How to Solder

The tools needed to solder are a soldering iron and a heat sink. A soldering iron is a tool that heats the solder to melt it. It is a long metal tube, with a sharp tip at one end, and a rubber handle at the other end. A heat sink is a metal clamp that is connected to protect a part (like a transistor, capacitor, light bulb) from getting damaged by the heat of the soldering iron. If the parts are being soldered into a circuit board, a pair of diagonal cutters is also needed. Diagonal cutters are designed to cut wires at an angle, so the end of the wire would be as short as possible. It is necessary to cut wires soldered to a circuit board short, or else they might bend and touch each other, causing current to flow between the wires. This is not good because it will cause the circuit to malfunction. Also needed is some 60/40 (60% lead, 40 % tin) rosin core solder. (The rosin core helps to clean the surface being soldered to.) Don't use acid core solder; it will corrode and ruin the connection.

To begin, first plug the soldering iron in, so that it can warm up before you use it. This takes about thirty seconds. Once it warms up, don't touch the metal part or else you will get burnt. Always remember to unplug it when you're finished using it. (I learned this the hard way. Once I forgot to unplug my soldering iron, and I left the house. When I returned, I picked it up by the metal part not knowing that it was on. The burn took a week to heal.) Make sure your work area is clear of flammable objects and things that can melt. Unroll some solder from the spool, but don't let it get close to the soldering iron, or it could melt. This would waste the solder, and it is expensive.

If you are going to solder two wires together, you must "tin" each wire first. To "tin" the wires place the hot soldering iron tip on the exposed wire to heat it, and then touch the end of the solder to the wire. It will melt and "flow" around the exposed wire. Remove the soldering iron, and allow the wire to cool. Do the same for the other wire(s). To connect the wires, place them so that the tinned ends touch, then heat the connection with the soldering iron. Add a little more solder to the connection while heating it, then let it cool. When finished, the solder connection should be smooth and uniform, with no dents, bumps, black dots, and exposed wire showing through the connection, ect. If it has any of these, you should heat the connection again until it melts, and let it cool. (I don't normally do this, but that is what my electronics instructor told me to do.)

For soldering parts (such as transistors, capacitors, miniature light bulbs) into a circuit board, first make sure that that the part is the correct one (you don't want to put a capacitor where a light bulb is supposed to go.), and that the holes that the part's leads (wires) go in to are the ones that it is supposed to. This is especially important for custom projects and circuits. Most kits are labeled for the builder. Put the part's leads in the holes, and then make sure that the part is in the right way. If it is not, chances are that it won't work. The part should be in straight, not crocked or leaning over to one side, but this is just for aesthetics and won't affect the operation of the project. Put the heat sink clamp on the lead that is to be soldered first, between the circuit board and the part. To solder it into place, hold the solder to one side of the foil "pad" around the hole, and the soldering iron to the other, and the solder will flow around the "pad." Allow it to cool. The solder should look something like a Hershey's kiss with a wire sticking out of the top, with no holes or dents, but I don't really care. If there is still some of the hole in the circuit board exposed, and you really want to, add more solder when reheating the connection. Next, move the heat to the next lead to be soldered, and repeat the procedure. After soldering all the leads, clip them off just above the solder with the diagonal cutters. (You don't have to do this, but it prevents your circuit from malfunctioning later.)

To solder wires to a circuit board, there are two options; solder it directly to the copper foil, or insert it through a hole like the other parts. Soldering directly is rarely done and considered unorthodox, but I still do it if I have to. To solder it directly, tin it and the foil on the circuit board. Next, hold the tinned wire to the tinned area of foil while applying heat with the soldering iron. Allow the solder connection to cool, and check it to make sure that it doesn't have any of the imperfections listed above. If you don't like how your connection looks, reheat it. It should still work, even it has imperfections. To solder it to the circuit board through a hole, just do the same as for a part lead. Tinning the wire is not necessary in this case.

When finished soldering, unplug the soldering iron and allow it to cool before putting it away. Be sure to wash your hands afterwards to avoid lead poisoning.