The Improvement Guidelines of BGA Warpage within SMT Temperature Profile Using Shadow Moiré Technique

Abstract

The electronic package warpage is induced by the mismatch of coefficient of thermal expansion (CTE) between different materials that compose the package after specific temperature change process. To well control package warpage after assembly process is an important assignment for packaging engineer because those packages with excessive warpage will be rejected by customers due to board SMT process yield/quality concerns. The primary failure mechanism coming from excessive package warpage during SMT assembly process is ball shorting or opening to cause electrical connectivity failure, thus, package designers are being driven to improve package warpage during SMT temperature variation to ensure a robust board assembly performance at the earlier stage of package design development. From this study, we have studied for improvement of warpage performance of BGA. The PBGA with the low CTE mold compound can reduce the CTE mismatch effects on substrate, but there is no obvious evidence to show the thickness of mold compound and substrate effect on warpage. In addition, PKG with heat spreader design can get better warpage performance. EDHS-PBGA has smaller package warpage variation, compared with the PBGA due to drop-in mold compound heat spreader, so the EDHS-PBGA deformation depended on heat spreader and was controlled by heat spreader to achieve the improvable warpage at room and peak temperature.