Evaluation of the Mechanical Strength of Solar Cell Solder Joint Interconnects and Their Micostructural Properties by Developing a New Test and Inspection Equipment

摘要

The expected life time of a PV solar cell is 20-25 years. Therefore the quality and reliability of materials andprocess parameters of cell connecting solder joints has to be assured. A standardized method or clearly definedgood-bad-criteria are not available for testing busbar interconnects in PV products. Thus a comparison ofmodule manufacturers, cell types, base- and joining materials or joining technologies is not possible. Due to thelack of standards and commercial available test equipment PV module manufacturers often implement their owntest solutions and specifications. These mostly have limited scientific proof, are difficult to interpret and lackoptimisation. The most commonly used test for solar cell ribbon interconnects is the pull or peel test, as used inmicro-electronics. For thin, brittle, large area silicon solar cells substantial modifications of the test equipmentand methodology are required to realize a suitable metrology. In addition the factors influencing the defectconditions in multi crystalline material, high strains around the solder connect, inhomogeneous contactinterfaces has to be considered. Results show the development, optimization and evaluation of a test method forsoldered bus bar interconnects on silicon a solar cell that is independent of product, manufacturer and cellassembly. A comparison between this new method, its results and the previously mentioned issues is made. Thetest method demonstrates how cell breakage during a test can be avoided by optimising how it is mounted andguided.