Effect of Loading Type on Fatigue Lifetime of Sintered-Silver Die Attach

The effect of loading type on the fatigue lifetime of sintered-silver die attach was investigated. The fatigue lifetime was measured by fatigue testing with micro-load testing equipment. The fatigue tests were conducted under displacement control with (reversed loading (stress ratio R = -1), pulsating-tensile loading (R = 0), and pulsating-compression loading (R = -infinity)) at room temperature. The strain of the fatigue test was estimated by strain-displacement relation obtained from previous tensile test using the strain gauge. Sintered-silver specimens were made from prebaked microscale silver paste and pressurized at 10 MPa for 10 minutes in air atmosphere at 573 K. The fatigue lifetime of reversed-loading case was 1000 cycles, that of pulsating-tensile-loading case was 4000 cycles, and the pulsating-compression-loading case remained unbroken. This suggests that compression load does not contribute to the destruction of the sintered silver. These measured fatigue lifetimes were aligned in a row when these are organized by maximum stress (tensile stress range). For fatigue lifetime evaluation of sintered silver, evaluation focusing on tensile stress seems to be important.