Dicing Die Attach Challenges at Multi Die Stack Packages

摘要

3D packaging provides a high level of functional integration in well established package families including BGAs and leadframe packages, by stacking die and using a mix of assembly technologies including wire bonding, flip chip, surface mounted components and passive cooling. Besides that, the package miniaturization has created challenges to a stacked die packages. With wafers thinned down to lOOum, conventional die attach process using solder paste or epoxy may not be suitable in this case due to bleed out of paste and bond line thickness (BLT) consistency. Dicing Die Attach Film (DDAF) as alternative has been widely used with its good control of bleed, consistent bond line thickness and simplified operation. The wafer which is mounted with DDAF will be diced into the predetermined die size and the diced chip will be picked and placed directly to a substrate with adhesive at the back. This paper will discuss the major concerns that contribute by the DDAF which is the void at the interface between the DDAF, die and substrate for a BGA stacked die packages. The characteristics of DDAF void and its formation/reduction mechanism are also investigated. Simultaneously the factors such as substrate surface condition, die attach parameter and molding parameter had been evaluated to improve the overall DDAF void performance.