JP2012021178A - Method for manufacturing electroless nickel plating film, and substrate for magnetic recording medium using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a flaw-free electroless nickel plating film.SOLUTION: The method for manufacturing an electroless nickel plating film includes the steps of: forming an aluminum layer having a purity of 99.99% or more and a film thickness of 2.5 μm or more on a substrate by using a sputtering; and forming the electroless nickel plating film on the aluminum layer by using an electroless plating. The method may further include a step of forming a titanium layer having a purity of 99.99% or more between the substrate and the aluminum layer.

Description

  The present invention relates to a method for producing an electroless nickel plating film that is defect-free and requires high corrosion resistance. More specifically, the present invention is useful in the field of using an aluminum substrate having a defect-free and highly corrosion-resistant nickel plating film. For example, the present invention is useful in the manufacture of a magnetic recording medium substrate mounted on various magnetic recording devices including an external storage device of a computer.

  The base material for a magnetic recording medium is required to have high nonmagnetic characteristics that do not become a noise source of magnetic recording. Further, the surface of the base material is required to have high hardness that can withstand sliding or impact with the magnetic head. In view of the above points, the base material for magnetic recording media is generally made of aluminum, and the surface thereof is usually electroless nickel plated with a thickness of 5 to 20 μm.

  In addition, in the magnetic recording device, the magnetic recording medium is rotated at a high speed of 10,000 rpm and scanned with a magnetic head floated to a height of several nanometers on the surface of the medium, thereby enabling high density recording and high speed access. Both are compatible. In order to achieve this characteristic, the surface of the base material for magnetic recording media is required to minimize defects that cause recording omission as well as high flatness (average surface roughness Ra of 1 nm or less).

  It is known that the plane orientation of the aluminum underlayer is preferably (111) in forming the electroless nickel plating film. In order to improve the uniformity of the film thickness of the electroless nickel plating film formed on the aluminum underlayer, a method of dividing the aluminum underlayer into two upper and lower layers with different material layers has been proposed (Patent Literature). 1). In this proposal, the continuity of the aluminum underlayer is cut off by the different material layer, and the upper aluminum layer is formed at a low substrate temperature, thereby reducing the upper layer aluminum crystal grains, and the crystal grains other than (111) orientation. Each area is made smaller. Then, the nickel plating film grown on the (111) -oriented crystal grains existing in the surrounding area covers the crystal grains other than the (111) -oriented crystal grains, thereby forming a nickel plating film having a uniform film thickness. In this proposal, although it is considered to reduce the area of each crystal grain, no consideration has been given to the total area of the portion other than the (111) orientation through the entire aluminum underlayer.

JP 2008-028079 A

  In order to maintain high reliability of the magnetic recording medium, it is required that the aforementioned defects do not increase even when exposed to an aluminum corrosive gas (for example, a chlorine-based gas and a nitric acid-based gas). For example, when there is a defect penetrating to the aluminum underlayer in the electroless nickel plating film of the magnetic recording medium housed in the magnetic recording device, when the aluminum corrosive gas enters the magnetic recording device, the aluminum corrosive gas May reach the aluminum underlayer and cause corrosion (corrosion) of the aluminum underlayer. The occurrence of corrosion may make the magnetic recording medium unusable. Therefore, there is a strong demand for defect-free electroless nickel plating films.

  The inventor has found that in forming the electroless nickel plating film, the aluminum layer serving as the underlayer is formed of aluminum having a purity of 99.99% or more, thereby improving the (111) orientation of the aluminum layer, The present invention has been reached.

  By adopting the configuration of the present invention, it is possible to form a defect-free high corrosion-resistant electroless nickel plating film by forming a high-purity aluminum layer on the substrate. Further, by forming a laminated film of a high-purity titanium layer and a high-purity aluminum layer on the substrate, it becomes possible to more stably form a defect-free high corrosion resistance electroless nickel plating film.

It is a figure which shows one structural example of the electroless nickel plating film | membrane laminated body formed with the method of this invention. It is a figure which shows another structural example of the electroless nickel plating film | membrane laminated body formed with the method of this invention. It is a graph which shows the relationship between the average particle diameter of the crystal grain in the aluminum layer which is a base layer for forming an electroless nickel plating film, and orientation.

