Experimental investigation of a micro jets - based cooling package for electronic applications

At present, most of the electronic components are cooled by means of heat sinks attached to them and by blowing air with fans. Unfortunately, this technique does not allow removing very high power without the heat sinks size becoming bulky or the fan becoming too large. An even bigger limitation of direct air-cooling appears when dealing with high heat fluxes, which are common since the chips’ size is becoming smaller by the day. Because reliability and speed of any chip depend on the working temperature, which normally must be below 120 C, new techniques are needed to improve the heat removed per unit surface area and volume. Electronic components such as power IGBTs can require a heat removal rate up to 250 W/cm. An approach to accomplish such a formidable heat flux could be to use liquid micro jets sprayed on the cooling surface. The use of micro jets allows a fine control of the thickness of the liquid film that is deposited on the cooling surface. Studies have been conducted on this subject and heat fluxes as high as 300 W/cm at relatively low flow rates, low surface temperatures, and associated pressure drops have been achieved. The objective of the present work is to develop a closed loop cooling module, consisting of an orifice plate for creating micro-jets, a pump and an air cooled condenser. The impinging micro-jets allow high heat fluxes through the cooling surface at relatively low surface temperature. A small aluminum module, with pin fins on the outside, of only 1 dm in volume has been manufactured and tested. A diode was used as the heat source and it was cooled with micro-jets 140 μm in diameter impinging normal to the surface. The test fluid was water. Heat fluxes up to 300 W/cm at a surface temperature, of 80 C, were easily achieved. The effect of all major parameters, such as liquid flow rate, amount of non-condensibles present in the chamber, and airflow rate was investigated.