What is Heat Pipe?

Heat pipe is a high-efficiency heat conductor. A typical heat pipe consists of a vessel in which its inner walls are lined with a wick structure. The heat pipe vessel is first vacuumed, then charged with a working fluid, and hermetically sealed. When the heat pipe is heated at one end, the working fluid evaporates from liquid to vapor (phase change). The vapor travels through the hollow core of the heat pipe to the other end of the heat pipe at near sonic speed, where heat energy is being removed by a heat sink or other means. Here, the vapor condenses back to liquid and releases heat at the same time. The liquid then travels back to the original end of the heat pipe via the wick by capillary action and repeat the heat removal.

When to consider Heat Pipe?

There are three thermal conditions that may lead to the use of heat pipe: 1. Heat pipe to act as a primary heat conductive Thermal Path – When a heat source and heat sink need to be placed apart, a heat pipe can be a very effective thermal path for heat transportation from the heat source to the heat sink. 2. Heat pipe to aid heat conducting of a solid – Heat pipe can add the efficiency and transport capacity of a thermal shunt. 3. Heat pipe to aid heat spreading across the plane – Heat pipe can be used to increase the heat spreading across a large heat sink base, thereby effectively increasing the heat sink base thermal conductivity. The effect of this is the decrease of the temperature gradient across the heat sink base (increase in efficiency), thereby lowering the heat source temperature. Refer to our Slim Cold Plate.

What are the materials of Heat Pipe?

Our heat pipe is made from copper pipe, and charged de-ionized water as working fluid.

How Can I bend Heat Pipe?

Heat pipe is very soft and can be bended as regular copper pipes by using pipe-bending tool. Note that the recommended bending radius is at least 3.5 of pipe diameter. Enertron designs and produces custom bend heat pipes.

How Can I flatten Heat Pipe?

Heat pipe is very soft and can be flattened by using a hand press. Note that the recommended flat thickness is at least half of pipe diameter. Enertron can flatten heat pipes for customers if inquired.

Can I solder Heat Pipe?

Yes. Low temperature, Bismuth Tin (BiSn) at 136C with reflow temperature at 150C is highly suggested for soldering heat pipes. Excess reflow temperature will expand and buckle the heat pipe, especially for flat heat pipes, due to excess internal vapor pressure.
If higher temperature must be used, PbSn 37/63 at 183C is allowable for short period of time (<30min), too. Note that lead is not RoHS compliant and high temperature cannot be used for flat heat pipe.

How can I mount Heat Pipe on Heat Sink?

There are three ways to mount heat pipes.
1. Crimp into a groove (thermal grease/ epoxy). Typically flattening the crimp section of heat pipe.
2. Sandwich heat pipe between plates (thermal grease/ epoxy).
3. Solder heat pipe in the groove. If your system will be subjected to vibrations and high shock loads, soldering will be the best way.

Can Heat Pipe stand for freeze and thaw cycles?

More than 50% of our heat pipe applications are in military, aviation and terrestrial. Most of them are subjected to freeze/thaw cycles and vibration. We helped customers to design the heat pipe into the application that can withstand the freeze/thaw cycles and vibration requirements. Our customers have performed the validation that proofs the heat pipe assembly meets freeze/thaw cycles, and vibration requirements.

Can I use Heat Pipe against gravity?

Yes, but the Heat Pipe performance is worse when used against gravity. Please refer to our Heat Pipe Test Report.

What is the nickel plating thickness on a Ni-plated Heat Pipe?

0.0003″ to 0.0006″ (7um to 15um).

What is the typical pipe length made for Custom Heat Pipe?

3mm diameter: 100 mm – 300 mm
4mm diameter: 100 mm – 300 mm
5mm diameter: 70 mm – 400 mm
6mm diameter: 70 mm – 600 mm
8mm diameter: 70 mm – 600 mm
10mm diameter: 100 mm – 400 mm

What is Enertron's lead time on Custom Heat Pipe?

Our typical lead time is 4 weeks.

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