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How to Use a Soldering Iron: A Beginner’s Guide

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One art form that geeks really appreciate is soldering, but not all of us know the proper technique. It’s an easy skill to add to your geek resume, so let’s learn how and some old projects off the shelf.

(Image credit: oskay)

What Is Soldering?

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(Image credit: Public Domain Photos)

A soldering iron is a tool with a metal tip that gets really hot. We’re talking like 800 degree Fahrenheit, though you can adjust the temperature on a good iron. Its job is to transfer heat to things like wires, transistor leads, and pads on PCBs. After the appropriate areas are heated properly, solder is applied. If you plan on soldering, then you’re better off spending $30-$40 on a 20-30 Watt iron instead of on a cheap $15 one. You’ll get a longer-lasting tool that will work for a much wider variety of applications and you’ll get proper heat control to boot. There are also soldering guns available, but you should only use these when repairing thick cables and never on PCBs, as the tips have a live voltage running through them that can damage sensitive electronics.

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(Image credit: Public Domain Photos)

Solder is a thin tube, usually rolled in spools, made of various metal alloys. Its job is to hold the individual components together. The individual components and their quantities can vary, but for computer electronics, you’re usually looking at a 60% tin and 40% lead. Lead-free solder is also available, though it has higher melting temperatures and less “wettability,” meaning you may need a better soldering iron to use it and removing it can be more tedious. Lead-free solder is better for the environment and has other benefits, and they function more or less the same way.

The inside of the tube is filled with “flux,” a substance that gets rid of oxidation and helps clean the surfaces involved in the fusing process. For electronic use, you want rosin-core/rosin-flux solder. Acid-flux is used in plumbing and the acid can damage the sensitive components on PCBs.

Safety First!

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(Image credit: intherough)

Many who’ve never used a soldering iron are afraid of damaging equipment, but more important is the danger to yourself! Soldering irons get really hot (think, and solder itself is molten metal. Be sure to wear safety glasses, keep loose clothing and hair out of the way, and be careful with your fingers. Better still, use protective gloves. Solder can contain lead, so be sure to wash your hands thoroughly after handling it. It’s also really important to work in a well-ventilated area because the fumes from the rosin can cause damage to your lungs when inhaled. Honestly, it’s more common sense and preparation than anything. Just take proper precautions and you’ll be fine.

Cleaning and Tinning the Tip

tip and sponge

(Image credit: Mae Labs)

In order to conduct heat properly, your soldering iron needs to be free of any old solder. After being exposed to air, it oxidizes and thus insulates against heat. We want heat to conduct so that we can apply everything quickly and efficiently. A dirty tip means that you’ll have to hold the iron on longer and risk heat damage to the PCB, and nobody wants that. Keep a wet sponge handy, and after the soldering iron is fully heated, softly scrape it against the sponge to remove old solder. The tip should be nice and shiny, or at least very close to it.

Next, we’re going to “tin” the tip. This will protect the tip and allow heat to conduct better via the presence of new solder. On the hot iron, carefully apply a small amount of fresh solder and coat the tip. It should still be shiny if you’ve done it right. As soon as you tin the tip you should start soldering your components together. After every few joins, clean and re-tin, and again before putting your iron away into storage. This will really help increase the longevity of your tool. A good soldering iron should easily last years this way.

Joining Parts

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(Image credit: Soldering Is Easy Comic Book)

Hold the iron in your dominant hand and a long piece of solder in your other hand. When soldering two components together, you want to touch the area where they join with the soldering iron. Hold it there for about a second, then slide the solder underneath the tip of the iron, sandwiching it to the PCB (refer to above image, cursor points to solder). Hold it for another second or two, feeding in how much solder you need. This amount will vary depending on the project, application, and diameter of the solder, so check your instructions and study the pictures to get a good idea of the end result.

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(Image credit: Soldering Is Easy Comic Book)

Now, this is really important. Pull away the solder first, and continue holding the iron for another second. This allows the solder to continue to melt and pool, forming a good joint. Then, you can remove the iron. The total process shouldn’t take more than 5 seconds, and usually you’re aiming for 3-4.

