A dog bone is the classic fanout pattern of a pad, a short neck of trace and a via, which together look like a bone. Under a BGA, each ball pad gets a dog bone to a via placed in the gap between four pads, so signals can drop to inner layers without putting holes in the pads. It works comfortably at 0.8 mm pitch and above, gets tight at 0.65 and 0.5 mm, and at finer pitches via-in-pad usually takes over.
0.8 mm pitch fits dog bones with 0.2 mm vias, no need to pay for via-in-pad on this one.
Also heard as
- dogbone
- dog-bone fanout
Related terms
Fanout
Short connections that bring each pin of a dense part out to a via so it can be routed on other layers.
Via-in-pad
Via placed directly in a component pad, filled and plated over so solder cannot drain down it.
Breakout
Drilled hole wandering past the edge of its pad, or the routing that escapes signals from a dense part.