Study and optimization of advanced heat sinks for processors

The main task of this project is the development of a modular heat exchanger to dissipate a TDP (Total Dissipated Power) of 140-180 W on a microprocessor. This exchanger should be able to dissipate the reference target TDP respecting the maximum operating temperatures (above these temperatures the CPU goes into thermal throttle) and the longevity temperatures (lower than the thermal throttle temperatures). This result should be achieved while providing product versatility (based on the concept to adapt the exchanger to each socket), acceptable noise, acceptable size and cost. The heart of the project is the design of a suitable fin surface to protect processors with high TDP. In this case, a significant increase in fan speed and in the size of the finned body is inevitable. In this way, an increase in the heat removal is obtained by larger airflow rate (high number of revolutions of the fan) and the large exchange surface. Considering the impact of these changes, the design of the exchanger is extremely critical in terms of size and noise level. Another physical limit is represented by the progressive and unavoidable phenomenon of electro migration that afflicts each circuit, the more the temperatures separate from those of longevity, the lower the useful life of the CPU. Once the longevity temperature is exceeded, the useful life of the processor decreases with increasing temperatures until the thermal throttle temperature is reached, which causes an abnormal system shutdown. The processors with a TDP from 65W to 95W are the most numerous. For this reason, most aftermarket solutions are designed to dissipate this TDP. The main purpose of this study is to examine the best geometry for a modular exchanger that is able to effectively dissipate the higher TDP (up to 180W) typical of modern high performance processors. For this purpose the Golden-section search is introduced for optimizing the number of fins. The heat exchange is simulated with fluid dynamic simulations (CFD). This new study allows obtaining an optimal design for the construction of the exchanger. The use of an optimal finned surface avoids the use of heat pipes. This approach simplifies the design. Moreover, by using materials with high thermal conductivity (such as copper alloys instead of aluminium alloys) we can certify the heat exchanger for TDP larger than the design one and therefore cope with even higher thermal loads. In this way, we can also effectively dissipate very performant CPUs (very uncommon) with extremely high TDPs such as FX-9590 with a 220W TDP (declared by the manufacturer AMD), maintaining in any case temperatures below the maximum thermal specifications.