Re: [SI-LIST] : Stackup Extraction

Mitch Morey (mitch.morey@nsicomm.com)
Mon, 16 Aug 1999 08:37:23 -0700

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Pat Zabinski wrote:

> #2 - I've been using Allegro for eight years for everything from
> single chip packages to MCMs to large PCBs, and I have rarely
> entered the material parameters into the tool. Although Allegro
> does have an integral tool that spits out some basic parasitics
> for lines (Z0, C, L, Td, etc.), I have never relied on it. The
> only time I've ever entered in the material parameters/thicknesses
> is for documentation purposes. Because it is not necessary
> to enter in the cross section (i.e., it's an extra unnecessary
> step), I'll venture a guess that many other designers avoid
> entering it as well.

Hi Pat,

I really have to take issue to this! You say you've been using it for 8 years! Incredible! But you did say you've been "using" it, not DESIGNING with it. If in your 8 years you have taken a little time to verify the results you
would've found you can easily do more things with the results. Each time I have an engineer come in a ask me what the capacitance on one of my traces, I amaze them. Not that I have to sit and figure it out, but it's right there in
front of me. I've done this on 2.4Ghz boards too. Want to know what my impedance will be on a finished board? I can tell you, let me just select a net! Does this take alot to set up? Well, with eight years of using the tool, I
wouldn't know. But after I've set up my databases based on what my fabricators do I can tell you what I'm designing to. Need resistivity of a clock trace? I can tell you. etc, etc, etc.

It's not hard! I'm not knocking you. I know many "designers" who are rowing the same boat. But what I find bewildering is you have an educational institution email address? I would think that out of most people, you certainly
would've taken the time to find the answers.

Happy "using".

Mitch

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Pat Zabinski wrote:

#2 - I've been using Allegro for eight years for everything from
single chip packages to MCMs to large PCBs, and I have rarely
entered the material parameters into the tool.  Although Allegro
does have an integral tool that spits out some basic parasitics
for lines (Z0, C, L, Td, etc.), I have never relied on it.  The
only time I've ever entered in the material parameters/thicknesses
is for documentation purposes.  Because it is not necessary
to enter in the cross section (i.e., it's an extra unnecessary
step), I'll venture a guess that many other designers avoid
entering it as well.
Hi Pat,

I really have to take issue to this! You say you've been using it for 8 years! Incredible! But you did say you've been "using" it, not DESIGNING with it. If in your 8 years you have taken a little time to verify the results you would've found you can easily do more things with the results. Each time I have an engineer come in a ask me what the capacitance on one of my traces, I amaze them. Not that I have to sit and figure it out, but it's right there in front of me. I've done this on 2.4Ghz boards too. Want to know what my impedance will be on a finished board? I can tell you, let me just select a net! Does this take alot to set up? Well, with eight years of using the tool, I wouldn't know. But after I've set up my databases based on what my fabricators do I can tell you what I'm designing to. Need resistivity of a clock trace? I can tell you. etc, etc, etc.

It's not hard! I'm not knocking you. I know many "designers" who are rowing the same boat. But what I find bewildering is you have an educational institution email address? I would think that out of most people, you certainly would've taken the time to find the answers.

Happy "using".

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