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Old 28th September 2004, 02:30 PM   #1
rs1026 is offline rs1026  India
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Default PCB coating

Hi,

I wanted to know what is the green color coating that is done on the PCB called as? Is it to prevent oxidation of copper??

I have etched my own PCBs using toner transfer method.Is it really necessary to apply the green coating on the exposed copper?

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Old 28th September 2004, 02:35 PM   #2
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Most commercial boards are soldered with a wave soldering machine. The coating keeps the whole board (all the copper) from being covered with solder.........
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Old 28th September 2004, 02:41 PM   #3
rs1026 is offline rs1026  India
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I still did not get the answer i was looking for. What is the name of the coating called? is it necessary to apply them to "homebrew" PCBs
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Old 28th September 2004, 02:46 PM   #4
Mr Evil is offline Mr Evil  United Kingdom
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It's called 'solder resist'. There is no need to put it on DIY PCBs. If you want to prevent oxidation then you could apply a conformal coating, which you can get in handy spray cans to cover everything, components and all.
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Old 28th September 2004, 02:48 PM   #5
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It's called soldermask. It is not needed for hand soldered pcb's.
(And mainly serves to save solder on commercial boards)
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Old 28th September 2004, 02:50 PM   #6
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The coating is called solder resist and is applied by screen printing. It is not practical to apply to homebrew boards unless you have screen printing facilities and a mask for the resist pattern.

It is not essential, just nice to have.

Measures to minimise copper oxidisation are tinning the board either by hand with a soldering iron (tedious) or tinning solution, or spraying 'conformal coating' over the finished *assembled* board (copper side only!). I've no idea how much grief it is to rework a conformal coated board though.
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Old 29th September 2004, 06:00 PM   #7
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Most conformal coats are fairly thin and I just solder right through it and then after cleaning off the flux, give it a touch up with a spray can. The only bad part is the smell of vaporizing conformal coat. I suggest not breathing it.

If I don't have conformal available, I just use clear spray paint.
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Old 30th November 2011, 03:18 AM   #8
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can i use a lacquer base spray paint? or there is specific type of spray paint? cause i don't like clear coats.
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Old 2nd December 2011, 10:10 PM   #9
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Quote:
Originally Posted by artvipinosa View Post
can i use a lacquer base spray paint? or there is specific type of spray paint? cause i don't like clear coats.
For the component side, you can spray whatever sticks on resin based materials; a primer for plastic car parts (bumpers) will often do the trick.

Then the final paint: it depends. If you intend to deflux the board after finishing soldering, which often results with the deflux entering the component side or at least the board edges, then not all spray paint will resist. 2-component paint is of course the best (and industrial soldermask is, I worked in a PCB factory years ago), but some spray paint will last as well. Better test it on a test piece before if the final paint resist deflux.

For the solder side: no spraying before soldering has finished, as it would avoid proper soldering (or even disable it).

What I do is painting the component side (with primer) first, then solder everything in place, deflux, the put special protective lacquer on sodler side.

Or: order your own PCB design from a PCB service, nicely soldermasked on both sides, even with component marking. Prices have come down a lot !

To come back to the original question (is it required for howbrew projects): yes, for the solder side. If you don't deflux the solder side, followed by a protective lacquer, then the solder and cupper traces will start corroding over time (as the flux is acid), eventually causing shorts, etc.

Last edited by AmpliFire; 2nd December 2011 at 10:14 PM.
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Old 2nd December 2011, 10:14 PM   #10
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Originally Posted by hitsware View Post
It's called soldermask. It is not needed for hand soldered pcb's.
It is needed when i solder by hand ! I am as blind as a bat lol
Even managed to get one solder bridge with solder resist !

Its to help stop solder bridges.
Its called solder resist and can come in numerous colours.
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Last edited by nigelwright7557; 2nd December 2011 at 10:41 PM.
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