You all,

I need some understanding and maybe some cross references to CTI Rating.

What I think I know is what follows:

1)  Under IEC 950 document at section 2.9.3 "Creepage distances" item 3 
relates that the CTI (comparative tracking index) rating  is a value 
obtained with method A of IEC 112 document; I do not have this one.

2)  If one knows the CTI then a pc board may attain a specific Material 
Group under Table 6 (Minimum creepage distances), contained in the same 
section 2.9.3 as stated above, along with knowing the Pollution degree.

3)  Also, the Material group and the Working voltage will allow a minimum 
creepage distance.

4)  There is a CTI column on some UL cards from some of the PC Board vendors 
but they do not have any data, just a dashed line.

What I want to know is:

1)  How do I find out what the CTI rating is for a PC Board from a PC Board 
vendor that I would use.

2)  Is the solder mask the only consideration or does the board material 
come in to play for the final CTI rating.

3)  What does a PC Board vendor have to do to get a CTI rating.

4)  What information do I have to specify on my PC Board Fabrication 
Document?

5)  What specific publications and other documents might explain what CTI 
exactly is?

6)  Is there a cross reference document to the CTI rating, like maybe 
IPC-840-C or information from the Solder Mask vendors?

7)  Any and all related information would be appreciated.  Please e-mail to 
me along with addressing technet for all others.



Much Thanks,
Greg Kaskey
Senior PCB Designer
Checkmate Electronics, Inc.
770.594.6000 x228
[log in to unmask]

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