Soldering Safety

If you are working on an electronics project, you are probably soldering. Soldering can be dangerous: solder produces toxic fumes, your soldering iron is extremely hot, the solder gets very hot as well, and you may get air pockets or impurities that can pop as you heat the solder, sending molten solder flying unexpectedly and unpredictably. Because of these potential hazards, you need to follow some rules while soldering.

1) Wear goggles to protect your eyes. You must be careful when you trim leads or solder dross because a flyaway could injure you and others working in the vici

nity.

2) Never inhale fumes while soldering. Always work in a well-ventilated space, preferably with a fume extractor.

3) You must return the soldering iron to its stand (if you have a soldering station, it will be built-in) when you are not using it — do not leave it sitting on your workbench for any amount of time. The soldering iron tip is around four hundred degrees Celsius, so be careful; avoid touching wire insulation, plastic, and all other nearby flammable materials with the soldering iron. If you won’t be using the soldering iron for a few minutes, switch the soldering station to standby or turn off your soldering iron. Once you have finished soldering, turn off the unit and/or unplug it.

4) Another important way to avoid nasty burns is to use helping hands, clamps, pliers, tweezers, or a circuit board vice to hold your components. Ensure that your arms and legs are covered to avoid being burned by splashed solder.

5) Keep food and drink away from the working area. Traditional solder is a tin/lead alloy, and the lead is toxic. Flux is used to help metal pieces stay soldered together, and it is both acidic and toxic: flux will damage clothing and cause acid burns to your skin which, if they occur, you should immediately flush with water. If you spill any flux, clean it up immediately. Be sure to wash your hands after soldering.

6) Always thoroughly wash your hands after you have handled flux or leaded solder. Use lead-free solder — if you can — to reduce potential hazards.

7) After you’ve finished soldering, completely clean the area and discard any leftover lead and silver solder as well as dross in a lidded container, and then label the container (e.g. “Solder Waste”). Contaminated rags and solder sponges should be discarded as hazardous waste.

LEAD-FREE SOLDER: CHARACTERISTICS AND DIFFERENCES

The Restriction of Hazardous Substances Directive (RoHS), adopted by the European Union in 2003, changed the world of electronics manufacturing forever — especially with regard to solder. The lead-free solder necessary for RoHS compliance presents a set of unique challenges to PCB-manufacturing businesses.

While no one is disputing the fact that lead-free solder is less hazardous to those working in PCB assembly, working with unleaded solder has its complications. Lead-free solder doesn’t flow as easily as traditional leaded solder and, compared to a PCB using leaded solder, the soldered joints on a circuit board using lead-free solder will look noticeably different. You’ll also notice a dearth of top fill on through-plated PCBs (you’ll seldom get more than a seventy-five percent fill). In addition you’ll notice that unleaded solder joints are less shiny than joints using traditional solder because of the differences between the alloys.

It’s important to note that lead-free solder melts at a higher temperature than leaded solder. The exact melting temperature depends on the particular unleaded alloy you choose. A common mixture is ninety-nine percent tin, point seven percent copper, and point three percent silver; this alloy will melt and flow pretty well at two hundred seventy-five degrees.

Replacing and Modifying Equipment

There’s a good chance that the majority of your existing soldering equipment will need modification or replacement for lead-free soldering. You will at least need to replace your soldering irons’ tips — to avoid possible contamination issues — or you may need to replace your soldering irons and soldering stations altogether if they can’t reach the higher temperatures required for melting unleaded solder. Larger soldering equipment (e.g., wave soldering machines) will likely need to have their soldering baths replaced and you should consider replacing your flux as well because the PCBs you’ll be soldering will be lead-free, too.

With regard to solder pots and other types of hand-operated soldering equipment, you can either replace their baths or you could empty the equipment of solder, clean the bath, and coat it with oxide paint, which will save you some money; once the oxide paint has dried you can go ahead and fill your bath with lead-free solder and you’ll be ready to begin soldering again. While transitioning from traditional solder to unleaded solder can seem like a hassle, it’s rather easy and requires minor adaptation.