" A Signature Design Fault " Weak Audio IC and Logic board connection in iPhone 7/7+
Weak soldering is typical defect of Apple iPhone 7 and iPhone 7+ design.
In addition of that, slim skinny design of iPhone 7/7+ makes its micro soldering more fragile and iconnection breaks with small jerk in regular usage without any major accidents.
This weak micro soldering of Audio IC on Logic board resulted in hundreds of iPhone 7 stopped working mic.
You can find lots of cases, just google "iPhone 7 mic issue" or "Audio IC repair iPhone 7"
With the aging of iPhone (above year and half) weak connection between IC and logic board gets disconnected that lands these kind of problems.
Problems are Speaker button grey-out, slow boot, around 5-6 minutes to boot and iPhone works with Bluetooth device.
For live example check this video, this is typical example of defect and repair in this video.
iPhone 7 / Plus Audio IC U3101 Repair stuck on Apple Logo Slow Boot No Sound 338S00105 - YouTube
Just reballing of Audio IC solves this problem.
Now days micro soldering repair shops getting lots of iPhone 7 and iPhone 7+ these kind of cases.
This is iPhone 7/7+ signature design failure, which apple never accepted.
See this video
iPhone 7 Signature Failures--Error 4013/BB_PMU, Audio ic and the Fault Line - YouTube
As people having this kind of problem and consulted to Apple genius bar for solution. And surprisingly, Genius could not detect actual problem but land with conclusion that Dock connector is broken.
So need to swap the iphone 7 that costs 319$ + tax.
Actually broken C12 connection of Audio IC on Logic board lands with this issue but when Genius runs diagnosis of iPhone that gives result like "Could not detect Dock connector".
But actually dock connector is working perfectly fine as it charges the iPhone and also communicate with iTunes using lightning cable. So their diagnosis process is not capable or apple want to hide this defect with false results.
Actually Apple is not a customer friendly company anymore.
So better is, Do not to wait for solution or free repair campaign from apple.
Just go to repair shop who repairs with micro soldering and get your iPhone fixed in 30 mins.
ebay also have many mail repair service available.
And last thing Think twice thrice before purchasing costly iPhone.......