[SI-LIST] Re: Relationship between loss tangent and dielectric constant's frequency dependence
- From: Istvan Novak <istvan.novak@xxxxxxx>
- To: Neo <neoflash2008@xxxxxxxxx>
- Date: Fri, 02 Apr 2010 09:21:27 -0400
Hi Neo,
As you may have learned from the responses so far, the good news
is that the relationship is known, and it is covered in several places;
excellent books (both old classics and contemporary works) and
web blogs. The bad news is that at high frequencies, where it really
matters for our designs, the dielectric constant and dielectric loss can
not be measured separately; they get convoluted with the
other two variables, inductance and resistance, which separately also
obey the causality constraints. Throw in surface roughness, which
has an impact on several of these four primary parameters (R L G C)
and you can see the practical challenge mounting.
This past DesignCon 2010 had several great presentations on surface
roughness and the identification of dielectric material properties.
There was also a technical panel discussion on this topic with IBM,
Panasonic, Rogers and SUN people. It summarized the challenges
and contradictions: among them the fact that there are almost two
dozen IPC standards to determine electrical properties of laminates.
The panel discussion slides were also included on the conference
CD, or you can get it from http://www.electrical-integrity.com/
Regards,
Istvan Novak
Oracle-SUN
Neo wrote:
> Hi,
> This email's title is a bit long but it is exactly a question annoying me.
> I'm trying to find out whether there is a proven relationship between a
> dielectric material's real part and imaginary part. Imaginary part is
> dielectric loss tangent. And real part is the dielectric constant.
> For a material like FR4 or Rogers, their dielectric constants all change over
> frequency. And their loss tangents are also different.
> Is there any inner relationship between the value of loss tangent and how the
> dielectric constant (real part) changes over frequency?
> Thanks,Neo
>
>
>
>
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