Effects of Surface Roughness and Aging on the Electrical Contact Resistance and Residual Stress in Gold-Nickel-Copper Connector Materials.

摘要

The purpose of this research is to investigate the effects of surface roughness and aging environment on the electrical contact resistance and residual stress in nickel and nickel/gold coated copper. In order to accomplish these research objectives, oxygen free copper coupons were prepared to a variety of average surface roughnesses (Ra ranging from 0.05 urn to 2.5 urn) prior to coating application. Three coating systems were investigated: Au/Ni plating, Ni plating, and Ni sputtering. The majority of this research focuses on the Au/Ni plated samples, with Ni plated and Ni sputtered data included for comparison. Nickel, gold, and copper are commonly used in electrical components, such as electrical contacts, in which component reliability is of great importance. As there are a wide variety of environments to which electrical components could be exposed to during service, the coated samples were aged for up to nine weeks in one of three aging environments: mixed flowing gas/atmospheric corrosion (MFG), elevated temperature and relative humidity (TRH), and thermal cycling (TC). The mixed flowing gas/atmospheric corrosion environment was created by using a Battelle Class 2 environment with the following conditions: 30 C, 70 % relative humidity, 200 ppb N02, 10 ppb H2S, and 10 ppb CU. The elevated temperature and relative humidity environment maintained samples at a constant temperature and relative humidity of 40 C and 85%, respectively. Samples in the thermal cycling environment were cycled between temperatures of-40 C and 60 C with a 15 minute dwell time and an approximately 4.5 C/minute ramp rate. Characterization using optical profilometry, optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), x-ray diffraction (XRD), and electrical contact resistance (ECR) measurements allowed for the determination of changes in the coupons due to the coating system, surface preparation, and environmental exposure.