A High-speed Vertical Transition for Multi-layer A1N Carrier Boards Designed by Time-domain Reflectometry

High density, high speed photonic integrated circuits (PICs) have large numbers of closely spaced DC and RF contacts, which must be connected in the package. The use of multilayer carrier boards to interface between the contacts and the package gives high performance and high density. In order to be effective as a packaging solution, these multi-layer carrier boards need high-speed electrical channels with good performance. Also, the boards usually need high thermal conductivity to manage the heat. Co-fired aluminium nitride (A1N) has the needed high thermal conductivity. However, there are no designs of multi-layer high-speed channels in the literature for co-fired A1N. Therefore, this article presents a high-speed multi-layer channel for co-fired A1N and its measured results. Two transmission lines were designed that showed a measured loss of ≈ 0.09dBmm^-1 at 40GHz. The vertical transition allows for arbitrary planar rotations of the channel and showed a measured 3 dB bandwidth of 33 GHz and small penalties in the eye diagram with a 44 Gbits^-1 signal. The channels showed crosstalk below -30 dB.