OK to tent unused BGA pads?

I am trying to avoid using trace/gap sizes below 4 mils. However, I cannot route traces from the inner rings of my BGA between pads without doing so. One option for me is to route the necessary inner ring signals right through some outer ring pads that are not used in my design. But I don't want those pads through which I am routing to make an electrical connection to the balls on the BGA.

Would it be acceptable to completely tent with soldermask the pads for the balls I am routing through so there is no electrical connection to the BGA ball? I would, of course, remove the stencil aperture as well, so no additional paste is deposited on those pads which are tented.

If I do this, there would still be a ball on the BGA on those unused pins which would reflow in the oven, but there would be no metalization on the board to which it would connect. I presume it would just remain a ball.

One potential problem I foresee is that the tented pad might prevent the BGA from sitting down properly on the other pads that are not tented. I would only need to do this on one or two out of 113 pads.

Do you see a problem with this technique?

Thanks,

Randy

I don't have experience with this, but, if you're going to try this, I'd recommend removing the unused balls before soldering.

I'd recommend using more layers for your board if you are using a BGA.

Fan out vias on the used BGA pads and route on another layer, only use the top side for the outside pads.