Heat spreader technology for silicon chip

Abstract

After the introduction of the Pentium™ processor in 1993, the trend of the processor performance and power consumption have been increased significantly each year. Heat dissipation has been increased but in contrast the size of die on the processor has been reduced or kept the same due to nano-size circuit technology, thus making the heat flux critically high. The heat flux was about 10–15 W/cm2 in the year 2000 and had reached 100 W/cm2 in 2006. For effective cooling, the least temperature gradient between the heat source and radiating components is required. There is a limit to solve thermal issue only by heat-sink improvement in this case, because of size limitation. Minimizing thermal resistance of CPU package itself is required. Thermal interface between silicon die and heat spreader has changed from thermal grease to phase-change-material (i.e. PCM). Recently, some model use indium as thermal interface. Meanwhile heat spreader design doesn't change much. The best-known device for effective heat transfer or heat spreading with the lowest thermal resistance are heat pipe and vapor chambers, which are two-phase heat transfer devices with excellent heat spreading and heat transfer characteristics. In this paper, newly designed vapor chamber is proposed to spread heat from CPU to the heat sink. This newly proposed vapor chamber consists of micro channel wick structure instead of the traditional sintered powder wick. In traditional vapor chamber, often ballooning problem occurs. However in the case of micro channel vapor chamber this problem can be improved.