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March 1999

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Subject:
From:
glenn pelkey <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 19 Mar 1999 09:18:41 PST
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Does anyone have information on the effect of applying epoxy around SMT
components after they've been soldered?

The situation arises due to space limitations on the board.  A die
encapsulant is used to protect wire bonds but overflows onto adjacent
chip caps and resistors.  Two conditions occur; fully encapsulated
components, and partially encapsulated components.

I have some concern with the mechanical stress that it may see at
different use temperatures.  But tell me if my thinking is correct here:
The epoxy is cured at an elevated temperature (150 to 160 C).  So, given
that it is stress free at the cure temperature, at room temperature, the
epoxy should be in tension.  Right?

Thanks for your input.  This will probably result in an experiment to
prove out the design.  But, maybe there's some technical paper already
published or personal experience that would help design the experiment.

Glenn
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