ISTFA 2008, 34th International Symposium for Testing and Failure Analysis. Portland, OR, Nov. 2-6, 2008.

Thick Film Resistor Failures

Anshul Shrivastava, Ahmed Amin, Bhanu Sood, Michael Azarian, and Michael Pecht
CALCE, Center for Advanced Life Cycle Engineering
Department of Mechanical Engineering,
University of Maryland,
College Park, Maryland 20740, USA

Resistors are passive electronic devices that impede the flow of electric current in a circuit. Resistors are used in virtually all electronic systems. Their purpose in a circuit varies. They can be used to divide a voltage or to limit a current. There are a variety of resistors ranging from conventional ceramic elements, embedded resistors inside of a printed circuit board, thin film resistors, or thick film resistors. Figure 1 shows a typical thick film resistor construction. Figure 2 shows thick film power resistor package that was investigated at CALCE Test Services and Failure Analysis (TSFA) Lab. Thick film devices are “single or multilayer structures fabricated by screen printing a layer of a specially formulated paste on a substrate that can be made of ceramic, polymeric, or metallic material.”[2]. The paste thickness generally ranges from a few microns to mils [1]. The material used in the construction of a thick film power resistor include a ceramic substrate, a resistive layer, a protective glass layer, heat sink, attach material to bond the substrate to the package heat sink, and mold compound to package the entire assembly. Figure 3 shows different layers present in a typical thick film power resistor. Thick film resistors are widely used in consumer and industrial products such as timers, motor controls and a broad range of high performance electronic equipment. Thick film resistors are commonly used in hybrid circuits, for current sensing, power resistor or power conversion [5]. They are used as damping resistors for pull-ups or pull-down resistors for digital circuits [6]. Additionally, high-speed switching, snubbers, and RF systems use thick film resistors [5].

Complete article is available to CALCE Consortium Members.

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