BACK TO BASICS Figure 10. Soldering irons are available with screw-in tips (shown here), as well as wedge-shaped and flat. for how to set the iron.) My iron uses a round screw-in tip (Figure 10). Some irons come with multiple tips, such as wedge-shaped, and flat but tapered. It’s a matter of personal preference. It’s a good idea to buy replacement tips when you get the iron. One of the cleaning processes involves sandpaper, and the tips eventually wear out. The stand for the iron does a little more than just hold a hot iron (Figure 11). You might think you don’t need one, but you don’t want to lay a hot iron on a table, even if the tip doesn’t touch anything. If you’re not paying attention when you reach for it, you’ll find there are few things more painful than grabbing the wrong end of a hot solder- ing iron. The stand prevents that. The other important part is the small sponge you see below the iron holder. This is dampened with water prior to use. When you pull the iron out for use, pass it lightly Figure 11. Besides holding a hot iron, a stand also helps keep you from grabbing the wrong end of the iron. over the sponge to clean it. The sponge, be- ing cooler than the iron, thermal shocks the tip and helps remove any excess solder that might be sticking to the tip. This is some- thing you’ll do every time you start to solder. Figure 12 shows the open can of flux. You’ll notice the flux looks like it has holes poked in it. This is from dipping the tip of the iron into the can. Some stands have a flux well, which you can fill and dip into. As I said before, flux helps heat transfer from the iron to the joint, and also isolates it from oxidants in the air. It’s also good practice to put a dab of flux on whatever you’re soldering before you heat it. This isn’t always practical, but it’s something to keep in mind. Flux tends to act and feel like grease, so you’ll want to keep something around to wipe your hands from time to time. Also, remove the flux from the joint aſter it’s com- plete, if you can. This is especially true on Rules for Soldering Wear eye protection. Solder is a molten liquid metal that can splash and hit you in the eye. It’s not likely, but do you really want to know what it feels like? Don’t rub your eyes either, as flux is like grease and tends to get spread around. Never work on a live circuit. Cut the power or unplug it. Keep the iron and the joint clean. Impurities in the joint can hinder current flow and cause the joint to fail. Use heat sinks near sensitive components. Don’t apply heat any longer than necessary. Heat the joint until the parts, not the iron, melt and flow the solder. Don’t move the joint until the solder solidifies. Figure 12. The appearance of holes poked in the flux is the result of dipping the iron’s tip into the can. circuit boards, because you’ll notice it liq- uefies when enough heat is applied. A little alcohol is usually all you need to clean it up. Look back at the solder in Figure 3. This is the most basic thing besides the iron that you need to solder. Remember, keep things clean. The rosin flux in this solder and the canned flux you’ll use tend to get on the solder as you work. Normally you want flux on the joint, but not dirty flux, so it’s good practice to wipe the solder off with alcohol as you use it. Next issue, I’ll go into the rest of the tools us joints. Wiersielis, CPL, CFDI, ore than a quarter y of experience, hav- rked in most phases e trade throughout the ork metropolitan area. WWW.ALOA.ORG MAY 2014 KEYNOTES 53
