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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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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 have said film vacuum deposited, allowing for a much more uniform and controlled resistive element. They then undergo similar finishing steps to trim, coat, and metalize the edges.

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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  • \$\begingroup\$ If thick film are supposed to be cheaper, I am wondering why they are almost 5x as expensive on Farnell. \$\endgroup\$ – Thomas O Jan 5 '11 at 22:43
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    \$\begingroup\$ @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. \$\endgroup\$ – Nick T Jan 5 '11 at 22:46
  • \$\begingroup\$ Thomas : thick film are £0.045 , but thin film are £0.435 , how did you find that thick film is 5x expensive ?? \$\endgroup\$ – ElectronS Feb 3 '16 at 14:12
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My fifty cents to Nick T's answer.

For thin film resistors, after metal deposition (and before trimming) the foil undergoes photo-etching (an important manufacturing step):

the surface is coated with a photo-sensitive material, then covered by a pattern film, irradiated with ultraviolet light, and then the exposed photo-sensitive coating is developed, and underlying thin film is etched away.

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