JPH03291396A - Ni-fe alloy plating method - Google Patents

Abstract

PURPOSE:To uniformize the compsn. of a plating film at the flat parts of a stepped body to be plated and the inclined part between the flat parts by continuously varying current density at the flat parts within a specified range when the stepped body is electroplated with an Ni-Fe alloy. CONSTITUTION:A surface-stepped body 12 to be plated is immersed in an Ni Fe alloy plating soln. 10, a holder 11 supporting the body 12 is connected to the negative electrode of a power source 15 and a counter electrode 13 to the positive electrode. A function generator 14 for continuously varying electric current is set before the power source 15. On a curve which shows the Fe contents (%) Fe3-Fe6 of a plating film corresponding to current densities I1-I6 at the time of electroplating the body 12 with an Ni-Fe alloy, current density at the flat parts A, C is continuously varied from I4 at which the Fe content becomes max. to I6 which is higher than 14 with the function generator 14. An Ni-Fe alloy plating film 20 having the same compsn. at the inclined part B and the flat parts A, B can be formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plating method using a Ni--Fe alloy, and more particularly to a method for plating a Ni--Fe alloy that functions as a magnetic film.

Previously, this type of Ni-Fe alloy plating method was used to form a Ni-Fe alloy plating film with a uniform component ratio on an object such as a magnetic recording head. It was getting worse.

In general, the magnetic properties of Ni--Fe alloy plating films used as magnetic thin films are greatly influenced by the difference in alloy composition. Possible factors that influence the alloy composition of the Ni-Fe alloy plating film include the plating method, plating bath, and plating conditions. For example, in electroplating such as constant current plating and pulse plating performed by pulsing the plating current, it is known that the characteristics of the plated film differ between constant current plating and pulse plating, even if the same plating bath is used. There is. And like this, Ni −F
Among the factors that influence the alloy composition of the e-alloy plating film, the plating current density has a particularly large influence.

FIG. 9 shows a cross section of an object to be plated and a plated film plated with a Ni--Fe alloy. 2 in the diagram
0 is a Ni-Fe alloy plating film formed by electroplating, and the plated object 21 to which this Ni-Fe alloy plating film 20 has been applied has a surface with steps including a flat part A, an inclined part B, and a flat part C. have.

Figure 10 shows the relationship between plating current density and Fe weight composition in the Ni-Fe alloy plating film.
This is a current density curve.

As shown in this figure, increasing the plating current density results in
The Fe weight composition in the Ni-Fe alloy plating film increases, and at a certain plating current density 1) 0, the Fe weight composition reaches its maximum value Fe+
It becomes o.

When Ni-Fe alloy plating is applied to the plated object 21 having a stepped surface, a deviation occurs in the Ni-Fe alloy composition at the sloped portion B, and this can lead to poor magnetic properties, especially in elements with fine patterns. This is a major cause of the below. In order to obtain a magnetic thin film by Ni-Fe alloy plating with uniform magnetic properties, it is sufficient to reduce variations in alloy composition by reducing variations in plating current density. The plating current density is 1 in FIG. 10 at the point where the Fe weight composition changes the least, that is, near the maximum value of the Fe weight composition.

) was selected for electroplating (Unexamined Japanese Patent Publication No. 1983-
However, in this method, when electroplating is performed on the plated object 21 having a stepped surface as shown in FIG. As shown in Figures 1 and 1), the flat parts A and C are flat. Therefore, in the sloped part B, I ++ becomes, and the plating current density in the sloped part B becomes smaller than that in the flat parts A and C. In other words, due to the difference Δ in plating current density between flat areas A and C and sloped area B, the Fe weight composition in flat areas A and C becomes Fe+. In the inclined part C, it becomes Fe++, and the Fe weight composition changes by Δ between the two.
A deviation of Fe, . . . will occur. Therefore, flat parts A and C
In order to reduce the difference in the Fe weight composition between the flat areas A and C, as shown in FIGS. (I+a in Figure 10) Higher current density I
A method has been proposed in which electroplating is carried out by setting the plating current density at the inclined portion B to a value I +4, which is smaller than the current density that gives the maximum value of the Fe weight composition, and which is shifted by Δt (Japanese Patent Application Laid-Open No. 1-180994). Publication No.).

In the conventional plating method using Ni-Fe alloy mentioned above,
As shown in FIG. 12, although it is possible to obtain approximately the same amount of Fe+4 at the plating current density in the flat areas A and C and the slope area B, the plating current density from the flat areas A or C to the slope area B is In the transition region, the current density peak Fe shown in FIG. There was a problem that a difference in Fe weight composition between the part B and the part B was unavoidable.

The present invention has been made in view of the above-mentioned problems, and it is possible to prevent microscopic compositional fluctuations of the Ni-Fe alloy between flat parts and sloped parts for an object to be plated having a stepped surface. Ni for forming a uniform Ni-Fe alloy plating film
-It is an object of the present invention to provide a method for plating a Fe alloy.

