Abstract: A backplane motherboard which mounts a plurality of printed circuit boards and which provides microstrip transmission lines to interconnect the components of an inserted PC board with any of the other inserted PC boards. All transmission lines are terminated at both ends with the characteristic impedance, and the plane of the motherboard is made of a sandwich construction having a ground plane, a Mylar insulating plane, a voltage plane, and outer epoxy surface insulators. The plane sandwich also carries terminal pins for holding additional printed circuit boards.