  Conventionally, nickel plating is formed by directly performing electroless plating on the surface of an aluminum substrate. In the present invention, as shown in FIG. 1, a high purity aluminum layer 30 is formed on a substrate 10, and an electroless nickel plating film 40 is formed thereon by electroless plating. Alternatively, as shown in FIG. 2, a high-purity titanium layer 20 and a high-purity aluminum layer 30 are sequentially formed on the substrate 10, and an electroless nickel plating film 40 is formed thereon by electroless plating. To do. It is possible to form a film-forming surface (surface on which electroless plating is performed) having sufficient orientation even with a single high-purity aluminum layer 30. However, by interposing the high-purity titanium layer 20, the influence of the substrate 10 is completely cut off, and the film-forming surface, that is, the surface of the high-purity aluminum layer 30 is stably made a highly oriented surface. It becomes possible.

  The substrate 10 in the present invention is formed of a nonmagnetic material, preferably aluminum or an aluminum alloy (Ag—Mg, etc.). The substrate 10 in the present invention may be, for example, a disk made of aluminum or an aluminum alloy for a magnetic recording medium, or may be an automobile wheel made of aluminum or an aluminum alloy.

  The high-purity aluminum layer 30 in the present invention is formed of aluminum having a purity of 99.99% or more, preferably 99.999% or more. The aluminum layer 30 can be formed using a sputtering method or a vapor deposition method. Preferably, the aluminum layer 30 is formed by sputtering. This is because, by increasing the energy with which aluminum atoms collide with the substrate to be deposited, the adhesion force is increased, the orientation is improved, and the film thickness is uniform when depositing a large area. This is because the effects such as can be achieved. When the aluminum layer 30 is formed by the sputtering method, the above-described high purity can be achieved by using an aluminum target material having a purity of 99.99% or more, preferably 99.999% or more. Although not intended to be bound by any theory, it is believed that the improvement in orientation due to the improvement in the purity of aluminum is obtained by the following mechanism. When the purity of the aluminum layer 30 is improved, the impurity concentration that inhibits crystal growth decreases, so that the crystal grain size in the aluminum layer 30 increases. Aluminum deposited on the substrate 10 (with a natural oxide film of aluminum formed on the surface) or the titanium layer 20 is preferentially oriented in the <111> direction to form crystal grains having a plane orientation (111). . However, crystal grains in other directions (for example, <100>, <110>, etc.) and other plane orientations are generated with a small probability. However, the crystal grains of other plane orientations are smaller in size than crystal grains having the plane orientation (111). Therefore, as the crystal grain size increases, crystal grains having other plane orientations are swallowed by crystal grains having a large grain size (111), and in the surface orientation (111) on the surface of the aluminum layer 30. The oriented region is enlarged and the orientation is improved.

  Considering the film thickness reduction due to the pretreatment etching of the electroless nickel plating and the variation at the time of manufacture, the aluminum layer 30 at the time of formation has a film thickness of 2.5 μm or more, preferably 3 μm or more. In the present invention, generally, as the film thickness of the aluminum layer 30 increases, the average grain size of the crystal grains in the aluminum layer 30 increases and the orientation improves. On the other hand, from the viewpoint of manufacturing cost and mass productivity, it is desirable that the film thickness of the aluminum layer 30 be the minimum necessary. The aluminum layer 30 has a thickness of 2.5 μm to 10 μm, preferably 3 μm to 6 μm.

  In the present invention, the high purity aluminum layer 30 is formed by forming a film-forming base material (the base material 10 or a laminate of the base material 10 and the high purity titanium layer 20), preferably 180 ° C. or higher and 420 ° C. or lower. It is preferable to carry out by heating to a temperature of 300 ° C. or higher and 400 ° C. or lower. This is because by raising the temperature of the substrate to be deposited, the average grain size of the crystal grains of the aluminum layer 30 is increased, and thereby the orientation of the aluminum layer 30 is improved. In FIG. 3, the aluminum layer 30 which has various film thickness in various film forming base-material temperatures is formed, and the correlation with the average particle diameter and orientation of the crystal grain of the aluminum layer 30 is shown. The orientation was evaluated based on the ratio of the area of crystal grains separated from the (111) crystal plane by 15 ° or more (based on the surface area of the aluminum layer). Thus, smaller numbers indicate better orientation. As can be seen from FIG. 3, the orientation of the aluminum layer 30 is improved with an increase in the average grain size of the crystal grains. In the present invention, the orientation in the aluminum layer, that is, the ratio of the area of crystal grains deviated by 15 ° or more from the (111) crystal plane is preferably 15% or less, preferably 5% or less.

