Heat pipes and vapor chambers are two-phase devices that offer engineers versatile solutions to improve thermal performance. Here are four tips for when to use 2-phase based heat sinks.
Tip #1: When heat needs to be moved. The effective thermal conductivity of two-phase devices increases with the distance heat is moved, far exceeding that of solid aluminum or copper. Further, heat pipes can be bent to avoid PCB keep-out zones on their way from the heat source to the fin stack. A useful rule of thumb is that heat being moved farther than 50mm or will benefit markedly from using heat pipes.
Tip #2: When heat needs to be spread in all directions. High heat flux ICs or those with hotspots often require efficient heat spreaders to meet thermal goals. Adding embedded heat pipes or replacing the base with a vapor chamber (shown) allows thermal budgets to remain below target. While vapor chambers are the performance option when they are acting as the heat sink base plate, heat pipes can be embedded into an aluminum or copper metal plate.
Tip #3: When additional fin area is required. When reducing maximum fan speed requirements or increasing the thermal capacity of the heat sink, additional fin area is usually needed. This grows the length, width, and/or height of the fins, translating to a bigger base (not shown) and/or fins that need additional contact with the heat source (shown below).
Heat Pipes Allow Both Fin Base and Mid-Fin Contact to Heat Source
Tip #4: When low weight and/or minimum vertical stack height is a design goal. A heat sink using a vapor chamber base can be roughly the same weight as one with an aluminum base yet has half the thermal resistance and be 2mm thinner.
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