a b s t r a c tIn this study, electroluminescent (EL), eddy current (EC) technology, and IeV measurements were used to analyze the soldering-induced damages on crystalline silicon solar modules fabricated by hot-air soldering method. Experimental results reveal that the most common defects, in the order of occurrence frequency, are cracks, gridfinger interruption at busbar (GFIB), and floating solders. High thermal stress is the main cause for the cracks and GFIB, which mostly appear close to the region of silver paste. Floating solder is often observed in a soldering process using materials with high melting temperatures such as lead-free solders. Both GFIB and floating solder induce obvious power degradation. Although floating solder is not easily identified in an EL image, it can be detected by using the EC method. The tensile tests reveal that if more floating solders occur in a sample group, then these samples also show lower tensile strength.

In this study, the quality degradation of Si-based photovoltaic (PV) modules during the aging process was observed by using electroluminescent (EL) technology and was verified by the IV curve measurements in order to find out the occurring timing of damages on solar cells. Furthermore, the influences of solder materials and soldering temperatures on the performance of the PV modules were also studied. Experiment results show that, high soldering temperatures which induce high thermal stress can easily lead to the power loss of the PV modules. Besides, the mechanical properties of the solar cells itself can also affect the degradation rate of the PV modules. On PV modules soldered with SnPb (SP) solder, more than 80% of cell damages occurred during the soldering and encapsulation processes. When SnAgPb (SAP) solder was used, a small part of the cell damages didn't emerge until the initial stage of the thermal cycling test (TC.) This phenomenon is attributed to the reduction of residual stress between the ribbon and the silver paste because of the good wettability of SAP solder.