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I'm using some 0.1% precision 10k and 150k resistors. They are thin film 0603 surface mount. For a lot more, there are also thick film types. Fundamentally and practically, what is the difference between these two?

Thin film example

Thick film example

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1 Answer 1

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Thick film resistors are screen printed; the alumina substrate is metalized then a resistive paste is deposited on top of the terminals. It is later trimmed, coated, metalized on the edges, and plated.

Thin film (or metal film) resistors are pretty much the same except instead of screen printing a resistive paste, the film is vacuum deposited, allowing for a much more uniform and controlled resistive element.

As a result, thick film resistors are generally cheaper than their thin film counterparts, but the tolerance and temperature coefficients one can get out of thin film resistors are generally better. Depending on the materials used, there is plenty of overlap between the two, but all things equal, thin film offer better performance for a cost premium.

Vishay has a decent app-note (PDF) on this.

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If thick film are supposed to be cheaper, I am wondering why they are almost 5x as expensive on Farnell. –  Thomas O Jan 5 '11 at 22:43
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@Thomas, A) Farnell's value add can add value in woefully opaque ways, B) Farnell lies, they are actually thin-film (read the datasheet), C) even if they were thick-film, getting ridiculous tolerances and Tc's with thick-film is asinine, so the volume is likely to be low and costs higher. –  Nick T Jan 5 '11 at 22:46

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