  When the high purity titanium layer 20 is interposed between the base material 10 and the aluminum layer 30 as shown in FIG. 2, the high purity titanium layer 20 is 99.99% or more, preferably 99.999% or more. Made of pure titanium. The titanium layer 20 can be formed using a sputtering method or a vapor deposition method. Preferably, the titanium layer 20 is formed by sputtering. Because, by increasing the energy with which titanium atoms collide with the substrate to be deposited, the adhesion force is increased, the orientation is improved, and the uniformity of the film thickness is increased when depositing a large area. This is because the effects such as can be achieved. When the titanium layer 20 is formed by the sputtering method, the above-described high purity can be achieved by using a titanium target material having a purity of 99.99% or more, preferably 99.999% or more.

  The titanium layer 20 has a thickness of 0.01 μm or more and 0.15 μm or less, preferably 0.02 μm or more and 0.05 μm or less. When the titanium layer 20 having a thickness of 0.01 μm or more is formed, the influence of the substrate 10 on the orientation of the aluminum layer 30 can be eliminated. Furthermore, when the thickness of the titanium layer 20 is 0.02 μm or more, the orientation of the titanium layer 20 itself can be stably improved. The improvement in the orientation of the titanium layer 20 makes it possible to achieve a highly oriented state of the aluminum layer 30 formed thereon. Further, by setting the upper limit of the thickness of the titanium layer as described above, excellent mass productivity and low manufacturing cost can be achieved.

  The electroless nickel plating film 40 in the present invention is a film that contains nickel as a main component and may contain additives such as phosphorus, molybdenum, and tungsten. The additive content in the electroless nickel plating film 40 is preferably 10% by mass or less and 14% by mass or less, more preferably 12% by mass or more and 13% by mass or less, based on the total mass of the film. The electroless nickel plating film 40 in the present invention is formed by electroless nickel plating using conventional materials and methods. Prior to the formation of the electroless nickel plating film 40, an initial reaction layer such as cleaning of the surface of the aluminum layer 30 to be a film forming surface, acid etching, and / or displacement zinc plating (zincate) may be performed. .

  When acid etching is performed before the formation of the electroless nickel plating film 40, the film thickness of the aluminum layer 30 is reduced by about 1 μm. Therefore, the film thickness of the aluminum layer 30 after acid etching is 1.0 μm or more, more preferably 1.5 μm or more and 8.5 μm or less, and more preferably 2 μm or more and 5 μm or less. By having the film thickness as described above, it is possible to prevent the acid etching solution from reaching the underlying titanium layer 20 and the base material 10 due to non-uniformity of acid etching.

  The electroless nickel plating film 40 formed according to the present invention has few defects such as pinholes, and can protect the underlying substrate 10 from corrosion even when placed in a corrosive environment. . Therefore, the base material coated with the electroless nickel plating film 40 manufactured according to the present invention is useful as a magnetic recording medium substrate for manufacturing a highly reliable magnetic recording medium.

  Alternatively, the nickel plating film formed according to the present invention is also useful in an automobile wheel. An automobile aluminum wheel is generally an electroless nickel plating film or an electroless nickel plating on an aluminum substrate. A film / electric nickel plating film / electrochrome plating film is formed. When pinholes exist in the electroless nickel plating film, chlorine ions contained in calcium chloride or the like sprayed on the road surface as a snow melting agent in the winter significantly corrode the aluminum base material of the wheel, and significant pitting corrosion occurs. However, since the electroless nickel plating film formed by the present invention has few defects such as pinholes, it is possible to suppress the occurrence of pitting corrosion as described above.

