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Optical System for Viewing Dielectric Smear in Printed Circuit Board Hole and Deleting the Smear

IP.com Disclosure Number: IPCOM000045113D
Original Publication Date: 1983-Feb-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 42K

Publishing Venue

IBM

Related People

Johnson, AH: AUTHOR [+2]

Abstract

An optical system includes a mirror that can be placed inside a hole in a printed circuit board for inspecting the surface of the hole for smearing of the dielectric material of the board across the edge of a metal layer. A beam splitter permits light to be directed toward the mirror along one path to illuminate the hole at low intensity and to delete the dielectric material at high intensity. The beam splitter permits reflected light to follow a second path to a viewing station or a light detector.

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Optical System for Viewing Dielectric Smear in Printed Circuit Board Hole and Deleting the Smear

An optical system includes a mirror that can be placed inside a hole in a printed circuit board for inspecting the surface of the hole for smearing of the dielectric material of the board across the edge of a metal layer. A beam splitter permits light to be directed toward the mirror along one path to illuminate the hole at low intensity and to delete the dielectric material at high intensity. The beam splitter permits reflected light to follow a second path to a viewing station or a light detector.

The drawing shows a sectional view of a circuit board with representative dielectric layers 3 and 4 and a representative metal layer 5. A mirror is formed by a surface 6 of a transparent rod 7.

The rod can be raised and lowered and rotated to scan the inside of a hole in the board. A light source 8 illuminates the hole along a path 9, 10 and 11 that includes a beam splitter 12, the rod 7 and mirror 6, and other optical components represented by lenses 13 and
14. A viewer station or a light detector 15 is positioned with respect to the beam splitter to receive reflected light along portions 10 and 11 of the optical path that are shared with the light source and a separate path portion 16.

In an alternative version of the apparatus, the rod enters the hole from below the board and the light is reflected from the outer surface of the mirror.

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