HK1092189A - Pre-plating surface treatments for enhanced galvanic-corrosion resistance - Google Patents
Pre-plating surface treatments for enhanced galvanic-corrosion resistance Download PDFInfo
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- HK1092189A HK1092189A HK06112826.9A HK06112826A HK1092189A HK 1092189 A HK1092189 A HK 1092189A HK 06112826 A HK06112826 A HK 06112826A HK 1092189 A HK1092189 A HK 1092189A
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Description
Technical Field
Metal-coated metal (or metal alloy) graphite composites have been used in thermal applications. Unfortunately: conventional methods for coating such metal graphite composites have disadvantages. For example, it has been found that when conventionally coated metal graphite composites are used, graphite extends into and tends to protrude from the metal coating and thus cause the coating to fail. Such fibers protruding from the metal coating form channels for the transmission of water vapor, resulting in corrosion. Likewise, the fibers protruding from the coating also provide channels for the gas to permeate through the composite.
Another problem with conventional metal graphite composites is that: the difference in thermal expansion coefficient between the surface graphite in the composite and the coating results in the formation of cracks in the brittle metal coating. Such defects impair the performance of the metal graphite composite material.
For the foregoing reasons, it would be advantageous to develop a metal-coated metal graphite composite material that is gas tight.
For the foregoing reasons, it would be advantageous to develop a metal-coated metal graphite composite material that is impervious to chemicals.
For the foregoing reasons, it would be advantageous to develop a metal-coated metallic graphite material that is corrosion resistant.
For the foregoing reasons, there is a need to develop a method of making metal-coated metal graphite composites that are resistant to corrosion.
For the foregoing reasons, there is a need to develop a method of preparing a metal-coated metal graphite composite material that is gas tight.
Summary of The Invention
The present invention relates to a process comprising (a) removing graphite from at least one surface of a metal graphite composite material; (b) carrying out chemical cleaning or plasma etching on the surface of the metal graphite composite material; (c) applying a metal-containing material to a surface of the chemically cleaned or plasma etched metal graphite composite material and thereby forming an intermediate layer; (d) a metal coating is applied to the intermediate layer and thereby a metal-coated metal graphite composite material is formed. The invention also relates to a metal-coated metal graphite composite material that can be made by this method, such as a metal-coated metal graphite composite material comprising: (a) a metal graphite composite substrate having at least one substantially graphite-free surface; (b) a metal-containing intermediate layer on the substrate; and (c) a metal coating on the intermediate layer.
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These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. Wherein:
FIG. 1 is a diagram of an aluminum-graphite composite material made in accordance with the present invention; and
fig. 2 is a diagram of an aluminum graphite composite material made without additional surface modification (not in accordance with the present invention) in which the fibers protrude from the nickel coating.
Detailed Description
The present invention relates to a process comprising (a) removing graphite from at least one surface of a metal graphite composite material; (b) carrying out chemical cleaning or plasma etching on the surface of the metal graphite composite material; (c) applying a metal-containing material to a surface of the chemically cleaned or plasma etched metal graphite composite material and thereby forming an intermediate layer; (d) a metal coating is applied to the intermediate layer and thereby a metal-coated metal graphite composite material is formed. Preferably, the composite material formed in step (d) of the method has a surface that is gas tight or corrosion resistant or both. The invention also relates to a metal-coated composite material comprising: (a) a metal graphite composite substrate having at least one substantially graphite-free surface; (b) a metal-containing intermediate layer located on a surface of the substrate; and (c) a metal coating on the intermediate layer.
The metal graphite composite material from which the graphite is removed from its surface can be any metal graphite composite material that, when used in accordance with the present invention, is capable of producing the metal-coated metal graphite composite material of the present invention. Generally, the metal graphite composite material may be an aluminum graphite composite material, a copper graphite composite material, a magnesium graphite material, or a combination of these materials. Likewise, aluminum alloy graphite composites, copper alloy graphite composites, magnesium alloy graphite materials, and combinations of the foregoing may also be used.
The metal graphite composite material is preferably a metal matrix composite containing random in-plane discontinuous fibers. The use of random planar discontinuous fibers allows the metal matrix composite to have a high fiber volume fraction (as used herein, "planar" is understood to mean the X-Y plane, e.g., a plane parallel to the bonding surface of the heat sink). Furthermore, by using plane oriented fibers, substantially all of the fibers can help control the coefficient of thermal expansion in the X-Y plane. Although the Z-direction coefficient of thermal expansion is not controlled by planar fibers, such control is generally not necessary for heat sink applications because the integrated circuit or other object is attached to the X-Y oriented surface of the heat sink.
