I'm excited about the May 2009 issue of SMT magazine, which will be highlighting photovoltaic soldering applications. Not only does it combine soldering and PV (which is our niche), but it will be including an article written by Karl Pfluke of the Indium Corporation. (Abstract shown below) Karl's one of my personal heroes, he's a veteran technical engineer and leader in solar applications.
Photovoltaic Stringing in Solar Cell Module Assembly
By Karl Pfluke
"As more and more contract manufacturers (CMs) look for opportunities to diversify and fill factory space, photovoltaic (PV) solar cell module assembly seems to be the popular choice. Commonly referred to in the solar panel industry as the "back end process", the assembly is done in lines and has some similarities to SMT.
Solders, solder pastes, solder wire, solder preforms, and fluxes are used for interconnects in PV assembly. Since RoHS and WEEE initiative does not apply to this industry, many manufacturers use SnPb solder for interconnects, Sn60 and Sn62 being the most popular. However, SnAg is occasionally used, and some manufacturers are exploring the use of SAC alloys (SnAgCu), specifically SAC305.
One process, "cell stringing" or "tabbing", uses products quite familiar to the SMT industry. Tabbing ribbon, a precisely straight and flat piece of copper that has been coated with a tightly controlled thickness of solder, is used to connect multiple PV cells.
This article discusses the common solders, reflow technologies, and materials used in PV cell stringing for solar module assembly."
Nice work Karl!