Effect of die attach configuration in stacked die packages

To accommodate the ever-increasing pressure of reduction in size, weight and cost, while provide more functionality and better reliability, many innovative electronic packaging solutions have been developed. Among them, stacked die packages offer smallest foot-print and thinnest profile in a cost-effective way and have been widely implemented in ASIC, memory, Ethernet controller, and other packages. However, new challenges keep emerging as more dies are stacked up and die thickness decreases to 50 to 75 μm level. In this paper, the improvement in die attaches to better suit stacked die configuration was discussed, including replacement of dummy die (spacer die) with spacer die attach pastes, adjustment of die attach properties and geometry to minimize molding compound/die attach delamination at die overhang area, comparison of film and paste die attaches. The detailed comparison in warpage and stresses was supported by finite element analysis.