Hi----- from Jurassica----

An over-simplified response to ------ G10 / FR4 (the Flame Retardant G-10) (old
NEMA designations ----- equivelant to the original Mil Spec designations of 
GE and GF respectively ----

Considering G10 as the basic epoxy glass laminate, the FR4 was considered the
G10 with Flame Retardant characteristics.   The Mil spec permitted certification
of the higher level in a hierarchy of products to pertain to the products on the
lower levels and did permit certification of the GF to pertain to GE callouts on
contract drawings.

The differences in performance or processing was invariably a function of how
the laminator achieved the flame-retardant properties ---- what modifications
were made to the epoxy resin formula.  Essentially, however, the properties for
which one selected epoxy glass laminates---- certain mechanicals and moisture
resistance amongst others ----  were not compromised by the flame-retardant
characteristic.

This is a broad stroke reply ----- the supplier in the case noted was correct in
what he did.

Best to all---

Bernie Kessler

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