PURPOSE: To provide a clad material for widening the use as a high thermal conductivity clad material by combining a high thermal conductivity metallic material, e.g. copper or copper alloy, with a low thermal expansion alloy metal which can sustain the thermal expansion characteristics of superinvar alloy at 150°C or below up to about 300°C.

CONSTITUTION: An Fe-Ni-Co alloy containing 31.5-33.5wt.% of Ni, 7-8wt.% of Co, and 40.5wt.% or less of (Ni+Co) can sustain the thermal expansion characteristics at 150°C or below up to about 300°C. When a high thermal conductivity metallic material, e.g. copper, is clad with such alloy the ratio of copper can be increased up to 30-70%. Consequently, a novel clad material having average coefficient of thermal expansion in the longitudinal direction lower than 8×10-6K-1 in the temperature ranges of 30-100°C and 30-350°C and thermal conductivity in the longitudinal direction lower than 100W.m-1.K-1 can be obtained.