Nuts and Volts - February 2009

A guide to

soldering

BY JAMES L. ANTONAKOS

Finally, electronic components can simply be soldered together. Soldering involves heating up the metal leads of the components and then coating them with a different molten metal. This makes for both good electrical and mechanical connections, that ideally, will not come apart when the leads of the components are moved or vibrated.

A typical solder is an alloy made up of 60% lead and 40% tin; it is thus referred to as 60/40 solder. It comes on a roll in the form of a thin, flexible wire that is pushed into the area being heated to make it melt. Figure 1 shows the cross section of three different types of solder wire, all of which contain some internal resin or flux — a chemical used to clean and wet the metal surfaces.

There are many ways to connect electronic components together to form a working circuit. They can be wire-wrapped or their leads can be pushed into small metal springs popular with 100-in-one electronic kits available at RadioShack. The components can also be placed into small plastic cubes with metal tabs on each side and inserted into a two-dimensional grid to form a circuit, another hobbyist fabrication for fashioning your own electronic projects.

FIGURE 1. Cross section of three types of solder wire.

Let’s Begin

What do you need to begin soldering? First, you need something to solder. This may be as simple as a few wires that you want to tin or as complex as a radio or other electronic kit that does something interesting. Next, you need a soldering iron, some solder, and a small wet sponge. Figure 2 shows all these items. A soldering iron is essentially an electric heater. The tip of the soldering iron gets very hot. Placing the tip onto the wire leads of two components transfers heat to the leads. When the leads get hot enough, they will melt the solder that is applied to them. When the soldering iron is removed, the molten solder will slowly cool and harden, making a strong, highly conductive connection between the wire leads. As the solder melts, it gives off smoke. Hold your head back so the smoke does not get in your eyes — or lungs — as you work.

The small wet sponge is used to clean the tip of the soldering iron before it is used each time. The high heat of the tip causes it to rapidly oxidize, which reduces its ability to transfer heat. So, before you place the tip