Ladder shape micro channels employed high performance micro cooling system for ULSI

The success of an IC cooling system or heat sink for ULSI depends on the ability to achieve effective heat transfer rate to the flowing liquid and superior flow performance of the micro channels. The effective heat transfer requires large wall area that is in contact with the flowing liquid and availability of large mass of fluid to carry away the heat. Conventionally a collection of parallel rectangular micro channels have been used to achieve this. However, there is a practical maximum limit on the number of channels that can be imbedded in the back surface of the substrate by bulk etching. In this paper, the authors propose a collection of ladder shape micro channels with rectangular cross section that effectively increases the wall area thus decreasing the thermal resistance and increases heat transfer coefficient. Two parallel rectangular channels are connected by one or more link channels to form a ladder shape micro channel. The flow performance of these ladder shape micro channels have also been studied using COMSOL multi physics and the comparison of the flow performance indicating parameters of the collection of conventional rectangular channels with the proposed collection of ladder shape micro channels show that the high performance heat sinking can be achieved using the proposed ladder shape micro channels. Further the thermal responses of these micro systems have also been studied extensively and these studies show that the thermal resistance decreases with the introduction of ladder shape micro channels considerably. Finally the substrate strength has also been estimated using IntelliSuite Software and it shows that the rigidity of the substrate is slightly lower in ladder shape micro channel carved substrates but the degradation is highly insignificant. (C) 2012 Elsevier Ltd. All rights reserved.