Innovative stack-die package - S2BGA

Stack-die package concept has been emerging 2similar to3 years ago. The major product - stack-die package with Flash and SRAM chips integrated together which is driven by cellular phone for the purpose of size and weight reduction. The basic requirement for these two dies in stacked package is the size difference must be large enough to allow wire bonding process at bottom die if we still want to utilize the low cost, mature wire bonding technology in interconnection. However, this requirement will limit the application in trying to integrate two similar or same size dies into one stack-die package. One solution for this application is to utilize flip chip technology in interconnection to solve the die size difference requirement. One of concerns for this package is the higher assembly cost due to Flip Chip interconnection. Therefore, a low cost, high reliability alternative package structure is created, it is named S2BGA as Fig. 1.(Spacer Stacked Ball Grid Array).