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April 1997

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Subject:
From:
[log in to unmask] (Jerry Cupples)
Date:
Mon, 7 Apr 1997 18:29:54 -0500
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Rick Payne asked:

>Rumors have it that Glob-Top BGA gave poor coplaranity. Some studies
>indicated that  glob top has significantly lower reliability than over
>molded BGA. I suspected that the high CTE and  shrinkage characteristics of
>the material  are the most significant contributor to this effect.  Anyway,
>have you guys seen anything coplaranity in real life manufacturing?

I like that rumour. We had some glob top PBGA 313 parts which tended to
break the foil off the package substrate (with lifted corners) after
reflow.

Unsubstantiated, highly emotive, rash judgment here is that they share many
tendencies toward anisotropism with Lay's brand potato chips.

Buy 'em if you must, my preference is an overmolded part. Glob top is for
engineering samples, IMO.


cheers,


Jerry Cupples
Interphase Corporation
Dallas, TX USA
http://www.iphase.com


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