Author Topic: PCB Stackup with FR4 and Rogers?  (Read 496 times)

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Offline eescuve

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PCB Stackup with FR4 and Rogers?
« on: September 09, 2022, 01:32:10 pm »
Hello! I'm designing the stackup of a 4 layer RF Board. I have it functional with a full Rogers 4003C stackup. Since I only need one layer of Rogers material I was wondering if I could use only one layer of Rogers and the other 3 of FR4 to reduce cost. Will I have PCB warping problems? Do I have to take any other considerations?

Offline exmadscientist

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Re: PCB Stackup with FR4 and Rogers?
« Reply #1 on: September 15, 2022, 06:24:29 pm »
You should avoid an unsymmetric stack up at all costs. So that's 2 and 2 rather than 1 and 3.

Some Rogers materials are designed to do this. You may find it useful to select a different Rogers laminate if yours is not one of them. Extra cost here for the material may or may not pay for itself in savings elsewhere.

Apart from that... this is another case of "talk to your fabricator". Anyone with experience building with Rogers laminates has probably heard this question before and knows how and when to do it. Unless it's a proof of concept build at a low-cost overseas vendor, in which case you might as well just spend the extra money for the fancy laminate because you're not going to get an overall lower cost elsewhere, once you consider the time needed to communicate what you want and the low quantities of PoC builds.

Online Gerhard_dk4xp

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Re: PCB Stackup with FR4 and Rogers?
« Reply #2 on: September 15, 2022, 10:01:51 pm »
I had some boards made, 1 layer Rogers TMM6, 0.5mm, the rest in FR4. 
No problems with warping, but they managed to put the 10 GHz stripline
filters on the FR4 side and the DC distribution on the Rogers, in
spite of clear instructions.    |O  The second run was OK.

The eval boards for the SKY 67150 MMIC are also Rogers 4350?
(the fireproof version of 4003) for one layer and the rest in FR-4.
That seems to be normal practice.

Cheers, Gerhard


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