Polystyrene caps

[IvoS]

I have a low THD 10kHz oscillator PCB board that has populated polystyrene capacitors. It needs to be cleaned very well from flux residue because it is using current feedback OPamps. Any PCB leakage and flux residues usually causing high frequency oscillation. I use medical grade 91% isopropyl alcohol (got it from walgreens). The question is, can submerge the whole board with those polystyrene caps as well? The other parts on the board should be no problem.
Thanks.

[Ian.M]

http://kmac-plastics.net/data/chemical/polystryrene-chemical-resistance.htm

It looks like it should be OK.  Don't leave it immersed overnight!  Caution: the markings may come off.

[bd139]

Check the trimpot data sheets as well.

[exe]

Is this really needed? How big is feedback current?

I don't encourage people leave flux on the pcb, but I  prefer using "no clean" fluxes that are non-conductive and non-corrosive (but don't trust package labels, not all no-clean fluxes are really no-clean). That's because cleaning flux from underside of ICs can be a challenge.

(of course, for low-leakage applications leaving flux is not an option).

[Ian.M]

Check the trimpot data sheets as well.

Yes.  If the pots aren't fully sealed and resistant to IPA you are in for a whole world of grief (or even if you put a hot board into cold IPA so the internal air pressure change overwhelms their seals).   If necessary, de-solder them, clean the rest of the board then re-solder them with minimal flux, and spot-clean round them with IPA, brushes and Q-tips.

[Gyro]

http://kmac-plastics.net/data/chemical/polystryrene-chemical-resistance.htm

It looks like it should be OK.  Don't leave it immersed overnight!  Caution: the markings may come off.

I followed that same chemical resistance data wrt Polystyrene. There was no visible surface damage but I found that contact with IPA increases their leakage current massively for a longish period of time (overnight). Granted I was using one in a Picoammeter application but this was a quick surface swab rather than immersion of any significant duration....

https://www.eevblog.com/forum/projects/picoammeter-design/msg790190/?topicseen#msg790190

[IvoS]

OK thanks. I will wash it in IPA with brush then rinse with water and dry quickly. Those trim pots are Bourns 3296 series, sealed.