Altium Via Question (Buried and Blind)

[sakibnaz]

Hi there.

I have a ques on Altium Via's (Buried and Blind).

Say my Board is 4 Layer ... where I want to route a trace from Bottom layer to Signal layer 1. Now in Via Stetting will I use:

Start layer: Bottom
End Layer: Signal Layer 1

Or,

Start layer: Signal Layer 1
End Layer: Bottom

Or, both are same thing?

Similarly for Trace between Signal layer 1 and 2:

Start layer: Signal Layer 1
End Layer: Signal Layer 2

Or

Start layer: Signal Layer 2
End Layer: Signal Layer 1

Form routing point, I can see both via settings can lay the Tarce ... but just wanted to be sure if there is any fabrication issue.

Please advise.

Thanks in advance.

Regards.

 

[FvM]

Are you sure that you want to pay the surcharge for buried and blind vias? Using it on a 4-layer board isn't impossible but very unusual.

You'll usually utilize other options to increase wiring density first. Even switching to a 6-layer standard process may be a cheaper alternative.

 

[sakibnaz]

Hi.

I understand. Actually my PCB don't have wire density. But there is two BGA Type Module, one is at Top and other Bottom Layer. Hence I am not able to place normal Via's as its conflicting with opposite side Module Pads. So I am thinking to to Buried and Blind Via's.

Thanks.

Regards.

 

[FvM]

I see. In this case blind vias may be required.

How ever the blind and burried vias are entered in a PCB tool, you'll end up with separate drill files for each via type, one for regular through-vias, one for blind vias to to inner 1, one for blind vias bottom to inner2, one for burried vias inner1 to inner2.

Not all layers ranges can implemented in a specific stack-up, in case of doubt contact the manufacturer before finishing the layout.

 

[ArticCynda]

Buried vias and blind vias under a component (like a BGA) should be avoided whenever possible, they're expensive to manufacture and more likely to cause connectivity problems. Also, you'll have to add dedicated test points elsewhere on the board because you can't probe the vias anymore, so they aren't saving you a lot of space either.