Electrical properties of a multilayer thin film substrate for multichip packages

The authors report the electrical properties of multilayer thin-film interconnects examined under circumstances in which the signal lines were sandwiched between mesh-pattern metal layers (called meshed striplines). Multilayer thin-film substrates with various transmission line structures were manufactured with several mesh patterns (power/ground planes) and signal lines, and the characteristic impedance and crosstalk for these lines were measured. The relations between the electrical properties and the meshed-stripline structures were obtained from the measurements for use in designing multilayer thin-film interconnects. It is shown that, in meshed-stripline structures, the characteristic impedance can be controlled by changing the aperture ratio or the mesh pitch. The fluctuation in the characteristic impedance along the signal-propagation direction was insignificant. It was also found that the crosstalk noise in meshed-stripline structures can be made as low as those in ordinary stripline structures.