Homebrew PCBs

My tin setup is Sulfuric based, Tin stuff and Brightener
The Tin is pattern plated at 100 milliamps per sq in (.0001 per 10 mins) I
shoot for 0003~0004 "
My tin Tank is 3 Gallons

The Flash copper is alkaline, mostly copper sulfate with hyposodium base and
organics.
The copper is panel plated, with 1 amp per 10 Sq In (.00025 per 15 mins)  ,
I shoot for  a 0.0005" coverage
My copper tank is 3 Gallons

The electroless Nickel is a bit complicated on keeping exact track of how
much you have used. I know that it has Nickel in it,
But other than that Its Part A, Part B, Part C and Water.  It must be HOT
195 Deg F.
Plates very evenly  0.00025"  per 15 min. I shoot for .0003".
The Nickel tank is 1/2 a gallon.
My plating-dev-strip-etch, "system" is 32" wide X 8 feet long

>I have never heard of problems of
> electroplated tin creating whiskers. Do you have any knowledge of
> tin whiskers being a concern in PCB production.
> here is an interesting articles on tin whiskers.
>
http://nepp.nasa.gov/whisker/reference/tech_papers/brusse2002-slides-tin-whiskers-attributes-mitigation-CARTS-europe.pdf<

I'm a little confuse by your statement. as the link you posted is absolutely
a great resource on tin "whiskers" and even they end by recommending
avoiding PURE tin. ... and that is what I've done with a 10% Lead content.

I'm not going to argue the merits of intermetalic alloy formation, lots of
factual info already out there. 1 month is not very long, ,,, 3 Year is a
good testing point.

JT


----- Original Message ----- 
From: "Adam Seychell" <adam_seychell@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Wednesday, March 31, 2004 11:39 PM
Subject: Re: [Homebrew_PCBs] plated tin as the etch resist


>
>
> Jeremy Taylor wrote:
>
> > no problem
> > I drill first with the cnc machine
> > then use the ink activation, then bake the board in a convention toaster
> > oven,
> > Then I plate the whole board in an alkaline "flash" copper. then dry in
the
> > toaster oven, than a dip in hot tri sodium phosphate, a good scrub and
> > rinse, then I laminate on Negative resist, and expose a positive image
and
> > develop, This results in everything but the traces and pads etc covered
in
> > resist. I then plate the tin, This plates everything exposed (including
the
> > holes), in very fine and solid detail, You can clearly see when
everything
> > is fully plated, over plating is not a problem >you do need oversized
holes
> > tho<. The next step is the resist stripper, then into the etch,
Sulfuric
> > Peroxy (which doesn't etch tin) and everything not plated with tin gets
> > removed. ... I'm actually using a 10% Lead content in the tin to keep
the
> > tin from sprouting roots, and to "set" it, I have to reflow it, which
means
> > back in the oven.   For boards, I plan on selling as kits (i.e.... not
> > immediately assembling), I also use a nickel undercoat (between the
copper
> > and the tin, to prevent the anti-solderable intermetallic alloy forming)
> > There are other various pre dips and post dips and rinses between each
step.
> > I've got it laid out in a nearly effluent free process. I can reclaim
copper
> > sulfate from the etch to replenish the copper plating tank. The only
things
> > I dispose of are the resist stripper (sodium carbonate) and the
developer
> > (sodium bicarbonate) which are both very safe chemicals.
www.thinktink.com
> > and www.caswellplating.com two US  links to more info. The only "odd
thing I
> > had to source was the low lead tin anodes. I didn't feel 60/40 solder
plate
> > was very Green considering how evil Lead is.   Pure tin grows metallic
> > fingers that will short circuit traces, and the intermetallic alloy
> > formation begins immediately, completely consuming the tin within 3
years
> > (in perfect storage)
> >
> > JT
> >
> >
>
>
> Jeremy,
> What bath compositions do you use for all three plating tanks ?
> I have done some pure tin electroplating on PTH boards and had no
> soldering problems with inter metallic alloys forming at least in
> the first month. The tin plating thickness is round 5 to 8 um
> (measured by amp hours). I have never heard of problems of
> electroplated tin creating whiskers. Do you have any knowledge of
> tin whiskers being a concern in PCB production.
> here is an interesting articles on tin whiskers.
>
http://nepp.nasa.gov/whisker/reference/tech_papers/brusse2002-slides-tin-whiskers-attributes-mitigation-CARTS-europe.pdf
>
> http://www.p-m-services.co.uk/electroless_tin.htm
>
> I seems that if plated tin is thin then the migration of copper
> in to the tin will stop the win whiskers being formed.
>
>
> The tin bath is 200/L sulfuric + 15g/L tin as stannous sulfate +
> proprietary brightener, and the copper plating bath is 200g/L
> sulfuric + 20g/L copper as copper sulfate + proprietary brightener
> .
> Is a nickel plating bath difficult to setup and maintain ?
>
>
>
>
>
>
>
>
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