Common Soldering Mistakes

Learn about the most common soldering mistakes from expert Jeff Koskulics in this Howcast video.

I have here two different pieces of copper that are from a standard [inaudible 00:09] power supply. One common soldering job might be to put a connector on something like this.

This piece of wire has been stripped and sitting out in the air for a long time and I wanted you to see how it looks when compared with something that’s just recently stripped. And holding them side by side, you can see that the one in my right hand is much, much cleaner and shinier. It has a pinkish appearance of nice, clean copper whereas, the one on the left not as copper colored.

The copper that has been exposed to air for a long times forms an oxide layer on its surface and that oxide layer tends to disrupt the alloying process of soldering. So it’s important to be able to get rid of that oxide layer before you begin soldering.

There are two ways to do that. The first is to mechanically remove it. You can do that by using sand paper to abrade away the oxide. And the other way is to chemically remove it and for that, we would use our rosin core.

So let me show you how it looks when we tin solder to the clean copper wire. Begin by adding some rosin, placing it in our vice, and heating it with our iron. See the smoke forming as the flux burns off and we have a nicely tinned piece of copper.

Now, if we try to do the same process with the oxidized copper, we’re going to run into trouble. Add our flux. Okay, here we go. Now, as we heat the joint see that our solder is still tries to find its way in there. It doesn’t make quite the same contact that we had with the other. Just for comparison, I’ll hold them side by side. You see little bits of brown left over? That’s copper that hasn’t been properly soldered and the reason for that is the oxides that have formed on its surface tend to disrupt that alloying process. So in order to make a better solder joint, what we need to do is we need to remove that oxide layer.

What we’ll do is we’ll cut a new piece of wire. Strip and use our sand paper. Twisting the wire. Adding our flux. Applying heat and our solder wicks its way between the wires for a nice, clean tinned copper wire. And there you have it.