I keep on hearing that no-clean solder paste or flux is bad for analog or digital signals because it makes analog signals "noisy" and promotes cross talk on digital signals.
Like this claim:
Flux residues can add noise on analog-to-digital conversion circuits.
Source: Mike Jones - Expert Comment
'No-clean' fluxes have been found to be electrically conductive and are not easy to clean (requiring strong solvents and scrubbing).
Source: answer to "Why do we need to remove flux from circuit boards?" - Spehro Pefhany
I realize that it's probably not good to have anything on the surface of the PCB between traces. I realize that corrosion is bad. But if no-clean residue or RMA flux residue is left on a board, what happens? Most people say, it's bad don't do it.
My question is, through what mechanism does leaving a residue on a PCB affect performance? How does it affect performance Is it a parasitic resistance? Parasitic capacitance?
I could see a promoted parasitic capacitance with a residue and leakage current. How much?
Is there some other mechanism besides promoting cross talk that I'd have to worry about?
Has anyone ran into this problem directly?
What is the mechanism for this noise? Can it be traced to some physical process?