What are these "colorful" capacitors called? Why are they used instead of regular ceramic ones?
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\$\begingroup\$ I don't know what those are but I do not think they are capacitors. \$\endgroup\$– DKNguyenCommented Nov 8, 2022 at 2:15
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\$\begingroup\$ Those look like surface-mount film capacitors, maybe? They're rare, but I seem to recall they look something like that. \$\endgroup\$– HearthCommented Nov 8, 2022 at 2:20
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\$\begingroup\$ I was going to say film capacitors too. \$\endgroup\$– td127Commented Nov 8, 2022 at 2:30
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\$\begingroup\$ reasons for using non-ceramic caps: frequency response, ESR, fail mode, capacity. \$\endgroup\$– dandavisCommented Nov 8, 2022 at 5:03
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\$\begingroup\$ My first thought was smd emi filter. \$\endgroup\$– RemyHxCommented Nov 8, 2022 at 5:46
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1 Answer
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Those are SMT film caps, probably PPS or similar (The issue with SMT film is that the reflow profile becomes somewhat critical, which is why you try to avoid them).
Used where relatively high values combined with good dielectric behaviour is desired as these have lower voltage coefficient than type II ceramics and lower dielectric absorption which can matter in things like sample and hold networks.
For values up to about 100nF or so, type I (C0G) dielectric ceramics are available, but these have significantly higher dielectric absorption which can matter in some applications, so sometimes a film part is preferred.
One trap with the SMT film parts is that they tend to drift initially after reflow, so if they form part of something critical that way you may with to delay calibration for a while to let them settle, learned that the hard way.
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\$\begingroup\$ Apparently C0G absorption can be quite good, but it varies between manufacture (maybe even batch?). It's not bad in general (most sources say <0.6%, which I'm sure are all quoting some long lost original reference, not saying so independently). Have also heard stacked SMT films are prone to high leakage (relatively speaking: ~GΩ say) after soldering, as flux gets into gaps and is impossible to wash out. \$\endgroup\$ Commented Nov 8, 2022 at 12:50