Apple has revealed an unconventional thermal design for the upcoming iPhone Duo, featuring a flexible graphite pipe routed through the hinge to transfer heat between both halves of the folding device. Scheduled for release on October 23, the handset relies on custom internal packaging and a vapor chamber to sustain performance.
Engineering the A20 Pro for a Folding Display
Developing the A20 Pro processor required Apple’s engineering teams to rethink standard mobile chip architecture. Dan Murray, Apple’s vice president of silicon engineering, and Banafsheh Barabadi, senior manager of thermal product design, detailed the processor during an interview with PCMag. Unlike previous iPhone chips, the A20 Pro shifts away from a traditional package-on-package arrangement.
For iPhone Duo, we added a second display engine to support simultaneous operation of the inner and outer displays, and with the increased CPU and GPU performance, we ensure we can deliver a smooth user experience across the displays.
Dan Murray, Apple
Under the older POP method, the system-on-a-chip and the DRAM module sit in a vertical stack. Moving the memory directly on top of the processor creates a thermal bottleneck by limiting how efficiently heat escapes the silicon. For the A20 Pro, Apple adopted wafer-level multi-chip module packaging, placing the DRAM module directly beside the processor. That shift gives heat a more direct path to the vapor chamber.
The A20 Pro is Apple’s first 2nm iPhone processor, following the technology’s debut in the M6 chip for the Mac mini. The version built for the iPhone Duo also packs a second display engine to run the inner and outer screens simultaneously while supporting an under-display FaceTime camera.
The Graphite Hinge Pipe and Multi-Tier Cooling Architecture
Because a folding smartphone doubles in thickness when closed, trapped heat can quickly degrade performance. Apple countered this by routing a flexible graphite pipe through the hinge to move thermal energy between the device’s two halves. This mechanical bridge effectively doubles the surface area available for heat dissipation.
Barabadi noted that co-engineering the graphite pipe with the mechanical team demanded months of development. The material has to bend safely across thousands of hinge activations without losing its structural integrity or thermal connectivity.
Inside the chassis, the cooling setup relies on three primary components working in tandem with the hinge pipe. A custom vapor chamber floats in the center, and a specialized interface material sits between the chip and the thermal plane.
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.
Banafsheh Barabadi, Apple
Barabadi explained that the material creates a direct thermal and mechanically compliant coupling between the processor and the vapor chamber, eliminating older thermal bottlenecks.
Apple Targets Heavy Workloads with Combined Cooling Pillars
Apple aims for the best possible performance through these combined cooling pillars, targeting heavy workloads such as high-frame-rate gaming and multitasking on the large display.
