Here’s what we know about the iPhone’s vapor chamber cooling system

No one wants a heat wave burning in the heart of their smartphone. That’s why Apple developed an advanced vapor chamber system for the powerful A19 Pro chip inside its latest iPhone 17 Pro phones.

Apple’s A19-based Pro iPhones are probably the most powerful smartphones on the planet, packing what the company calls MacBook Pro level performance inside their small frame. That performance relies on a chip that offers a 6-core CPU, 6-core GPU, and a 16-core Neural Engine that can deliver up to 40% better performance than the previous generations of iPhone Pro. Initial independent performance benchmarks seem to bear that Apple claim out.

Performance like this comes from the heart, which is why Apple designed a new vapor chamber-based thermal management system to help direct heat away from the processor. It needs this because even with Apple chips, this kind of performance generates heat.

What does it do?

To handle the heat, Apple’s design kitchen baked thermal management into the overall design of the new iPhones, including the aluminum unibody, which uses an Apple-designed, aerospace-grade alloy to optimize heat dissipation. This provides 20 times the thermal conductivity of the titanium used in the last generation iPhones. 

Smartphones usually rely on a solid conductive plate made from a material such as copper to spread heat. The idea is that this plate heats up and then dissipates the heat through the chassis of the phone.

Vapor cooling takes this a few steps further. As also used by Samsung and Google, this kind of phase-change technology adds fluid to the equation, which boils and condenses inside the device to use up that heat energy and dissipate it. 

To assist with that dissipation, Apple connects the cooling part of the chamber to the unibody and battery plate, so that heat is lost more swiftly. Therefore, the hermetically sealed vapor chamber inside the new iPhone is essential to the cooling system. 

How does it work?

According to Apple, it works like this: “Deionized water is sealed inside the vapor chamber, which is laser-welded into the aluminum chassis to move heat away from the powerful A19 Pro, allowing it to operate at even higher performance levels. The heat is carried into the forged aluminum unibody, where it is distributed evenly through the system, managing power and surface temperatures to deliver incredible performance while remaining comfortable to hold.”

If you watched Apple’s iPhone presentation earlier this month, you’ll be aware the vapor chamber itself is very thin and relatively wide in terms of the scale of the device. That’s deliberate, as it gives the best possible performance by volume within the shape of the phone. 

An IEEE Spectrum report warns of some potential pitfalls — the use of water in the chamber means the cooling contraption needs to be perfectly sealed, and the new iPhones haven’t yet been available long enough to even begin to speculate on how long they will remain efficient/sealed. At the same time, as chip performance improves and smartphones shrink, you can expect cooling systems of this kind to become standard.

The annual iFixIt iPhone Pro Max teardown reveals a little more about the vapor chamber system. It tells us it sits between the heat-generating chips and the “giant heatsink” of the battery.

What iFixit found

The company looked inside the vapor chamber, and reported it “spreads heat from the A19 Pro chip into a water-filled copper lattice that boils, evaporates, and condenses in a constant loop. That cycle pulls heat away from the processor and into the phone’s frame.”

The amount of liquid it contains is so small they didn’t notice a drop of it when researchers opened up the chamber. The teardown also reveals the cooling system uses a mesh between two plates to distribute water throughout the chamber. The site also showed microscopic images of the interior of the new component, calling this, “pretty, practical, and now profoundly Apple.”

How well does it work?

The chamber might be pretty, but how effective is it? 

iFixIt has an answer to that, as well, sharing thermal camera data that found the iPhone 16 Pro Max hit 37.8 degrees Celsius at peak performance — and its chip was then throttled. The iPhone 17 Pro Max reached 34.8 degrees at peak and remained unthrottled. In other words, you can anticipate much higher performance on a sustained basis in the new device, so you won’t burn yourself during a sustained gaming session or while using any other app that demands consistent performance and power. 

The result? The cooling system appears to be efficient enough that these smartphones should be able to handle anything you want without becoming too hot to handle.

One more thing: It absolutely hints at big leaps in system performance on other Apple devices as chips based on the A19 Pro processor appear; just how much performance might we anticipate in a vapor chamber-cooled MacBook Pro running an M-series variant of these chips, for example? 

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