Adhesive Enhancement Technology for Directly Metal Plating on EMC

Abstract

Plating on molding compound is a relatively new field with many possible applications. One major application is magnetic or electrical EMI shielding of active components. This is currently done by metallic cans. However, this technique also increases the space requirements. A second major application, is the formation of build-up circuits on encased components, such as for Fan-out Wafer Level Packaging (FO WLP). An established method to provide a metallic seed layer is sputtering. However, with respect to cost effectiveness and mass production capability, classical electroless metallization along with an adhesion promoters would a desirable alternative. In this paper we will present a new approach, where components encased by molding compound are directly coated with an electroless copper or nickel layer. By this method spatial requirements are minimized. Also, this process fits into the existing infrastructure within the PCB industry. Due to the presence of fillers with an extremely high ratio (70–90%wt.) and irregular size (from few μm to tens of μm), classical Desmear followed by electroless seeding can get at best an adhesion of only 2–3N/cm . This is typically insuffient to prevent delamination during further processing. In contrast, with chemically bonding adhesion promoters, as presented in this paper, we are able to get up to 5N/cm of peel strength without any blistering. The plated layer stands up well to reflow shock (260C) and HAST without significant loss of adhesion. These adhesion enhancement technology is applicable to various kinds of molding compound. Extending this technology to FO WLP (i.e. FO SiP, FO PoP) can be another far reaching application.