Effectiveness of conformal coatings on a PBGA subjected to unbiased high humidity, high temperature tests

Abstract

Plastic ball grid array (PBGA) packages are non‐hermetic surface mount packages, designed in response to market demands for cost‐effective, high I/O count, small footprint, and low profile components. Because of the materials and construction, PBGA packages can be vulnerable to failure mechanisms associated with exposure to temperature and humidity. In some applications, conformal coating has been used as a potential means to mitigate these problems by enhancing moisture ingress resistance. This study focused on the ability of two popular kinds of conformal coatings to protect PBGA packages from moisture‐induced failures. As part of the study, PBGA packages with and without conformal coatings were subjected to moisture ingress, moisture desorption and unbiased high temperature high humidity tests. The principal failure mechanisms observed were delamination and cracking in the packages. Although it was observed that parylene coating did slow down the moisture ingress, the high temperature high humidity tests did not demonstrate that two tested conformal coatings had significant protection against moisture‐induced failures for PBGA packages.