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Resistance Testing for Short Circuit Categorizing

IP.com Disclosure Number: IPCOM000046605D
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Coombs, VD: AUTHOR [+3]

Abstract

A series of resistance tests are taken to determine the nature of the short-circuit defect detected by the tests. Production line testing of printed circuit (PC) boards often employs resistance testing (e.g., four-point-probe resistance measurements) to detect board internal defects, such as net-to-net shorts. The resistance values obtained ordinarily indicate only that a short exists; infrequently the values can also be used to locate the approximate position of the short. The values are not used, however, systematically to interpret what is the nature of the short. The shorting agent between nets could be electronic (the short current being carried by electrons) or ionic (the current being carried by ions).

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Resistance Testing for Short Circuit Categorizing

A series of resistance tests are taken to determine the nature of the short-circuit defect detected by the tests. Production line testing of printed circuit (PC) boards often employs resistance testing (e.g., four-point-probe resistance measurements) to detect board internal defects, such as net-to-net shorts. The resistance values obtained ordinarily indicate only that a short exists; infrequently the values can also be used to locate the approximate position of the short. The values are not used, however, systematically to interpret what is the nature of the short. The shorting agent between nets could be electronic (the short current being carried by electrons) or ionic (the current being carried by ions). Furthermore, the electronic shorting agent could be metallurgical (a coherent bridge of metal from net-to-net); or it could involve metallic contact, with metallic oxides at the contact, as with a particle of metal lying across the shorted circuit lines of the nets. The ionic shorting agent could involve a conductive organic contaminant or a conductive inorganic contaminant (a salt). Although shorted nets can be deleted and replaced by wired nets external to the PC board, it is highly desirable to know what agents caused the shorts. Such interpretations of the responsible shorting agents can aid in product yield and cost predictions and can guide process-change actions aimed at reducing short-defect rates. The conventional approach to interpreting shorting-agent origins has been to metallographically section a board. If the shorting agent can usually be observed visually, the origin of the shorting agent is ordinarily interpreted easily. This results, however, in the destruction of the board. The present system is an alternative non-destructive method for interp...