PCB design tips for steamy environment

Thread Starter


Joined Aug 12, 2014
I'm designing a hall effect sensor & comparator circuit and it will end up in an intermittently steamy environment as part of an espresso machine. Space restrictions make potting essentially impossible. We'll probably plan on conformal coating, but I know that is no guarantee of complete protection. Are there things I can do with layout (trace size or routing, etc) that will help protect it from moisture induced malfunctions?

The circuit will be in a roughly 6" dome shaped area, typically around 130F. Periodically, near-boiling water will flow about 8" below or bursts of steam will blow by just under the dome and I imagine some of that steam gets trapped in the dome and possibly condenses on the cooler (but still warm, around 130F) surfaces.


Joined Nov 30, 2010
Conformal coating is nearly perfect, but there are always connections to the outside world. Guess what. You can coat them, too! It just makes repairs more complicated. I would also mention that cutting slots in the circuit board can create long leakage paths where there used to be short leakage paths. Maybe a couple of slots could be used in sensitive areas.


Joined Apr 24, 2011
Unless you intend to drink whatever chemical residue is on the board I would keep it isolated from the potable water path.

Solder mask works in your favor here, so use it well. The board can be dipped or sprayed for conformal coating, and anything added later (off board soldered wires) should be brush coated.

Do not "poke" the coating during test unless you recoat it. Those pin holes will let chemicals in and out.


Joined Oct 15, 2009
conformal coating or potting... and or re-design the machine..

creepage/clearance distances between traces/circuits can be increased to deal with condensing humidity. The conformal coating is the best defense but it never hurts to have multiple backup plans.

130 deg F is basically nothing when talking components/pcbs..
Most PCB's now can be used up to surface temperatures of 105 deg C and most are now 130 deg C (UL RTI temp)