Effect of surface roughness of silicon die and copper heat spreader on thermal performance of HFCBGA

From the available mass production devices of HFCBGAs, there can be a range of surface roughness with different surface finished of silicon dies and heat spreader. An aluminum filled gel is used to examine the surfaces clamping with both identical substrates at both sides whether compatible to the thermal conduction. Their thermal contact resistances are measured by laser flash technology and therefore modeling HFCBGAs with those measured roughnesses and resistances for characterizing thermal performances.