Effect of ion-implantation on the contact resistance of copper and silver-copper electrical contacts under fretting conditions

The effect of In+ and N+ ion-implantation on the contact resistance of copper and AgCu alloy wires in AgCu plates was investigated. In addition to contact-resistance measurements, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX) were used to study the processes involved. The fretting tests were carried out with simulated connector configuration at frequency of oscillation of 0.005 Hz, contact load 2 N and current 20 mA. The results showed that fretting adversely affects the contact resistance of copper connections, which shows a rapid increase and substantial fluctuations with fretting time. The effects of fretting were reduced significantly with N+ ion-implantation whereas In+ ion-implantation had practically no effect on the fluctuations in the contact resistance. Fretting had no effect on the contact resistance of AgCu-AgCu contacts. AES, EDX and SEM analyses revealed that considerable damage of the contact zones and substantial transfer of material occurred in the copper-AgCu connections as a result of the fretting action. Auger mapping of the wire and plate contact zones showed the presence of a substantial concentration of Si. The enrichment of these contact zones was associated with the contamination of the copper wires by the silicone-base lubricant used during drawing procedures.