CTI in PCB manufacture

[kabl...@hotmail.com]

I understand that there are several types of laminate materials for the
manufacturing of printed circuit boards. The different types of
laminate I am aware of are: CEM 1, CEM 3, FR 1 and FR 4 etc. Each
laminate will have different CTI (Comparative Tracking Index) value.
I have the following questions about CTI:
1) What is CTI?
2) How to measure CTI? What are the measuring methods?
3) How does CTI related to PCB application?
4) Will the CTI value change during the PCB manufacturing process? e.g
the CTI value of a laminate material is 200, will this value change
after the laminate have gone the PCB manufacturing process? Which
process in the PCB manufacturing processes have impact to the value of
CTI?
5) Does FR4 laminate normally have higher CTI value than CEM 1 and CEM 3
?
6) Are CEM 1 and CEM 3 laminate material normally for Single sided PCB ?
7) CEM 1 and CEM3 laminate normally require Siver Thru' Hole process, is
this true? Can it be replaced with other process like Plated Thru Hole
process? If yes, will it affect the CTI value?
8) Can anybody enlighten me about the Siver Thru Hole, Easy Hole and
Black Hole process?

I would greatly appreciate it if anybody could answer any of my
questions.

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[fred]

CTI is a function of the organic content of the material, material
that is
able to be carbonized. For example anorganic materials such as glass
and
ceramics always have the highest possible CTI ratings and essentially
do not
track. If you will note, when using FR-4 for PCB's most standards
including
IEC950 and EN 60950 make a special case and provide a separate spacing

table. The creepage numbers generally correlate directly to equivalent
CTI
of 600V.

If you are using the FR-4 for something other than PCB's you will need
to
get exact information from the laminate manufacturer. Try to get past
the
sales people and you may still need to educate technical types as to
what
CTI is before you can get meaningful information. Chances are most all
FR-4
laminates are CTI 600V, depending on glass content..