Today we’ll be kicking off a three part series on Heat Sink Testing Methods and Common Oversights. This important phase in developing a thermal management solution can sometimes be overlooked. While CFD is a critical first step, the actual testing of physical samples verifies your data and insures your design meets the real world application needs.
The effective use of an electrical component is limited by its maximum operational junction temperature. To achieve a desired component temperature, excess heat dissipated by the device must be transferred to the environment [1]. The most common method for transferring heat from the component to the environment is to use a heat sink.
To estimate a component’s junction temperature, a required value is the heat sinks thermal resistance. The thermal resistance of a heat sink can be determined analytically or experimentally. This article looks at three experimental methods of testing heat sinks.
First, it is necessary to understand the heat transfer path from the component to the environment, and then to understand the differences between the practical and experimental application of a heat sink.
Heat Sink Mounted On a Component: Practical Use
In a practical application, the heat transferred to the air from multiple junctions of a component follows a complex 3D heat transfer path. Simplified, the heat transferred from the junction of a component, 
, to the air follows two heat transfer paths, as shown in Figure 1. The first heat transfer path is from the junction to the air via the heat sink 
The second path is also from the junction to the air, but via the board 
The portion of heat transfer via the heat sink depends on the thermal resistance of the two paths.
For BGA components without a heat sink, heat transfer to a board is typically 80% of the total heat transfer rate. When a heat sink is mounted to the BGA, the thermal resistance from the case to the air is decreased. Heat transfer to the board will decrease and more heat will be transferred to the air.
Figure 1. Heat Sink Applied to a Component, Mounted on a Board.
In part 2 of our 3 part series on Heat Sink Testing, we’ll cover three examples of how to do this testing. CLICK HERE FOR PART 2
ATS’s Thermal Characterization Lab is the perfect partner to help you put this 3 part article series into practice. And the best part is, the first half day is free! Click here to learn more: Thermal Characterization Lab
References
1. Sergent, J. and Krum, A., Thermal Management Handbook for Electronic Assemblies, First Edition, McGraw-Hill, 1998.
2. Advanced Thermal Solutions, Inc., Data Sheet for maxiFLOW ATS-52425P-C2-R0 Heat Sink. http://media.digikey.com/pdf/Data%20Sheets/Advanced%20Thermal%20Solutions%20PDFs/ATS-52425P-C2-R0.pdf
3. Advanced Thermal Solutions, Inc., Heat Sink Design and Characterization, Tutorial.