JP3033455B2 - Electroless nickel plating of aluminum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for electroless nickel plating of aluminum which can be effectively employed particularly for electroless nickel plating on aluminum or aluminum alloy substrates for magnetic disks.

[0002]

2. Description of the Related Art Conventionally, in the production of a hard disk, an electroless process using hypophosphorous acid or a salt thereof as a reducing agent as a base plating on an aluminum or aluminum alloy substrate (Al or Al alloy substrate). A nickel plating film (hereinafter, referred to as an electroless Ni-P film or simply a Ni-P film) is formed. As a process of forming the Ni-P film, an Al or Al alloy substrate is machined. Thereafter, the following steps (1) degreasing (2) washing with water (3) etching (4) washing with water (5) immersion in an aqueous nitric acid solution (6) washing with water (7) zinc replacement (8) washing with water (9) hypophosphorous acid or Usually, electroless nickel plating using the salt as a reducing agent is employed.

After forming the Ni-P film in this manner, the surface is mirror-polished to form a magnetic film, then an appropriate protective film is formed, and if necessary, a lubricating layer is formed. A hard disk (magnetic disk) is obtained.

[0004] In this case, particularly in the production of a hard disk, the zinc substitution treatment is repeatedly performed twice, and in this case, the steps after (5) are as follows.

(5) -1 Immersion in primary nitric acid aqueous solution (6) -1 Rinsing in water (7) -1 First zinc substitution (8) -1 Rinsing in water (5) -2 Immersion in secondary nitric acid aqueous solution (6) -2 Rinse (7) -2 Second zinc substitution (8) -2 Rinse (9) Electroless nickel plating One example of the process of this double zinc substitution method is ASTM B-25.
3-87, "Standardization Guide for Pretreatment of Plating on Aluminum Alloys", section 6, displacement deposition / strike processing. Therefore, the recommended zinc substitution treatment time is 45 seconds for the first zinc substitution and 30 seconds for the second zinc substitution (Section 6.4.1), and is characterized in that the second zinc substitution treatment time is short. This is because the zinc-substituted treatment solution is highly alkaline and highly corrosive to Al or Al alloy, and does not want to prolong the immersion time more than necessary.

Incidentally, when the Al or Al alloy substrate is zinc-substituted (zincate treatment) and then subjected to electroless nickel plating, the Ni-P film is blistered (blistered) due to aging of the electroless nickel plating solution. ) Occurs. If blisters occur like this, it is necessary to discard the previously used electroless nickel plating solution and replace it with a new plating solution to perform plating. No blisters occur.

An electroless nickel plating solution containing hypophosphorous acid or a salt thereof as a reducing agent is mainly composed of a water-soluble nickel salt, a complexing agent thereof, and a hypophosphorous acid / salt as a reducing agent. As the plating proceeds, the nickel ions and the reducing agent in the solution are consumed and their concentrations decrease, and the pH decreases. For this reason, it is a general practice to replenish the water-soluble nickel salt (nickel ion) and the reducing agent, adjust the pH, and continue the plating. Since phosphoric acid / salt is oxidized to phosphorous acid / salt, phosphorous acid / salt accumulates and increases in the plating solution, and phosphorous acid / salt in the plating solution accumulates in a certain amount or more. In such a case, the characteristics of the Ni-P film are reduced or the plating rate is reduced. Therefore, the plating solution must be discarded and replaced with a new plating solution. Normally, the life of the electroless nickel plating solution (the time of disposal and replacement of the plating solution) is approximately 6 to 7 times the replenishment equivalent to the nickel ion concentration in the initial plating solution. (Hereinafter, this is expressed as the life of the electroless nickel plating solution is about 6 to 7 MTO). That is, the usual electroless nickel plating solution is 6
It is discarded after ＭＴ7 MTO and replaced with a new solution.

However, in the case of electroless nickel plating after double zinc substitution of the magnetic disk, blisters are generated in the Ni-P film by using about 3MTO, and therefore, about half of ordinary electroless nickel plating solution. At present, the plating solution must be discarded at the end of its life and replaced with a new plating solution. This is because when Al or Al alloy pre-treated by the double zinc substitution method is electroless nickel plated, zinc attached to Al or Al alloy elutes into the plating solution, and this zinc ion acts as an impurity. It was thought that the plating solution would be spoiled, but in any case, when the Al or Al alloy substrate was subjected to the zinc substitution treatment and the electroless nickel plating was performed, Since the life of the electroless nickel plating solution becomes extremely shorter than the life, improvement of this point has been desired.