Example 1
This example is an example of manufacturing an electroless nickel plating film laminate having the structure shown in FIG.
An Al—Mg alloy base material 10 having an annular shape with an outer diameter of 95 mm, an inner diameter of 25 mm, and a plate thickness of 1.75 mm was prepared. The substrate 10 was subjected to alkali cleaning and acid etching to clean its surface.

  Next, an aluminum layer 30 having a thickness of 2.5 μm was formed by sputtering using an aluminum target having a purity of 99.99% or higher. At this time, the film forming power was 10 kW, and the temperature of the substrate 10 was 300 ° C. A 200 μm square region on the surface of the obtained aluminum layer 30 was analyzed using backscattered electron diffraction (EBSD), and the ratio of the area where crystal grains deviated by 15 ° or more from the (111) orientation were obtained. . The obtained ratio was shown as “orientation” in Table 1 below.

  Subsequently, the surface of the aluminum layer 30 was cleaned by alkali cleaning and acid etching. Next, a zincate film was formed on the aluminum layer 30 as an initial reaction layer of electroless Ni—P plating.

  Subsequently, an electroless Ni—P plating film 40 containing 12.2% phosphorus and having a thickness of 7 μm was formed using an electroless nickel plating solution Nimden-HDX (manufactured by Uemura Kogyo). The obtained electroless Ni—P plating film 40 was roughly polished using an alumina slurry having an average particle diameter of 800 nm and a polishing pad made of urethane foam. The processing thickness of the rough polishing was set to 2 μm. Subsequently, finish polishing was performed using a colloidal silica having a particle diameter of 20 to 200 nm and a polishing pad made of urethane foam. The processing thickness of the finish polishing was set to 0.2 μm. Further, the surface of the electroless Ni-P plating film 40 is thoroughly rubbed with an alkali cleaner and a PVA sponge, rinsed sufficiently with deionized water having a resistivity of 18 MΩ · cm or more, and abrasive grains Then, chips and other adhered foreign matters were removed to obtain a magnetic recording medium substrate.

  Using a surface defect analyzer OSA (Optical Spectrum Analyzer), the number of pit defects having a diameter of 200 nm or more is measured over the entire electroless Ni-P plating film 40 on one surface of the obtained magnetic recording medium substrate. did. Here, when the number of pit defects is 10 or less, “◎”, when 25 or less, “◯”, when 50 or less, “Δ”, when 51 or more, or more Was determined as “×”. The results are shown in Table 1.

(Examples 2 to 5)
The procedure of Example 1 was repeated except that the film thickness of the aluminum layer 30 was changed to obtain a magnetic recording medium substrate. Table 1 shows the film thickness and orientation of the aluminum layer 30 and the number of pit defects on the magnetic recording medium substrate.

(Example 6)
The procedure of Example 1 was repeated except that an aluminum layer 30 having a film thickness of 3 μm was formed using an aluminum target having a purity of 99.999% or more to obtain a magnetic recording medium substrate. Table 1 shows the orientation of the aluminum layer 30 and the number of pit defects in the magnetic recording medium substrate.

(Comparative Example 1)
The procedure of Example 1 was repeated except that the aluminum layer 30 was not formed to obtain a magnetic recording medium substrate. Table 1 shows the number of pit defects in the magnetic recording medium substrate.

(Comparative Example 2)
The procedure of Example 1 was repeated except that the film thickness of the aluminum layer 30 was 2 μm to obtain a magnetic recording medium substrate. Table 1 shows the orientation of the aluminum layer 30 and the number of pit defects in the magnetic recording medium substrate.

(Example 6)
The procedure of Example 6 was repeated except that an aluminum target having a purity of 99.9% or more was used to obtain a magnetic recording medium substrate. Table 1 shows the orientation of the aluminum layer 30 and the number of pit defects in the magnetic recording medium substrate.