Advantageously, the use of these planar oriented fibers allows the coefficient of thermal expansion to be selected over a wide range of values. The desired volume fraction of the planar oriented fibers is selected to achieve the desired coefficient of thermal expansion. By orienting substantially all of the fibers in the X-Y plane, a very high volume fraction can be obtained. This allows the volume fraction and accordingly the coefficient of thermal expansion to be selected over a large range of values.
In one embodiment, the metal graphite composite material has a volume fraction of random in-plane discontinuous fibers of about 0.15 to about 0.6. In another embodiment, a minority of the random in-plane discontinuous fibers are oriented out-of-plane at an angle greater than about 10 °. In a preferred embodiment, the random in-plane discontinuous fibers are uniformly distributed within the metal matrix composite. Preferably, the metal matrix composite is an aluminum graphite composite.
The metal graphite composite material typically has a carbon fiber content sufficient to enable the material to be used in the present invention. In one embodiment, the composite material has a carbon fiber content of at least about 30 wt%, or at least about 40 wt%. In one embodiment, the metal graphite composite material has from about 30 wt% to about 40 wt% carbon fibers. The metal graphite composite material may have various contents of carbon fibers. In one embodiment, the carbon content is at least about 15%. In another embodiment, the carbon content is from about 15% to about 60%. Examples of suitable metal graphite composites can be found in U.S. s.n.09/855,466, the contents of which are incorporated herein by reference in their entirety.
The graphite may be removed from the metal graphite composite material by any method that enables the graphite to be removed from the composite material to produce the composite material of the present invention. For example, the graphite may be removed by one technique selected from the group consisting of, for example, an oxidation technique, a vibration grinding (vibrating) technique, a plasma stripping (plasma stripping) technique, a glow discharge technique, a mechanical blasting (mechanical blasting) technique, a grinding (lapping) technique, and a combination thereof. Vibratory abrading techniques typically involve the use of components and abrasives that move relative to the respective surfaces. Plasma stripping techniques typically involve a portion of the ionized gas (e.g., Ar) containing equal amounts of positive and negative charges as well as some other non-ionized gas particles striking the surface of the component. Glow discharge techniques typically involve the use of a completely neutral zone as well as a zone containing net positively and negatively charged particles that strike the surface of the component. Most thin film processes can use "plasma" and "glow discharge" interchangeably. Mechanical blasting techniques typically involve the use of abrasive materials, such as glass beads, alumina powder, which impinge under pressure on the component surface. Grinding techniques typically involve the use of a liquid grinding medium that is injected between the assembly and a rotating plate on one or both sides of the assembly. These techniques are known to the skilled person.
When oxidation is selected as the technique for removing graphite, the metal graphite composite material may be oxidized by any technique capable of removing at least some of the graphite from the surface of the metal graphite composite material. Preferably, the metal graphite composite material is oxidized by heating the metal graphite composite material to a temperature sufficiently high to oxidize the composite material and remove graphite from the composite material. Generally, the maximum temperature of the oxidized metal graphite composite material is below the melting temperature of the metal graphite composite material. In one embodiment, the temperature of the metal oxide graphite composite material is at least about 250 ℃.
The amount of graphite removed from the surface of the metal graphite composite material is sufficient to enable the metal graphite composite material to be made according to the method of the present invention. In one embodiment, at least 10% of the residual graphite remains on or below the surface of the metal graphite composite material. In another embodiment, less than 10% of the residual graphite remains on or below the surface of the metal graphite composite material. In another embodiment, substantially all of the graphite is removed from the surface. In another embodiment, one hundred percent of the graphite is removed from the surface.
The metal graphite composite material may be chemically cleaned by any technique capable of producing a metal graphite composite material according to the present invention. Examples of suitable chemicals for cleaning the surface of the metal graphite composite material include chemicals used in higher pH alkaline chemical cleaning techniques. The metal graphite composite material is typically cleaned by a dipping and rinsing operation. In one embodiment, the metal composite is subjected to a plasma etching process in place of a chemical cleaning process.
The metal-containing intermediate layer, e.g., film, applied to the surface of the chemically cleaned or plasma etched metal graphite composite material may contain a metal that produces the metal-coated metal graphite composite material of the present invention. Examples of suitable metallic materials include zinc, gold, and combinations thereof. Preferably, the applied metal-containing intermediate layer is a zinc-containing material. More preferably, the zinc-containing material is a zincate.
