- Apple built a flexible graphite pipe into the iPhone Duo hinge to dissipate excess heat between the two chassis halves when folded.
- Combined with an unstacked A20 Pro SoC and vapor chamber, the active thermal hinge helps maintain peak performance for longer under heavy loads.
- Android foldables have used graphite sheets as part of the display stack or on the chassis on either side of the spine, but have not typically used the spine itself for cooling.
Foldables have spent years balancing thinner profiles with flagship-grade SoCs and the resulting thermal dilemma. When unfolded, you have a large surface area that is great for thermal dissipation, but when folded, you create a thermal sandwich that suddenly has to work with only half the surface area. Apple appears to have solved this on its first foldable, the iPhone Duo, by incorporating the hinge into the phone’s cooling structure.
According to a PCMag interview with Apple’s thermal and silicon engineering teams, the iPhone Duo’s fold itself was one of the device’s toughest thermal roadblocks. While book-style foldables are usually razor-thin when open, closing them stacks the chassis, effectively doubling the thickness while reducing the surface area available for heat dissipation. If you trap a flagship processor in a compact sandwich, that’s a recipe for some aggressive thermal throttling.