Popcorn testing of liquid encapsulants

Glob-top encapsulation has found wide-spread acceptance in electronics assembly for low-end, consumer products. To extend the use of this encapsulation method to high reliability and harsh environment conditions, a rigorous evaluation of the available materials is needed. This paper outlines the results of popcorn tests on a wide range of liquid encapsulant materials. The materials were chosen on the basis of being market leaders in providing reliable protection for direct attached ICs and are used in several applications such as glob-top for COB through to IC protection in BGA and multi-chip style packaging. Evaluations based on variables such as encapsulant type, substrate material and wire-bond material were performed to compare these encapsulants. Electrical characterization and non-destructive scanning acoustic microscopy were the main analysis techniques used on the samples.