14 Vias and VIP

One of the greatest benefits from package-on-package technology is the elimination of the complex, expensive, and challenging task of routing high-speed memory lines from under the processor out to memory. Instead, the memory sits on top of the processor and the connections are automatically made during assembly.

Except for the outer perimeter balls, routing for the BeagleBoard is done with VIP technology. Although this was once a feared and expensive technology, recent studies and advances have eliminated nearly all of the problems. In fact, VIP is becoming the dominant technology for high density boards and is providing a cost effective alternative to conventional and offset vias.

The VIP methodology places the via directly under the device’s balls. However, this requires another step to seal the via to prevent blowouts and voids. For the BeagleBoard, non-conductive, epoxy-filled vias were used.

The BeagleBoard uses only through-hole vias from top to bottom, blind vias from top to layer 2, and stacked vias from top layer to layer 3. It does not use buried vias. All vias are laser drilled.