A Modular Stackable Concept for Heat Removal From 3-D Stacked Chip Electronics by Interleaved Solid Spreaders and Synthetic Jets

A design for cooling 3-D stacked chip electronics is proposed using solid heat spreaders of high thermal conductivity interleaved between the chip layers. The spreaders conduct heat to the base of an advanced synthetic jet cooled heat sink. The stack conduction was investigated parametrically through computational modeling. The effect of the power dissipated, the heat transfer coefficient applied to the peripheral surface, the spreader thickness, spreader thermal conductivity, and the shape of via holes in the spreader were modeled. Results show that for moderate power dissipations, 5 W in each 27 x 38 mm layer, a 250 Am thick copper heat spreader would conduct heat adequately. In order to remove the heat from the edges of a five-layer stack and transfer it to the ambient air, a novel active heat sink design has been implemented using a matrix of integrated synthetic jets. In previous synthetic jet heat sink designs, cooling air is entrained upstream of the heat sink and is driven along the length of the fins, resulting in a significant rise in the air temperature and corresponding drop in streamwise heat transfer effectiveness. In the new design, synthetic jets emanate from the base of the fins so that the induced jets, and more importantly the entrained (cooling) ambient air, flow along the fin height. The significantly shorter flow path ensures rapid purging and replacement of the heated air with cool entrained air. Furthermore, in the matrix design the jets are spread uniformly throughout the heat sink such that all fin surfaces are subjected to the same airflow. The velocity field of the active heat sink is mapped using particle image velocimetry (PIV) and the configuration that maximizes the volume flow rate through the fins is investigated. Thermal performance is characterized using a surrogate heater and embedded thermocouple sensors. The thermal performance of identical heat sinks cooled by the two synthetic jet approaches is compared.