Thermal and mechanical performance for different package design of ultra thin 8 die stacked flash packages

Based on the relationship between die size and package size, there were 3 possible package structures of 8 dies stacked memory flash as shown in figure 1, structure A1, A2 and A3 were shown in figure 1(a),1(b) and 1(c) respectively. All dies using in the 3 structures were numbered to U1~U8 from package bottom to top. Different package structures would induce different assembly process flows, which affected assembly process complexity and final cost. This paper explored thermal and mechanical performance of the 3 structures with finite element modeling (FEM). And the final finished packages with different stacked structures were also evaluated and compared. The warpage of different package structures were also studied and its possible impact to SMT process was also considered.