Tony
IPC-4101 Spec Sheet 21 is cross referenced with MIL-S-13949/04 - GF-GFN-GFK
and NEMA FR-4.  It is described as follows:
        WOVEN 3 GLASS FABRIC
        EPOXY, FLAME RESISTANT
        Tg of 110C minimum

This document also has cross references on Spec Sheets 24 and 25 and 26 to
MIL-P-13949/04 and NEMA FR-4.

There descriptions are as follows:
        Sheet 25
        WOVEN GLASS
        EPOXY, PPO, FLAME RESISTANT
        NEMA FR-4, MIL-S-13949 - GF/GFG

        Sheet 24
        WOVEN E GLASS FABRIC
        MAJORITY EPOXY MODIFIED OR UNMODIFIED, FLAME RESISTANT
        Tg 150 - 200C

        Sheet 26
        WOVEN GLASS
        MAJORITY EPOXY MODIFIED OR UNMODIFIED, FLAME RESISTANT
        Tg  170 - 220C

In 4101 the laminate and prepreg are on the same spec sheets.

You would need to know if the original drawing specified a range for Tg.

The failures you are seeing may or may not have anything to do with the
laminate, however a different Tg could impact test and processing results.

Susan Mansilla
Robisan Lab

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