Criterion for predicting delamination in plastic IC packages

Abstract

This paper proposes that the critical stress intensity factor in linear elastic fracture mechanics. KIIC, obtained in an adhesion test between the leadframe and the mold compound can be used as a criterion for predicting delamination. A finite element stress analysis of the adhesion test determines the critical stress intensity factor KIIC corresponding to the measured maximum strength. Delamination between the leadframe chip pad and the mold compound occurs when the maximum stress intensity value. KII obtained for the package exceeds the critical value KIIC in the adhesion test. The validity of the proposed criterion was verified by experiments on different plastic SOJ packages molded with different grades of molding compound under different moisture conditions. These findings suggest that for any new IC package, an optimised package design together with a mold compound with the necessary properties that 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 cost in new package development. They can also be used to set directions for mold compound manufacturers on the requirements of compounds for future generation IC devices.