My answers marked with 2 asterisks (**) below.

Alain Savard, B.Sc.
Chemical Process Analyst
CAE Electronics Ltd.
e-mail: [log in to unmask]

-----Original Message-----
From: Hiteshew, Michael [mailto:[log in to unmask]]
Sent: July 12, 2000 12:06 PM
To: [log in to unmask]
Subject: [TN] Glass Transition Temperature (Tg) Questions

Hi,
        I've been reading up on laminate materials and have some questions
that I hope some-one can help me with:

1. What is the "glass transition" ? What is the glass transitioning from and
to? I'm guessing it's the plastic stage that occurs in a material just
before it melts.

** Temperature at which the laminate turns from a relatively hard and
potentially brittle state, to a vicious, semi-liquid stage. Epoxy used in
the boards is more likely to decompose or burn than it is of ever melting.

2. What is gained by a higher Tg in tetrafunctional and multifunctional
epoxy-glass?

** Higher Tg means that you have a better resistance to heat from any
source. Your board is more likely to keep it's shape during heat related
fabrication process or during use if it has a higher Tg.

3. What is meant by the prefixes "tetra" and "multi" as they're applied
here? Is it a reference to the number on bonds in the chemical structure of
the epoxy or glass?

** It refers to the number of linkage sites of the epoxy prepolymer.

Thanks in advance,

Michael Hiteshew
Lockheed Martin NE&SS-Baltimore
[log in to unmask]
(410) 682-1259

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