Comprehensive study on die shift and die protrusion issues during molding process of Mold-1st FOWLP

Abstract

The introduction of Fan-Out Wafer-Level Packaging (FOWLP) is one of the viable approaches as the current packaging technology is moving towards low cost, multi-functions and small form factor packages [1]. FOWLP also offers good interconnects due to its shorter inter-connections from the chips to the thin-coated layer of metallization [2]. However, warpage largely induced from molding compound becomes a challenge in the fabrication of the FOWLP [3]. Silicon die bonded onto the carrier and the die shifted from its original bonded position during encapsulation known as die shifting. Factors affecting the die shift can be from material expansion rate, dragging force during encapsulation and the mold compound shrinkage properties [4].In this paper, we evaluated 3 different configurations of FOWLP Mold-1st packages to study the impact of the configuration and process parameters on die shifting, and die protrusion during the assembly process. DOE incorporating different bonding force is done to study their impact and to achieve a die shift, and die protrusion target of $\pm 15 \mu \mathrm {m}$.In summary, we are able to achieve a small die shift, minimum die protrusion and minimum warpage on the molded wafer for this FOWLP fabrication study.