for BGA's, via-in-pad (plated over) makes decoupling caps almost too easy; do a VIPPO in each BGA pad; for the power pads, you can place the cap directly on the

for BGA's, via-in-pad (plated over) makes decoupling caps almost too easy; do a VIPPO in each BGA pad; for the power pads, you can place the cap directly on the other side of the board. In many cases, the power pads are arranged next to corresponding ground pads and you can select a capacitor whose footprint exactly bridges those two vias.