JP2738080B2 - Plating solution bath equipment - Google Patents

Description

The present invention relates to a plating bath construction apparatus for forming an alloy plating film or the like used for a magnetic core of a thin film magnetic head, and streamlines the construction bath operation. A plating bath that easily deteriorates is quickly formed, the characteristics of the product are made uniform, the surface of the plating film is smoothed, the life of the plating solution is extended, and the cost is reduced.

[Conventional technology]

As shown in FIG. 3, the thin-film magnetic head has an insulating layer in which a lower core 14 is formed on a substrate 10 having a lower protective layer 12 attached thereto, and a coil conductor 20 is accommodated on the lower core 14 via a gap layer 16. 18 is formed, an upper core 22 is formed thereon, and a protective layer 24 for protecting and stabilizing the head is further formed thereon.

In this thin-film magnetic head, the magnetic cores 14, 22 are made of an alloy plating film. The magnetic properties of this plated film are that the magnetic film has a high magnetic permeability for reproduction efficiency, the saturation magnetic flux density BS is large for improving the writing ability on a high coercive force medium, and the core adheres during reproduction. It is desired that the coercive force HC of the magnetic film is small so that magnetic noise is hardly generated.

For example, a binary alloy of iron and nickel (permalloy) is used to satisfy such conditions.

In addition, if the surface of the plating film is rough, the anisotropy is disturbed, the magnetic properties are deteriorated, and the protection film formed on the plating film causes abnormalities and poor adhesion, so that the plating film surface is smooth. It is desirable.

In order to obtain a plating film having desired magnetic properties, it is necessary that the concentration of a plating chemical in a plating bath be accurately controlled. Further, in order to obtain a smooth plating film surface, it is necessary that impurities in the plating bath be small.

In the bathing process of the plating bath, generally, the plating chemicals are dissolved in pure water, the organic impurities contained in the plating solution are absorbed and removed by activated carbon, and the solid impurities contained in the plating solution and generated in the bath. The removal is performed by filtering out insoluble impurities (Fe ²⁺ → Fe ³⁺ ) and the like.

Conventionally, each of these steps is performed in a discontinuous batch process by a separate and independent apparatus, and a liquid after one step is placed in a container and transferred to the apparatus of the next step.

[Problems to be solved by the invention]

In alloy plating containing iron used in thin-film magnetic heads, Fe ²⁺ ions in the plating bath are easily oxidized and precipitated as insoluble trivalent iron hydroxide, which becomes impurities in the plating solution and causes plating. It causes the film surface to be rough. Also, Fe
Oxidation of ²⁺ ions reduces the iron ion concentration in the bath effective for plating, and changes in the composition ratio of alloy metal ions in the plating bath cause a large change in the plating film composition of the product, resulting in the desired magnetic properties. No longer available. For this reason, it is required that the bath for the plating bath be performed in as short a time as possible.

However, it was not possible to build a bath in a short time with the above-described conventional bath processing by batch processing. Therefore, it is difficult to make the characteristics of the product uniform and it is difficult to smooth the surface of the plating film. In addition, since the building bath requires a long time, the amount of insoluble iron hydroxide increases, and the life that can be used as a plating solution is short. In addition, since it takes a long time to build the bath, it is difficult to keep the initial concentration of the plating solution at a predetermined value due to fluctuations in various conditions during that time. For this reason, in the past, since the plating bath with the optimum concentration was selected from those prepared at various concentrations and used, the others had to be discarded,
This was a cost increase factor.

The present invention solves the drawbacks of the prior art, rationalizes the construction bath work, enables quick creation of a plating bath that is easily deteriorated, and makes the characteristics of the product uniform and the surface of the plating film smooth. It is an object of the present invention to provide a plating bath apparatus which realizes the above-mentioned conditions, prolongs the life of the plating solution, and realizes cost reduction.

[Means for solving the problem]

The present invention relates to a plating chemical dissolving tank for removably containing a corrosion-resistant colander-like container for accommodating activated carbon, a suction filtering device in which a plating solution is sent from the plating chemical dissolving tank through a pipe by a pump, and a suction filtering device. And a receiver through which the plating solution filtered through is supplied through a pipe.

(Operation)

According to the present invention, a plating solution is prepared by dissolving a plating agent in a plating agent dissolving tank, and then activated carbon is contained in a corrosion-resistant colander-shaped container in the plating agent dissolving tank to remove organic impurities. The plating solution from which the organic impurities have been removed is sent through a pipe to a suction filtration device by a pump to remove solid impurities, and the filtered plating solution is supplied to the receiver through the pipe.

