An investigation of thermal enhancement on flip chip plastic BGA packages using CFD tool

This paper demonstrates the advantage of applying Predictive Engineering in thermal assessment of a 279 inputs/outputs (I/Os), six-layer, depopulated array flip chip PBGA package. Thermal simulation was conducted using a comp utational fluid dynamics (CFD) tool to analyze the heat transfer and fluid flow in a free convection environment. This study first describes the model ing techniques on multilayer substrate, thermal vias, solder bumps, and pri nted circuit board (PCB), For a flip chip package without any thermal enhan cement, more than 90% of the total power was conducted from the front surfa ce of the die through the solder ball interconnects to the substrate, then to the board. To enhance the thermal performance of the package, the heat t ransfer area from the backside of the die needs to increase dramatically. S everal thermal enhancing techniques were examined, These methods included c opper heat spreader with various thicknesses and with thermal pads, metalli c lid, overmolded with and without heat spreader, and with heat sink, An al uminum lid and a heat sink gave the best improvement; followed by a heat sp reader with thermal pads. Both methods reduced thermal resistance by an ave rage of 50%, Detailed analyses on heat flow projections are discussed.