Homebrew PCBs

have you tried with sulphuric acid and H2O2 added to it?
this should not eat up your plating.
it blackens it but shouldn't eat it up.


regards
st

26.04.2003 19:46:40, "Max Davies" <max.davies@...> 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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