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<title>Thick Film Resistor Failures
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<center><i>ISTFA 2008, 34th International Symposium for Testing and Failure Analysis.
Portland, OR, Nov. 2-6, 2008.</i>

<br><h2>Thick Film Resistor Failures</h2>
<br><br><b>Anshul Shrivastava, Ahmed Amin, Bhanu Sood, Michael Azarian, and Michael Pecht</b><br>
CALCE, Center for Advanced Life Cycle Engineering<br>Department of Mechanical Engineering,<br> University of Maryland,<br>College Park, Maryland 20740, USA<br>



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<b>Abstract:</b>

<p>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].
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<p><a href="../../fulltext/2008/Thick_film_res_TSFA_final.pdf">Complete article</a> is available to CALCE Consortium Members.</p>


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