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Cell Expose for Improved Registration in the Manufacture of Flexible Circuits

IP.com Disclosure Number: IPCOM000131133D
Publication Date: 2005-Nov-07
Document File: 4 page(s) / 98K

Publishing Venue

The IP.com Prior Art Database

Abstract

In the roll-to-roll manufacture of flexible circuitry, it is often necessary to align, or register, one circuit pattern to another circuit pattern or to interconnect vias during a photolithographic step. This photolithographic step is performed on a Re-Register Exposer and the alignment is typically done with a single set of fiducials on a phototool and a matching set of fiducials on the incoming pattern. An entire panel is exposed to UV light at the same time. A typical panel is approximately 12"x12" and pattern to pattern alignment is on the order of +/-50 microns. Very often, registration as tight as +/- 10 microns is required for product designs. This paper describes a novel "Cell Expose" feature of the Re-Register Exposer, which was designed to obtain this registration precision. Additional fiducials are utilized so that small cells, or areas, of a web are exposed to the UV light independently from one another across the web in the cross-web direction (up to 3 cells wide). This provides tighter accuracy and precision than registering and exposing an entire panel. As mentioned above, registration error of at least +/-50 microns must be allowed when exposing a full panel (12"x12"). This amount of error is a compilation of i.) dimensional errors of the phototools (first pass and second pass), ii.) web deformation, and iii.) registration error of the Exposer. Using the Cell Expose feature reduces the effect of the first two sources of error by aligning to, and exposing, smaller areas of web at a time. Figure A shows the expose area and the alignment fiducials used for the exposure of a full 12"x12" panel. Figure B shows the same using Cell Expose in a 2-Cell configuration. Shutters are used to protect the neighboring cross-web and down-web areas, so that only the one precisely-aligned Cell is exposed. The phototool does not step across the web. The Cell Expose option on the Re-Register Exposers improves feature registration by reducing the errors due to web distortion and phototool dimensional errors. No additional process steps are required to obtain the tighter registration, though more space on the web is needed for the additional fiducials and a longer cycle time results from exposing multiple cross-web Cells. The Cells may contain any number of parts, depending on the part design and registration requirements. Figure C below shows registration data for a full-panel expose (a.) and a Cell-Exposed panel (b.). The four different colors represent the mis-registration measured in each of the four corners (if perfect alignment were obtained, all points would be stacked on the origin (0, 0)). The Cell-Expose data shown below was obtained from a design with alignment fiducials approximately 4.5" apart. Tighter registration is possible by using fiducials that are closer together, but their proximity is dependent on the design and part size.

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Cell Expose for Improved Registration

in the Manufacture of Flexible Circuits

In the roll-to-roll manufacture of flexible circuitry, it is often necessary to align, or register, one circuit pattern to another circuit pattern or to interconnect vias during a photolithographic step. This photolithographic step is performed on a Re-Register Exposer and the alignment is typically done with a single set of fiducials on a phototool and a matching set of fiducials on the incoming pattern. An entire panel is exposed to UV light at the same time. A typical panel is approximately 12”x12” and pattern to pattern alignment is on the order of +/-50 microns. Very often, registration as tight as +/- 10 microns is required for product designs.

This paper describes a novel “Cell Expose” feature of the Re-Register Exposer, which was designed to obtain this registration precision. Additional fiducials are utilized so that small cells, or areas, of a web are exposed to the UV light independently from one another across the web in the cross-web direction (up to 3 cells wide). This provides tighter accuracy and precision than registering and exposing an entire panel. As mentioned above, registration error of at least +/-50 microns must be allowed when exposing a full panel (12”x12”). This amount of error is a compilation of i.) dimensional errors of the phototools (first pass and second pass), ii.) web deformation, and iii.) registration error of the Exposer. Using the Cell Expose feature reduces the effect of the first two sources...