Back in the vacuum tube era, American (and at least one Japanese) manufacturers of professional and military electronics (Tektronix being the most prominent) used ceramic tag strips to mount resistors and capacitors. These had silver bonded to the ceramic by a sintering process much the same as for making hybrid microcircuits. After silvering, which is microscopically thick, they tinned the strips by dip- or hand- soldering.
Silver loaded solder should be used in repairing/restoring such equipment, as normal tin-lead solder will cause the tag strips to fail. The solder that was used in the factory and in maintenance depots back then was loaded with 3% silver, but with the normal ratio of tin and lead. The 3% silver prevents the silver/ceramic bond from failing. Note this is NOT "silver solder" nor is it modern lead free solder.
3% silver loaded tin/lead solder is not stocked by electronics firms, although 2% silver loaded solder is.
Does anyone know where I can but the proper 3% silver tin/lead solder?
In restoring old equipment back to factory standard, I have to assume that somebody in the past may have used ordinary tin-lead solder once or twice, so some weakening of the bond has already been done. I don't want to make it any worse.
Silver loaded solder should be used in repairing/restoring such equipment, as normal tin-lead solder will cause the tag strips to fail. The solder that was used in the factory and in maintenance depots back then was loaded with 3% silver, but with the normal ratio of tin and lead. The 3% silver prevents the silver/ceramic bond from failing. Note this is NOT "silver solder" nor is it modern lead free solder.
3% silver loaded tin/lead solder is not stocked by electronics firms, although 2% silver loaded solder is.
Does anyone know where I can but the proper 3% silver tin/lead solder?
In restoring old equipment back to factory standard, I have to assume that somebody in the past may have used ordinary tin-lead solder once or twice, so some weakening of the bond has already been done. I don't want to make it any worse.
This is interesting.
I use only MG Chemicals SAC305, 96.3% Tin, 0.7% Copper, 3% Silver from Amazon.
May not work for your application, but works great and mix well with older solder.
Cheers,
Brice.
I use only MG Chemicals SAC305, 96.3% Tin, 0.7% Copper, 3% Silver from Amazon.
May not work for your application, but works great and mix well with older solder.
Cheers,
Brice.
I don't know of lead/tin/3%silver but there is Multicore 96S which is 96%Tin/4%Silver and is useful for stopping of erosion/dissolving of silver platings as in your case.
Dan.
Dan.
Thanks. But I don't want to use lead free solder. As far as I can ascertain, lead free solders such as this have a significantly higher melting point, which on ceramic terminal strips cancels out the protective action of the silver. According to Tektronix factory documentation, the 3% silver level is an optimum - less than 3% and the solder dissolves out the silver sintered to the ceramic, weakening the bond, and over 3% the raised melting temperature and loss of eutectic behavior causes problems. But, to be honest, how critical it is I don't really know. If I can get the correct 3% silver loaded solder, I'll use that. If I can't, I'll continue to use 2% silver in tin-lead, which is readily available.
It's also important to use a solder with a conventional flux intended for electronics, not jewelry, metalwork, etc. With ceramic terminal strips, after soldering in a new component, you need to clean the flux off with something compatible with electronics, such as Electrolube Safewash. Otherwise the insulation properties of the glazed ceramic are degraded. And anything the least bit sticky should not be used or left, as this is ventilated vacuum tube equipment, which collects dust and pollutants.
Keit, perhaps Cardas Quad Eutectic is what's needed. I've used it and will happily do so again. The stuff is expensive, but just might be worth the cost. The eutectic alloy (Sn/Pb/Ag/Cu) flows well and makes strong joints.
Everything is fine. I used 2% silver solder on my Tektronix 575 Curve Tracer and it's all good.
What you're doing is joining glass to metal, something done with lightbulbs, tubes, neutron generators, etc. Much research has been done on this subject. For example, neutron generator tubes are designed for a certain life span that is many decades long, so the glass to metal seal cannot leak. Fortunately for audio equipment, this life span is not as long.
