Thermal Fatigue Fracture Behavior of Sintered Ag Nanoparticles under Equibiaxial Thermal Stress

Abstract

An equibiaxial thermal fatigue test of die-attach materials that reproduces the same stress state as the power cycle was proposed, and the fatigue fracture behavior of Ag sintered die-attach materials under equibiaxial thermal stress was investigated. Thermal fatigue tests under equibiaxial stress showed that vertical cracks were observed throughout the sintered Ag nanoparticles. Thermal fatigue fracture was out-of-phase type, in which crack initiation and opening were driven by equibiaxial tensile stress during temperature drop. It is suggested that the fatigue crack growth in the die-attach joint during power cycling can be predicted by the fatigue crack growth law at high temperatures obtained by mechanical fatigue tests.