A copper busbar has at least one stepped hole for fastening a cable shoe vi a screw connection. The stepped hole extends from a first surface of the copper busbar to a second surface of the copper busbar. The stepped hole has at least a first region, a second region and a third region, wherein the first region of the stepped hole adjoins the first surface, with a radius of the stepped hole being constant over the length of the second region with the second radius value. The third region adjoins the second surface, wherein the third region has at least at the second surface a radius with a third radius value which is less than the second radius value.