CTI is a specification of the bare laminate or more specifically the
dielectric material used in the laminate and as such is determined
by the laminate manufacturer.  The following is from UL 746A
Polymetric Material - Short Term Property Evaluations

21.1 The test method for determining the comparative tracking
index of electrical insulation materials - which is the voltage, as
determined under the conditions specified in the Standard Test
Method for Comparative Tracking Index of Electrical Insulation
Materials, ASTM D 3638 -85 (IEC 112), that causes a permanent
electrically conductive carbon path with the application of 50 drops
of electrolyte that is applied at the rate of one drop every 30
seconds to the specimen.  This test is used as a measure of the
susceptibility of the material to tracking.

Hope this helps,

Regards
John Parsons

> Hi Techs
>
> could use some education on "Comparative Tracking Index" testing
>
> what does the test consist of ?
> what factors are key to meeting specifications ?
> laminate / soldermask.....
>
> Thanks
> Wolfgang Erat
> Viasystems Canada
> [log in to unmask]
>