[SI-LIST] : CAF and Thin PWB reliability

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From: Mellitz, Richard (richard.mellitz@intel.com)
Date: Thu Dec 14 2000 - 06:45:52 PST


Thin dielectrics between power and ground seem good. i.e. low mutuals.
planer waves, and all that. All us signal integrity types can go on and on
regarding the merits of this. There is a another angle to this...
reliability.

I remember from research, sometime in my distant past, when standard FR4
cores are too thin they have a propensity for CAF (conductive anodic
filament) growth. If I remember the research correctly, the spurs on the
rough side of the Cu greatly increase the probability for dendrite growth.
Eventually you get shorts. This is not good. I believe the voltage
dependence was not what I expected too.

Do any of you have new information or web sites that can expand on this.
Specifically I am looking for the lifetime vs. FR4 thickness data.

Regard,
Richard Mellitz
Sr. Staff Hw. Engineer
Intel, Columbia SC
(803) 216-2160

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