At 05:06 PM 6/15/99 +0800, Lum Wee Mei wrote:
>I quite like the reason Bob gave. Solder mask is green so as to blend with
the light greenish colour of the
>printed circuit board before masked. The light greenish colour of the
printed circuit board if my memory
>does not failed me comes from the combination of the resin and epoxy being
used. The percentage between
>them and also the woven glass cloth give a slightly different colour.

I'd say that this begs the question. If solder mask is green to blend with
the color of the plastic laminate, first of all, why should it blend? And,
secondly, why should the *laminate* be green? Epoxy resin itself is not
green; rather it is clear.

I've seen specifications on many drawings requiring that the solder mask be
green, but I've never seen a reason stated anywhere.

My suspicion is that, first of all, someone, somewhere, decided that a
particular grade of epoxy/fiberglass laminate should be colored green, to
distinguish it from other grades. I couldn't find my old copy of
MIL-P-13949, and it is distressing to be reminded once again that, still,
all these standards and their descendants are available only for sale at a
fairly stiff price, and not for free download, especially considering that
the MIL standards, at least, were written with public money.

Now, another related question: why is white more or less the standard color
for component legend ink when it's been considered for years that yellow is
a better color to use, by those who specialize in such details (like Preben
Lund), due to the increased contrast.

I'd think that an opaque, or semi-opaque, solder mask might be easier to
inspect.

[log in to unmask]
Abdulrahman Lomax
P.O. Box 690
El Verano, CA 95433

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