Wait a few seconds and don’t disturb the solder. It cools very quickly, but moving or blowing on the joint will cause it to deteriorate. A bad solder connection will look really oxidized, overly dull, and grainy. It also sort of looks like a ball of solder formed on the area. A good connection should be smooth and uniform, and its sides will be concave. It won’t look like a raised ball, it’ll look flat.

Desoldering

When removing a connection or undoing a mistake, you can often resolder over the original and add a touch of new solder. If you want to take the extra step and do it right, you can remove the old solder completely and start with a fresh work area. There are two tools you can use for this, a vacuum-based “solder sucker,” or a solder wick.

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(Image credit: Wikimedia Commons)

A solder sucker is essentially a tiny hand-held syringe-like pump. It creates and uses vacuum pressure to suck solder off of whatever it’s on. It’s a great tool to have and works well.

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(Image credit: Wikimedia Commons)

A solder wick is woven copper which the old solder bonds to. It’s more expensive and it’s expendable, so I usually don’t recommend it. Some jobs, however, will greatly benefit from the clean finishing touches that a solder wick provides. Both tools have their strong points, and odds are that in your soldering career you’ll need to use one or the other specifically from time to time. Having a clean working area is really important, as it provides the best results and minimizes risk of damage.

 


Soldering isn’t particularly difficult. You just need to focus, keep a steady hand, and be safe. A good soldering iron will prove to be a wonderful investment, leading to a much wider arrangement of geek projects at your disposal. Now that you know how, practice so that you’re ready to show off your skills!

 

Have some soldering “tips” of your own? Share your molten-hot stories in the comments!

Yatri Trivedi is a monk-like geek. When he's not overdosing on meditation and geek news of all kinds, he's hacking and tweaking something, often while mumbling in 4 or 5 other languages.

  • Published 05/17/11

Comments (25)

  1. bobro

    how do you make PCB boards? or are you guys just soldering to exsisting boards.

    (i dont mean in the general scheme of things i mean how can you do it at home)

  2. Porkfist

    Some components such as diodes can be damaged by the heat of a soldering iron, and require the use of a heat sink. An alligator clip or pair of needle nose pliers will usually do the trick. Some components are also polarity sensitive so be mindful of that as well.

  3. poisoncidr

    First,
    This article is for lead based soldering which is all but gone in electronic devices. If you buy something new like a computer, cell phone, television that is classified as retail electronics… you can rest assured that it has lead free solder inside and “lead free” is a whole new ball game relative to techniques and equipment. Not only does it take different equipment, different solder, and higher temperatures but it is also more costly and takes some practice even if your an excellent solderer using leaded systems. While leaded solder flows freely, such is NOT the case with “lead free.”
    Next,
    Porkfist, I have been soldering for years and have never damaged a diode from heat damage. In your first electronics class they show you the alligator clip but I have yet to use one. As for polarity sensitive, this has nothing to do with soldering. Instead, you must be aware of inserting the device backwards prior to soldering. If you got it wrong, in the case of a capacitor, you will know about it once you turn the device back on.
    Finally,
    Lots of devices today, like on mother boards in computers, have no visible pins but they have been soldered and require special equipment to remove and replace them. So this is my advice, let someone else do it. Someone that has the right equipment. Entry level equipment sucks for both leaded and unleaded soldering and the good stuff will cost you more than a nice cell phone. So just take it to someone who knows what they are doing. Better yet… buy extended warranties. I practice what I preach.

  4. john bennett

    how can one tell if the product has been soldered “lead” or “lead free” visually ?

  5. Ryan

    @poisoncidr

    There are plenty of other projects to solder other that computers/phones. I like modding guitar pedals which require soldering the components and I recommend anyone to pick it up and have a go as it is relatively easy.