The present invention has been made in view of the above circumstances,
An object of the present invention is to provide a method for electroless nickel plating of aluminum which can extend the life of an electroless nickel plating solution.

[0010]

The present inventors have made intensive studies to achieve the above object, and as a result, after pre-treating Al or an Al alloy material by the above-mentioned double zinc substitution method, electroless nickel was obtained. It has been found that by performing plating, in which case the second zinc substitution treatment time is longer than the first zinc substitution treatment time, the life of the electroless nickel plating solution can be significantly extended. That is, conventionally, generally, the first
The zinc replacement time is in the range of 30 to 50 seconds, the second zinc replacement time is in the range of 10 to 30 seconds, and the second zinc replacement time is shorter than the first zinc replacement time. . However, in particular, the first zinc substitution treatment time is 1 to 4
0 second, the second zinc substitution time is in the range of 30 to 100 seconds, and when the second zinc substitution treatment is performed longer than the first zinc substitution treatment as described above, the conventional method surprisingly requires about 3 MTO.
It was found that the life of the electroless nickel plating solution was increased to about 6 MTO or more, and the life was doubled or more.

The reason why the life of the electroless nickel plating solution can be extended by taking the second zinc substitution treatment longer than that of the first zinc substitution treatment is because of the fact that the conventional electroless nickel plating solution has a short life. It is currently unknown, as it may change the idea that zinc impurities were present.
In any case, when the electroless nickel plating is performed after the zinc substitution, it is considered that the shortening of the life of the electroless nickel plating solution is almost fatal. It is an unexpected new finding that the life of the electroless nickel plating solution could be significantly prolonged simply by making the time longer than the first zinc substitution treatment time.

Hereinafter, the present invention will be described in more detail. In the method of electroless nickel plating of aluminum according to the present invention, 1 to 5 mol / l of sodium hydroxide and 0.1 to 0 mol of zinc oxide are added to aluminum or an aluminum alloy material. .4
The zinc-substituted solution containing mol / l is immersed at a temperature of 15 to 30 ° C. to perform a first zinc-substitution treatment, and then, after pickling, 1 to 5 mol / l of sodium hydroxide and 0.1 to 0.1 mol of zinc oxide. 0.
Electroless nickel plating solution using hypophosphorous acid or hypophosphite as a reducing agent after dipping in a zinc substitution solution containing 4 mol / l at a temperature of 15 to 30 ° C. to perform a second zinc substitution treatment In the method of electroless nickel plating of aluminum, wherein the first zinc substitution time is 10 to 40 seconds, the second zinc substitution time is 30 to 100 seconds, and The method is characterized in that the zinc replacement treatment time is longer than the first zinc replacement treatment time by 5 seconds or more.

The present invention is described in detail in the following. (1) Degreasing (2) Rinsing with water (3) Etching (4) Rinsing with water (5) -1 Immersion in primary nitric acid aqueous solution (6) -1 Rinsing with water 7) -1 First zinc substitution (8) -1 Rinse (5) -2 Immersion in a second nitric acid aqueous solution (6) -2 Rinse (7) -2 Second zinc substitution (8) -2 Rinse (9) ) When treating Al or Al alloy in the process of electroless nickel plating, (7)
The second zinc substitution treatment time of (7) -2 is longer than the first zinc substitution treatment time of -1.

In this case, the method of the present invention is suitably employed particularly for the manufacture of a magnetic disk, and Al and Al alloy materials conventionally used for magnetic disks can be used as Al and Al alloy. .

Here, (1), (3), (5) -1, 2
Steps (9) and (9) can be performed by a conventional method.

