Graphite nanoplatelet pastes vs. carbon black pastes as thermal interface materials

Comparison of graphite nanoplatelet (GNP) and carbon black (CB) pastes as thermal interface materials shows that the optimum filler content for attaining the maximum thermal contact conductance (copper proximate surfaces, roughness 15 μm) are 2.4, 15 and 2.4 vol.% for GNP, CB (Tokai) and CB (Cabot), respectively. Except for CB (Cabot), the optimum filler content is diminished when the roughness is decreased from 15 to 0.009 μm. Comparing the fillers at their respective optimum contents shows that (i) GNP is similarly effective as CB (Tokai) for rough (15 μm) surfaces, but is less effective than CB (Tokai) for smooth (0.009 μm) surfaces, and (ii) GNP is more effective than CB (Cabot) for rough surfaces, but is slightly less effective than CB (Cabot) for smooth surfaces. GNP gives higher thermal conductivity and greater bond line thickness than CB (Tokai or Cabot), whether the comparison is at the same filler content or at the respective optimum filler contents. In spite of the high thermal conductivity, the effectiveness of GNP is limited, due to the high bond line thickness. CB (Tokai) gives higher thermal conductivity than CB (Cabot), thus causing CB (Tokai) to be more effective than CB (Cabot).