  6. Vaidya

    My experience is that the solder gun tip always repels the solder metal. How can I tin it. So is the case of the component. I have cleaning wax. It spoils the tip as it gets coated with some bad stuff. Am I using wrong or the spoilt wax. If I use wet sponge, will it not get burnt by the gun. I finally have to use sharpening stone to clean the tip. And it get spoilt in no time. Seeking help from experts and thanking in advance.

  7. Paul

    @ Vaidya: Just follow the advice in the article about letting the iron (assuming you mean that and not a soldering gun which is very different) warm up, and then giving it a wipe on a damp sponge to clean off the black oxidation prior to tinning. If the tip is really hard to clean up and it’s repelling the solder, it could be because it hasn’t got a good thermal connection to the heating element so it’s not getting hot enough (and getting the components hot enough). Check the tip is pushed/screwed in fully, but obviously let it cool first! Alternatively it might benefit from a gentle sanding with some fine emery cloth or similar. If you use something as abrasive as a sharpening stone it’ll take the polished finish off the tip as well, which as you’ve found causes the oxide to really stick the next time and makes it even harder to clean.

    As a final tip (no pun intended), it might just be that you need to spend a bit more on your equipment. As the article says, you pretty much get what you pay for with soldering irons.

  8. Paul

    Btw, one other point that might be useful to readers occurred to me when I was reading the article: Soldering irons come in different power ratings or Wattages. This doesn’t necessarily affect how hot the iron gets, but how much heat it can supply to the joint being soldered. Soldering large metal objects can be difficult because they act like heat sinks and can draw heat away from the joint (and the tip of the iron) faster than the iron can supply it, preventing the solder from melting or forming a good joint. Higher Wattage irons can maintain a better heat supply in these conditions.

  9. Groff

    I hate lead-free solder. So much. Even with my good iron, it’s such a pain to work with.

  10. novachris

    do tips on the soldering irons ever need to be replaced and if so how can you tell when they need to be

  11. Anonymous

    Most soldering “guns” are also bad joo joo for electronics because many of those gun-style irons are inductive too. You may get away with not damaging things by having a high-voltage inductor near your sensitive electronics, but the potential to cause damage grows exponentially the closer you move any live inductor to them. Fortunately, most of those inductor soldering guns are also (Faraday) “shielded” which significantly reduces this risk. But why take that risk in the first place? Just don’t use inductive soldering guns on electronics.

    (You might also move those low hanging high watt fluorescent lights away from your electronics too. And for much the same reason!)

  12. chrisbphoenix

    I’ve been soldering more and more recently, and I have come across two different types of iron tips. One is like a needle and is pointy, the other is like a small spade (ish) and is flat on the tip. (more like a straight blade screwdriver) I was wondering… is one kind better than the other. Or, what kinds of jobs are best handled by each? Personally I prefer the flat tip. (But admittedly I am a novice)

  13. oldham

    When solder balls up, it usually means the iron is too hot;and this also causes faster oxidation.
    A swipe or two on the damp sponge will,up to a point,remove enough heat from the tip if you do
    the next soldering operation quickly. If the iron is too hot, the sponge will not cool it enough, and
    you must turn off/turn down for a while. Swiping alone is not enough to *clean* the tip; it is best
    to keep an old knife,relegating it to this purpose(the lead!). As the iron is heating up, give a light to
    moderate scrape on the tip; when the iron is hot enough, the scrape plus touch of solder will tin
    the tip. If you don’t scrape, it is almost impossible for the solder to tin, unless you clean the tip
    with fresh flux(very messy). In fact, an old trick to solder a wire to aluminum,supposedly impossible,
    is to strongly sand/clean the aluminum surface, and *quickly* flow hot solder onto the area; keeping
    the pool of solder hot,stick a sharp awl into the pool, and scrape the surface; position the wire into
    the pool so that it does not move, and remove the heat. This trick usually requires a gun, due to
    the amount of heat required. In fact, cleaning is supremely important for all the surfaces involved,
    as it enhances the effectiveness of the flux. Finally, not all “cold soldered joints” look grainey,etc.
    Sometimes they look beautiful! This because only a slight vibration during cooling can wreck the
    joint electrically. The solutoin is to simply retin the tip,etc. and simply reheat the joint;it will reflow.
    Sadly, I no longer do this due to shaking hands, and the new lead-free solder would probably drive
    me insane.oldham.

