Thermal resistance analysis and validation of flip chip PBGA packages

Abstract

This work proposes a finite element numerical methodology to predict the thermal resistance of both flip chip-plastic ball grid array (FC-PBGA) with a bare die and FC-PBGA with a metal cap. The 3D finite element model was initially constructed to simulate the thermal resistance of FC-PBGA. A thermal resistance experiment was performed to verify the FEM results, following the construction of specimens of FC-PBGA with a bare die and with an aluminum cap, using six-layered substrate. The verified finite element model was employed to determine the thermal resistance of FC-PBGA with a copper cap using four-layered and six-layered substrates. Experimental results demonstrated that FC-PBGA with a metal cap improves thermal performance by 35% over with a bare die. FC-PBGA with a copper cap slightly improves thermal performance from 2% to 2.8% over that of FC-PBGA with an aluminum cap. The thermal resistance of FC-PBGA with a four-layered substrate is reduced by 4.0% to 5.9% from that of FC-PBGA with a six-layered substrate, since the four-layered substrate contains less metal. The finite element numerical results negligibly differ from the experimental results by 6% to 8.1%. A finite element numerical methodology is here proposed to predict the thermal resistance of FC-PBGA. The methodology is effective in researching and developing new products or improving existing packages.