Methods of treating metal surfaces and devices formed thereby
View Patent ↗Embodiments of the present invention relate generally to methods of treating metal surfaces to enhance adhesion or binding to substrates, and devices formed thereby. In some embodiments of the present invention, methods of achieving improved bonding strength without roughening the topography of a metal surface are provided. The metal surface obtained by this method provides strong bonding to resin layers. The bonding interface between the treated metal and the resin layer exhibits resistance to heat, moisture, and chemicals involved in post-lamination process steps, and therefore can suitably be used in the production of PCB's. Methods according to some embodiments of the present invention are especially useful in the fabrication of high density multilayer PCB's, in particular for PCB's having circuits with line/spacing of equal to and less than 10 microns. Methods according to other embodiments of the present invention are particularly useful in the coating of metal surfaces in a wide variety of applications.
1. A method of treating a metal surface to promote adhesion between the metal surface and an organic material, comprising the steps of:
contacting the metal surface with a composition containing an oxidizing agent and a surface modifier compound, to oxidize the metal surface to form a metal oxide layer on the metal surface; and to terminate growth of the metal oxide layer by a self limiting reaction between the metal oxide layer and the surface modifier compound,
wherein the method further comprises a step of conditioning the metal oxide layer with a reducing agent, the reducing agent being selected from any one or more of formaldehyde, sodium thiosulfate, sodium borohydride, borane reducing agent represented by the following formula BH 3 NHRR′, wherein R and R′ are each selected from a group consisting of H, CH 3 and CH 2 CH 3 ,
wherein the contacting and the conditioning are carried out so as to not roughen the metal surface relative to the roughness of the metal surface prior to the contacting.
2. The method of claim 1 wherein after the conditioning the metal oxide layer has a thickness of about 200 nanometers and less.
3. The method of claim 1 wherein the metal oxide layer is comprised of copper oxide.
4. The method of claim 1 wherein the metal layer is oxidized with an oxidant selected from any one of more of: sodium chlorite, hydrogen peroxide, permanganate, perchlorate, persulphate, ozone, or mixtures thereof.
5. The method of claim 1 wherein the method is carried out at a temperature in the range of room temperature to about 80° C.
6. The method of claim 1 wherein the self limiting reaction becomes stable after about 2 to 15 minutes.
7. The method of claim 1 further comprising the step of:
contacting the metal surface with one or more organic molecules comprising a thermally stable base bearing one or more binding groups configured to bind the metal surface and one or more attachment groups configured to attach to the organic material.
8. The method of claim 7 wherein the one or more organic molecules is a surface active moiety.
9. The method of claim 7 wherein the one or more organic molecules is selected from the group of: a porphyrin, a porphyrinic macrocycle, an expanded porphyrin, a contracted porphyrin, a linear porphyrin polymer, a porphyrinic sandwich coordination complex, or a porphyrin array.
10. The method of claim 8 wherein said surface active moiety is a porphyrin.
11. The method of claim 7 wherein the one or more attachment group is comprised of an aryl functional group and/or an alkyl attachment group.
12. The method of claim 11 wherein the aryl functional group is comprised of a functional group selected from any one or more of: acetate, alkylamino, allyl, amine, amino, bromo, bromomethyl, carbonyl, carboxylate, carboxylic acid, dihydroxyphosphoryl, epoxide, ester, ether, ethynyl, formyl, hydroxy, hydroxymethyl, iodo, mercapto, mercaptomethyl, Se-acetylseleno, Se-acetylselenomethyl, S-acetylthio, S-acetylthiomethyl, selenyl, 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, 2-(trimethylsilyl)ethynyl, vinyl, and combinations thereof.
13. The method of claim 11 wherein the alkyl attachment group comprises a functional group selected from any one or more of: acetate, alkylamino, allyl, amine, amino, bromo, bromomethyl, carbonyl, carboxylate, carboxylic acid, dihydroxyphosphoryl, epoxide, ester, ether, ethynyl, formyl, hydroxy, hydroxymethyl, iodo, mercapto, mercaptomethyl, Se-acetylseleno, Se-acetylselenomethyl, S-acetylthio, S-acetylthiomethyl, selenyl, 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, 2-(trimethylsilyl)ethynyl, vinyl, and combinations thereof.
14. The method of claim 1 wherein the organic material is an organic substrate comprised of any one of more of: electronic substrates, PCB substrates, semiconductor substrates, photovoltaic substrates, polymers, ceramics, carbon, epoxy, glass reinforced epoxy, phenol, polyimide resins, glass reinforced polyimide, cyanate, esters, Teflon, plastics and mixtures thereof.
15. The method of claim 1 wherein the surface modifier compound is selected from a porphyrin, a porphyrinic sandwich coordination complex, a porphyrin array, a silane, a sugar, inorganic molecules from the group consisting of molybdates, tungstates, tantalates, niobates, vanadates, isopoly or heteropoly acids of molybdenum, tungsten, tantalum, niobium, vanadium, and combinations of any of the foregoing.
16. The method of claim 15 wherein the surface modifier compound comprises the silane and the silane comprises one or more silane selected of am inoethyl-aminopropyl-trimethoxysilane, (3-Aminopropyl)trimethoxysilane, 1-[3-(Trimethoxysilyl)propyl]urea, (3-Aminopropyl) triethoxysilane, (3-Chloropropyl) trimethoxysilane, Dimethyldichlorosilane, (3-Glycidyloxypropyl)trimethoxysilane, 3-(Trimethoxysilyl)propyl methacrylate, Ethyltriacetoxysilane, Triethoxy(isobutyl)silane, Triethoxy(octyl) silane, Tris(2-methoxyethoxy)(vinyl)silane, Chlorotrimethylsilane, Methyltrichlorosilane, Silicon tetrachloride, Tetraethoxysilane, Phenyltrimethoxysilane, Chlorotriethoxysilane, ethylene-trimethoxysilane.
17. The method of claim 7 wherein the organic molecule comprises a silane having the formula A (4-X) SiB x Y, wherein each A is independently a hydrolysable group, where x=1 to 3, and B is independently an alkyl or aryl group, that contains or does not contain attachment group Y, wherein the attachment group Y comprises a functional group selected from the group consisting of amino, alkylamino, bromo, iodo, hydroxy, hydroxymethyl, formyl, bromomethyl, vinyl, allyl, S-acetylthiomethyl, Se-acetylselenomethyl, ethynyl, 2-(trimethylsilyl)ethynyl, mercapto, mercaptomethyl, 4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl, dihydroxyphosphoryl, selenyl, S-acetylthio, Se-acetylseleno, or the attachment group Y comprises an alcohol or a phosphonate.
18. The method of claim 1 wherein the surface roughness of the metal surface prior to the contacting is up to about 0.14 μm Ra and the surface roughness of the metal oxide after the conditioning is up to about 0.14 μm Ra.
19. The method of claim 1 wherein after the conditioning the oxide layer has a grain size in the range of about 200 nanometers and less.
20. The method of claim 3 wherein after the conditioning the copper oxide exhibits a substantially amorphous structure.