In this study, electroluminescent (EL), eddy current (EC) technology, and I-V 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. (c) 2015 Elsevier Ltd. All rights reserved.