The trace spacing is violated either by etching, contaminates or
possible voiding the dielectric that insulates the tracks.  If the
breakdown involves nets that are connected to utilities, the issue could
be CAF if operating for sometime, or a registration issue with a TH pin
to the plane layer.  X-Ray and microsection could provide some useful
information along the affected net and failed areas if indicated by
damage.  The 9 KV DWV you state only applies from layer to layer - the
inter-net spacings can be violated any where along the signal run or
utility.  



Jeffrey Bush
Director, Quality Assurance and Technical Support

                          76 Technology Drive - POB 1890
                             Brattleboro, Vermont 05302-1890
                                Tel. 802.257.4571.21 Fax. 802.257.0011
                                    [log in to unmask]

                              http://www.vtcircuits.com	


Bill Higinbotham wrote:

>We are using a multilayer FR4 board with 12 mils between layers and 
>getting breakdown between traces on different layers.  The voltage is 
>about 3500 V peak.  THis board should be good for 740 V/mil x 12 or 9 
>KV.  I wonder if it is excessive leakage due to moisture absorption?
>
>Bill
>
>Bill Higinbotham
>RFL Electronics Inc.
>E-mail : [log in to unmask]
>Voice: 973.334.3100 Ext. 386
>Fax: 973.334.3863
>
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