Effect of surface flatness on interface heat transfer

Data and conclusions are presented on the effect of surface flatness on heat transfer across an interface between two plates. The effect of thermal grease (Dow Corning 340 silicone heat sink compound) on interface heat transfer is also presented. Test data yields three conclusions: interface heat transfer varies linearly over the tested range of surface flatness (0.010 to 0.035 in); thermal grease decreases interface thermal resistance by a minimum factor of 2.5; and as interface temperature increases, thermal resistance decreases. The objective of the thermal tests was to measure the rate of heat transfer across an aluminum-to-aluminum interface. The subject interface is located between two electronics assemblies