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] .