Apple Details Cooling Overhaul Behind iPhone Duo's Foldable Design

Apple has explained how it kept its first foldable iPhone cool. Engineers told PCMag that the iPhone Duo uses a flexible graphite pipe routed through the hinge to carry heat between its two halves. AppleInsider and 9to5Mac reported the same details. Foldables have little room for thermal hardware, and a hinge is an awkward place to move heat through. Apple says the answer was to spread heat across more of the device rather than let it build up around the chip. Four-part thermal design Apple described its approach as resting on four elements: Direct silicon-to-cooling path. Heat leaves the chip and reaches the cooling system without passing through extra layers. Metal-over-foam coupling material. This new layer moves heat while flexing with the chassis. Engineers said it took months to tune. Larger vapor chamber. Its surface area is roughly three times that of earlier designs. Nanotube copper plate on the display. It adds further heat-spreading capacity on the screen side. The hinge graphite pipe was developed together with Apple's mechanical teams so it can survive repeated folding. Chip packaging The A20 Pro in the Duo uses wafer-level multichip module packaging. This places the DRAM beside the processor instead of on top of it, so heat spreads sideways rather than stacking above the chip. Why it matters According to the reports, the changes let Apple fit a second display engine and an under-display FaceTime camera into the Duo while keeping higher CPU and GPU performance. Apple says this builds on vapor-chamber work already used in recent Pro iPhones. Sustained performance is a common weak point for thin devices, since sustained heat usually forces the chip to slow down. Apple's claim is that the Duo avoids this despite its folding form factor. Independent testing after release will show whether that holds under heavy real-world use.