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It's been a while since I have soldered, so I bought a cheap unbranded soldering iron to use while I re-familiarised myself with the skill. After a few weeks of use, I turned it on just now and it popped with a blue spark. Now it appears to be dead. Did I do something wrong, or is that simply what happens sometimes when you buy a cheap soldering iron? I'm curious to find out what could have happened.

Ironically, just before the magic smoke escaped from the cheap one, I actually bought a new soldering station (Hakko FX-888D) earlier today, as I had a feeling it was time to get better equipment. Spooky. I guess the cheap one got upset and self-destructed.

Out of curiosity, I dismantled the dead soldering iron and took a photo of the board inside.

Dead soldering iron PCB

With my limited knowledge of electronics, my intuition tells me that an arc occurred between the AC wires. If so, is this bad luck, bad soldering, or user error?

Close up of the burnt AC wires

The insulation appears burned, but also the core of the wires seems to be a bit frayed. Was this as a result of the arc, or low quality manufacturing?

Bonus question: I wasn't touching the button at the time the iron popped, but if I was, would I have received an electric shock? Would it have been life threatening or painful?

Edit: I am in the UK (230VAC).

Nick Bolton
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    It's very probably not your fault--those cheap soldering irons aren't worth even the tiny amount they cost. You seem to have purchased exactly the iron I would recommend to replace it, so good choice! – Hearth Jul 03 '21 at 21:55
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    People don't destroy soldering irons. They destroy the tips, and the soldering iron destroys the work. – DKNguyen Jul 03 '21 at 22:37
  • Did it have a fused UK plug? – DamienD Jul 03 '21 at 23:53
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    were you soldering on live wire/circuitry? if so, it is your fault. otherwise its likely someone manufactured the soldering iron's heating coils poorly. – Abel Jul 04 '21 at 00:44
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    Also, if getting cheap gear go for simple- like an iron with no temperature setting (or power button) for example. KISS helps reduce manufacturing screwups that make it to store shelves. – Abel Jul 04 '21 at 00:51
  • @Abel Great tip: if going cheap, keep it simple. The iron was sitting in the holder (I was waiting for it to heat up). – Nick Bolton Jul 04 '21 at 01:21
  • @DamienD Yeah, I’ve been using it for a few weeks. The fuse in the plug looked ok at first glance. – Nick Bolton Jul 04 '21 at 01:22
  • _"cheap unbranded soldering iron"_ - can you provide a link to the product or a similar one? – Bruce Abbott Jul 04 '21 at 07:27
  • I did have the link in but someone voted to close; assuming that was the reason, I removed the link. Here it is anyway: https://www.ebay.co.uk/itm/203450194573 – Nick Bolton Jul 04 '21 at 09:11
  • Also, I pulled the earth away with a solid tug. It left only 4 strands behind. The solder joint was very weak. I imagine after a good amount of use, it would have worked it's way free eventually. – Nick Bolton Jul 04 '21 at 09:12
  • Can you add the (nominal) value of the mains voltage at your location to your question (but ***without*** "Edit:", "Update:", or similar - the question should appear as if it was written right now))? For instance, is it 240 V? – Peter Mortensen Jul 04 '21 at 10:13
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    What is the unit of the scale in the background? Centimeters? – Peter Mortensen Jul 04 '21 at 10:19
  • If you call this cheap, then I don't know what should I call the ones that I had once worked with. Cost less than $2, no adjustment, switch, or indicator. And they lasted a few years each, just the bit replaced once or twice a year. – paki eng Jul 04 '21 at 16:06
  • @NickBolton When you buy something, it can be a good idea to look inside to make sure everything is in order. Of course, you have to avoid destructive disassembly, and you would have needed a soldering iron to fix that one... – Andrew Morton Jul 04 '21 at 16:30
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    @NickBolton If you re-make those connections when your nice new iron arrives, you might have a working iron that you can use for messy jobs like melting plastic. – Andrew Morton Jul 04 '21 at 16:39
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    Yes. I think it arced over due to insufficient clearance (design issue) or poor workmanship at manufacture, or both. – user57037 Jul 04 '21 at 19:44
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    You could destroy soldering iron tips. Worst case (not sure if actually possible) the tip damage could also damage the heater. But that shouldn't make the circuit board go pop. No way that's your fault. – user253751 Jul 04 '21 at 20:46
  • @AbdullahBaig I've got one of these, and a couple of even cheaper non-adjustable ones. The one that goes hot enough to work with lead-free only has a massive tip (and it's unique), the one with nice tips will melt lead-free but only just. – Chris H Jul 05 '21 at 15:49
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    "Cheap" soldering iron with ICs inside, and a pushbutton? For most cheap soldering irons, its an element in a handle, crimped to a mains lead, with a (maybe replaceable) tip at the end. – Criggie Jul 06 '21 at 04:40

4 Answers4

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Just looking at how these wires are soldered to the PCB indicates a low quality product. I would not blame you but the product instead.

