
Why are circuit boards green?  The material used to make them goes by two
names.  If it is used to make circuit boards it is called FR-4.  The same
material is used in the cryogenics industrya and marine industries as a
structural material and is called G-10.  FR-4 and G-10 are both green.  They
are not green because of a solder masking agent.  The basic ingredients are
a clear epoxy resin and glass fibers.  I am not sure what the specs are on
the resin, but if you are really curious you can call NEMA (National
Electronics Manufacturing Association) or Ciba Geigy (a major manufacturer
of epoxy resins) to find out.  As an aside, I occasionally mix clear epoxy
and glass microsphres to cast small structures for cryogenics experiments.
The proportions of glass to epoxy are about the same as in G-10.  They are
the same green color.
