Joyce,
There are several patterns on the B-25A test board.  The same voltage is
applied to all, so you have a number of different voltage gradients in
place.  The IPC test methods for SIR and electromigration are all based on
a set applied voltage, not a voltage gradiant.  At present, there are no
plans or revision efforts for SIR test methods 2.6.3.1 - 2.6.3.4, so the
voltages will be the same.

As to the dielectric withstanding test, here is the pertinent text:
It is run per IPC-TM-650, method 2.5.7.1, which should be free via the IPC
web site.

3.6.1 Dielectric Withstanding Voltage (DWV) Dielectric withstanding voltage
of the cured conformal coating shall be measured in accordance with
IPC-TM-650, Test Method 2.5.7.1.

There shall be no disruptive discharge evidenced by flashover (surface
discharge), sparkover (air discharge) or breakdown (puncture discharge).
The leakage rate shall not exceed 10 microamperes.



Doug Pauls




             Joyce Koo
             <[log in to unmask]
             COM>                                                       To
             Sent by: TechNet          [log in to unmask]
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                                                                   Subject
             03/08/2006 01:49          [TN] SIR spacing
             PM


             Please respond to
             [log in to unmask]
                    om






Dear SIR,
could you kindly provide the update info regarding the maximum bias for the
conformal coating SIR test?  Is it still 333 V/mm?  assume I use read out
at
100 Vdc and bias at 50 Vdc for the B-25A, am I right that bias max is
333V/mm and read out is at 666V/mm spacing?  Thank you very much.
Best regards,
                       jk
ps.  I know Concoat recommend low voltage bias, but the current test method
650-2.6.3.4 is still high voltage.  (50Vdc bias)... by the way, anyone has
table regarding the dielectric withstanding voltage per IPC-CC-830?  Many
thanks.)

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