2015 Volume 56 Issue 648 Pages 29-33
Chromium-copper materials have been developed to be substituted for W-Cu and Mo-Cu materials in heat-sink applications. These latter materials have poor formability and poor machinability, which raise processing costs. Tungsten and molybdenum powder are both rare metals, very expensive, and have unstable supply. Chromium is a 6A group element, the same as W and Mo, and the cost of its powder is lower and its supply is more stable, but its thermal properties are inferior to those of W and Mo. To realize thermal properties of Cr-Cu close to those of Mo-Cu and W-Cu, rolling is thought to be an effective improvement method. Rolling formability was tested by 50mass%Cr-Cu material. The material showed good rolling formability. However some microcracks, which are detrimental to Ni plating, were observed on the surface of the rolled sheet. These microcracks were shown mainly at the boundaries between Cr particles and the Cu matrix. Warm rolling was effective for reducing the number of cracks. FEM analysis revealed that large roll diameter could reduce the stress at the boundaries. It was confirmed that there is a correlation between the number of cracks on the plate and the amount of stress at the boundaries.
