I've come across a LED flashlight that has rather curious design. The flashlight is rather powerful - it can notably heat up in "turbo" mode and so the driver definitely deals with some serious amounts of heat.

It runs on one AA battery and so has usual cylinder battery compartment with a screwed-on cap on one end and the LED, reflector and driver on the other one - this part is usual. However if I remove the cap and look into the compartment I see the "plus" terminal in the compartment bottom center and immediately beneath is the PCB all stuffed with PCB-mount resistors - yes, I look into the cylinder and the seemingly uncovered PCB is at the bottom. Maybe the "plus" terminal is on the PCB itself - I'm not sure.

I can't see more details because the compartment is rather deep and narrow.

Unless there's some clever protection of the PCB I expect it to die of corrosion quickly if there's a minor leak of electrolyte from the battery. In all other flashlights I've seen the compartment bottom has a plastic or metal piece that completely separates it from the driver. This is not the case here - the PCB is clearly visible at the compartment bottom.

Is there any easy way for protecting a PCB in such design like perhaps some varnish-like coating that would cover everything and protect it from electrolyte?


Conformal coating can offer some protection, but the exposed area of the PCB for connection to the battery will still be vulnerable.

  • \$\begingroup\$ Suppose the "plus" terminal is made of stainless steel and so not very sensitive to corrosion and the coating is applied to all the PCB up to and including the terminal edges - does this have any chance to save the PCB? \$\endgroup\$ – sharptooth Aug 26 '13 at 12:47
  • \$\begingroup\$ With the correct coating, yes. Simply choose one that is resistant to the electrolyte. \$\endgroup\$ – Ignacio Vazquez-Abrams Aug 26 '13 at 12:54
  • \$\begingroup\$ @sharptooth: The reason stainless steel is resistant to corrosion is that when exposed to air it rapidly forms a coating of chromium oxide. Chromium oxide is chemically very stable and is also optically transparent. Unfortunately, it is a very poor conductor of electricity. I'd figure that any metal which comes in contact with battery electrolyte will need to be replaced, and focus on ensuring that any metal which could come in contact with battery electrolyte can be easily replaced. \$\endgroup\$ – supercat Aug 26 '13 at 16:16

protected by Kortuk Aug 26 '13 at 14:05

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