Andy

As an FYI...

Kepro, a US company that is in the small batch - at home pc board
business,  used to sell (and may still) an immersion tin plate solution.
While the plating soldered well and looked shiny initially it did
deteriorate over time. After about a year it would oxidize to a  very
dull gray color and soldering became difficult requiring seemingly too
much heat and flux during rework. It might have been possible to prevent
the oxidation by spraying the board with a conformal coating once it was
de fluxed - but I never tried that.

What I've been doing lately is to mount the board to a nearly vertical
surface and coat the board with solder using a 40-watt iron top to
bottom. While I can't get the solder to flow quite as smoothly as the
professional circuit board houses,  it does look pretty smooth and
bright once it is defluxed. It seems to hold up better than tin
plate...a light spray of conformal coating would probably still be a
good idea.

my 2 cents...for what it's worth.

Jay, W1VD

To: <[email protected]>
Sent: Friday, July 09, 2004 3:41 AM
Subject: LF: RE: Re: Tin Plating compound (off topic LF, almost on topic
microwaves)

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
[email protected]

----- Original Message -----
From: "Andy Talbot" <[email protected]>
To: <[email protected]>; <[email protected]>
Sent: 08 July 2004 18:01
Subject: LF: Tin Plating compound (off topic LF, almost on topic

microwaves)