Photovoltaics; A cost effective alternative

2011-03-07T09:56:00.000-08:00

The ever increasing demand and growing cost of silicon has made thin film photovoltaic’s a competing substitute to silicon solar. Thin film photovoltaic (PV) modules are seen as a realistic alternative for a cost effective generation of electricity from sunlight. They are often referred to as the second generation of photovoltaic technology. Some promising materials for thin film solar cells include amorphous silicon, cadmium telluride, CuInSe2 and its alloys. While all of these materials are low band gap, they are all polycrystalline as well leading to a loss in efficiency due to grain boundary recombination. Amid the polycrystalline thin film solar, CIGS solar cells have been documented in various pieces of literature as being unrivalled in efficiency.

Fireclay Tile Slideshow- A THT Furnace Customer

2011-03-02T10:38:00.000-08:00

Check out this slideshow we did for our customer Fireclay Tile!! They purchased a furnace from us recently!

Follow Torrey Hills Technologies on twitter

2011-02-28T14:10:00.000-08:00

Torrey Hills Technologies now has a twitter account! For updates on all the latest furnace news please follow us!! Thanks!

twitter.com/torreyhillstech

Furnace Cross Belt Uniformity

2011-01-17T16:23:00.000-08:00

The cross belt uniformity is an important factor that can have a significant influence on the quality of the fired samples in a conveyor belt furnace. Good cross belt uniformity and temperature stability have been reported to lower the contact resistance in photovoltaic’s and coefficient of thermal resistance in thick film hybrids. With increasing product dimension, especially in thin film photovoltaic’s, non uniformities in temperature across the belt can cause significant temperature gradients resulting in breaking of the substrate materials.

For this reason, our furnaces are manufactured with utmost care to ensure minimal variation across the belt. Our furnaces use a fully enclosed heater board that is designed to provide uniform and stable heat distribution across the entire belt. Also, the use of precise Shimmaden temperature controllers enables the furnace to respond quickly to variation caused by the load. Along with this, the superior insulation design ensures minimal heat loss across the edges of the furnace.

Below is an illustration of cross belt uniformity check performed on a 750mm wide belt furnace. It has been observed that the temperature variations between the centre and the two edges at any instance have always been less than a 2 degree centigrade. This precise control on temperature variations across the belt helps in improving the process yield.

Why Zirconia Oxygen analyzer needs Furnace to warm up before they can show oxygen ppm level

2011-01-14T13:22:00.000-08:00

The Zirconia sensor is a high temperature electrochemical type. The Zirconium oxide, treated with Yitium oxide and plated with platinum on opposite ends acts as the sensor. At elevated temperature, pores are formed in the zirconia lattice allowing oxygen movement from higher concentration to lower concentration, based on the partial pressure of oxygen. To create this partial pressure differential, one electrode is usually exposed to air (20.9% oxygen) while the other electrode is exposed to the sample gas. The movement of oxygen ions across the zirconium oxide produces a voltage between the two electrodes, the magnitude of which is based on the oxygen partial pressure differential created by the reference gas and sample gas.

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