Active Solder Joining Electrical Buss on Photovoltaic Cells

Active solders formulations activated with Ti, Ce, Mg and Ga have been developed for optimum joining to silicon and SiO2. These solders are finding application in the attachment of copper and/or aluminum buss strips to the back planes of photovoltaic cells to direct the current from the cells and create a solar panel.  The paper describes a thermosonic bonding  (process of ultrasonic energy and heat)where these active solders are melted and disrupted to create a strong bond between the back, aluminized surface of polycrystalline Si photovoltaic cells and a copper strip.  The paper will present the active soldering joining process and compare it to conventional soldering processes. It will also present and compare the joint’s metallographic structures, comparative joint peel strengths, electrical resistances and I-V characteristics.