Preparation and performance evaluation of Sn-Bi solder paste

Bi element in Sn-Bi solder paste is easy to oxidize during reflow soldering, forming black oxide and affecting solder joint performance. Therefore, it is very important to improve Sn-Bi solder paste to reduce or even eliminate the black residue after solder joint soldering. In this study, a new Sn-58Bi solder paste was designed to reduce black residue and improve mechanical properties by selecting additives such as solvents, resins, thixotropic agents and antioxidants, as well as different active agents and antioxidants. The results show that the black residue formed after Sn-Bi solder paste soldering is related to Bi and mainly consists of Bi2O3. In addition, the combination of ether as solvent and organic acid as active agent can effectively reduce the formation of black matter, which is conducive to further improve the performance of SnBi solder paste.