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| From [log in to unmask] Sat Apr 27 14: |
48:29 1996 |
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Genetlemen,
The definition of FR-5 is a laminate base material that will
retain 50% of its flexural stength at 150xC (it may be 125xC). This
defintion was coined by NEMA before we had such base materials as polyimide
or BT. The orginal FR-5's were white in color and had a much different
curing agent than any FR-5 available today. FR-5 sold today is nothing more
than an enhanced FR-4. The glass transition temperature is an indirect
measurement of a material being an FR-5 but the original flexural strength
defintion is the one that counts.
Doug Sober
IPC Base Materials Chairman
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