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Mirror Image Metallographic Sectioning

IP.com Disclosure Number: IPCOM000073906D
Original Publication Date: 1971-Feb-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Elmgren, JA: AUTHOR [+3]

Abstract

Inspection of sectioned through holes in a circuit board at their midpoint is facilitated by this optical method. The technique employs the pattern formed by the hole in the circuit board and its image on the ground surface of a transparent potting material. As shown at A, circuit board 1 is positioned vertically in mold 2 midway between the viewing flats 3 and 4. A transparent epoxy 5 poured into the mold provides an image mount such as shown at B. The viewing flats are parallel to each other and to the circuit board and are at 90 degrees to the base of the mount. The lower portion of the mount and circuit board are removed by grinding to expose the holes.

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Mirror Image Metallographic Sectioning

Inspection of sectioned through holes in a circuit board at their midpoint is facilitated by this optical method. The technique employs the pattern formed by the hole in the circuit board and its image on the ground surface of a transparent potting material. As shown at A, circuit board 1 is positioned vertically in mold 2 midway between the viewing flats 3 and 4. A transparent epoxy 5 poured into the mold provides an image mount such as shown at B. The viewing flats are parallel to each other and to the circuit board and are at 90 degrees to the base of the mount. The lower portion of the mount and circuit board are removed by grinding to expose the holes. The mid-point of the hole is indicated when the half circle in the board and the reflected half circle in the base of the mount are equal, when viewed at an angle through one of the flat surfaces, as shown at E. Prior to reaching the mid-point of the hole, the pattern will appear as shown at C, whereas a cut beyond the mid-point will appear as shown at D. Parallelism of the sectioning to the center line of the holes is indicated by identical patterns at the end holes. Correct vertical alignment of the sample to the sectioned face is indicated by identical patterns in both flats. Deviations from the center line of the holes are doubled in the patterns, and this increases the error sensitivity of the technique.

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