Application of Copper-Graphite Composite in Active Radar System Thermal Management

Discontinuous pitch-based graphite fiber reinforced copper (Cu/Gr) composites have been under development for semiconductor thermal management. The composites consist of a high thermal conductivity copper-chromium alloy matrix and short pitch-based graphite fibers randomly oriented in planar directions. These composites are a planar isotropic material. The CTE of this composite in planar directions is in the range of 2~9x10-6 /°C, varying with the fiber content, to match those of various semiconductor and packaging materials, such as SiC, silicon, GaAs, and GaN, alumina, and AlN. CTE in the through-plane direction is slightly less than that of the matrix alloy. The composites have a thermal conductivity in the through-plane direction from 200 to 320 W/m K and a thermal conductivity in planar directions from 330 to 420 W/m K, also varying with the fiber content. This composite is excellent in terms of machining and brazing, which renders itself as an ideal, low cost thermal management material for high power density packaging of advanced semiconductor devices. In this proposal, a liquid-cooled baseplate of this composite is proposed on which semiconductor modules can be directly built. The ability of this composite to be machined and brazed enables the proposed liquid-cooled baseplate to be cost effective.