Method of manufacturing a multilayer circuit

A method of forming a multilayer circuit comprising the steps of:

• providing a first circuit assembly formed by the steps of,
• (1) selecting a planar platform having opposed mutually parallel surfaces,
• (2) forming first sites for a first part of a conductive circuit on a first of said surfaces of said platform,
• (3) plating in said first sites to form said first part of said conductive circuit in said first sites,
• (4) forming second sites for a second part of said conductive circuit on selected locations of said first part of said conductive circuit,
• (5) plating in said second sites to form said second part of said conductive circuit in said second sites,
• (6) laminating a layer of filled fluoropolymeric composite material onto said conductive circuit to define a laminated conductive circuit,
• (7) planarizing said laminated conductive circuit to expose selected locations of said conductive circuit and define a planarized surface, and
• wherein conductive circuit includes a layer of a diffusible conductive material on at least one selected location thereof;
• providing a second circuit assembly comprising a substrate of fusible dielectric material and a conductive circuit formed thereon and wherein said conductive circuit includes a layer of a diffusible conductive material on at least one selected location thereof;
• stacking said first and second assemblies one on top of the other so that said at least one selected location of diffusible conductive material of said first assembly aligns with said at least one selected location of diffusible conductive material of said second assembly;
• and
• laminating said stacked assemblies under heat and pressure effective to both fuse said filled fluoropolymeric composite material with said fusible dielectric material and diffuse said diffusible conductive material so as to form a cohesive multilayer substrate having a solid conductive interconnect between said first and second assemblies, said solid conductive interconnect being defined by said diffusible conductive material.