Message-ID: <01C46590.89F27200.actalbot@southsurf.com>
From: Andy <actalbot@southsurf.com>
To: "'rsgb_lf_group@blacksheep.org'" <rsgb_lf_group@blacksheep.org>
Date: Fri, 9 Jul 2004 08:41:28 +0100
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Subject: LF: RE: Re: Tin Plating compound (off topic LF, almost on topic microwaves)
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Ok Thanks Alan.  I'll make up a solution in that proportion and give it a try. 
 Being able to tin plate home made PCBs may solve the not too major problem of 
them becoming oxidised and not so nice to look at a few days after construction 
- though after all the joints have been made fortunately.

I have been using the bubble etch tank for some time, in the garage then 
utility room, and have seen no adverse effects from a fine FeCl3 mist - it is 
the vertical sort.  I only tend to do little boards,  (SMT components for 
everything these days, they're much easier to use).   I have noticed a certain 
difference in etch rate between top and bottom, but its so quick when hot and 
the FeCl3 is fresh that its hardly important.

The copper on normal PCB material is only 3.5microns, so that is quite an extra 
deposition.

Andy  'JNT


Hi Andy an old paper RS cat gives some information, though it would seem
there is no data sheet.
It says.....
Deposition rates of tin to tin 1.5 microns in the first half hour, and up to
3 to 4 microns in 2 hours, can be achieved at an optimum room temperature. 5
lites of solution may be made by disolving the pack (450gms) in 5 lites of
solution (note not 5 litres of water) at 50 deg C. This is enough for 2.7 sq
m of board ( I suppose they mean copper)

I think that is probably the information you want.

I think we used to call this "electroless tin-plate" I remember using
something like it for putting temporary electrodes on silicon slices. We
used a photo-electrolytic polishing system, the electrolyte was hydrofluoric
acid and glycerine....now there is something really nasty.

For etching dont use a bubble etcher, they are terribly messy and distribute
a fine, almost aerosol, spray of ferric chloride everywhere, which you dont
notice for about 2 days after which clothing and furniture starts to fall
apart. If they are the vertical type they also tend to etch unevenly...top
to bottom so you have the rotate the board halfway though...messy. I prefer
a ice cream carton (they even have a little bulge in the middle of the base
to stop the board "ringing" down) with just enough fresh etch to cover the
board warmed to about 40 deg C by immersing in a bath of hot water, and
steady gentle rocking agitation..... about 5 to 7 mins a board. Tiring but
worth the effort. Once used etch kept for the more crude projects, where you
can just leave it and not worry about undercutting fine lines.

Disposal (important these days) is easy, neutralise the used etch with
garden lime (very cheap). It is actually safe to bury then I
believe....probably good for reducing earth resistance and better for the
soil that common salt.

Cheers de Alan G3NYK
alan.melia@btinternet.com

----- Original Message -----
From: "Andy Talbot" <actalbot@southsurf.com>
To: <ukmicrowaves@yahoogroups.com>; <rsgb_lf_group@blacksheep.org>
Sent: 08 July 2004 18:01
Subject: LF: Tin Plating compound (off topic LF, almost on topic microwaves)