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Detection of Defects in Printed Circuits

IP.com Disclosure Number: IPCOM000077998D
Original Publication Date: 1972-Oct-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 40K

Publishing Venue

IBM

Related People

Uhls, DL: AUTHOR

Abstract

This apparatus provides visual readout of the physical position of unwanted shorts between closely adjacent printed-circuit conductors.

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Detection of Defects in Printed Circuits

This apparatus provides visual readout of the physical position of unwanted shorts between closely adjacent printed-circuit conductors.

Flat circuit card 1 includes insulating substrate 2, on which a metallic conductor pattern is formed from copper or aluminum by printed-circuit techniques. A complex circuit formation is simplified to include metal lands 3 and 4, these lands including extending conductors 5-7 and 5-10, respectively. Conductors 5-7 are integral, with land 4, whereas conductors 8-10 are integral with land 3. Conductor 5 is closely spaced but electrically isolated from conductor 8, as are conductor pairs 6, 9 and 7, 10.

A card of this general configuration is tested for circuit integrity by the apparatus of Fig. 2. In this figure, the circuit pattern has been additionally simplified to show only adjacent conductors 5 and 8.

Switch 11 is momentarily closed to connect low-voltage source 12 to lands 3 and 4. If an unwanted short exists, light 13 is energized. Source 12 is selected to insure that the current flow through such a short will not disturb the short, as by burning it out with only a momentary current flow. In this manner, the apparatus allows accurate monitoring of the printed-circuit technique, insuring that even hairline shorts will be detected.

Once a short is indicated by light 13, its physical location must be located on the circuit card, since the card contains a complex circuit pattern consistin...