Numerical analysis on thermal crack initiation due to non-homogeneous solder coating on the round strip interconnection of photo-voltaic modules

Abstract

Solar energy is one of the most widely used renewable energy sources, with photo-voltaic (PV) solar cells/panels now utilized as an important energy source. The strip interconnection between solar cells (used for collecting current from solar cells) is a key PV module component; as poor interconnection reliability can lead to PV module failure. Multi-Busbar is a new type of interconnection which incorporates several round copper wires to help increase the energy conversion and transmission efficiency of PV modules and also to reduce the material costs. The non-homogeneity of the solder coating on the wires (resulting from manufacturing process faults), is one of the main factors that is responsible for the poor connections between the wire and the silver pads; which adversely impacts on the interconnection strength and long term reliability. This paper concerns an investigation of the effect of solder coating non-homogeneity on the thermo-mechanical response of round wires used for PV module interconnections. The study evaluates the two main parameters of non-homogeneity (out of centre value and direction), and also investigates the effect of geometrical parameters. The Extended Finite Element Method in ABAQUS software was used to determine the micro-crack initiation temperature and location for a given joint design. The results show that the cracking temperature is most affected by the direction of solder coating non-homogeneity and the downward vertical direction of out of centre positioning of copper in the solder coating leads to the most reduction in cracking temperature (up to 21%).