Jakob Halskov
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    Could the way that AC wires are soldered to a PCB cause cause an arc? – Nick Bolton Jul 03 '21 at 23:00
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    And, would I have gotten an electric shock if I was touching the power button? The power button is right next to the AC solder connections. – Nick Bolton Jul 03 '21 at 23:00
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    If the one strand of wire snaps it could end up bridging live to neutral or to ground. and to me that looks like what happened. – Jasen Слава Україні Jul 04 '21 at 03:11
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    At best you'd get a big scare, at worst this product can be lethal. I'd request a full refund and flag/mark/review it as a dangerous product where you purchased it. And finally congrats with your new Hakko iron, it is a nice step-up :) – Jakob Halskov Jul 04 '21 at 11:14
  • You'd have to look at the wires/joints _before_ they burned to crisp. It does look like bad wetting, but it is hard to judge the quality of the soldering as it stands. Not using an isolated connector instead is rather the main remark here, but that's related to the PCB design. – Lundin Jul 06 '21 at 07:30
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This soldering iron is garbage. The PCB has been soldered by machine and is likely ok. The power cable looks like it hasn't even be soldered on in a factory but by home workers with bad equipment and bad skills. It starts by the cables not being properly deinsulated (you can see a number of torn copper strands) and then not being properly twisted and presoldered (you can see lots of blank copper) and then not being properly shortened: there are far too long open strands off the solder pads. The solder joints look more baked on rather than thoroughly heated, particularly the right one. Also it appears like there has too much been cut from both outer insulation and wire insulation to have any pull protection measure work reliably.

I would expect the ground wire to easily sprout a copper wire over where it may touch the live wire.

But it doesn't even look like that is what happened: one can see in the upper picture that tracks leading to the switch have burnt off, so the short wasn't even in the awful cable soldering (where the damage would have been contained nearby while blowing the fuse) but was somewhere higher.

In addition, the PCB design does not appear to accommodate any significant amount of cross section for the ground tracks, so the amount of security provided by them is limited: you might get a flash and a bang and the thing continues "working" after having rid itself of the ground track. And might even work for the next user after having killed you.

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It looks like the mains cord was not fully soldered to the board.

You can see a stray whisker of the ground still. There were probably also loose strands on the current-carying conductors. They probably flexed enough to touch when you were handling the cord, and when you plugged it in, they bridged a rush of current through and vaporized. POP!

I'm kind of surprised that it broke the iron. It shouldn't have. But whatever. I've been using $10 irons all my life and they work okay for me without any circuit board inside them. But that hakko is super great too, so enjoy it.

Billy left SE for Codidact
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  • Perhaps it blew a fuse. Nick could check whether the plug or cord has a fuse (doubt it unless they live in the UK) – user253751 Jul 05 '21 at 13:12
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That thing was not UL Listed

and should never have been plugged into AC power. It violated the safety codes of lots of countries.

Never plug anything into AC power that isn't UL Listed.*

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Buy from reputable vendors in the future. Note that on Amazon, many third party (eBay crud tier) items ship from Amazon warehouses with Prime. Make sure the seller and shipper are both Amazon, and you have a chance of getting a better quality product. Amazon seems to follow the "bricks and mortar retail" quality laws on their own stuff.

The safer option is to buy from actual bricks and mortar vendors (even if you mail order from them), such as Home Depot, Galco, Grainger, Radio Shack (though watch out these days) etc. Sorry, there's slim pickings these days for electronics bricks and mortar. Mouser and Digi-Key and McMaster-Carr have been reliable IME.

* Or if you want to get into the gory details...

