Methods of making printed circuit boards utilizing an image transparency mode with Herschel-effect film
OwnerBarry David Browninventor
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Abstract
The photographic method of producing a printed circuit involves preparing a film negative from a graphic replica of the printed circuit and, through the film negative, exposing a photosensitive coating on a copper laminate board which is then developed and etched. This method is improved using Herschel-effect film in two successive steps, first producing a film image of the graphic printed-circuit replica and then producing the required film negative from the first film image. One of the film images is a film positive and the other is a film negative.
Claims8
In the method of producing a printed circuit board by preparing a film negative of the desired printed circuit, assembling the film negative to a photosensitive coating on a copper-clad laminate, exposing the coating to light through the negative, developing the coating to produce bare and resistcoated areas, and etching away the bare areas of the copper-clad laminate, the improvement in the preparation of the film negative which comprises the steps of applying a first Herschel-Effect silver halide emulsion film to a graphic image of the desired printed circuit, exposing and developing the first film so as to yield a film copy of the graphic image, applying a second Herschel-Effect silver halide emulsion film to said film copy of the graphic image, and exposing and developing the second film, one of said films being initially fogged when it is exposed so as to yield a positive replica of the image to which it is exposed, the other of the films being initially unfogged when it is exposed and developed so as to yield a negative replica of the image to which it is exposed.
Dependencies are inferred from the claim text.