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I have a FULGORE soldering iron (quite an unknown brand, isn't it?) and I think it is not working properly but I would like to hear the opinion of experts.

The iron, as mentioned in the title, operates on a nominal power of 25 W, but I have found it quite difficult to use - I think it is not transferring enough heat to the parts to solder.

After letting the iron heat up for about a minute or so, I try to melt solder to the tip of my iron, and it is possible, it just takes a couple of seconds; it is a lot easier melting solder on the sides than on the thinnest part of the tip though.

But then, if for example I wanted to solder two wires together, I would put the tip in contact with either of the wires, and stick the solder wire to the joint, waiting for the wires to get hot enough to melt the solder. This takes forever though, with this iron.

What could be wrong with my iron? Is it perhaps the iron itself?

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    \$\begingroup\$ @Leon Heller Since when are questions like this off-topic? \$\endgroup\$ – AndrejaKo Dec 15 '11 at 10:16
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    \$\begingroup\$ Those 25Watt irons just stop working properly after a while, cheap heating elements or thermostats. They cost like a few bucks right? get another one.. or buy a proper one like Weller..I have mine 15years now.. no problems, just change tips from time to time. \$\endgroup\$ – Piotr Kula Dec 15 '11 at 13:01
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    \$\begingroup\$ @Leon: There you go again. No, I don't think the question will be closed. Again, by flat out stating it will be closed you give the impression you have the authoroty to do that and that you know for a fact it will be closed. Neither is true. Please stop misrepresenting yourself like this. \$\endgroup\$ – Olin Lathrop Dec 15 '11 at 14:34
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    \$\begingroup\$ While this has nothing to do with electronic design, it is a relevant issue faced by anyone doing electronics, and I will not vote to close the question (it takes 5 votes or a mod decision). Besides, if not here, where can someone ask for advice about soldering and soldering tools? I don't care much about the letter of the law in the FAQ. To me it feels sufficiently relevant to this forum. \$\endgroup\$ – Olin Lathrop Dec 15 '11 at 14:37
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    \$\begingroup\$ @Kortuk: I wasn't objecting to Leon acting on his opinion that the question should be closed. I was objecting to the way he said that implies that he alone can make that determination. He alone doesn't get to decide that it will be closed. He can only contribute a 1/5 vote towards that or express the opinion that it will be closed. That may be semantics, but especially for new people here his flat out "will be closed" can be taken the wrong way. \$\endgroup\$ – Olin Lathrop Dec 15 '11 at 17:54
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We'll need more info to help you. First, post a picture of the tip itself. It could be damaged and we'll need to see it to be sure. I'll explain later on why that is important.

Next check your iron's manual and see what it say about time required to heat it up. My (also 25 W) says that 1 minute is needed to reach operating temperature. The heat transfer also depends a lot on the condition of the tip. If the tip is bad, then it could take a while for it to melt solder even if the temperature is reached.

Next are the wires. What size of wires are you using? The size of the wires makes a huge impact on the quality of the soldering and 25 W irons can't handle thicker wires (say greater than \$0.75\mbox{ } mm^2\$).

Are you sure that you're soldering them correctly? The description of the process makes me doubt that. You're supposed to first connect wires mechanically (here are some nice pictures) and then heat up the joint until it reaches the high enough temperature to melt the solder. You should connect the iron to the joint in such way that the both wires are in contact with the iron. Don't forget to have a little bit of solder on the tip of the iron when you make first contact. This will cause better heat transfer and in addition to that, once the tiny bit of solder on the tip flows into the joint, the region near the tip if probably hot enough to get the solder wire. In some cases if you keep heating up both solder wire and the joint at the same time, the flux from the solder wire can melt prematurely. The whole process should take only several seconds or the insulation of the wires can melt. If it takes too long, leave the iron for some time to heat up first.

About the comment:I agree that the water probably did it. Here we actually have several factors that work together to kill the iron. First one is the composition of the tip. Most tips are made from copper and better ones will have some fancy alloy at the tip of the tip which is supposed to prevent the working end from oxidizing. As the tip heats up, it becomes more chemically reactive and will tent to oxidize. To prevent the contamination of the working part, we put some solder wire there which will cover the working end of the tip and oxidize instead. So when we put that into water, it is to be expected that the tip will corrode. In addition to that it may react with any impurities in water itself and get even more contaminated. Same goes for the soldering iron itself. As the tip gets more corroded, its thermal resistance increases meaning that we'll have greater temperature difference between the heater and the tip. When connected to the heater, the tip will act as a cooler and when it's contaminated, its performance will decrease. That may cause the heater to overheat and in some cases my damage it. This may even destroy cheaper soldering irons completely.

