US Patent 7996806 Methods and apparatus for layout of multi-layer circuit substrates

Methods and apparatus are provided for designing and laying out multi-layer circuit substrates, such as multi-layer PCBs. Dynamic vias are provided on intermediate PCB layers. Each dynamic via has features that adjust based on the trace layout of the corresponding intermediate layer. In particular, each dynamic via has a second radius R2 if the via is not connected to any trace on the corresponding intermediate layer. If a trace is connected to a dynamic via, the via radius changes from the second radius R2 to a first radius R1, where R1 is greater than R2.