Determination of the filler distribution in an epoxy molding compound using high-resolution X-ray computed tomography

In this paper, the filler distribution in an epoxy molding compound (EMC), used in IC packaging, is studied across a wafer using high-resolution X-ray computed tomography (HR-XCT). It is widely assumed that the fillers are uniformly distributed across the wafer. However, it is demonstrated that the distribution of the filler deviates across the wafer, and that filler sizes affect the distribution on edge and center of wafer too. Quantitative HR-XCT of the filler distribution provides accurate data for simulation. Based on this approach, the differences between CTE and Young's modulus values of the filler material for the center and edge of the wafer is explained. Furthermore, compression simulations are conducted applying an XCT-based FEM model to understand the role of EMC for the mechanical behavior of advanced IC packages. These findings are validated by in-situ and stand-alone compression experiments. The accurate simulation results demonstrate that the use of an XCT-based FEM model provides insight into the mechanical behavior of the EMC itself, and furthermore, of the whole IC package.