Ultrasonic bath, flux removal and full circuit immersion

[johnnyfp]

Does it damage a mcu or circuit if its immersed in iso prop in a ultrasonic bath and will this remove all the solder flux residue or is there still a manual task required.

Cheers.

[george graves]

subscribed.

[Rerouter]

it depends on what you are cleaning, but from memory, nasa out-right banned there use on any of there equiptment as it had a considerably high rate of tearing bond wires apart, (1 part per thousand or something like that)

also any water in packagings from humidity will be ultrasonically cleaning things that probably where assumed safe coated in plastic,

[free_electron]

Hold it ! Space circuitry uses hermeticialy sealed cerpacks. The bondwires are not trapped in epoxy but are loose.... This has to do with thermal cycling up in space...

Standard circuitboards can be perfectly washed in IpA in an ultrasonic bath. No problem at all.
IPA does not attack plastics.

The only thing you need to watch out for is things like switches and relays and piezo buzzers. Anything where ipa may stay behind.

And you need to dry the board quickly afterwards. Evaporating ipa will attrack humidity out of surrounding air that will condense on the board.

[johnnyfp]

Just curious, \why would it affect Switches and Relays, if it doesn't attack the plastic? And if the IPa permeates into the Chips like moisture does, could it be a fire hazard or other explosive if the chips heat up?

[free_electron]

Because switches and relays are not necesaarily sealed !
Ipa does not permeate chip packaging. There is no risk there
 The space parts have problems with ultrasonics, not with ipa.

[Short Circuit]

Because the liquid contains a lot of flux and moisture that came off the board. Leave some driops behind inside a switch, and the IPA will evaporate over time, but the flux will stay behind and leave a nice (isolating) film over your contacts / membranes / whatever. Also, some parts like buzzers may have glued parts inside, which glue might be affected by the solvent.

[johnnyfp]

Yeah that makes sense.

After the bath, would I then rinse the boards? (Obviously not in water)