Conformal coating after repair

[gjvdheiden]

My house has a ventilation unit that (Zehnder ComfoAir Q350) keeps the temperature (warm in winter, cold in summer) inside. (TEMP_SENSOR_ODA ERROR if someone searches on the net for this problem)

I noticed the unit didn't turn on, the unit complained that a sensor has an error. Took the unit apart, according to the nice service manual, digged in and found the thing. Replacement sensor unit is of course meant as to be easily swapped. The actual sensor IC that is used on the sensor unit is a SHT30-DIS. That sensor is on a PCB that comes out of a nice potted holder and has formal coating on it. (See picture I grabbed from the net) This sensor practically lives outside, because measures the incoming are temperature an humidity. The rest of the PCB that is potted I'm guessing it translates I2C (from the sensor) to CAN bus.

But the problem was a SMD ceramic capacitor that wasn't coated very well or the coating leaked. It was totally corroded and fell apart. Due to corrosion a piece of the PCB trace was eaten away. Checked, and is is a bypass cap and the corroded trace was Vdd. I didn't took pictures, too small. Don't have proper optical inspection yet, just one of those el cheapo magnifying glasses you can put on your head.

With the minimal tools and a cap that was to big in size I did manage to fix it. The bigger cap is in an angle, and one side conveniently bridges the PCB trace that was eaten away.  Hurray.

But I don't know how to repair that conformal coating. (After I taped of the sensor part of the actual sensor chip). What is the sensible way to repair the coating to protect the pcb and cap? Do I need to buy something from e.g. Digikey? Or can I just use metal paint in a spray can? Or a blob of glue?

Replacement sensor looks very different by the way.

edit: spelling

[Jeroen3]

For such small area after rework the easiest way is to use this: Electrolube APL15ML

The alternative is using spray on coating like PLASTIK 70, but per spray bottle reasonably expensive for such small item.

The beunhaas solution would be transparent acrylic nailpolish.

[gjvdheiden]

For such small area after rework the easiest way is to use this: Electrolube APL15ML

The alternative is using spray on coating like PLASTIK 70, but per spray bottle reasonably expensive for such small item.

The beunhaas solution would be transparent acrylic nailpolish.

"The beunhaas solution"  Sorry tiny non-dutch speaking part of this forum.    Very tempting. Thank you for the suggestions. Didn't even know where to look in the big pile of stuff you can buy online.

I did had some trouble with ordering isopropanol from Farnell a while back, it got stuck in Germany somewhere. Border control didn't like it or something.

[Haenk]

I have a can of this:

https://www.voelkner.de/products/19467/Kontakt-Chemie-PLASTIK-70-74313-AA-Isolier-und-Schutzlack-400ml.html