What's the wax-like stuff on some PCBs?

I recently purchased several PCBs from a supplus store to get some buttons and else off it for my projects. I realized the entire board front and back is covered with some thin transparent wax type of thing, which surprised me a bit. It you desolder components from it the "wax" seems to lift off the board when hot but returns to the board when cold. I've just made my first PCB (still in mail) so I wonder if a cover layer of that is needed on top of a soldered PCB. BTW, all the components on those boards are covered with the same stuff, making reading their markings pretty hard. So what is that cover? Anyone has an answer? Thanks.

I can’t say I have ever seen this wax type stuff covering a whole board…

Got any pictures?

Mowcius

Depending on what the pcb's were from, it sounds like it could be conformal coating. It's generally used to protect boards in harsh environments.

Here's a picture. The whole board is covered with it. It feels like rubber with quite a bit friction if you want to drag your finger tip across it. For comparison I have a different chip without the coating.

I wish I had a 7805 without coating but all my 7805's are taken from these boards. :-[ cheap this way.

BTW, the other chip is at22v10L 25PC. Any good use for it?

Here's a picture. The whole board is covered with it. It feels like rubber with quite a bit friction if you want to drag your finger tip across it. For comparison I have a different chip without the coating.

Yeah, it looks like some kind of conformal coating to me, too - have you tried any solvents on it (acetone, alcohol, gasoline, etc)?

I wish I had a 7805 without coating but all my 7805's are taken from these boards. cheap this way.

I would try some solvents and scrubbing - maybe do some googling on conformal coatings and solvents, maybe something common can be used?

BTW, the other chip is at22v10L 25PC. Any good use for it?

According to a google search, its a "High Speed UV Erasable Programmable Logic Device" - it definitely looks interesting, but I am not sure how you would erase it or program it (theres no window on it...)?

It might be a urethane or silicone coating; I am just guessing, but given how you describe the texture, it seems like it could be one of those. MG Chemicals make solvents for conformal coatings, but there might be something more generic that will work...

[edit]This page may help...

http://www.paryleneconformalcoating.com/liquid_coatings_removal.htm [/edit]

You know the regulator will operate just fine with the coating that's already on it. As long as you can make good solder connections to the pins why worry or labor over the existing coating?

Lefty

Hey thanks guys. Just learned another thing today. Yes, I can just use the components with the coating on. I guess I won't need the coating for my designs just yet, most of which should sit indoor.

It’s generally used to protect boards in harsh environments.

That was what I thought. Maybe if the board was to be used in a high humidity environment or similar.

I have turned a whole board into a resin block before :wink: Now that was fun!
Made it waterproof alright!

Mowcius

BTW, the other chip is at22v10L 25PC. Any good use for it?

its a programmable logic chip, in a nutshell its a matrix of fuses and logic gates, program or "draw" out what logical function(s) you want the chip to do and you have a custom chip

but designs in that series are not used much any more, which makes the effort of learning it a little deprecated (fpga's use similar design), and the programming hardware is rare, googling for a DIY version mostly links to the same dead, blank project page, I snagged a old parallel port chip burner that supports a big list of stuff, but only dos

now were into a production, though your luck may vary ;)