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Old 24th Jan 2020, 3:42 am   #1
'LIVEWIRE?'
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Question Soldering to gold plated terminals

A few minutes ago I placed an order for 2 x 5-pin valve sockets. THese have Gold Plated pins/terminals. Can I solder successfully to these using a normal 40 watt iron and 60/40 Leaded solder?
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Old 24th Jan 2020, 4:26 am   #2
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Default Re: Soldering to gold plated terminals

I would! Gold solders easily.

It's true that depending on thickness of plating, gold can dissolve in the molten solder, leading to a brittle joint, but owing to the cost of the stuff, it's unlikely to be present in large enough quantities for this to be a problem.
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Old 24th Jan 2020, 9:12 am   #3
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Default Re: Soldering to gold plated terminals

Thanks, kalee20!
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Old 24th Jan 2020, 12:49 pm   #4
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Default Re: Soldering to gold plated terminals

Personally, I would strongly recommend 2% silver loaded solder for soldering to either gold or silver plated contact surfaces.
The silver helps to make a stronger joint due to the metallic chemistry involved.
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Old 24th Jan 2020, 3:12 pm   #5
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Default Re: Soldering to gold plated terminals

One job I was given as an apprentice at Marconi's was to de-gold gold plated contact pins, though now I wonder if it was de-golding as gold has a melting temperature of over a thousand degrees C. The reason for de-golding was because the gold made any soldering go brittle. Maybe I was just pre-tinning on top of the gold.
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Old 24th Jan 2020, 4:38 pm   #6
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Default Re: Soldering to gold plated terminals

Quote:
Originally Posted by GeoffK View Post
One job I was given as an apprentice at Marconi's was to de-gold gold plated contact pins, though now I wonder if it was de-golding as gold has a melting temperature of over a thousand degrees C. The reason for de-golding was because the gold made any soldering go brittle. Maybe I was just pre-tinning on top of the gold.
You're saying you were dipping the pins in molten solder? (and breathing in all the fumes as we all did in those days!).
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Old 24th Jan 2020, 5:37 pm   #7
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Default Re: Soldering to gold plated terminals

I'm assuming that the de-gold dip was hot solder, rather than hot mercury.... Hopefully, this wasn't a case of getting the apprentice to do the job that everyone else avoided!
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Old 24th Jan 2020, 6:21 pm   #8
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Default Re: Soldering to gold plated terminals

I'm with kalee20 on this. Just solder them.
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Old 24th Jan 2020, 6:33 pm   #9
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Default Re: Soldering to gold plated terminals

Quote:
Originally Posted by stevehertz View Post
Quote:
Originally Posted by GeoffK View Post
One job I was given as an apprentice at Marconi's was to de-gold gold plated contact pins, though now I wonder if it was de-golding as gold has a melting temperature of over a thousand degrees C. The reason for de-golding was because the gold made any soldering go brittle. Maybe I was just pre-tinning on top of the gold.
You're saying you were dipping the pins in molten solder? (and breathing in all the fumes as we all did in those days!).
Quote:
Originally Posted by turretslug View Post
I'm assuming that the de-gold dip was hot solder, rather than hot mercury.... Hopefully, this wasn't a case of getting the apprentice to do the job that everyone else avoided!

Yes hot solder and it seemed to remove the gold but the temperature would have been to low to melt gold so I am not sure what it actually did. If it did remove gold I should have scraped it off to supplement my apprentice pay! Did plenty of soldering with no extraction equipment when doing wiring and assembly. Not much H&S back then.
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Old 24th Jan 2020, 6:42 pm   #10
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Default Re: Soldering to gold plated terminals

Hot solder dissolves gold.

HP used to use a standard copper-nickel-gold plated finish on PCBs. The gold acted as etch resist.

The solder in the flow solder machines used to go off after time... it went grainy. We didn't know it but it was gold build-up from all the boards that had been through it. We dropped the bad solder out and put it in a scrap stillage and paid for it to be taken away.

Someone nicked the scrap stillage. What a prat! we all thought... but why nick that and not the brand new solder bars nearby? Huh? and then we found out that the bad solder was worth a heck of a lot more than the new stuff. We got burgled, but we made money out of it. We sold the scrap solder from then on instead of paying for its removal.

Gold takes solder very well indeed. Getting solder off gold if you made a mistake and let it flow onto contact fingers is the problem.

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Old 24th Jan 2020, 7:27 pm   #11
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Default Re: Soldering to gold plated terminals

In the 1970's I was working on a high reliability military project that made extensive use of custom IC's packaged in military flat packs in which all metal surfaces, including the leads (joggled for surface mounting), were gold plated. We just used ordinary tin-lead solder.
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Old 24th Jan 2020, 8:37 pm   #12
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Default Re: Soldering to gold plated terminals

Exactly as above, gold dissolves in molten solder. Heavily contaminated solder is weak.

