How to improve heat sink performance: optimizing the base

Heat sink bases: a good foundation for a great solution

Heat sinks come in all shapes, sizes, styles and materials. But a common feature with many heat sinks is the base: the part of the heat sink that contacts the device(s) and supports extra surface area in the form of fins for increased heat transfer. The base is where different parts of the thermal solution are connected together and has a number of responsibilities to fulfill in order to be an effective solution.

Purpose of heat sink bases

Interface to device(s)

The base of the heat sink is where engineers contact heat sources that need cooling. Most electrical devices are designed to be contacted on the top, where heat has the path of least resistance away from the silicon chip. The finish and quality of the device surface and heat sink base are critical, especially in cases where thermal interface material (TIM) is not permissible in the application. Smoother surfaces will form fewer and smaller air gaps, which is why base flatness and surface finish help determine the heat sink’s actual thermal performance. Since there are no perfect surfaces in thermal management solutions, we use thermal interface material to decrease this contact resistance. In fact, thermal interface material is so important for the complete thermal management solution that there are entire companies solely focused on just TIMs.

A really effective way of improving the spreading capability of a heat sink base is to embed heat pipes. Heat spreading heat pipe assemblies leverage the rapid heat transport capabilities of two-phase cooling, which helps increase how well a heat sink base can spread heat to each of the fins.

Interface to extended surfaces

Heat sink bases that have fins added onto them may need some extra features to accommodate the fins. For zipper fins and folded fins, the heat sink base just needs to be flat. Bonded and brazed fin heat sinks require grooves to hold the fins and joining material in place.

Mechanical support

Finally, heat sink bases also provide mechanical support for the device(s) attached, especially those on a printed circuit board (PCB). Bases add rigidity to a delicate PCB. This can prove crucial for mechanically demanding applications, like those in transportation or consumer electronics. The nature of these applications are harsh and devices can be subjected to mechanical shock and vibration and daily abuse from its users.

Not just all about the base

Despite how important the base is, heat sinks also have several other important considerations. Fins, flow, thermal interface material and other features play an important role in determining the amount of heat transfer you have away from your device. But the base is the center of all the action and a good one will help keep you out of trouble.