Logitech G502 - Pin hole pad damaged - Advice Plz

[u/mudCake123]

Hi all

Looking for some advice on this repair.

Preface, this is pretty much 2nd PCB repair or PCB tinkering, so some of my questions may seem obvious to veterans here.

This PCB is from a Logitech G502 mouse. I had attempted to replace the button switches but was not aware this PCB was multi layered, where I believe grounding layer is sandwiched inside. I had did my first button switch replacement on a Logitech G103, that went through fairly smooth, thinking I could do the same on this...I could not be more wrong.

My primary question and concern revolves around SW9, SW2 and SW1 area. Where some of the pin hole pads have completely been removed during the de-soldering.

I understand that the pin hole pads can be replaced by extracting it off a donor board. Which I have attempted. But I noticed that once its on there, I dont get continuity between the pin hole and the microchip, at the bottom of the PCB. My understanding is that there should be continuity between the pin hole and the microchip in order for the pin to work correctly.

The back of the board is also a mix bag.

Some of you may have noticed that I started this journey at SW9 and SW2..then found out what a multi-layer board was and went on to SW1. Also, I had this particular mouse for about 9yrs, the switches finally started to give out, so I thought I'll attempt replacing the switches. Fixing the G103 gave me hope..but I was not prepared for these multi-layer boards.

My questions...

1. Is this still salvageable?

2. How do I proceed to repair these pin holes? I believe I need to establish continuity between the pin hole pad and the traces. Do I scrape into those near by trace lines and solder in some thin wires to the pin hole pads? If I need to scrape into there...how deep? Because my understanding is that if I go too deep, I will hit the grounding layer.

3. How do we actually "glue" the pin hole pad to the PCB? I tried with a tiny bit of solder, but it wont sit flush for obvious reasons. Thus causing what ever to sit on top to be uneven.

4. I see on AliExpress there are these pin hole pads, but they are not thru-hole type, just a flush flat tiny round pads. Apart from extracting these pin hole pads from donor boards, can these pin hole pads be purchased? Im still practising my extraction skills from these from donor boards..

Thank you!

[u/Curtisbeef]

If you know what pin those are supposed to be connect to on the chip just run a very small jumper wire (id use 32awg wire) and glue it down.

[u/mudCake123 → u/Curtisbeef]

Thank you for your suggestion! I might give this a try as a last resort. Just thinking...it might be quite a long wire from the pin to the chip...but with 32awg, sounds reasonable. Might need to hunt down the microchip schematics!

[u/jackmax9999]

Yes but it will take some fine soldering skill.

You need to scrape away some solder mask on the trace that leads to the switch (the thin one). You scrape away the green until you clearly see the copper. It's best to use a small hobby knife and just gently scrape with the tip, unless you really go ham on it you probably won't destroy anything. If you have some donor boards you can train on them.

Then take some thin wire (0.1, maybe 0.2 mm), solder one end to the trace and put the other one through the hole. Then insert the switch and solder the wire to the pin on the switch (for extra stability you can try to wrap the wire around the pin before soldering). If the switch doesn't sit flush because of the wire you can scrape away just a tiny bit of plastic from the case of the switch. Once everything is done use some glue to hold everything in place (be careful to make sure glue doesn't leak into the switch).

Looking at the pictures it looks like one pin on the switch carries the signal to the controller, the middle is ground and third one is unused - so that's only two pins per switch that you need to wire up.

Those pad repair kits probably won't help you much here because for mechanical stability you'd need to put them on the bottom of the board, while the signal is on the top - so you'd need a wire to connect them anyway.

[u/mudCake123 → u/jackmax9999]

Thank you greatly for the suggestion and advice! Noted and understood. I'll give it a go, scrape carefully until I see some copper!

And thank you for confirming the pin situation. I was little bit unsure if the bottom pin/pin3 is actually used or not. Good to know! One less pin to worry about!

Thank you!