Is it okay to use sharpie on PCB?

[ianriley0]

Simply Put: Sometimes, coworkers and I will use sharpie to write on conformally-coated PCBs as notes to each other, with short notes such as firmware version. Am I correct in thinking that the conformal coating is enough that this isn't damaging the PCB?

Followup: What about writing on non-coated FR4?

[tszaboo]

Yes, you can write with alcohol based pens on PCBs. Just make sure it has soldermask where you write. I dont think anyone will say "oh noes, it will ruin the flammability" or conductivity.

[Ian.M]

You'd want to avoid metallic pigment inks and any black inks containing carbon, UNLESS there is a dedicated area to write on with no signal tracks.  If you are laying out a PCB that you expect to hand-annotate, provide rectangles of white silkscreen to write on  either over the groundplane or bare PCB.

Totally bare FR4 (no coper, soldermask or silkscreen) can be lightly sanded to roughen the surface and marked in pencil, and also erased.  However you need to be careful to avoid conductive graphite dust getting where you don't want it. 

[Fsck]

it's fine, but I would tack a sticker on it (solder mask) to write on. those little colored dot stickers are pretty commonly used.

[Simon]

I write on conformally coated PCB's and non. the ones we have at work do have a space for this. Note that if you write first them coat the ink will disolve and you won't be able to see what you wrote.

[LabSpokane]

A sharpie directly on the PCB /FR4 is fine. I put white rectangles on mine to write the firmware rev. I've never seen a silkscreen dissolve due to alcohol. Most silkscreen is epoxy based these days and does not dissolve readily with alcohol-based solvents.

Obviously you don't want to write across sensitive traces, or connect pads together with ink, such as the front end of an instrumentation amp, but a little common sense goes a long way.

Also, QC (rubber) stamps have been applied directly onto FR4 for many decades now.

[tooki]

I think he meant that Sharpie ink would dissolve in alcohol (which I can absolutely confirm is true).  Nobody was talking about silkscreens.

[ianriley0]

I think he meant that Sharpie ink would dissolve in alcohol (which I can absolutely confirm is true).  Nobody was talking about silkscreens.

I was actually talking about the conformal coating- just wanted to make sure that my understanding was correct and that there was no damage being done.

That being said, I think I will invest in a handheld labelmaker, since some of the areas can be hard to write small enough on

Thanks All!