Characterization of mold compound to improve delamination performance in power package

Abstract

This paper elaborately discusses the process of selecting the most prominent mold compound candidate which balanced the quality, cost and moldability aspects. In this experiment sample X7 was selected based on the validation performed. The mold compound fluidity properties and critical molding parameters' window were analyzed by measuring Visual mechanical rejects, weight gain (%) and SAT on nickel plated lead tip as output response. In the experiment conducted, transfer time and spiral flow were identified as significant factors affecting weight gain and delamination on nickel plated post. In order to ensure all related stress to die is below the limit of 30ksi, Finite Element Modeling and simulation were performed to study die thermal stresses when it is loaded with temperature excursion during package assembly steps assuming the packaging raw materials has not been pre-stressed by its manufacturing process such as when the leadframe undergo stamping, die saw and etc. The analysis recommends the use of mold compound X7 for its superior performance at reflow condition. Before the mold compound could be released into production mode, mold runners were redesigned by modifying the draft angle at `weak point' and ejector pin were slotted-in on cull surface to allow uniformed ejection force. It reports the successful introduction of delamination improved mold compound which complies to MSL-1 260C package robustness.