Effect of Crystallographic Orientation on Contact Resistance of Electroplated Nickel Alloys

The contact resistance of electrodeposited nickel doped with Sb, In, Zn, and P on copper coupons has been studied. After accelerated aging at 35°C and 95% relative humidity for 7 days, nickel deposits with (111) or (220) preferred orientations exhibit no degradation in the contact resistance. However, deposits with the (100) preferred orientation show a large increase in the contact resistance. From an initial value of about 10 mΩ before aging, the contact resistance increases after aging fourfold in Ni(P) deposits and almost 20‐fold in Ni(Sb) deposits. This result is attributed to faster oxide film formation on the (100) plane than on the (111) planes. Furthermore, we suggest that the addition of dopant elements in the nickel bath increases the overvoltage to form the doped nickel deposits. Therefore, the orientation with the lowest overvoltage, namely, the (111), is formed from the doped nickel bath at the same current density as that at which the (100) orientation will form from a pure nickel bath. The transition from the (111) to the (100) preferred orientation occurs at a higher current density in the doped nickel baths.