The Influence of Manufacturing Technology on
The Effectiveness of Nickel Diffusion Barriers
For High Temperature (100(C-200(C)
Dry Circuit Applications
P.W. Lees
Principal Technologist
Technical Materials, Incorporated
Subsidiary of Brush Engineered Materials, Inc.
Lincoln, Rhode Island, USA
ABSTRACT
Copper diffusion from base metal to an electrical contact surface is a well documented phenomenon. The subsequent oxidation of copper causes an increase in contact in contact resistance and may result in failure of the contact interface. Dry circuit contact surfaces are typically manufactured with a layer of nickel between the noble contact material and the base metal. The efficacy of this barrier layer in preventing copper diffusion to contact surface within the temperature range of 100(C to 200(C and beyond is dependent upon both the time of exposure and the manufacturing technology. This study examines nickel diffusion barriers produced by both electroplating and wrought technologies. Each manufacturing technology yields a characteristic microstructure. Electroplated and clad gold/nickel/copper samples were aged at temperatures in the range of 100(C to 200(C for times up to twenty weeks. Copper and nickel composition profiles were determined and the interdiffusion coefficients were calculated. Contact resistance was monitored as a function of aging time. Good correlation was found to occur between the calculated penetration distance for copper or nickel and observed contact resistance behavior. Guidelines for estimating material system performance based upon anticipated thermal exposure are given.
KEYWORDS: Clad Contact Materials, Contact Resistance, Copper Diffusion, Electroplated Contact Materials, Nickel Diffusion Barriers
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