Thermal stress and fatigue analysis of plated-through holes using an internal state variable constitutive model

Abstract

Previous related research on plated-through hole (PTH) fatigue investigations has been based on the so-called effective stress/strain methods, which did not account for the fact that fatigue crack nucleation and growth is observed to occur on planes of specific orientation. Moreover, previous related thermal stress/strain analyses were at most based on bilinear constitutive relations for modeling copper plating along with a linear kinematic hardening assumption, and this cannot capture many aspects of cyclic stress/strain behavior during thermal excursions. In this paper, thermal stress analyses using internal state variable (ISV) models of metallic constituents of PTHs are conducted using the finite element code ABAQUS (1996). Two thermal history profiles having two repeated cycles were applied for the PTHs of a double layered printed wiring board (PWB) uniformly: (1) MIL-T-CYC (between −65°C and 125°C), and (2) IEC OIL-T-SHOCK (between 25°C and 260°C). A critical plane theory was used for purposes of multiaxial fatigue life prediction. The stress/strain results were reported and compared at the PTH corner and barrel. For both cases, the thermomechanical mismatch between the FR4 and copper constituents of the PWB generates nonproportional stress/strain responses. This complicates PTH thermal fatigue investigation.