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Tin plating copper clad pcb

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Sulaiman

Sun Mar 30 2014, 10:15AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

I have plain copper clad pcb material, some in sheet form,
some cut to 160x100mm 'Eurocard' size, and some cut as a front panel.
I then cut the copper away to make 'tracks', or Manhattan style etc.

I am considering tin plating the mostly double sided fiberglass boards
as they tarnish so horribly.
For a cosmetic tin plated finish I'm considering a pure tin 5oz. 'ingot' (GBP7.50, eBay)
and electrolytic plating - guessing that I'll need a lot of tin.
I've no experience of tin plating .. suggestions please. (electrolyte etc.)
(cheap, disposable, not to unfriendly to the environment or me etc.)

P.S. just read that a final plating of chromium is required for the 'shiny' finish,
I don't want to use chromium so any reasonable finish that is easy to do is needed.
(I've looked at 'tinning salts' which seem ok but I want less cost/area.)

P.P.S
12Apr14 bought pure tin and hydrochloric (36%) acid, results to follow.
14Apr14 bought 500ml each of Sulphuric (96%) and Nitric (69%) acids
so I can experiment with tin(II) chloride or sulphate electrolyte.
(quite surprised that such concentrated acids are available via eBay UK)
I'll probably have a play with tin crystal growing too

Sulaiman

Sun May 11 2014, 09:01PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Finally got around to making a YouTube account and a video of tin crystal growing
here is the video

The solution is tin in hydrochloric acid (a bit too much acid, hence the 'steam' in the video)
it looked prettier than in the video
but I'm quite pleased for a first YouTube attempt.
This was my second attempt, I didn't video the first attempt.
My son made the video using a Cannon SLR
The video is in real time.

Thomas W

Sun May 11 2014, 09:24PM

Registered Member #3324 Joined: Sun Oct 17 2010, 06:57PM
Location:
Posts: 1276

Wow, that looks really awesome i must say. thinking of getting some of these things and giving it a go myself.

Sulaiman

Sun May 11 2014, 11:03PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

What I liked was that after the video I put the crystals and liquid back in a flask, heated it
and the tin crystals dissolved back into the liquid, ready to play again.

The first time I tried I varied the current,
low current gives lots of tiny crystals, like frost
higher current gives even thinner crystals.

if the tin chloride + acid is very diute then wide flat blade-like crystals formed.
I'll be playing some more.

a 9V alkaline battery is about the best voltage, quite a current drain though,
that's why I used a bench power supply for the video.
so I may try sealing the electrodes/liquid as it is re-usable just by warming.

Once I've experimented enough I'll do what I originally intended .. tin plating copper-clad board.

Ash Small

Sun May 11 2014, 11:15PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I'd use the 'old' flux technique, and use the purest tin I can get.

Electro-chemistry is a 'dark art' if you don't know what you're doing.

try the 'traditional' approach first

Sulaiman

Mon May 12 2014, 12:47PM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Well, I don't know much yet, that's part of why I'm playing / experimenting,
and 'dark art' is what this forum is all about !

From playing with my crystal growing setup I can see why much lower current densities give a better finish,
and by reversing the polarity (just call me 'Scotty') after the crystals have formed
I saw how they break up, especially near the cathode, and drop off
which is probably related to the practice of repetitively and briefly passing a large reverse current during electroplating,
even if the finished product is not a super smooth bright finish when I do it,
it should be enough to protect the copper from corrosion, which is my main aim,
and it's fun ( must get out more ! )

I certainly would NOT recommend diy tin electroplating, the pre-packed electroless system is easier
and for typical PCBs it doesn't need all of the copper to be electrically connected

Ash Small

Mon May 12 2014, 01:27PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I still think just melting the tin and fluxing the board and dipping it is the easiest way to get a good finish, but I'm also interested in your results.

It's sometimes difficult to get a 'lasting' finish with electroplating.

klugesmith

Tue May 13 2014, 01:17AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Have you looked into commercially packaged fluids for this purpose?
e.g. Liquid Tin by MG Chemicals.

I can attest that pure tin, plated onto solid copper, has the risk of spontaneously growing tin whiskers.

Sulaiman

Tue May 13 2014, 06:10AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Yes, the first thing I looked at was 'Liquid Tin' and similar proprietary products.
I considered it expensive, so decided to have a go at electrolytic plating.
I have looked at the MSDS for 'Liquid Tin' to see what additives are used
Fluoroboric Acid 9-11%
Stannous Fluoroborate 9-11%
Thiourea
and probably some 'secret' ingredients ...

I've also researched 'tin whiskers' and watched video's of their growth (amazing)
and researched tin plating in general.

Despite all of the above I'm going for tin electroplating,
partly since I only want to coat continuous sheets, cheaply
and partly because chemistry was the hobby of my youth
and I just felt like re-visiting chemistry.
I have already spent more than I would have if I just used 'Liquid Tin'

Digital scales & calibration weights, acids, thermometers,burner, flasks, liquid measures ....etc.
and a Quickfit Leibig condenser setup (I couldn't afford one when I was younger)
so it's really a 'justification' to myself to spend some cash on a 'Chemistry Set'
(I did 'A' Level chemistry, I used to run the Chemistry Club at school and it was my main hobby).
I've been watching YouTube video's by 'Periodic Videos' .. so Chem knowledge getting refreshed.
As a youth Pyrotechnics was my main area of chemistry
but in the current environment (I'm a bearded Muslim) I will be prudent and avoid that area.
Although I have good neighbours
(my Ham Radio antennas and Tesla Coil experiments have caused interest, not complaints)
pyrotechnics would probably be a bit too much to ask.

So, thanks for the advice .. but I'm going a different direction.

P.S. can anyone suggest a chemistry forum that doesn't emphasize pyrotechnics and illegal drug synthesis ?

P.P.S. if anyone can provide a list of chemicals that are likely to cause black helicopters or swarms of police to appear, please suggest them ... I don't want to vanish in the night !

Large quantities of Ammonium Nitrate, Hydrogen Peroxide, Acetone are the most obvious,
what else should I avoid ?

Ash Small

Tue May 13 2014, 11:18AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I've had a look at a couple of webpages on the subject, and it would appear (if I've understood correctly) that in order to obtain a bright finish, the workpiece is heated to the melting point of tin (232C) after electroplating.

Does this concur with your research, Sulaiman?

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