Method for manufacturing artwork for printed circuit boards

Claim 1

The method for preparing photographic artwork of claim 1, whereby the secondary pad mask is obtained by a process comprising the steps of: contact collimation of an unexposed photographic plate with a master positive mask comprising at least part of the lead connection layout along a first direction, for obtaining, after exposure to substantially parallel light rays, a negative latent image of said part of the lead connection layout, contact collimation of said plate with a master positive mask comprising at least part of the connection lead layout along a second direction, to obtain, after exposure to substantially parallel light rays, a negative latent image of the crossover regions of said connection leads, development of said plate to obtain a negative mask comprising said crossover regions of said connection leads, distance collimation of an unexposed photographic plate with said mask comprising said crossover regions, and exposure of said plate through said mask to a suitable source of diffused substantially uniform at all points, sufficiently distant from said mask to obtain a latent positive image of rounded-off and enlarged regions corresponding in position to said crossover regions, such rounded off and enlarged regions being suitable to be used as a layout of all possible pads, and said process being followed by the development of said plate to obtain a positive secondary mask of the pad layout.

Claim 4

A method for preparing photographic artwork in the form of a mask, to be used for photoetching a printed circuit, whereby a negative mask comprising all connection leads specific to a single printed circuit is obtained by the use of a secondary complete positive mask comprising all possible connection leads common to a plurality of printed circuits, followed by deleting all the connection lead lines not specific to said printed circuit from a latent image obtained from said complete secondard mask, said deleting being obtained by the combined use of a plurality of partial masks comprising the layout of only the connection leads specific to the desired circuit and of master masks comprising the layout of all possible leads for the whole surface of the printed circuit, a separate mask respectively for each direction of the desired printed circuit leads.

Claim 7

A method for preparing artwork for photoetching printed circuit boards of the type having pads with connection leads therebetween comprising lines of uniform width arranged along at least two directions, the method comprising: forming a plurality of master masks defining the layout of all possible leads for the entire surface of the printed circuit a separate mask respectively for each of said directions, forming a plurality of secondary masks defining the layout of all possible pads on the surface of the desired printed circuit by exposing a photosensitive medium to a radiation source through said master connection lead masks in an optical photographic process, said master masks and said secondary masks being common for a plurality of printed circuits, and forming a plurality of distinct partial masks defining the layout of the lines of the specific connection leads of each desired printed circuit by exposing a photosensitive medium to a radiation source through said master connection lead masks in an optical photographic process, and employing said partial masks and said master masks in combination to delete all the connection lead lines from another secondary mask containing all possible connection leads common to said plurality of printed circuits by subjecting said other secondary mask to a series of successive exposures by a radiation source through said combination of masks.