Method and apparatus for manufacturing multi layer printed circuit boards

Claim 1

A method for fabricating a printed circuit board comprising the steps of: (a) electrolytically forming a uniform, relatively pin-hole free thin first layer of a conductive material on a polished, homogenous, rigid substrate having a conductive surface; wherein there is low contact pressure between the first layer and the substrate surface; (b) depositing photosensitive resist onto said first layer of conductive material; (c) masking the photosensitive resist with a photomask to define a conductive circuit pattern on the surface of the resist; (d) exposing the masked photosensitive resist to light; (e) dissolving those portions of the resist corresponding to the conductive circuit pattern, forming three-dimensional cavities in the resist, to expose said first layer of conductive material according to said circuit pattern; (f) electrolytically forming a second layer of conductive material, of the same material as that of said first conductive material, upon the exposed portions of said first layer of conductive material, wherein a raised conductive circuit pattern is formed above the general plane of said first conductive layer, conforming to the three-dimentional cavity definition of the photosensitive resist image; said first and second conductive layers being integrally bonded to one another; (g) removing previously undissolved photosenitive resist from said first layer of conductive material, thereby exposing top and sidewall surface portions of said raised conductive circuit pattern configured to the shape of said three-dimensional cavity; (h) treating at least the three-dimensional top and sidewall surface portions of said raised conductive circuit pattern so as to provide a chemical conversion coating on said surface portions, thereby enhancing the adhesion properties of said surface portions to laminate insulator materials; (i) embedding said raised conductive circuit pattern on said first conductive lyaer within a uniform thickness of laminate insulator material, whereby the laminate material strongly adheres to said raised conductive circuit pattern across the entire three-dimensional said surface portions thereof; (j) separating the first conductive layer with said attached laminate and said embedded conductive layer from the rigid substrate; and (k) etching away said first conductive layer from said insulator material; whereby the conductive circuit pattern embedded in the laminate insulator material is exposed and lays flush and coplanar with the surface of the insulator material, with uniform cross-sectional thickness across the entire circuit board.

Claim 2

A method for fabricating a printed circuit board comprising the steps of: (a) electrolytically forming a uniform, relatively pin-hole free thin first layer of a conductive material on a polished, homogenous, rigid substrate having a conductive surface; wherein there is low contact pressure between the first layer and the substrate surface; (b) depositing photosensitive resist onto said first layer of conductive material; (c) masking the photosensitive resist with a photomask to define a conductive circuit pattern on the surface of the resist; (d) exposing the masked photosensitive resist to light; (e) dissolving those portions of the resist corresponding to the conductive circuit pattern, forming three-dimensional cavities in the resist, to expose said first layer of conductive material according to said circuit pattern; (f) electrolytically forming a second layer of conductive material, of the same material as that of said first conductive material, upon the exposed portions of said first layer of conductive material, wherein a raised conductive circuit pattern is formed above the general plane of said first conductive layer, conforming to the three-dimentional cavity definition of the photosensitive resist image; said first and second conductive layers being integrally bonded to one another; (g) removing previously undissolved photosenitive resist from said first layer of conductive material, thereby exposing top and sidewall surface portions of said raised conductive circuit pattern configured to the shape of said three-dimensional cavity; (h) treating at least the three-dimensional top and sidewall surface portions of said raised conductive circuit pattern so as to provide a chemical conversion coating on said surface portions, thereby enhancing the adhesion properties of said surface portions to laminate insulator materials; (i) embedding said raised conductive circuit pattern on said first conductive lyaer within a uniform thickness of laminate insulator material, whereby the laminate material strongly adheres to said raised conductive circuit pattern across the entire three-dimensional said surface portions thereof; (j) separating the first conductive layer with said attached laminate and said embedded conductive layer from the rigid substrate; and (k) etching away said first conductive layer from said insulator material; whereby the conductive circuit pattern embedded in the laminate insulator material is exposed and lays flush and coplanar with the surface of the insulator material, with uniform cross-sectional thickness across the entire circuit board.