Lots of people know that a damaged Home Button can always be replaced on an iPhone with an universal Home Button flex, which doesn’t support Touch ID any more. But can a Home Button be actually repaired and Touch ID still works? The answer is YES!
The most essential part of a Home Button flex is the microchip which stores one’s Touch ID information, shown below. As long as this microchip is intact and undamaged the Home Button flex can be fixed. To assure personal security, a Home Button microchip is always encrypted and the Touch ID can only works with its host iPhone. That’s why we can not move a Home Button flex from one iPhone to another and the Touch ID still works. But the microchip can be transplanted to a donor Home Button flex and restore the Touch ID.
A universal Home Button flex is not a qualified donor. Refer to image below. The upper one is a genuine Home Button flex, and the lower one is an universal one. They have different circuit design and the Touch ID microchip doesn’t fit into a universal Home Button flex.
You need to find a genuine Home Button flex to do the transplant. You can find one from a used iPhone as shown below (it needs to be from the same iPhone model).
With a heat gun, gently remove the Touch ID microchip from the damaged Home Button flex and the good Home Button flex. Solder the Touch ID microchip from the broken Home Button to the donor Home Button flex. Fix the repaired Home Button to its original iPhone. The Touch ID is restored!