Copper going away at 350° ?

[Bernhard]

I remove the insulation of 0,18mm transformer wire with the solder iron and from 350° to 400°C the wire starts to get thinner and just disappears.

Is that normal ? I used the same wire from the same spool before and did not notice anything.

[AndrewT]

It could be copper dissolving in the solder.
The temp is a bit high.
Try 280 to 320degC for bit temp.
What solder are you using? Do you know which flux is used?

[Bernhard]

It is SN96.5 AG03.5 even at 300° but not as fast.
With normal solder without the silver it starts at 425° but slowly.

[gareth]

Strange as copper has a maximum working temperature of 800 degrees C

Gareth

[Charles Hansen]

Originally posted by Bernhard
I remove the insulation of 0,18mm transformer wire with the solder iron and from 350° to 400°C the wire starts to get thinner and just disappears.

Is that normal ?

Yes, this is normal.

Copper will dissolve in solder. The higher the temperature, the more quickly it happens.

We use a solder pot to remove the enamel insulation from the litz-type Cardas wire. If you keep the temperature low and work quickly, there is no problem. But if the temperature is high and/or you leave the wire in the solder too long, then the copper becomes thinner and thinner until it disappears.

[Conrad Hoffman]

I always thought the reason for SN62 was to reduce the tendency of fine copper wire to dissolve. Tektronix used to specify it to prevent damage to their plated ceramic terminal strips in the old scopes. It actually comes in a variety of different amounts of silver- I'm holding a roll of SN62.5, with 36.1% Pb and 1.4% Ag. A tin-silver solder is a lead free solder, but I don't know if it has the same copper preserving properties due to the higher temperatures required.

[dnsey]

I can't say that I've encountered this problem, but I'd try 'Savbit' or similar copper-loaded solder, designed to minimise erosion of plain Cu iron bits.

[jneutron]

Charles is right on. The copper is dissolving into the melt.

Time and temperature is the reason. More time, more temp, more dissolving.

33 AWG is very small wire..using the liquid solder to remove the insulation will certainly give you problems.

I'd use a razor to scrape the insulation off under a microscope. Or, chemical/abrasive means.

I tried to soldercoat a 1 cm by 2 cm copper braid using a solder pot, and found that half the wires were gone in under 2 to 3 seconds. The surface area of the fine wires is what's biting you.

Using a copper loaded solder will slow it down a bit, but that also tends to force you to raise the temperature to compensate the alloy type, so hand soldering tends to not gain much.

Cheers, John

[Bernhard]

Thanks, I used the standard non silver solder at 320° and everything is ok.