Normal force reduction in electronic contacts

Elevated temperature heat aging tests were performed on dual cantilever beam gold-plated-over-nickel, phosphor bronze electrical contacts. The normal force provided by the beams was directly measured before and after heat-aging. A series of curves relating change of normal force with time was obtained for the temperature range 100 to 200°C. These curves shows that the normal force reduces with time. The rate of this reduction is found to increase with elevated temperature. The results of the tests were used to develop a model of the behaviour of the normal force with time and temperature. The model can be used for predicting the amount of normal force reduction that has taken place after a given time at a specified temperature. Confidence bands were calculated for the model parameters. The limitations of the use of the model are described