5 Common Mistakes People Make When Soldering

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There are some people out there who might be a bit intimidated by the prospect of melting metal to create electrical joints, but soldering is an important skill to have if you want to work with electronics, and you can do it safely so long as you follow proper guidelines. There are also plenty of great soldering irons for beginners that can simplify the mechanics and make soldering much more approachable. Even so, it can be a tricky skill to master.

Sometimes soldering feels like a task that requires four hands, especially when you’re new to it and haven’t had much practice. Even when you do manage to solder components together, the connection might still not function as intended, and that’s often down to one of the several common mistakes that people make when soldering.

If you’re new to soldering, you’ll want to be aware of these mistakes so you can avoid making them. Conversely, those with more experience still may want to brush up on these to refine your technique and make sure your solder joints are as good as they can be.

Nearly every soldering iron you’re likely to encounter will have temperature control. Sure, you can get an ultra-cheap Harbor Freight iron that lacks this feature, but most decent ones will have a dial on the iron itself or a setting on the base that lets you adjust that setting. Either way, setting the appropriate temp for heating your solder is one of the most important steps when soldering.

When the iron is too hot, it can burn off protective flux and instantly oxidize the iron’s tip. It can also damage delicate components, such as the copper pads on a circuit board. Setting it too cold is also problematic, though. This results in cold solder joints that are dull, lumpy, and unreliable since they can crack and break easily. An iron that’s too cold will require you to hold it against the component for much longer, which can also cause damage.

Different kinds of solder will have different melting points, but a general rule is that most alloy solders will melt at around 360 to 370 degrees Fahrenheit. This isn’t the temperature you set your iron to, however; you usually want it to be around 660 to 750 degrees Fahrenheit. That said, you’ll need to play around with it a bit. Joint size, solder type, and material will all influence the temperature necessary to solder properly — and you’ll need to learn how to feel it out on a case-by-case basis. At the proper temperature, the solder should fully melt easily without anything burning.

If you’re trying to figure out how to solder on the fly, then you might think you’re supposed to press the solder onto the tip of the iron and then dab the solder-covered tip onto the joint. This method is incorrect for a couple of reasons. The first is that it creates a cold solder joint. The components you’re applying the solder to are cold when you attempt to attach them this way, and the solder cools much too rapidly on contact and can’t form a proper bond. 

These issues are similar to using an iron that’s too cool. The solder doesn’t flow properly, won’t bond well to the components, and the joint can crack and break easily. Another reason this is problematic is that liquid solder that’s beaded on the tip of an iron isn’t likely to spread evenly. You can also easily nudge components out of alignment as you attempt to get the solder off the iron and onto the joint.

When soldering, you should press the iron against the point where the components make contact, heating them until they are hot enough to melt the solder. Once these have reached a sufficient temperature, you press the solder directly against the joint, where it should melt on contact and seal the joint.

One of the biggest mistakes you can make when preparing to solder is failing to clean and tin the iron. Dust, dirt, and carbon can all build up and insulate the tip, preventing heat distribution. This means you need to clean both the soldering iron and the components you plan to solder before making a joint. The dust that builds up on components you’re soldering can also serve as a barrier that stops the solder from forming a proper bond. This weakens the bond and can reduce the joint’s conductive qualities.

Wires and circuit boards can easily be cleaned with isopropyl alcohol and a lint-free cloth. Simply wipe them down, and then give them a minute or so to dry. The soldering iron’s tip is generally cleaned while the iron is hot. One of the best methods is to use a brass sponge that’s soft enough not to scratch the tip but coarse enough to remove any build-up. A cellulose sponge that’s been dampened with distilled water can also work.

Once the tip is clean, you’ll want to tin it before soldering your next joint. This is the act of adding a small amount of solder directly to the iron’s tip. This is just a small amount that fills in the gaps, improving heat transfer and serving as a small protective layer that stops the tip from getting scratched or oxidized.

It’s possible to perform a perfect solder with one of the best soldering irons for electronics, only to mess up the joint right at the end. Solder cools pretty quickly, but it doesn’t solidify immediately. It takes time for the ambient air to cool the components being joined and for the solder that is adhering them together to become completely solid. Moving the joint too quickly can cause it to come apart.

There might not be obvious damage, but it may still loosen the solder’s hold, resulting in a much less effective joint. Even accidentally bumping a circuit board or brushing a wire with your hand before it’s completely fixed can disturb the joint. One of the biggest ways to avoid this is to make sure the components are fixed in place when you solder them. You can pick up something like the ZYRELYNX Silicone Soldering Stand or NOEVSBIG Helping Hands Adjustable Third Hand Soldering Holder to hold the components in place during and after soldering.  

Cooling times can vary, but they usually don’t take long. For some joints, 10 seconds is usually plenty of time. That said, you may need to wait as long as 20 seconds for larger surface-mounted resistors and capacitors to completely cool. You’ll see solder harden and turn gray very quickly, but it’s usually worth giving the interior a bit of extra time to harden just to be sure.

Another easy mistake involves the choice of solder for your projects. There is a wide variety of types, although most fall into one of three categories: electrical solder, plumbing solder, or jewelry solder. As you might imagine, electrical solder favors conductivity, while plumbing and jewelry solder are designed more for sheer tensile strength.

But even among these categories, there are several subtypes. You may come across, for example, lead-based solder, lead-free solder, rosin-core solder, acid-core solder, flux-core solder, and silver-alloy solder. Each is designed for specific kinds of joints and has different strengths and weaknesses. Leaded solder is often considered to have superior bonding strength, while lead-free solder has fewer health risks (if potentially worse reliability). It’s worth noting that different kinds of solder might have different melting points, so some will require more heat than others. Soldier can also come in different thicknesses, which can affect the amount of material that is melted on contact.

There isn’t really a one-size-fits-all solution for choosing the right kind of solder. Tin-lead solder is considered the industry standard for electronics, while lead-free solder offers a more health-conscious alternative. That said, you’ll want to research your specific project to find the best kind of solder for your needs.