Hi Wolfgang,

CTI is a measure of the ability of the laminate surface to withstand
tracking across two electrodes placed on the surface, when an
electrolyte is dropped between them. It is a test of the bare laminate.
There are two specified methods IEC 112 and ASTM D 3638-85 I guess they
are both the same?. I have details of the IEC 112 method if you're
interested.
In general the higher the CTI the more resistant the material is to
tracking.
FR4 has a CTI of 175 - 200 although an FR4 with a CTI of 400 is
available.
FR2 & FR3 have a CTI of 300
        CEM1 has a CTI of 200 - 300
        The higher CTI materials tend to be specified for items like
washing machines, dish washers etc.

        Perhaps the CTI of any soldermask is also important for the
finished board,
        As I remember CTI of soldermasks is about 400 - 500 although I
suppose that depends on the type of mask.
        hope this helps

        Geoff Layhe
        www.Lamar-uk.co.uk
> ----------
> From:         Erat, Wolfgang[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;Erat, Wolfgang
> Sent:         08 July 1999 22:04
> To:   [log in to unmask]
> Subject:      [TN] CTI testing
>
> 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]
>