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We are copying some part of a PCB reference design. The stackup information is needed to calculate the trace signal transmission line parameters.

The reference is in _PCB.brd files. It can be opened with the Cadence Allegro Free Physical Viewer. In the viewer, how can you see the thickness of each layer, and its dielectric number?

In the same software package it also installs a SIM and MCM Free Viewer. Would that be what should be used?

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Look under "Setup > Cross-section...". In Allegro Free Physical Viewer 16.6 (and 17.2, IIRC), the cross-section report lists the layers with name, material, thickness, dielectric constant, loss tangent, etc.

If you have access to Allegro Physical Viewer Plus, it shows a much prettier graphical stackup representation, but it is still the same information, just displayed differently.

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  • \$\begingroup\$ Is the Plus version also a free download? \$\endgroup\$
    – minghua
    Commented Mar 5, 2018 at 6:25
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    \$\begingroup\$ @minghua AFAIK, no, but depending on how the Cadence licensing for your site is set up, you may have access to it. You'd have to ask the person managing your Cadence license(s). (I have it on my machine, but I believe it's because I have a full Cadence install as well.) \$\endgroup\$
    – uint128_t
    Commented Mar 5, 2018 at 7:10

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