Effect of Strain Rate and Temperature on Tensile Properties of Bi-Based Lead-Free Solder

Abstract

Tensile properties of three Bi-based lead-free solder which are pure Bi, Bi-1.0Ag-0.3Sn-0.03Ge (mass%), and Bi-2.5Ag (mass%) were investigated and compared with that of Pb-rich Pb-2.5Ag-2.5Sn (mass%) solder. Tensile strength of pure Bi is the minimum among solder investigated regardless of the temperature and strain state. Although tensile strength of Bi-based solder is lower than that of Pb-2.5Ag-2.5Sn at 25 C, those of Bi-1.0Ag-0.3Sn-0.03Ge and Bi-2.5Ag improve and become analogous and higher than that of Pb-2.5Ag-2.5Sn at a temperature of 125 C or more. The effect of strain rate on elongation is negligible in solder investigated. Although elongations of Bi-based lead-free solder are lower than that of Pb-2.5Ag-2.5Sn at 25 C, they increase with increasing temperature. While the elongation of Pb-2.5Ag-2.5Sn relatively stable at approximately 20-30% regardless of temperature, elongations of Bi-1.0Ag-0.3Sn-0.03Ge and Bi-2.5Ag become a same level with that of Pb-2.5Ag-2.5Sn at 125 C and 175 C. In particular, the ductility of pure Bi which is about 5% improves drastically at temperatures of 75 C or more and the elongation rises to approximately 60%. From microstructure observation results, it was con rmed that the addition of small amount of Sn and Ge is effective to form ne microstructure. From fracture surface observation results, it was con rmed that brittle fracture occurs at 25 C and the fracture mode changes to ductile fracture when the temperature increases and the ductility improves.

Comparison of Sn‐5Sb and Sn‐10Sb Alloys in Tensile and Fatigue Properties Using Miniature Size Specimens

“…Pb-rich solder containing from 5 to 10 mass% Sn has been used for such applications. However, lead-free high-temperature solder alloys have not been regulated by RoHS directive yet, and such solders are expected to be developed [1,[5][6][7][8]. ese solders need to be equipped with a combination of good mechanical properties, high thermal fatigue properties, and high heat resistance.…”

Comparison of Sn-Sb and Sn-Ag-Cu-Ni-Ge Alloys Using Tensile Properties of Miniature Size Specimens

“…In such applications, Pb-rich solder containing approximately 10 mass% Sn has been used. Although many high-temperature lead-free solder such as Au-based [7], Zn-based [8], and Bi-based solder [9,10] have been investigated as a substitute of Pb-rich solder, the optimum substitute material has not been developed yet. Although Pb-rich solder used in the specific field has not been regulated by RoHS restriction yet, such lead-free solder is expected to be developed [3,7,[9][10][11][12].…”

“…Although many high-temperature lead-free solder such as Au-based [7], Zn-based [8], and Bi-based solder [9,10] have been investigated as a substitute of Pb-rich solder, the optimum substitute material has not been developed yet. Although Pb-rich solder used in the specific field has not been regulated by RoHS restriction yet, such lead-free solder is expected to be developed [3,7,[9][10][11][12]. Generally, both high thermal fatigue reliability and high heat resistance are required for such high-temperature solder.…”