Inductive filters and methods of fabrication therefor

Abstract

A series of plated through hole (PTH) vias are interconnected by traces that alternate between a top surface and a bottom surface of a dielectric board. The PTH vias in the series can be positioned to create a collinear inductive filter, a coil-type inductive filter, or a transformer. Multiple, electrically isolated series of interconnected PTH vias can be used as a multi-phase inductive filter in one embodiment. In another embodiment, multiple series of interconnected PTH vias are electrically connected by a linking portion of conductive material, resulting in a low-resistance inductive filter. Ferromagnetic material patterns can be embedded in the dielectric board to enhance the inductive characteristics of the interconnected via structures. In one embodiment, a closed-end pattern is provided with two series of interconnected vias coiling around the pattern, resulting in an embedded transformer structure. A method of producing an interconnected series of PTH vias includes providing a dielectric board having a series of holes. In some embodiments, the board includes an embedded ferromagnetic material pattern. The holes and the top and bottom surface of the dielectric board have a conductive material thereupon. Portions of the conductive material are selectively removed, resulting in the embedded inductive filter and/or transformer structure.