Carbon black dispersions as thermal pastes that surpass solder in providing high thermal contact conductance

Carbon black dispersions based on polyethylene glycol (PEG) or di(ethylene glycol) butyl ether, along with dissolved ethyl cellulose, provide thermal pastes that are superior to solder as thermal interface materials. The thermal contact conductance of the interface between copper disks reaches 3×10⁵ W/m² °C, compared to 2×10 ⁵ W/m² °C for a tin-lead-antimony solder. The pastes based on PEG are superior to those based on butyl ether in their thermal stability above 100°C. Carbon black is superior to materials that are more conductive thermally (graphite, diamond and nickel particles, and carbon filaments) in providing thermal pastes of high performance. The performance of thermal pastes and solder as thermal interface materials is mainly governed by their conformability and spreadability rather than their thermal conductivity.