Anyone doing conformal coatings on PCBs
PropGuy2
Posts: 367
Just a question to see if anyone has tried conformal coatings on the P1 FLIP, or P2 Edge modules.
This would be to better protect the PCBs from water, moisture or long term corrosion. Of course, I would mask off the I/O pins, uSD, and USB ports.
Is it even recommend ? And if so, what brand of coating is /was used ? Is it dipped, sprayed or other ?
Would the coating interfere with the PCB operation or digital signals ?
Anything else I should know ?
Comments
Thermal matters should be tested.
Flip less so, P2-based modules more so.
FLiP (P1) ICs generally run very cool; (though the advice applies also to P1, and indeed any uC / power part)
P2 ICs will run cool with light demands (simple code/tasks), but the power use will ramp up (and therefore heat dissipation requirements) as the users code uses more of the P2's potential.
And in addition, on any uC board, the temp rise of the power supplies should be checked also with your code running at highest demand, to ensure the conformal coating will be ok, and will allow any needed thermal dissipation.
When we tested the Edge and P2-EC modules, we attached thermocouples to the top of the P2 IC, switching PSU IC and inductor, and also to the bottom of the PCB under the switching PSU and P2 IC. Then ran various "power stress test" code samples over a period of about 5 minutes (at least until the temperature rise had stabilised). The test could be repeated with a local fan, or other techniques you might use to reduce temperatures.
I suspect if your conformal coating temp rating is suitable for a good margin beyond whatever the fan-less maximum temperature is in your project, then you might be fine to coat all the components and if needed add some external cooling (fan probably) to move air over the surface of the coating and keep things cool(er).
If your P2 runs cool to the touch with your code, then you may not need any cooling - though it's good to keep in mind that you might before committing to a tiny case! Adding the conformal coating will certainly increase the component temperatures, so what might run cool without it may become borderline-too-warm (for your application) with it.