New discovery of ZnO whisker in SnZn/Cu solder joints interconnection in concentrator silicon solar cells solder layer

In this work, we have found the formation of ZnO whiskers in SnZn/Cu solder joints interconnection in concentrator silicon solar cells solder layer. Different morphologies of ZnO whiskers were precipitated from rich-Zn phase. During oxidation, the diffusion of Zn atoms induces the formation of voids. The volume expansion (near surface zone) and volume shrinkage (inner zone) both appear in the microstructure matrix, and the tensile stress resulting from oxidation is the driving force for ZnO whisker growth. Net-type oxidation morphology along the triangular grain boundary resulting from that Zn diffuses onto the free surface along the grain boundaries of Sn was found synchronously.