According to this, since the dissolution of the plating chemical, the removal of the organic impurities, and the suction filtration are successively performed, the plating bath can be constructed in a short time under a constant condition and history.
Therefore, the oxidation of the metal ion component in the plating bath in the building bath can be minimized, and the characteristics of the product can be made uniform and the surface of the plating film can be smoothed. Also, since the bath can be built in a short time, it is easy to maintain the initial concentration of the plating solution at a predetermined value, it is easy to manage the plating solution, and it is possible to make full use of the optimal use conditions of plating, and to extend the life of the plating solution. Extend. In addition, since it is not necessary to discard those not having a predetermined initial concentration as in the related art, the cost can be reduced.

〔Example〕

One embodiment of the present invention is shown in FIG. The construction bath (plating chemical dissolution tank) 30 is composed of a cylindrical container made of corrosion-resistant metal,
The upper part is open. A heater 32 is installed in the built bathtub 30. In addition, a stirring blade 34 is freely inserted from above to stir the plating solution 38 by driving a stirring motor 36.

A corrugated container 25 made of a corrosion-resistant wire mesh for accommodating activated carbon, for example, as shown in FIG. The colander-shaped container 25 forms a frame with a support stay 26 and a circular band 27, and a metal mesh 28 made of stainless steel or the like is attached to the bottom surface and the peripheral surface to form a cylindrical shape slightly smaller than the building bathtub 30.
The circular band 27 is provided with a fixing bracket 29 and a handle 31 (which can be laid down so as not to be obstructed at the time of use) so as not to move in the bathtub 30 when stirred.
The colander container 25 contains, for example, granular activated carbon having a particle size of about 4 mm (a wire mesh is 2-3 times larger than the mesh of the particles). When powdered activated carbon is used, the amount of activated carbon used can be reduced to 1/3 to 1/5, but the filter for suction filtration is severely clogged and the filtration operation takes time. On the other hand, by removing the large activated carbon with the wire mesh of the monkey-like container 25, the activated carbon particles applied to the filter are reduced, and the filtration time is also reduced.

A pipe 40 is attached to the bottom of the building bathtub 30 and a pipe 42 is provided.
Is led to a filtrate drain 44 via a construction tub drain cock 42. In addition, the pipe 42 is guided from the construction bath drain cock 42 through a pipe 46, a liquid feed pump 48, and a pipe 50 to an outlet 54 to which a stop cock 52 is attached.

A suction filtration device 56 is provided below the outlet 54. The outlet of the suction filtration device is connected to the manifold 58. A pipe 60 is connected to the outlet of the manifold 58, and the pipe 60 is connected to a pipe 64 via a filtrate drain cock 62. The pipe 64 has a rear end guided to a filtrate drain 65 and a front end connected via a cock 66. Into the receiver flask 68. The upper space in the receiver flask 68 is connected to a vacuum suction pipe 72 via a cock 70, and the pipe 72 is connected to a three-way cock 74.
The lower end of the pipe 76 is connected to a suction bottle 78
Guided inside. The inside of the suction bottle 78 is connected to a suction pump 82 via a pipe 80.

A pipe 84 is connected to the bottom surface of the receiver flask 68, and the pipe 84 is connected to a liquid supply drain cock 86 via a liquid supply drain cock.
Guided to 88. Also, the pipe 84 is a liquid supply drain cock.
It is connected to a pipe 90 via 86, and is led to a plating apparatus storage tank via a liquid supply pump 92 and a pipe 94.

Next, an example of using the plating solution bath apparatus of FIG. 1 will be described. Here, a plating solution for 81 wt% nickel-permalloy plating with zero magnetostriction is prepared as permalloy plating for a thin film magnetic head. By using the 81 nickel composition, the magnetic permeability of the plating film can be easily realized at μ = 3000 or more, and the coercive force can be easily achieved at HC = 0.1 or less.

Table 1 shows an example of a plating bath for producing such an 81 permalloy plating film.

The relationship between the bath concentration of nickel ion (Ni ²⁺ ) and iron ion (Fe ²⁺ ) and the components in the plating film has the following stoichiometric equilibrium (nickel ion and iron are based on the principle of partial equilibrium). Equilibrium conditions shall be applied to electrolytic deposition and dissolution of ions.)

