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Blind via limitations?

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cingkrab

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I've built a board with 6 layers with blind vias, and the stackup is like this:


Top routing/components
Ground
Power1
Power2
Power3
Bottom routing/components

The blind vias run from: top-ground (1-2), top-power1(1-3), top-power2(1-4), top-power3 (1-5), bottom-ground (6-2), bottom-power1(6-3), bottom-power2(6-4).

Problem is, no one seems to be able to fabricate this board. What are the upper limits for the number/types of blind vias for a 6 layer board? Also, would backdrilling be a better (more manufacturable) option?
 

your board shop should give you the stackup they can build.


you can go from top-ground and then ground-power 1
also same from the bottom go from bottom-power3 and then power3-power2
the core is from power1-power2 which you can use a blind vias

forgot to mention : some can drill from 1-3 as well

do you really need blind and buries vias. it is a very expensive process.

hope it makes sense.
 
Last edited:

Mainly I am using these vias for decoupling capacitors. Are blind/buried or backdrilled vias necessary for decoupling? I've read from TI that they help at high speeds due to the lower inductance.

focus.ti.com/lit/an/sloa069/sloa069.pdf
 
That is probably true. At what frequency are you running the circuits?? If you are in KHz or MHz range I don't think you need microvias.
The TI paper is for the G Hz range.
 

loosemoose said:
That is probably true. At what frequency are you running the circuits?? If you are in KHz or MHz range I don't think you need microvias.
The TI paper is for the G Hz range.
Click to expand...

The circuit will operate between 5-10 GHz.
 

Were you able to get some information from the board house??
Is it possible to make the pcb thinner?? Maybe .031" thick instead of .062"?

If you have access to hyperlinx you could model it.
 

This appears to be a case of an engineer designing a board stackup without finding out if it can be manufactured first.

You should always find out what layers blind and buried vias can go between before attempting to use them.
 

The board has to be made as a series of boards, these are stacked and drilled at each stage. You require a thorough understanding of how the board can be assembled before you define the layer spans of the blind and burried vias. The design you have cannot be fabricated, though could be achieved by backdrilling.
Have fun
 

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