In an October 13 interview with PCMag, Apple engineers described the iPhone Duo cooling system as a path from A20 Pro to a vapor chamber, plus a flexible graphite pipe through the hinge that transfers heat between the phone’s two halves. The design details come from the interview conducted by Eric Zeman with Apple engineers Dan Murray and Banafsheh Barabadi.
Apple introduced iPhone Duo on September 9, 2026. The new engineering account adds detail to NeoTeo’s earlier coverage of Apple’s then-unconfirmed foldable iPhone.
How Apple describes the iPhone Duo cooling system
A20 Pro uses wafer-level multichip module (WMCM) packaging, which places DRAM beside the system-on-chip (SoC), rather than stacking the memory directly on top of the processor. Dan Murray said earlier iPhone SoCs used package-on-package (POP) packaging, with DRAM above the SoC—a layout that can make it harder to draw heat from the chip into the rest of the system.
Banafsheh Barabadi described “metal over foam” as the interface coupling A20 Pro to the vapor chamber. It is designed to transfer heat while accommodating the mechanical demands of the assembly. The Duo’s chamber is thinner than the one described for iPhone 18 Pro and sits within the device rather than serving as its central structural plane.
From the chamber, a flexible graphite pipe runs through the hinge to transfer heat between the Duo’s two halves. Barabadi said the part must retain both thermal connectivity and structural integrity through repeated hinge movement; she did not give a cycle count.
How the Duo differs from iPhone 18 Pro
Apple’s engineers describe a different arrangement for iPhone 18 Pro and iPhone 18 Pro Max. Their vapor chamber serves as a structural plane, with the battery and logic board mounted directly to it. Barabadi said the iPhone 18 Pro chamber has three times the surface area of the iPhone 17 Pro chamber. That comparison applies to those Pro models, not to iPhone Duo.
The Pro models also use a nanotwin copper plate beneath the display and a high-conductivity graphite layer. The combination is intended to spread heat across the display and reduce hotspots. The Duo’s distinctive element in the account is instead the flexible graphite pipe crossing its hinge.
Apple’s performance claim and iPhone Duo dates
Apple says iPhone Duo delivers up to 35% better sustained performance than iPhone 17 Pro. That is a company claim: PCMag said its testing had not yet included A20 Pro in the Duo when it published the interview.
The architecture Apple describes centers on a vapor chamber and a graphite heat-transfer path. Apple’s September 9 announcement scheduled preorders to begin October 16, 2026, with availability set for October 23, 2026.
