A New Reliable Adhesion Enhancement Process for Directly Plating on Molding Compounds for Package Level EMI Shielding

摘要

Plating on molding compound is a relatively new field whichcould open up new package designs. One major application is conformal self EMI shielding (package level shielding) of ICs. Generally, EMI shielding is done mainly by metallic cans, however, this technique increases the space requirements and reduces flexibility of component layout on the PCB, that would not be suitable to handset products. An alternative and more space saving approach is 'Conformal Self EMI Shielding (package level shielding)'. A popular method to provide a metallic seed layer for'Conformal Self EMI Shielding' is sputtering and conductive paste, however, in order to make it more cost effective and feasible for mass production, there is a need for classical electroless plating metallization along with adhesion enhancement process. While in some instances conductive paste and sputtering metallization will provide adequate adhesion -- it has the technical drawbacks of poorsidewall coverage and limited metal layer thickness that would not fulfill for lower frequency noise shield. As a result, scale-up for mass production is relatively difficult and costly. Classical electroless and electrolytic plating metallization are much more desirable but have been so far limited by insufficient adhesion by existing chemical treatment, due to the presence of extremely high ratio (80-90%wt.) and irregular size (from few μm to tens of μm) offillers. In this paper we will present a new 'Adhesion nhancementProcess' approach that is based on an innovative combination of mechanical anchoring by selective resin etching and chemical adhesion promoter along with adhesion results and shielding effectiveness results. This adhesion enhancement technology is applicable to various kinds of molding compounds. Extending this technology to new package design (Embedded PoP/SiP) can be other reaching applications.