Shear deformation and thermal cyclic behaviors of Bi solder as high-temperature applications

High-temperature welding, shearing, and thermal cycling tests were conducted using bismuth solder. At temperatures exceeding 603 K, Bi solders demonstrate superior wetting and coating characteristics on Au-plated substrates. Bismuth solders are capable of bonding SiC chips to Cu substrates in a manner comparable to traditional Pb and tin-silver-copper SAC solders. At 298 K, the shear strength of Bi solder is 1.2 times greater than that of Pb solder. Within the temperature range of 448 to 473 K, the shear strengths of Bi and Pb solders are approximately equivalent; however, the shear strength of Bi solder exhibits minimal temperature dependence. Following 1000 cycles of thermal testing, intermetallic compound (IMC) layers, specifically Cu 3 Sn and Cu 6 Sn 5 , were observed at the interface of SAC and Pb solder, accompanied by the formation of voids and a reduction in bonding strength. In contrast, the interface between Bi solder and the substrate remained intact, with no reaction phases detected. These findings indicate that Bi solder is a promising candidate for lead-free high-temperature solder applications.