On the mode II popcorn effect in thin packages

Abstract

Experiments were carried out using P-TQFP-176 packages to study the mode II popcorn effect in thin packages. The doming of the package backside was measured as a function of time and temperature. The measurements were performed using a line projection method. An "accelerated" increase in the doming was found to correlate with the onset of the package crack propagation. It was shown that when a constant critical doming angle is reached, package cracks begin to propagate toward the surface. This critical doming angle was found to be temperature independent between 170°C and 215°C. Furthermore the development of the package doming with time was described by a simple model based on the moisture diffusion from molding compound and die-attach material in combination with a bimaterial plate theory. The water content of the die-attach layer after preconditioning was calculated from the model and it was found to be in good agreement with the results of a three dimensional finite element simulation

Vapor pressure and residual stress effects on failure of an adhesive film

“…Experimental studies on type II package cracking have shown that plastic packages could fail by interface delamination and/or rupture of the die-attach layer (e.g. Alpern et al, 2002;Tay and Lin, 1999;Pang and Seetoh, 1997;Pang et al, 2002). The numerically simulated behaviors are consistent with these experimentally observed failure mechanisms.…”

Plastic Ball Grid Array Encapsulation Process Simulation on Rheology Effect

“…Several models have been used to predict the relationship between viscosity (µ) and the degree of polymerization. The Castro-Macosko model has been applied by Nguyen et al [8] and Alpem et al [9] is selected to use in this simulation. It is described as follows:…”

Coupled Thermal-Moisture-Stress Analysis for Electronic Packages

“…The temperatures from this analysis can be mapped onto a stress analysis to give the moisture-stress, using the coefficient of moisture expansion is given in place of the coefficient of thermal expansion. This method has been used frequently and is widely documented [3][4]. The limitation of this approach is that it ignores any effect of temperature gradient or pressure on the moistures distribution.…”