Mihai,
In the past I have worked with many multilayer boards and have applied the
following criteria:
1) Most PC boards are made up of multiple layers (prepreg). This has to be
taken into consideration for traces on opposite layers of the board. In this
case you cannot use the 0.4mm thickness requirement because it is not 1
solid layer. I would suggest you contact the board vendor and request
information on the build. You will usually receive a cut-away drawing of the
board stating each material used and the thickness of the layers. You can
use this information when referring to clause 2.9.4.3 in EN60950 in order to
determine if it meets the requirements.
2) As for traces on inner layers of the board, I would consider it pollution
degree 1 (sealed against moisture and dust) which will reduce the normal
required spacing. Also, you may be able to reduce the spacing further if the
board meets the requirements of clause 2.9.5.
Good luck
Edward Eszlari
Bose Corporation
From: [email protected] (Jim Bacher)
Reply-To: [email protected] (Jim Bacher)
To: [email protected]
CC: [email protected]
Subject: Fwd:Isolations on inner layers
Date: Fri, 17 Mar 2000 07:50:53 -0500
forwarding for [email protected] ... Jim
____________________Forward Header_____________________
Subject: Isolations on inner layers
Author: Mihai Vintila <[email protected]>
Date: 3/16/00 7:34 PM
Hello,
I have a question concerning isolations for hazardous voltages on
inner
layers of a multilayer PCB.
The material is standard FR4.
I have read the EN60950 spec and it seems like for copper on
different
inner layers an isolation of 0.4mm would be good enough. Now what I could
not
figure is about traces on the same inner layer. In this case an isolation
of 0.4
mm is as good as it is between different layers, or should I take into
consideration the manufacturing errors (impurities, air bubbles, a.s.o.)
and
make a bigger isolation, but how much bigger?
The voltages I am working with are some of them TNV1 and others
220VAC
(mains).
Many thanks,
Mihai
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