A multi-stress screen for corrosion-susceptible chip resistors

Surface mount thick chip resistors are amongst the simplest and most inexpensive of all components used in electronic circuits and systems. However, resistor failures in some systems are often responsible for complete functional breakdown. Typically, resistor failure modes include open circuits, resistive shorts or variations in resistance indicating intermittent failure. Corrosion is currently believed to be the number one failure mechanism for chip resistors deployed in developing markets such as Central and Latin America, Asia, India and Pacific regions where aggressive corrosive conditions are prevalent. The objective of this study is to develop a stress screen to identify or screen out corrosion-susceptible parts. The twelve precision thick chip resistors representative of resistors in contemporary printed circuit board assemblies are subjected to a well-defined multi-stress screen which comprises thermal cycling and flowing gas exposure. The combination of thermal cycling and corrosive gas exposure is shown to provide an acceptable screen to identify corrosion-susceptible parts by replicating corrosion observed in developing market environments.