When to use film capacitor

Question

I've bought a bunch of film type capacitor as they were pretty cheap and I thought it was a good idea to get some and test them. (set here)

So I'm trying to figure out what's the specific application for these but for now I've only found them more usefull than other types when working with high frequency.

So, can I just use them as replacement for ceramic/electrolytic capacitors ? For example as decoupling capacitor for IC or on voltage regulators ?

(I'll confess that I really love their looks so as I'm just a hobbyist and most of the time space is not a problem, if I can use these cool looking little parts :) )

Answer 1

Though it depends on your specific caps, all the very low leakage caps I have bought for precision low drift integrators (time constants of 1 second or more) were metal polyester film. They were also very stable over temperature compared to ceramic disk, which often stated +80 -20% over the commercial temperature range.

They are good for high frequency as well and the ones you show are quite high manufacturing quality. Just don't use the physically big ones to bypass. The leads will be too long or the distance from the part will defeat the purpose.

Answer 2

All capacitors have their benefits/drawbacks depending on the application.

I've used Metalised polyester caps for high voltage/current resonant circuits for induction heating due to their low thermal drift coefficient and inherently high voltage rating. Ceramics are also good for this, however NP0 capacitors with nF ranges in suitable voltages are expensive. Metalised polyester caps are widley used in the AC/Mains arena due to those factors.

Electrolytics and Tantalums are great for high buffering storage requirements such as switchmode power supplies while augmented with some ceramics for nice current ripple performance.

Some age faster than others. They all have their application specific pros/cons.

Answer 3

Film capacitors do not suffer from piezoelectric effect compared to some ceramic dielectrics (X5R and X7R for example but not C0G), making them suitable for applications with high vibrations.

Answer 4

Film capacitors have much better linearity than most other capacitor types. They also can have relatively tight tolerances (I'm using some 2% ones) and don't suffer from significant microphonic affects. Overall they are a good choice for precision analog work.

The price you pay is they are relatively bulky and expensive.

Answer 5

The question doesn't usually arise. Generally you use ceramics in the picofarad range, film in the nanofarad range, and electrolytic in the microfarad range. You would use film rather than the other types in marginal overlap cases when audio is being passed or filtered if you can tolerate the extra size of film caps.