Comparative evaluation of thermal interface materials for improving the thermal contact between an operating computer microprocessor and its heat sink

Testing of the relative effectiveness of various thermal interface materials for improving the thermal contact between the well-aligned mating surfaces of an operating computer microprocessor (with an integrated heat spreader) and its heat sink shows that carbon black paste, whether by itself or as a coating on aluminum or flexible graphite, is more effective than silver paste (Arctic Silver), but is comparable in effectiveness to aluminum paste (Shin-Etsu). The carbon black paste by itself is as effective as the Shin-Etsu paste coated aluminum. The Shin-Etsu paste is more effective than Arctic Silver, whether by itself or as a coating. The relative performance is mostly consistent with that assessed by measuring the thermal contact conductance. The correlation is particularly strong for conductance below 3×10⁴ W/m²·°C. The discrepancy is attributed to the difference in surface roughness between computer and guarded hot plate surfaces. In the case in which the mating surfaces of microprocessor and heat sink are not well aligned, Shin-Etsu and Arctic Silver are more effective than carbon black.