For example, as the degreasing of (1), immersion or electrolytic degreasing using a normal alkaline degreasing solution for aluminum can be adopted, and as the etching treatment of (3), an alkaline or acidic aqueous solution is used. , 1-1
A method of immersion treatment at 60 to 75 ° C. for 1 to 15 minutes using an alkali hydroxide solution of about 0% by weight or an aqueous acid solution of about 1 to 20% by volume, for example, a mixed aqueous solution of sulfuric acid and phosphoric acid, can be adopted. As the immersion treatment with the aqueous nitric acid solution (5), a method of using a concentrated aqueous nitric acid solution of 200 to 700 ml / l and immersing at 15 to 35 ° C. for 30 seconds to 2 minutes can be adopted. Hydrofluoric acid or the like may be mixed with the nitric acid aqueous solution as needed. The immersion in the first and second nitric acid aqueous solutions can be performed under the same conditions.

In the zinc replacement treatment, a zinc replacement solution having a conventionally used composition can be used as it is. In addition to zinc containing a metal component, the zinc replacement solution further contains iron, nickel, and the like. A metal salt such as copper may be contained. Specifically, as the zinc-substituted solution, sodium hydroxide is used at 1 to 5 mol / l, more preferably 2.5 to 4 mol / l, and still more preferably 3 to 3.8 mol / l. 0.1 to 0.4 mol / l, more preferably 0.15 to 0.35 mol / l, and still more preferably 0.2 to 0.3 mol / l;
One or two or more of nickel and copper salts are used in an amount of 4 to 10 mmol / l, and a complexing agent such as sodium tartrate is used in an amount of 0.02 to 0.3
Those containing mol / l can be used. In this case, the first zinc-substituted liquid and the second zinc-substituted liquid usually have the same composition, but may of course have different compositions.

The conditions for the zinc substitution may be the same as usual except for the processing time.
And more preferably at 20 to 23 ° C.

Thus, in the present invention, the second zinc substitution treatment is performed for a longer time than the first zinc substitution treatment. In this case, the first zinc substitution treatment time is 10 to 40.
Second, more preferably 15 to 25 seconds, and the second zinc substitution treatment is preferably 30 to 100 seconds, more preferably 35 to 60 seconds, and still more preferably 35 to 50 seconds. Further, the time of the second zinc substitution treatment is preferably at least 5 seconds, more preferably at least 10 seconds longer than the time of the first zinc substitution treatment.

Further, the electroless nickel plating is also carried out with a nickel complexing agent (usually 20 g / l) such as a water-soluble nickel salt (usually 4 to 7 g / l as Ni), an organic acid salt, an ammonium salt and an amine.
-80 g / l) and a known plating bath and plating conditions using a hypophosphite such as hypophosphorous acid or sodium hypophosphite (usually 20 to 40 g / l) as a reducing agent. Can be done. In this case, the plating bath may be an acidic bath or an alkaline bath, for example, those having a pH of 4 to 10 can be used. In the production of hard disks,
It is preferable to form a Ni-P film having a phosphorus content of 9 to 13% (% by weight, the same applies hereinafter) by using an acidic electroless nickel plating bath having a pH of 4 to 6 to a thickness of about 5 to 30 μm.

As described above, the concentration of nickel ions and hypophosphorous acid / salt decreases with the progress of plating, and the pH of the electroless nickel plating solution also decreases. In the present invention, the second zinc replacement treatment time is made longer than the first zinc replacement treatment time, so that the plating life, which was about 3 MTO conventionally, is more than doubled to 6 MTO.
The length can be extended as described above, and the life can be almost equal to the life of a normal electroless nickel plating solution.

[0022]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[Examples and Comparative Examples] As an electroless nickel plating solution, the one having the following composition was used in 6.5 MTO, and each component and pH were adjusted according to the following composition. The various aluminum plates shown were subjected to electroless nickel plating in the following steps (5 samples).
Table 1 shows the results of the generation of blisters (swelling) on the obtained Ni-P coating.

