How vapor chambers keep phones cool

The standard approach to cooling smartphones has used a solid, highly conductive plate made from a material like copper to spread heat. This approach relies on having a surface where heat can spread. Sometimes, fins are added to extend that surface, but this can lead to a thicker device. Most companies, however, are intent on making thinner and thinner phones.

Phase change technology—which has been used in laptops for decades, Goodson notes—achieves the same goal more effectively with fluid that boils and condenses to dissipate heat. These two-phase solutions include vapor chambers, like that used in the new iPhone, as well as narrow, finger-like structures called heat pipes.

Phones have limited volume to work with, and “performance per volume is critical,” says Victor Chiriac, CEO and co-founder of Global Cooling Technology Group, based in Phoenix. Thin and wide vapor chambers have a high heat removal capacity and offer an effective solution. The cycle between liquid and vapor is “a powerful mechanism for absorbing heat,” he says.

Apple’s vapor chamber efficiently spreads heat across the phone’s body.Apple

In Apple’s version, a small amount of deionized water is sealed in the chamber. The water evaporates when near heat sources, then condenses back into a liquid when the heat dissipates into the phone’s surrounding aluminum body. Water is often used in vapor chambers, though sometimes other materials are mixed in to avoid it freezing and cracking the seal, Chiriac says.

Vapor chamber manufacturing faces challenges

As Apple, Samsung, and others push the boundaries of how thin phones can get, manufacturability of vapor chambers may become a challenge. While solid materials can easily be shaved down, these chambers need to have enough space for coolant to travel through channels. The chambers have to be perfectly sealed in order to work properly, and “the thinner you make it, the less space you have for that secret sauce to do its thing,” Chiriac says.

It comes down to physics: “A big challenge in small devices like phones is that as you scale down the thickness of a vapor chamber, the fluid physics aggressively scale back their performance relative to copper and other solid heat conductors,” Goodson explains. (This is a problem that researchers, including his students, are working to address with new microstructures.) Plus, vapor chambers tend to be expensive to manufacture.

Still, Apple and other companies have decided to invest in this technology for their most powerful phone models. Goodson suspects part of that decision is to leverage the “wow” factor. But, he says, “with time this approach will likely become an industry standard.”