Suppose I have a stackup like this:
That is, from left to right, buried vias (2-3), double side microvias, and normal through vias.
Suppose I am routing on layer 2, at a certain point I can add a “type” of via. I expect:
If I insert a MicroVia I should automatically proceed to layer 1
If I insert a Buried via, I should automatically continue on layer 3
If I insert a standard through via, Then I can continue on any layer
I cannot make KiCad enforce this behavior.
As an example if the pair 3-4 is active, from layer 2 after a microvia, I can continue on bottom layer.
The result, if I don’t catch and fix manually the error, is to make a PCB which is impossible to build.
No manufacturer chan build a PCB with that stackup and a via passing from 2 to 4. No vay.
It seems that KiCad is checking only the currently active layer pair, but in my opinion a CAD should enforce correct results, if the stackup is properly defined.
You are using the term “microvia” incorrectly. A microvia is a via with a small diameter hole.
A normal via starts and finishes on the outside layers.
A blind via starts on an outer layer and finishes on an internal layer.
A buried via starts and finishes on internal layers.
In my understanding a microvia is not only a small via.
It is also not drilled, but cut with laser.
As you can see in the picture, it is also normally visualized as conical and not cylindrical, and may span normally only the two external layers. Some manufacturers may span the three external layes, but its a complex manufacturing process (stacked vias), and not all manufacturers support it.
Additional drilled vias can be drilled only across a core. In the above picture the core spans layers 2 to 3, and then, after pressing, from 1 to 4.
There is absolutely no way to build a buried via from 2 to 4.
The only way is to stack a buried via (2-3) and a microvia (3-4), but again this is a complex manufacturing process and not all manufacturers support it.
Please ask you manufacturer if they can produce what you said.
I did, … and they say no.
That’s why I asked here.
For a four layer board, a via from 2 to 4 is a blind via, not a buried via.
This forum is for discussion regarding Kicad not PCB manufacturing.
Laying out blind and buried vias in Kicad is best achieved by placing “vias on the fly” using hotkeys.
Top and bottom layers and “place blind/buried via” are already assigned hotkeys. You need to assign hotkeys for the two internal layers.
By using the five hotkeys and the mouse, it is easy and quick to layout tracks with their correct vias.
Agree , a via 2 to 4 is blind and not buried, but blind, buried and through vias are built in the same way, by drilling. The only difference is they are made in different phases of PCB production (before or after pressing operations).
And No this is NOT a question on PCB manufacturing.
It’s a question about KiCad.
KiCad as any other CAD, even in different technological areas, have to enforce manufacturability of the design as far as it can.
It already prevents you to connect two different nets, and to violate isolation and many other “manufacturability” issues (Design rules, and constraints).
So my question is: Why you can happily design a board with zero DRC errors, nevertheless, impossible to produce?
