Soldering ultrafine wire

[Richard Head]

What's "Purine"?

[Pjotr]

Purine by itself is a basic raw material used for many purposes. One of them is a classic non aggressive solder grease.

[Ian.M]

The MSDS for  CFS/Griffon's Purene paste flux tells me it contains Zinc Chloride, so its fairly aggressive.

I wouldn't use it for fine wires because of the risk of corrosion problems in high humidity environments if its residue isn't totally removed.   A good liquid R or RMA flux would be a better choice compared to any paste flux as the hard rosin residue is close to inert at room temperature and as long as you avoid RA fluxes with metal salts or chlorides, the risk of chemical corrosion is low.

[Pjotr]

I wouldn't use ultrafine copper in a high humidity environment anyway. Have used this method without problem and joints made 20 years ago are still alive and kicking But maybe there are more modern solutions? I don't know, and didn't come up in this thread. A very experienced technician at the machine lab of the Delft University pointed me to this method long time ago, when I had to do about 100 2KW/400Khz transformers with ultra fine multi stranded litz wire.

Did try many modern fluxes, they do not work if you do not carefully remove the enamel mechanically on forehand. And most "solder-able" enamels are in fact not so solder able in reality.

[ian.rees]

Received a new roll of Edsyn "Sn60PbCu2 FSW32" solder from Element14 today - works great!  I kept a molten bead of solder over some of the wire for a minute or so and didn't have any problems with the wire dissolving away.  Thank very much!  -Ian-

[hr8799]

Hello ian.rees,

I just stumbled upon this thread and am very interested to learn how things turned out.  I've been toying with the idea of repairing 214 (and 218) coils and would benefit greatly from hearing about your experiences.   Were you able to successfully rewind a coil and end up with a working circuit with the appropriate resistance?   

I would like to give this a try (I have 6 or 7 coils that need work)!

[N2IXK]

I work with similar fine magnet wire when wiring up strain gages for force measurement.  I use the thermally strippable wire, dip the end in a liquid rosin flux, and tin the end in a solder pot. Then trim back the tinned end as needed for the specific connection to be made.

[ian.rees]

Hi hr8799,

    It is still a work in progress (has been probably 9 months worth of occasional evenings and weekends), but I can currently re-wind 214 coils and don't expect 218 ones to be too much additional work.  The re-winding is a bit more nuanced than I anticipated at the outset, beyond getting the wire tension right.

Soon I hope to start selling re-wound coils (through Accutron repair people like Rob Berkavicius, who has been immensely helpful in this) on an exchange basis, and once I've recouped the cost of the project my plan is to do a series of blog posts about the project.  Thanks for your interest!  -Ian-

[hr8799]

Very cool!  I am looking forward to reading your blog posts, as I'm sure many others are.

My biggest roadblock at the moment is obtaining the wire.  It looks like everyone wants you to buy $1000 worth the stuff.  I just want a small amount to experiment with.  I may use something "close" to setup the winding apparatus.  I never imagined it would be so expensive.

Bets of luck!

[ez24]

I used very fine sandpaper. Pinch the wire between two pieces of sandpaper and pull it out. Repeat until the wire is shiny all round. It's a real pain to do both ends of a dozen pieces of wire (plus re-do all the wires that snapped because you squeezed the sandpaper too hard).

I also used very fine sandpaper. I put the wire on the paper and pressed down on it lightly with my finger and pulled lightly on the wire.

The wire made a great security perimeter wire because it would break so easy.  But I did not solder it. I made connection with a small spring