@User: There are bump bonding solutions for system-in-package like www.zglue.com which are not appropriate for board level design unless you are going to design an expensive PCB and have it professionally assembled (i.e., bump pitches in the 200-300um range). We are aiming at a larger bump bond solution with a 0.5mm pitch, for which it is possible to make a surface mount landing pad on a cheap PCB (that is, no blind vias) if you stay below a certain size. Candidate solutions may change depending on what we can get done (specs vary greatly from manufacturer to manufacturer), but the preferred solution if we can get it is a 48-pin WLCSP (7x7 bump bond array with the center position missing).