Eagle pro....4 layer board and via types?

[treez]

Hello,

I am doing a 4 layer board in Eagle, ...supposing i want to track down from top layer to the next layer down........do i have to use a blind via?...or can i use a through via which only electrically connects to the next layer down?

its just that i hear that through vias are cheaper than blind vias

Also, do you know how to specify 4 layers and through vias to any layer?...is it (1*2) + ( 15* 16) ?

 

[keith1200rs]

Normally I use vias which can connect to any layer - blind and buried vias increase the cost considerably and I can usually manage without them. Even having smaller vias costs less than going to blind/buried.

I cannot remember the layer definitions and cannot check until Tuesday but I think it is 1+2*15+16 but could be 1*2+15*16. I suspect either way would work.

Keith

 

[treez]

Thanks Keith,

I am not sure what prepreg is......i always thought it was just the wafer thin layer of adhesive which gets used to glue the copper to the FR4 core....

But either "*" or "+" stands for "prepreg"...i cant think why

 

[FvM]

i cant think why

Apart from "why", the Eagle 6.0 manual explains the board stackup syntax very detailed.

I see that the manual shows many examples of stacks with buried and blind vias. They shouldn't be misunderstood as design suggestions, I think.

Blind vias are drilled together with the through vias after the layer stack has been assembled. In so far they don't depend on the core and prepreg sequence. The standard 4-layer stackup uses a single core.

Blind vias are rather unusual for 4-layer PCB, but possible though. I guess, you'll want to ask your PCB manufacturer for the surcharge first.