Solder Joint Structure of Sn-58Bi Solder Paste with Epoxy-based Flux

Non-clean soldering technology and low temperature bonding will be of great significant for applications in electronic industry. A curable solder paste containing epoxy-based flux and Sn-58Bi solder powder was developed. The solder joint covered by cured epoxy shell can be obtained by soldering process. The thermal-curing process of the curable flux was monitored by DSC to ensure the wetting and metallurgical connection between Sn-58Bi and Cu substrate. The microstructure characteristics of the solder joints were analyzed by metallurgical analysis and SEM observation. The factors influencing the structure of the solder joints were analyzed and discussed.