Gold or silver plating soldered boards?

[Petter]

Is it possible to (ideally) chemically gold plate boards after they have been soldered? Another cool option would be to Copper or silver plate the same way, but gold is more robust.

From my high school chemistry I seem to recall that gold is fairly low on the electrochemical table and thus chemical gold plating should be possible, at least on the copper. What then about the soldered pad?

Any ideas?

Petter

 

[MRehorst]

If the board has been soldered, then the plating chemicals will either plate or corrode the leads of the parts you've soldered down. It might make a real mess of switches and connectors, if there are any soldered to the board. I'd worry about plating chemicals trapped under components not getting thoroughly washed out. That isn't going to improve reliability a bit...

Many plating processes involve applying voltages to the surfaces to be plated. This could cause some real trouble for electronic components.

Most PCB houses can apply gold plating to boards they manufacture. It costs a little more, but if you really want it, just specify it when you order your boards.

Most of the time there isn't much point because solder mask will cover the copper and protect it. If you get gold plating, most of it will be covered by solder mask unless you open up the solder mask layer (or delete it) in your layout files. Would having exposed conductors that are shiny gold be better than having insulated, nonshiny conductors?

MR

 

[tiroth]

I've been told silver plating is a reasonably inexpensive alternative to hot air solder leveling (HASL). All the prices for gold I've seen were astronomical for small orders.

 

[dice45]

Petter,

the German company Kepets (website under construction, has a link with an email adress) sells a wide variety of PCB manufacturing reagents. Among those is a bath for tin-plating and silver plating. Both bathes work without applying voltage and by chemically depositing only. I have tried them out, both work fine. I would not recommend to use them after components have been soldered; they are meant to plate the PCB before soldering and to enease soldering.

However i would be reluctant to sliver-plate amp PCBs. My experinece with cables shows that pure copper has better sonics than tin- or silver-plated one.

 

[jackinnj]

HP (now Agilent) gold plates their boards, fwiw. Silver is a great conductor, but oxidizes very quickly. If you want to protect the board from oxidation, there are any number of coatings some of which are easy to apply and don't require a laminar flow hood.

 

[mrfeedback]

I'd Like To Try It Too....

In past discussions with a jeweller friend, I am told that it is not possible to easily electroplate onto Lead (Pb) - solder.
A jewellry making process is to make a lead die, and then electroform a thick deposit of copper, which can then be peeled off - no adhesion.
The other obstacle is any remnants of the electroplating salt soloutions used, as already said.

Eric.

 

[fdegrove]

PLATING

Guys,

As Dice45 pointed, out plating after soldering is not a task you want to get in to.
As far as cunductivity goes:silver is a better conductor then gold and even when oxidized conducts very well.
Gold,on the other is a worse conductor then copper and when oxidized does not condict too well.
If oxidation is your main concern you can tropicalize your circuit whith some special spray-on product.
How all that is going to sound is another story...


Greets,

 

[haldor]

Re: PLATING

Gold,on the other is a worse conductor then copper and when oxidized does not condict too well.

I am not a proponent of gold plating PCB's except for card edge finger contacts, but I have never even heard that gold can oxidize. What is your source of information about gold oxidizing?

Phil

 

[Steve Eddy]

Re: Re: PLATING

I am not a proponent of gold plating PCB's except for card edge finger contacts, but I have never even heard that gold can oxidize. What is your source of information about gold oxidizing?

It doesn't oxidize under normal conditions. You can get it to oxidize under high heat and pressure, but the oxide is unstable and quickly reverts back to metallic gold.

Suffice to say that it won't oxidize under any conditions existing in audio systems.

Now, gold can interdiffuse with other metals. So for example a thin gold plating over a copper substrate can result in the gold interdiffusing with the copper which effectively brings the copper to the surface and the copper can oxidize. That's why much of the gold plating in the electronics industry is done with a nickel barrier between the gold and the copper.

se

 

[haldor]

Re: Re: Re: PLATING

Now, gold can interdiffuse with other metals. So for example a thin gold plating over a copper substrate can result in the gold interdiffusing with the copper which effectively brings the copper to the surface and the copper can oxidize. That's why much of the gold plating in the electronics industry is done with a nickel barrier between the gold and the copper.se

Hi Steve,

That explains why cheap gold contacts corrode so easily. We used to make a retail (food market) product that used telephone modular jacks for connection to a RS485 mutli-drop network. Those gold plated copper wires in the modular jacks would corrode at the first hint of moisture. Use to have major problems keeping those jacks working in fish departments.

