Nested glass exposure tool registration device

Details Nested glass exposure tool registration device Nested glass exposure tool registration device

2000-03-10

2001-04-10

Adams, Russell (Department: 2851)

Photocopying

Projection printing and copying cameras

Detailed holder for original

C355S026000, C355S053000, C355S072000, C356S401000, C356S399000

Reexamination Certificate

active

06215548

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to photographic image masters and more particularly to apparatus for maintaining close-tolerance registration of such image masters on opposite sides of an image-receiving object during illumination and exposure of the image-receiving object to the image masters.
BACKGROUND OF THE INVENTION
Photographic techniques are commonly used in the fabrication of printed circuits and other chemically-milled components to form images on the surfaces of rigid or flexible substrates such as circuit boards. Certain known circuit board configurations require formation of images on opposite sides of a common circuit board in close registration at critical locations such as at through holes, apertures, peripheral borders, and the like. For such circuit board configurations, it is common to expose both light-sensitive surfaces of the circuit board through respective image masters in order to improve productivity through subsequent photographic processes that develop and etch the final circuit patterns in close registration on the opposite sides of the circuit board.
Conventional fixtures for supporting image masters commonly rely upon composite materials that are less dimensionally stable than glass-based image masters, and thus such conventional fixtures suffer loss of registration accuracy attributable to wear, thermal variations, and the like.
SUMMARY OF THE INVENTION
In accordance with one embodiment of the present invention, supporting fixtures for pairs of glass image masters rely upon the dimensional and thermal stability of glass to preserve registration accuracy over time and use. The fixtures include gas springs to counterbalance the weight of the upper glass image master and to resiliently bias the upper glass image master into proper registration with the lower glass image master. Spring actuators also bias registration of the pair of glass image masters toward one side. Reference edges of the glass image masters thus remain in dimensionally accurate registration through repeated production operations that require relative separations and closures of the pair of glass image masters as light-sensitive circuit boards are inserted, exposed to light through the image masters, and removed from the assembly for further photographic processing of the exposed images.


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