In a message dated 3/18/99 7:26:33 AM Pacific Standard Time, [log in to unmask]
writes:
<< Good Morning TechNet,
I have a fabrication drawing with a note with the following note.
Material: .062 laminated glass (woven fabric) base, epoxy resin, Flame
retardent, FR4. copper clad 2 oz./sq ft. Laminate must be certified to
have a minimum comparative tracking index of 175. Microsection demonstrating
compliance with copper weight, dielectric spacing, line width and use of CTI
175 or
better material shall be shipped with each lot.
I am at a loss on the CTI 175 stuff. I have reviewed IPC 4101 and don't
find a reference. I have placed a call to our material supplier but no
response yet. The TechNet
seems much faster. Can anyone provide me with a clue? Thanks in advance for
the help.
Anne Ledger
EMDS, Inc.
[log in to unmask] >>
Hi Anne!
While I'm waiting for a stencil to get here so I can run a job I got set-
up, I used http://www.dogpile.com search engine to see what I could find...and
I like to learn more stuff besides assembly junk too. But here's what it found
for ya':
Materials are separated into four groups according to their CTI (Comparative
Tracking Index) as follows:
Material group I: 600 < CTI
Material group II: 400 > CTI < 600
Material group III a: 175 > CTI < 400
Material group III b: 100 > CTI < 175
The CTI values above refer to values obtained, in accordance with DIN IEC
112/VDE 0303, part 1, on samples specially made for the purpose and tested
with solution A. Method for determining the comparative and the proof tracking
indices of solid insulating materials under moist conditions.
...and reading the stuff on different pages it looks like it has something to
do with surface insulation resistance and a materials ability to prevent
arcing and sparking while carrying specified power loads...(I think) I looked
for the test methods that were referenced above, and other test standards
(IEC 1120 and ASTM D3638-93) that I read as referenced to determine a
materials CTI, to see if I could read and understand what the heck CTI is all
about, but everybody wants money before they'll let you learn anything.
However, if you wanna go to http://www.cssinfo.com you'll find the ASTM
D3638-93 standard there, and if you'll give them a credit card number and pay
$21.95, you can download that standard online. It's precisely the standard
test used to detremine Comparative Tracking Indexs with resins.
Hope this helped a bit...
-Steve Gregory-
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