Here, α is an equilibrium constant. In this case, when α is larger than 1, the molecule indicates that components are easily precipitated, that is, nickel is easily precipitated (when α is smaller than 1, Conversely, this indicates that iron is easily precipitated.)

When α in the plating bath composition shown in Table 1 is obtained from this equation, α is 0.123, which indicates that this bath is a bath in which iron is easily deposited. As described above, in a bath in which iron easily precipitates, a change in iron ions appears very sensitively in the plating film. Therefore, iron ion concentration control becomes important. However, since divalent iron ions are easily oxidized, the concentration of divalent ions in the plating solution that is effective for plating tends to fluctuate. In particular, when the liquid temperature exceeds 50 ° C., oxidation of iron divalent ions proceeds rapidly. Therefore, if it takes a long time to prepare the bath, the iron ion concentration in the plating bath is far from the predetermined concentration, and the magnetic properties are deteriorated due to the fluctuation of the plating film composition.

According to an experiment, it is necessary to maintain the magnetic film for a thin film head at 79 to 83% -Ni in order to maintain stable characteristics. Allowable concentration of iron ions at this time, it is necessary to fit from the first equation to _{FeSO 4 · 7H 2 O = 9.68g} / ~9.75g / range.

When the melting temperature is maintained at 40 to 50 ° C., the oxidation of FeSO ₄ .7H ₂ O can be performed at about 0.1 to 0.2 g // hr. Therefore, it is desirable to finish the construction bath in about 1 to 2 hours in order to keep the iron ion concentration within the predetermined range. The plating solution after the filtration step can suppress iron oxidation with a suitable reducing agent. Therefore, it is considered that iron oxidation at the time of building bath is the factor which gives the most variation in plating solution due to oxidation of plating bath.

 The procedure for establishing the plating bath will be described.

1) Pour about 20 pure water into the building bath 30 and heat it with the heater 32 to raise the temperature (the colander 25 and the stirring blades 34 are also put in advance).

2) Of the plating chemicals, putting inorganic salt chemicals that do not adsorb to activated carbon _{(NiSO 4 · 6H 2 O,} NiCl 2 · 6H 2 O, the H ₃ BO ₃₎ in pure water heated with active carbon, the stirring blade 34 Turn to dissolve.

3) After the inorganic salt chemicals are completely dissolved, keep the temperature at 50-60 ° C for 30 minutes.
The activated carbon is stirred for more than one minute to adsorb organic impurities contained in the plating chemical (particularly in nickel sulfate).

4) Pull up the granular activated carbon together with the colander 25.
At this time, the powdered activated carbon partially crushed during the chemical dissolution remains about 1/20 to 1/30 of the initial charge.

5) After the temperature of the solution has been lowered to 45 ° C. or lower, FeSO ₄ .7H ₂ O is added (at 50 ° C. or higher, the oxidation rate sharply increases). Ascorbic acid is also added to prevent oxidation, followed by stirring.

6) When the chemicals have completely dissolved, drain the cock
42, Open the stop cock 52, drive the liquid feed pump 48, and put the solution in the bathtub 30 → pipe 40 → cock 42 → pipe 46 → liquid feed pump 48 → pipe 50 → stop cup 52 → discharge port 54 → suction filtration. Feed to device 56.

7) By operating the suction pump 82, the three-way cock 74 and the cocks 66 and 70 of the receiver flask 68 are set on the suction side, the supply drain cock 86 is stopped, and the solution supplied to the suction filtration device 56 is filtered. , Solid impurities (powdered activated carbon,
Insoluble solids contained in plating chemicals, iron hydroxide solids generated in a building bath, etc.) are removed. At this time, stirring is performed.

The powdered activated carbon in the building tub 30 is substantially uniformly dispersed by the stirring of the building tub 30. Therefore, by sending this solution directly to the suction filtration device 56 by the pump 48, the activated carbon can be guided to the suction filtration device 56 without precipitating (this solution was moved by replacement or the like as in a conventional batch process). In this case, the powdered activated carbon precipitates during standing still or sticks in the apparatus due to stagnation, which takes a great deal of time to clean the apparatus.)

Although a part of ascorbic acid is adsorbed on the powdered activated carbon, the amount of ascorbic acid is small compared to the activated carbon removed in the colander vessel 25. Yes (ascorbic acid concentration is 0.5wt% ~
If it is in the range of 1.0 wt%, there is no influence on plating conditions, plating composition, and the like. ).

