Plated-Through-Hole Via Design Specifications for 112G Serial Links

An earlier study of a high layer-count test board using plated-through-hole (PTH) vias and a limited quantity of laser vias was shown to be capable of supporting 112 Gb/s PAM-4 links (or equivalent signaling having 28 GHz (Nyquist) bandwidth). This original board design was then rebuilt using a different fabricator, and the test results revealed a significant decrease in the bandwidth of the vias. These results led to the development of a set of design specifications that PCB vendors can easily validate, which will ensure that the use of high layer-count boards with PTH technology are viable for emerging 112 Gb/s PAM-4 links.