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Can we do Electroless Silver Plating on Gold?

2007

Hello,

My name is Gil Bruso. I have a question regarding electroless silver plating. I am currently electroplating silver onto a gold circuit trace. This is a long process and can become a bottle neck in the process flow. I am looking for a process that would be possible to do in some other bath equipment that can be scaled up easily. The articles I have seen so far call electroless silver an immersion plating process where the silver replaces copper on the circuit. Does this process also work on gold instead of copper? We currently benefit from an increase of surface area as seen with electroplating. Will electroless silver work? How does immersion plating work for this process? I also need a source for the chemistry.

Thank You,

Gil

Gil Bruso
Medical Electronics Manufacturer - Simi Valley, California USA

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Sorry, Gil, you cannot do it that way. Immersion silvering relies on the fact that silver is more noble than copper; the copper will dissolve into the solution and silver will plate out onto it as a simple product of their position in the electrochemical series. Gold is more noble than silver and will not replace it in solution.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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Ted is right seen from a chemical point of views, but if you buy a commercial immersion silver, the process actually happen. The reason is that the producer also ad some chelators, which make the silver "more noble" than gold.
I found out the hard way, lost face to some colleaques explaining that immersion silver would not cover the gold.

Bo Kønig
- Odense, Denmark
2007

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Thanks, Bo. I could not find anything about this in a 15-minute web search. If you have any further info on it please let us know. Also, my understanding is that immersion silver is one of the RoHS-compatible alternatives to HASL for preserving the solderability of copper circuit traces, and may sometimes also be used as a contact surface for lower-end membrane switches, etc. Does it have additional applications in the PWB industry? Thanks again.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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You are very welcome Ted. I only know this little because I tried. We used this immersion silver as replacement for HAL back in 2000 because of RoHS.
Gil are you aware that an immersion process are indeed not the same as electroless ?
When the immersion silver replaces the metal from the surface, then the process stop, once the surface is covered. With electroless the process stop once you remove your product. This means that immersion silver will be limited in thickness.
As for source of chemistry you can contact the supporting advertisers, I have knowledge of Atotech and Macdermid and both are good, there are probably many more.

Bo Kønig
- Odense, Denmark
2007

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First of two simultaneous responses --

Thank you both for your input. My original goal was for electroless silver but I was told that it wouldn't work on gold. Maybe my source had it wrong. What can you tell me about an electroless silver process over sputtered gold? Our experiment would benefit from a thick silver layer.

Gil Bruso
- Northridge, California, USA
2007

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Second of two simultaneous responses -- 2007

I have found on the net suppliers who claim to have an actual electroless silver (not an immersion one),

you could google "autocatalytic silver plating" and find out.

Please let me have feed back if you had any results.

Daniel Livshitz
plating on plastics - Tel Aviv, Israel

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April 12, 2011

Hello
There are processes in the market that can be used for depositing Silver on Gold. It is autocatalytic silver plating and as it's a chemical process, it's uncomplicated. It gives conforming layers and can be used for applications with very thin Silver layers on complicated geometrical structures. There is also good experience of using it for applications on Gold.

Best Regards

Lena Hultin
Plating Technology supplier - Norrtalje, Sweden