Homebrew PCBs

----- Original Message ----- 

  From: grantfair2001 
  To: Homebrew_PCBs@yahoogroups.com 
  Sent: Saturday, December 13, 2003 2:21 AM
  Subject: [Homebrew_PCBs] Printing pcb patterns negative or positive


  I use a Panasonic KX-P6500 laser printer for making prototype boards
  with Dyna Art paper, which seems to work fairly well for me. However I
  am thinking of trying to make some silk screens for small volume PCBs
  and I think I need to be able to print a "positive" of my PCB pattern
  onto transparency in order to make the silk screen.

  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.

  I use Ivex Winboard for my PCBs, and to do this would require another
  Ivex product costing $199.00.

  However there may be drivers or other ways to do this, can anyone advise?

  Grant

  1. see if you can get an updated printer driver that will allow whit on black.

  2. The old version of Pentalogix Viewmate had the capability of white on black printing as an option. The current version does not, but you might be able to write them to get an older version. It was a freeware gerber tool.

  Ron

[Non-text portions of this message have been removed]

I use a Panasonic KX-P6500 laser printer for making prototype boards
with Dyna Art paper, which seems to work fairly well for me. However I
am thinking of trying to make some silk screens for small volume PCBs
and I think I need to be able to print a "positive" of my PCB pattern
onto transparency in order to make the silk screen.

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.

I use Ivex Winboard for my PCBs, and to do this would require another
Ivex product costing $199.00.

However there may be drivers or other ways to do this, can anyone advise?

Grant

On Sat, 13 Dec 2003 07:21:41 -0000, grantfair2001 <grant.fair@...> 
wrote:

> I use a Panasonic KX-P6500 laser printer for making prototype boards
> with Dyna Art paper, which seems to work fairly well for me. However I
> am thinking of trying to make some silk screens for small volume PCBs
> and I think I need to be able to print a "positive" of my PCB pattern
> onto transparency in order to make the silk screen.
>
> 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.
>
> I use Ivex Winboard for my PCBs, and to do this would require another
> Ivex product costing $199.00.
>
> However there may be drivers or other ways to do this, can anyone advise?
>
> Grant
>
print to post script and invert the ps image, then print it.

st

> am thinking of trying to make some silk screens for small volume 
PCBs
> and I think I need to be able to print a "positive" of my PCB 
pattern
> onto transparency in order to make the silk screen.
> 
> 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.

Maybe I am wrong but I think you have positive and negative 
backwards?

I too use Ivex, to print to transparency for a positive to exposed 
my PCB's,  I personal have not done it but you can take a positive 
with photo film and make a negative which is what it sounds like you 
are wanting to make your silk screens.  I have been thinking about 
trying out screen printing to do text on the board, but have not had 
time to work with it yet.

Ben

--- In Homebrew_PCBs@yahoogroups.com, "grantfair2001" 
<grant.fair@s...> 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.

Another idea:
The ThumbsPlus image manipulation program can invert colors.  I 
assume that others, e.g. PhotoShop, can as well.  If the Ivex program 
allows to you output an image (.bmp, .jpg, etc.) you could just 
invert it with your image program and then print it.

Don

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

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


--- 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

--- In Homebrew_PCBs@yahoogroups.com, "grantfair2001" 
<grant.fair@s...> wrote:
> 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



Grant,

Most screen printing emulsions are negative acting. Expose them using 
a postive image of your circuit board where opaque black is the 
copper and clear areas are etched away. The black areas on your film 
positive will prevent the UV exposure from making the emulsion hard.  
The areas that didn't get UV light will wash out leaving an open area 
in the screen for ink to go through during printing. The film 
positive should also have it's emulsion on the side that contacts the 
screen emulsion when UV exposing. This is really important if you are 
doing fine line work.

Tom

Tom - Many thanks, again.

Grant

--- In Homebrew_PCBs@yahoogroups.com, "twb8899" <twb8899@y...> wrote:

> Grant,
> 
> Most screen printing emulsions are negative acting. Expose them using 
> a postive image of your circuit board where opaque black is the 
> copper and clear areas are etched away. The black areas on your film 
> positive will prevent the UV exposure from making the emulsion hard.  
> The areas that didn't get UV light will wash out leaving an open area 
> in the screen for ink to go through during printing. The film 
> positive should also have it's emulsion on the side that contacts the 
> screen emulsion when UV exposing. This is really important if you are 
> doing fine line work.
> 
> Tom

--- In Homebrew_PCBs@yahoogroups.com, "twb8899" <twb8899@y...> wrote:
> Grant,
> 
> Most screen printing emulsions are negative acting. Expose them using 
> a postive image of your circuit board where opaque black is the 
> copper and clear areas are etched away. The black areas on your film 
> positive will prevent the UV exposure from making the emulsion hard.  
> The areas that didn't get UV light will wash out leaving an open area 
> in the screen for ink to go through during printing. The film 
> positive should also have it's emulsion on the side that contacts the 
> screen emulsion when UV exposing. This is really important if you are 
> doing fine line work.
> 
> Tom

I'm really confused. Black areas are where copper is. But black areas
over the emulsion result in it washing away. This isn't making sense
to me.

Steve

Steve wrote:

> 
> I'm really confused. Black areas are where copper is.

   Exactly.

  But black areas
> over the emulsion result in it washing away.

   Again exactly.

  This isn't making sense
> to me.


   If black areas are where the copper is, but instead you need black 
areas over what to remove, then you need a negative of the copper areas 
image to expose the emulsion.  You use a negative image, the light goes 
through where the copper needs to stay and hardens the emulsion to 
protect that copper.  Since the emulsion makes a reverse of what you 
want, you have to reverse the picture of what you want before you expose 
the emulsion.  The emulsion makes an inverted hardening resist, so you 
also need a negative image.  "-" once and then "-" again gets you back 
to "+" of what you want..

   Just think of a black circle in the middle of a tranparency.  If the 
circle will make a hole where you wanted a copper dot, then what you 
really need to make is a black page with a clear circle.  A negative of 
the original.  That's what you use to expose.

   That is assuming a negative emulsion, there may be some positive 
acting emulsions out there.  The usual stuff is negative though.

--- In Homebrew_PCBs@yahoogroups.com, Alan King <alan@n...> wrote:
> Steve wrote:
> 
> > 
> > I'm really confused. Black areas are where copper is.
> 
>    Exactly.
> 
>   But black areas
> > over the emulsion result in it washing away.
> 
>    Again exactly.
> 
>   This isn't making sense
> > to me.
> 
> 
>    If black areas are where the copper is, but instead you need black 
> areas over what to remove, then you need a negative of the copper areas 
> image to expose the emulsion. 

Well, I was answering Tom and he said:


> Most screen printing emulsions are negative acting. Expose them using
> a postive image of your circuit board where opaque black is the
> copper and clear areas are etched away.

Which doesn't make sense. What -you- said makes sense. Use a negative
image with negative resist.

Steve

You wrote:
>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?

Where can I get "negative acting screen printing
emulsions"?

TIA,

Javier.

Search in this list on "silk screen". Tom (twb8899) has extensive
knowledge and he posted some sources in the US over a year back.

I am in Toronto, and I looked screen printing supplies up in the
Yellow Pages, made a few calls, and located a place that sold one of
the products Tom mentions in his post.

Grant

--- In Homebrew_PCBs@yahoogroups.com, JChavez@s... wrote:

> Where can I get "negative acting screen printing
> emulsions"?
> 
> TIA,
> 
> Javier.

> "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?
 

I would think that you want a negative to expose your screen which 
would be the trace pattern would be clear and all other areas dark 
just like a film negative would be.

Ben