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41:04 1996 |
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Phil in any way do you feel that this cracking has gotten worst since
MDA was taken out of the polyimide resins?
Jim Spendow
Smiths Industries
PH 616-241-8413
FAX 616-241-8686
______________________________ Reply Separator _________________________________
Subject: Re: polyimide bd, failure
Author: [log in to unmask] at SMTPpost1
Date: 3/31/96 10:48 PM
The failure of this type is not uncommon when using the high temp.
polyimides, Keramid 601, (and some of the loweer temp ones) which tend to be
brittle especially when the resin is not reinforced in power/ground planes
where the lands have been removed and unreinforced resin from the prepreg
fills the area between the hole wall and the copper cladding on the ground
plane. A careful horizontal microsection often reveals radial cracks
extending from the hole wall to the ground plane in these resin rich areas
and after electroless plating these partially fill with copper and if not
initially shorted will form a path for migration. The thicker the copper
cladding, the more likely for this to happen. And when getting into thin
metal core, 0.007in. thick, and using the brittle resin, it is sure to
happen.
Phil Hinton
[log in to unmask] .
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