Maybe you just completed the etching of the circuit board in the project and everything looks very successful. But you also know that over time, the copper traces on the circuit board will slowly turn black and green. This article describes a simple method for tinning copper traces on a circuit board. If you have all the materials ready, it’s great!
After preparing the solder, flux, solder core, and flux cleaner, you can proceed to the next step. If your materials are incomplete, I will attach a parts list at the end of this article so you can prepare the relevant materials.
First apply solder flux to the bare board-be sure to apply a sufficient dose. A piece of solder is then applied to a strip of solder. As shown in the figure below, make sure that there is enough solder on the solder tape.
Then place the solder suction tape on the circuit board. Use a soldering iron to heat the soldering strip. When you see that the solder has melted on the soldering strip, gently “drag” the soldering strip on the trace. Repeat this operation on all traces. If you come across some small copper trace areas while dragging the suction strip, don’t worry, we will clean it in a later step.
The effect after completion is shown in the following figure. You can see that the surface of the circuit board is a bit rough, there are residual flux on it, and there are some areas where the solder strip is missing. It’s time to start cleaning. Apply enough flux again on the entire circuit board.
Cut off the end of the strip to continue using the remaining clean section. Place the soldering tape on the circuit board traces and heat the soldering tape with a soldering iron. When the solder begins to melt, gently “drag” the suction tape again. This removes excess solder, and if any areas are missing, drag the solder into those areas. The goal is to keep only a thin layer of solder on the board traces. Do this for the entire circuit board and apply some flux (if needed).
Next, clean the circuit board with some flux cleaner and a small cloth. Spray the flux cleaner on the cloth as shown in the figure below. While pressing the circuit board firmly, clean the circuit board in a circular manner with a damp cloth moistened with flux cleaner.
Then “polish” the board with a clean, dry cloth. Use a little force during this process so that the solder coating will be more shiny.
The effect of tinning and cleaning of the circuit board is shown below. (You can see that the rectangular welding plate in the middle sparkles after polishing).
With this thin layer of solder coating, the copper traces on your board will no longer turn green, and tinned copper traces will be easier to solder.
The products I like to use throughout the operation are as follows:
Kester’s 20AWG requires no solder cleaning: KE1400-ND
Chemtronics Flux Dispenser: CW8400-ND
Chemtronics Solder Removal Strip: CW10-25-ND
3M Novec Flux Cleaner: 3M155811-ND
If you already have other similar products, you can continue to use them.
For more technical information related to circuit design, see:
Removing through-hole components from double-sided boards
PCB milling tips
At a glance! Quickly estimate the copper wire resistance on the PCB surface
Keep your PCB away from moisture