Product Briefing Outline: Ultrasonic Systems, Inc. (USI) has released its third generation PV360 for PV wafer coating applications. The PV360 uses nozzle-less ultrasonic technology for highly uniform, thinner coating deposition of solar cells when compared to conventional spray technologies. Optimized for high-volume, in-line manufacturing, the system can process up to 4,300 wafers (125mm sized wafers) per hour.
Problem: For most photovoltaic manufacturing processes, the amount of Dopant applied to a silicon wafer is in the range of 0.0002 to 0.002 ml/cm2 of liquid. This translates to a wet film thickness in the range of 2 to 8 μm. This is very challenging considering that the surface roughness is about 5 μm for many photovoltaic wafers.
Solution: The PV360 delivers liquid coating with transfer efficiency of 95-99%, utilizing a traversing ‘Ultra-Spray’ blade head for greater control of film thickness, down to the sub-micron level. Plus, it offers the versatility to handle the transfer of phosphoric/boric acid and phosphoric oxide dopants, as well as other proprietary coatings. The new PV360 also features a wafer dryer system, dual metering pump liquid delivery system, and state-of-the-art control system with touch-panel interface, all designed to increase manufacturing quality, efficiency, throughput, and reliability for in-line thermal diffusion and laser doped selective emitter (LDSE) processes.
Applications: Precision coating of various dopants such as phosphoric/boric acid and phosphoric oxide for crystalline solar cells, including laser doped selective emitter processes.
Platform: The PV360 utilizes a self-cleaning ‘Teflon’ coated ‘Kevlar’mesh belt to transport the silicon wafers under the traversing Ultra-Spray ultrasonic blade head. The system can be operated in-line or as a stand-alone process. The conveyor width is 914 mm and can accommodate up to six (6) rows of 125 mm wafers.
Availability: September 2010 onwards.