FIG. 4 illustrates a top view of the cover 150 installed on the via fence 140 with a portion removed to see into some of the chambers 142A and 142C. For illustrative purposes, the cover 150 is shown as a rectangular shape planar substrate affixed to the top of the via fence 140. Thus, portions of the cover 150 overhang the perimeter of the via fence 140. The shape of the cover 150, however, may extend to the perimeter with essentially no overhang. The process of attaching the cover 150 to the via fence 140 may be by solder or epoxy. In some embodiments, the cover 150 may be fastened to the via fence 140 using fasteners 155 that are affixed to the via fence 140 by holes 145. However, the fasteners 155 are optional and may be omitted if the holes 145 are omitted. In some embodiments, the shape of the cover 150 may track the perimeter edges of the wall structure 144.

The front-end RF stage 104′″ may include a via fence 140 created outside of the PWB together with an affixed cover 150 to form an isolation structure including external three-dimensional (3D) isolation chambers for a pre-designed circuit pattern with signal trace lines. The via fence 140 may include a first material 512 (FIG. 5) that may be a dielectric, which may be a poor conductor of electricity. The dielectric is generally encapsulated with a second material 514 (FIG. 5) that may be a good conductive material, such as Au, Palladium (Pd), Ag, Al or Cu. The term “material” as used in this disclosure may include a single material or a composite of materials.