Nanoclay Paste as a Thermal Interface Material for Smooth Surfaces

A paste in the form of a polyol ester vehicle (liquid) containing 0.6 vol.% nanoclay is an effective thermal interface material. Nanoclay with a high conformability and hence a small bond line thickness is preferred, namely montmorillonite containing a quarternary ammonium salt organic modifier (dimethyl dehydrogenated tallow) at 125 meq/100 g clay, after exfoliation by using the vehicle. When it is used between smooth (0.009 μm) copper surfaces at a pressure of 0.69 MPa, the thermal contact conductance reaches 40 × 10⁴ W/m² K, in contrast to the corresponding values of 28 × 10⁴ W/m² K, 28 × 10⁴ W/m² K, 25 × 10⁴ W/m² K, and 24 × 10⁴ W/m² K previously reported for carbon black, fumed alumina, fumed zinc oxide, and graphite nanoplatelet pastes. Between rough copper surfaces (12 μm), the conductance provided by the nanoclay paste is slightly below those of the other pastes. The superiority of the nanoclay paste for smooth surfaces is attributed to the␣submicron bond line thickness; the inferiority for rough surfaces is due to the low thermal conductivity. The conductance provided by the nanoclay paste increases from 31 × 10⁴ W/m² K to 40 × 10⁴ W/m² K when the pressure is increased from 0.46 MPa to 0.92 MPa. This pressure dependence is stronger than that of any of the other pastes studied.