Thank you, thou son of Maxwell. This is very good information,
especially the link.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of John Maxwell
Sent: Thursday, March 26, 2009 4:40 PM
To: [log in to unmask]
Subject: Re: [TN] PTH resistors arcing to LPI covered etch

Phil,
Solder masks are not designed to provide voltage isolation. I suspect
that 
the voltage is above Paschen's minimum that is 327V @ 1 atm for 7.5u 
spacing. P Basically you are dealing with a corona inception voltage
(CIV) 
and when dealing with HV layout one can never have traces beneath parts
and 
data are consistent with no solder mask either. I have a few paper that
were 
presented at CARTS (Capacitor and Resistor Technology Symposium) and an
app 
note covering corona and traces on my companies web site 
http://www.johansondielectrics.com/. Take a look at those papers for
some 
guidance and I hope this helps.

Regards,
John Maxwell


----- Original Message ----- 
From: "Phil Nutting" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Thursday, March 26, 2009 9:43 AM
Subject: [TN] PTH resistors arcing to LPI covered etch


Good afternoon,

We have been experiencing some issues with the end of metal film PTH 
resistors arcing through the LPI solder mask to the etch.  Is this
something 
others have seen?  Short of applying Kapton under the resistor, lifting
the 
resistor up or completely rerouting the etch, has anyone found another 
solution?

Thanks in advance.

Phil

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