That eraser shield is a good idea. I could use that with touch ups
prior to etching and so forth. Now for the hard part - finding
one :-) as I am sure I have thrown out a dozen of them in the past
couple decades.
Chris
--- In Homebrew_PCBs@yahoogroups.com, "dl5012" <dl5012@y...> wrote:
>
> --- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
> <lcdpublishing@y...> wrote:
> >
> > This weekend I etched some boards with .010" wide traces
> with .010"
> > wide spacing. After etching I found a couple of traces "broken"
so
> I
> > had to repair them and with these old eyes, it wasn't easy but I
> did
> > get it.
>
> For tiny breaks, I'm using a conductive pen. It's silver
particles
> in a carrier. Supposedly you can simply draw traces, but I've
found
> that it dispenses too much "ink". What I do is put a blob on
> something handy (scrap PCB, etc) and use a toothpick or needle to
> transfer small amounts to the broken trace. I've never tried to
> solder to a patch (it says it's solderable). Resistance is 0.1
ohm-
> cm when cured at 25C and 0.02 when cured at 150C.
>
> You can get info from Jameco Electronics -
> http://www.jameco.com/webapp/wcs/stores/servlet/ProductDisplay?
> langId=-1&storeId=10001&catalogId=10001&productId=263716
>
> > As to the reason for the breaks in the traces - just being in
too
> > much of a hurry. After doing the toner transfer, I inspected
the
> > boards very good and did notice the missing toner. Knowing that
> the
> > Sharpie pen is too blunt to patch the spot, I just went for the
> > etching. I really should have cleaned the boards and tried the
> > transfer process again - it would have been much faster and
easier.
>
> For cases like this, I use an eraser shield (anyone old enough to
> have drafted schematics and mechanical drawings by hand will know
> what this is). If the eraser shield openings are too large, I use
a
> piece of overhead transparency to reduce the opening.
>
> I've found that the "original" fine point Sharpies work better as
an
> etch resist. The ink in the ultrafine is pretty useless. I
bought
> an industrial Sharpie with a wide tip to see if that ink is better.
>
> For cases where too much ink get's applied, I use an eraser shield
> and eraser to remove the excess. Anyone old enough to have
drafted
> schematics or mechanical drawings by hand will know what this is.
> It took trips to a dozen office supply and craft places to find
> them; and the new ones are crap. For cases where the eraser
shield
> openings are too large, I use a piece of overhead transparency or
> similar material to reduce the opening. In the end, I have nice
> straight edges...
>
> I've got my toner transfer process down pretty well and don't
> usually have problems with traces being etched open. I usually
err
> on the conservative side and melt the toner until it starts
> spreading. This can create shorts which I clean up with an Xacto
> knife before etching. I always go over my copper fills to
minimize
> pitting during etch.
>
> Regards,
> Dennis
>