This is the common iPhone 7/7+ audio ic issue. The good news is that this problem IS REPAIRABLE.
The independent repair community has fixed thousands of these cases and we now know exactly what the specific defect is now. The C12 pad for the master clock line of the audio ic chip on the logic board gets stretched/lifted/pulled/weakened simply from normal use of the phone. This is a very similar problem to the iPhone 6 plus touch disease. Both defects share the same underlying biology—-the iPhone logic board is screwed down into a relatively flexible/bendy housing and this causes the logic board to experience flexion forces that it can’t handle. (Similar in concept to bending a paper clip back and forth a few dozen times.) In similarly sized Samsung devices, the logic board “floats” in the housing and is not subjected to these same forces.[br]
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The repair is to desolder the audio ic, add a thin wire to enhance the connection of the C12 pad to the master clock line, reball the audio ic and resolder it the board. With the microjumper in place, the phone becomes immunized against the recurrence of this classic problem in the future.[br]
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We have trained hundreds of microsoldering students in the US and Internationally, so people will have an increasingly good chance of being able to find a local logic board repair expert that can fix their iPhone 7 audio issue since the manufacturer never will. If you can’t find a local microsolderer, then there is always mail in repair. [br]