There's no quick and easy way to order a PCB from where I live and I make most of my own. For major projects, I persuade local silk-screen printers to print the solder mask on. For minor ones, to protect the finished copper areas, I either tin them with solder or use the old method of painting it over with rosin. Unless I do this, the bare copper gets visibly tarnished in a matter of days.
However, when working on years-old company products, I often see unused solder pads that are still fairly clean and bright and take solder readily. And I don't mean the gold-plated ones. What's the trick? If they are covered with an anti-oxidation coating, it must be quite thin and transparent.
They probably coated with protective flux. A product called SK10 is popular over here:
formatting link
--
Failure does not prove something is impossible, failure simply
indicates you are not using the right tools...
nico@nctdevpuntnl (punt=.)
--------------------------------------------------------------
Generically called "organic coating", I think. Unfortunately, in North America you'll get hammered for a hazmat fee that exceeds the cost of the product when you buy any reasonable amount.
Best regards, Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
I clean, then spray home-made boards & protos with ordinary Krylon clear acrylic spray, available at most any store. It keeps boards new forever, AFAICT--more than 33 years for some of my samples, with many of those years spent stored in salt-air environments. They still look new, and you can solder right through it.
One DIY solution I have seen recommended, and have experimented a bit with myself, is to use Krylon clear acrylic protective spray. This is often used as an artist's fixative, and general light-surface protection spray.
One way to use it, is to spray the board after you've done your component installation and soldering and de-fluxing.
Another way to use it is to spray the PCB after you have etched it and cleaned off the resist and shined up the copper, but before you solder the components to the board. This will protect all of the copper, almost immediately. When soldering through-hole components, the heat of the soldering iron burns off the Krylon wherever the molten solder touches it... the usual solder and maybe a drop of liquid rosin flux is enough to create a good, solid solder joint. As I haven't tried this with surface-mount components, I can't say whether the same will be true, or whether you'd have an increased rate of failed joints.
The commonest version of this stuff is "crystal clear" glossy transparent, and isn't very visible at all on the board. I believe it's possible to buy it in a "transparent green" color as well... which would leave the board looking as if it had a conventional solder-mask applied.
The trick for applying this type of Krylon (to anything) is to make several very light applications, a few minutes apart. This will provide full coverage of the surface, without letting the liquid build up to the point where it might run, drip, or fail to dry promptly.
--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!
Krylon acrylic is a good moisture barrier, on anything that doesn't have to suffer from knocking about.
OSP on pcb's doesn't survive past the solder wave - is designed to break down. If the boards you're looking at were hand soldered, that might explain the residue on 'unused' pads.
On a sunny day (Thu, 27 Jan 2011 17:05:53 -0500) it happened legg wrote in :
I have a Motec satellite dish positioner. It has to survive cold and rain and all sorts of weather outside. I opened it up once and found they covered everything with a thin layer of what looks like paraffin wax. Probably dipped the board in a bath of molten paraffin wax, that seems to melt at about 37C:
formatting link
I must say after al these years it is still working perfectly. Maybe if the sun heats it up above 37 C it sort of re-impregnates itself... closing any holes, but still sticks to the board.
Thanks for all the replies. There's no chance of getting the particular brands of protective sprays mentioned by various people, but there *are* acrylic clear finish spray cans available even here. They're not specifically made for the electrical/electronics market and are used mostly by people engaged in decorative work. I'll get one and try it out.
Krylon spray cans (or something similar) are available at art supply stores, home craft supply stores, and Canadian Tire (automotive touch-up), above the 49th parallel.
Yes, any lacquer should protect the copper from the air. But of course, preaching to the choir, be sure that the copper is bright shiny clean, and the board is bone-dry when you spray it. And, don't quote me or bet the farm on it, but you could probably solder through it with barely a puff of smoke from burned lacquer, and the flux smoke will certainly swamp that out. :-)
Wax is great electrically. They used to use it to stabilize radio coils, but I always wondered why it didn't melt. You spurred me to realize--there are waxes of all melting temperatures. No doubt they use one with a higher melting point.
Is acrylic 'lacquer'? I thought 'lacquer' always meant 'lac' as in 'shellac', as in 'made from the shell of the lac beetle.' I read that as a kid anyhow, and it's stuck with me to this day. Hmmm...
formatting link
Nope, it seems lacquer is generic for the modern synthetics, the Diet Pepsi of wood finishes; shellac is the real thing(tm).
Hey, you're more than welcome! It's just that ISTR seeing a spray can labeled "acrylic lacquer" or something. But these days, "Acrylic" doesn't narrow it down much. Plexiglass is acrylic. There are acrylic "hobby" paints, for artsy-fartsy folks - they're as vivid as tempera, but somehow better, maybe more durable. It seems like I've heard of even acrylic floor tile, but I might have dreamed or hallucinated that one. ;-)
Shall we throw it out to the group? Hey - in how many contexts have you heard the term "acrylic?"
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.