By Josh Perry, Editor
[email protected]

In the latest article from Advanced Thermal Solutions, Inc. (ATS), a leading-edge engineering company based in Norwood, Mass., the concept of spreading resistance in the base of a heat sink that is larger than the component is calculated and used to model and optimize a heat sink for enhanced thermal performance.

The article outlines how to optimize heat sink base spreading resistance to enhance thermal performance. (Advanced Thermal Solutions, Inc.)

“The heat, q, originates from the source, spreads out over the base and dissipates into the fluid on the other side with heat transfer coefficient, h. For heat transfer through finned heat sinks, the effective heat transfer coefficient is related to thermal resistance of the fins,” the article explained.

It continued, “The derivation of the analytical solution starts with the Laplace equation for conduction heat transfer and applying the boundary conditions.”

There are full solutions and approximations for determining spreading resistance and, according to the article, the percentage error increases with increases in the length of the heat sink, but those errors are relatively low.

The article said, “Less than 10% error is expected for lengths up to 50 mm; five times the length of the heater. This is acceptable for most engineering problems since analytical solutions are first-cut approximations that should later be verified through empirical testing and/or CFD simulations.”

To reduce spreading resistance (and ultimately lower the junction temperature of the component on which the heat sink rests), engineers can increase base thickness but that impacts the height of the fins, as space is limited in most electronics systems, and that lowers the overall heat transfer coefficient.

“Techniques such as higher conductivity materials, embedded heat pipes, vapor chambers etc. are available if the spreading resistance is major obstacle in the cooling,” the article concluded. “Thermal engineers must balance the increased weight and cost of such techniques against the benefits for each application.”

Read more about this subject and get examples of the calculations for determining spreading resistance at https://www.qats.com/cms/2018/08/13/optimizing-heat-sink-base-spreading-resistance-to-enhance-thermal-performance.