Cooling solutions for a no-air-flow and low-junction-temperature application

Thermal management problems involving PCI cards are growing as devices and components on the cards are dissipating more power. The spacing limitation, i.e. spacing between cards, as well as airflow conditions seriously limit the effectiveness of many conventional cooling solutions that are usually at the disposal of thermal engineers. Novel cooling solutions are needed in order to meet the growing thermal requirements involving PCI cards. A heat-dissipating chip on a PCI card is located in a stagnant airflow area when the card is plugged into a conventional computer chassis. Worse yet, the maximum allowable junction temperature for the chip is extremely low at 70°C. Various conventional cooling options are explored and tested. Taking practicality, reliability, and effectiveness all into consideration, a conclusion is reached that conventional heat sinks and fan/sink assemblies can not provide a satisfactory cooling solution. Instead, a heat pipe/heat sink assembly is designed and tested. Utilizing the high heat transfer capability of heat pipes, thermal energy dissipated from the chip can be efficiently transported from a stagnant airflow region to a specially designed heat sink located in an area on the PCI card where there is significant airflow. Test results and subsequent thermal analysis indicate that the heat pipe/heat sink assembly is a practical and satisfactory cooling solution for this particular application