Heat Sinks And Electronic Cooling For Thermal Management

Heat sinks and electronic cooling are the most common methods for thermal management in electronic systems.

Thermal management is needed to ensure that a product will operate within the specified thermal ratings for the various components. For example, standard ICs are rated for usage within the “commercial temperature range” of 0C to 70C. When the ambient temperature of the system rises above 70C, the IC may not operate as specified in the data sheet or cease to work at all. Elevated temperatures also decrease the usable life of the component.

Electronic cooling can use one or more fans to decrease the temperature within an enclosure by replacing the heated internal air with cooler external air. The convection process also provides cooling to the components as the air passes over them. Additional cooling for high temperature components can be achieved by attaching a dedicated fan to an individual component. This approach is most often used for cooling the CPU, ASIC or FPGA.

Another method of electronic cooling uses a thermoelectric cooler (TEC) which transfers heat away from the component.  These TEC are solid state devices made of two dissimilar materials layer on top of each other. The TEC is attached to a component or thermally conductive portion of a printed circuit board. Passing an electric current through the TEC materials creates a heat flux at the junction of the materials causing heat to be transferred away from the component. This is referred to the “Peltier Effect” and the thermoelectric coolers are marketed as “Peltier Modules”.

The most widely used, and least expensive, method of cooling uses a simple heat sink. A heat sink is a shaped metal which is attached directly to a component using either a thermally conductive glue / pad or a bolt. The heat sink has a number of fins, much like a radiator, which increases the effective surface area of the component to provide greater heat dissipation.

Standard heat sinks in a variety of configurations (e.g., rectangular TO-220, square CPU/FPGA, generic U-shaped) can be at ASSMANN-WSW components and purchased through Digi-Key.

Depending on the amount of cooling required, factoring in the operational environment and system usage, a designer may need to use a combination of heat sinks, fans and TEC to meet the thermal management and cooling specifications. Software tools are available to help calculate heat dissipation based on the data sheet parameters of the active components and assist designers with their thermal management plan. Finished products can be viewed with thermal scanners to check for hot spots and overall thermal patterns while running the product under various operational scenarios.

(Photo Credit – ASSMANN-WSW components)

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