BEHAVIOR OF DELAMINATED PLASTIC IC PACKAGES SUBJECTED TO ENCAPSULATION COOLING, MOISTURE ABSORPTION, AND WAVE SOLDERING

Plastic IC packaging subjected to moisture is vulnerable to delaminati on and cracking during the solder reflow process, Modeling the respons e of the delaminated plastic package is an essential step to fundament ally understand failure mechanisms and mechanics involved in the cooli ng, moisture absorption, and solder reflow process, A nonlinear finite element model was developed for predicting the deformation, stress, a nd fracture behavior of delaminated plastic packages induced by mechan ical and hygro-thermal loads, The model consists of a sequentially cou pled hygro-thermo-mechanical analysis considering moisture absorption, evaporation and interface contact and fracture analysis. A Lagrange M ultiplier method was utilized to model the delamination interface cond ition. A general contact model was adopted which can handle complex co ntact conditions, such as arbitrary slippage and discontinuous curvatu re, A thermal contact mas utilized to model the contact along delamina tion surfaces. Mixed mode fracture modes mere elaborated, The model wa s verified by comparing existing analytical results with the predictio ns in the case of pulsed heating of the IC chip, Packaging responses a nd failure mechanisms due to encapsulation cooling, moisture absorptio n and evaporation, wave soldering, and interfacial moisture pressure l oading are investigated, with consideration of temperature-dependent m aterial properties change around the glass transition temperature for both die attach and molding compound, Packaging deformation and stress , crack tip driving force, doming of the delamination, and delaminatio n growth stability as a function of time are discussed.