Investigation on TSOP warpage mechanism and improvement method

Abstract

This paper gives a detailed investigation on TSOP warpage mechanism. The influences of all the factors on warpage behavior, including materials (EMC ingredient and lead frame), lead frame design and assembly process, were investigated through numerical simulation and experimental study. The simulation result showed that low CTE material is a good choice for warpage reduction. And it also indicated that by properly modifying the lead frame design, the warpage performance can be improved. Much attention was paid to the curing process as this thermal process would obviously affect the stress formation and release in the package. It was deduced that a reduction in the cooling rate above Tg during cure would reduce warpage based on theoretical thermal analysis, and the experiment result proved it did work. Finally a modification to the cure process is proposed as the most cost effective and practicable solution in actual production.