Lead-free on-laminate laser soldering:: A new module assembling concont

We demonstrate lead-free laser soldering of standard industrial solar cells. The laser-soldered contacts stay stable for more than 240 accelerated ageing cycles by humidity-freeze test and withstand peel forces in excess of 10 N/cm. Laser soldering is demonstrated while the cells are lying on the ethylene vinyl acetate (EVA)foil. This permits to connect the solar cells to the lead-free tinned copper ribbons directly on the lamination materials. We also demonstrate soldering on the bottom side by lasering through the glass and the non-polymerized EVA. With the aid of a pick and place robot it thus becomes possible to avoid all string handling. On-laminate laser soldering (OLLS) technique, which permits a high level of automation and process control, induces little thermal and mechanical stress, reduces the handling and should thus be of particular advantage for assembling modules with very thin cells at a high yield. Copyright (c) 2007 John Wiley & Sons, Ltd.