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Smaller version of the original iPad Pro. Released March 31, 2016. Features a 9.7" display, A9X processor, and 32/128/256 GB storage options. Available in Silver, Space Grey, Gold, and Rose Gold.

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Home Button replacement on iPad Pro 9.7

I tried repairing a torn flex (between the button and the chip, where it folds) on an iPad Pro 9.7. I have the correct tools, microscope, and the skills, but it is so tiny, the work is very tedious. (And yes, I have watched the repair video on YouTube - it's not the easy one.)

I'm giving up and buying a new button because the owner is okay with the lack of Touch ID functionality - I used the pin code to get in and disable passcoding.

But... I hatched a different plan.
I unsoldered the 'cap' over the chip, and removed the chip, a 4x5 ball array, ~1.7mm x 2.1mm package). The plan was to buy a new button and replace its chip with the security matched chip. I think it is doable. But (you will all laugh), It went flying from my tweezer when I attempted to turn it over for re-balling, never to be found on my work area floor, full of equipment and parts. At that point I gave up and ordered a new button.

Has anyone attempted this sucessfully? I think it can be done. I'm quite sure it contains the logic for the home button wire array decoding and an eprom for the security matchup to the logic board. Obviously, Apple can put new buttons in and change the syncing with special software through the USB cable - that's how I would design it.

If you want to discuss this in greater detail, use my email

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The security part is the sensor chip adhered to the button itself, if you are replacing the standalone chip on the cable, it won't work.

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Therefore, could one, theoretically, marry a working button to a new flex with its working chip? What is the function of the chip mounted to the upper flex? If it is just the fingerprint decoder, it should work. (You can see where I’m going with this.) I should be able to take my working button, and overlap solder it to a new flex and gain back my Touch ID. Theoretically, and the stars all align.

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@thepilotsmith retain the original button, try replace and splice the rest if it works. The small chip probably has nothing to do with Touch ID encoding, the fingerprint image capture, encoding and encryption is probably done directly in the sensor chip.

Or the small chip has some function such as storage, I have no documentation for the cable, I don’t know.

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So, to be clear, there are two parts to this problem.

1. The security sync with the logic board; the two must match.

2. The fingerprint encoding (memory, encoding, and a possible "success" signal back to the logic board that is only accepted if the pairing of button and board is valid.

All conjecture, at this point. If in fact the pairing is on the back of the button, then why not just remove that chip and place it on a new button/flex assembly? Apple is smarter than that. I'll bet there's more to it than we are able to decypher, without knowledge of their code. I think we're done.

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@thepilotsmith The fingerprint scanner doesn't work like the way you imagined it. It only captures the capacitive image of your fingerprint, encrypt it and send it to the phone CPU, the CPU decrypts it and verify for an unlock. Nothing is compared on the sensor chip, it's just a "camera".

To prevent bus eavesdropping and DMA attacks illegally recording and replaying the fingerprint data, the traffic between the sensor chip and the security portion of the CPU is encrypted using a key only known by them, that's why you can't replace the button without Apple's programming, the key provisioning can only be done using their factory equipment.

You can't remove the sensor chip from the button crystal, the chip is thinner than human hair and the glue used to bond the chip to the crystal is stronger than the chip itself. I don't see any way you can pull it off.

You CAN splice the cable back together as long as the button end is preserved and you have the skills to reattach the cable, other people have done it.

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@tomchai

Thanks Tom. The “camera” concept went right over my head. I see now how this works with the encrypted communication. Excellent! So the only real alternative (besides Apple’s intervention), is to carefully surface splice the existing button on to a newer flex. I attempted the ‘wire splice’ under my microscope, and found it impossible; I’m getting too old for the micro stuff. But if the two halves are scraped clear of surface coating, and mated precisely, I think capillary soldering might work. Trust me, I will never again break a Home Button flex!

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