Mechanical Properties and Shear Strength of Sn-3.5Ag-Bi Solder Alloys

Abstract

Mechanical properties and ball shear strength of Sn-3.5Ag-Bi were investigated with Bi addition of 0-9 mass%. Solder characteristics of Sn-3.5Ag-Bi were improved with Bi addition to decrease the melting temperature, to promote wetting to Cu and Ni substrates, and to increase the tensile strength and fracture energy. Shear strength of Sn-3.5Ag-Bi solder bumps increased with Bi addition up to 5 mass%, and was kept almost unchanged with further increase of Bi addition. Shear strength exhibited a parabolic relationship with the tensile fracture energy of the solder alloys.

Interfacial microstructure and shear behavior of Sn–Ag–Cu solder balls joined with Sn–Zn–Bi paste

“…Among the profitable lead-free solders are Sn-Ag-based alloys, holding promise because of their good resistance to thermal fatigue, high ductility [6] and better solderability on copper than Sn-Pb solder [7]. Investigations have been conducted to modify the thermal and mechanical characteristics of eutectic Sn-3.5Ag solder with the addition of Bi, Cu, In, Sb or Zn [8][9][10][11][12][13]. In spite of the compositional modification, the melting points of the Sn-Ag-based solders are still 25-61 • C higher than that of the Sn-Pb eutectic solder.…”

“…The studies on mechanical properties of Sn-Ag series joints are plentiful [1,2,4,7,8,[12][13][14][15][20][21][22][23][24][25]. Packages of Sn-Ag-Cu with introduction of Sn-Zn-Bi are rarely investigated.…”

Electrical resistance of Sn–Ag–Cu ball grid array packages with Sn–Zn–Bi addition jointed at 240 °C

“…The addition of Bi to Sn-Zn near-eutectic solder can improve the soldering properties by lowering melting temperature 3 , 1 0 and strengthening the joint. 7,10,[14][15][16][17] Sn-Ag-Cu packages with the introduction of Sn-ZnBi are rarely investigated. In our previous study, 18 Sn-Ag-Cu/Sn-Zn-Bi packages show higher shear strength than Sn-Ag-Cu joints under thermal aging.…”

Thermodynamic Assessment of the Ni-Bi Binary System and Phase Equilibria of the Sn-Bi-Ni Ternary System

“…Moreover, the Sn-Bi alloy has good wettability with under bump metallurgy (UBM) and high shear strength value compared with other solder alloys. [3][4][5] The Ni UBM is plated on the Cu UBM as a diffusion barrier layer because it restricts the Cu atoms from diffusing into the Sn-based solder matrix, and thus it exhibits a slower reaction rate with the Sn-rich solder alloys than the Cu UBM does. 6,7 Several studies have been made on the interfacial reaction between the Sn-Bi solder and the Ni UBM.…”