Thermal modeling of electrical contacts in switches and relays

A thermal modeling procedure has been developed to calculate the temperature distribution of components in complex 3-D switches and relays. The methods developed for dissecting the components, treatment of thermal interaction among the components, and calculating of interface thermal resistance are reported. In particular, the knowledge of electrical "a-spot" is used to estimate solid-solid contact area and void area. The void areas do not contribute to electrical conductivity but do contribute to thermal conductivity. The method is used to more accurately estimate the interface thermal resistance which is very important in any thermal analysis program. Actual switches and relays were modeled using finite difference thermal analysis, and the results matched well with measured temperatures.