Soldering 101

As with other skills, becoming adept at soldering takes time and practice. Good technique will enable you to progress much faster than trial and error. Use the following technique to learn to solder the right way and you’ll find yourself proficient in no time. If you are a complete novice you should start on inexpensive and relatively unimportant projects.

The first step is to prepare the joint. Do not hold the wire with your fingers — you’ll have to figure out a way to hold the wire you’ll be soldering in position without your fingers. Some options are to loop the wire through the solder lug so that it stays in place, taping the wire down, laying a tool (such as pliers) on the wire, or using a mechanical soldering accessory to keep the wire in place. You can use just about anything, except your fingers, to secure the wire.

If you attempt to solder a joint and rely on your fingers to steady the wire as the joint cools you will inevitably fail; you need the wire to be completely motionless as it cools, because the solder will fracture internally if there is any movement at all, and no one has hands steady enough to accomplish this.

You’ll want to use a good soldering iron, the tip of which you need to keep clean. You can use a damp sponge for keeping the tip clean, which is why almost every soldering station includes a sponge. Solder creates dross — a mass of solid impurities — rather rapidly and dross buildup on the tip of your soldering iron will prevent proper heat conduction and introduce waste to your solder joints.

Before you bring your soldering iron to the joint you should tin the tip of your soldering iron with fresh solder. Completely coating the tip with solder will improve heat conduction. Remember to shake off any excess solder after tinning the tip: you want the tip of the soldering iron coated all the way, but you don’t want it dripping with solder. You can knock excess solder into any fire-resistant container (such as a tin can). While it is very unlikely that you’ll start a fire with solder, given its low melting temperature, be attentive and cautious with regard to molten solder.

After removing excess solder from the soldering iron tip immediately apply it to the joint, i.e. to the wire and the solder lug, the wire and the potentiometer … whatever it is you’re soldering. Dross will accumulate quickly so it’s important that you start soldering as soon as the tip is ready.

You’ll heat the joint rather than the solder; you want the joint to be hot enough to melt the solder. If the joint is hot enough to melt the solder you’ll be able to feed solder into the joint without touching the soldering iron and then the solder will melt and be drawn to the joint. You’ll actually see the solder wick out onto the soldering surface, which is ideal. When you solder a ring-shaped solder lug, for example, you should completely fill the lug with solder, thus ensuring maximum mechanical strength.

Remove your soldering iron from the joint as soon as the solder wicks to the joint. While the majority of electronic components can withstand a considerable amount of heat, some are can’t stand the heat for long — so don’t test your luck. Once you’ve soldered the joint, remove the soldering iron and allow the joint to cool, and make sure that the components remain totally motionless.

George

George Leger has a Masters in Electrical Engineering from Stanford University, worked in private industry pioneering surface-mount technology and in government research labs for twenty years, published several papers on surface-mount technology, co-authored papers published in national symposiums on accelerator technology, was past president of SMTA and an adjunct professor at the community college level, holds a patent, and is a certified microchip design partner, serving as a consultant to many companies developing electronic circuits.

Leave a Reply