Mechanical Properties And Microstructure Of Sn-Ag-Bipb-Free Solder

This paper presents the mechanical properties and microstructure of Sn-Ag-Bi Pb-free solder. Here, the effects of Bi content on the mechanical properties of Sn-Ag-Bi solder such as tensile strength, elongation and deformation behavior are evaluated at cross-head speeds of 0.1 mm/min and 500 mm/min. The experimental results show that at low cross-head speeds, low-Bi Sn-Ag-Bi solder (<5 mass% Bi) and high-Bi solder (about 57 mass% Bi), exhibit relatively high elongation, whereas Sn-Ag-Bi solders with intermediate amounts of Bi exhibit lower elongation. Deformation of low-Bi solders is governed by slip within the Sn phase, and for high-Bi solders (about 57 mass% Bi) deformation occurs by slip at Sn-Bi grain boundaries. Intermediate-Bi solders, on the other hand, do not slip in the Sn phase or at Sn-Bi gain boundaries. At high cross-head speeds, the elongation of both intermediate-Bi solders and high-Bi solders was low and almost constant The impact resistance of these solders was investigated through charpy impact tests, and it is found that Bi has a marked effect on impact resistance. The impact absorption energy of Sn-Ag solder decreases rapidly with the addition of Bi.