Study on the Coverage of Metal Thermal Interface Material for Ultra-Large FCBGA Packaging

In this study, the coverage of metal Thermal Interface Material(TIM) and warpage for ultra-large Flip Chip Ball Grid Array(FCBGA) package were investigated by experiments and finite element analysis. Shadow moire, Cscan were used to characterize the warpage and metal TIM coverage , respectively. The study found that the coverage of metal TIM within large-scale FCBGA chip has a significant correlation with the warpage of package, especially in the reflow temperature above 150 degrees. The large deformation at the temperature above 150 degrees promotes the generation of large voids in the metal TIM, and this large deformation will promote the deterioration of indium coverage in the reflow process. Once the core thickness of substrate was increased, the package warpage shall be mitigated in the high temperature enviroment. The behavior of warpage was consistent with the theoretical calculation and simulation results. Based on the corelation , we had been demostrated the opimized metal TIM coverage in multiple products.