Electroless nickel plating solution Nickel sulfate 0.1 mol / l Sodium malate 0.2 ナ ト リ ウ ム Sodium acetate 0.2 ナ ト リ ウ ム Sodium hypophosphite 0.2 鉛 Lead nitrate 1.0 ppm pH 4.7 Plating step (1) Degreasing: 50 ° C., 5 minutes Sodium carbonate 0.2 mol / l Sodium phosphate 0.05 {sodium borate 0.2} Surfactant 5 g / l pH 9.0 (2) Rinsing: room temperature, 30 seconds (3) Etching: 70 ° C., 2 minutes Sulfuric acid 1 mol / l phosphoric acid 0.5〃 (4) Washing: room temperature, 30 seconds (5) -1 Immersion of first nitric acid aqueous solution: 25 ° C., 30 seconds concentrated nitric acid 500 ml / l (6) -1 Washing: room temperature, 30 seconds (7) -1 First zinc substitution: 20 ° C., time is as shown in Table 1, sodium hydroxide 3.0 mol / l zinc oxide 0.25% Ferric chloride 0.007〃 tartar Sodium 0.1 ナ ト リ ウ ム Sodium nitrate 0.01 〃 (8) -1 Rinse with water: room temperature, 30 seconds (5) -2 Immersion in secondary nitric acid aqueous solution: 25 ° C., 60 seconds Same composition as (5) -1 (6)- 2 Rinsing: room temperature, 30 seconds (7) -2 Secondary zinc substitution: 20 ° C., time is the same as (7) -1 as shown in Table 1. (8) -2 Rinsing: room temperature, 30 seconds (9) None Electrolytic nickel plating: 90 ° C, 90 minutes, bath ratio about 1 dm ² / l

[0025]

[Table 1]

From the results shown in Table 1, it can be seen that the time for the second zinc substitution treatment is longer than the time for the first zinc substitution treatment, especially the first zinc substitution treatment.
It has been found that the zinc substitution treatment is preferably performed for about 15 seconds to 30 seconds, and the second zinc substitution treatment is preferably performed for a longer time period of 30 seconds or more.

Similar results were obtained when a commercially available electroless nickel plating solution was used. In addition, the obtained N
As a result of measuring the amount of magnetization after heat treating the i-P film at 290 ° C. for 2 hours, the value in each case was 2 Gauss or less. However, if the second zinc substitution treatment is performed for more than 60 seconds, the amount of magnetization after the heat treatment increases, so that it is recognized that it is effective to perform the treatment for 60 seconds or less in the manufacture of a magnetic disk. Was.

[0028]

According to the present invention, the electroless nickel plating solution was conventionally discarded at about 3 MTO in the magnetic disk industry, but by changing the time of the zinc substitution treatment in the pretreatment step, it can be reduced to 6 MTO or more. Now available. For this reason, it is possible to significantly reduce not only the cost required for discarding the plating solution but also the opportunity loss caused by stopping the equipment for the discarding operation. It also helps to reduce the amount of industrial waste.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideyuki Takami 1-5-1 Exit, Hirakata City, Osaka Prefecture Uemura Industry Co., Ltd. Central Research Laboratory (72) Inventor Ikuo Nakayama 1-5-1 Exit, Hirakata City, Osaka Prefecture Uemura Industrial Co., Ltd. Central Research Laboratory (56) References JP-A-54-84835 (JP, A) JP-A-62-7873 (JP, A) JP-A-63-259082 (JP, A) JP-A-63-63 293170 (JP, A) JP-A-3-10085 (JP, A) JP-A-4-36474 (JP, A) JP-A-5-51756 (JP, A) JP-A-5-230664 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) C23C 18/31-18/52

Claims (2)

(57) [Claims] 1. An aluminum or aluminum alloy material containing 1 to 5 mol / l of sodium hydroxide and 0.1 to 0.5 mol of zinc oxide.
15 to 30 ° C in a zinc-substituted solution containing 1 to 0.4 mol / l
The first zinc substitution treatment is carried out by immersion at a temperature of 5 ° C., followed by pickling, followed by 15 minutes in a zinc substitution liquid containing 1 to 5 mol / l of sodium hydroxide and 0.1 to 0.4 mol / l of zinc oxide. ~ 3
After immersion at a temperature of 0 ° C. to perform the second zinc substitution treatment,
In the electroless nickel plating method for aluminum in which electroless nickel plating is performed by immersion in an electroless nickel plating solution using hypophosphorous acid or hypophosphite as a reducing agent, the first zinc substitution treatment time is 10 to 40. Electroless nickel of aluminum, wherein the second zinc substitution treatment time is set to 30 to 100 seconds and the second zinc substitution treatment time is set to 5 seconds or more longer than the first zinc substitution treatment time. Plating method. 2. The method according to claim 1, wherein the aluminum or aluminum alloy material is an aluminum or aluminum alloy substrate for manufacturing a magnetic disk.