I just received some 10K .1% precision resistors from Digikey (part number PTF10KECT-ND). Unlike all their other passive components, which come in a normal plastic bag, these came in a metalized bag with a yellow seal that warns me that they're "electrostatic sensitive devices". They're kidding, aren't they?
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2\$\begingroup\$ Thinking about that another way: thats a lot of expense for a joke, right? \$\endgroup\$– Bryan BoettcherFeb 15, 2013 at 18:02
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\$\begingroup\$ @insta - that's why I asked. There were two such packages, so I figured there was something going on that I didn't understand. \$\endgroup\$– Pete BeckerFeb 15, 2013 at 18:11
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3 Answers
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I wouldn't discount it. Precision film resistors rely on laser trimming or very fine and precise film control. Both of which could lead to local film breakdown under high current.
Edit incorporated from comments:
Designs requiring a 0.1% precision resistor, or even two or more such resistors in ratiometric arrangements, would typically be much more sensitive to value change than less precision-dependent designs, thus it's a bigger concern: If one resistor in a set gets changed by ESD, the rest of them wouldn't be changed by the same amount, so nasty and mysterious problems will ensue.
answered Feb 15, 2013 at 17:51
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\$\begingroup\$ I frequently see resistors changing value as the circuit warms up. That's at least somewhat predictable, ESD change in value would be far more insidious. \$\endgroup\$ Feb 15, 2013 at 18:15
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2\$\begingroup\$ Adding to this: Designs requiring a 0.1% precision resistor, or even pairs of such resistors in ratiometric arrangements, would typically be much more sensitive to value change than less precision-dependent designs, thus it's a bigger concern: If one resistor in a set gets changed by ESD, the rest of them wouldn't be changed by the same amount, so nasty and mysterious problems will ensue. \$\endgroup\$ Feb 15, 2013 at 18:34
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They are not kidding. In a presentation on ESD hazards, we heard just such a tale of precision resistors changing value. I see this sort of thing to be far worse than if they simply burned out.
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If you think about it, ESD basically entails extremely high voltage ripping through the resistor, heating up what are somewhat thin regions , breaking dielectrics, etc. For anything that's precise, that's bound to affect it. Components are not always destroyed by ESD outright. Precision Op Amps, for example, when exposed to even low amounts of ESD can change their parameters such as offset voltages. Same with the precision resistor.
The best approach is to ensure you're properly grounded when working with those components and keep it in those bags.
answered Feb 15, 2013 at 18:16
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\$\begingroup\$ So the issue isn't so much like CMOS, which can be destroyed, but that its value will change. That makes sense. Thanks. \$\endgroup\$ Feb 15, 2013 at 18:22
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1\$\begingroup\$ @PeteBecker you can have ESD into CMOS without destruction, this falls into the classification of EOS (Electrical Over stress). OR it may fail later. Both very common failure modes (that are not instantaneous). \$\endgroup\$ Feb 15, 2013 at 18:39
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\$\begingroup\$ ESD wouldn't cause heat.. ESD is high voltage yes but low power. \$\endgroup\$ Feb 16, 2013 at 0:56