Those DK values are average values only, and for  frequencies of 1 MHz.
The dielectric constant of base materials depends on the resin content
of the base material, because it is a composite value of E-glass with a
DK of 6.6 and neat resin (e.g. epoxy resin of 3.6).

For epoxy/glass (FR4), irrespective whether difunctional or
multifunctional, the DK range is from 4.3 (e.g. 0.15 mm laminate of 2
plies 1080 glass fabric, with a retained resin content of 56 %) to 4.8
(x plies of 7628 glass fabric, 41 % resin content, e.g. 0.33 mm, 0.51
mm, 0.71 mm, 1.50 mm). The same applies to polyimide/glass, with DK
values from 4.0 to 4.6.

And it is not possible to manufacture any laminate thickness for a given
dielectric constant: e.g. it is not possible to manufacture a rigid
epoxy/glass laminate (1.5 mm) with a DK value of 4.3. This would require
approx. 23 plies of 1080 prepreg, resulting in slippage in the press,
and manufacturing cost that nobody could pay for (23 plies 1080 vs. 8
plies 7628 glass ).

For teflon laminates a DK value cannot be stated without the MIL
designation, e.g. GX, GY, etc., because the nature of this designation
also determines the construction of the laminate: A GY laminate
automatically has a lower DK than a GX material due to the use of skived
PTFE (= pure PTFE, without glass fabric reinforcement) in the laminate
construction together with glass reinforced prepreg.

Manfred Huschka
AlliedSiignal Laminate Systems Europe
 ----------
Von: No Name
An: Armando Saldana
Cc: [log in to unmask]
Betreff: Re: dielectrics for dif materials
Datum: Mittwoch, 22. Januar 1997 19:43

Microsoft Mail v3.0 (MAPI 1.0 Transport) IPM.Microsoft Mail.Note
From: No Name
To:  Armando Saldana
Cc:  [log in to unmask]
Subject:  Re: dielectrics for dif materials
Date: 1997-01-22 19:43
Priority: 3
Message ID: D46E11B7BE74D011B4D600805FD4C991

 -----------------------------------------------------------------------
----- --

Dielectric Values
FR-4 = 4.8
teflon = 2.4
Polyimide = 4.3
GETAK = 3.9



On Wed, 22 Jan 1997, Armando Saldana wrote:

> attn: all in the TechNet Forum!!
>
> Can anybody out there tell me how I can
> get the dielectric values for different
> kinds of materials?
>
> FR4 = ?
> Polyimide = ?
> Teflon = ?
> Kapton = ?
> etc. = ?
>
> can i call a website or would ipc have this kind of
> information handy at all times?
>
> i need this info yesterday so anybody with
> any kind of help or hints would be greatly
> appreciated!!
>
> thanks in advance!
>
>
> Armando Saldana
> [log in to unmask]
>
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