If you feel lucky, the big box hardware stores sell a solder that contains silver. Sure to last longer than many of the other components contained in you audio amplifier.
What you're really trying to avoid is the solder creeping and causing shorts with other components. It takes a lot longer for this to happen than I have left on this Earth, so I'm going to relax and have a beer, listen to some music.
Thanks for the link.
Funny it does NOT say how much silver it contains.
Nor gold for that matter.😕
These are just ordinary modern-type lead free solders, except for one type for which they don't give the alloy data.
If I want ordinary lead free solder, I can buy that locally, without the price loading and magic audio properties of hi-fi marketing. When I work on audio gear not using ceramic tag strips, I use standard tin-lead eutectic, it's cheap, available in any electronic parts store, does the job best of all, and here in Australia I don't need to give a fig for the silly European Lead Free Directive.
Here I need silver loaded solder that is otherwise standard tin-lead with a standard electronics-type flux.
Yes, they certainly did, so that technicians wouldn't be tempted to use standard solder and ruin the ceramic tag strips.
The trouble is, they didn't always include the little roll, and sometimes they did, but over the years it has gone missing. And other manufacturers that used the same tag strips never included a little roll of solder.
The last three items of test gear I have restored had the little rolls missing. I made replica white plastic reels on a mini-lathe.
Quite a bit of Tektronix gear has come on the market that is ex-military. These quite often don't have the little roll. Perhaps Tektronix realized that military technicians were "properly" trained, would be supplied with the correct solder, and would not be temped to use the wrong stuff. Tek oscilloscopes they sold to civilian customers seem to have always had the little rolls inside. But not the more specialized gear, such as precision oscillators, inductance meters, and the like.
And more equipment has gone on the market via radio hams, whose ability to solder is not always the best, and they probably didn't bother about using the correct solder. So the bond may be already weakened. I don't want to make it any worse.
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There is only one big box hardware outfit here in Australia - Bunnings, owned by what was originally a local farmer's cooperative. There was another, American owned, but they went broke - didn't understand the local market.
Bunnings only have regular tin-lead solder, food grade lead-free, and a large range of plumbing solder (paste stage, non-eutectic) sticks.
Light globes and vacuum tubes use what is known as a "housekeeper seal", or alloys chosen to have a tempco nearly the same as the glass they use. They don't use solder. But you're right about a lot of research done.
They do have a datasheet.
http://www.mundorf.com/english 1.1/Broschuere Einzelseiten/MSolder Loetzinn.pdf
They claim 3.8% silver. The first gold version doesn't seem to have any gold in it, or... traces?
You DON'T want any gold in solder. It causes embrittlement. Mundorf is just being a snake oil merchant for the multitude of gullible in the audio market.
At one stage, during the earlier 1960's, a few quite respected manufacturers had their entire printed circuit board traces gold flashed, because it looks pretty, and lends an impression of quality. Surprisingly, even Hewlett-Packard fell for it. They soon stopped - the rate of returns due to "dry" joins went up enormously.
Some manufacturers, eg T&N in Germany, gold plated the component side only on their double-sided boards and just tinned the solder side. Looked nice and pretty without too much trouble with dry joints.
I quote from the datasheet:
The MSolder Silver provides a superior conductivity by virtue of 4.5% precious metal "
What we are talking about here is 0.0001% of just about nothing in terms of any circuit. A solder joint might contribute 0.001 ohms at most in a circuit that at least contains many ohms in the components, even in the power stage. It's not even anywhere near as good as claiming you can get better fuel consumption in your car by giving the paint an extra smooth polish to lower wind drag.
"and guarantees the excellent sound characteristics of components containing silver."
If you believe that, you believe in fairies and pots of gold at the end of rainbows.
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Yes it does. Aerospace rules require that gold plating be scraped off, prior to soldering. Brittle joints in a high vibration environment are asking for trouble.