An Integrated Sensor for Detecting Moisture Ingress in Printed Circuit Board Assemblies
Abstract Numerous applications exist where electronics must operate reliably in moist environments, and often for long periods of time. In these environments, the circuit board assemblies may experience moisture ingress, which can deleteriously affect the operation and life span of these systems. Detecting moisture ingress is therefore useful for improving system design, assembly techniques, packaging technologies and maintenance scheduling. Capacitive fringing field sensors are useful for measuring the moisture content of materials. Therefore, a capacitive fringing field sensor, implemented in printed circuit board technology with a CMOS relaxation oscillator interface circuit, is proposed for detecting moisture ingress into the printed circuit board assembly. A set of instrumented sensors was designed, fabricated and tested. The results demonstrated that when the test articles experienced prolonged exposure to moisture, the instrumented sensors experienced an 18.42% change in output value, indicating a satisfactory sensitivity to moisture ingress.