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I bought a 20W soldering iron a while ago and I found the experience very frustrating as the tip does not get hot enough quickly and when it does melt the solder it gets cold so quick I can't get the solder to flow long enough i.e. I end up with blobs all over the place.

A friend of mine heard all my cussing and praying for a more powerful iron when I was putting a circuit together and out of the goodness of her heart she bought me 100W soldering iron from Hong Kong. I was praying for a 60W model. This new soldering iron gets hot, about 420 C and I an easily get the solder to flow but I am worried about this high temperature killing my PCB or components.

  • Is a 100W iron safe to use on Arduino type projects?
  • What are the risks I run with using this type of iron?

Just a safety check before I destroy something valuable.

Update:

Been soldering for a while now with both the 20W and 100W and they both have very different uses. The 100W is NOT recommended for smaller jobs and finer components - it is way too powerful. I replaced the tip of the 20W iron and tinned it properly and been keeping it tinned. It is actually not that bad so I suspect my blues started with the tip not being maintained properly. Lesson learned experienced gained.

Update 2:

Finally invested in a proper soldering station (Hakko-FX888) and I am in soldering heaven. I felt like I have been trying to paint the Mona Lisa with rock with my other irons. Life is beautiful again.

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    \$\begingroup\$ Safety in most soldering is proportional to skill and care. When you really get into this stuff though you'll want a temperature controlled iron. \$\endgroup\$
    – user39962
    Commented Mar 1, 2015 at 1:26
  • \$\begingroup\$ @SeanBoddy I did soldering at high school as part of my electronics course however over the years I did very little soldering so initially I was a bit rusty. I try to keep the heat as low i.e. make enough contact to just get the solder flowing and get the joint done before breaking contact. However I was more concerned that there is some sort of hard limit I forgot about over the years. \$\endgroup\$
    – Namphibian
    Commented Mar 1, 2015 at 1:32
  • \$\begingroup\$ Its about timing and control. That 20W iron would destroy just about anything - eventually. A temp controlled iron gives you better control and can ramp power to maintain a given temperature, which gives you much more flexibility. \$\endgroup\$
    – user39962
    Commented Mar 1, 2015 at 1:38
  • \$\begingroup\$ You might be able to use a dimmer to reduce the output of the 100W soldering iron, but I don't recommend trying it and you certainly didn't hear me suggest it. \$\endgroup\$ Commented Mar 1, 2015 at 1:50
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    \$\begingroup\$ don't screw around, get a temperature controlled one. \$\endgroup\$
    – Pete W
    Commented Jan 2, 2021 at 19:25

5 Answers 5

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Using a 100W soldering iron will obviously get the job done. It will melt nearly any width electronic solder, and maybe do some moderate plumbing jobs too. With an iron like this you will likely never learn the important aspects of soldering sensitive electronics. You will possibly destroy many parts as you learn.

A 20w soldering iron should be well enough for most electronic soldering applications, (except for very thick wires or heavy duty solder lugs). One of the most important things is to learn how to keep the tip "tinned". This helps transfer the heat to the item being soldered. Tinning a solder tip involves cleaning the tip and getting a thin coating of melted solder on it. This is easy to recognize as the tip will stay shinny with the liquid solder. When using the soldering iron it is also important to frequently clean the tip using a damp sponge (often sold with a soldering set). See some additional tips here:

http://www.wikihow.com/Solder

https://learn.adafruit.com/adafruit-guide-excellent-soldering/tools

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  • \$\begingroup\$ I find using brass tip cleaner more appropriate. The schock when dipping hot iron tip into cold moisty sponge can cause microfractures. \$\endgroup\$
    – Golaž
    Commented Mar 1, 2015 at 18:53
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    \$\begingroup\$ @Nedd I kept the tip tinned on the 20W one but I am pretty sure it is faulty now as it just does not heat up properly. I use a brass tip cleaner as well as a sponge. Now that I think of it the iron must be faulty as it just heats up a a little then almost dies. I have had it for just over a year and about 2 months ago the performance just went very bad. \$\endgroup\$
    – Namphibian
    Commented Mar 1, 2015 at 20:11
  • \$\begingroup\$ @Golaž: Only poor-quality soldering iron tips shatter when subjected to these hot-cold cycles. If your tip breaks because you're using a sponge, that's your hint that you need to get a better iron. I'm not talking about extravagant expenses here; I've used US $9 irons that easily withstood use of a sponge. \$\endgroup\$ Commented Mar 1, 2015 at 21:11
  • \$\begingroup\$ @Namphibian I've experienced issues you mentioned with two recent cheapy soldering irons. It's a pain. Mine heats up enough to solder 1 connection then the work to solder the one connection seems to cool the tip so much that I have to wait a minute or two to solder next connection. I also noticed this occurred more when the tip would get loose (there's a screw holding it). But even after I tightened it down it kept giving me problems. I don't remember these challenges in the past with irons - they must've run hotter (higher wattage) or whatever. Planning on buying better one this year. \$\endgroup\$
    – raddevus
    Commented Jan 2, 2021 at 19:38
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    \$\begingroup\$ This wholly misses the issue. Thermal equilibrium irons are bad no matter what the wattage. The era when people were told to chose a small one represents a set of compromises which are today long obsolete. A proper temperature controlled iron is fundamentally better at high wattage, and the better ones preserve tip life by cooling in between uses within a work session. The only downside being if it is physically unwieldy. \$\endgroup\$ Commented Jan 2, 2021 at 20:10
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With practice yes. Don't stay on the part too long, and everything should be OK.

I have a 100W that I use when not at work, never had a problem.

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  • \$\begingroup\$ Thanks as I suspected it should be fine. I guess a tip would be if the pcg starts melting you kept the soldering iron on the board too long. \$\endgroup\$
    – Namphibian
    Commented Mar 1, 2015 at 5:12
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    \$\begingroup\$ If your 100W iron is temperature-controlled, you can't compare it to a 100W pencil iron. \$\endgroup\$ Commented Mar 1, 2015 at 20:54
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A good compromise is 40W iron for larger components and 20-25W for small, sensitive ones. 100W is way too much.

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It is much more important how good is the temperature regulator of the soldering iron (or if any is present). Another is the size of the soldering tip: if the iron is intended for massive components, the tip may be just too large.

If a good regulator is present and the tip has the right size and shape, I do not see how more power could be a problem. Differently, it may prevent the undesired cooling down when soldering something bigger. The regulator would restrict the power to much less than maximum once the set temperature is reached.

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  • \$\begingroup\$ Exactly. The argument for a low wattage iron comes from the compromises of a previous generation when temperature control was only available in the highest end solutions, rather than today where it is the norm in all but the throwaway cheapest. \$\endgroup\$ Commented Jan 2, 2021 at 20:13
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100W solder guns (not as much always-on irons) are somewhat more tenable for unsoldering large components in old TV sets and household appliances, the stuff that has really fat solder points and partly metal cases soldered to a robust PCB.

100W always-on irons are more for soldering plumbing and sheet metal.

Neither are suitable for soldering integrated circuits and small components. I've worked for most of my electronics experimental time with a 16W solder iron without active temperature control (basically, the resistance of the heating coil went up when it got too hot).

The main thing is making sure that the heat actually flows well from heating element to solder tip: the tip needs good contact and heat transfer from the shaft it sits on (if necessary, taking it off and bending it slightly narrower if it sits too loosely) and needs to be clean and tinny at its tip.

While more (and actively controlled) power makes this less of an issue, good heat transfer remains something that makes things work better.

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