Make and Break Properties of Electrodeposits

Properties of thin precious metal electrodeposits used as contact materials on base metals under make and break conditions are described. The investigations were carried out with the aid of a model device which simulated conditions existing in relays. The electrodeposits tested were AuCo 0.3, AuPd6Cu2, Pd, PdNi20, Rh, and Ag/Rh sandwich. For these electrodeposits contact resistance is discussed in dependence on the number of operations for different electric loads (28550 mA dc, 12-60 V, ohmic). At voltages below 12 V and currents below 100 mA with a 5 µm thick Rh-, Pd-, PdNi20-, and a 10 µm thick AuPd6Cu2 layer more than 107 operations are available with no Rt(max) value above 100 m At the same voltage but with 5µm AuCo 0.3 even at a current of 30 mA only 106 operations are possible. Below 12 V/100 mA doubling of the layer thickness gives rise to a doubling of the operation number. For all electrodeposits it is valid that at higher voltages and currents the maximum number of operations decreases significantly and this nearly independent on the layer thickness.