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Date: Wed, 31 Aug 2016 21:25:23 -0700
From: Larry Doolittle <ldoolitt AT recycle DOT lbl DOT gov>
To: "Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Subject: Re: [geda-user] Microwave PCB layout simulation or How to eat all
 your processing power in 3 easy steps
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Evan -

On Thu, Sep 01, 2016 at 12:07:28AM +0000, Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> On Wed, Aug 31, 2016 at 9:39 PM, Larry Doolittle <ldoolitt AT recycle DOT lbl DOT gov> wrote:
> > On Wed, Aug 31, 2016 at 03:53:25PM -0400, Evan Foss (evanfoss AT gmail DOT com) [via geda-user AT delorie DOT com] wrote:
> >> I thought soldermask issues were why most of the microwave and other
> >> RF hardware I have seen has no soldermask.
> > For the long lines, yes, depending on the designer, but eventually
> > those lines usually touch chips.  And high-speed serial lanes (with
> > the interesting frequency range now going up to 40 GHz) usually don't
> > have soldermask stripped off.
> At those frequencies I would actually think the chip would be supplied
> as bare die and wire bonded.

These days Xilinx BGAs have I/O rated for 25 Gb/s, with pretty broad spectral
content up to 40 GHz.  I'm used to microwave circuits mostly ranging from
1 - 3 GHz, and all the Mini-Circuits and Hittite chips that cover that range
(and higher) are in relatively conventional packages.

All this rambling is getting a bit off topic for the gEDA list.  Sorry.

    - Larry