PREDICTING DELAMINATION IN PLASTIC IC PACKAGES AND DETERMINING SUITABLE MOLD COMPOUND PROPERTIES

This paper proposes that the critical stress intensity factor obtained in an adhesion test between the leadframe and the mold compound can b e used as a criterion for predicting delamination. A finite element st ress analysis of the adhesion test determines the critical stress inte nsity factor K(IIC) corresponding to the measured maximum strength. De lamination between the leadframe chip pad and the mold compound occurs when the maximum stress intensity value, K(II) for the package exceed s the critical value K(IIC). The validity of the proposed criterion wa s verified by experiments on different plastic SO.J packages molded wi th different molding compounds under different moisture conditions. Th ese findings suggest that for any new IC package, an optimised package design together with a mold compound withthe necessary properties tha t will not result in delamination can be defined on the outset of any new package development. The results of this work can be used to avoid exhaustive experimental trials, enabling savings in both time and cos t in new package development. They can also be used to set directions for mold compound manufacturers on the requirements of compounds for f uture generation IC devices.