JPS63277771A - Plating method - Google Patents

Abstract

PURPOSE:To prevent the occurrence of defects such as pinholes and abnormal deposition by putting a plating soln. in an atmosphere under a lower pressure than atmospheric pressure before or during plating so as to easily separate bubbles of dissolved gas and gaseous hydrogen generated during plating. CONSTITUTION:When electroplating or electroless plating is carried out, a plating soln. in a plating tank is put in an atmosphere under a lower pressure than atmospheric pressure before or during plating. The diameter of bubbles of dissolved gas and gaseous hydrogen generated by a reaction is increased and the bubbles rise at an increased speed and are easily separated. Accordingly, the adhesion of gaseous hydrogen and dissolved gas to a member to be plated can be prevented and the occurrence of defects such as pinholes and the abnormal deposition of a plating metal can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plating method for applying nickel-phosphorus (N i -P) plating to, for example, an aluminum or aluminum alloy substrate.

[Prior Art] Conventionally, this type of plating method has been used, for example, as a plating process for forming an underlayer of a magnetic disk. This magnetic disk is a magnetic recording medium used for external memory of computers, etc.
It is formed by providing a non-magnetic underlayer and a recording magnetic layer.

The above-mentioned underlayer is added to increase the surface hardness of the magnetic disk, but the momentary contact between the surface of the magnetic disk and the magnetic head destroys the surface of the magnetic disk, making it impossible to record or read information. This is to prevent this from happening. This base layer is formed by coating the nickel alloy by performing electroless plating under atmospheric pressure.

[Problems that the invention seeks to solve] However, in this conventional coating method, hydrogen gas generated by the plating reaction and dissolved gas in the plating solution adhere to the surface of the plating layer, thereby causing damage to the plating layer. In some cases, surface defects such as pinholes are formed due to stopping of reaction in the parts, or protrusions are formed due to abnormal precipitation of plated metal.

When a magnetic disk with such surface defects is used, problems such as recording/reproducing failures and head crashes may occur.

[Means for Solving the Problems] The present invention, which has been made to solve the above-mentioned problems, is a plating method using electroplating or electroless plating, in which a large amount of plating solution is applied before or during plating. The gist of the present invention is a plating method characterized by being placed in an atmosphere with a pressure lower than atmospheric pressure.

[Effects] By placing the plating solution in an atmosphere with a pressure lower than atmospheric pressure before or during plating, hydrogen gas generated by the plating reaction and dissolved gas generated from the plating solution are reduced compared to normal pressure. The diameter of the bubbles increases. As a result, the rising power and speed of the hydrogen gas and dissolved gas increase, the bubbles are removed more easily, and the hydrogen gas and dissolved gas are removed more quickly than in the plating solution. Therefore, when electroplating or electroless plating is performed, hydrogen gas or dissolved gas in the plating solution becomes difficult to adhere to the plating surface, and as a result, the reaction at the attached part stops and pinholes are formed.
The occurrence of abnormal precipitation of plated metal and the formation of protrusions is reduced.

[Example] An example of the present invention will be described below with reference to the drawings. FIG. 1 shows the manufacturing process of a magnetic disk, and FIG. 2 shows a plating apparatus 1 that performs plating under reduced pressure.

First, kQ-Mg-based aluminum alloy (for example, JI
S standard: A-5086) material, plate thickness 1, 2m
A doughnut-shaped member 2 to be plated (see FIG. 2) having an outer diameter of 95 mm and an inner diameter of 25 mm is manufactured (Step 2).

Next, the member 2 to be plated is coated with a non-silica alkaline degreasing solution (Okuno Pharmaceutical Co., Ltd., product number: Alblep 204).
The temperature was set to 65°C, and soaked for 2 minutes and 30 seconds at night,
Perform non-etching alkaline degreasing treatment (Step ■). Subsequently, after performing a water washing treatment using ion-exchanged water, using a non-silica-based solution (Okuno Pharmaceutical Industries, product number: Alprep 230), it was immersed in the solution for 4 minutes at a temperature of 65 ° C. Aluminum oxide is removed by non-etching acidic degreasing treatment (Step ①).

Next, after washing with water, zinc replacement treatment is performed. 30. Zinc replacement treatment. A solution of Og/Q Na2Zn○2 is converted into NaO
Using a solution adjusted to pH 14.0 with H and heated to 25°C, the member to be plated 2 is immersed in this solution for 30 seconds (step ①).
).

The substitution reaction at this time is shown by the following formula.

3Na2ZnO2+2AQ+2820 →2NaAQ02+3Zn+4NaOHIn this process,
Zn is more electrically sensitive than AQ, and the AQ of the surface of the plated material is
At the same time as replacing and removing the 203 film, Zn in the solution is deposited on the surface of the member 2 to be plated.

Next, after washing with water, it was washed with 62% nitric acid solution at 25°C for 3
Dissolve and remove the zinc-substituted film by 0-second acid immersion treatment (Step V)
.

Subsequently, after washing with water again, a zinc replacement treatment is performed for 10 seconds using the same solution as the above-mentioned zinc replacement treatment (step (2)) (step (2)). This is because the zinc substitution treatment is performed again to make the substituted film more dense and to make the N1-P film to be formed later more dense.

Next, after washing with water, surface conditioning treatment is performed by immersing it in a weak alkaline solution containing 30 g/Q of sodium bicarbonate for 30 seconds.
Process ■). This means that the solution used for zinc replacement treatment has a pH of 1.
Since the pH is as high as 4, the pH is lowered and adjusted to match the pH of the plating solution.

