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JANUARY 2021 I DESIGN007 MAGAZINE 51 Your margins decrease as speeds increase. You've got to be improving your design meth- odology; you can't do what you were doing two years ago, you've got to be improving. That's what engineers and designers are get- ting paid to do. If you're starting to work on PCI Express 5, you can't use the same tech- niques you were using with PCI Express 3. Shaughnessy: Are standards helpful in doing the stackup? Hargin: Yes and no. The IPC-4562 standard for copper foils is helpful in terms of copper thick- ness; it gives you a definition of copper thick- nesses: how thick is half-ounce copper, and how thick is one-ounce copper. But it handles copper roughness, which is much more impor- tant these days, in a nebulous way. The defini- tions in 4562 about copper roughness are not universal, and they're not current. Glass is defined in IPC standards, but each manufacturer can create their own wrinkle in how they implement that standard. Some com- panies like Nan Ya, where both Happy and I used to work, have their own glass manufac- turing. But other laminate vendors source their glass from multiple sources. That could be a source of variation. Holden: Does the Z-zero impedance analyzer replace the HyperLynx analyzer? How exactly is this used by Siemens EDA? Hargin: We both use the HyperLynx 2D field solver. I've been using that from the get-go in an OEM relationship with Siemens EDA. The HyperLynx 2D field solver is also used by the HyperLynx SI and PI simulator, and it's also used in Xpedition. The Z-zero software, Z-planner Enterprise, can send data to and from the stackup editor that Xpedition and HyperLynx use. In our envi- ronment, there's a lot more detail. For exam- ple, in the materials library, we have about 150 materials, and probably another 10 materials, I would say, by the end of this year. We have a lot more granularity, as it relates to stackup and materials, and we send that data to and from Xpedition or HyperLynx. The other thing we do that's a little different is that our tool realizes that a given production part number may have multiple versions of a stackup. Fabricator A, B, and C, version one, version two, etc. A lot of people think of imped- ance and stackups as kind of a monolithic con- cept, but they're pretty nuanced, in fact. Shaughnessy: Bill, is there anything we haven't covered that you'd like to mention? Hargin: Just that stackup design has been a passion of mine for a long time. The seeds of Z-zero were planted in my mind back in my HyperLynx days. And I thought that a tool should exist that does what my Z-plan- ner Enterprise product does. I thought that if speeds kept increasing, engineers would need to have a tool that handles the granular details of stackups. And that's the journey that I've been on with Z-zero. We spoke with you a few months ago about Siemens EDA distributing my Z-plan- ner Enterprise product. As Max Clark and I mentioned at the time, we realized we were both pursuing the same goal: To take manu- facturing knowledge and move it to the left in the design process with an EDA tool that would handle all the uncertainties in stackup design. Shaughnessy: Well, congratulations, Bill. Thanks for speaking with us today. Hargin: Thank you, Andy, and Happy, it's always great talking with you. Holden: Thanks, Bill. DESIGN007 A lot of people think of impedance and stackups as kind of a monolithic concept, but they're pretty nuanced, in fact.

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