PLANAR COAXIAL INTERCONNECTION TECHNIQUES

The object of this work is the development of planar coaxial interconnection techniques that integrate the batch fabrication advantages of printed circuits with the electrical characteristics of point-to-point coaxial wiring by forming coaxial conductors within laminated aluminum plates. Analyses and investigations have been completed on three types of aluminum, eight types of surface preparation, and two types of photo resist; in addition, several combinations of etch solutions and etch times have been studied. Work to date indicates that the aluminum surface can be prepared by mechanical sanding, followed by trichloroethylene vapor cleaning; with this approach, Kodak KMER or KPR is used as the photo resist, 22 degree Baume ferric chloride is used as the etchant, and alloy 1100 aluminum is used as the substrate. An alignment tool, for punching holes in photographic film masks and the aluminum plates to an accuracy of 0.0001 inch, has been fabricated and is being investigated. Results obtained indicate that channels can be etched into aluminum plates with depths controlled to an accuracy of 0.5 mil, that cavity widths can be etched to within plus or minus 1.0 mil, and that the etched channel linearity can be held to within plus or minus 0.3 mil. Preliminary analysis indicates that coaxial lines fabricated into the planar coaxial planes on 0.025-inch centers will provide characteristic impedances and tolerances consistent with the objectives of the program. (Author)