Comparison of sintered silver die attach failure between thermal shock test and mechanical cycling test

Abstract

Abstract This paper compares the degradation of sintered silver (s-Ag) die attach between a thermal shock test (TST) and a mechanical cycling test to correctly understand the mechanism of s-Ag die attach failure in power module products during practical operation. A bar-shaped specimen is subjected to two types of four-point bending tests: a centered bending test for bending moment application and a shifted bending test (SBT) for shear force application. The crack path in the SBT is similar to that in the TST, which suggests that shear force has an important role in imitating the degradation and failure of s-Ag in the TST. The crack propagation speed per cycle in the TST is, however, about 4000 times faster than that in the SBT. The lifetime assessment period of the SBT is approximately 1400 times shorter than that of the TST. The difference in failure mechanism between the TST and SBT is discussed by using scanning electron microscopy of the fractured specimens.