How to create a via from layer 1 to 3 on a 8 layer PCB?

[fhn]

I'm working on a design for a 8 layer PCB with Multisim/Ultiboard v10. In Multisim under sheet properties i selected the PCB to contain 8 layers, which makes Ultiboard to create this board with 4 layer pairs and 0 top/bottom build-ups. In the PCB properties of Ultiboard i enabled micro vias and buried/blind vias but i noticed that i'm not able to allow vias between some combinations of layers.

For example i can enable vias from top to the second layer (1st inner) and from top to the fourth layer (3rd inner), but not from top to the third layer (2nd inner).

When placing a via, i can select top for the start and the 3rd layer for the end, but it will be created as via between top and the 4th layer, which will -of course- shorten several traces on the 4th layer.

So my questions is: Why am i not allowed to create a via, that goes from the top layer to the third layer and how to enable all possible combinations of start and ending layers for the via?

Thanks for your help

fhn

PS: sorry for my bad english 😕 

Message Edited by fhn on 08-22-2008 04:39 AM

[lacy]

I am not 100% sure about this, but what I see happening here is that you can only select certain combinations of pairs. Once that selection is made it will gey out other selections as not valid. You might want to carefully look at the options in the via selection and make sure of which layers you want vias to be on. I don't know about enabling all layers in this selection. I would assume this would not be legal from a design rules standpoint, but since most of my boards are either single or double sided I do not have the necessary experience with multi-layers to give a proper answer to that.

This is the only thing I can advise as when I went through the process I was able tio select the vias for the layers you outlined in your post.

I hope this helps somewhat as this is all can tell you.

[Johann.Wagner]

Yes it´s correct that when you manufactures a multi layer you can´t create each via´s you want - therefore we have a help. You see the greyed fields in the board wizard in my *.doc which shows you the possible and not possible via´s you can do or better the manufacturer of your layer can later do...

When you set a possible via then other possibilities going gray - so not valid.

Best Regards

Johann

[fhn]

Thank you for your support.

So according to your answers the root cause of my problem is that my pcb manufacturer can build more via combinations in one pcb than ultiboard thinks he can. (Or at least my manufacturer claims he is able to... 😉 )

Is there any way to work arround this kind of assistance of ultiboard?

Also i found no way to crate a via from top to bottom which only has an annular ring on - lets say - layer 1, 3, 6 and 8. Am i missing something?

Thank you in advance

Florian 

[Johann.Wagner]

you can try placing a wire on active layer e.g. layer 1, then changing active layer to layer 3 and continue wiring - so it´s create automatically a via between layer 1 and 3 - so you can do it with other via´s

So manual wiring should work but not automatically routing...