Investigation of nickel-nickel contacts in portable computer battery pack applications

Recent advances in the portable computer industry have increased the demands on battery pack performance and intensified interest in the long-term reliability of battery contacts. This paper characterizes the relation between contact resistance and force of the popular Ni-Ni contact interface at various stages of oxidation. The virgin Ni-Ni interface exhibited contact resistances of less than 30 mΩ at contact forces greater than 40 g. However, contacts exposed to a Battelle Class II mixed flowing gas (MFG) environment for up to six days and contacts subjected to 85°C/85% RH conditions for 500 bouts showed resistances as high as 200 Ω at 150 g and 1 kΩ at 100 g. The effects of repeated mating and wiping also were evaluated; fifty cycles of repeated mating at contact forces up to 150 g did not make a discernable difference but a single wipe at 150 g reduced the contact resistance significantly.