CTE difference decrease of epoxy molding compound after molding and after PMC

Abstract

With the rapid development of the semiconductor filed, more and more advanced package types have turned up such as Quad Flat No-lead (QFN), Ball Grill Array (BGA), and so on to meet the requirement of the high O/I function. Followed on, warpage has emerged as a big challenge during cutting and surface mounting process. As packing material, Epoxy molding compound (EMC) often show different performance on warpage after molding and after post mold cure (PMC). Coefficient of thermal expansion (CTE) difference of epoxy molding compound and laminate is one of the key factors influencing warpage. Here an internal method to measure the warpage based on CTE of EMC after molding and after PMC using thermal mechanical analysis (TMA) equipment has been developed. Dynamic Mechanical Analyzer (DMA) and impact strength have also been introduced to indicating the toughness of EMC. Coupling agent, rubber A and rubber B, polymer elastomer C and silicon oil D, have been investigated in the EMC system. The result show that EMC without coupling agent exhibits minimum change of TMA plot after molding and after PMC, meanwhile its DMA data displayed lowest modulus at room temperature, molding temperature as well as reflow temperature in the testing system. At the same time, EMC with rubber A show the biggest mold shringkage change after molding and after PMC. EMC with polymer elastomer C and EMC with silicon oil D show highest impact strength.