Proposal of Sulfur Corrosion Accelerated Test Method by S₈ gas for a Cased-structure Electronic Modules Installed in Engine Room

Abstract

We studied a highly accelerated corrosion test method for in-vehicle electronic modules. In the module, a circuit board on which the silver wiring was formed was stored in a casing sealed with silicone. SO₂, H₂S, S₈ gas tests were conducted under the condition of 3300 ppm/90℃/80％RH in SO₂ test, 60 ppm/90℃/80％RH in H₂S test, and 4 ppm/90℃/＜10％RH in S₈ test. As a result of examining the corrosion rate of the silver wiring, it was found that the S₈ gas test has the highest rate of corrosion acceleration. High corrosion rate is presumed to be due to high permeability of S₈ gas through silicone, in addition to its high corrosion ability to silver. Based on this result, we propose S₈ gas test as a sulfur corrosion accelerated test method.