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I am designing a PCB. My PCB has controlled impedance traces for PCIe and 1G Ethernet signals.

I looked up the 6-layer stackup specification for my board house. I used their stackup information with a trace impedance calculator to determine the trace width and spacing requirements for my routing. I ordered the PCBs, tested them, and they are working properly.

A year has gone by, and I am now looking to order a larger quantity of PCBs. I want to get quotes from multiple PCB manufacturers so I can compare cost and schedule tradeoffs. However, it appears that different PCB manufacturers all have different stackup specifications for their 6 layer PCBs.

This makes it seem like you need to commit to a board house prior to finishing routing and validating a design...and then you're locked-in to that specific board house, unless you want to change copper geometry and potentially invalidate your testing.

If the stackup is different, then won't I need to alter my trace/space requirements and redo my routing for the new geometry? It seems crazy that I'd need to design different versions of my Gerbers just to customize impedance routing for each board house I want to quote...but is this what I need to do?

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  • \$\begingroup\$ Did you ask the PCB vendor if they are able to use your Gerbers and tune the geometry for their stackup? Some PCB fabs can use any stackup you define - did you ask about this too? They might not have the materials at hand but might order them. It simply makes sense to use materials for one stackup and use it for everything. \$\endgroup\$ Commented Jun 24 at 18:04
  • \$\begingroup\$ "and then you're locked-in to that specific board house," - the cynic in me says you've answered your own question there. \$\endgroup\$ Commented Jun 24 at 18:09
  • \$\begingroup\$ I think its quite reasonable to specify the stackup/materials you want, especially if you are ordering large qtys. \$\endgroup\$ Commented Jun 24 at 18:20
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    \$\begingroup\$ Sometimes, they will update the gerbers if you tell them that a certain trace needs to be impedance controlled. But the simpler way is to just open your EDA tool and edit it. (It helps of you have different net groups/classes per impedance controlled interface type)..And you only really need to do it once for the manufacturer you are eventually going with. \$\endgroup\$ Commented Jun 24 at 20:13

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For budget PCB manufacturers you're generally locked into a few specific stackups that they offer, because they keep costs down by batching multiple customer PCBs into larger panels. Their choice of offered stackups comes down to economics, dielectric material supply chains, and customer demand.

If you pay a non-budget PCB house you can specify whatever stackup you like. Any thickness you like, any materials you like, any features you like. You just pay for the privilege.

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