EFFECT OF GEOMETRIC PARAMETERS ON POPCORN CRACKING IN PLASTIC PACKAGES DURING VPS PROCESS

Several thin quad hat packages (TQFPs) are analyzed for the evaluation of G, the energy release rate based on the interfacial fracture mecha nics. The purposes of this study are; (i) to obtain the values of G as a function of the length of delamination (interfacial crack) and vari ous geometric dimensions, (ii) to obtain the values of G for the packa ge crack, which is believed to be the subsequent stage to the full del amination, and consequently (iii) to investigate quantitatively the ef fect of the various geometric dimensions on the popcorn cracking durin g vapor-phase soldering (VPS). Also the method to compute the phase an gle (or mode mixity) for the interfacial crack is presented for severa l TQFPs. Due to the insufficient data for G(int)(c), the question of w hether the partial delamination for given alpha (delamination length o r crack length) grows or not cannot be addressed. However, this can be used for the prediction of the popcorn cracking in the future study. (C) 1998 Elsevier Science B.V. All rights reserved.