In recent years, low temperature solder (LTS) has become popular in the SMT industry due to its reduced energy consumption and increased production yields during the soldering process. However, the main solder alloy used in LTS, the tin-bismuth alloy, still poses reliability risks due to its brittleness. In this study, a joint protection epoxy flux was used to enhance LTS PCBAs. Three test groups were used: 1. SAC ball attached component reflowed with LTS solder paste (SAC-LTS); 2. SAC ball attached component reflowed with LTS solder paste with epoxy flux (SAC-LTS-EF); and 3. SAC ball attached component reflowed with SAC solder paste (SAC-SAC). Thermal cycle tests were performed after the samples were assembled. The resistance of the sample did not change more than 20% when using in-situ monitoring for 1000 cycles. Test samples were cross-sectioned to observe the joint condition. Cracks were observed on all samples, and SAC-LTS had the most significant cracking, followed by SAC-SAC. With SAC-LTS-EF, only two joints showed cracking.
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