Thermal characterization and optimization of a blower heat sink for small form factor micro-computer desktop applications

The drive to develop competitive thermal management desktop solutions that achieve thermal performance levels of less than 0.3 degrees C/Watt (case-ambient) while maintaining aggressive weight and volume constraints has lead to a continual need to provide heat sink solutions with increasing fin densities. However, increasing fin densities have the detrimental effect of increasing pressure drop and reducing airflow performance. A transition point is eventually obtained in which traditional axial fan technology can no longer provide heat sink performance improvements, and high-pressure centrifugal blower solutions must be pursued. This paper describes a significant re-engineering effort of the traditional heat sink to support a centrifugal blower air-moving concept. With the objective of taking heat sinks to a higher level of fin density, a novel custom centrifugal blower design was configured to meet application specific geometry, noise, weight and attachment constraints. Commercially available blowers were benchmarked to a custom blower and comparisons are indicated with respect to airflow performance, power usage and noise levels. While no blowers were available in the exact required form factor, the custom blower was observed to perform with superior noise and power characteristics. Modeling considerations in developing the optimal thermal design are presented. As well, prototype test results outline the thermal characteristics associated with fin density, fin material, fin height, fin length, and fin style. Preliminary findings observed thermal resistance levels (c-a) of 0.25 degrees C/Watt, with superior power and acoustic characteristics as compared to conventional heat sink designs.