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Via Hole Inspection Apparatus

IP.com Disclosure Number: IPCOM000089073D
Original Publication Date: 1977-Sep-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Gasparri, AS: AUTHOR [+2]

Abstract

This apparatus detects missing via holes in a multilayer ceramic green sheet in the fabrication of multilayer ceramic substrates.

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Via Hole Inspection Apparatus

This apparatus detects missing via holes in a multilayer ceramic green sheet in the fabrication of multilayer ceramic substrates.

In this apparatus a punched ceramic green sheet 10 is depicted with a missing via hole in the lower right hand corner. Master mask 12 has the desired pattern of punched holes in the desired configuration which would correspond to the punched holes in sheet 10, if it were perfect. In operation a source of white light 14 is projected through the master mask 12 on screen 16. Simultaneously, a source of colored light 18 is projected through green sheet 10, which is being inspected, onto the same screen 16 in an overlay pattern.

The resultant pattern on the screen 16 will display all colored dots unless a hole is missing in the green sheet 10. This spot 20 will be white since it received light from only source 14. The remaining spots 22 will be colored since they receive colored light from a source 18. This difference in color can be easily visually inspected without causing undue eye fatigue. The arrangement for projecting the various beams onto a single screen from two different sources can be accomplished by the use of a beam splitter or optical bridge. Since the holes being inspected are relatively small, on the order of 5 mils, magnification of screen 16 will be required.

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