FEDEVEL
Platform forum

Kfir2020 , 02-01-2021, 02:03 AM

hi i finish the high speed design coruse and i tring to design flex rigid board for our connector (Fischer_MR11WL08_0420_BK1_E1AP to LSH-030-01-G-D-A) ,
i have eternet pairs on my deisgn and im tring to calculate the width for 50 ohm single ended and 100 ohm diff parirs,
acoording to this stackup

the numbers dont add up,

what do you think?

Lakshmi , 02-04-2021, 08:08 PM

Better to ask the PCB Manufacturer with whom you got this stack-up.

robertferanec , 02-05-2021, 06:06 AM

I agree with @Lakshmi, if it is important I would try to ask the PCB manufacturer. But it looks like, you are using PCBWAY, so there may not be many options.

The problem is, that 2mil (50um) between copper layers is really small (it means, you would need to use very narrow tracks to get 50 OHMS) and I double checked PCBWAY website and it looks like they only have that kind of stackup:
https://www.pcbway.com/pcb_prototype...p_for_FPC.html

What do do? I am not sure .... maybe risk impedance mistmatch? I have seen many Ethernet connector breakouts connected by ribbon cables working just fine (not exact impedance matching, I found that ribbon cable impedance is like 110-130ohms diff (?)). Maybe it may work also with flex just fine ???