apples-iphone-6-6-plus-are-failing-early-thanks-to-touch-disease-bending-problems

Touch. It’s a critical part of how we navigate the real world and, thanks to the success of the original iPhone, a core component of modern smartphones. Apple has been at the forefront of introducing various touch capabilities, but its iPhone 6 and 6 Plus appear to suffer from design flaws that are killing the devices more quickly than one would expect.
As iFixit reports (and our own EIC Jamie Lendino can attest), an increasing number of iPhone 6 and 6 Plus devices are showing up in shops with the same problem: A gray, flickering bar at the top of the display and a non-responsive touchscreen.
“This issue is widespread enough that I feel like almost every iPhone 6/6+ has a touch of it (no pun intended) and are like ticking bombs just waiting to act up,” Jason Villmer, owner of STS Telecom—a board repair shop in Missouri, told iFixit. According to multiple sources, the problem has already been identified, and it’s a familiar problem for Mac users: The underfill layer underneath the chips that handle the phone’s touchscreen degrades over time.

The touchscreen ICs. Photo by iFixit

Back in 2008, Nvidia disclosed that certain Macs had underfill problems. Both the Mac and iPhone use ball grid array (BGA) chips that are connected to the PCB via an array of solder balls or bumps. The spaces between the bumps are filled by a material known as an underfill — it provides additional structural support and helps keep the solder bumps from flexing or cracking if the device is put under stress. In 2008, Nvidia was forced to replace or repair a wide range of systems because the underfill material it chose held up poorly under thermal stress. The iPhone 6 and 6 Plus have a different problem. The underfill that connects touchscreen chips to the rest of the device isn’t failing due to heat but thanks to physical deformation of the device.

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The iPhone 5s was the first Apple device to skip the underfill layer for touchscreen ICs, according to iPad Rehab. This appeared to cause no problems, so Apple didn’t use an underfill on the iPhone 6 or 6 Plus, either. Here’s how the site describes the failure mode.
The combination of a lack of underfill on the touch ic chips, plus their relative position on the board–seated on a span of board like a swinging bridge between two anchoring screws–and the inherent ‘bendiness’ of the sexy, slim iPhone 6/6+ is a perfect set up for what we are seeing now. Our mail-in logic board repair service sees hundred of iPhone boards, which allows us to notice patterns in the failures of these devices. This is our working hypothesis with what we think is going on with iPhone 6/6+ touch ic disease.
Initially the iPhone 6/6+ works fine.  Over time, normal daily use of the large, thin phone will eventually create a small crack or separation in one of the balls that underlie either of the touch ic chips on the board. At first, there may be no defect at all. Later you might notice that the screen is sometimes unresponsive, but it is quick to come back with a hard reset.
As the crack deepens into a full separation of the chip/board bond, the periods of no touch function become more frequent. This is exacerbated by any drop–which is a great way to fully sever an existing bga joint crack.
In the short term, the device can be torqued or pressured into working (by literally squeezing it) but this is strictly a short-term solution. Small cracks eventually expand, stress points fracture, and voila — your iPhone is now a paperweight. The iPad Rehab link goes on to describe how the solution is to replace the touchscreen ICs entirely — simply reflowing the solder isn’t always enough to ensure a solid bond and the likelihood of another failure is high. Dropping the device also hastens the failure rate.
It’s important to note that since all of this information is unofficial, we can’t say Apple has endorsed this explanation of the problem. Nonetheless, it makes sense. The problem may be exacerbated if Apple sells refurbished devices without replacing the touchscreen ICs (iPad Rehab doubts they replace the boards but again, we have no information from Apple itself).
Apple isn’t immune to public pressure; the company changed its practices last year after it became apparent that DRM lockouts introduced in iOS 9 were bricking devices people had previously repaired. If touchscreen failures are a major problem with the iPhone 6 and 6 Plus, Apple needs to repair the issue whether devices are in-warranty or not. It also needs to clarify whether the iPhone 6s and 6s Plus are affected, and how it’ll avoid the issue with the upcoming iPhone 7.
It’s also a problem that links back to the bending problems the iPhone 6 and 6 Plus suffered from not long after their debut. While tests showed that the iPhone 6 / 6 Plus could withstand normal pressure, the increased flexibility combined with the lack of underfill and the physical location of the chips appears to have created an issue that wouldn’t otherwise exist.