The Influence Analysis of Geometry on Void in Molded Underfill for Flip Chip

In flip chip packaging, the molded underfill (MUF) integrates the underfilling and molding processes to reduce manufacturing cost and cycle time of process, but is difficlut to obtain high quality filling due to void trapping problem. Virtually, from a technical perspective, it is a microinjection molding process, the MUF process can be thought as a pressure-driven suspension flow. For transfer molding, the main factors affecting the reliability of products include the properties of filling materials, injection process parameters and the geometry of the cavity. In this paper, 3D mold flow modeling of the transfer molding process with MUF using Moldflow is applied. By designing DOE experiments, the MUF process parameters were optimized under different packaging structures of flip chip, and the influence of different methods of chip placement on the molding results was discussed, providing a basis for the design and optimization of process parameters and chip geometry structure.