According to industry data, the trend in the heat load per product footprint has grown tenfold for server and communications applications over the past decade – to more than 6,000W/ft2 in some applications – and it is projected to go even higher. This makes thermal transfer a more crucial aspect of electronics design, writes Southco’s Nick Bennett.
Mechanical heat-sink devices, featuring a fin design with a high surface area to footprint ratio, are one method used to transfer heat away from electronic components but the attachment option chosen for their installation could have a significant impact on the efficiency of the thermal management design. In order to optimise the heat transfer performance it is essential to maintain a consistent fastening.
Plastic clips offer a low-cost method, but reliability can be challenged by shock, vibration or heat sink weight. Retaining clips provide for easier heat-sink replacement, but reliability has been shown to vary during shock testing and they can require removal of the centre fin material, where most of the heat is typically absorbed.
Other mechanical fastening options that provide better tolerance to shock, vibration and alignment include a variety of screw, pin and spring attachments, in both loose and captive hardware designs. Captive designs help to avoid problems with loose hardware posing potential short-circuit problems on printed circuit boards. They can also simplify screw alignment for easier assembly even in crowded, compact PCB layouts.
Spring-loaded, self-levelling heat-sink fastening hardware that maintains consistent pressure across the surface of the heat-generating component, and automatically adjusts to compensate for thermal expansion, also helps to improve thermal transfer performance, used either with or without compressible pads. The best advice is to consider the question of heat-sink attachment as an integral part of the design process.