It's an issue caused by a bad connection on the audio IC chip, the chip will need to be replaced which can only be done by someone that has micro-soldering experience.
You may be able to find someone locally in your area that does board-level repairs for iPhones.
Update (for microsolderers): The audio IC issue is caused by a bad connection on some solder points / pads on the logic board on the right hand side.
Reballing the chip can fix the issue but replacing the chip, reinforcing weak solder pads and use of jumper wires for broken pads on the logic board is a better option.
Edit: Updating answer to explain the audio IC issue
Here is more information about the audio IC fault on iPhone 7 in detail via YouTube video:
It's an issue caused by a bad connection on the audio IC chip, the chip will need to be replaced which can only be done by someone that has micro-soldering experience.
You may be able to find someone locally in your area that does board-level repairs for iPhones.
-
Update (for microsolderers): The audio IC issue is caused by a bad connection on some solder points / pads on the logic board on the right hand side.
+
Update (for microsolderers): The audio IC issue is caused by a bad connection on some solder points / pads on the logic board on the right hand side.
Reballing the chip can fix the issue but replacing the chip, reinforcing weak solder pads and use of jumper wires for broken pads on the logic board is a better option.
Edit: Updating answer to explain the audio IC issue
+
+
Here is more information about the audio IC fault on iPhone 7 in detail via YouTube video:
It's an issue caused by a bad connection on the audio IC chip, the chip will need to be replaced which can only be done by someone that has micro-soldering experience.
You may be able to find someone locally in your area that does board-level repairs for iPhones.
+
+
Update (for microsolderers): The audio IC issue is caused by a bad connection on some solder points / pads on the logic board on the right hand side.
+
+
Reballing the chip can fix the issue but replacing the chip, reinforcing weak solder pads and use of jumper wires for broken pads on the logic board is a better option.
+
+
Edit: Updating answer to explain the audio IC issue
It's an issue caused by a bad connection on the audio IC chip, the chip will need to be replaced which can only be done by someone that has micro-soldering experience.
You may be able to find someone locally in your area that does board-level repairs for iPhones.