Thermal Fuse Crimp material
Copper being soft metal,  may or may not be poor crimp material for this application.  Some are silver plated brass, , stainless steel, some copper. It depends on the mating materials , ruggedness, operating conditions and tooling.

It MUST be  capable of a 5 pound pull test without fatique on resistance or strength.  It must  be a gas tight fitting, so that the mating surfaces do not oxidize and must be done with proper tooling for consistency.

Commercial equipment may use a spot welder but a high quality gas-tight crimp machine is cheaper.  There are many material types depending on other specs which were not given in the question, such as budget,qty.  &amp; reliability.