PCB of the Month

Filled Microvias for 0.4 mm Pitch BGA

This tiny HDI-multilayer affords some surprises. Blind micro vias in all pads are filled with copper to maximise yield at assembly. The PCB acts as interposer with chances of a new footprint assignment at BOT layer by re-routing at both inner layers which are connected by plugged buried vias.

HDI-Multilayer
                             HDI-Multilayer

Solder mask is not necessary for this PCB for all lines are placed on the inner layers.
 
Leading a single signal between two BGA pads on inner layers requires 2 MIL lines and spaces in general. If you want to avoid such fine structures, you can fall back on excentric micro vias. So 3 MIL lines and spaces are possible, however only one line between every other row.

exzentrische Microvias
                    excentric Microvias

Don't hesitate to ask for further information contacting the ANDUS Team.