Background
I'm filtering low-speed signals from some 5V automotive sensors. That is, their signal is within 0-5V and less than 1kHz. As such, I have selected a 1.3Kohm 1% resistor and a 0.1uF C0G capacitor, giving me a corner frequency of around ~1.2kHz. Both are 0603 packages.
The Real Question
What I am curious on is… is there more to the filter than just the values? Does the package size of the RC components influence filtering, one way or another, based on the frequencies, or even voltages, that I'm working with? Aside from things like microphonics or temperature-based fluctuations (which I'm trying to deal with by going with C0G capacitors, etc)… is there anything else I should be looking at more closely?
Best Answer
It's a reasonable question. For much, much higher frequencies than you're working at, the non-ideal characteristics of physical components become significant and at higher still frequencies, electrical components can no longer be considered "lumped elements".
However, I think it's highly unlikely that any of these considerations are even remotely important for a simple 1st order filter with a corner frequency of 1kHz.
Consider, for example, classic vacuum tube audio / musical instrument circuits working over the audio band (20Hz - 20kHz), with much larger voltages, using point-to-point wiring and much larger, leaded components.