Influence of Contact Pressure on the Specific Electrical Contact Resistance of Copper

The specific electrical contact resistance (SECR) [
$\Omega \text{m}^{2}$
] of Cu-ETP (CW004A) contacts is characterized in dependence of contact pressure up to high pressures close to the tensile strength of the base material. Two different material states are considered, R200 (soft) and R300. Static four-wire measurements are carried out on a special experimental setup, which favors homogeneous contact states during mechanical loading. A finite-element simulation is utilized for interpretation and evaluation of the measurements, including the deformation of the samples during the test. The results show that the SECR of the harder material state R300 is higher than that of the softer material R200. The developed data show a decrease of SECR with increasing contact pressure. For contact pressures up to 0.5 of the tensile strength
$\sigma _{t}$
of the base material, the SECR decreases according to a power law. For contact pressures above
$0.6~\sigma _{t}$
, the decrease shifts toward a linear behavior. In addition, the measurements show that the SECR vanishes at contact pressures in region of the tensile strength of the base material.