The iPhone Duo’s cooling system hides a clever trick inside its hinge

The iPhone Duo, Apple's latest folded smartphone, presents a unique thermal engineering challenge for the company's team. To tackle this issue, they ingeniously utilized the device's hinge. PCMag interviewed Dan Murray, Apple's vice president of silicon engineering, and Banafsheh Barabadi, the senior manager of thermal product design, to delve into the A20 Pro chip's architecture that powers the iPhone 18 Pro, iPhone 18 Pro Max, and the iPhone Duo.

The A20 Pro is Apple's first iPhone chip built on a 2 nm process, following its debut in the M6 chip for the Mac mini. While designed for all three new iPhones, the iPhone Duo includes extra capabilities, such as a second display engine to run both screens at once. Murray explains that this enables simultaneous operation of the inner and outer displays with increased CPU and GPU performance for a smooth user experience.

A notable feature of the A20 Pro is Apple's "metal over foam" material, which facilitates efficient heat transfer between the SoC and the vapor chamber. Barabadi describes this material as "metal over foam," emphasizing its direct thermal and mechanically compliant coupling with the A20 Pro and the vapor chamber. This innovative design took months of development to perfect the material's properties, ensuring both thermal efficiency and mechanical compliance.

Perhaps the most intriguing aspect of Apple's thermal management strategy for the iPhone Duo is the use of a flexible graphite pipe routed through the hinge. This pipe bridges the gap between the two halves of the device, increasing the surface area available for heat dissipation. According to Barabadi, this co-engineered component between the thermal and mechanical teams is a flexible material that must maintain its thermal connectivity and structural integrity throughout the product's lifecycle.