Stitch-bond reliability evaluation by construction analysis

Abstract

Electronic components have changed the way we live and the way we use technology since they were first introduced into products. Most equipment is only as reliable as its internal electronic components. In electronic integrated circuit (IC) components, wire bonding is the most common first-level interconnection method between die and lead. Failure of wire bonds can have very costly consequences in the severe or harsh operating conditions of the oil and gas industry, where services such as rig charge are extremely expensive.Wire bonding has several failure modes and mechanisms. The most common failure modes are ball bond failure due to intermetallic growth and stress, wire rupture due to electrical overstress, and stitch-bond related failures due to repeated flexure of the wire induced by thermomechanical loading. The ball and stitch-bond failures are accelerated in harsh environment applications.This study focuses on gold (Au) and copper (Cu) stitch-bond failures caused by mechanical vibration coupled with thermal cycling of gull-wing plastic components. Both design and operating parameters impact stitch-bond reliability. In this study, simulation was used first to identify the potential effect of design parameters (component level and assembly level) on the stress magnitude and to rank the most critical structural parameters impacting stitch-bond reliability. Test units were designed based on the simulations and subjected to the test conditions that provided feedback to the model to define acceptance criteria using experimental results. Destructive construction analysis confirmed the location of stitch-bond failures and variables contributing to early failure or extended life of stitch bonds. This paper describes the component robustness prediction method that can be used as a lot acceptance test to screen plastic encapsulated IC components using construction analysis.