Once upon a time, home computers were low-powered enough that they barely needed any cooling at all. An Amiga 500 didn’t even have a heatsink on the CPU, while the early Macintosh got by with a single teeny little fan.

Modern smartphones are far more powerful than these ancient machines, packed with multi-core processors running at speeds of many gigahertz. Even still, they’ve generally been able to get by without any active cooling devices. However, as manufacturers continue to push the envelope of performance, they’ve had to scramble for ways to suck heat out of these handheld computers. Vapor chamber cooling has risen as a solution to this problem, using simple physics to keep your handset humming along at maximum speed for longer.

Cool Runnings

Keeping a smartphone cool is a unique challenge compared to other computing devices. In a desktop or laptop computer, designers can rely on fans, heatsinks, and even water cooling loops with radiators to get heat out of a device. However, for a phone, these methods aren’t so practical. Any air vents would be quickly blocked by pocket lint, and even the slimmest fan or heatsink would add a huge amount of bulk, which is unacceptable for a handheld device.

Samsung has been using vapor chambers in phones for almost a decade, relying on them to keep thermal throttling to a minimum. Credit: Samsung

Thus far, smartphones have largely avoided heating issues in two ways. Firstly, by using low-power chipsets that simply don’t generate a lot of heat in the first place. Secondly, by thermally coupling the main chips to metal heat spreaders and sometimes the smartphone’s external housing, to effectively create a simple heatsink. However, smartphones continue to grow more powerful, generating more heat during demanding tasks like recording high-resolution video. Thus, engineers have had to find new ways to dump greater amounts of heat without compromising the aesthetics and usability of their devices.

Enter vapor chamber cooling. Picture a sealed metal cavity built into a smartphone, inside which is a small amount of water-based coolant. The phone’s chipset is thermally coupled to the cavity, such that the heat is absorbed by the coolant inside. Thanks to the physical properties of water, notably its huge specific heat value, it’s able to absorb a great deal of heat energy, particularly as it passes through the phase-change regime as the fluid turns from a liquid into a gas. As it heats up and vaporizes, the coolant spreads to fill the entire cavity, spreading the heat into the whole thermal mass of the casing where it can be released into the surroundings. As heat is released, the vapor cools back into a liquid, and the cycle can begin again. The idea is exactly the same as is used in heat pipes—where a liquid is heated beyond its phase change point into a vapor, and used to spread heat to other areas of a sealed cavity.

A visual demonstration of a vapor chamber at work. The fluid is heated until it evaporates, and then spreads around the cavity. Credit: Apple

The vapor chamber has benefits over traditional metal heatsinks. The liquid coolant is very effective at evaporating and spreading heat around the entire chamber, wicking heat away from hot chips more quickly. Traditional heatsinks can end up with a hotspot over individual chips, whereas the vapor chamber is more effective at distributing the heat over a wider area.

The intention behind this is to allow phones to run at maximum performance for longer. Whether you’re shooting video or playing a game, it’s no good if your phone has to start throttling clock rates to stay cool in the middle of a task. The vapor chamber simply helps engineers suck more heat out of a phone’s chipset and get rid of it faster.

Google has recently seen fit to include vapor chambers in various models of the Pixel 9 series, aiming to keep phones running at maximum performance for longer. Credit: Google

One drawback is that vapor chambers are obviously far more complex to manufacture than traditional heatsinks. Rather than a flat metal heat spreader, you have a delicate chamber into which coolant must be injected, and then the chamber must be sealed. The coolant must be able to soak up a great deal of heat, as well as safely deal with many cycles of vaporization and condensation, without causing any corrosion or damage to the chamber in the process. The entire vapor chamber must be able to survive the rough-and-tumble life of a handheld device that’s stuffed into pockets and thrown into bags every day of its life.

Vapor chambers have been around for a while now, first showing up in the Galaxy S7 in 2016. They’ve gradually become more popular, though, and these days, you’ll find a vapor chamber in phones like the Google Pixel 9 Pro, the Samsung Galaxy S25+, and the Apple iPhone 17 Pro and Pro Max. They’re still largely the preserve of flagship devices, perhaps as much due to their high-tech appeal and higher cost than traditional cooling solutions. Still, as the smartphone arms race continues, and these parts become more common, expect the technology to trickle down to more humble models in the years to come.

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