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|Side Mount Package (SMP) for Ultra-High Density Memory Applications|
|Keywords: package stacking, 3D, solid state drive|
|In recent years, package stacking technology has been practiced widely in industry, mainly as perimeter array package on package (PoP) stacking configuration. However, the stacking qty is limited to just two. For ultra high density die stacking application such as solid state drive (SSD), there can be as many as 64 dice assembled in limited space. For this type of application, multi-package stacking can provide practical lower cost solution compared to die level memory stacking by Through Silicon Via (TSV) technology. However, multi-package stacking technology has not yet been demonstrated in High Volume Manufacturing. Therefore, new low cost and highly reliable multi-package stacking concept is necessary for ultra high memory density packaging solution. In this paper, we developed side mount package (SMP) cube, which is shown to use smaller board space than any of other package stacking technology. Small board space for eight or more multi-stack packages is due mainly because SMP doesn’t need redistribution layer formation process for side wall interconnection or through mold via (TMV) formation and solder filling process, and solder joints between individual packages. Key processes are; (a) QFN single package build by typical die stacking technology with wire bonding and die attach film. Key feature here is the exposed lead pad on side wall of the QFN package. (b) QFN package stack by polymeric adhesive layer with thickness of 20~50 um, (c) the eight QFN package stack up by adhesive layer and the exposed pad is aligned on one area of the package stack up. This array of the exposed pad from each QFN pad is naturally redistributed pad to the sidewall. (d) Final step is solder balls attach on the exposed pad array for board level interconnection. This work demonstrated ultra-high density package stacking solution by SMP’s novel package stacking and easy manufacturability.|
|Myung Jin Yim, Sr. Packaging Engineer