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April 2001

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Subject:
From:
Geoff Layhe <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Fri, 6 Apr 2001 09:15:18 +0100
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Hi Paul,
One method of measuring CTI is IEC 112 ( I think there is an ASTM
equivalent). According to IEC 112 the CTI is "The numerical value of the
maximum voltage at which the material withstands 50 drops of electrolyte
without tracking".
Usual values for FR4 are between 175 & 225 although a product with a CTI of
400 is available.
I know of at least one CEM 3 product with a CTI of 600 which is available
but there might be a minimum order quantity requirement.
The CTI values are on the UL yellow cards as voltage values and in the UL
Qualified Products List as 1 - 4. I don't know what the tie-in between the
different ways of quoting CTI is. If you find out let me know.

Geoff Layhe
www.lamar-uk.co.uk


> ----------
> From:         tech[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;tech
> Sent:         05 April 2001 17:51
> To:   [log in to unmask]
> Subject:      [TN] Comparative Tracking Index.
>
> I'm looking for a PCB material with a CTI Index of 0. The other number I
> have referenced is 600 ? I believe typical FR4 has a CTI of 2-3 which
> equates to a number of 100-175 (units?) I remember the test with
> electrolyte dripping between two electrodes but cannot recall how the
> results are reported. Can anyone help with this. Thanks in advance
> Paul Greene
>
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