[bobJandal]

Hello.

I am seeking to coat the underside of the pcb circuitry I have milled with something to increase isolation.

Ideally, I want something like that green stuff that is on commercial boards ?

Anyone know what that is ?

Or what a substitute is ?

Cheers,

Tom.

[sswitaj]

That green coating on commercial circuit boards is called soldermask, and, although it's an insulator, it's not really intended for electrical isolation.

It's actual function is to control the spread of molten solder.

When boards are made commercially, all the parts are inserted into the holes, and then the stuffed board is floated across a pool of molten solder. This way all the components are soldered on in one step, no holes are skipped, and there are no cold joints.

Surface mount boards use a different process involving solder paste and hot air.

In both cases, solder will not stick to the mask, so the mask contains the solder and prevents it from bridging adjacent pins and traces.

You really can't apply the mask at home, and it's not really necessary on hand-soldered boards, but if you feel you need a little more insulation, there are spray-on coatings you can get from electronic suppliers like Mouser or Digi-Key.

They are called "conformal coatings" and are typically used on boards that are expected to live in difficult environments where they would be subject to greater-than-normal corrosion or contamination.

If you're just looking to cover up some high-voltage pins and traces, go down to your local Home Depot and buy a can of liquid electrical tape. It's sort of a thick, fast-drying lacquer that electricians use to insulate exposed parts when tape is inconvienent.

One word of warning - make sure everything works well before you start covering things up. All this stuff is a bear to get off for rework.

[CJL5585]

Varnish, Lacquer (not water based), RTV silicone sealant.

[toolbox911]

I use "Bruce One Step" acrylic finish floor wax. Works great as anti oxidation and solder flux.

[vladdy]

You can buy conformal [from MG chemicals] in sparay bombs, a little pricey, but lasts quite a while...excellent for moisture sealing, at least on the sprayed side..
An 'inexpensive' alternative you can you if you are primarily concerned about appearance as well as some protection against corrosion of the solder connections, can be found [of all places] at WalMart...it's just the semi transparent paint, usually laquer based, for glass tinting... I like the blue myself..