The impact of material composition and process parameters on the cSi solar cell interconnection

In this paper the effects of soldering process parameters and used materials on wettability characteristics and the mechanical properties in photovoltaics solder joints were investigated. The soldering and wetting behaviour of solder joints and its industry standard testing methods has been well studied in electronics packaging applications [1–3]. In photovoltaics lesser extent is made to characterize solder joint formation and their influencing parameters, such as process parameters, surface finishes, fluxes, solder composition, etc. [4–6]. In several experiments we focused on a comparative characterization of different process parameters, a variation in solder alloys and the aspects of different solar cells for solar cell string assembly. The mechanical strength of the solder joint interconnection was measured by mechanical pull tests, correlating the force-way-sequence with the fracture mode alongside the pad structure. We conducted wetting balance and surface measurements on solar cell metallizations, indicating the significant difference between used cells and surface finishes on the interconnection process for the equipment suppliers.