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Circuit Board Testing Disclosure Number: IPCOM000051547D
Original Publication Date: 1981-Feb-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 1 page(s) / 11K

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The following technique can be used to find defects in printed circuitry.

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This is the abbreviated version, containing approximately 100% of the total text.

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Circuit Board Testing

The following technique can be used to find defects in printed circuitry.

Each line in the circuitry is pulsed with successive, discrete, increasing currents, and the voltage required to generate these currents is detected by an analog-to-digital converter. As the current levels of the pulses increase, a proportional voltage is detected for the total line resistance and temperature. If a flaw exists in the line that can cause undesirable current constriction, it will result in an elevation of temperature at the flaw (hot spot).

The hot spot causes a disproportional local resistance increase that will add to the total line resistance. The analog-to-digital converter output will show a disproportional voltage level requirement as the current levels rise with each consecutive pulse. Low current pulses establish a line resistivity level without hot spots versus line resistivity with hot spots. Thus, each line establishes its own resistance or voltage slope standard.

The added resistance heat of a flaw to the total line resistance causes a necessary voltage increase to maintain a constant current. This can be detected and used as an indication of an unacceptable flaw.