Listings from other NRTLs are generally acceptable. That is because the other NRTLs duplicate UL's high level of independent third-party scrutiny. Off the top of my head, British BSI, German TUV, a dozen others. UL and the other NRTLs are extremely aggressive about defending their mark, and as a result, UL, CSA, BSI and TUV marks are almost never seen faked.

Who the heck is USA OSHA to decide who is an NRTL? I don't know, but somebody has to do it, and they do a good job, and many agencies in many countries simply defer to that list rather than try to administer their own list.

The CE mark is universally faked, mockingly, on a "catch me if you can" basis by pretty much every manufacturer who keeps their assets outside the reach of EU authorities. The only way to count on that mark is to buy at a competent, trustworthy bricks-and-mortar shop physically inside the EU whose assets are inside the EU. Walk into Wickes and you're fine. With mail-order, all bets are off. It only works if you have a responsbile in-EU seller, such as Wickes.co.uk or Mouser. But many warehouses, such as Amazon's, do drop-shipping for many third-party sellers. Amazon is not responsible for regulatory compliance for third-party items, even those sold on its site. So effectively, ordering a third party item on Amazon (or other website where Amazon or a like-minded shipper is the drop-shipper) is the same as direct ordering overseas - there are no consequences for faking the CE mark, so it most likely is faked on a product whose distinctive feature is that it is a bargain.

Pretty much the same for the CCC mark. The manufacturer may be in the jurisdiction of the mark issuer, but the government turns a blind eye if the item is only for export.

I have researched these companies. As an example, I found one who claimed to be a 100-year-old famous German electronics firm which had merged with a four-year-old American LLC. Their USA address was an apartment block in Sunnyvale. Their German address was a drop box in downtown Dortmund. Their China address was a massive industrial park. Nothing within the reach of EU authorities. They had bought the corporate shell of the defunct electronics company.

I realize many readers want to believe those oh-so-cheap items on Amazon are legal and safe. I'm sorry to burst your bubble.

Note that even when CE is working as intended, by an EU company with EU assets selling inside EU watched by EU regulators, the CE mark is still a self-certification, which is weak tea compared to a third party NRTL certification and followup examination. EU used to agree; that is why BSI and TUV were formed in the first place.

Harper - Reinstate Monica
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  • Good answer. Could you tell me more about how to check if something is UL listed? How did you find out that the product wasn’t UL listed? – Nick Bolton Jul 05 '21 at 23:26
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    Look for the distinctive UL in circle mark, along with a 6-9 digit "file number". I can tell the product wasn't UL listed because I pay a lot of attention to certain supply channels, and also, that build quality lol... note that UL is not the only NRTL; others will suffice but CE isn't one. – Harper - Reinstate Monica Jul 05 '21 at 23:34
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    Good luck finding small 230V-only appliances with a UL listing in the UK. CE has been deemed good enough by the appropriate authorities, so that's what you get, regardless of issues caused by dodgy self-certification (or outright fakery) – Chris H Jul 06 '21 at 07:56
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    UL is an American certification company, UL Listed only means that the product was tested following guidelines issued by that particular company. There are other certification bodies and standard and it varies widely across the globe (IEC, CE, CSA, CCC, etc...). Usually only product sold in north America are UL tested. – Damien Jul 06 '21 at 08:58
  • CE is the European Union's certification scheme. Over the course of this year Britain is introducing its own scheme, UKCA. https://www.gov.uk/guidance/using-the-ukca-marking – padd13ear Jul 06 '21 at 10:48
  • @padd13ear No it's not. **CE is so universally faked that it has no meaning at all**. Overseas manufacturers fake it gleefully, on a "catch us if you can" basis - and EU enforcers *can't* because they take care to leave no assets inside the EU. The mark only works at a competent, well-behaved, trustworthy bricks-and-mortar EU business located physically inside the EU with seizable assets inside the EU, and even that doesn't work with mail order, thanks to Amazon's "our warehouse is a free trade zone" model. *At best*, CE is a *self*-certification, "fox guarding the henhouse" sort of deal. – Harper - Reinstate Monica Jul 06 '21 at 13:39
  • @Damien I didn't feel the need to complicate the discussion by getting into the other NRTLs, such as BSI and TUV, which are in the UK and Germany respectively. Mentioning IEC, CE and CCC in the same sentence as CSA tells me you have more to learn in this field. – Harper - Reinstate Monica Jul 06 '21 at 13:48