How to connect two sides of a spacer PCB?

[Anonymous]

Hello everybody, I am currently designing a "spacer" PCB. What I mean by a spacer is: A two layer board with two equal BGA footprints at each side (one mirrored) which are simply connected to each other. The "spacing"-effect is simply based on the physical material used. I created the footprints and now I am wondering, how it is possible to route the connections properly. As the BGA-Ball-Pairs which have to be connected are at the exactly same (x,y) position, first of all I was thinking about using microvias, but after some reading I saw that microvias by definition do not go through the whole board, even it's a two layer board because of dimension etc., am I right? So, is there some technique I can use to connect both exactly overlayed footprints easily? I am thinking about PTHs which top and bottom is closed/covered by some copper to solder a BGA on it. 🙂 If there are multiple possibilities, of course cheapest for win! 🙂 If this is a really simple problem, please excuse my asking. I am an absolute beginner into PCB design, tried to do some research but did not succeed so far. Anyway, thank you in advance. All the best, Marvin

[mtl_asm]

Why not just use regular vias? Microvia is as you said just referss to  a via that does not go through all the layers of the board, but since your spacer swill likely only be 2 layers (top and bottom) just use a regular via beside each bga pad that goes from top to bottom layer. 

So in this case a via is basically what you suggested, just plated through hole, although usually they are also covered with the solder mask so the copper is not exposed. If you start a 2 layer board in eagle and just use the via command, teh default pad stack will put it all the way through the board and it should work as you wanted (:

hope this helps.

[Anonymous]

Hi,

first of all thanks for trying to help, even though I'm kind of a noob.

Second, I'm sorry for the REALLY late response (must be several months now?). I was busy with other projects and this one simply had less priority.

OK, so anyway, I finally found some time to look at this again and recognized, that the problem seems to be the dimension of the annular ring of a via (at least I think this is the annular ring).  I took two pictures, that should immediately explain the troubles I'm currently having:

Without vias (unrouted)With vias (some routed)

The pitch is with 0.5mm kind of small.

Further, the free space between two balls of the grid is rather small, too, as a single balls diameter is 0.325mm.

As a manufacturer I decided to use OSHPark, because they are acting in non-professional segment but should be able to produce this kind of small designs. At least as far as I know.. In addition, it was kind of easy to use their DRC files. 🙂

When selecting to place a via do I have to explicitly switch to PTH somehow?

Do these DRC errors mean, that my manufacturer won't be able to produce this board at all? Are there any workarounds you may think of?

Which possibility would be the most eligible to connect both the sides if there should be no way to use vias directly?

All the best && stay healthy,

Marvin