Moisture sensor for electronic modules

US5606264A · kind A · utility

Inventors

• James J. Licari · Whittier, US
• Aram Tanielian · Rancho Palos Verdes, US

Key dates

• Filing date: Apr 21, 1995
• Grant date: Feb 25, 1997
• Expiry date: Apr 21, 2015

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N27/048
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

Seepage of water and other impurities into hermetically sealed on plastic encapsulated modules leads to eventual device failure, as conductor material corrodes and opens, or electromigrates to establish conductive trails across a substrate, shorting the conductors. To forewarn of such failure, a sensing device defined as a separate chip is packaged in the same module with the circuit to be checked, with pinouts that can be tested with a circuit that is usually external. The sensor makes use of the moisture-induced migratory behavior that causes the problem, using a highly migratory metal or alloy to define paired electrodes spaced as closely as 2 micrometers apart. The metal of the electrodes undergoes rapid ionization and migration in the presence of trace amounts of moisture, dissolved ionic contaminants, and a small potential difference across the electrodes. Two volts applied to the sensor conductors by the sensor circuit will output a voltage if even a minute current is flowing between the electrodes permitting "go/no-go" decisions to be made regarding use of the module. The moisture which actuates the sensor, triggers the circuit long before the level of seepage and electromi…