All;

I believe the number that Louis is refering to is from the IPC-CC-110. Table
1 covers 31 standard construction types of Fr4 laminates. Each construction
specifies the number of layers of prepreg, glass style, and configuration.
Each of these 31 types is a registered laminate number with laminate
suppliers. The advantage to using these numbers is that the construction
will not vary from one supplier to another. They have all agreed to supply
laminate to this registered number. The down side is that each laminate
supplier claims that his materials are better performers than the next. Your
application may require a suppliers specific material, which may fall
outside of the registered IPC number.

The new rewrite of the IPC-D-275 (IPC-2222) will include this table of
information.

At 12:33 PM 5/21/96 -0400, Louis Dallara wrote:
>Hey all;
>The trick is to specify the material in your fab drawing, use the IPC
>number for that material that is correct dielectric constant
>for your other calcs. There's a chart listing the number with it's
dielectric constant,
> this causes the fab house to use the correct material, not what they have
laying
>around and they don't have to tweak the stackup or the line and trace width's
>on you...
>
>> From [log in to unmask] Tue May 21 12:19 EDT 1996
>> Resent-Date: Tue, 21 May 1996 11:16:12 -0700
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>> From: [log in to unmask] (Brookhaven National Laboratory)
>> To: [log in to unmask]
>> Subject: Re: Controlled Impedance - Dielectric Constant- Comment
>> Date: Tue, 21 May 96 11:36: 7 EDT
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>> 
>> Regarding dielectric constant, I have found that 4.5 is an average for
FR4 material however if you check the data sheet information from supplier
to supplier you will see a range of 4.2 to 4.9
>> 
>> Ron 
>> 
>> 
>
>
Regards,

Gary Ferrari
Chairman IPC-D-275
Tech Circuits
(203)269-3311
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