In one of my books, published in 1980, no longer in print, so don't ask
for it, I stated that it was a bad idea to use both solder mask and
conformal coating. A quarter of a century later, I still stand by this
statement. If you can get away with it, do not use solder mask if you
are going to use conformal coating. In those days, of course, we had
wave soldering to contend with and solder mask had a real purpose to
serve. With SMD, and proper design, solder mask is not so important. At
the worst, it would be sufficient to apply it as a thin line dam to
prevent solder from being thieved from a pad. That way, the area being
masked would be a tiny fraction of a percent and not 95%++. Old habits
die hard.
Brian
Bob Wilson wrote:
> Hi,
>
> I'm studying for the CID+ test and, among other
> things, I've discovered there is a bunch of things I
> don't know or didn't realize that were important in
> the fab/assy world, even after 20+ years in the biz.
>
> I had boards that needed to be conformal coated. I
> used one fab house and a different assy house and a
> 3rd conformal coat house. Now that I'm studying, I
> see it is pretty important that the LPI and conformal
> coat "match" in compatibility.
>
> Has anyone run into this (potential) problem? How do
> I specify a compatibility between disparate
> disciplines?
>
> Sigh...I swear my fab and assy notes take up more room
> on the drawings than the biggest boards I've ever
> done, by far.
>
> Regards,
> Bob
> http://www.cstone-design.com/home.html
>
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