[SI-LIST] Re: Use of Ceramic substrates at High Frequencies
- From: "Daniel, Erik S., Ph.D." <Daniel.Erik@xxxxxxxx>
- To: APANNIKK@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Tue, 18 Sep 2001 07:39:23 -0500
Anil-
Although Raymond and Scott have already pretty much answered your question,
I thought I could maybe add a few more thoughts.
The loss tangent in ceramic (~0.0002) is *much* less than that in FR4
(~0.01-0.02) -- perhaps a factor of 100 better. As Scott pointed out, this
makes a *dramatic* difference at higher frequencies.
You mentioned W metallization. In the thin film ceramic processes I am
familiar with, there is only a very thin (100s of Angstroms) W or TiW layer
on the surface of the ceramic to promote adhesion of a much thicker layer of
gold. Even for quite high frequencies, the skin depth is still much larger
than the thickness of this W/TiW layer, so the bulk of the current flows in
the gold, hence the gold conductivity dominates.
Another feature of thin film ceramic processes that we often find attractive
(or necessary) is very fine line geometries. Many vendors can provide 1 mil
lines and spaces with no problems, and some can do somewhat better.
- Erik
==================================================================
Erik Daniel, Ph.D. Voice: (507) 538-5461
Mayo Foundation Fax: (507) 284-9171
200 First Street SW E-mail: daniel.erik@xxxxxxxx
Rochester, MN 55905 Web: www.mayo.edu/sppdg/
==================================================================
> -----Original Message-----
> From: Anil Pannikkat [mailto:APANNIKK@xxxxxxxxxx]
> Sent: Monday, September 17, 2001 6:41 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Use of Ceramic substrates at High Frequencies
>
>
>
> Hello
> This might be a very naive question, but can anyone please
> tell me as to
> why ceramic substrates are used so much in the microwave
> world as compared
> to organic substrates. I know the dielectric loss in ceramic
> substrates is
> much lower than the organic substrates, but the skin
> resistance in ceramic
> substrates (due to W metallization) is much higher. So why is
> the dielectric
> loss more important than skin R?. Or is the choice more due
> to other factors
> such as cost?
> Thanks
> Anil
>
> Anil Pannikkat
> MTS Package Development Ph : 408-544-7542
> Altera Corporation Fax: 408-544-6419
> 101, Innovation Drive, M/S 4101 Email: apannikk@xxxxxxxxxx
> San Jose, CA 95134 WWW: http://www.altera.com
>
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