Super interesting read over at iFixit; as Apple worked to pack more tech into the iPhone, the sheer tininess of certain components made the device particularly vulnerable to breaking down in the presence of helium.
But quartz oscillators have some problems. They don’t keep time as well at high (and low) temperatures, and they’re a relatively large component—1×3 mm or so. In their quest for smaller and smaller hardware, Apple has recently started using MEMS timing oscillators from a specialized company called SiTime to replace quartz components.
Helium can diffuse through the fusion bond oxide and cause the cavity pressure to increase. In our pressure sensors, helium could cause the absolute accuracy to temporarily degrade. In our gyro sensors, helium could cause the offset to drift and could cause the oscillation to temporarily stop.
Apple’s user guide for the iPhone and Apple watch admits this is a problem, just not one many people are going to run in to:
“Exposing iPhone to environments having high concentrations of industrial chemicals, including near evaporating liquified gasses such as helium, may damage or impair iPhone functionality. … If your device has been affected and shows signs of not powering on, the device can typically be recovered. Leave the unit unconnected from a charging cable and let it air out for approximately one week. The helium must fully dissipate from the device, and the device battery should fully discharge in the process. After a week, plug your device directly into a power adapter and let it charge for up to one hour. Then the device can be turned on again.”