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Brazing of Gold-Plated Copper

10/26/2010 7:39 AM

Hi all

I wonder if there's any experience out there concerning brazing of copper components (up to say 20mm diameter) with a 0.5micron gold plate?

In my case the parts are electrical contact pins; they could see a continuous 150degC in normal use and also experience some serious vibration. The pins would be brazed to copper busbar.

Would the gold maybe interfere with the chemistry, weaken the joint, have other undesirable effects? Would a sliver plate be preferable on the pins from the joining POV?

Any advice or shared experience much appreciated

Best

Dan, London UK

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Power-User
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#1

Re: Brazing of Gold-Plated Copper

10/26/2010 8:49 AM

Dan can you not braze-solder-thread the parts first then plate them after you test for joint integrity. Gold/Silver plating kits are avaiable at good prices.

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#2
In reply to #1

Re: Brazing of Gold-Plated Copper

10/26/2010 8:56 AM

Hi thanks for the idea

subsequent plating is probably not feasible as we are OEM and the user would want to purchase useable contacts from us that he could braze onto busbars. My guess is that the user would not be happy taking on the plating as well however I will throw the idea over...

Thanks

Dan

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#3
In reply to #2

Re: Brazing of Gold-Plated Copper

10/26/2010 12:49 PM

The thing about brazing the components after they are plated is to maintain the coating under heat.


FYI 18K yellow gold has a melting point of 1675 degrees Fahrenheit and 14K yellow gold has a melting point of about 1550 degrees, Pure copper is 1983 F and you need to get near that to braze.. However gold alloys may give you better temps Silver is 1760 F

so I think a small electrolytic kit seems best path...

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#4

Re: Brazing of Gold-Plated Copper

10/26/2010 4:18 PM

Talk to your local jewelery repair shop. They may recommend a gold solder. That way the integrity of the gold will be intact, the soldering will be done at the temps the gold solder works at. Works fine for them, should for you.

Otherwise, you are going to burn off the gold, will look bad. Normally, silver solder is used for what you are doing. It's melting point is below the brass or copper, does a good job.

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#5

Re: Brazing of Gold-Plated Copper

10/26/2010 10:49 PM

You should never plate copper with gold directly, especially if they are exposed to elevated temperature. They will inter-diffuse and create an alloy at the interface. Always plate a nickel diffusion barrier between the two metals. 0.5 microns is a thin plating that will disappear rapidly at elevated temperature. That being said, your pins can be soft soldered or silver soldered to your copper bus depending on strength and temperature requirements.

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#6

Re: Brazing of Gold-Plated Copper

12/01/2010 1:01 AM

Ok 20mm is quite large. so you can mig weld, there is a wire called silicone bronze made to replace braising, if you need fine work, same thing and TIG weld, as for the disurbed finish, you can get paint on nickle and gold plate kits to refinish the join. simple.

Archie

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#7

Re: Brazing of Gold-Plated Copper

12/01/2010 8:55 AM

In many applications silver plating provides adequate protection and solderablitiy. The biggest problem with silver plating is that it reacts with sulfur in the air and tarnishes. The problems with tarnish are mostly cosmetic, but if the customer doesn't like the appearance, you may have a problem. Both gold over nickel as well as silver are good choices.

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