From UL-746A Polymeric Materials - Short Term Property Evaluations (Nov
2000):
Table 23.1
CTI (Volts)    PLC (Performance Level Category, not programmable logic
controller)
>= 600         0
400- <600      1
250- <400      2
175- <250      3
100- <175      4
0  - <100      5

Seems kinda backwards but hey maybe the person who wrote it is a golfer.
I'd guess there aren't many materials with a PLC of 0.
Hope that does it.

Tim Reeves

|-----Original Message-----
|From: Geoff Layhe [mailto:[log in to unmask]]
|Sent: Friday, April 06, 2001 1:15 AM
|Subject: Re: Comparative Tracking Index.
|
|
|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

|

---------------------------------------------------------------------------------
Technet Mail List provided as a free service by IPC using LISTSERV 1.8d
To unsubscribe, send a message to [log in to unmask] with following text in
the BODY (NOT the subject field): SIGNOFF Technet
To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL
Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives
Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional
information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315
---------------------------------------------------------------------------------