Ultrasonic Soldering Iron

Solder to stainless steel, ceramic, or even glass

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Ultrasonic Soldering is a unique process that uses cavitation to break surface oxides and allow two normally unsolderable surfaces to be bonded. These specialized devices are sold for thousands of dollars. This project aims to create a cheap and effective ultrasonic soldering iron that anyone can build at home.

CAD is released under the MIT license. Not sure if the MIT license even applies to CAD, but the point is, you can do whatever you want with the CAD.

  • Potential problems

    Hunter Scott05/25/2016 at 21:54 0 comments

    After reading some more about ultrasonic conduction (including some comments on this project page and on the Hackaday blog post on this project), I'm concerned that not very much vibrational energy will actually get to the heating element tip. Here's why:

    Notice how much space is between the top of the transducer and the bottom of the threaded adapter. I think for this to work really well, I'm going to need to change two things:

    1) The threaded adapter should be flush against the top of the transducer to get good mechanical conduction

    2) The threaded adapter should be made of metal. This will present a much closer mechanical load impedance to the transducer. Some people were worried that the heating element might melt the adapter, but I actually don't think it will. The heating element doens't get too hot that far up, and the original construction had the heating element directly connected to plastic too. I'm hoping that making that part out of metal won't screw up my thermal conduction and keep the tip from getting hot enough as it conducts heat away into the large thermal mass of the transducer.

    So now the question is, how do I make that part? If I had a real shop, I would just lathe it out of a single piece of cylinder stock and then use a die to thread it, but I don't have a lathe. So I can either get one (mini one from Harbor freight maybe?) or pay somone to machine it, or 3D print it. The cheapest place to 3D print it would be Shapeways, which would be $51 in 12 days. I think I'll get someone to machine it for me, since it's a stupid easy part to make. Will probably be cheapest that way. I would do it myself in TechShop [I miss machining stuff :( ] but I can't pay $150 a month for that.

  • Mounting the transducer

    Hunter Scott05/25/2016 at 21:40 0 comments

    I drew a little press fit adapter to connect the ultrasonic transducer to the iron. I used Fusion 360 again, and it went fairly smoothly. I had to re-do some work when I wanted to change the diameter of the main sleeve part. I feel like there should be a way to change stuff like that without having to do the same work twice, but I'm not sure how. Anyway, here's the adapter I printed on a Lulzbot mini:

    The solder tabs get screwed down on the sides there (those will also make contact with the wires to the transducer driver). And the entire assembly gets connected to the iron with 3 screws that go in the same holes that the original heating element went in.

  • Attaching the heating element

    Hunter Scott05/04/2016 at 06:39 0 comments

    To attach the heating element to the transducer, I ended up 3D printing an adapter. It turns out it's extremely hard to find M10-1.0 bolts. I only found some that were used on some cars. So instead I modeled a little adapter block in Fusion 360 and had it printed by Fictiv. I couldn't print it myself because this part has threads that need to be accurate.

    One side has the M10-1.0 thread and the other side has 3 screw holes to attach the heating element. I probably should have made the holes for the screws slightly larger. I also should have used threaded inserts instead of screwing directly into the plastic. The plastic held up ok, but it started to crack and lift in some areas and I'm hoping it will survive the 40W of ultrasonic energy it will experience. If I still had access to a machine shop, I probably would have made this piece out of aluminum. That way I wouldn't have to worry about heat leaking from the heating element mounting holes into the adapter, and I wouldn't have to worry about it failing during use. This piece would be pretty simple to make with a lathe, drill press, and threading die.

    I thought about it more later and realized that I could actually make this part without support material by using a threading die like this:

    Here's the whole assembly so far:

  • The approach

    Hunter Scott05/04/2016 at 06:27 0 comments

    The plan is to take apart an existing soldering iron, install an ultrasonic transducer, and then somehow put it all back together. Here's the parts I have so far:

    A 40W ultrasonic transducer. This was originally meant to be used on an ultrasonic cleaner. I got it from eBay and it came with a driver circuit that is powered by 120VAC. It's got an M10-1.0 threaded hole in the middle. The "manual" that came with it says not to drive it without a correctly matched load. Basically they don't want you to try to run it without there being any water in the ultrasonic bath. If you do, it can get hot, overheat the power supply/driver and destroy the transducer. Of course, I'm going to be doing exactly that and never driving it with a load. So to keep it from overheating, I'm going to install a momentary normally off button on the handle of this thing somewhere so you can heat the solder without ultrasound and then engage it when you need it.

    The soldering iron I got is a Weller. It doesn't have temperature control or anything. I just got it from Home Depot and it plugs straight into the wall. This is actually perfect, because I can splice into that connection to power the ultrasonic transducer. This iron also comes apart easily and the heating element is connected with 3 screws, which makes it easy to move elsewhere.

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Richard Mcfarlane wrote 02/13/2018 at 15:09 point

Ultrasonic Transducer drving schematic ?

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Moritz Walter wrote 05/11/2016 at 05:41 point

Very cool project! Make sure you don't fry your periosteum while soldering the unsolderable ;)

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Hunter Scott wrote 05/11/2016 at 18:31 point

Yeah, I was thinking about that the other day. I should probably try to find the OSHA limits on conducted ultrasound into humans. 

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Peter Walsh wrote 05/09/2016 at 17:44 point

I've put up a large body of information on ultrasonic transducers and the relevant circuits on my project.

If you go through the logs, you might find some info useful to your project.

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Hunter Scott wrote 05/11/2016 at 18:29 point

Wow, this is great, thanks a lot!

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