Howto repair the microphone inside the bottom module

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As fairphone angel (in Berlin) I have a lot of support cases with nonfunctional microphones in the bottom modul. A lot of users have minimum the 2nd, often the 3rd bottom module. Mostly easily changed by Fairphone support in warranty.
But there is a lot of waste (I collect old faulty modules and send them back for recycling).

So my questions:

  1. Did anyone successfully repaired the microphone inside the bottom module by soldering a new smd microphone?
  2. What’s the reason for the highly rate of faulty microphones? I first expected just dirt inside the microphone (like a lot of faulty headphone jack problems are just dirt/lint stuck inside). But I opened some of the faulty bottom modules and everything seemed clean. So it’s just bad smd module with low quality?

My search results:

  1. I knew that @Leo_TheCrafter did his own (pcb) module.
  1. The user @userr tried this in the closed thread FP2 Bottom Module: Repair broken µUSB port but without feedback

OT: I opened this thread (at first as question), but in future it could be a wiki entry to collect all information about repairing the microphone


The thing is not only are the traces very fragile, the board also is very thin and tends to bend, this is noticible in the pad area, where it can deform, causing contact problems