  In comparison between Comparative Example 1 and Examples 1 to 5, by forming the aluminum layer 30 having a purity of 99.99% or more on the base material 10, an aluminum layer 30 having excellent orientation is obtained. It turns out that the pit defect of the electroless nickel plating film | membrane (Ni-P film | membrane) formed on it can be reduced significantly. Further, in the comparison between Comparative Example 2 and Examples 1 to 5, it is necessary to reduce the pit defects of the electroless nickel plating film by setting the film thickness when forming the aluminum layer 30 to 2.5 μm or more. I understand that. Further, from the comparison between Comparative Example 3 and Example 2 in which the film thickness of the aluminum layer 30 is equal, the purity of the aluminum layer 30 is 99.99% or more. It turns out that it is important to decrease. Further, from the comparison between Example 6 in which the purity of the aluminum layer 30 is 99.999% or more and Example 2, the pits of the electroless nickel plating film are more effectively improved by improving the purity of the aluminum layer 30. It can be seen that defects can be reduced.

(Example 7)
This example is an example of manufacturing an electroless nickel plating film laminate having the structure shown in FIG.
First, an AlMg alloy base material cleaned according to the procedure of Example 1 was prepared.

  Next, a 0.01 μm thick titanium layer 20 was formed by sputtering using a titanium target having a purity of 99.99% or higher. At this time, the film forming power was 10 kW, and the temperature of the substrate 10 was 300 ° C.

  Subsequently, an aluminum layer 30 having a film thickness of 2.5 μm and an electroless nickel plating film 40 were formed by the same procedure as in Example 1 to obtain a magnetic recording medium substrate. Evaluation similar to Example 1 was performed about the orientation of the aluminum layer 30, and the pit defect of the electroless nickel plating film. The results are shown in Table 2.

(Examples 8 to 11)
The procedure of Example 7 was repeated except that the thickness of the titanium layer 20 was changed to obtain a magnetic recording medium substrate. Table 2 shows the thickness of the titanium layer 20, the thickness and orientation of the aluminum layer 30, and the number of pit defects in the magnetic recording medium substrate.

(Example 12)
A titanium layer 20 having a thickness of 0.02 μm is formed using a titanium target having a purity of 99.999% or more, and an aluminum layer 30 having a thickness of 3 μm is formed using an aluminum target having a purity of 99.999% or more. Except for this, the procedure of Example 7 was repeated to obtain a magnetic recording medium substrate. Table 2 shows the thickness of the titanium layer 20, the orientation of the aluminum layer 30, and the number of pit defects in the magnetic recording medium substrate.

(Comparative Example 4)
The procedure of Example 7 was repeated except that the titanium layer 20 having a thickness of 0.02 μm was formed using a titanium target having a purity of 99.9% or more, and the aluminum layer 30 having a thickness of 3 μm was formed. A magnetic recording medium substrate was obtained. Table 2 shows the thickness of the titanium layer 20, the orientation of the aluminum layer 30, and the number of pit defects in the magnetic recording medium substrate.

  In the comparison between Comparative Example 1 and Examples 7 to 11, excellent orientation was achieved by forming a titanium layer 20 having a purity of 99.99% or more and an aluminum layer 30 having a purity of 99.99% or more on the substrate 10. It can be seen that the aluminum layer 30 having the properties can be obtained, and the pit defects of the electroless nickel plating film (Ni-P film) formed thereon can be remarkably reduced. Further, in the comparison between Example 1 and Examples 7 to 11, it is more effective to provide the titanium layer 20 having a purity of 99.99% or more than the single aluminum layer 30. It can be seen that pit defects are reduced. Further, it can be seen from the comparison between Comparative Example 4 and Example 8 that the purity of the titanium layer 20 is 99.99% or more, which is important for the reduction of pit defects in the electroless nickel plating film. Further, from the comparison between Example 12 in which the purity of the titanium layer 20 and the aluminum layer 30 is 99.999% or more and Example 8, it is more effective by improving the purity of the titanium layer 20 and the aluminum layer 30. It can be seen that pit defects in the electroless nickel plating film can be reduced.

