Soldering is a way to join electronic components by melting metal to join the parts, so that when it cools, your parts are strongly connected—both electronically and physically.
Soldering is sometimes avoided in school makerspaces because it seems too technical or perhaps unsafe. But soldering is a way to continue an iterative process of building circuits with more reliability and good visibility into how things are connected.
One of the most important engineering principles when building things with electronics is how reliable your physical and mechanical connections are in your circuit. The thrill of getting a circuit to work can be immediately undone when it fails in mysterious ways because the connections are weak. It also makes troubleshooting circuits more difficult when you constantly have to wonder if the components are even connected, much less doing what you expect.
As a metaphor, the solder builds a bridge at the atomic level for the electrons to walk across—those lazy electrons! When your parts are just touching, even if you hold them tightly, there is always a microscopic chasm for electrons to cross, and they won’t do it if they can avoid it. If you are teaching about electricity as movement of electrons, this reinforces your lesson. (Even if you aren’t there yet, you can just say that the electricity won’t jump across empty space, even spaces so small we can’t see them, and leave the atomic stuff for another day.)
There are a number of ways to make a circuit by putting the components in close physical proximity—wrapping wires as tightly as you can, tape, sticky copper tape, tightly sewing conductive thread, holding things together with your fingers, binder clips, alligator clips, etc. Those are all good ways to start, because they are immediate and easily changeable. But hopefully you don’t stop there—the next step is to build circuits that are more complex and/or more permanent. Breadboards are good for that, but introduce another way for things to fail—bad jumper wires, incorrect placement, knocking the parts loose by accident, etc. Anyone who has every tried to use a breadboard on a moving robot can testify that the connections are never permanent. And it’s also a level of abstraction that can confuse a beginner. I believe that soldering is much simpler and easier to learn than breadboarding.
Soldering is a skill that improves with practice—there are ways to make the joins better—and of course you can learn to not burn yourself and others. There are other skills for the teacher to learn and share—kinds of solder, different soldering irons, safety concerns, the mysteries of flux, and the joys of unsoldering. There are lots of good guides and videos available online to get started.
Soldering is useful for simple circuits, even just a few LEDs and wires can be joined quickly for a huge improvement in reliability. It also works for circuits with copper tape and (some) conductive thread (here’s a trick). Soldering does not require a printed circuit board. If you are building fun paper circuits, a simple next step once your circuit is working is to reinforce the places where the LEDs touch the copper tape with a bit of solder. The reward will be a much more reliable project that will last even when it’s taken home or put on display.
Using soldering as a solution to the problem of unreliable circuits teaches students that engineering is a continuing effort to solve the small problems as you make progress toward bigger goals. That means beginners absolutely SHOULD start off WITHOUT soldering so that they actually run into the problem and authentically need a solution.
If you are considering introducing students to soldering, know that all of this gets better and easier with practice, but the bottom line is that while we wait for someone to invent conductive superglue, soldering is the best way to create reliable circuits and successful electronic projects.
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