Higher Reliability for Hybrids and Printed Circuit Boards by Functional Thermal Testing

Thermal cycling of functioning electronic assemblies has proven to be a means to enhance field-reliability. This paper describes a unique testing device which proved to be both practical and cost-effective for performing rapid thermal cycling on automatic test equipment (ATE). By using liquid nitrogen for quick cooling and the resulting inert gas as the media to be blown across electronic assemblies, many gains were made in quick proof-of-design tests. A unique manual switching arrangement from a pair of commercially available chambers provides quick changeover from hot to cold ambient environment around the units under test (UUT). Adding blowers to each chamber for circulating the inert gas across the UUT achieves rapid temperature changes. New MIL specification requirements can now be met and the proven reliability enhancement techniques can now be used with any ATE. A programmed temperature cycle is also part of the features available from the Thermal Test Station (TTS) described.