A Comprehensive Study on Failure Modes and Mechanisms of Thin Film Chip Resistors

Abstract

Usually, resistors and capacitors populate majority portion of a common electrical circuit, hence miniaturization drive of any package or subsystem starts with miniaturized resistor and capacitors. In this context, thin film chip resistors are the most sought-after components for any electronic/electrical circuit due to their small size, wide range of values, military temperature range, stringent tolerance, low TCR value (recognised with PPM). Increased use of thin-film surface mount chip resistors in military and space application has led to an increased awareness of its potential failure modes in harsh environments. Thin film resistor with lower TCR (5PPM, 10PPM and 25PPM) are most preferable and widely used because of very low temperature coefficient of resistance (TCR) and high resistivity, which suits for high precision measurement application. Low temperature coefficients characteristics of thin film resistors also makes them stable and reliable. Because of their high-volume usage in recent times, failure in thin film resistor with lower TCR/PPM (Parts per Million) are also being seen more predominantly. In general, there are two types of thin film chip resistors, one is discrete type and the other is die type or wire bondable type. Discrete type chip resistor are used directly on cards, whereas, die type/wire bondable type chip resistors used in hermetically sealed HMC packages. Standard failure mode of a resistor is open mode or high resistance mode, whereas short mode failure has a very low probability. Hence in this paper, failure modes and mechanisms of both types of thin film chip resistors, with respect to common failure causes such as EOS, ESD are discussed, which is in continuation to Fabrication/Workmanship related failures discussed in our earlier technical paper. With this, all possible failure modes and mechanism related thin film chip resistors are explained. Discussion in totality always provide in depth analysis on a subject of concern, which in turn facilitate reliability assessment of the component and corrective action, if any.