Patent Application
20090317280
1. Field of the Invention
The present invention relates to a method for manufacturing a target, in particular, to a method for manufacturing a metal-based ceramic composite target containing noble metal.
2. Description of the Related Art
A hard disk is an important device used for the storage of a large amount of data, and data is mainly stored in a thin-film magnetic recording layer on a hard disk, the main component of which is a Co-based alloy material having the noble metal Pt. It is well known that the thin-film magnetic recording layer is applied onto the hard disk by a sputtering process with a target for sputtering.
In the prior art, CoCrPt—SiO2 film is a primary material used as magnetic recording film in current high-capacity hard disks. Due to SiO2 ceramic contained therein, a powder metallurgy process needs to be used to produce CoCrPt—SiO2 target, that is, selecting Co, Cr, and Pt powders to be thoroughly mixed with SiO2 powder, or selecting premixed CoCrPt metallic powder to be thoroughly mixed with SiO2, and then molding and compacting the target by using a hot pressing or hot isostatic pressing process.
There are two well-known powder mixing methods, i.e., dry and wet powder mixing, and the main difference between them is that the powder mixing is either carried out in a solution or not. However, neither of these methods can cause the metal and ceramic powders to be uniformly mixed; normally, this mixing cannot be accomplished due to an overly large difference between their specific gravities.
Moreover, in the wet powder mixing process, the Co, Cr, Pt, and SiO2 powders are mixed in a mixing ball, to form a mixed slurry. Therefore, after the wet powder mixing process, when taken out of the mixing ball, part of the mixed slurry will remain in and adhere to the mixing ball. Because the content of noble metal Pt in the CoCrPt—SiO2 target is above 30 wt %, the wet powder mixing process will lead to the loss of a large amount of noble metal Pt, thus increasing the production cost of the target.
Therefore, there is a need to provide a method for manufacturing a metal-based ceramic composite target containing noble metal to solve the above problems.
The present invention is directed to a method for manufacturing a metal-based ceramic composite target containing noble metal, comprising the steps of: (a) providing a magnetic metal powder and a ceramic powder with purities higher than 99.9%; (b) wet powder mixing the magnetic metal powder and the ceramic powder in a solvent, to form a slurry, where the ceramic powder is applied onto the surface of the magnetic metal powder; (c) drying the slurry, to form a ceramic-metal composite powder; (d) dry powder mixing the ceramic-metal composite powder with a noble metal powder that has a purity higher than 99.9%; and (e) molding and compacting the mixed ceramic-metal composite powder and noble metal powder, to form the metal-based ceramic composite target containing noble metal.
According to the manufacturing method of the present invention, the ceramic powder is firstly uniformly applied onto the surface of the magnetic metal powder by using the wet powder mixing process, and dried to obtain the ceramic-metal composite powder, which is then uniformly mixed with the noble metal powder by using the dry powder mixing process, and finally the ceramic-metal composite powder is made into the compact target by using a molding and compacting process. The manufacturing method of the present invention can uniformly mix the powders of the magnetic metal, the ceramic, and the noble metal, and reduce the loss of the noble metal in the production process of the target, so as to improve the quality of the target and decrease the production cost thereof.
In this embodiment, SiO2 or TiO2 is used as the ceramic powder 12. The particle size of the ceramic powder 12 is preferably 0.07 to 1.0 μm.
With reference to step S12, the ceramic powder 12 and the magnetic metal powder 11 is wet powder mixed in a solvent (e.g., water or alcohol), to form a slurry, where the ceramic powder 12 is applied onto the surface of the magnetic metal powder 11. In step S 12, the surface of the magnetic metal powder 11 and the surface of the ceramic powder 12 are differently charged, enabling the ceramic powder 12 to be applied onto the surface of the magnetic metal powder 11, thereby increasing uniformity of mixing. The time for the wet powder mixing is preferably 6 to 24 hours.
It is noted that on the basis of different mixing materials and conditions, in step S12, a further step of pH adjustment can be included, in which an acid or base solution is added to adjust the pH of the slurry, so that the surface of the magnetic metal powder and the surface of the ceramic powder 12 are differently charged.
With reference to step S13, the slurry is dried, to form a ceramic-metal composite powder. In this embodiment, a vacuum drying method is used to dry the slurry, in which the temperature for the vacuum drying is 80° C. to 160° C., the time is 2 to 6 hours, and the vacuum level is less than 760 torr.
