Copper alloy, copper alloy plastic working material, component for electronic/electrical devices, terminal, bus bar, lead frame and heat dissipation substrate

A copper alloy comprising:

• Mg in an amount of greater than 10 mass ppm and less than 100 mass ppm;
• Ag in an amount of 5 mass ppm or greater and 20 mass ppm or less;
• and
• a balance being Cu and inevitable impurities, wherein
• the inevitable impurities comprise;
• S in an amount of 10 mass ppm or less,
• P in an amount of 10 mass ppm or less,
• Se in an amount of 5 mass ppm or less,
• Te in an amount of 5 mass ppm or less,
• Sb in an amount of 5 mass ppm or less,
• Bi in an amount of 5 mass ppm or less, and
• As in an amount of 5 mass ppm or less,
• a total amount of S, P, Se, Te, Sb, Bi, and As is 30 mass ppm or less,
• when the amount of Mg is represented as [Mg] and the total amount of S, P, Se, Te, Sb, Bi, and As is represented as [S+P+Se+Te+Sb+Bi+As], a mass ratio thereof, [Mg]/[S+P +Se+Te+Sb+Bi+As] is 0.6 or greater and 50 or less,
• an electrical conductivity is 98.0% IACS or greater,
• a residual stress ratio RSG (%) in a direction parallel to a rolling direction after holding at 200° C. for 4 hours is 20% or greater,
• a half-softening temperature is 200° C. or higher, and
• in a case where the copper alloy is measured by an EBSD method in a measurement area of 10000 μm2 or greater at every measurement interval of 0.25 μm, measured results are analyzed by data analysis software OIM to obtain a CI value at each measurement point, a measurement point at which the CI value is 0.1 or less is removed, an orientation difference between crystal grains is analyzed, a boundary having 15° or greater of an orientation difference between neighboring measurement points is assigned as a crystal grain boundary, an average grain size A is acquired according to Area Fraction, the copper alloy is measured by the EBSD method at every measurement interval which is 1/10 or less of the average grain size A, measured results are analyzed by the data analysis software OIM with a total area of 10000 μm2 or greater in a plurality of visual fields such that a total of 1000 or more crystal grains are included to obtain a CI value at each measurement point, a measurement point at which the CI value is 0.1 or less is removed, an orientation difference between crystal grains is analyzed, and a boundary having 5° or greater of an orientation difference between neighboring pixels is assigned as a crystal grain boundary, an average value of Kernel Average Misorientation (KAM) values is 2.4 or less.