board coatings

[Andy]

Is it safe to use polyurathane to protect the traces after it's been finished?  I understand that it would mean no mods or repairs.  What's a better way to do this?

[sfr]

yeah, i hafta ask - is it bad to just leave the traces as be?  they get slightly oxidized, but will that eventually become a problem?

[BillyJ]

There is some stuff called tinnit I think it is called. I belive this not only helps when soldring but also protects the board when done. I haven;t used it and could be way off but I think it is worth checking out.
Also knowing that acetone is used a lot on boards and I have used clear nail polish to protect a couple boards. I haven't had to remove the stuff but assume with some scrubbing and such could be removed completely and then you could solder away.
Again YMMV and I could be tottaly crazy and screwed those boards from ever being fixed if they get broken. Hmmm maybe I should stop trying to help.....
Anyway what is that green stuff that is one traces all the time in retail gear?

[acromarty]

Commercial boards are covered with solder resist except on the pads. The idea is that when they are wave soldered, the solder sticks to the pads but not to anything else.
I guess most solder resist materials also protect the tracks against corrosion or oxidation as well.
Many military spec circuit boards used to be "conformally coated" with some clear resin to give both mechanical and environmental protection, but then it's impossible to repair or modify afterwards.
Cheers,

[Robin]

I liked RG's comment that his board coatings consist of a fine patina of neglect. Mine too. I suppose it does make for easier mods or repairs down the road. However, he also remarked about capacitance problems associated with the accumulation of "bar funk"over time. AFAIK poly and epoxy coatings should work for a little strength/prophalaxis. I dipped a few populated boards with no high power/heat issues with no problems --- better minds may disagree.

[afranks]

The green stuff on commercial boards is called solder mask, and does
just as acromarty mentioned.  It prevents solder bridges when wave
soldering, because the solder simply won't stick to it.

The polyurethane thing is great, but only if you know you won't be
modifying the board.  Just put on an thin coat, just thick enough to
provide protection from any oxidation.  Repairs are still doable, since
you can use a dull xacto knife and a glass fiber brush to scrape off the
polyurethane.  I've seen DIY synth builders protect boards with clear
Krylon, and it seems to work well.

The other thing you can do is brush the whole back of the board with
a light coating of flux, and then flow a small amount of solder across
all of the traces.  If you get too much on there, you can always remove
the excess with solder wick.

I bought a bag of Tinnit a while back, but I've never used it.  Anyone
have any good results with it?

-alan

[Nasse]

I have small spray can made by Cramolin. The stuff is named Solderlac and it claims to be "Transparent protective coating and flux-agent for PC boards". I believe info may be found at Cramolin pages.

[The Tone God]

Anyway what is that green stuff that is one traces all the time in retail gear?

To be alittle more specific a process called Liquid Photo-imageable (LPI) is used to apply the green solder mask. Green is the default colour but there are other colours availible.

Andrew

[Andy]

I bought a bag of Tinnit a while back, but I've never used it.

do you wanna sell it?

[downweverything]

i know most supply catalogs (allied, mouser, digikey) sell "liquid tin" which is a liquid you set the etched board in and it tins the copper.  quite expensive though.  like $27 a bottle.  but i hear a bottle goes a long way.

[Mike Nichting]

so the basic idea is to protect the copper traces?? If I run solder on all of the traces that will be as good as "coating" the board??

Mike N.

[downweverything]

yeah, the basic idea is to keep the traces from oxidizing, and to make it easier to solder parts