You just got done etching the circuit board for your project, and it looks great. However you know that after time, the copper will slowly darken and green up. This post will show you an uncomplicated way to tin the copper on the board. The best part is you probably have everything you need!
If you have solder, flux, solder wick, and flux remover you are ready to proceed. If not I will have a list of parts at the end of the post to get you started. The first step is to apply solder flux to the bare board. Be sure to apply plenty of flux. Next you will apply some solder to a piece of desoldering braid. Make sure you get a generous amount of solder in the braid as seen in the picture below.
Now take the desoldering braid and lay it on the circuit board. Apply heat to the braid with the soldering iron and gently “drag” the braid on the traces when you see the solder has melted in the braid. Proceed to do this on all the traces. If you have some small areas of copper showing as you drag the braid around, this is not an issue, as we will clean those areas up in a later step.
When the board is done, it will look like this. As you can see it is a little rough with the left-over flux still on the board and there are a couple spots that were missed with the desoldering braid. Now we are going to start cleaning up our work. Apply a liberal amount of flux to the entire board again.
Cut the end of the desoldering braid back so you have a clean, fresh piece to work with. Place the braid on the circuit trace and heat the braid with the soldering iron. You will notice the solder staring to melt and at that point start “dragging” the desoldering braid around gently again. This will remove any excess solder, and if any spots have been missed you will drag solder to those areas. The goal is to only have a very thin layer of solder on the circuit traces. Do this to the entire board and re-apply flux if need be.
The next step is to clean the board up with some flux cleaner and a small piece of cloth. Apply flux cleaner to the cloth as shown below. With the flux cleaner wetted cloth, apply pressure and clean in a circular motion while pressing firmly on the circuit board.
Next, with a clean dry cloth “buff” the board up. Use some pressure on the cloth when you do this. This will add a nice luster to the solder coating.
When the board is all cleaned up and tinned it will appear like this. (Notice the nice sparkle on the center rectangular pads after the buffing).
With the thin coat of solder, the copper traces on your board will no longer turn green. Also, it will be much easier to solder since the copper itself is now tinned.
The products I favor to use for this are the following:
20AWG No-Clean solder from Kester: KE1400-ND
Chemtronics Flux Dispensing Pen: CW8400-ND
Chemtronics Solder Removal Braid: CW10-25-ND
3M Novec Flux Remover: 3M155811-ND
But if you already have similar product on the bench, you’re set to go.