Key Considerations for Heat Sink Designs

A heat sink is a crucial thermal component, serving heat exchange purposes in electronic assemblies. The concept of its performance is simple – transfer thermal energy from where its generated (electronic component) to several points within the assembly where the heat will dissipate. The heat transfer is achieved by one or the combination of conduction, convection and radiation.

There are a number of factors that can influence the performance of a heat sink. The most important factors include the material, the heat sink fins, the attachment method, and the thermal interface material, all of which make up the heat sink design. This article shares 5 simple but key factors for consideration when looking to design an effective heat sink.  

1. Material

The material used in fabricating the heat sink determines some of the performance and functional characteristics of the heat sink. Materials such as aluminum and copper have excellent thermal conductivity. Copper and aluminum are very popular in heat sinks because of other properties like corrosion resistance, heat absorption, bio-fouling resistance and anti-microbial properties. 

For most conventional applications, aluminum will be the choice material because of availability and cost. Copper is usually reserved for end-uses that demand more performance. Copper boasts of twice the conductivity of aluminum, but can cost up to -4-6x the price of aluminum. From the design perspective, aluminum heat sinks can be extruded while copper heatsinks must be skived or machined. 

Finally, diamond is another material used in heat sinks. It has 5 times the conductivity of copper due to its latticed structure. It is deployed in applications where outstanding thermal diffusivity and conductivity greatly affect performance.

2. Heat Sink Fins 

A heat fin can be described as a flat plate with one end conducting heat and the other dissipating the heat into the surrounding fluid. The design of the heat sink fin can also impact its efficiency. For one, materials with higher thermal conductivity and lower aspect ratio have higher heat dissipation efficiency. Fin efficiency can also be improved in other materials by making them thicker or shorter.

3. Heat Sink Geometry 

Geometrical and positional considerations also affect the efficacy of a heat sink system. The rate of flow of the coolant medium is dependent on the arrangement of the fins in the heat sink. Heat sink fin configuration should be optimized to encounter less fluid flow resistance, and improve air circulation through the heat sink. 

Shape and size of the fins both impact heat transfer density. When modelling the heat sink and fin, different geometrical configurations should be tested to identify what will deliver performance optimization. 

4. Heat Sink Attachment Method

The performance of a heat sink can be hindered or enhanced by using the ideal attachment method to the electronic device. Heat sinks may be attached by epoxy, thermal tapes, standoff spacers, etc. Thermal engineers must consider both thermal and mechanical requirements in choosing the attachment method. The ideal attachment will not cause the component to overheat, and will remain in thermal contact with the heat sink through the vibrations that may arise in everyday usage of the electronic device. 

5. Surface Color 

Heat transfer primarily occurs through conduction, convection or radiation. In heat sinks, convection is the primary method for heat dissipation. However, in cases where convection is low, the system’s radiative cooling may come to the fore. Matte-black surfaces will radiate heat more efficiently than bare metals due to the low emissivity of the latter. 

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