Three-wire-line vertical interconnect structure for multilevel substrates

Abstract

A vertical interconnect structure comprising a three-wire-line transmission line structure for providing electrical continuity between different levels of a multilevel substrate. The present invention provides a means for transferring power between various levels of the substrate without introducing excessive additional RE losses. First and second coplanar transmission line structures are disposed on first and second surfaces of the substrate. A vertical interconnect structure is disposed in the multilevel RF substrate and is coupled between the first and second transmission line structures. The vertical interconnect structure comprises three conductors having predetermined cross-sectional dimensions and predetermined separations therebetween that are adapted to transfer RE power between the first and second transmission line structures. In a completed electronic circuit employing the present invention, an electronic device is electrically coupled between two coplanar transmission line structures disposed on one surface of the substrate, and the vertical interconnect structure couples power to the electronic circuit by way of the coplanar transmission line structure disposed another surface of the substrate. The impedance of the vertical interconnect structure is determined by the relative dimensions of the three conductors and their relative separations. The three-wire-line transmission line structure supports a highly desirable TEM mode of energy propagation. The present invention is relatively easy to fabricate, in that vertical wires having a circular geometry are easily accommodated as part of the fabrication process for the substrate. The present invention provides for relatively low loss, because of the nature of the currents that flow on the conductors. The propagation characteristics are well-understood, and the vertical interconnect structure supports a highly desirable TEM mode of energy propagation.