8) The filtered solution stays in the receiver flask 68.

9) When all the solutions in the building bath 30 have been filtered, the three-way cock 74 is opened, and the inside of the receiver flask 68 is returned to the atmospheric pressure.
The liquid supply drain cock 84 is opened to the liquid suction pump 92 side, and the liquid supply pump 92 is moved to transfer the solution to the storage tank of the plating apparatus, so that the plating operation can be started immediately.

Since sodium saccharinate and sodium dodecyl sulfate are adsorbed by activated carbon, they are added to the plating solution in the receiver flask 68 or the storage tank.

10) Immediately after the transfer of the solution, wash the equipment. For cleaning, set all cocks 42, 52, 62, 66, 86 on the suction side, supply pure water into the construction bath 30 with a hose, wash well, and at the same time, operate the liquid supply pump 48 and the liquid supply pump 92, The inside of the system is washed to remove the plating solution remaining in the system.

11) When the inside of the system has been sufficiently replaced with pure water, stop the supply of pure water and drain each drain cock 42, 62, 86 to drain 44, 6
Open to the 5,88 side, and drain the final drain in the system.

By using the apparatus shown in FIG. 1 described above, the speed of preparing a magnetic alloy plating solution for a thin film magnetic head was greatly increased. According to the experiment, the conventional batch processing took 7 hours and 15 minutes from the start of the bath to the end of the washing, but the apparatus of FIG. 1 took 1 hour and 55 minutes.

In addition, since it is created in a short time under a constant condition and history, fluctuations of oxidatively altered components (iron divalent ions) in the alloy are suppressed, the initial concentration of the plating solution is maintained at a predetermined value, and the plating solution Management became easy, and the optimal use conditions for plating were fully utilized (by gradually lowering the bath temperature from 47 to 40 degrees C., a stable plated film having almost the same characteristics and appearance can be produced. ). As a result, the life of the plating solution was prolonged, and the number of plating treatments could be increased by a factor of two to three times as compared with the conventional bath bath.

In addition, since the initial concentration of plating can be maintained at a predetermined value, the amount of decrease in iron ions is measured in advance according to the heating time of the bath, the history of use, and the like. The film composition can be kept approximately constant by a technique such as adding ions as they are consumed, or by bringing the conditions under which iron ions are easily precipitated, and the accuracy is easily obtained.

In addition, it is not necessary to wash each step individually, and pure water may be flowed in the same system as the building bath. This is very easy, and the washing time is shortened.

[Modification example]

In the above embodiment, the present invention has been described in connection with the case where a plating solution for forming a magnetic core of a thin film head is prepared. However, the present invention can also be used for preparing a plating solution for other uses.

〔The invention's effect〕

As described above, according to the present invention, the dissolution of the plating chemical, the removal of the organic impurities, and the suction filtration are continuously performed, so that the plating bath can be constructed in a short time under a constant condition and history. . Therefore, the oxidation of the metal ion component in the plating bath in the building bath can be minimized, and the characteristics of the product can be made uniform and the surface of the plating film can be smoothed. Also, since the bath can be built in a short time, it is easy to maintain the initial concentration of the plating solution at a predetermined value, it is easy to manage the plating solution, and it is possible to make full use of the optimal use conditions of plating, and to extend the life of the plating solution. Extend. In addition, since it is not necessary to discard those not having a predetermined initial concentration as in the related art, the cost can be reduced. Further, cleaning after use is also easy.

[Brief description of the drawings]

FIG. 1 is a system diagram showing one embodiment of the present invention. FIG. 2 is a perspective view showing an example of a corrosion-resistant colander-shaped container. FIG. 3 is a sectional view showing the configuration of the thin-film magnetic head. 25: Corrosion-resistant wire mesh container, 30: Construction bath (plating chemical dissolution tank), 40, 46, 50, 60, 64, 90, 94 ... Piping, 56: Suction filtration device, 68: Receiver Flask (receiver).

Claims (1)

(57) [Claims] 1. A plating chemical dissolving tank for removably containing a corrosion-resistant colander-like container for accommodating activated carbon, a suction filtration device in which a plating solution is sent from the plating chemical dissolving tank through a pipe by a pump, And a receiver for supplying a plating solution filtered by the apparatus through a pipe.