The metal-containing material applied to the surface of the chemically cleaned or plasma etched graphite composite material typically forms an intermediate layer that can have various thicknesses. In one embodiment, the thickness of the intermediate layer is less than about 1 micron. In another embodiment, the intermediate layer has a thickness in a range from about 1 nanometer to about 1 micrometer.
The metal-containing intermediate layer may be applied to the surface of the chemically cleaned or plasma etched metal graphite composite material by any suitable technique capable of treating the metal graphite composite material according to the method of the present invention and preferably forming a composite material having a surface that is gas tight or corrosion resistant or both. Examples of suitable techniques for applying the metal-containing material to the surface of the chemically cleaned or plasma etched metal graphite composite material include plating (e.g., dip coating techniques, electroplating techniques), physical vapor deposition techniques, chemical vapor deposition techniques, ion vapor deposition techniques, and combinations thereof. These techniques are well known and known to those of ordinary skill. Preferably, the metal-containing material is added to the surface of the metal graphite composite material by an electroplating technique.
The metal coating applied to the intermediate layer may be made of any metal that enables the present invention. Typically, the metal of the coating will be selected from the group consisting of aluminum, copper, nickel, gold, silver, rhodium, ruthenium, aluminum alloys, copper alloys, nickel alloys, gold alloys, silver alloys, rhodium alloys, ruthenium alloys, and combinations of the foregoing. In one embodiment, the metal coating applied to the intermediate layer comprises a multilayer coating, for example a coating consisting of nickel and gold layers.
The metal coating is applied by any technique that enables the application of a suitable metal to a surface covered by the metal-containing material. The metal coating is applied by a technique selected from plating techniques such as electroplating, physical vapor deposition techniques, chemical vapor deposition techniques, ion vapor deposition techniques, and combinations thereof. As mentioned above, these techniques are well known and known to the skilled person.
The metal coating applied to the intermediate layer typically has a thickness of less than about 100 microns. Preferably, the metal coating is at least about 1 micron, or from about 1 micron to about 75 microns. Preferably, the coating is a galvanic-corrosion (galvanic-corrosion) resistant and gas-tight coating.
In use, a suitable metal graphite composite material is selected for treatment. Graphite is removed from at least one surface of the metal graphite composite material. Advantageously, fibers extending onto the surface and other on/in the metal surface are removed in a controlled manner. The graphite present on at least one surface is typically present in an amount less than about 60% of the total surface area. In one embodiment, at least one surface of the metal graphite composite material is smoothed prior to chemical cleaning or etching of the metal graphite composite material, e.g., prior to or after removal of the graphite from the surface and prior to chemical cleaning or plasma etching of the composite material. The surface may be smoothed by a technique selected from the group consisting of lapping techniques, ivadizing techniques, peening techniques, and combinations thereof.
Once the graphite is removed from the surface of the metal graphite composite material, the metal graphite composite material is chemically cleaned or plasma etched using a suitable technique. Thereafter, an intermediate layer is formed by applying a metal-containing material to the surface of the chemically cleaned or plasma etched metal graphite composite material. Finally, a metal coating is applied to the intermediate layer to form a metal-coated metal graphite composite material. The composite material formed by the method of the present invention preferably has a surface that is hermetic or corrosion resistant or hermetic and corrosion resistant. Also, the composite material of the present invention is preferably unaffected by chemicals. Advantageously, the metal-coated metal graphite composite material of the present invention can be corrosion resistant and gas tight under a variety of conditions of use. The coated composites of the present invention were subjected to a salt spray test according to military or ASTM standards to test the corrosion performance of the coated composites. The composite material of the present invention can be placed in a sealed chamber with a gas (e.g., He) pressure and tested for leak rate to test for hermeticity.
Although the invention has been described in detail with reference to certain preferred versions thereof, other variations are possible. Therefore, the spirit and scope of the appended claims should not be limited to the description of the versions contained herein.
Claims (29)
1. A method, comprising:
(a) removing graphite from at least one surface of the metal graphite composite material;
(b) carrying out chemical cleaning or plasma etching on the surface of the metal graphite composite material;
(c) applying a metal-containing material to a surface of the chemically cleaned or plasma etched metal graphite composite material and thereby forming an intermediate layer;
(d) a metal coating is applied to the intermediate layer and thereby a metal-coated metal graphite composite material is formed.
2. The method of claim 1, wherein the graphite is removed by a technique selected from the group consisting of an oxidation technique, a vibratory milling technique, a plasma stripping technique, a glow discharge technique, a mechanical blasting technique, a milling technique, and combinations thereof.
