[SI-LIST] Re: What is the acceptable minimum pre-pregthickness for volume manufacturing?
- From: "Chris Cheng" <Chris.Cheng@xxxxxxxxxxxx>
- To: <George.Dudnikov@xxxxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Thu, 7 Sep 2006 15:26:35 -0700
George,
Welcome to the Si-list.=20
I am always curious about this single ply reliablity in PCB.=20
Does the main benefit of ZBC on single ply reliability came=20
from the material itself or is it the extra hypot test to=20
ensure reliability ? The PCB material guys insist on double ply
everywhere but when it comes to thin core, it is ok to single
ply all the sudden.
>As was previously mentioned on this thread, single ply
>dielectrics can be risky business when you think about voltage
>differential and the potentially catastrophic effect of any type of
>inclusion or conductive path between planes. Prepreg dielectrics have
>exposure to foreign material and inclusions during the glass yarn
>manufacturing, prepreg coating and PCB lamination processes. There is a
>significantly elevated risk of yield loss due to hard power ground
>shorts or field issues due to latent P/G shorting from =
electromigration.
>One of the benefits of licensed ZBC materials, in addition to certain
>structural specifications, is the requirement to hypot test the cores
>and finished PCBs to a minimum of 500VDC breakdown voltage using
>prescribed ramp rates and dwells. Film based dielectrics have the
>advantage of eliminating the glass weave and have even better voltage
>breakdown performance.
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