Throttle Position Sensor Termination and Connector Reliability

Sensor reliability is of increasing concern to the automotive industry due to the desire for longer warranty periods and the proliferation of sensing applications. With today's variable resistor technology, the sliding contact interface is sometimes perceived as limiting overall throttle position sensor reliability. Any conceivable sensor, contact or non-contact, includes terminations both internal and external to the sensor. An analysis of warranty returns suggested that most returns are due to the separable electric contacts connecting the sensing element to the engine control system. We have thermal shock tested a variety of internal terminations and external connectors utilized with throttle position sensors and have, in fact, found major connector reliability concerns with some constructions. This paper reports on the thermal shock fretting performance of several internal and external terminations as a function of termination and connector metallurgy. Polymer thick film conductive/terminal and connector/terminal thermal shock fretting resistance as a function of tin thickness and underlayer is specifically explored.