Method of making circuitized substrates utilizing smooth-sided conductive layers as part thereof
View Patent ↗A circuitized substrate in which two conductive layers (e.g., electroplated copper foil) are bonded (e.g., laminated) to an interim dielectric layer. Each of the two foil surfaces which physically bond to the dielectric are smooth (e.g., preferably by chemical processing) and include a thin, organic layer thereon, while the outer surfaces of both foils are also smooth (e.g., preferably also using a chemical processing step). One of these resulting conductive layers may function as a ground or voltage plane while the other may function as a signal plane with a plurality of individual signal lines as part thereof. An electrical assembly and an information handling system utilizing such a circuitized substrate are also provided, as is a method of making the substrate.
1. A method of making a circuitized substrate comprising:
providing at least one dielectric layer;
providing first and second electrically conductive layers each having a first side of a first, relatively low roughness and a second side of a second roughness greater than said first, relatively low roughness of said first sides;
treating said first and second sides of said first and second electrically conductive layers with a first chemical treatment so as to etch said first and second sides and thereby minimally increase said first relatively low roughness of said first sides to a first greater roughness and also minimally increase said second roughness of said second sides to a second greater roughness greater than said first greater roughness, said first chemical treatment including depositing a thin organic layer on said first and second sides of said first and second electrically conductive layers;
bonding said first sides of said first and second electrically conductive layers having said thin organic layer thereon following said treating of said first and second sides to said dielectric layer such that said dielectric layer is positioned substantially between said first and second electrically conductive layers;
treating said second sides of said first and second electrically conductive layers after said bonding of said first sides of said first and second electrically conductive layers to said dielectric layer with a second chemical treatment different from said first chemical treatment so as to etch said second sides but not to include a thin organic layer thereon, said second chemical treatment reducing both said second greater roughness of said second sides and the thickness of said first and second electrically conductive layers such that said second greater roughness of said second sides is substantially similar to said first greater roughness of said first sides during said bonding of said first sides to said dielectric layer; and
forming a circuit pattern within at least one of said electrically conductive layers.
2. The method of claim 1 wherein said providing said first and second electrically conductive layers comprises providing said first and second electrically conductive layers in which said first, relatively low roughness includes an RMS surface roughness within the range of from about 0.1 micron to about 0.5 micron prior to said treating of said first and second sides.
3. The method of claim 2 wherein said providing of said first and second electrically conductive layers comprises providing said first and second conductive layers in which said second roughness of said second sides includes an RMS roughness within the range of from about 1.0 micron to about 3.0 microns.
4. The method of claim 1 wherein said treating of said first and second sides with said first chemical treatment comprises subjecting said first sides to a solution including acid.
5. The method of claim 1 wherein said bonding of said first sides of said first and second electrically conductive layers to said dielectric layer is accomplished using a lamination process.
6. The method of claim 1 wherein said treating of said second sides of said first and second electrically conductive layers is accomplished using a fluid treatment device.
7. The method of claim 1 further including providing a plurality of openings within said second electrically conductive layers following said bonding of said second electrically conductive layers to said dielectric layer.
8. The method of claim 1 wherein said forming of said circuit pattern within said at least one of said electrically conductive layers is accomplished using a chemical treatment including exposing said at least one of said electrically conductive layers to an etchant.
9. The method of claim 8 wherein the total number of dielectric layers and electrically conductive layers within said circuitized substrate is greater than ten.
10. The method of claim 1 further including adding additional dielectric and electrically conductive layers on opposite sides of said circuitized substrate having said at least one dielectric layer and said first and second electrically conductive layers, and forming a circuit pattern within selected ones of said additional electrically conductive layers.