Homebrew PCBs

I have to differ with you, Tom. I used Tin Plate (Electrolysis) in my shop
for many years and not Gold. Gold plating was too expensive. I etched with
Ferric Chloride with no problems ever. Perhaps the trick is in how fast you
are able to etch the panel.
-Mike

----- Original Message -----
From: "twb8899" <twb8899@...>
To: <Homebrew_PCBs@yahoogroups.com>
Sent: Saturday, April 26, 2003 11:40 AM
Subject: [Homebrew_PCBs] Re: Oh no, blank fibreglass again!


> Max,
>
> We always used solder plating as a resist and it worked fine. After
> etching either reflow the solder or strip it off and apply one of the
> newer "white tin" coatings if you want tin plating. Are you using
> immersion tin or really electroplating it? Immersion tin is worthless
> as a metallic resist but some electroplated tins will work if they
> are plated heavy enough. By switching to solder plating you will
> eliminate the problem. The same plating bath can probably be used.
>
> Ferric chloride will not work unless gold is being used as the etch
> resist. Sulfuric/peroxide will work as an etchant for solder plated
> boards. After stripping the photoresist dip the panel in a 10%
> peroxide dip and then etch. This keeps the black crud from forming on
> the solder plated surface for a better reflow finish. After etching
> dip the panels in a 10% hydrochloric acid dip for about five minutes
> to brighten the solder plating for reflow. Skip the peroxide and
> hydrochloric dips if the solder is being stripped after etching. They
> are only required for solder reflow quality.
>
> Bake the boards for at least 30 minutes at 300 degrees F after
> etching and before reflowing. This is for outgassing any trapped
> moisture and will keep the plated through holes from blowing out when
> soldering.
>
> BTW, are you using the newer activated palladium cataylyst and
> skipping the electroless copper stage?  Good luck on your new system!
>
> Tom
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "Max Davies" <max.davies@b...>
> wrote:
> > Hi everyone.
> >
> > A newbie to this group, I am (perhaps over-ambitiously) attempting
> > to set up a micro through-hole plating line at home.  It's a lot
> > more involved than I ever thought it would be, but I now have most
> > of it working fine.  ...Except what should be the easy bit - the
> > final stage - the etching!
> >
> >
> > To give a brief description of what I do...
> >
> > STAGE 1:  Starting with plain, copper-clad board, I do the drilling.
> > STAGE 2:  Apply photopolymer laminate, then expose & develop. (This
> > is positive photopolymer, so the copper which will ultimately
> become
> > tracks is exposed to the air on developing the pattern)
> > STAGE 3:  Go through a 6-stage process to electroless-plate the
> > entire thing (including the holes & edges). The copper cover it
> puts
> > on is pretty thin, but uniform at 1-2 microns.
> > STAGE 4:  Electroplate the copper - this gives reasonable thickness
> > to the copper applied in stage 3 - I aim for 25 microns.
> > STAGE 5:  Electroplate with tin to 10 microns.  This
> > (theoretically!) protects the copper from etchant.
> > STAGE 6:  Remove remaining resist.  Then etch.  This should leave
> > the tin-plated areas untouched, everything else should be zapped.
> >
> >
> > But alas no!  Stage 6 fails, because both tin *and* copper are
> > etched, leaving me with a fine, blank piece of fibreglass!  It
> > matters not whether I use Ferric Chloride or Sulphuric/Peroxide
> > etchant - they both destroy what has been so lovingly created!!  So
> > I reckon there must be something awry with my tin plating.
> >
> > It's a total impasse, and nothing I do, from increasing/decreasing
> > current to re-formulating the tin plating bath according to
> > manufacturer's instructions seems to change things.
> >
> > Does anyone else use a similar process, or have any clue about what
> > might be the problem here?
> >
> > Max.
>
>
>
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