Soldering Issues with Pro Mini

I'm just seeking conformation that I've killed the I2c pins on my 3.3v pro mini =(

I've gone a changed the style of my pins numerous times as carefully as I can by desoldering old for new. Now, my solder wont stick to the board as the copper ring (I think its copper) seems to have just disintegrated. Is there any way I can rectify this or have I killed them both?

It's been a while since I've done this, but I used to fix such things by scraping off a bit of the solder mask over the trace coming from the pad, then carefully solder in a small jumper. You's need something like awg 30 or smaller wire. I used to use single stands from stranded wire, if it was the right size. The 'right size' is a combination of current capability (should not be an issue here) , handling and be small enough not to short to surrounding objects.

If you want to reuse a Mini, solder header pins into the holes, don't solder wires directly!

The pad lifting that you've seen is often a symptom of using a soldering iron that's too hot, or taking too long to solder, or repeated use of a spring-loaded desoldering tool (impact damage from the recoil).

Temperature controlled irons are not false economy IMO.

I made some bad decisions on my choice of pins. First I had normal pins but after realised the lid on my project box would not of fit by the time a dupoint cable was used. So I then changed them for some right angle header pins, then realised I needed the right angle header pins to point the other direction. Thats when things went belly up.

I use only a M12 Antex but was using a big desoldering tool which probably didn't help. I find using the right pins is a nightmare because once they are in they are hard work getting out!

You can find the schematics of your pro mini and other important information right here on this site. You can use that to know where a wire needs to go if you decide to fix it.


I’m not sure if I follow, solder to where? You mean tapping into one of the legs of the 328 chip?

I’ve looked at the schematics and it doesn’t make much sense, all’s I can see that is relevant to A4 & A5 is JP2

Well, the pro mini is just a power supply, a reset, a LED an oscillator and the controller. There's nothing more, and that's why the board it this small size. So you'd solder the wires to the controller i guess.

There is also a zip file to download, that holds the eagle files so you can have a peek at the copper traces. Maybe that can be of some help to you, to find a good spot to do your soldering.

Will do, thanks :)

Pro minis cost less than $4 on eBay.

Acceot that you over-cooked the PCB by using a soldering iron with too high a wattage, get a new pro mini... move on.

That is the rational and economic solution.
Still there is value in fixing this; one can practice their soldering skills and learn a bit about pcb’s.

Still there is value in fixing this; one can practice their soldering skills and learn a bit about pcb’s.

95% of the lesson has already been learned (hopefully).

You might be able to solder a wire onto a PCB track - find a suitable track and scrape the solder mask that covers it until you see metal. Those tracks are very fine though and lift off the PCB at the slightest overheat.

Soldering directly onto the chip? Also very difficult unless it’s a corner pin. You could try it with wire-wrapping wire or fine magnet wire.

Due to the size you may be able to get away with a solder bridge...