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Date: | Tue, 15 Aug 95 18:46:38 EST |
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The CTI refers to Comparative Tracking Index of Electrical Insulating
Materials. Reference documents are ASTM D3638 and test method of IEC
112. This CTI evaluates for low voltage (up to 600V) tracking
resistance of an insulating material (laminate) in the presence of
aqueous contaminates.
You may contact someone at Glasteel Industrial Laminates. These guys
appear to have considerable knowledge regarding material attributes
necessary to withstand this type of environment.
Hadco Printed Circuits
Tech Center Two / Watsonville
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Dave Hoover (408) 728-6677
Senior Process Engineer (408) 728-1728 Fax
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______________________________ Reply Separator _________________________________
Subject: Re: laminate with CTI of 400+
Author: [log in to unmask] at SMTPLINK-HADCO
Date: 8/14/95 12:59 PM
On 10 August 1995, Dougal Stewart wrote:
>> We have a customer who has been asked by his designers to
>> provide boards with a CTI of greater than 400 and a flammability
>> rating of 94V-1. They also ask if standard FR4 will comply - at
>> least I know the answer to that one.
>> I am not sure what laminate will meet this requirement - FR3
>> has been suggested, but laminate suppliers always leave off
>> the CTI when quoting electrical properties.
Dougal,
I sent a response Friday to the second-half of your post, but then
came across this message that I hadn't read yet. I would like to add a
little more to the post I made Friday to help make that information a
little more useful.
When you speak of CTI, I'm not exactly sure what is meant by that...I
don't believe it's coefficient of thermal expansion (CTE) because the
values are expressed in parts-per-million...and I can't think of why
anyone would want a laminate that has a CTE of 400ppm. So I'm assuming
what it is that you're asking for is laminate that has a glass transition
temperature (Tg) of 400 degrees F. or above...that works out to 204.44
degrees celsius (400-32 x 5/9=degrees C.)...I'll list below the important
properties of the materials I refered to in my last email:
(Note: All temperatures are in degrees C.)
Reinforcing Materials
Dielectric CTE,ppm/degree C.
Constant
Material @ 1 MHz Long. Radial
E-Glass 5.5 5.5 5.5
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