Failure Analysis of Resistors
Chip Resistor F/A
SEM Lab, Inc. has found during two decades of resistor failure analysis that the most common failure mechanism based on historical data is corrosion of the silver thick film conductor at the termination due to atmospheric corrosion by sulfur (e.g. H2S). The corrosion causes the resistance of the chip resistor to increase and ultimately results in an open circuit.
Chip resistor failures and a cross-sectional image of a resistor are shown below. More information about chip resistor corrosion can be found here.