Next we have the problem with rapid cooling in the water. When the tip heats up it expands and when it cools, it shrinks. In some cases cooling it very quickly can lead to creation of small cracks and small pieces of the tip may actually fall off. I suspect that the films were made by that process. You naturally want to prevent that from happening and that is another reason why you should let the iron cool off unassisted.

When you combine two of that, you get what you got.

Now for the iron itself... Check where exactly the heating element of the iron comes into contact with the tip and how the system works. If that part isn't corroded, then I'd let the iron be and get a new tip. I fear that agitating the corroded part would only make the problem even worse. If the part where the tip comes into contact with the heater is corroded, then you could try cleaning it somehow. It should (hopefully) make the tip's contact with the heater better. If it's really badly corroded, then consider getting a new iron.

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  • \$\begingroup\$ Well I first disassembled the tip from my iron, and a lot of rust came out, or at least thin films of metal. The iron looks a bit rusty yes, but I don't have a camera decent enough here to show you how the tip looks. However, I think I know now what I did wrong. I was using a small glass of water to cool off my tip whenever I finished using it. I bet this created enormous amounts of rust, so I guess my tip is whats causing the problem, overall. Stupid, right? \$\endgroup\$ – Severo Raz Dec 15 '11 at 20:36
  • \$\begingroup\$ @Wolter Hellmund Stupid indeed. In fact it's so stupid that you should probably spend some time watching soldering tutorials and try soldering the way they show (I'll see if I can dig up some nice ones). In fact the procedure is so unusual that I don't think I've seen anyone warn against doing so. \$\endgroup\$ – AndrejaKo Dec 15 '11 at 22:06
  • \$\begingroup\$ @Wolter Hellmund Well what's done is done. I'll think of some ways to determine how can we determine if it's just the tip or the whole iron. I'll post another comment when I update my answer. \$\endgroup\$ – AndrejaKo Dec 15 '11 at 22:08
  • \$\begingroup\$ @Wolter Hellmund I added some more information to my answer. I hope it's useful. I'm actually out of ideas what would be a smart thing to do now. \$\endgroup\$ – AndrejaKo Dec 15 '11 at 22:42
  • \$\begingroup\$ Your answer seems pretty well founded, I will see what I can do with my iron. It seems that the iron is alright except for the end of the tip and a short section of the tip holder where its closer to the tips end. I doubt the latter will affect considerably the heat transfer, since the tip is quite long and receives heat all along its body. Now, I will focus on the tip to see if this solves the problem. Do you think sanding the tip until I see no rust is a possible fix? \$\endgroup\$ – Severo Raz Dec 15 '11 at 23:26
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It's probably technique:

  • Soldering iron tinning matters much, as people have said.
    Below are some variably useful links, some directed more towards tinning the iron but most also covering soldering in general.

But

  • If you are doing all the following OR can say what they are doing wrong, then your iron is faulty :-).

NASA student workbook for soldering course 100+ pages. A bit NASAish but some good stuff there.

Instructables looks OK - YMMV

OK

Soldering:

Good

Good - diagrams and video

OK - tinning copper wire


THEN build eg this.

Extreme soldering 101.
Build a WiFi Cantenna

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25W should be enough for simple stuff like soldering two wires together. In fact, after 5-10 minutes the problem will be the tip will get too hot and therefore oxidize excessively and overheat things it touches.

If it's not doing that then it's most likely broken. Sometimes these cheap soldering pencils have replaceable elements since they do burn out. However, you get what you pay for. For real electronics work a temperature controlled soldering station is far better.

Another possibility is that the tip has gotten so hot in the past that it is heavily oxidized. The oxide layer won't conduct heat well, but more importantly, solder won't flow on it. The lack of the wetting action prevents the solder from really touching the tip properly, thereby not transferring much heat due to small contact area.

Do you tin the tip regularly? Is it nice and shiny when you try to solder the wires together? You can't decide whether the iron is broken until this is true.

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