I just got a cheap wireless phone charger from ebay, and noticed it making a very distinct high frequency squeaking noice. Here is how i fixed it, or made it almost inaudible. (Didn’t take any pictures, sorry)
Tldr; Basically open it and glue the coils down.
(15W Qi Fast Wireless Charger Stand 4in1 For iWatch 6/5/4/3/2/1 iPhone 11 XS XR 8)
Inside the main unit is a circuitboard, and inside the wireless unit there is two coils for QI charging and a circuit board for, and the watch charger.
Theory here should apply for any squeaking wireless charger really.
The coils that are causing trouble here are the two QI coils. I assume since they are charging via inductive coupling, and that they are not either tuned properly or glued down properly, that this is the reason for the audible sound.
Overly simplified, Inductive coupling works by an alternating current being sent trough the active coil. The magnetic field created will cause current to flow in the receiving coil in your phone and voila, battery charges.
The magnetic field created will, as it seems be able to make the coils vibrate, and in this case make a very annoying high pitch sound. Qi specs says that the frequency of the ac in the coils should be somewhere between 80 – 300 kHz. That is well above the human ears capabilities which stops at 20kHz. So why this happens I cant explain.
To open it up you dont really need to open the base (six screws under the rubber pads, in case you want to anyway). The front cover of the charging unit should come off without. Its clipped in place around the edges. Clips are pretty strong, and be careful around the watch charger cause the electronics are pretty exposed there.
The coils are glued to a ferrite sheet, to provide magnetic shielding. I cracked mine trying to pry it off, but it didnt seem to cause a problem. However heating it quite a bit with a hot air gun would not be a bad idea. There is double sided tape on the back of it so it will stay ish together anyway tho.
The ferrite sheet is fastened to the back with two foam spacers. Just leave them in there, fill the thing with the glue of your choice. Silicone, construction adhesive, epoxy putty or similar. I had to use hot snot cause it was the only thing available to me, but that gives awful working time.
Next fill glue on topp of the coils, and clip the cover back on. Let the glue set and youre good to go.
Put a bit of tape over the hole for the stand thing, and maybe cover the glue surface on the cover with tape so there is the remote chance of getting it apart again should you ever want to.
Mine still makes audible sound, but just ever so slightly.
Ill might still replace it at some point, but for now it does the job.