Pre-structural patterning approach for enhancing flow characteristics of B-stage film-type epoxy molding compound

Abstract

Epoxy molding compound (EMC) compositions of silica powder and epoxy matrix have been utilized as encapsulation for semiconductor packaging over the past decades. Among various forms of EMC, film-type EMC offers untapped potential. Utilizing EMC film as an encapsulation material allows larger and more uniform encapsulation behavior especially for panel-level and wafer-level packaging applications. In material aspects, as increases silica contents in EMC film, it can encounter a trade-off relationship between the coefficient of thermal expansion (CTE) and the material's viscosity. As silica content increases, the CTE tends to decrease, which enhances warpage behavior. However, viscosity also tends to increase, which reduces flowability. To overcome these tradeoff relationships, in our study, we have demonstrated a pre-structural patterning approach to enhance flowability of B-stage EMC film without changing the raw compositions of material. By doing that, we can suppose increased flowability of film while having similar thermomechanical properties. For patterning while maintaining B-stage, patterned protection film was fabricated using a brass-based metallic mold and a PDMS/PUA-based soft mold. Subsequently, pre-structural patterned EMC was fabricated by transferring the patterned protection film onto a B-stage EMC film using a laminator. The effectiveness of patterning on EMC film was investigated in both numerical and experimental molding analysis according to rheological, chemical, and thermomechanical characterization. The pre-structural patterning approach demonstrated enhanced flow characteristics via a shortened flow path despite the increased viscosity caused by higher silica content.