Odd-layer-count boards are not only manufacturable, but at times preferable.

Can vias carry considerably more current than was previously known? 

When the authors were investigating via temperatures, we were surprised to find vias were much more robust than we had thought. They could carry considerably more current than anyone had previously imagined. The reason is the trace provides a very effective heat sink for the via, permitting a substantial amount of heat to be conducted away from the via itself. The rule we proposed is that if the trace itself is sized correctly, only a single, small via is required, regardless of the amount of the current. Subsequent experimental results confirmed our initial modeling. We reported these results in two previous articles (note 1) and in a subsequent book (note 2). This article looks at the current carrying capacity of vias (and a related trace configuration) in more detail.

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