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Platform forum

noisepic , 09-17-2018, 09:37 PM

I plan the stack up for 10 layers, there's sandwich layer:
Gnd-2
Inner3
Inner4
Vdd-5

In which inner3 and 4 are high speed line. And it should be not overlap each other ? A stupid question but a little bit hard when do layout.

Paul van Avesaath , 09-18-2018, 05:23 AM

basically there are two ways of doing this, but it al depends on your design.
rule one keep the board semetrical, meaning for a ten layer board you would do either

top, internal plane1, midlayer 1, midlayer2, interalplane 2, internal plane 3, mid layer 3, mid layer4, internal plane 4, Bottom

or

Top, mid1, int1, mid 2, int2, int3, mid 3, int4, mid4, bottom,

preferably you would go to 12 layer by adding a internal between top and mid1 and bottom and mid 4.

robertferanec , 09-19-2018, 12:24 PM

I prefer to place high speed signals on the layer closer to GND solid plane - GND is usually good reference plane (some powers are not good reference planes and often they are not solid). Also I make the isolation between GND and signal layer as small as possible e.g. often between 75-120um, but depends on stackup)