Multilayer ceramic substrate with circuit patterns

A multilayer cermaic circuit board made of a plurality of units which are laminated on one another and fired to form a unitary fired body, each of said units including a ceramic electrical insulating layer and a patterned electrical conductor layer supported on said ceramic electrical insulating layer, through-hole electrical conductors extending through the ceramic electrical insulating layers and connecting the patterned electrical conductor layers of the respective units to form a predetermined internal wiring circuit in said unitary fired body, both said patterned electrical conductor layers and said electrical coductors consisting essentially of a first electrical conductor material selected form the group consisting of Ag and electrically conductive Ag alloys, said fired body being the results of co-firing a laminate of green ceramic sheets having said patterned electrical conductor layers and said electrical conductors of said first material applied thereon in an oxidizing atmosphere to convert said first material into said internal wiring circuit and to convert said sheets into said unitary fired body, said circuit board also including a predetermined surface of said unitary fired body and in electrical connection with said internal wiring circuit at least one interface therebetween, said external wiring pattern consisting esentially of a second electrical conductor material selected from the group consisting of Cu and electrically conductive Cu alloys, said external wiring pattern being the result of applying said second material in the form of said external wiring pattern on said unitary fired body and then firing said second composition in a neutral or reducing atmosphere at a temperature below the eutectic temperature of a eutectic alloy of said first and second materials so that a liquid phase of said euctectic alloy is not formed at said interface of said internal wiring circuit and said external wiring pattern.

A multilayer ceramic circuit board made of a plurality of units which are lamianated on one another and fired to form a unitary fired body, each of said units including a ceramic electrical insulating layer and a patterned electrical conductor layer supported on said ceramic electrical insulating layer, through-hole electrical conductors extending through the ceramic electrical insulating layers and connecting the patterned electrical conductor layers of the respective units to form a predetermined internal wiring circuit in said unitary fired body, both said patterned electrical conductor layers and said electrical conductors consisting essentially of a first electrical conductor material selected from the group consisting of Ag and electrically conductive Ag alloys, said fired body being the result of co-firing a laminate of green ceramic sheets having said patterned electrical conductor layers and said electrical conductors of said first material applied thereon in an oxidizing atmosphere to convert said first material into said internal wiring circuit and to convert said sheets into said unitary fired body, said circuit board also including a predetermined external wiring pattern applied on at least one external surface of said unitary fired body, metal layer means interposed between said external wiring pattern and said internal wiring circuit and providing electrical connection means therebetween, said external wiring pattern consisting essentially of a second electrical conductor material selected from the group consisting of Cu and electrically conductive Cu alloys, said external wiring pattern being the result of applying said second material in the form of said external wiring pattern on said unitary fired body, placing said metal layer means between adjacent portions of said external wiring pattern and said internal wiring circuit and firing said second material in a neutral or reducing atmosphere at a temperature below the eutectic temperatures of eutectic alloys of said metal layer means with said first and second materials so that a liquid phase of a eutectic alloy is not formed at the interfaces of said metal layer means with said internal wiring circuit and said external wiring pattern.

A multilayer ceramic circuit board made of a plurality of units which are laminated on one another and fired to form a unitary fired body, each of said units including a ceramic electrical insulating layer and a patterned electrical conductor layer supported on said ceramic electrical insulating layer, through-hole electrical conductors extending through the ceramic electrical insulating layers and connecting the patterned electrical conductor layers of the respective units to form a predetermined internal wiring circuit in said unitary fired body, both said patterned electrical conductor layers and said electrical conductors consisting essentially of a first electrical conductor material selected from the group consisting of Ag and electrically conductive Ag alloys, said fired body being the result of co-firing a laminate of green ceramic sheets having said patterned electrical conductor layers and said electrical conductors of said first material applied thereon in an oxidizing atmosphere to convert said first material into said internal wiring circuit and to convert said sheets into said unitary fired body, said circuit board also including a predetermined external wiring pattern plated on at least one external surface of said unitary fired body and in electrical connection with said internal wiring circuit at at least one interface therebetween, said external wiring pattern consisting essentially of a second electrical conductor material selected from the group consisting of Cu and electrically conductive Cu alloys, said external wiring pattern being the result of electroless plating said second material in the shape of said wiring pattern on said unitary fired body.