While a folding iPhone posed a new challenge for Apple’s thermal engineering team, they came up with a creative way to leverage the device’s hinge to their advantage. Here are the details.
iPhone Duo’s hinge features a flexible graphite pipe
PCMag recently sat down with Dan Murray, Apple’s vice president of silicon engineering, and Banafsheh Barabadi, the company’s senior manager of thermal product design, to discuss the architecture of the A20 Pro chip.
The new SoC, which powers the iPhone 18 Pro, iPhone 18 Pro Max, and iPhone Duo, is Apple’s first iPhone chip built on a 2 nm process, following the technology’s debut with the M6 chip in the Mac mini in August.
And while the A20 Pro was designed with all three new iPhones in mind, the iPhone Duo version packs some additional capabilities. These include a second display engine to run both screens simultaneously.
The iPhone Duo’s A20 Pro variant is just slightly different. “For iPhone Duo, we added a second display engine to support simultaneous operation of the inner and outer displays,” says Murray, “and with the increased CPU and GPU performance, we ensure we can deliver a smooth user experience across the displays. For the inner display, we also added support for placing the FaceTime camera behind the display.”
The report offers a really interesting, in-depth look at the A20 Pro’s thermals and the new vapor chamber Apple developed to keep them at bay. That includes what Apple calls “metal over foam,” a material that iFixit also examined during its recent teardown of the iPhone 18 Pro.
The second pillar is a new material that bridges the gap between the A20 Pro and the vapor chamber. “We call it metal over foam,” says Barabadi, and it “basically creates a direct thermal and mechanically compliant coupling between the SoC and the vapor chamber. It is highly effective in removing the heat, meeting the strict mechanical requirements of the system. It took us months of development to get the material properties exactly right to be able to use this material.”
Perhaps the most interesting tidbit from the story is what Apple did to improve the iPhone Duo’s thermal performance, particularly given the challenges of dissipating heat in a device that doubles in thickness when folded.
“This was one of the most technically challenging aspects of our design,” says Barabadi. To surmount the issue, Apple routed a flexible graphite pipe through the hinge itself to transfer heat between the two halves, thereby increasing the surface area available for heat dissipation. “This part need[ed] to be co-engineered between our thermal team and the mechanical team. It’s a flexible material that needs to survive, as you can imagine, many hinge cycles while maintaining its thermal connectivity, and also its structural integrity throughout the product life cycle.”
PCMag’s interview with Murray and Barabadi also goes into the A20 Pro’s architecture, including the benefits of placing the DRAM next to the processor rather than stacking it on top, and you can read it in full here.
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