In order to make this work for varying layers, I believe you may have to
take the product mean of all the layers.  In other words, if you had two
differing layers, the dielectric constant may be the square root of the
product of the two.  Just an idea.

> -----Original Message-----
> From: Andy Slade [SMTP:[log in to unmask]]
> Sent: Thursday, May 06, 1999 9:40 AM
> To:   [log in to unmask]
> Subject:      Re: [TN] Dielectric Calculation
>
>      Hi Simon,
>
>      This might be a stretch, so others, feel free to beat me up...
>
>      The formula one of our laminate suppliers uses for determining
>      theortical Dk of FR-4 materials is:
>
>      Dk=6.3*(Tglass/Td)+3.6*((Td-Tglass)/Td), where
>
>      Tglass = thickness of glass cloth (in mils)
>      Td = overall thickness of dielectric
>      6.3 = Dk of glass (at 1 Mhz)
>      3.6 = Dk of FR-4 epoxy resin (at 1 MHz)
>
>      Assuming you know the Dk and thickness of each of the materials in
>      question, I don't see why you couldn't apply the above formula.
>      Change the 6.3 to the Dk of one of the materials, the 3.6 to the Dk
> of
>      the other material.  Substitute the thickness of the first material
>      for Tglass, and Td is equal to the combined thickness of both
>      materials.
>
>      Hope this makes sense...Andy
>
>
> ______________________________ Reply Separator
> _________________________________
> Subject: [TN] Dielectric Calculation
> Author:  Simon Butte <[log in to unmask]> at smtplink-hadco
> Date:    05/05/99 4:04 PM
>
>
> Hi Everybody,
>
> Is anyone know how I can figure out the effective dielectric constant when
> 2
> different
> Dielectric materials are placed together. Is there any document I can find
> in
> the web.
> Any input is appreciated.
>
> Simon Butte
> Email   : [log in to unmask]
>
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