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June 2004

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Subject:
From:
Jeffrey Bush <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Wed, 9 Jun 2004 10:29:26 -0400
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text/plain (62 lines)
I would bet some residual copper/contaminated are encapsulated under the
mask at this site - the mask can also be thin or have poor wetting the
conductor side walls causing voids in the mask.  Properly processed PCB
surfaces with adequate soldermask application will yield a good
insulation ~ 2500 V/mil.   



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	



-----Original Message-----
From: Scott Lefebvre [mailto:[log in to unmask]] 
Sent: Tuesday, June 08, 2004 2:32 PM
To: [log in to unmask]
Subject: [TN] Soldermask Dielectric DC properties


We have a PCB that two traces have shorted and blown a set of traces on
the PCBs.  The trace width and spacing is correct for 150 V and is not a
new design.  We recently changed PCB shops.  We found some residual
moisture about 1/8" square in close proximity of two traces after
assembly and after test.  The traces were entirely covered with LPI
soldermask.  

I understand that the moisture should be removed prior to test.  My
question is shouldn't the soldermask have insulated the two traces from
the moisture?

Scott

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