Thermal management of silicon-based multichip modules

Thermal characteristics of silicon-based multichip modules and their associated heat sinks are presented. The structure of the multichip modules allows the heat generated inside a chip to be conducted away to the heat sink through the solder balls between the chips and the silicon substrate. The internal thermal resistances thus depend on the number of solder balls as well as the number of layers of insulators on the chip and the substrate. A thermal test module which has dimensions 59×59 mm mounted with nine thermal chips has been tested. The module can dissipate about 43 W at a chip temperature rise of 60°C when a heat sink with fin height of 25 mm is used at 1 m/s airflow. The heat sink has seven doubly folded fins which are thermally optimized to give the best cooling performance while keeping the lowest pressure drop across the heat sink at a given airflow rate