# Eagle and vias - board layout

I will start out by saying that I'm an electronics hobbyist and I'm currently in the process of laying out my first 4 layer board in eagle. Now all of the PCB manufacturers I've looked at either don't support or charge a lot for blind vias.

In eagle I get several options for vias as show in this image.

Now do I just want to select 1-16 and rout on the required layers keeping other traces away, or do I select 1-2 for routing from layer 1-2, keeping in mind that I can't have blind vias.

Though @Samuel has already written what you need, here is a little more about the (EAGLE) internals.

PCBs are usually made of a resin reinforced by glass fibers. To make multi-layer PCBs, usually several thin double-layered PCBs (cores) are made and glued together by a so called prepeg. After this, the vias are drilled and the walls of the holes are coated by metal to make the vias conductive.

However, it's possible to add vias already to the cores and so to make vias between distinct layers. But this adds extra work / costs.

EAGLE allows to configure between which copper layers vias can be made in the LAYERS tab of the design rule window:

Here, two cores (green) are glued together by a prepeg (grey), and vias are possible through each core as well as the whole PCB. This is defined by the string ((1*2)+(15*16)) in the setup.

You can change it to (1*2*15*16) which also defines a four-layer PCB, but only with vias across the whole board.

Finally, you can of course your set up and use "1-16" vias only, and this is more for completeness.

You need to via from 1-16

The other options only place vias from layer 1 to layer 2 or from layer 16 to layer 15, that is, they create blind vias.

The other option, which is not listed but you still don't want is the buried via, which would be from layer 2 to layer 15 (the two, or more, internal layers).

• Adding to this, if you want to continue routing on the internal layer, you need to select the layer after placing the TH via and route as usual. – crasic Dec 15 '15 at 19:06