Gary,

Most laminate Suppliers will give you a nominal Er based on a 50/50
glass to resin ratio...if you talk to them they may even have a curve
of Er based on the ratio of glass to resin in a package..the true Er is
based on this ratio...Typically for FR4 it runs between 4.1 and 4.6 as
the ratio changes...for general calcualtions I use a 4.3 Er at 50%
glass and 50% resin..when you look at your package you should try to
estimate if you will be above or below this range..then you can
estimate the effect...the best way to know is to have a particular
construction tested...

Doug Jeffery
Engineering Mangaer
Electrotek, Inc.

Email: [log in to unmask]

You wrote:
>
>Does anyone know where I can find information on the dielectric
constants of pre-preg materials used for PCBs?
>
>
>Gary
>
>
>
>==================================================
>
><color><param>0000,0000,ffff</param>Gary Griffin
>
>Engineering Manager
>
>Phone (408) 501-7156
>
>Fax   (408) 437-1976
>
>Pager 1-800-759-7243 Pin: 145-1886
>
>Alpha pager email griffin_p or [log in to unmask]
>
>SABER group Interface Products</color>
>
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