A heat dissipation component for a semiconductor element includes: a composite part containing 50-80 vol % diamond powder with the remainder having metal including aluminum, the diamond powder having a particle diameter volume distribution first peak at 5-25 m and a second peak at 55-195 m. A ratio between a volume distribution area at particle diameters of 1-35 m and a volume distribution area at particle diameters of 45-205 m is 1:9 to 4:6; surface layers on both composite part principal surfaces, each of the surface layers containing 80 vol % or more metal including aluminum and having a film thickness of 0.03-0.2 mm; and a crystalline Ni layer and an Au layer on at least one of the surface layers, the crystalline Ni layer having a film thickness of 0.5-6.5 m, and the Au layer having a film thickness of 0.05 m or larger.

A composite is obtained by press-molding a mixed powder comprising 20-50 vol % of a metal powder and 50-80 vol % of a diamond powder for which a first peak in a volumetric distribution of particle size lies at 5-25 m, and a second peak lies at 55-195 m, and a ratio between the area of a volumetric distribution of particle sizes of 1-35 m and the area of a volumetric distribution of particle sizes of 45-205 m is from 1:9 to 4:6, thereby obtaining a composite having a high thermal conductivity and a coefficient of thermal expansion close to that of semiconductor devices, which is easy to mold into a prescribed shape.

An aluminum-diamond composite that exhibits both high thermal conductivity and a coefficient of thermal expansion close to that of semiconductor devices, and that can suppress the occurrence of swelling, etc., of a surface metal layer portion even in actual use under a high load. An aluminum-diamond composite includes 65-80 vol % of a diamond powder having a roundness of at least 0.94, for which a first peak in a volumetric distribution of grain size lies at 5-25 m, and a second peak lies at 55-195 m, and a ratio between the area of the volumetric distribution of grain sizes of 1-35 m and the area of the volumetric distribution of grain sizes of 45-205 m is from 1:9 to 4:6; the balance being composed of a metal containing aluminum.

A metal foil including: a steel layer whose thickness is 10 to 200 m; an Al-containing metal layer arranged on the steel layer; and plural granular alloys which exist in an interface between the steel layer and the Al-containing metal layer, wherein, when a cutting-plane line of a surface of the Al-containing metal layer is defined as a contour curve and an approximation straight line of the contour curve is defined as a contour average straight line, a maximum point, whose distance from the contour average straight line is more than 10 m, is absent on the contour curve, and wherein, when an equivalent sphere diameter of the granular alloys is x in units of m and a thickness of the Al-containing metal layer is T in units of m, the granular alloys satisfy x0.5T.

A composite is obtained by press-molding a mixed powder comprising 20-50 vol % of a metal powder and 50-80 vol % of a diamond powder for which a first peak in a volumetric distribution of particle size lies at 5-25 m, and a second peak lies at 55-195 m, and a ratio between the area of a volumetric distribution of particle sizes of 1-35 m and the area of a volumetric distribution of particle sizes of 45-205 m is from 1:9 to 4:6, thereby obtaining a composite having a high thermal conductivity and a coefficient of thermal expansion close to that of semiconductor devices, which is easy to mold into a prescribed shape.

An aluminum-diamond composite that exhibits both high thermal conductivity and a coefficient of thermal expansion close to that of semiconductor devices, and that can suppress the occurrence of swelling, etc., of a surface metal layer portion even in actual use under a high load. An aluminum-diamond composite includes 65-80 vol % of a diamond powder having a roundness of at least 0.94, for which a first peak in a volumetric distribution of grain size lies at 5-25 m, and a second peak lies at 55-195 m, and a ratio between the area of the volumetric distribution of grain sizes of 1-35 m and the area of the volumetric distribution of grain sizes of 45-205 m is from 1:9 to 4:6; the balance being composed of a metal containing aluminum.