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Characterization of Dual Side Molding SiP Module

The molded underfill (MUF) process for system in package (SiP) assembly has been applied for years and is still in production. However, the shrinkage in package size, cost reduction and improving electrical performance are driving the development of dual side molding package. The development of dual side molding technology faces the challenge of moldability. The moldability is largely influenced by the increasing number of component, decreasing bump/solder pitch, and shrinkage of package area. In this work, a three-dimensional finite element model was constructed and experimentally benchmarked to simulate the void formation behavior and the allocation of voids in the package. The molding analysis result shows that the void issue occurred between thin and multi-die stack packaging that would influence the manufacturability and reliability of the package. In order to reduce the void size and the number of void, a design monitoring the ratio between compound/mold volume and mold chase layout were investigated. The results of simulation indicate that the melt front is unbalanced. The incomplete filling occurs as the ratio of compound/mold volume is over 23%. The design of implementing an over flow zone in the end of the mold chase side edge and the decrease in the space between mold chase side edge and package edge can reduce the incomplete fill. The design increases the yield rate from 92% to 99%. The results of numerical analysis indicate that the above mentioned advanced SiP package structure design would lead to lower warpage and better thermal dissipation. The enhancements in the warpage behaviors are ascribed to the dual side balance structure and the appropriate hot spot location layout. The dual side molding SiP mechanism and the design guidance for engineering application will be presented and discussed in this paper.