For hobbyists who want to create their own electronics from scratch, there comes a time in every project when two metal surfaces must merge. Solder, which changes from a flexible solid to a liquid, then back to a solid in seconds, is the magical metal glue that makes this happen.
Solder can also be a frustrating mess. For reasons both aesthetic and functional, you'll want to learn how to work with it cleanly and neatly, because sloppy soldering means your project might not work.
Tools of the Trade
Meet the Materials
Printed circuit boards (PCBs) connect together electronic components (capacitors, resistors, LEDs, microcontrollers, sockets, etc.). Solder gives those components structural and electrical footholds at the spots where they're mounted, called pads. It's important that these surfaces start out clean, so wipe the PCB with a nonabrasive scrubber.
The wires sticking out of components are called leads. Some parts, such as microcontrollers, come with rigid leads that align with the pads on the PCB, and others, such as resistors, come with longer leads that bend to fit. Some parts have one lead, some two, some 28 or more.
Add Components To the Board
To connect a component to the board, push its leads through holes in the pads—only one lead goes into each pad—and bend them about 45 degrees to keep the component from falling out. Next, hold the iron like you would a pencil and press it against the pad and lead for 1 second. Then push about 1 to 3 mm of solder between the lead and the pad, where it will melt against the heated components.
Hold the tip steady for another second or two so the solder has a chance to flow around the lead. It's key to heat the components themselves, not the solder directly, which can cause a cold joint; components that aren't hot enough won't bond to the solder properly, leaving the joint weak.
💡 Try not to let that metal flow onto your hands—not only is the solder hot, the lead is toxic. Wash your hands after soldering so you don't leave any residue on your skin.
A perfect connection will look like a small bump around the lead and will completely cover the pad. If some of the pad is still exposed or the connection is flat, you haven't used enough solder, and you may end up with an incomplete connection. The fix is simply to add more solder, but not too much—that could create a connection where you don't want one, shorting the circuit and directing electricity down the wrong path.
Cut the Leads
The last step is trimming the leads. If they remain too long, they may bend and touch each other, potentially causing a short circuit. Using a wire cutter, snip each lead just above the mound of solder. Hold on to the end of the lead to ensure you don't get speared in the eye by flying wire.
How To Join Two Wires
Don't Forget Clean Up
Because a soldering iron heats to almost 400 F, the tip oxidizes quickly, creating solder rust that blocks the flow of heat. So before soldering each connection, use a wet sponge to clean the tip of the iron (it's clean when it shines) to remove any buildup.
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