  14. Frodoshopped

    Don’t buy a iron by wattage rating. All it means is that it has constant wattage to the tip. It doesn’t mean you have constant temperature to the tip which is much more important. Buy a good temperature controlled iron. They are more expensive, but much better – it will maintain the temperature you set to the tip so you avoid “spikes” of cool downs when you touch the iron to something metal – it will keep the heat flowing properly and make it easier to solder. Invest in a good Weller or something like that. A solder wick is great for trying to remove components from a circuit board – often it’s the only really good way to get solder away from the leads of a chip (especially if you’re working on an old board where the pads are delicate or you’re trying to save the chip!)

  15. Cactus

    For the people who cant say the word right, Its pronounced ‘SOLE – DER’ :P

  16. RickM

    When soldering the joint, make sure you apply the new solder to the joint, not to the area where the iron is touching. The solder will flow smoothly around the entire joint.
    When tinning the tip, don’t wait till the tip reaches its full temperature. Tin it while it is heating up. The solder won’t ball up doing it this way.
    If the tip gets too corroded or pitted and swiping it on a wet sponge doesn’t make it shiny again, then it will need to be filed down after the tip has cooled, of course. Just use a clean, fine file and reshape the tip until it’s shiny copper color comes back. Some steel tips can’t be filed, only “scraped” with emery cloth, not sandpaper. Turn it back on and tin the tip as it heats up. It’ll be shiny again and work like new.

    Rick

  17. RickM

    In America, it’s pronounced SOD er. Not Sole der. The “L” is silent.

  18. Andrew Nierman

    I am surprised no one has mentioned “flux”. The molten solder will only adhere where there is flux!

  19. btcoyle

    Mabye Cactus is one of those know-it-all Brit douchebags, but here in the US, solder is pronounced “sod – er.” If you say “sole – der,” you’ll just sound like you’re retarded.

  20. Dissident Penguin

    @Andrew Nierman. Solder usually contains the right amount of flux needed to melt it. Adding more increases the amount of fumes inhaled and could result in excess flux, which is corrosive and changes the electrical properties of the joint, so it is better not to use it unless your solder doesn’t have enough. Even then it would be advisable to buy better solder. In case you can see flux covering your joint when it cools down, it´s better to remove it with nafta.

  21. Ted

    One important thing not mentioned is that the component to be soldered is CLEAN or you will possibly end up with a dry joint.

    From a retarded Brit who calls it as it’s spelt, solder and have been doing so for over 55 years. LOL

  22. Bart

    After having soldered professionally in an assembly-firm for 2 years, a bottle of liquid flux is something I always keep next to my Iron. With a little brush I apply some on the components and copper clad to be sure they’re clean. The flux stinks like h*ll, it evaporates fast (don’t leave the bottle open), it probably isn’t very healthy and good ventilation is needed.
    Using it makes all solder-jobs 10x easier.

    Another tip, laying your project flat on a table can result in mess, too much solder and lots of unwanted connections. Let gravity help you by making a stand tilting the board 75-85 degrees. Excessive solder, while liquid, will fall right off.
    Besides using a solder-sucker/ solder-wick you can correct unwanted connections on a tilted board by adding (!) solder under the tip and pulling the iron down.

  23. templets

    I solder things to build microelectrodes for surgical implantation into rat brains, and, in my experience, if there’s a significant melting point difference between the two things being soldered together, then I’ve noticed that it’s better to actually remove the iron first and then the solder (more solder may be applied while the joint is still hot enough to melt the solder, as well), which is contrary to the article. Even after doing this, the connection may not be strong enough to withstand most simple physical manipulations.

    Does anyone have any solutions for easily soldering two objects of a significant melting temperature difference?

  24. jonno

    Thanks for this how-to.

    Very clear and useful instructions.

  25. Julian

    Templets, that is the coolest job I’ve ever heard of. You have the best life.

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