Shielded bar-cap

Abstract

Interelectrode parasitic capacitance coupling between the top plates of a bar-cap is avoided by a shielding electrode layer on the top surface of the bar-cap's ceramic substrate adjacent to, but spaced apart from, each of the top plates. The shielding layer has a plurality of windows through which respective surface regions of the top surface of the bar-cap are exposed. Within the windows respective ones of the top plates of the capacitors of the bar-cap are provided, each plate being spaced apart from the shielding layer. The shielding layer is coupled to a source of reference potential (ground) so as to provide an electrical shield around each of the top plates of the capacitors and thereby effectively prevent parasitic capacitive coupling through the ceramics substrate between adjacent ones of the top plates. Grounding of the shielding layer may be accomplished by a direct wire connection to the shielding layer or by forming a conductive layer along a sidewall of the ceramic substrate to integrally electrically join the shielding layer to a bottom conductor. In a second embodiment of the invention, isolation between adjacent decoupling capacitors of the bar-cap is effected by forming respective grooves or channels between surface regions of the substrate in which the capacitor top plates are formed, thereby interrupting the continuity of the surface of the ceramic substrate and preventing the establishment of a parasitic capacitance between neighboring plates of the bar-cap.