Phil

 

[Steve Eddy]

Re: Re: Re: Re: PLATING

That explains why cheap gold contacts corrode so easily. We used to make a retail (food market) product that used telephone modular jacks for connection to a RS485 mutli-drop network. Those gold plated copper wires in the modular jacks would corrode at the first hint of moisture. Use to have major problems keeping those jacks working in fish departments.

Yeah, water around any current carrying contact isn't good.

By the way, I did some poking around and found this piece on the issue of gold and oxidation if anyone's interested.

<a href="http://matsci.uah.edu/courseware/mts501/reports/sschwitalla.html">Why is Au Found in Nature in the Metallic Form and not as an Oxide?</a>

se

 

[haldor]

However i would be reluctant to sliver-plate amp PCBs. My experinece with cables shows that pure copper has better sonics than tin- or silver-plated one.

Heretic! How can you possibly suggest that the less expensive solution that is overwhelmingly preferred by engineers world wide could possibly have better sonic qualities. This flies in the face of all audio tweaker lore. Sheer deviltry

After all, everyone knows that the best (most expensive) way to dampen vibration is fill back the solid platinum cases with powered diamonds (gem quality of course). I find this also increases thermal conductivity wonderfully well. Hmm... actually diamond is a great conductor of heat, better not mention this on Audio Asylum.

Realityists! What can you do with them.

Phil

 

[haldor]

Heretic! How can you possibly suggest that the less expensive solution that is overwhelmingly preferred by engineers world wide could possibly have better sonic qualities. This flies in the face of all audio tweaker lore. Sheer deviltry

After all, everyone knows that the best (most expensive) way to dampen vibration is fill back the solid platinum cases with powered diamonds (gem quality of course). I find this also increases thermal conductivity wonderfully well. Hmm... actually diamond is a great conductor of heat, better not mention this on Audio Asylum.

Realityists! What can you do with them.

Phil

Wow that was incoherent, even for me!

To try the part I messed up the most once more.

"After all, everyone knows that the best (most expensive) way to dampen vibration is back fill the solid platinum cases with powdered diamonds (gem quality of course). "

All a joke of course. I just love how most tweaks seem to have a consistant theoretical underpinning of "if it's ridiculously expensive or a pain in the a** to do, then it just has to sound better". Sort of like God will bend the laws of physics just for you if only you try hard enough. NOT.

Phil

 

[BrianL]

HP (now Agilent) gold plates their boards, fwiw.

HP once gold-plated all their boards, computers as well
as instrumentation. This was long before Agilent. It
was phased out due to cost and the fact that non-gold
boards had increased significantly in quality and reliability
over the years.

All the HP "gold" boards were gold over nickel over copper.
As mentioned above, gold over copper is not that great
and the nickel is needed as a barrier to the copper migration.
Though there are some audiophile connectors done with
"heavy" gold over copper.

I've never listened to gold-plated boards vs. "normal" boards,
but when I was involved with switching boards from gold
to non-gold, they both seemed to "thunk" about the same
when you tapped on them. (that's supposed to be a joke).

Still there is no board prettier than an HP gold-plated board.
(and 10 years or 100 years from now you won't have
solderability problems)

These days about all you see from anyone is selective
gold over connection areas.

 

[Steve Eddy]

All a joke of course. I just love how most tweaks seem to have a consistant theoretical underpinning of "if it's ridiculously expensive or a pain in the a** to do, then it just has to sound better". Sort of like God will bend the laws of physics just for you if only you try hard enough. NOT.

Hehehe. Exactly. I call that The Smucker's Postulate¹

<font size="1">¹ Based on a trademark advertising slogan used by the <a href="http://www.smuckers.com">J.M. Smucker Co.</a>, makers of jams and jellies: "With a name like Smucker's, it has to be good.^®" A slogan which was also parodied by Saturday Night Live (back when it was still funny) which included such gems as "With a name like xxxxxxxxxxx, it has to be good."</font>

se

 

[peranders]

Is it possible to (ideally) chemically gold plate boards after they have been soldered?