3. The method of claim 1, wherein the composite formed in step (d) has a surface that is hermetic or corrosion resistant or hermetic and corrosion resistant.
4. The method of claim 1, wherein in step (c), the applied metal-bearing material is a zinc-bearing material.
5. The method of claim 4, wherein the zinc-containing material is a zincate.
6. The method of claim 1, wherein the metal coating in step (d) is selected from the group consisting of aluminum, copper, nickel, gold, silver, rhodium, ruthenium, aluminum alloys, copper alloys, nickel alloys, gold alloys, silver alloys, rhodium alloys, ruthenium alloys, and combinations thereof.
7. The method of claim 1, wherein the metal graphite composite material has a carbon fiber content of about 30 wt% to about 40 wt%.
8. The method of claim 1, wherein the metal graphite composite material is selected from the group consisting of aluminum graphite composite materials, copper graphite composite materials, magnesium graphite materials, aluminum alloy graphite composite materials, copper alloy graphite composite materials, magnesium alloy graphite materials, and combinations thereof.
9. The method of claim 1, wherein in step (a), the graphite is removed by oxidizing the metal graphite composite material by heating the metal graphite composite material to a temperature sufficiently high to oxidize the composite material and remove the graphite from the composite material.
10. The method of claim 9, wherein the temperature is at least about 250 ℃.
11. The method of claim 9, wherein the maximum temperature is below the metal melting temperature of the metal graphite composite material.
12. The method of claim 1, wherein the metal-containing material applied in step (c) forms a thin film of zinc-containing material having a thickness of less than about 1 micron.
13. The method of claim 1 wherein the metal-containing material applied in step (c) forms a zincate film having a thickness of from about 1 nanometer to about 1 micrometer.
14. The method of claim 1, wherein the metal coating is applied by a technique selected from the group consisting of plating techniques, dip coating techniques, physical vapor deposition techniques, chemical vapor deposition techniques, ion vapor deposition techniques, and combinations thereof.
15. The method of claim 1, wherein the metal coating is applied to the intermediate layer comprising zinc and the metal coating has a thickness of less than about 100 microns.
16. The method of claim 1, wherein the metal coating is applied to the zinc-containing film and the metal coating is at least about 1 micron, or from about 1 micron to about 75 microns.
17. The method of claim 1, wherein the method further comprises: the surface of the metal graphite composite material is smoothed prior to chemical cleaning or etching of the metal graphite composite material.
18. The method of claim 17, wherein the surface is smoothed by a technique selected from the group consisting of a grinding technique, a shot peening technique, and combinations thereof.
19. A metal-coated composite material, comprising:
(a) a metal graphite composite substrate having at least one substantially graphite-free surface;
(b) a metal-containing intermediate layer on the surface of the substrate; and
(c) a metal coating on the intermediate layer.
20. The composite of claim 19, wherein at least one surface of the composite is air tight.
21. The composite of claim 19, wherein at least one surface of the composite is corrosion resistant.
22. The composite of claim 19, wherein at least one surface of the composite is hermetic and corrosion resistant.
23. The composite material of claim 19, wherein the amount of graphite present on at least one surface is less than about 60% of the total surface area.
24. The composite of claim 19, wherein the material is selected from the group consisting of aluminum graphite composite, aluminum alloy graphite composite, and combinations thereof.
25. The composite material of claim 19, wherein the material has a carbon fiber content of about 15% to about 60%.
26. The composite material of claim 19, wherein the metal-containing intermediate layer comprises a zinc-containing material.
27. The composite of claim 19, wherein the metal-containing intermediate layer comprises a zincate.
28. A metal-coated metal graphite composite material, comprising:
(a) a metal graphite composite substrate having at least one substantially graphite-free surface;
(b) a metal-containing intermediate layer on the surface of the substrate; and
(c) a metal coating on the intermediate layer;
wherein the composite material is made by a method comprising:
(1) removing graphite from at least one surface of the metal graphite composite material;
(2) chemically cleaning or plasma etching at least one surface of the metal graphite composite material;
(3) applying a metal-containing material to a surface of the chemically cleaned or plasma etched metal graphite composite material and thereby forming an intermediate layer; and
(4) a metal coating is applied to the intermediate layer and thereby a metal-coated metal graphite composite material is formed.
29. The composite of claim 28, wherein the metal-coated metal graphite composite formed in step (4) has a surface that is hermetic or corrosion resistant or hermetic and corrosion resistant.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US60/442,042 | 2003-01-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| HK1092189A true HK1092189A (en) | 2007-02-02 |
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