Thermal management has become a key design parameter in modern electronic devices―everything from personal computers and tablets to specialized computing equipment. To combat the thermal management challenges associated with these designs, many of these devices now incorporate heat pipes and vapor chambers. Whether your design utilizes standard heat pipes or a custom vapor chamber solution, consider these four parameters before you choose a solution for your design.
For more information on how heat pipes function, check out our introduction to heat pipes.
1. Heat Pipe Dimensions & Shapes
Heat pipes, as the name suggests, are generally cylindrical, metallic components. Modern heat pipes can vary in length, thickness, and cross-section shape. The most common cross-section shapes are:
- Round
- Rectangular
- Square
- Flat
Flat heat pipes have a more oval or rectangular shape with flat, long side edges. Keep in mind that flat-shaped heat pipes still maintain an internal volume. The image below features a CPU cooler's round and flat shaped heat pipe. On the left side of the image, where the heat pipe attaches to a heat sink, the heat pipe has a circular shape. But as it transitions to the CPU side of the thermal spreader, the heat pipe flattens.
2. Vapor Chambers vs. Heat Pipes
As designs become smaller and more complex, they naturally have less working space. Therefore, some space-saving new heat pipe shape configurations have come to market: vapor chambers. Vapor chambers often feature custom or unique shapes and are designed for a particular space. You'll commonly find these devices in laptops and tablets, where space and effectiveness are of the utmost concern. Vapor chambers look much like traditional heat pipes, but they consist of the same fundamental physical characteristics.
3. Heat Pipe Thermal Conductivity
A heat pipe's thermal conductivity is a critical parameter to consider when manufacturers match components with devices. We usually measure thermal conductivity in Watts, which is denoted by the unit "Q."
4. Heat Pipe Wick Material
Heat pipes consist of an outer shell and an internal structure that wicks the working fluid from the condenser to the heat source. The heat pipe's wicking type directly influences the system's capillary action potential. There are two common heat pipe wick types: grooved and sintered copper powder.
- Grooved heat pipes are more cost effective, as they can be manufactured using an extrusion process. These pipes, which are heavily influenced by gravity, are generally used in a vertical orientation.
- Sintered copper powder, which is actually in solid form and not a fluid powder, features much higher capillary action potential and is less influenced by gravity. However, sintered copper powder heat pipes are more costly to manufacture.
Heat Pipe Purchase Considerations
When used in conjunction with heat sinks and fans, heat pipes can be the perfect thermal management solution for your design. Keep these critical parameters in mind as you design a heat pipe to meet your thermal management needs.