3
\$\begingroup\$

We have a product that consists of an aluminium single-sided PCB with micro-controller and LEDs soldered to the copper side. The PCBA is shaped so that it can be bent to fit over the scalp of the user with copper side on the inside.

The 12VDC is supplied by a medically approved 2xMOPP double isolated external "brick", with the negative rail (0V) internally earthed through the earth pin of the plug.

The testing company tells us that it is rated Class IIB and must be IP22 rated. However, it is intended as a home use device, indoors only.

My question is - to pass the dripping water test of IP22, is it enough to have conformal coating or circuit waterproofing lacquer protecting the electronics?

None of the SMD pads can be touched, since the LEDs are 3535 types with hidden pads and the rest of the circuit is covered by a foam pad.

\$\endgroup\$
4
  • 1
    \$\begingroup\$ Conformal coating/PCB lacquer is mainly against moisture from condensation. It may also protect against outright dripping water if you are lucky, but I wouldn't count on it - you could still get shorts. Some manner of silicone (elastosil etc) is the best bet, but that brings other problems - pain to apply, pain to remove, easily slips into connectors etc. \$\endgroup\$
    – Lundin
    Commented May 14 at 10:04
  • \$\begingroup\$ Since it's an indoor-only product and has explicit warnings against getting it wet, I'm more concerned with getting through the certification process than with a customer wearing the product in the shower. In my l experience of using PCB lacquer, I've never seen any signs o corrosion in a PCBA treated with properly-applied lacquer. The only corrosion I've seen in a hostile environment is on the edges of FR4 boards in places where the lacquer didn't reach. \$\endgroup\$
    – Ron Brown
    Commented May 15 at 3:18
  • \$\begingroup\$ The only area that water in an IP22 test would reach is the part containing power LEDs supplied by solder-masked copper tracks carrying 350mA. No adverse operation in the short term, even without conformal coating. \$\endgroup\$
    – Ron Brown
    Commented May 15 at 3:34
  • \$\begingroup\$ I would imagine that the requirement is necessary for things like human sweat? To work in the shower you'd need IP65 and that's unlikely to happen without full encapsulation or molding. \$\endgroup\$
    – Lundin
    Commented May 15 at 6:29

0

Reset to default