Preparation and performance analysis of a new type of SnZn medium-temperature high-strength lead-free solder paste

A new type of SnZn-based lead-free medium-temperature high-strength solder paste was prepared. The alloy composition was Sn-9Zn-2.5 Bi-1.5In with a melting point of 195 ℃,which has good printing performance and welding performance. The shear strength of SnZn solder paste was studied and compared with the leading SnAgCu solder paste on the market and SnBi solder paste. The results show that the shear strength of SnZn solder paste ishigher than that of the other two solder pastes on the surface tin-plated solder pads（ 14% higher than SnBi system and 25% higher than SnAgCu system）,which is inferior to other nickel-gold pads. Two solder pastes are placed between the two on the OSP pad. At the same time,it was found that SnZn solder paste obtained the highest shear strength of 62. 9 MPa when the maximum temperature of the temperature curve was 215 ℃. By observing the profile of SnZn solder paste solder joints,the element distribution was analyzed and the soldered joints were determined. An intermetallic compound（ IMC） formed on the surface of the disk.