But a quickly made joint (and solder will flow very readily) will be fine.

I've soldered many 'D' connectors with gold-plated solder-bucket pins, no problem. Standard 60/40 solder.
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Old 25th Jan 2020, 1:56 pm   #13
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Default Re: Soldering to gold plated terminals

Personally I would just use lead solder not the lead free as my personal opinion is its rubbish and does not take as well although it's getting harder to get hold of. Remember it's not the lead that's so much toxic it's the resin.
Silver solder is not really worth using unless you are using it in specific areas plus it costs a lot £50 plus for a small reel.
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Old 25th Jan 2020, 5:43 pm   #14
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Default Re: Soldering to gold plated terminals

I have a couple of manuals for my Tekreonix Type 453 oscilloscope, it has some ceramic tag- board with silver pads instead of actual tags. Here is what the regular manual has to say about them on page 59.
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The other manual is for the Department of the Army and has this on Page 2, right after the warning about not electrocuting yourself.
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and this on page 82.
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Old 25th Jan 2020, 6:09 pm   #15
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Default Re: Soldering to gold plated terminals

Ah. Yes. But that's different.

The reason for using silver-bearing solder (which is NOT tha same as 'silver solder') on the Tek tagboards is that normal solder will dissolve-away the silver metallising on the ceramic tag-strip, and you suddenly find that the solder balls-up because there's nothing for it st stick to.

Whereas if you keep attacking a gold-plated terminal with your iron, sure, you may dissolve away the gold, but there's still the base metal underneath which will take the solder. The gold has kept it all corrosion-free for you till this moment.
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Old 25th Jan 2020, 6:44 pm   #16
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Default Re: Soldering to gold plated terminals

Quote:
Originally Posted by kalee20 View Post
Ah. Yes. But that's different.

The reason for using silver-bearing solder (which is NOT tha same as 'silver solder') on the Tek tagboards is that normal solder will dissolve-away the silver metallising on the ceramic tag-strip, and you suddenly find that the solder balls-up because there's nothing for it st stick to.
Yes, this is why a lot of older Tek scopes were supplied with a small reel of "special" solder somewhere on the chassis.
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Old 25th Jan 2020, 9:13 pm   #17
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Default Re: Soldering to gold plated terminals

Quote:
with a small reel of "special" solder somewhere on the chassis.
Either lost or nicked by audio people that think it gives a better sound to soldered joints.
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Old 2nd Feb 2020, 9:39 pm   #18
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Default Re: Soldering to gold plated terminals

Quote:
Originally Posted by kalee20 View Post
I would! Gold solders easily.

It's true that depending on thickness of plating, gold can dissolve in the molten solder, leading to a brittle joint, but owing to the cost of the stuff, it's unlikely to be present in large enough quantities for this to be a problem.
Until a few years ago (working within BAE on avionics) I was responsible for highlighting those parts that had to be de-golded prior to assembly. It was basically a final plating and consisted of the traditional tin/lead mix. This rule was applied to ALL PCB mounted parts. We avoided pure tin as well because of the known problems.

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Old 3rd Feb 2020, 9:14 am   #19
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Default Re: Soldering to gold plated terminals

Space grade qualified parts are supplied with a gold flash on the leads to prevent tarnishing compromising solderability. All parts are de-golded prior to assembly to prevent solder/gold brittle intermetallics. If final assembly is not within a short time (I forget how short - certainly measured in hours) they have to be stored in an inert atmosphere of dry nitrogen in a desiccator.

Even if the assembly technician has been to an ESA course and is therefore qualified, ESA still insists on solder joint cross sections to be used in the final flight model.

Basically no service calls, so the whole space industry is rightly founded on rigid procedures to ensure reliability.

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Old 3rd Feb 2020, 11:43 am   #20
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Default Re: Soldering to gold plated terminals

Gold is not always a good thing in our (ie this forum) business, not just because in wrecks solder joints.

Many years ago, I had to find out why a unit of a large computer would fail in the field, only for the faulty unit to work perfectly once returned to the factory.

Turned out to be a VLSI chip in a pin grid array package with gold plated pins in a tin plated socket. The ride back to the factory cleared the resulting bad contact, all our shake rattle and roll treatments to try to get the fault to show were just improving things. The device spec called for tin plated pins to match the socket, but I guess goods inward folk thought gold was better than tin, so let them through.

Having dissimilar metals in contact is not a good idea, even if one of them is gold (unless contact pressure ensures a gas-tight seal). Something to be kept in mind when updating your hifi cables for super duper gold plated ones, Iíve seen gold connectors on aerial cables, but not on Belling type sockets.

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