Via paste compositions and use thereof to form conductive vias in circuitized ceramic substrates

A multilayer circuitized ceramic structure comprising at least two insulating layers of dielectric ceramic composition having insulated therebetween a thin electrically-conductive body, said structure having one or more vertical via holes formed through at least one insulating layer present at a surface of said structure and communicating with said electrically-conductive body, characterized by said via hole being filled with a conductive via body comprising an electrically-conductive skeletal network of a minor amount by volume of a metal contained within a major amount by volume of a ceramic matrix, said conductive via body being a solid, non-porous mass represented by cosintered packed spheres of ceramic material having the spaces therebetween filled with particles of said metal which are smaller in size than said spheres, to form a conductive path between the surface of said via body present at a surface of said ceramic circuit structure and said thin electrically-conductive body otherwise insulated between said layers of dielectric ceramic composition, the ceramic composition of said dielectric layers being cosinterable with said ceramic matrix of each said via body, whereby the ceramic matrix is cosintered with and integrated with the dielectric layer in the area of said via hole to form a hermetic seal between said via body and said dielectric layer.

A cosinterable via-fill paste composition comprising a uniform mixture of (a) a major amount by volume of spheres of ceramic composition having a substantially- uniform average diameter between about 0.5 .mu.m and 6 .mu.m, (b) a minor amount by volume of particles of low-resistive metal having a maximum size between about 1/3 and 1/4 the diameter of said ceramic spheres, and (c) a minor amount of an organic binder material in a volatile vehicle, said mixture containing a sufficient volume of said ceramic spheres to form densely packed via fill in which each of said spheres is in surface contact with at least two other spheres and a sufficient volume of said smaller metal particles to fill substantially all of the void spaces surrounding said ceramic spheres, whereby when said uniform mixture of spheres and metal particles is cosintered, there results a solid, substantially non-porous conductive via body comprising a continuous skeletal network of said metal contained within a matrix of ceramic composition.

A conducting composite having a thermal coefficient of expansion matched to the thermal coefficient of the expansion of a glass-ceramic layer, comprising a paste containing a mixture of a minor amount by volume of copper particles and a major amount by volume of glass-ceramic spheres having a thermal coefficient of expansion about the same as that of said glass-ceramic layer, said copper particles having a maximum dimension less than about one-third to about one-fourth the uniform diameter of said glass-ceramic spheres.