Volume 8, Issue 1 (January 2011)
A Review of Pb-Free High-Temperature Solders for Power-Semiconductor Devices: Bi-Base Composite Solder and Zn–Al Base Solder
Pb-base high-temperature solders (mass % Sn=5–10, melting point (m.p.)=300–310°C) are widely applied under severe conditions, although the harmful nature of Pb is recognized. Bi-base alloys (m.p. of Bi=270°C), Zn-base alloys (m.p. of Zn=420°C), and several Au-base eutectic alloys (m.p. of Au-20Sn and Au-3.6Si=280 and 363°C, respectively) are proposed as candidates for Pb-free high-temperature solders. This paper reviews the features of Bi-base composite solders containing reinforcement particles of a superelastic Cu–Al–Mn alloy in a Bi matrix to relax thermal stress and to prevent the propagation of cracks, and Zn–Al base solders, which have high stability and high reliability enough to be utilized in practical applications under severe thermal cycle tests between −40 and 230°C more than 2000 cycles.