1. Field of the Invention
This invention relates to an apparatus for positioning a pair of elements into aligned intimate contact. Particularly, this invention relates to apparatus for a precise photocell-controlled positioning a resist-film covered, copper clad, flexible web adjacent to a pattern master for exposure to ultraviolet rays.
2. Description of the Prior Art
One method of manufacturing flexible printed circuits includes the screen printing, in ink, of circuit patterns directly onto a surface of copper cladding of successive sections of a flexible web with land areas of the inked patterns desirably located about positions whereat holes will be subsequently punched in the cladding and through the web. Thereafter, those portions of the copper cladding which are not covered by the ink are removed in an etching process. The ink is then removed from the remaining copper cladding and additional copper is deposited onto the now-exposed cladding, onto the walls of the now punched holes and, if desired, onto similarly formed circuit patterns of copper cladding on the opposite side of the flexible web.
To facilitate the screen printing process, a series of through slots are placed in spaced relation in each of successive sections of the flexible web along one margin thereof in a precise relationship to the positions whereat holes will be punched through the web. In addition, window openings are formed in the screen in precise relationship to circuit patterns in the screen and are designed to coincide with the through slots of the flexible web when the screen and successive web sections are aligned.
A light source is positioned adjacent to the window openings in the screen and, but for the presence of the flexible web, would normally direct light rays onto light sensitive devices, such as photo-diodes. The light sensitive devices are connected to a control system to assist in the control of a pair of web feed drums, at entrance and exit locations to the screen, which cooperate to accurately position the flexible web under the screen and, further, to control a screen positioning mechanism to accurately position the screen pattern relative to the flexible web.
In operation, successive sections of the flexible web are indexed adjacent to the screen and each section is accurately aligned with the screen for the screen printing operation. As each section of the flexible web is indexed into a position adjacent to the screen, a first of the slots in the web passes a window opening in the screen whereby one of the light sensitive devices is activated to facilitate the slowing of the feed of the web. Thereafter, the same slot in the flexible web is positioned for alignment with a corresponding window opening in the screen pattern. When the slot and window opening are generally aligned, another of the light sensitive devices responds and develops a voltage which controls the synchronous operation of the feed drums to accurately align the slot and window opening so that the section of the flexible web is aligned accurately in the longitudinal direction with the screen pattern.
As the first slot is positioned for alignment with the corresponding window opening, two other slots in the flexible web are also positioned to be aligned with corresponding window openings in the screen. When these slots and window openings are generally aligned, corresponding light sensitive devices respond to develop voltages which provide for the movement of a support for the screen to precisely align the two other slots and corresponding window openings and thereby provide for the precise lateral alignment of the screen pattern with the section of the flexible web.
After the two-direction alignment is accomplished, a table which is positioned adjacent to the web on the side opposite from the screen, vacuum grips the section of the flexible web and moves the web section to a spaced position beneath the screen. Thereafter, ink is deposited onto the screen and subsequently wiped through the pattern and onto the copper cladding of the web.
A reverse procedure is initiated to release the gripped web section and the next successive section of the web is then moved to align the next successive section with the screen pattern for the next ink printing operation.
Another technique for manufacturing flexible printed circuits includes the placement of a photoresist material on the copper cladding, the placing of a circuit pattern master adjacent to the photoresist material and the subsequent exposure of the uncovered photoresist material to ultraviolet rays whereby the exposed material is developed. Thereafter, the undeveloped photoresist material is removed to expose the underlying copper cladding.
In a first example, if the underlying exposed copper cladding is in the pattern of the ultimately formed circuit, additional copper is plated onto the exposed cladding and a protective solder coating is then applied to the plated copper. Thereafter, the exposed photoresist material is removed and the underlying copper cladding is removed whereby the desired printed circuit remains.
In a second example, if the underlying exposed copper cladding is in areas other than that ultimately occupied by the printed circuit, the exposed cladding is then removed by an etching process leaving only the copper cladding covered by the unexposed photoresist material. Subsequently, the unexposed photoresist material is removed to reveal the copper cladding in the pattern of the circuit pattern master. Subsequent copper plating and solder coating operations provide for a copper build-up and protective coating in the configuration of the circuit pattern.