In message 352, list member Tom stated:
"BTW, the screen printing emulsions are negative acting so you will
need positive films emulsion side up."
So I guess you are saying that my laser printed PCB patterns (on
plastic sheets) are positive as is, and I have my terminolgy
backwards. So I can use these with "negative acting screen printing
emulsions" to get the silk screens I need to put resist ink on the
copper which is not to be etched?
Grant
"BTW, the screen printing emulsions are negative acting so you will
need positive films emulsion side up."
So I guess you are saying that my laser printed PCB patterns (on
plastic sheets) are positive as is, and I have my terminolgy
backwards. So I can use these with "negative acting screen printing
emulsions" to get the silk screens I need to put resist ink on the
copper which is not to be etched?
Grant
--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
> grantfair2001 wrote:
> >
> > By positive, I mean that the copper tracks will appear white when
> > printed on paper, and etched portions will be black. My PCB software
> > does the usual "negative" print - copper tracks are black, etched
> > areas white, but not the positive print.
> >
>
> As someone already pointed out, you have your terminology
reversed by
> trying to label it what you want it to do. On screen is a positive,
> what you're describing is a negative, and then the exposure process
> negates it again to make a positive PCB with correct tracks. Note that
> your reversed terminology will make you want a 'positive' and when you
> print a 'positive' it'll be backwards to what you want. What you
really
> need to find is the program's way to print a negative image.
>
> Keep in mind that you can always reverse the sense of positive and
> negative in anything, electronic or mechanical or photo or anything
> else, and it'll still work logically as long as you keep the senses
> consistent. That means you are REQUIRED to correctly determine and
> match the normal conventions, or you will be thinking the wrong thing
> and be getting results that you think don't work correctly when really
> you just chose the wrong result by being backward to normal polarity.
> It's not that the program's 'positive' output or 'negative' output
> aren't correct. You just chose their 'positive' when you really wanted
> their 'negative' and have your choices reversed to the conventional
> direction..
>
> Alan