Homebrew PCBs

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
>