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June 2001

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Subject:
From:
"Misner, Bruce" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 13 Jun 2001 09:31:35 -0500
Content-Type:
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Steve,

Maybe it's just me, but, while I can see the 2  x-sections, I don't have the
x-rays.

Earl,

The die size and assembly process would be very helpful (attachment in
vacuum?). While GaAs is a brittle material it will bend in 1.5 mil
thickness' which is probably from TCE mismatch (obviously on larger die
since the mismatches are not large) and I would think vac pressure could
contribute as Steven suggested.   Have you cross sectioned known good die to
see if they are warped also? If the attachment voiding is significant, you
might consider Ag epoxy attachment.  With a thin bond line on a good
Cu/Invar heat spreader like you have, 98% attachment with epoxy vs 60-70%
with eutectic may be thermally acceptable, depending, of course, on your
application.  Also, you can check for cracks with a dye penetrant or often
by slowly running a felt tip pen (like a red Flair) across the die while
under a microscope. Capillary action will pull the ink into the crack(s) and
obviously show it.

Good Luck,
Bruce Misner

> ----------
> From:         Stephen R. Gregory[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;[log in to unmask]
> Sent:         Wednesday, June 13, 2001 8:58 AM
> To:   [log in to unmask]
> Subject:      [TN] X-ray Images
>
> Hey ya'll!
>
> Earl has one more picture up, it's 4 x-ray images of the device showing
> voiding under the die or thin eutectic. Go to:
>
> http://stevezeva.homestead.com/index.html
>
> Since he can't post from where he's at, he's asked me to pose the
> following
> question:
>
> "How much flexibility does GaAs have and is the current eutectic contour
> too
> much (as in x-sections on Steve's site)? Can these die crack under
> additional
> thermal stress and cause the catastrophic failures shown in other images?"
>
>
> -Steve Gregory-
>
>
>

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