I don't know anything about your specific question but have you seen old HP-stuff from the 60's and 70's? The pcb's were always goldplated at the componentside but had no soldermask. The downside had always a soldermask and were not goldplated. Even my HP calculators had gold on the pcb's. When I opened a HP instrument, oscilloscope or whatever, I allways said: aaaaaaaaah(*) like tasting or smelling good food.

Anyone who knows why HP did that?

Petter, gold is really cool! Nothing beats that.

Let me also point out that the reason for plating is:

Lower the contact resistance (long lasting)

Protect copper traces against harsh environment

Make i look prettier

The conductivity thing (when we talk normal plating thickness) is totally inimportant (Am I right here?). Silver, copper, lead, tin, gold, iron, doesn't matter. But if we talk HF coils with silver plated copper, then I think it matter, the choice of metal.

(*) What do you say in english when you smell something good?

Edited
Sorry, BrainL, didn't see your post above, still lovely, these HP-boards.

 

[Steve Eddy]

Re: Re: Gold or silver plating soldered boards?

The conductivity thing (when we talk normal plating thickness) is totally inimportant (Am I right here?).

That would be "unimportant." But don't worry, your English is better than a lot of native-born Americans'.

(*) What do you say in english when you smell something good?

"Mmmmmm" or "ahhhhhhh" typically. Or in some of the rougher neighborhoods, "It's about time somone took that dead body out of here."

se

 

[Petter]

The original idea was to ...

The original idea was to get a non-corrosive coating on the entire board including component leads -- and to have similar conductivity all over. I realize this is probably not worthwhile.

I like the idea of gold plated boards except for one thing. Nickel is ferromagnetic (magnetism of the worst sort in Audio (barring transformers) ...

Perhaps I will consider silver plating my teflon boards (pre-solder stage) and SMPS transformer windings

Interestingly I just learned from a friend that solder plated boards sound worse than non-plated boards ...

Petter

 

[Steve Eddy]

Re: The original idea was to ...

The original idea was to get a non-corrosive coating on the entire board including component leads -- and to have similar conductivity all over. I realize this is probably not worthwhile.

Including component leads? Well, there are conformal coating sprays for that sort of thing. What components are you using whose leads are not already non-corrosive coated? Most component leads are tin plated already.

I like the idea of gold plated boards except for one thing. Nickel is ferromagnetic (magnetism of the worst sort in Audio (barring transformers) ...

Why not just have the boards made for you, SMBOC (Solder Mask Over Bare Copper)? Today's masks are made from exceedingly thin films so dielectric issues aren't anything to worry about.

Perhaps I will consider silver plating my teflon boards (pre-solder stage) and SMPS transformer windings

But of course, silver oxidizes. And worse, reacts with sulfur compounds in the air to form silver sulfide.

Interestingly I just learned from a friend that solder plated boards sound worse than non-plated boards ...

All I can say is, "SMOBC - Works for me!"

se

 

[dice45]

Haldor,
on the floor laughing !

All,
i was simply suggesting not to plate at all.
Urethan 71 (mabe by Kontakt Chemie) spray urethane lacquer does fine for me.

I have tried it with cables: pure copper sounds good, pure silver sounds better say some folks, i say it's a matter of taste.
I do not follow Smucker's postulate bbut who wants can take pure silver or pure gold, just do not plate it.
Plating on what ever material spoils sonics. I don't like it.

Petter,
your friend reports the similar.
So the probability cloud is becoming more dense concerning plating being disadvantageous .

BTW, one of the most sought-after cartridges is a working sample of the vdHul Grasshopper IV Gold. It uses gold wires for the coils and i have learned from a guy who owned them both that he clearly prefers the Grasshopper Gold over the Grasshopper Silver. An indicator for me that highest conductivity of a conductor is not necessarily achiving best sonics.

Petter,
you have Teflon PCB boards! this definitely is advantagous for sonics, no only the dieleectric is better, also parasitic µphony is damped. Gorgeous!
Where do you buy them?

One hint: use **many** supporting posts, keep the PCB from excessive bending otherwise the routes might craze and crack. But you probably know that.