Following the above step (step ①), the plate is washed with water again, and then electroless N1-P plating is performed under reduced pressure, that is, by placing the plating solution in an atmosphere with a pressure of 600 to 700 mmHg (step ①). In this process, the member 2 to be plated is immersed in N1-P plating solution 4 for several hours to form a N1-P film of about 15 um. The concentration components of the N1-P plating solution 4 are shown below, and it is used at a pH of 4.6 and at a solution temperature of 85°C.

NiSO4◆6H20...-13,OOg/QKNaC
aH40e・4H20...28.28g/QNaH2
PO2◆H20=-13,25g/QN840H(30
% aqueous solution) -.-70m Q/Q This electroless plating reaction is expressed by the following formula.

N i 2++ 82P 02-+ H20→N i+
82PO3-+28+ This reaction is an autocatalytic reaction of N1 using hypophosphorous acid as a reducing agent, and actively occurs in the presence of Ni. As a side reaction, P precipitates, and the N1-P film contains P.
-h″ Contains about 12% in SNi.

The above-mentioned plating process under reduced pressure is performed in a plating apparatus 1 as shown in FIG. In the figure, 5 is a plating tank, and this plating tank 5 is separated by a partition plate 6.7.
The first liquid chamber 8 and the second liquid chamber 9 communicate with each other at the upper part of the partition plate 6, and the second liquid chamber 9 and the third liquid chamber 9 communicate with each other at the upper part of the partition plate 6. It communicates with the liquid chamber 10 at the lower part of the partition plate 7.

A heater 11 is installed in the first liquid chamber 8, while a disk holding device 12 is housed in the second liquid chamber 9. Further, a filtration pump 13 is installed in the third liquid chamber 10.

The disk holding device 12 includes a support member 14 fixed to the plating tank 5, a rotating member 15 rotatably supported at the lower end of the supporting member 14, and a drive unit ( (not shown), etc., and the rotating member 1
A member 2 to be plated, which becomes a magnetic disk, is attached to the leading edge of the image 5.

A pump 16 is installed on the left side of the plating tank 5 as shown in the figure, and the plating liquid from the pump 16 is passed through a filtration device 17 and a pipe line 18.
through which the first liquid chamber 8 is supplied, and the third liquid chamber 1
At 0, the plating solution sucked by the filtration pump 13 is returned to the pump 16.

Then, the plating tank 5 equipped with the above-mentioned devices is covered and sealed with a wall 20, and the pressure is lowered with a vacuum pump 22 to perform electroless plating.

By using this equipment to perform electroless plating at a lower pressure, the diameter of the dissolved gas and hydrogen gas bubbles generated by the reaction becomes larger than at normal pressure, resulting in their rising power. This increases the rate of rise and the rate of rise, making it easier to remove bubbles. Therefore, it is possible to prevent hydrogen gas generated during the electroless coating reaction process and dissolved gases such as air and carbon dioxide in the plating solution from adhering to the plated member 2.
This can prevent the formation of pinholes and abnormal precipitation of plated metal.

The reason why it is preferable to perform the plating process at a pressure in the above range of 600 to 700 mmHg is that the plating solution is used after being heated, so below 600 mmHg, the amount of evaporation of the plating solution increases. This is because the concentration of the components of the plating solution tends to change, and furthermore, at 700 mmHg or more, the effect of pressure reduction is small.

Next, after washing with water and drying, the surface is subjected to a polishing stone treatment (Step ①), and then a non-etching alkaline degreasing treatment is performed (
Process X).

Next, after washing with water, the surface of the magnetic disk is activated (Step XI). This treatment is to remove the oxide film on the surface, and involves immersing it in 2N HCQ for 1 minute, washing with water, and then immersing it in IN H2SOJ for 1 minute.

Next, after washing with water again, electroless Co-P plating is performed to form a Co-P film as a magnetic layer (Step XII
). The moisture content of this Co-P plating solution is shown below, and the solution is adjusted to pH 10 with NaOH and used at a solution temperature of 80°C.

C03OA-7820---0.05mol/12KN
aczHaos -4H20-・-0,71mol
/QNaH2P02・N20...0.19
m01/Q(NH4)2S04 -~0.6
1mo L/Q Next, after washing with water again, a protective layer is formed using carbon in Step XI [), and a lubricating layer is further formed (Step XrV) to complete the magnetic disk.

In this embodiment, the plating solution was placed under reduced pressure during the plating process, but it may be placed under reduced pressure before the plating process. In that case, since the temperature of the plating solution has not increased due to heating, evaporation is less likely to occur, and the pressure may be set to 600 mmHg or less.

Furthermore, it can be used not only for electroless plating but also for electroplating using a plating solution.

[Effects of the Invention] As explained above, according to the present invention, in the plating processing method of electroplating or electroless plating, the plating solution is placed in an atmosphere of pressure lower than atmospheric pressure before or during plating. This allows the dissolved gas and hydrogen gas to bubble out more easily than under normal pressure. Therefore, these gases can be prevented from adhering to the surface of the plated member,
Therefore, it is possible to prevent the formation of surface defects in the plating film, such as the formation of pinholes and heterodense precipitation of the plating metal.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing a plating process for a magnetic disk according to an embodiment of the present invention, and FIG. 2 is an explanatory diagram showing an apparatus for plating under reduced pressure. 2... Part to be plated 5... Plating tank 22... Vacuum pump ■... Electroless plating process

Claims (1)

[Claims] A plating method for electroplating or electroless plating, which comprises placing a plating solution in an atmosphere with a pressure lower than atmospheric pressure before or during plating.