With reference to step S14, the ceramic-metal composite powder is dry powder mixed with a noble metal powder 13 with a purity higher than 99.9%. In this embodiment, Pt is used as the noble metal powder 13, with a purity of higher than 99.95%, and the time for the dry powder mixing is preferably 4 to 8 hours.
With reference to step S15, the mixed ceramic-metal composite powder and noble metal powder 13 are molded and compacted, to form the metal-based ceramic composite target 1 containing noble metal according to the present invention. In this embodiment, the molding and compacting step is carried out by a hot pressing or hot isostatic pressing process, where the temperature for the molding and compacting is 800° C. to 1200° C., and the time for the molding and compacting is 1 to 4 hours.
The percent by weight (wt %) of the ceramic powder 12 is preferably 5% to 12%, the wt % of the noble metal powder 13 is 20% to 50%, and the rest of the wt % is the content of the magnetic metal powder 11. In this embodiment, the magnetic metal powder 11 is cobalt-chromium alloy, where the wt % of the ceramic powder 12 is 5% to 12%, the wt % of the noble metal powder 13 is 20% to 50%, the wt % of chromium in the cobalt-chromium alloy is 4% to 16%, and the rest is the wt % of cobalt in the cobalt-chromium alloy.
The following embodiments are used to describe the present invention in detail; however, it should be understood that the present invention is not limited to the disclosure of these embodiments.
In this embodiment, the production of the CoCrPt—SiO2 alloy target for sputtering is taken as an example. Firstly, a magnetic Co powder having a purity above 99.95%, as well as Cr powder, Pt powder, and SiO2 powder (with a particle size of 0.25 μm) also having a purity above 99.95%, are provided. The contents of Co, Cr, Pt, and SiO2 are 46 wt %, 5 wt %, 42 wt %, and 7 wt %, respectively. Then, Co powder, Cr powder, and SiO2 powder are put into deionized water of pH 7 and wet powder mixed for 18 hours. Next, the slurry of CoCr—SiO2 is placed in a vacuum oven, and dried at a vacuum level of 76 torr, where the drying temperature is 120° C., and the drying time is 4 hours, and thereby, SiO2 powder could be uniformly applied onto the surface of Co powder and Cr powder. Finally, the dried CoCr—SiO2 powder and Pt powder are thoroughly mixed for 4 hours by dry powder mixing without a solvent, and then the uniformly mixed powder is put into a graphite mold, and molded and compacted by hot pressing at 1100° C. for 1.5 hours, to form a CoCrPt—SiO2 target having high purity, fine structure, and uniform composition.
In this embodiment, the production of the CoCrPt—TiO2 alloy target for spluttering is taken as an example. Firstly, magnetic Co powder having a purity above 99.95%, as well as Cr powder, Pt powder, and TiO2 powder (with a particle size of 0.07 μm) also having a purity above 99.95%, are provided. The contents of Co, Cr, Pt, and TiO2 are 48 wt %, 13 wt %, 31 wt %, and 8 wt %, respectively. Then, Co powder, Cr powder, and TiO2 powder are put into deionized water, and wet powder mixed for 12 hours after adjusting the solution to pH 8 with aqueous ammonia. Next, the slurry of CoCr—TiO2 is placed in a vacuum oven, and dried at a vacuum level of 76 torr, where the drying temperature is 160° C., and the drying time is 2 hours, and thereby TiO2 powder could be uniformly applied onto the surface of Co powder and Cr powder. Finally, the dried CoCr—TiO2 powder and Pt powder are thoroughly mixed for 6 hours by dry powder mixing without a solvent, and then the uniformly mixed powder is sealed in stainless steel canning, and molded and compacted by hot pressing at 800° C. for 4 hours, to form a CoCrPt—TiO2 target having high purity, fine structure, and uniform composition.
According to the manufacturing method of the present invention, the ceramic powder is firstly uniformly applied onto the surface of the magnetic metal powder by using the wet powder mixing process, and dried to obtain the ceramic-metal composite powder, which is then uniformly mixed with the noble metal powder by using the dry powder mixing process, and finally the ceramic-metal composite powder is made into the compact target by using a molding and compacting process. The manufacturing method of the present invention can uniformly mix the powders of the magnetic metal, the ceramic, and the noble metal, and reduce the loss of the noble metal powder in the production process of the target, so as to improve the quality of the target and decrease the production cost thereof.
While the embodiments of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications that maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 097122747 | Jun 2008 | TW | national |
