A sintered ceramic article which comprises internal electrodes and/or conductors is formed by producing a sintered ceramic body that has areas of ceramic with interconnected pores extending to an outer face thereof and providing a conductor in said porous areas. The ceramic body may be formed by depositing, as by screen printing, on sheets of a powdered dielectric or insulating ceramic material bonded with a temporary bond, an area of a temporarily bonded powdered ceramic material which on firing becomes porous, consolidating a plurality of such sheets, and sintering them. Subsequently a conductive material may be provided in the porous areas by impregnating said areas with a conductive material or with a material which is reacted or decomposed to form a conductive material in said areas.
A method for constructing a capacitor having an increased equivalent series resistance (ESR) is disclosed. In one embodiment, a capacitor includes a plurality of capacitor plates comprised of a conductive material and first and second capacitor terminals. At least one of the capacitor plates is coupled to the first terminal and at least one of the capacitor plates is coupled to the second terminal. At least one of the plurality of capacitor plates includes a pattern, wherein the pattern is void of conductive material. The void in the conductive material formed by the pattern may cause a path of current flow through the capacitor plate to be substantially altered in comparison to a capacitor plate that is continuous. By using capacitor plates having voids of conductive material that cause the current path to be altered in comparison to continuous capacitor plates, a capacitor can be constructed having a higher ESR.
A sintered ceramic article which comprises internal electrodes and/or conductors is formed by producing a sintered ceramic body that has areas of ceramic material extending to an outer face thereof, said areas having an open structure characterized by interconnected voids, and thereafter providing a conductor in said porous areas. The ceramic body may be formed by depositing, for example by screen printing, on sheets of a powdered dielectric or insulating ceramic material bonded with a temporary bond, an area of a temporarily bonded powdered ceramic material which on firing becomes porous, i.e. open-structured, consolidating a plurality of such sheets, and sintering them. Subsequently, electrodes or conductors may be provided in the open-structured areas by impregnating said areas with a metal or alloy and providing a termination electrode on the said outer face. If desired, an open-structured permeable barrier can be provided on said outer face before such impregnation. The barrier may be either a porous ceramic or a porous conductive coating which serves as a termination electrode.
Monolithic ceramic capacitors are formed by producing suitered ceramic bodies with voids. The voids are produced during sintering. In the voids are distinct pillars which remain after sintering. The voids are filled with metal to form conductive electrodes.
A method for manufacturing ceramic capacitors of the lead filled type comprises coating the end surfaces of a ceramic monolith having internal voids opening to the ends with a termination paste. The paste includes glass frit, a metal component wettable by lead, i.e. silver, binder and solvent, the characterizing feature of the paste being the inclusion of reducible metal salts of a metal wettable by lead, the salts undergoing volumetric diminution when reduced from the salt to the metallic state. When the termination paste is sintered, reduction of the metallic salt provides the termination with a porous latticework. Molten lead or lead alloys are injected through the now porous, sintered termination paste. The disclosure further relates to a capacitor made in accordance with the method described.
A monolithic ceramic capacitor having embedded electrodes formed by cosintering of ceramic dielectric layers and layers indifferent to the dielectric layers corresponding in area and position to the electrodes. The indifferent layers are converted to a conductive state, for example, by chemical conversion and used as such or are removed and replaced by metal or conductive material. One example in which the indifferent layers comprise nickel oxide involves stacking layers of green ceramic coated with nickel oxide in the desired electrode pattern, sintering the stacked layers to produce a monolith, reducing the nickel oxide in the monolith to metallic nickel in a hydrogen atmosphere at a temperature low enough to have minimal effect upon the dielectric properties of the ceramic and using the metallic nickel as reduced for the ceramic capacitor electrodes. In another example, after the reduction step (which may be at high temperature) the metallic nickel is dissolved, for example by sulfuric acid, the ceramic monolith is reoxidized by firing in an oxidizing atmosphere such as air, and the voids left by removal of the dissolved metallic nickel are provided with suitable electrodes. In still another example, in which the indifferent layers comprise oxidizable material such as carbon, the stacked layers are sintered in an inert atmosphere to produce a monolith of matured ceramic and the indifferent layers are removed by subsequent firing in an oxidizing atmosphere to produce the voids for receiving conductive electrode material.