XP-E2 on copper Dropped in glass of Water . . .

Flashlight Modding and DIY Parts
1

I have a question that may seem obvious, but I’m hoping the explanation will help me and others to understand more about led’s and the physics behind electricity etc… in flashlight building:

Through and act of inexplicable clumsiness, I dropped an Xp-e2 on a 16mm noctigon into a glass of water I was drinking. It was a red xp-e2 if that makes any difference. Anyway, I thought there was a slight chance that if I let it dry for a while before attempting to test it’s functionality, that without the water physically present anymore present, it would not short anything in the led or the traces and allow the led to work normally.
Unfortunately this was not the case and nothing I tried will get the emitter to light again, so it goes to the pile of other parts I’ve toasted as I attempt to learn how to mod some flashlights.
My questions is: What is the reason that somewhere under 2 seconds while the noctigon was submerged, this contact with water rendered the led and/or the mcpcb board useless? Is it the noctigon itself and it’s traces that are damaged by the water, the LED only, or both?
Can anyone give an informative answer on generally how or why this happened? (the led no longer working, not me dropping it in the water. I know how that happened :open_mouth: :person_facepalming: )
Many thanks

2

well, I have used extensive amount of water on drivers, emitters, boards, etc. - ideally distilled water. I clean the parts with alcohol and blow them out with compressed air.

There are many cavities and places where water might be, in this case possibly under the emitter (depending on how much space is underneath/ depending on solder job).

edit: just 2 seconds? - aluminum or copper should only get wet on the outside, which can be dried easily.

edit 2: I am assuming the led was not running when you dropped it? just a bare board /w led

3

might want to place it in an air tight container of white rice to completely draw out any moisture trapped between the emitter and the MCPCB. The emitter wants to “float” ontop of the flowing solder when its hot, so if care is not taken to eliminate excess solder trapped between the LED and MCPCB… there could be residual water trapped in between the gap.

4

Heat up the star to 150-180dC for a few minutes on your stove the water below the LED will boil

Heating up above 200dC and you can do a reflow emitter swap, or reflow it again after cleaning the bare star and add some solder to the pads

5

(obvious question alert)… Are you sure it was working OK to begin with, before it got wet?

6

The LED wont get hurt by water it adds a resistor parallel to the LED as worst case

Maybe the LED is soldered in wrong direction to star short cut the board or in reverse polarity

7

The LED should not have died from that, make sure your power supply is working fine and you didn’t kill the LED by connecting the + and - backwards.

8

I accidentally dropped a pill with LED and star in a pot of boiling water trying to dislodge the driver, its still working today 4 (maybe 5) years later.

9

Trying to see if it’ll fizz like an Alka-Seltzer?

Shouldn’t. Even fully dedomed emitters coated with phosphor are soaked in gasoline and then rinsed with alcohol for hours with no ill effect.

Could’ve been something else, but water shouldn’t do anything at all to either the star or the emitter.

Try giving it a soak in distilled water for a few min, then heating it slightly to evaporate the DW.

Actually, a warm oven heated to 140°F-150°F, just like for drying fruit slices, would be ideal.

10

Rice If rice could draw moisture out of things, it would need to be stored in tightly sealed containers or the humidity from the air would cause it to soften and go bad.

Relatively scientific study

11

The camera I use to take every photo I post on BLF was dropped in a stream in about 1-2’ of water about 10 years ago… I had the water inside the camera for several hours (10 or more!) before I got home to work on it. I took the casing off and let it cook under a low wattage incan light bulb for a couple of days. Still works great! :student:

In this case:

1. Water is non-conductive… :smiling_imp:

2. As long as you were drinking FRESH water, it should be okay. Salt water not so much.

3. The tiny amount of water that might possibly get between the emitter and the PCB should be insignificant and non-threatening. It should also evaporate out quickly from any external heat source. I would expect the LED to work properly though, and the heat from the emitter to drive that moisture out quickly.

4. My thought is: Did the emitter possibly fall in such an unlikely manner to invoke Murphy’s Law, and fall with the edge of the dome hitting the lip of a glass container with JUST enough force to flex the dome material and damage a bond wire?