One Powerful Decade Update: Vapor Chamber Heat Sinks

Aug 1, 2010 12:00 PM
Matt Connors Application Engineering Manager Thermacore, Inc.

To illustrate the thermal performance improvement that a vapor chamber can provide to an all-metallic heat sink, let’s examine the same heat sink described earlier, but with a vapor chamber integrated into the heat sink base. As shown in Fig. 4, the heat is spread much more evenly across the entire heat sink, causing a drop in overall thermal resistance of 19 percent. The heat sink shown here with an embedded vapor chamber and all of the parameters held constant exhibits a resistance of only 0.044 °C/watt. Vapor chambers also allow easier implementation of a folded fin or stamped fin. These fins can be directly soldered or glued onto the top of the chamber. The fin densities can be dramatically improved by using these types of fins due to the ability to increase pitch. Since the heat flux is so low exiting the vapor chamber, the additional resistance going through this fin-attach interface is inconsequential.

Higher Metal Heat Sink Performance

As illustrated, the enhanced performance of the vapor chamber improves the thermal performance of an all-metallic heat sink significantly. The improved thermal performance allows the electronic component designer to easily manage component frequency speed and power increases within the existing architecture, and at the same time, allow for much more computing/transmitting power for new designs in a more compact space. For example, if an IGBT component in a given system is reaching its maximum junction temperature at 1500 Watts, the vapor chamber can potentially increase the dissipated power to 1800 Watts without changing junction temperature. This is a great advantage for mechanical designers where changing the form factor of a given heat sink would prompt a costly overhaul of the enclosure layout.

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Fig. 5 shows a Therma-Base vapor chamber, which enables lower device temperature and greater component reliability. Like conventional heat sinks, vapor chambers are versatile enough to be freeze/thaw resilient and able to withstand military shock and vibration standards, but it’s important to consider those variables in the specification. Operating temperature, gravity orientation, and length of power transport are all factors to account for when tailoring a vapor chamber’s internal structure for a given application.

While conventional heat sinks may be suitable for use in low power, large heat source applications, it is applications where the performance of the system is limited by thermal/mechanical constraints (heat flux, overall power, space, mass) that the vapor chamber offers the ability to obtain the next level of speed and power in the same space.

Summary

The Therma-Base vapor chamber has an enhanced capability to accept higher heat fluxes than a traditional aluminum or copper surface. Its smaller size improves system packaging and provides quieter operation through less air flow. Able to operate in any orientation, the Therma-Base passes shock and vibration testing, and thermal cycling (freeze/thaw).”

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