Corrosion of Metals for Electronic Component in Mixed Gases

Abstract

In order to develop an atomosphere assessment method, we investigated the compound corrosive action of mixed gases by analyzing the products of corrosion of exposed metals and alloys, using an electron probe microanalyzer. Test pieces were exposed to mixed gases : H₂S or SO₂ (10 ppm) as a background plus HCl, HNO₃ (1 ppm respectively) or NH₃ (100 ppm) under 90% relative humidity. Test piece metals and alloys were copper, five copper alloys, silver, aluminum, iron and 52 alloy, which are most used for electronic instruments.
In H₂S background gas the results are as follows:
(1) When HCl gas is added, corrosion of nickel silver, cupro-nickel, iron, and 52 alloy is accelerated, and corrosion of beryllium copper, phosphor bronze and silver is suppressed.
(2) When HNO₃ gas is added, corrosion of all the metals and alloys is suppressed, but after corrosion once begins, corrosion of nickel silver and cupro-nickel is accelerated.
(3) When NH₃ gas is added, corrosion of brass, silver and 52 alloy is accelerated, and corrosion of nickel silver, and cupro-nickel is suppressed.
In SO₂ background gas the results are as follows:
(1) When HCl gas is added, corrosion of iron is accelerated and corrosion of other metals and alloys is suppressed.
(2) When HNO₃ gas is added, corrosion of all the metals and alloys is suppressed.
(3) When NH₃ gas is added, SO₂ gas is exhausted to produce ammonium compound, and no corrosive reaction occurs.