Apple has routed a flexible graphite pipe through the hinge of its foldable iPhone Duo to improve heat dissipation. The design transfers heat between the phone’s two halves, helping address the thermal challenges of a foldable device.
The engineering approach was discussed by Dan Murray, Apple’s vice president of silicon engineering, and Banafsheh Barabadi, the company’s senior manager of thermal product design, in an interview with PCMag. They also explained the architecture of Apple’s new A20 Pro chip, which powers the iPhone 18 Pro, iPhone 18 Pro Max and iPhone Duo.
The A20 Pro is Apple’s first iPhone processor built using a 2-nanometer manufacturing process. iPhone Duo version includes additional features to support its foldable design. Apple added a second display engine so the inner and outer screens can operate simultaneously. The chip also supports placing the FaceTime camera behind the inner display.
The device uses a new material called ‘metal over foam’ to connect the processor to its vapor chamber. The material helps transfer heat while meeting the phone’s mechanical requirements.
"We call it metal over foam," says Barabadi, “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”, he added.
Apple also developed a way to move heat between the two halves of the foldable phone. The flexible graphite pipe runs through the hinge, expanding the surface area available to release heat.
Barabadi said the component required close coordination between the thermal and mechanical engineering teams. The pipe must withstand repeated folding while preserving its ability to transfer heat and maintain structural strength throughout the device’s life.
The design highlights the challenges of cooling a foldable phone, where components must fit into a compact structure that changes shape during use. Apple’s hinge-based solution combines thermal management with the mechanical demands of a device designed to fold repeatedly.
Also Read: iPhone Duo: How Apple’s Foldable Design Changes the Smartphone Experience