Novel Thermal Packaging Approach for an Airtight Electronic Chassis without Card Retainer-I

Abstract

The card retainer mechanism is mostly the preferred tool to simply fasten a PCB card to the chassis to have a thermal conduction path. Depending on the card retainer design, thermal contact resistance between the retainer and chassis wall can differ. For a 150W heat-load PCB card, the contact resistance may cause more than a 10°C temperature increment on the electronic components regardless of the location on the card. This temperature rise in the card may not be affordable as the available cooling air temperature is 71°C or higher for an aircraft application. Considering the aviation platform and the abnormal cases, intermittent operation temperature can reach the value of 71°C for a 30-minute duration. In this study, a novel packaging approach is developed for a high-power card to get rid of the thermal contact resistance thanks to eliminating the card retainer mechanism. The card with its cold plate is driven to the chassis from one of the side walls through the slot and it stops at the opposite wall. The cooling fins are on the cold plate rather than on the chassis, therefore there is no contact resistance between the fins and the cold plate. Gaskets are used to have an airtight design between the cold plate and the wall. All studies are performed both numerically and experimentally to evaluate the novel approach. In the end, thermally promising results are obtained for harsh environments.