Selecting heat sinks for heavily populated boards

Focus:

In the context of this article, a heavily populated board is a pc-board that contains multiple components that require heatsinks. When specifying the heatsinks for this type of application, designers must not only consider the thermal performance of each heatsink by itself, but also its impact on airflow in the application. In other words, designers must consider the thermal resistance of the heatsink and the reduction in air pressure (pressure drop) it produces in the application. (The latter concept is also described as airflow management.) Ideally, designers would like heatsinks with lowest thermal resistance and lowest pressure drop. However, these are conflicting requirements as low thermal resistance typically implies more surface area and greater fin density, which in turn implies high pressure drop. This article discusses how to balance these requirements by applying what's described as the "minimum-cooling-power approach." An experiment is conducted to demonstrate the importance of airflow management in heatsink selection. Article concludes with a discussion of the advantages of using splayed pin fin heatsinks to achieve low pressure drop for a given level of thermal performance.

What you’ll learn:

• How to understand the importance of airflow management when cooling heavily populated pc boards
• How to select heatsinks for pc boards that require multiple heatsinks

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Author & Publication:

Barry Dagan and Philip Raynham, Cool Innovations Inc , EDN, May 14 2009

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