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Subject: Re: Printing pcb patterns negative or positive

From: "grantfair2001" <grant.fair@...>
Date: 2003-12-16

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