A new cooling technique is proposed to simultaneously enhance the heat transfer and significantly reduce the prohibitive high temperatures usually reached by high-powered chips embedded in the last generation of packages. A comparison between flow and heat transfer characteristics for several types of microelectronic cooling arrangements was conducted using a numerical investigation. The maximum temperature and local heat transfer coefficient were determined on a single heated chip cooled by a channel flow, a steady impinging jet, and an oscillatory impinging jet at a Reynolds number of 600. A uniform inlet velocity was used for the channel flow calculation, and the upper and lower channel walls confined the jets. The calculation domain for the three simulations was identical; the steady jet configuration had an inlet jet width twice that of the unsteady jet.
The results indicate that the unsteady nature of the confined impinging jet greatly enhances the removal of heat transfer and reduces the high temperatures on the heated chip. The jet core becomes distorted and buckles beyond a critical Reynolds number of 600, which leads to a sweeping motion of its tip (stagnation point). As a result of the combined buckling/sweeping jet motion, the cooled area is significantly enhanced. A comparison between the unsteady impinging jet and the stationary impinging jet reveals that the heat transfer enhancement provided by the unsteady jet is at least two times better. A 25% cooling enhancement is observed when compared with the channel flow technique, yet the jet uses a flow rate 6.3 times lower, therefore a smaller pumping power.
The new cooling method does not require the incorporation of costly heat sinks and heat spreaders, or the unnecessary increase of pumping power/blower work, yet provides effective cooling at significantly reduced manufacturing/operating costs.