Essential Soldering Equipment

Matti Airas was asked about soldering irons in the #sensors channel on Discord (join the Signal K Discord here). Here’s what he had to say.

This is my opinionated list of recommendations for getting decent electronics/wire soldering equipment without breaking the bank. The essentials are small enough to easily store on the boat and shouldn’t cost much more than 100 EUR/USD or so.

The text below is in a rough order of importance. At the very minimum, you should get at least a soldering iron and tips, some solder, flux and brass wool.

Soldering iron

The recent USB-powered soldering irons are very compact, powerful and easy to use. I recently bought a FNIRSI HS01 for boat use. My initial impressions are very good: it’s very fast to heat up, comfy to hold and is able to provide plenty of heat for thick wires or large ground planes. The downside is that it apparently only works well with its own tips. If you go with it, be sure to get a tip assortment as well.

Another good option for people in North America is Pinecil. A lot of people rave about their products. Super cheap in the US as well.

The USB-powered irons require a decent USB PD power supply and some proper USB PD cable. A really good 12V supply might do, but the cheap, slow ones definitely not. I’m prepared to use the inverter and a mains powered supply for soldering on the boat.

Soldering iron tip

I have learned to like knife-style tips a lot. They work great for both thick wires, through-hole components as well as more finicky surface-mount components, depending on how you hold the tip. They come Chisel tips are ok as well, but conical tips - I don’t really understand how you can do anything with them. The flat screwdriver type tips are probably great if you’re a plumber or something.

Solder

Solder is another crucial component. In the EU, leaded solder is outlawed for professional use. Lead-free solders have a slightly higher melting point and have a reputation of being more difficult to use. I’ve been a good citizen and have only used lead-free solder for all purposes for some time and have had no problems. Pretty much all solders are flux-core, meaning that they contain flux. (More on flux later.) If you decide to use leaded solder, get 63/37 (63% tin, 37% lead). For lead-free, SN100C is apparently a good formulation. I just checked; it’s very close to the roll at my desk and what I have no problem with. One major difference with leaded and lead-free solder is that the lead-free solder fumes are considerably more harmful than the leaded fumes. The fumes consist mostly of burnt flux. There’s no lead in leaded solder fumes, the temperature is not nearly high enough to vaporize any metal.

Flux

Flux is very very important. That’s an additive that reduces the surface tension of the solder and let’s it flow easier onto pads and into wires. A bit like dishwashing liquid and grease, except opposite. About 80% of the time you don’t need extra flux, the one that’s in your solder is enough. If you keep fudging with a joint enough or with a too hot iron, flux eventually burns away and the solder becomes “weird” and starts forming spikes and doesn’t flow any more. Usually adding a bit more solder will fix it. However, either for nasty surface-mount components or for thicker wires, adding extra flux helps a lot. A syringe is handy. There are lots of different types of flux. Both rosin or no-clean are fine. I don’t have strong preferences there.

Cleaning the iron

Keeping the soldering iron tip clean is essential for frustration-free soldering experience. A clean tip is shiny, an oxidized one is dull-colored or even charred. It’s totally frustrating to try to get anything done with an oxidized tip. Solder just tries to avoid the tip and won’t melt in the first place. On a shiny tip, things just work. After soldering a joint, add a bit of solder to the tip and wipe the tip on brass wool. I’ve learned that wiping works much better than stabbing. It also helps if you don’t keep the iron on for too long. Never touch any plastic with your good tip. Oh, and if you intend to carry the kit around, get a container with a lid. Otherwise the brass wool will shed solder dandruff everywhere.

For badly corroded tips, there are also soldering tip cleaners/refreshers/activators. You dunk the tip in them for a second and then wipe on the brass wool. And repeat a few times. They help but won’t do wonders. Never use sandpaper. The tips have a thin hard plating over a copper core. If the plating wears out anywhere, the copper core corrodes in no time and the tip is gone.

Light & Magnification

For those of us who are middle-aged, proper lighting helps a lot. At the desk, a magnifying glass table lamp is good for most of the stuff I do. (And it keeps the most of the solder fumes separated from your nose.) On the go, even a good headlamp goes a long way, but something like a head loupe is even better.

Solder wick

Other useful things: solder wick is helpful for removing excess solder and solder from old joints. Stripped wire end dunked in flux will also do in a pinch. A solder sucker (like a reverse syringe) is nice to have for removing solder from PCB holes and costs next to nothing.

Ventilaition

Finally, some ventilation. A small fan is usually enough, or even just blowing at the fumes if it’s a small thing.

Soldering mat

Finally finally, a silicone soldering pad is nice to protect your varnished tabletops.

Join the Signal K Discord channel and join the discussion about soldering equipment.