Homebrew PCBs

Robert wrote:

--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan <robert.hedan@...>
wrote:
>
> > -----Message d'origine-----
> > De : Homebrew_PCBs@yahoogroups.com 
> > [mailto:Homebrew_PCBs@yahoogroups.com] De la part de dagmargoodboat
> > Envoyé : juin 28 2006 22:59
> > À : Homebrew_PCBs@yahoogroups.com
> > Objet : RE : [Homebrew_PCBs] Re: Toner melting points, pt. 2
> > 
> > 
> ...
> > My board prep *was* slightly lax--stainless steel
> > potscrubber, with soap, then Comet cleanser, towel
> > dry--but it's robust enough to cut through the dull
> > oxide and leave a mirror finish on the Cu.  Same
> > procedure as used on the "perfect" trial board.
> > 
> > I'll post any fixes I devise.
> > 
> >   Thanks again Robert,
> >   James
> 
> 
> James,
> 
> I recommend at least either acetone or 90% + isopopyl alcohol to
remove any
> leftovers, and then wipe that dry.  I think Comet leaves a residue
behind,
> you might not have wiped it dry evenly between the 2 tests.  The
last time I
> used Comet on the sink, it leaves a very shiny and 'slippery'
finish, it's
> like a wax effect.
> 
> Robert
> :)


And Stefan suggested:

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan"
<stefan_trethan@...> wrote:
>
> I have not followed the thread, so maybe this is not a suitable answer.
> 
> Some printers use fuser oil on the fuser roller. maybe your toner
surface  
> is contaminated with that?
> 
> ST

  Thanks to both--what a nice group this is!  Here's my update:

  I've improved pcb copper preparation by rubbing to ensure complete
removal of any cleanser films, and adding a wipe with isopropol alcohol.

  My earlier work measuring toner melting points suggests laminator
heat is not a problem.  To double-check, and to eliminate questions of
adequate pressure, I transferred the toner first with the laminator,
then pressed hard with the edge of a household iron, working the surfaces.

  After soaking and removing the paper, I "flash fused" the remaining
toner by heating the boards to ~180 C (360 F) for five or ten minutes.

 Despite the extra steps, results are not much different.  I
transferred and etched 7 more boards.  Toner transfer isn't super --
the 0.006" ((0.15 mm) traces show one or two gaps per board, which I
touch up with a Sharpie marker, then bake to cure before etching.

  John Popelish's float etching method (floating the boards on FeCl
ethant) worked a treat, saving over-etching in a number of places.

  If these were 0.010" lines I think the boards would be superb as
they are; the defects that ruin a 0.006" trace would be much less
important.  Fortunately these are tiny boards with only a few traces,
so I can touch them up and still get good prototypes without too much
trouble.  It is nerve-wracking though, to try and paint 0.008" /
0.006" / 0.008" space / trace / space rules with a Sharpie!

  Robert--since my tests transferring the toner patterns on Staples'
Picture Paper leave gaps even on decorative foil when I try, I think
this excludes copper surface prep. as a variable (though I did upgrade
my procedure with some of your suggestions, as noted above).

  Stefan--yes, I still suspect (but cannot yet prove) something's
wrong with the toner print, either dust, fingerprints, oil from the
fuser rollers, or perhaps just from not using them immediately
(oxidation?).

  I've a new test for toner adhesion, the "Rip Test."  After
transferring the toner, I just rip the paper off, no soaking.  I
discovered that, surprisingly, this left as much toner as gently
soaking and rubbing.  I conclude that, once transferred, the toner
grabs pretty well, and is tougher than I thought.

  So, that's the update.  Despite lack of a solution to my immediate
situation, I'm encouraged that the toner's adhesion strength and ease
of melting suggest that truly excellent 6/6/6 boards are possible.

  Thanks again for all the suggestions guys.

  Cheers,
  James