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How to solder

Soldering is an intimidating skill, but it can be learned. And with some practice, it’s not difficult to learn how to solder.

I’m not a professional. A lot of people are surprised to hear I’ve ever had to solder on anything computer-related, since many people my age haven’t. In spite of the disadvantages, I learned how to do it. If I can solder things that will hold together and conduct electricity, you can too.

Here are some tricks and tips, most of which I’ve learned the hard way.

Even though most of us rarely went there, it’s much harder to get good soldering supplies since the demise of Radio Shack. Some of the things that make your life easier aren’t available at a hardware store, so I’ve provided links to good supplies when possible.

Enough apologies. Let’s talk about what you need.

1. Pick the right iron. If you’re soldering electronics, a 300-watt gun is not only overkill, it’s highly likely to damage the electronic components you’re soldering. So use a 15, 25 or 30-watt iron to solder electronics. On the other hand, if you’re soldering wire leads to model train track, you’ll want a heavier gun (though perhaps not 300 watts). You’ll quickly grow frustrated trying to do that job with a 25W iron.

2. Pick the right solder. Reducing exposure to lead is commendable, but having worked with lead-free solders, I can tell you it’s very difficult. The ideal solder to use is a low melting point 63/37 solder. You may be able to find a 63/37 blend at a hardware store for less and that would be fine to use, but I recommend you get the thinnest you can find. When soldering electrical circuits, I find the thinner solder melts and flows much more easily.

If all you can find locally is 60/40 solder, that works and is easier to work with than lead-free solder, but 63/37 is easier.

3. Use flux. You can get flux at your hardware store or  online, and you’ll always find the flux in the same part of the store as the solder and other soldering materials. If there aren’t Geneva Convention regulations against forcing someone to solder without flux, there should be. Try it once and you’ll see I’m not kidding. Get the right type, probably electrical solder in this case.

4. Clean and tin your soldering iron tip. I really miss Radio Shack tip tinner and cleaner (part# 64-020). The closest stuff I’ve found is soldering tip refresher. Far and away the easiest way to clean and tin your soldering iron’s tip is to let it heat up, then plunge it into a tin of I wish someone had told me about this stuff years ago because it makes a world of difference. “Tinning” is the practice of applying a small amount of solder to the tip of your iron. The presence of that solder on the tip makes the solder flow more easily. In a pinch, you can tin your iron by applying the tip to your spool of solder, but using the Radio Shack product is easier and more effective because it also cleans the tip.

So, that’s what you need for your shopping list. Now let’s talk about process.

1. Get safe and comfortable. If you’re not comfortable, you’re more prone to make mistakes. The iron gets extremely hot, so you don’t want to slip and touch it. Move anything out of the way that might be damaged by the iron, or might get in your way. Open a window and, if at all possible, put a fan in it. Don’t stand right over the joint you’re soldering, because the fumes from the soldering process will irritate your eyes, lungs, and respiratory tract. And wear safety glasses. Most components are perfectly safe to solder, but there’s never, ever a reason to take chances when your eyes are involved. I learned in Cub Scouts that you only get one set of eyes, and that was 30 years ago, but it’s still true.

Also, don’t solder in the kitchen, or anywhere near where food preparation takes place. Lead poisoning is no joke.

2. Plug in your iron and let it heat up. Enough said.

3. While you’re waiting for your iron to heat up, clean the solder. Take a paper towel, dab a bit of 91% isopropyl alcohol (available at any drug store) onto it, unroll a length of solder, and wipe the paper towel on it until you can do so without the towel getting dirty. This removes surface impurities from the solder. This trick is optional, but it really helps.

4. Prepare the components you’re going to solder. If they aren’t new out of the package, clean the components with a pencil eraser. If they’re new out of the package, clean them with alcohol to remove any impurities that may remain from the manufacturing process. Next, put the parts together and do your best to make a strong mechanical connection between them. When soldering two wires, I twist the wires together beforehand. When soldering a wire to a component, I wrap the wire around the lead on the component. Once you’ve made your mechanical connection, clean it again with alcohol to remove your oils and fingerprints.

5. Apply flux. Once you have the best mechanical connection you can get, apply a small bit of flux to the joint using a toothpick. The flux removes impurities from the metal surfaces and helps the solder to flow much more easily. It’s usually possible to solder without flux, but you won’t like doing it.

6. Tin the iron. At this point, the iron probably is hot enough. To find out, plunge the tip into the tin of tip tinner and cleaner. If it doesn’t melt like butter, the iron isn’t hot enough.

7. Apply the iron near the joint. The flux will immediately melt and vaporize. Then apply the solder to the joint. That’s right. Apply the soldering iron near the joint, and apply the solder to the joint. A common mistake is applying the solder to the iron. The iron’s job is to heat the joint hot enough that the joint can melt the solder. So apply the solder where you want the solder to go, and apply the tip of your iron next to it. Once the joint is hot enough to melt the solder, the solder will flow into the joint. Then you can remove the iron and the soldering spool.

8. Allow the joint to cool, then clean the joint with alcohol to remove any remaining flux. A good solder joint will be clean, smooth, and shiny. If it’s dull and grainy, it’s a cold joint, which may not work at all, and even if it does, won’t conduct as well as it should and is prone to cracking and failure. If you get what appears to be a cold joint, re-heat the area again and apply a small amount of additional solder.

9. Wash your hands. You’ve just been handling lead, and lead isn’t good for you. It won’t hurt you if you take the proper precautions, so wash your hands.

And that’s all there is to it. The only other secret is practice. The more you solder, the better you’ll get at it.

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