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Sniper2 , 10-03-2024, 05:14 PM

No matter what i do i cant get a nice stack up on 12 layers with 2 power layers ( unless stackup is asymmetric )
Any tips or guides?
How bad would it be to have 2 signal layers next to each other? LVDS and RMII , there would be some overlap but i can minimise that

corlas , 10-03-2024, 06:53 PM

to be honest, people are scared of using 2 signal layers next to each other, If you know what you are doing and you are careful, it will be fine. You can also make them signal/GND or signal/PWR.

You can't have the ideal stackup every time.

Sniper2 , 10-03-2024, 07:05 PM

well i never had problems but i was allwas very carefull and i mostly worked with 4-6 layers up to now

Robert Feranec , 10-07-2024, 04:40 PM

i have used two neighbor signal layers number of times, no problems. Ideally, route one horizontally and the other one vertically. Also, if possible keep bigger distance between them than is the distance to their reference planes.

Sniper2 , 10-08-2024, 03:08 PM

thx

Sniper2 , 10-09-2024, 01:46 PM

Btw

Sniper2 , 10-09-2024, 01:47 PM

Foe 12l what do you use as stackup?

Sniper2 , 10-09-2024, 01:48 PM

Rather where do you put your power layers ? Especially it it is animetric

Sniper2 , 10-09-2024, 01:49 PM

When I hot some 12l stackup from a manufacturer I got I bit worried since some controlled impedances were under .1mm is that normal in high layer count pcb?

Sniper2 , 10-09-2024, 01:49 PM

@Robert Feranec

Robert Feranec , 10-09-2024, 01:54 PM

yes, I have used some boards with 0.085mm or even 0.075mm track width for 50 ohms

Sniper2 , 10-09-2024, 07:01 PM

thx i was a bit afraid since i thought it may become a reliability problem with potencial broken traces when the PCB slightly bends

Robert Feranec , 10-10-2024, 04:31 AM

the same for me, I was also worried. but in my cases these were small size boards ... for bigger boards maybe it could be a problem, but for bigger boards this kind of stackup could be too expensive. Often these tiny tracks are used because dielectric must be very thin - usually because some microvias are used. And if microvias are used, this will be HDI PCB, means expensive board. So for normal, bigger boards usually there may not be need for that kind of stackup.

Sniper2 , 10-10-2024, 04:34 AM

Thx