US CPV Firm Deploys Resistance Welding Tool
Semiconductor equipment firm CHAD Industries is set to do away with manual attachment of metallic interconnects to III-V solar cells, thanks to its recently developed automated welding tools.
The company went public with the new tools at the end of January, although a US concentrating photovoltaic (CPV) system manufacturer has used them for the past year.
After using the system to weld interconnects to the cells before they are integrated into larger modules, the customer then brought a second tool into production around six months later.
While being welded, triple-junction cells are protected from damage by the parallel gap resistance welders used in the system, made by Japanese welding specialist Miyachi Unitek. Resistance welding generates little heat and offers excellent process control, according to Scott Klimczak, CHAD Industries president.
“The customer had developed a manual process that we used as our base line for the technology," Klimczak told compoundsemiconductor.net. “Working with the customer and Miyachi Unitek we used the existing manual process and defined the specification for the fully automated process."
The welder also features a robot with specially tooled grippers and weld nests. It can handle a variety of interconnect materials.
Once a process is programmed into the tool it employs a vision system that allows closed-loop control, sensing process errors and keeping them to a minimum. It both inspects the cells, and locates them prior to welding.
“The interconnects are placed to within plus-or-minus 0.002 inches relative to the contacts on the solar cell," Klimczak said. “This placement accuracy is required to bond as large an interconnect as possible to the cell and to maintain as much active area on the solar cell as possible."
At its Anaheim, California operation CHAD Industries has evolved GaInP/GaAs/Ge cell expertise by developing feeding and handling systems for satellite photovoltaic applications. It also develops systems for handling other non-standard semiconductor wafer products.
“Welding, as an interconnect bond, is more robust than other technologies," Klimczak asserted. “This technology has been used in space application for years, which have greater environmental challenges than terrestrial."