Strip grinding introduction for thin PoP

摘要

Due to rapid growth in the mobile industry, Package-on-Package (PoP) has been widely adopted for 3D integration of logic and memory devices within mobile handsets, and other portable multimedia products, etc. Typical PoP configuration includes a logic function in the bottom package while memory dice are assembled into the top package. The TMV solution is widely adopted to reduce package warpage, to achieve a fine pitch PoP, and to stabilize stacking performance. Another big benefit of the TMV is to generate a thin structure by exposing the back side of the die using a film assist mold system. However, the trend of mobile devices is going thinner and thinner, and there is a limitation to achieve the thin PoP structure. The most difficult barrier to generate the thin PoP structure is the warpage control. In this paper, a strip grinding process is introduced as a solution to generate thinner PoP structures in overmolded packages. Applying the strip grinding process to exposed die, reducing mold clearance, and exploring double sided mold structures to reduce die/package height were also investigated.