Recovering data from the eMMC wouldn’t be that hard if he had a datasheet. An eMMC is an embedded Multi Media Card, basicly an SD card, but it would require an expensive adapter PCB, which could easily cost a few 100€. I have worked on iphones with waterdamage before and know how to deal with these problems. Drying it doesn’t do anything, in fact you have the best chances of recovery when you bring the phone to a repair shop when it’s still wet.
If it dries it leaves nasty corrosion everywhere, causing shorts. Luckly most shorts aren’t that bad, as they commonly occur at capacitors between ground and VCCx.x.
As you describe the problem, the issue is somewhere in the PMIC section, as the LED still works, which indicates that the phone isn’t completely dead. I have high hopes for this device.
The standard procedure for this kind of issue is:
-
Take appart and rinse the board and the connectors with some 99% ethanol
-
Take off the shields with a hot air gun or if they are sticker shields, just peel them
-
Wash with ultrasonic cleaner for a maybe 1/2 an hour and immedialty rinse with ethanol again
-
Manually clean the board with ethanol under the microscope
-
If there are capacitors that are obviously damaged, take them off, most of them are decoupling capacitors that aren’t manditory, but can effect stability, but should be fine for data recovery, most of the times the phones work fine without them, if you really want you can replace them with some 1µF capacitors of the appropriate size.
-
If still not booting, you can check the capacitors and their resistance with an multimeter, everything over 50ohm is usually fine. If you have an short on the power rails, you can check if sth is a power rails by looking if it comes from an inductor, try searching for the faulty capacitor/corrosion.
It is common that some of the repaired waterdamaged phone have high battery drain, due to some smaller shorts still remaining, but for data recovery, not a problem, they might also be fully functional, who knows, it’s always a bit luck.
If none of this helps, you probably have sth blown up like PMIC or have some corrosion under the ICs and in the worst case some short destroyed the CPU, in these cases there’s nothing to do about it and the board goes to the pile of donor boards.
We don’t have schematics for the FP2, I hope we’ll get them one day, but it’s unlikely, because qualcomm likes to keep things confidential.