Substrate material clarification for 4 layer PCBs

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1

Hello,
I’m building a test board for a USB hub chip and noticed a discrepancy in the documentation provided in the DKRed specifications page. The substrate datasheet .pdf is for Isola 185HR for 2 and 4 layers builds, however, the 4 layer stackup document shows prepeg and core layers of ISOLA 370HR.
Both materials have slightly different dielectric constant (Dk) and the one listed in the 4 layer stackup doesn’t match any of those materials. The calculation of differential pairs will change accordingly.
Please clarify which material is used and ultimately, which of the three DK values (185HR → 4.13, 370HR → 4.24, Stackup → 3.99) should be used.

Thanks!

2

It’s going to be 370HR, like the below link:

Follow the DKRed 4 Layer Stackup specification here.

3

Hi Kristof,
Do you know why the prepeg there 370HR - 2x2113_59% specifies a 3.99 Dk while the manufacturer specifies higher values, all the way up to 2GHz here ? see 2x2113 line.

4

The above linked document Layer Stackup specifications are what was provided by the DKRed Printed Circuit Board fabricator.