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Layer stack-up details

meet , 12-30-2016, 04:17 AM
Hello Robert,
As shown in attachment, there is no via from L1 to L4 and similarly L12 to L9. As I understand, L3, L4, L9, L10 layers are used for routing. then, how Layer L4 will be used?
will it accessible with through hole via only?
can you please, elaborate about layer details regarding layout planing. for example, L3 can be used for data lines while or L10 can be used for Address command and controls.

I wish to know which signals you had considered for layer 4, because it accessible with through hole via and if we use it for high speed signal, there may be stub.

I also would like to know why 4 internal layers are used for power planes (+ive supply)

All together, i am curious to know how to plan signals for layers.

I wish you, a very happy new year!!!!!
robertferanec , 12-30-2016, 05:11 PM
@meet, this may help you: http://www.fedevel.com/welldoneblog/...of-pcb-layers/

If you are speaking about iMX6 Rex module stackup, have a look also at the completed project. You will see how the tracks are routed and how the layers are used. Here you can download the full project: http://www.imx6rex.com/

- in many 12 layer stackups we use L2/L4 and L9/L11 as reference planes (as solid GND planes) and we route most high speed signals on L3 / L10. We use L5/L6/L7/L8 as power planes.
- You do not need VIA from L1 to L4, you can use the through hole via (L1-L12) or you can use the buried VIA (L3-L10). Both this VIAs will connect to L4
- Processor boards have usually number of different power planes and it may require up to 4 layers to be able to design a good power distribution / power planes. Two layers for power planes on a CPU board is usually not enough. Dont forget, under CPU there may be high currents flowing and you need wide power planes with enough copper.

I hope this helps.

meet , 01-03-2017, 01:49 AM
Hello Robert,
Thank you for detailed reply. i got the answer of my curiosity Its large current which Leeds to increase number of planes.
robertferanec , 01-04-2017, 06:25 PM
It doesnt have to be large current - for example I prefer to use mutliple GND planes to create a good reference planes above and below critical or high speed tracks.
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