Method for strengthening terminations on reduction fired multilayer capacitors

Claim 1

A method of producing base metal electrode multilayer capacitors having end terminations of increased strength, said method comprising the steps of: (a) forming a body of a plurality of alternate layers of a reduction resistant ceramic dielectric material and electrode layers, said electrode layers consisting of a paste of a base metal selected from the group consisting of nickel, cobalt, iron and copper and alloys thereof, dispersed in a solution of an organic vehicle dissolved in an organic solvent, each of said electrode layers being sandwiched between layers of said ceramic dielectric material and having edges alternatively exposed at opposite faces of said body; (b) firing said body first in air at low temperature to remove all organic residue, and then in an atmospheres reducing to the base metal of the electrode layer at a high temperature; (c) applying to each face of said fired body having exposed electrode edges, end terminations consisting of a coating of a conductive paste comprising a noble metal and a reduction-resistant glass, in an amount of less than 15% by volume of the noble metal, dispersed in a solution of an organic vehicle in an organic solvent; (d) heating said end terminations in air at a temperature of 300° C.-500° C. to remove all organic residue from said end terminations; (e) heating said end terminations at a temperature of from 700° C.-950° C. in a reducing atmosphere having an oxygen partial pressure not in excess of that which is reducing for said electrode layers for a time sufficient to sinter the terminations to form adherent bonds between the glass of said terminations and said ceramic dielectric material, and to form adherent and electrically conductive bonds between the metal of said termination and said electrode layers; (f) and then heating said end terminations for at least 15 minutes at a temperature of 375° C.-600° C. in an atmosphere in which the oxygen of partial pressure is at least equal to that of air thereby increasing the strength of said end terminations.

Claim 2

A method of producing base metal electrode multilayer capacitors having end terminations of increased strength, said method comprising the steps of: (a) forming a body of a plurality of alternate layers of a reduction resistant ceramic dielectric material and electrode layers, said electrode layers consisting of a paste of a base metal selected from the group consisting of nickel, cobalt, iron and copper and alloys thereof, dispersed in a solution of an organic vehicle dissolved in an organic solvent, each of said electrode layers being sandwiched between layers of said ceramic dielectric material and having edges alternatively exposed at opposite faces of said body; (b) firing said body first in air at low temperature to remove all organic residue, and then in an atmospheres reducing to the base metal of the electrode layer at a high temperature; (c) applying to each face of said fired body having exposed electrode edges, end terminations consisting of a coating of a conductive paste comprising a noble metal and a reduction-resistant glass, in an amount of less than 15% by volume of the noble metal, dispersed in a solution of an organic vehicle in an organic solvent; (d) heating said end terminations in air at a temperature of 300° C.-500° C. to remove all organic residue from said end terminations; (e) heating said end terminations at a temperature of from 700° C.-950° C. in a reducing atmosphere having an oxygen partial pressure not in excess of that which is reducing for said electrode layers for a time sufficient to sinter the terminations to form adherent bonds between the glass of said terminations and said ceramic dielectric material, and to form adherent and electrically conductive bonds between the metal of said termination and said electrode layers; (f) and then heating said end terminations for at least 15 minutes at a temperature of 375° C.-600° C. in an atmosphere in which the oxygen of partial pressure is at least equal to that of air thereby increasing the strength of said end terminations.