Greetings,
For two different reasons, I’ve come to wanting something that, I think, may not be obviously available. We’d like to be able to specify the structure of a via more precisely, especially when it traverses a specific set of layers.
This comes up in two ways. We’ like to categorize vias by the top and bottom layer. This could mean that there is one or more types of vias between those layers. In some cases, we want PTH type and in others we may need a laser drilled via on the same board. But often, we want to prefer a type of via based on the layers, so it is likely that all top-to-bottom vias are PHT, for example. The current methods for via selection can (I think) do this, though I admit I often need to edit them by hand after placement because I’m not always able to make my intention clear.
The second way we want to customize vias is more complex. Our vendor wants to use different means of perforating the PCB layers. Some can be laser drilled and others may need a mechanical drill. The laser drills are 0.1mm, but the smallest mechanical drill is 0.2mm which leads to a via where some layers use a different technology–think successive lamination.
Note that part of what makes this tricky is that we don’t have room to make these vias 0.2mm drilled all of the way through as there are some very tightly routed sections.
- Is this currently possible with the UI? (I don’t think so, but it would be handy if it were.)
- Is this possible with some scripting?
- Am I missing some kind of simple solution?
Cheers
KiCad does have support for both blind and buried and for micro via’s, but you have to enable this in the board setup first.
Copy from the PCB Editor manual:
If microvias or blind/buried vias are enabled in the Constraints section of the Board Setup dialog, these vias can be placed while routing. Use the hotkey Ctrl+V to place a microvia and Alt+Shift+V to place a blind/buried via. Microvias may only be placed such that they connect one of the outer copper layers to an adjacent layer. Blind/buried vias may be placed on any layer.
I have been looking through the board setup in KiCad V8 but can’t locate the exact location of this setting. “Laser Drilling” is usually “micro via’s”. and this normally only goes through one layer of prepreg, not from layer 1 to layer 3. This is a limitation of PCB manufacturers, not of KiCad.
What is your complete layer count? Do L2 and L5 also exist? Is there an F.Cu and B.Cu in addition to the numbered layers? When communicating though this forum, it avoids misunderstandings if you use the default layer names, or at least show the part of the Appearance Manager with the copper layers.
Also, the most common way of making PCB’s is to start with the core and two copper layers, then laminate on prepreg on both sides to get a 4 layer, and then repeat that to get to 6 layers. But there are alternative ways to combine all the layers together. And these advanced sorts of layer stackups also define which sort of via combinations can be manufactured.
I have enabled microvias as well as blind/buried ones. It’s just that the hotkeys don’t lead to expected results. I’ve followed the tutorials and played with it. I suspect I’m just not understanding some subtlety. Usually, I’m drawing a trace and I want to jump to another specific layer. Seldom does it do what I expect. Editing the via fixes it up well enough.
FWIW, the distinction between microvia and blind-buried seems superfluous. We’re going to be routing from one layer to another and we don’t care, with laser drill, about micro or blind/buried except for whether or not the fab can execute the design. Just my 2c.
The layer stackup note I show came from the PCB vendor. This is a 6 layer board. I don’t think that detail matters for the question. I included the note because this is a specific request from the PCB vendor. They like numbering layers, so they’ve labeled them L1-L6.
I don’t see how to do anything other than specify a single hole size for the whole via. And as you point out, this isn’t generally how vias are created in many cases. Certainly, the vendor can drill and plate with successive lamination, but with laser drilling, it’s possible to have a different effective diameters per layer.
