Ultra-thin mold cap for Advanced Packaging Technology

In this paper we carry out studies to compare the effect of mold material selection between granular and liquid materials to develop a novel ultra-thin mold cap solution. Previous studies in this area have shown ability to produce thin mold caps down to around 100 μm with bumps and bare substrates [1]. In this study, using a new compression molding technique, we manage to produce ultra-thin mold caps down to 30 μm. We are also able to show the benefits of granular mold compound for this process to enable cheaper, easier to handle material with less warpage introduction to the product. Using the right filler size for the mold material, we are also able to ensure the proper encapsulation of fine pitch structures. The combination of this enables us to provide an ultra-thin mold cap solution with low thickness variation for wafers with both electroplated and ball dropped solder bumps. In addition, as the solder bump pitch goes down further with subsequent technologies, it is important to effectively protect the front side of the bumped wafers. Due to the good warpage, thickness control and minimal solder shift, with further process optimization, this can be serve as a path to develop thin mold cap solution in embedded wafer level ball grid array (eWLB) with fine pitch structures [2].