  In addition, about Example 3 and Example 9, 10 samples were produced, respectively, and the above-mentioned evaluation was performed. In these examples, the average values are shown in Tables 1 and 2. In Example 9, in all ten samples, the orientation of the aluminum layer 30 (the ratio of the area deviated by 15 ° or more from the (111) orientation) is 5% or less, and the number of pit defects is 10 / face or less. Met. On the other hand, in Example 3, one sample showing the orientation of 18% of the aluminum layer 30 exceeding 15% was present in 10 samples. This sample had 39 pit defects / surface and was evaluated as “Δ”. This makes it possible for the combined use of the titanium layer 20 to completely eliminate the influence of the substrate 10 and stably produce the highly oriented aluminum layer 30 as compared with the case where only the aluminum layer 30 is used. As a result, it can be seen that the pit defects of the electroless nickel plating film can be stably reduced.

10 Substrate 20 Titanium layer 30 Aluminum layer 40 Electroless nickel plating film

Claims (20)

A step of forming an aluminum layer having a purity of 99.99% or more and a film thickness of 2.5 μm or more on a substrate using a sputtering method or a vapor deposition method;
And a step of forming an electroless nickel plating film on the aluminum layer by using electroless plating. Forming a titanium layer having a purity of 99.99% or more on a substrate;
Forming an aluminum layer having a purity of 99.99% or more and 2.5 μm or more on the titanium layer using a sputtering method or a vapor deposition method;
And a step of forming an electroless nickel plating film on the aluminum layer by using electroless plating.   The method for producing an electroless nickel plating film according to claim 2, wherein the titanium layer has a thickness of 0.01 µm or more and 0.15 µm or less.   The method for producing an electroless nickel plating film according to claim 3, wherein the titanium layer has a thickness of 0.02 µm or more and 0.05 µm or less.   The method for producing an electroless nickel plating film according to any one of claims 2 to 4, wherein the titanium layer has a purity of 99.999% or more.   The method for producing an electroless nickel plating film according to claim 1, wherein the aluminum layer has a thickness of 2.5 μm or more and 10 μm or less.   The method for producing an electroless nickel plating film according to claim 6, wherein the aluminum layer has a thickness of 3 μm or more and 6 μm or less.   The method for producing an electroless nickel plating film according to any one of claims 1 to 7, wherein the aluminum layer has a purity of 99.999% or more.   9. The aluminum layer according to claim 1, wherein a ratio of a crystal grain area deviated by 15 [deg.] Or more from a (111) crystal plane based on a surface area of the aluminum layer is 15% or less. The manufacturing method of the electroless nickel plating film | membrane of description.   10. The electroless device according to claim 9, wherein in the aluminum layer, a ratio of a crystal grain area deviated by 15 ° or more from a (111) crystal plane based on a surface area of the aluminum layer is 5% or less. Manufacturing method of nickel plating film.   A magnetic recording medium substrate comprising a base material, an aluminum layer having a purity of 99.99% or more and a film thickness of 1.0 μm or more, and an electroless nickel plating film formed on the aluminum layer by electroless plating .   The magnetic recording medium substrate according to claim 11, further comprising a titanium layer having a purity of 99.99% or more between the base material and the aluminum layer.   The magnetic recording medium substrate according to claim 12, wherein the titanium layer has a thickness of 0.01 μm or more and 0.15 μm or less.   The magnetic recording medium substrate according to claim 13, wherein the titanium layer has a thickness of 0.02 μm to 0.05 μm.   The magnetic recording medium substrate according to claim 11, wherein the aluminum layer has a thickness of 1.0 μm or more and 8.5 μm or less.   The magnetic recording medium substrate according to claim 15, wherein the aluminum layer has a thickness of 2 μm to 5 μm.   The magnetic recording medium substrate according to claim 11, wherein the aluminum layer has a purity of 99.999% or more.   18. The magnetic recording medium substrate according to claim 11, wherein the titanium layer has a purity of 99.999% or more.   19. The ratio of the crystal grain area deviated by 15 ° or more from the (111) crystal plane in the aluminum layer based on the surface area of the aluminum layer is 15% or less. 19. The substrate for magnetic recording media described in 1.   20. The magnetic recording according to claim 19, wherein a ratio of the area of crystal grains deviated by 15 [deg.] Or more from the (111) crystal plane in the aluminum layer based on the surface area of the aluminum layer is 5% or less. Medium substrate.

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