This blog is NOFOLLOW Free!
Print This Post Print This Post

Using the Induction Heater – Solderng


In my last installment I briefly mentioned that soldering copper is difficult with induction heat. That is true unless one uses a flux concentrator. Well lo and behold we had a kit customer who was interested in heating small parts which also requires a flux concentrator so I took some time out to experiment.

Flux concentrator 05

A flux concentrator is simply something that is magnetic and suitable for the operating frequency that concentrates the magnetic flux into a specific area. Pictured above is a simple concentrator that I made using a broken transformer core. This is attached to the output of a Roy heater. The white-hot object is a 1/4-20 steel nut. I melted the nut right after this photo was taken!

The flux concentrator can concentrate the magnetic flux into a very small area which is what is needed for heating highly conductive metals such as copper and brass.

Flux concentrator 10

Above is a photo of a brass bolt that has been melted by the flux in the gap. The bolt has been repulsed by the high magnetic field and was physically moved out of the gap before I could take the photo. Power in this photo is about 500 watts.

Flux concentrator 08

Here is a photo of a heavy duty crimp-type butt splice in the gap. With about 500 watts input to the heater, this splice is heated from room temperature to soldering temperature in about 15 seconds.

Other things to note in the photo include the Litz wire used to wind the work coil. This wire, which is made up of hundreds to thousands of individual strands Has much less resistance to RF current than conventional wire because of the skin effect. Current flows on the surface of hundreds of little wires instead of one big one. This wire is available from Fluxeon®.

Flux concentrator 11

Here is another shot of the flux concentrator. The gap has been opened up so that I can fit a 3/8″ copper coupling in the gap to demonstrate copper sweating.

Flux concentrator 12

Here is the soldering operation being conducted.

Flux concentrator 13

And the finished product. Note the complete lack of staining or other evidence of heat. Also note the almost perfect little bead of solder. Notice that the copper tubing is in contact with the plastic tape holder (the tan object in the background) but the copper isn’t hot enough to melt the plastic. That’s how fast induction heating can be.

Flux concentrator 14

The kicker: From room temperature to soldering in 7 seconds! That’s with about 700 watts input to the heater. Probably half that makes it to the work.

While Fluxeon® does not (yet) offer a soldering heater, you can easily make one from the kit that we offer. When you order a version 2.21 kit, be sure to note that you want to do copper soldering. You will be supplied with a different output transformer. This transformer has 20 turns of Litz wire on the secondary instead of the 2.5 turns of welding cable used on the general purpose heater. You may also buy more litz wire and ferrite cores for the flux concentrator. Contact me or Garett, for more info.

Posted by neonjohn on November 12th, 2010 under Cool Stuff, Induction heating

10 Responses to “Using the Induction Heater – Solderng”

  1. al Says:

    this is what i want but bigger, and capable of melting a 1inch diameter by 1 inch length solid rod

  2. neonjohn Says:

    Patience, my friend. We’re working on it. And when it’s done it’ll be affordable.


  3. Cedric Says:

    This is very interesting. Could you please give more details ? As in the number of turn on the ferrite and other advices… Cheers.

  4. neonjohn Says:

    Hello Cedric,

    We’ve greatly refined the flux concentrator since I wrote that article. Fluxeon now sells a dedicated soldering station that is also capable of brazing small items. We’ve just introduced a 2500 watt unit so brazing should be possible for larger objects.

    Stay tuned. My next blog post will be an update to the flux concentrator, showing what we sell and how to DIY.


  5. Norm Matzen Says:

    I just purchased a ferrite core and Litz wire to make a flux .
    I want to place a rifle cartridge case into the flux concentrator gap and heat the neck region only to about 600 deg F in seconds to anneal it. I shoot long range bench rest, and we re-load cases many times and need to re-anneal them.
    Can you give me some hints on power levels and geometry to do this?


  6. neonjohn Says:

    Hi Norm,

    I’m an ex-competitive shooter (eyes went) so I know what you want. In fact we sell an annealer called the Annie. It includes the gapped ferrite flux concentrator, a low powered Roy (around 600 watts, I think), a built-in timer and a foot switch.

    We had to turn the power down because the annealer was too fast to achieve uniformity. The power level is set to run a cycle in about 2.5 seconds on a .308 brass.

    I designed the heater but my partner Garett Churchill refined the geometry and power levels. If you’ll drop him a note at, he’ll help you out.

    I think that you’ll find that buying an Annie is cheaper than trying to put all the pieces together yourself.

    Our website is woefully out of date. We just hired a web guy to update it and keep it up to date. The Annie and its specs will appear shortly.


  7. Norm Matzen Says:

    I didn’t pay attention to your comment about the Annie and its specs not being on the web site yet. Could you tell me the price and pertainant details?



  8. Jeff Says:

    what type of transformer did you get that core from?

  9. neonjohn Says:

    We have them made in China. They’re for sale from Fluxeon and soon from us (, the company that just split off from Fluxeon. They’re called UY cores, formula 40 I think. Amadon associates might have them here in the US but they’ll be expensive.


  10. Interesting Animals Says:

    Thank you for sharing such a useful and helpful tips for the community. Keep it up!

Leave a Comment

Comments links could be nofollow free.


  • Meta