Are Buried or Blind Vias necessary in a multilayer PCB ?

[3Deye]

Hello,

As the title implies, are Buried or blind vias a must in a 8-10 Layer PCB or can I avoid them in the design ?

 

[keith1200rs]

They aren't compulsory! I have never used them, but with high density boards I assume they make the layout 'easier' (or possible!).

Keith

 

[3Deye]

Hello Mr. Keith , long time no see

Thanks, I will try to avoid using them since they increase the manufacturing cost a lot (increase about $400 for a 10-layer PCB !).

 

[keith1200rs]

I've been here - just a bit busy so not as active.

The company I normally use doesn't do blind vias and I normally do mixed signal boards up to 6 layers so blind vias aren't a problem. Sometimes though I wish I could use them even on 4 layers because you run out of PCB surface to put the vias in without hitting something. I suspect that is what will force you to have to use them when you get to 8 layers or more.

I often reach a point where I am not sure which way to go with a layout so I save a copy and go down one route e.g. add another couple of layers and then can go back and try another solution and pick the one which seems to be going best.

Keith.

 

[PCBWING]

PCB including the blind hole or buried hole drilling needs of many times, it demands a higher precision, manufacturing time-consuming, so it is more expensive than no including them.

 

[911EDA]

Blind and buried vias are sometimes needed to get out of a large BGA or in a complex board, but our designers generally try to stay away from them. Both are going to add additional cost to manufacturing boards - blind more than buried. We have also found that yield can decrease when using blind and buried vias due to the increased overall difficulty in the manufacturing process.

We would only recommend using blind and/or buried vias when there are no other options or if you don't care about the cost of manufacturing.

Ryan O'Connor
911EDA, Inc.
www.911pcb.com

 

[3Deye]

Thanks Mr. Keith and PCBWING for the advice, till now I didn't use Buried/Blind vias and I'll try to avoid them as much as possible.

The problem is that the extra cost depends on whether they're used or not , and doesn't depend on their number, so If I used say 1 buried via, I'll have to pay the extra $400 which is the same price if I used tens of them !!

 

[arunrajendhar]

I accept with keith..

The buried and blind vias requires when we use a .4 or .5mm devices to meet the aspect ratio.

For 8 or 10 layer brd there is no need for muliti or sequential lamination.

Also it depends on the minimum drill size of the board with respect to the board thickness (Aspect ratio)

thx..