Reliability assessment of high-leadcount TAB package

The authors describe the reliability assessment of a high lead count TAB (tape automated bonding) package using advanced packaging technology. The package was developed to replace existing leaded chip carriers for high I/O and high performance applications. The package technology uses Au bumps and Au plated, single-metal, two-layer 70-mm Cu tape with a polyimide support ring. Two test vehicles, with up to 332 leads, were assembled using the new packaging technology. Due to their physical constructions, the packages contained the characteristics of both hermetic ceramic packages and nonhermetic packages. To assess the reliability concerns arising from this technology, the packages were subjected to a comprehensive array of reliability tests consisting of military/industry standard thermal, mechanical, and environmental test methods. To address the module assembly process compatibility and its effects on reliability, some samples were attached to printed wiring board test coupons before being subjected to biased temperature humidity and pressure cooker tests. After stress testing, the samples passed all electrical testing. Furthermore, the corrosion resistance of the package was demonstrated. However, certain unexpected observations were also revealed, including lid cracking, low innerlead bond pulls, and dendritic growth