New thin plastic package crack mechanism, induced by hot IC die

Abstract

Fine cracks in thin plastic packages have been observed after board tests and reliability tests with static or dynamic biasing. The new package crack mechanism was investigated and a model is proposed. Cracks in thin plastic packages can occur when the die overheats due to the latchup phenomenon in CMOS ICs. This crack mechanism is attributed to high pressure inside the package created by outgassing of plastic encapsulant material surrounding the overheated die and thermomechanical stresses. Hot-die-induced cracks are similar in appearance to moisture-induced popcorn cracks occurring during vapor-phase solder reflow. This may lead to ambiguity as to the actual cause of failure when such cracks are encountered. Non-destructive and destructive techniques are proposed to distinguish hot-die-induced cracks from popcorn cracks.<>