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Method for preventing spreading of a liquid on a solid surface, e.g., an adhesive placed on a substrate, and for preventing metal migration, in particular silver migration, between conductors deposited on a surface of a substrate, and articles produced by the method. The method comprises application

Method for preventing spreading of a liquid on a solid surface, e.g., an adhesive placed on a substrate, and for preventing metal migration, in particular silver migration, between conductors deposited on a surface of a substrate, and articles produced by the method. The method comprises application of a layer of polymer having room temperature critical surface tension of wetting less than about 20 dyn/cm, and less than about 0.1 μm thick, to at least a part of the surface. The polymer layer can be applied by any convenient method, including dipping, spraying, painting, printing, and plasma deposition. A preferred polymer is poly(1H, 1H-pentadecafluorooctyl methacrylate) (PDFOM), which can be advantageously applied in the form of a solution, typically in a fluorinated hydrocarbon such as Freon.RTM. TF, with PDFOM concentration typically between about 0.001% and about 2% by weight. Thin PDFOM layers according to the invention covering the substrate area on which the adhesive is placed later do not unduly decrease the strength of the adhesive bond formed, and have no measurable effect on the electrical conductivity of a conducting adhesive bond. Because of these properties, a substrate surface can be coated with PDFOM, such as by dipping or spraying, and the adhesive be applied to the coated surface. Metal migration is prevented by preventing formation of a continuous electrolyte film, typically an aqueous film, between conductors at different electrical potentials. This can be achieved by coating at least a part of the substrate with the polymer, e.g., PDFOM.

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1. Method for fabricating an article comprising a substrate having at least one first surface region covered with a substance at least part of which is capable of undergoing surface mass migration, and at least one second surface region that is not covered with the substance, the method comprising

1. Method for fabricating an article comprising a substrate having at least one first surface region covered with a substance at least part of which is capable of undergoing surface mass migration, and at least one second surface region that is not covered with the substance, the method comprising (a) applying a layer of material to at least part of the second surface region, characterized in that (b) the material comprises a polymer having a critical surface tension of wetting of less than about 20 dyn/cm at room temperature, and (c) the layer of material applied is no more than approximately 0.1 μm thick. 2. Method of claim 1, wherein the substance capable of undergoing surface mass migration comprises a liquid, and the mass migration is spontaneous spreading of the liquid. 3. Method of claim 1, wherein the layer of material is applied also to at least part of the first surface region before that region is covered with the substance. 4. Method of claim 1, wherein the layer of material is applied to the first and second surface regions before the first region is covered with the substance, the substance is an adhesive, and the strength after curing of the bond between adhesive and substrate is no less than about 50% of the strength of a bond formed between adhesive and substrate in the absence of the layer of material thereon. 5. Method of claim 1 wherein the substance covering the first surface region is an adhesive, a solid item to be bonded to the substrate is placed in contact with the adhesive, and the layer of material is applied after placing the item in contact with the adhesive, but prior to curing the adhesive. 6. Method of claim 1 wherein the substance capable of undergoing surface mass migration is a metal comprising an electrical conductor disposed on the substrate, and the mass migration is metal migration. 7. Method of claims 2 or 6 wherein the layer of material is applied by contacting at least part of the surface regions with a solution comprising the polymer. 8. Method of claim 7 wherein the polymer is poly (1H, 1H-pentadecafluorooctyl methacrylate), the solvent is a fluorinated hydrocarbon and the concentration of the polymer in the solvent is at least about 0.001% by weight. 9. Method of claim 8, wherein the concentration of the polymer in the solvent is less than about 2% by weight. 10. Method of claims 2 or 6 wherein the applying of the material is done by dipping the substrate into a solution comprising the polymer. 11. Method of claims 2 or 6 wherein the applying of the material is done by spraying the substrate with a solution comprising the polymer. 12. Method of claim 6 wherein the conductor comprises silver. 13. Method of claim 12 wheren the layer of material is applied only to a part of the second surface region. 14. Method of claim 12 wherein the layer of material is applied to the conductor and at least part of the second surface region. 15. Method for fabricating an article comprising a substrate and a solid item affixed to a surface of the substrate by means of adhesive bonding, the method comprising (a) contacting, prior to application of the adhesive, at least part of the surface of the substrate with an amount of a 0.001% to 2% by weight solution of poly (1H, 1H-pentadecafluorooctyl methacrylate) (PDFOM), the amount being sufficient to result in formation on the surface of a layer of PDFOM less than about 0.1 μm thick, and (b) placing the adhesive and the solid item onto the PDFOM-covered substrate surface. 16. Method for fabricating an article comprising a substrate and a solid item affixed to a surface of the substrate by means of adhesive bonding, the method comprising (a) placing the adhesive and the solid item onto the surface of the substrate, and thereafter, but prior to curing the adhesive, (b) contacting at least part of the surface of the substrate with an amount of a 0.001% to 2% by weight solution of poly(1H, 1H-pentadecafluorooctyl methacrylate) (PDFOM), the amount being sufficient to result in formation on the surface of a layer of PDFOM less than about 0.1 μm thick. 17. Method for fabricating an article comprising a plurality of spaced apart electrical conductors comprisng metallic silver deposited on an insulating substrate, the method comprising contacting at least part of the surface of the substrate bearing the conductor with an amount of a 0.001% to 2% by weight solution of poly (1H,1H-pentadecafluorooctyl methacrylate) (PDFOM), the amount being sufficient to result in formation on the surface of a layer of PDFOM less than about 0.1 μm thick. 18. Method of claims 15, 16, or 17 wherein PDFOM is dissolved in a fluorinated hydrocarbon. 19. Article comprising (a) a substrate, and (b) a semiconductor electronic device affixed to a substrate surface by means of an adhesive, characterized in that (c) a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, is disposed over at least a part of the substrate surface including the area to which the device is affixed. 20. Article comprising (a) a substrate, and (b) a semiconductor electronic device affixed to a substrate surface by means of an adhesive, characterized in that (c) a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, is disposed over at least a part of the substrate surface and over at least a part of the device. 21. Article comprising (a) a substrate, and (b) a plurality of spaced apart electrical conductors comprising metallic silver deposited on a surface of the substrate, characterized in that (c) a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, is disposed over at least a part of the substrate surface. 22. Article according to claim 21 wherein the layer is disposed also over at least one of the conductors. 23. Article according to claims 19, 20, or 21 wherein the polymer is poly (1H, 1H-pentadecafluorooctyl methacrylate). 24. Method for manufacturing an article comprising a substrate and a semiconductor device affixed to a substrate surface by means of an adhesive,characterized in that the method comprises disposing a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, over at least a part of the substrate surface including the area to which the device is to be affixed. 25. Method for manufacturing an article comprising a substrate and a semiconductor device affixed to a substrate surface by means of an adhesive characterized in that the method comprises disposing a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, over at least a part of the substrate surface and over at least a part of the device. 26. Method for manufacturng an article comprising a substrate and a plurality of spaced apart electrical conductors comprising metallic silver deposited on a surface of the substrate, characterized in that the method comprises disposing a layer, consisting essentially of polymer having a room temperature critical surface tension of wetting less than about 20 dyn/cm, the layer being less than about 0.1 μm thick, over at least a part of the substrate surface.