Itt Industries, Inc.

International Standard Electric Corporation

Stc, Inc

Standard Telephones & Cables Limited

John H Alexander

Henley F Sterling

Eric L Bush

Dawn A Jackson

A dielectric composition including a ternary system comprising non-stoichiometric lead magnesium niobate, non-stoichiometric lead zinc niobate and non-stoichiometric lead iron niobate, and a small amount of one or more oxide additives which serves to reduce the tan .delta. value in comparison with the ternary system alone. The one or more additives may be chosen from the group consisting of nickel oxide, stoichiometric lead nickel niobate, ceric oxide, lead oxide, zirconium oxide, silver oxide, manganese dioxide, lanthanum oxide and cobalt oxide. Compositions with firing temperatures in the range 950.degree. to 1100.degree. C. have dielectric constants in the range 10700 to 16600 (at 20.degree. C.) making the composition particularly useful for high silver content multilayer ceramic capacitors.

Dielectric composition

Ceramic capacitors are formed from electrodeposited ceramic dielectric layers that are provided with electrodes, stacked and fired. Contact to the electrodes is provided by each terminations and leads. As the electrodeposition process is self limiting and self heating, uniform pinhole free dielectric layers are obtained.

Capacitors

A dielectric composition, for use in the manufacture of ceramic capacitors, and comprised of barium titanate (BaTiO.sub.3) with small additions of niobium pentoxide (Nb.sub.2 O.sub.5) and gadolinium sesquioxide (Gd.sub.2 O.sub.3).

Ceramic capacitor and dielectric compositions

A method of manufacturing thin film dielectric material by directing vapors of reactants containing lead and additional metals and an oxidizing gas onto a heated substrate to form a layer of dielectric material thereon, which layer can be of a high dielectric constant (greater than 5000).

Dielectric materials

Ceramic capacitors are made by printing green ceramic limps with a fugitive electrode material, stacking the printed limps and firing the stacked assembly to form the ceramic and remove the fugitive electrodes. This provides an array of laminar voids in the body. The ceramic is doped to form boundary layers, terminations are applied, and the voids are then filled, such as by vacuum impregnation, with an electrode metal.

Multilayer doped ceramic capacitor

A multilayer ceramic dielectric capacitor comprises a plurality of layers of dielectric arranged in a stack. Between the dielectric layers are arranged metallic electrodes. Alternate electrodes in the stack extend to opposite end faces thereof, where they are electrically connected by end terminations. The electrodes each comprise a plurality of parallel conductive elements provided between two adjacent dielectric layers. The adjacent dielectric layers are bonded together along three of their edges and at the gaps between the conductive elements, thus providing a stronger structure than when the adjacent layers are only bonded at the three of their edges. The electrode pattern comprised by a plurality of parallel elements is particularly applicable to metal-impregnated ceramic dielectric capacitors, which employ fugitive electrodes that are burnt away during firing of the ceramic to leave spaces for subsequent metal impregnation.

Multilayer ceramic dielectric capacitors

End terminations for multilayer ceramic dielectric capacitors, particularly but not exclusively metal-impregnated capacitors, are provided by bonding a coarse ceramic powder, which is lightly coated with silver, to the capacitor ceramic by means of a glass frit in order to produce a porous pseudo end termination containing insufficient silver to provide a good contact to the capacitor electrodes. The exposed silver in the pseudo end termination is then provided with a silver sulphide layer and subsequently the pseudo end termination is impregnated with lead. The end termination thus formed is comprised substantially of lead, which is held in place by the silver sulphide layer, that is wetted by the lead, on the bonded ceramic powder, and thus low cost and readily solderable.

Conductive and porous end terminations for metal-impregnated multilayer ceramic dielectric capacitors are provided by firing a silver, or silver alloy, and glass frit onto respective end regions of a sintered capacitor stack. The exposed silver of the fired terminations is provided with a silver sulphide layer, the latter being a good electrical conductor and acting as a barrier between the silver and the impregnation metal, for example lead, during a subsequent impregnation step, whereby to prevent leaching of the silver. The termination is readily solderable by virtue of the silver sulphide layer being wetted by the lead during the impregnation step and resulting in a lead coating in the termination.

Base metal electrodes are used in ceramic capacitors with a dielectric material comprising barium titanate, barium oxide, magnesium ortho-titanate, calcium titantate, and barium, strontium or calcium zirconate.

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Bishop's Stortford, United Kingdom

John H Alexander