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Test for Effect of Ionic Residue On Circuit Boards

IP.com Disclosure Number: IPCOM000037726D
Original Publication Date: 1989-Jun-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Camp, MM: AUTHOR [+5]

Abstract

The long term effect on circuit boards of different concentrations of ionic residue, such as palladium-tin colloid left from processing, is reliably determined by subjecting board samples to conditions of temperature and humidity that facilitate resistance breakdown.

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Test for Effect of Ionic Residue On Circuit Boards

The long term effect on circuit boards of different concentrations of ionic residue, such as palladium-tin colloid left from processing, is reliably determined by subjecting board samples to conditions of temperature and humidity that facilitate resistance breakdown.

Samples or test vehicles are cut from circuitized boards at various stages of processing to obtain different concentrations of ionic residue on their surfaces. Respective board samples are analyzed chemically to determine ion concentration. Adjacent conductors are wired for insulation resistance testing and given an initial leakage test at a high voltage (100 vdc), then placed in a chamber controlled as to temperature and humidity (about 50oC and 80% RH) to facilitate formation of short circuits.

For test vehicles indicating less than 108 ohms resistance, a 15 vdc bias is permanently maintained to promote metal migration. Measurements of resistance are taken three times weekly. Test vehicles showing more than 108 ohms insulation resistance are subjected to the low bias voltage only during measurements. The test chamber conditions are maintained for a time sufficient to simulate one or more lifetimes of energized circuit usage. Another high voltage leakage test at 100 vdc is given the test vehicles upon removal from the chamber.

No adverse effect is usually found with palladium and tin colloids through a range of residue from 1-19 ug./sq. cm. In fact,...