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March 1997

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Subject:
From:
Sheila Smith <[log in to unmask]>
Date:
Thu, 13 Mar 1997 09:04:57 -0500 (EST)
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John ..

CTE (coefficent of thermal expansion) & dielectric constant typically
increase above the glass transition ... mechanical strength decreases ...
the lap shear strength of an epoxy resin that is 4500 psi at room
temperature can decline to less than 200 psi above its glass transition.
Delamination of cured composite laminates above the glass transition is a
reality.  At least for most applications, delamination and increased
dielectric are  concerns.  

Sheila Smith, Tracor Aerospace Electronics Systems


At 11:20 AM 3/13/97 PST, you wrote:
>
>     Does anyone have experience of any failures attributed to
>     running PCBs at or above their glass transition temperature?
>     
>     I heard that this is not a problem and wish to confirm, or
>     otherwise.
>     
>     John
>     MBUK
>
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