What is a resistor?
Failure due to silver sulfide
Sulfur components exist in a variety of forms in the atmosphere, such as in vehicle exhaust gases and gases emitted from hot springs. These components are adsorbed by metal surfaces, where they will gradually react.
In thick-film chip resistors, sulfur gas in the air can be introduced in the gap between the protective layer and plating, gradually reacting with the internal silver (Ag) electrode to form silver sulfide (Ag2S). (See figure below.) This will cause the internal electrodes to become disconnected, resulting in failure. This failure mode is referred to as disconnection due to sulfide.