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I have read various questions and posts, but still I am not sure whether when talking about resistors, thin film means the same as metal film or not.

I read the statement that "most of the metal film resistors are thin film". That means that there are also metal thick film resistors. But does it also mean, that a thin film resistor is always a metal film type?

To give an example: Are those resistors from Yageo (http://www.yageo.com/NewPortal/yageodocoutput?fileName=/pdf/R-Chip/PYu-RT_1-to-0.01_RoHS_L_9.pdf) metal film resistors?

The "resistive" layer is not specified further in the datasheet, but since the Yageo website talks about "sputtering" I assume it´s metal film?

EDIT: From the comments it seems that "thin film" and "metal film" is often used as a synonym. This seems to be the case because metal film resistors are produced by thin film techniques. Open question seems to be therefore: What is the difference of through-hole(i.e. leaded) metal flm resistors and thin film smt resistors (beside of power and voltage rating)? Is (in general) a leaded metal film resistor comparable to a thin film smt resistor with regard to noise? If not why not if the process (thin film) and the materials are the same?

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  • \$\begingroup\$ Some info here vishay.com/doc?49562 \$\endgroup\$ – Brian Drummond Feb 24 '19 at 13:58
  • \$\begingroup\$ More information at resistorguide.com/thin-and-thick-film \$\endgroup\$ – Peter Smith Feb 24 '19 at 14:25
  • \$\begingroup\$ Well, still not sure. The vishay pdf distinguishes "thin film" from "metal film" which supposes it´s not the same. The second link however says "Thin film resistors have a metallic film..." I am not sure about the materials described in the vishay pdf (Nichrome (NiCr), Tamelox, ..) -> seems all of them are metal alloys at least. If I get the advise to use "metal film" resistors in a circuit because of low noise properties, are thin film resistors a proper choice? \$\endgroup\$ – Junius Feb 24 '19 at 16:17
  • \$\begingroup\$ It's a bit ambiguous because you say "metal film". The distinction is normally thick film, thin film, and metal foil, in lower of decreasing noise. Metal foil also has higher temperature stability than the other two. When you say metal film, you might actually be meaning to say metal foil. Thin film is definitely not metal foil. \$\endgroup\$ – DKNguyen Feb 24 '19 at 16:42
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    \$\begingroup\$ Simple questions aren't always so simple, especially when obfuscated by marketing. You might as well ask them. it appears to be a niche product so there's no guarantee that lots of people know about them if not a lot of people use them. The best temperature stability and tolerance numbers for these metal films match other thin films. The only difference is the rare times a noise figure is listed for thin film, it's -30dB whereas on the datasheet you linked it's -40dB. \$\endgroup\$ – DKNguyen Feb 24 '19 at 17:01
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If the "sea of electrons" of a metal is upset, and turned into a "sea of granules", then the electrons need to cross boundaries between the conducting granules.

This need to cross boundaries is a cause of SHOT NOISE. This shot noise is proportional to the current through the resistor (or perhaps the squareroot of the current).

You would expect carbon composition resistors to have lots of this current-dependent noise.

Now how to model the "sputtering" of tiny droplets of metal? Are the droplets in good enough contact that SHOT NOISE does not occur?

On the other hand, if the metal foil resistors use foil that is rolled out from billets of metal, we would expect few if any disruptions to the electron movement.

I've read some words about "Pauli exclusion principle" being behind these behaviors.

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  • \$\begingroup\$ This doesn't seem to answer the question at all. The OP's question re noise is through hole metal film vs SMD metal, nothing to do with foil or carbon. \$\endgroup\$ – awjlogan Feb 24 '19 at 21:32
  • \$\begingroup\$ This is exactly addressing the question. \$\endgroup\$ – analogsystemsrf Feb 24 '19 at 21:41
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    \$\begingroup\$ In what way? To quote: "But does it also mean, that a thin film resistor is always a metal film type?" and "If not why not if the process (thin film) and the materials are the same?". There is, as I pointed out, no mention of metal foil or carbon resistors, so I don't see how your answer addresses the question at all. \$\endgroup\$ – awjlogan Feb 24 '19 at 21:46
  • \$\begingroup\$ As awjlogan mentioned: I had to edit my initial queston to set a focus und the difference between the thin film SMT resistors and the leaded resistors. I find more and more references that treat thin film SMT resistors just as a subcategory of metal film - so it would be really interesting why many people suggest to use leaded types (e.g. in audio or other equipment where noise and TCR/VCR is a topic) even in places where power rating is not a concern and SMT types should (to my knowledge) suffice. \$\endgroup\$ – Junius Feb 27 '19 at 6:38
  • \$\begingroup\$ If leaded resistors have SLOWER thermal time constants, because of a LARGE clay core inside the film resistive element, then less thermal distortion will result. On different part of the Question, I recall thick-film (THICK) can be laid down on a substrate in a silk-screen method, then BAKED to fuze the resistive particles in a conductive matrix; after baking, a laser (or a sand-blast) is used to trim the THICK FILM. These were used in hybrid circuits. (and maybe still are). \$\endgroup\$ – analogsystemsrf Feb 28 '19 at 4:21

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