To solve the problem 1″7 In order to achieve the above-mentioned purpose, the Ni-F according to the present invention
The method for plating e-alloy is to set the current density at the flat part of an object to be plated with a stepped surface to the current density that gives the maximum value of the Fe weight composition in the Fe weight composition-current density curve, and the current density from the current density. It is also characterized by performing plating while continuously changing the current density between large current densities.

■ Figure 3 shows the Fe weight composition vs. current density curve when a Ni-Fe alloy plating film is formed by electroplating on a plated object having a stepped surface as shown in Figure 9. .

In the figure, ■4 is the plating current density at which the Fe weight composition becomes the maximum value, and using this plating current density ■4, the flat areas A and C
When electroplating is performed, Ni
-The weight composition of Fe in the Fe alloy plating film is Fe in the inclined portion B, and is smaller than that in the flat portions A and C.

On the other hand, the plating current density was changed from the above (4) to the flat areas A and C.
When electroplating is performed with the current density difference between the current density and the slope part B being +6, which is larger than 61, Ni-Fe is deposited as shown in Figure 5.
The weight composition of Fe in the alloy plating film is higher in the inclined portion B than in the flat portions A and C. That is, when the plating current density of flat areas A and C is set to a current density I4 that gives the maximum value of Fe weight composition, and when it is set to a current density I6 that is larger than the current density, the Ni-Fe alloy plating film is The weight composition of Fe in the flat portions A and C and the inclined portion B are reversed.

Therefore, the plating current density for flat areas A and C was changed from 14 to 1.
By performing plating by continuously changing the plating current density to
-The weight composition of Fe in the Fe alloy plating film changes, and the Ni-Fe alloy composition in the Ni-Fe alloy plating film as a whole disappears and becomes homogenized6! FIG. 2 is a block diagram schematically showing a plating apparatus used in the Ni-Fe alloy plating method according to this embodiment.

In the figure, 1) is an object to be plated having a stepped surface placed in a plating bath 10, and this object 1) is connected to a power source 15.
connected to the cathode side of the Further, in the plating bath 10, an electrode 13 is provided facing the object to be plated 1) and connected to the anode side of the power source 15, and each electrode 1). 13 is
It is connected to a power source 15 via a function generator 14 for continuously changing the current density.

Hereinafter, a plating method according to an embodiment of the present invention will be explained based on the drawings.

In a method of plating a body 21 to be plated having a stepped surface as shown in FIG.

In order to eliminate the difference in the Ni-Fe alloy composition in the Ni-Fe alloy plating film 20 and to make it homogeneous, the current density is continuously changed.

That is, in FIG. 3, the range ΔI° of the continuously changing current density in the flat parts A and C is expressed as the difference ΔI° in the current density.
Plating is carried out by changing the current density between current density 4 and current density I6, which is the maximum value of the Fe weight composition. In this way, between the current density I4, which is the maximum value of the Fe weight composition, and the current density 16, which is larger than ΔI, which is the difference in current density between the flatter parts A and C and the slope part B, If set to change continuously, the Fe weight composition in the plating film 20 will change in the flat areas A, C and the inclined area B.
Both of them change continuously between Fe< and Fee, that is, they change continuously between the states shown in FIGS. 4 and 5, and the flat parts A and C of alloy plating M2O and the slope The magnitude of the composition change in part B becomes equal, and the formed plating film 2
The alloy composition of the entire 0 becomes uniform.

At this time, as shown in FIGS. 6 to 8, the same effect can be obtained even if the current density is changed continuously in a linear triangular wave, sine wave, or trapezoidal wave. Furthermore, the frequency of the current that is continuously changed is set to several m5.
The same effect can be obtained even if the time is varied within the range of ec to several tens of seconds. Particularly when the level difference is 100 μm or less, the uniformity effect of this method is significant.

Moreover, as shown in FIG. 1, if plating is performed with the setting Δ■=Δ■°, Fe4 and Fes in FIGS. 4 and 5 become equal, and Fe3 and F
e6 are made equal, and a plated film 20 whose composition is further made uniform can be obtained.

As is clear from the above explanations of Mitsuyoshi and Kari, the Ni-
In the plating method using an Fe alloy, when plating a plated object having a stepped surface, the current density in the flat part is changed to the Fe weight composition-current density curve.
By performing plating while continuously changing the current density between the current density that gives the maximum value of the weight composition and the current density larger than the current density, the alloy composition on the flat part and the slope part becomes uniform, and the magnetic properties are improved. A uniform Ni-Fe alloy plating film can be obtained.

[Brief explanation of drawings]

Figure 1 shows the Fe weight composition-current density curve when the continuously changing current density is set equal to the difference in current density between the flat part and the slope part in the Ni-Fe alloy plating method according to the present invention. The figure is a schematic configuration diagram showing a plating apparatus used when carrying out a plating method according to an embodiment of the present invention.
The figure shows the Fe weight composition-current density curve, which explains how plating is performed by changing the current density in the flat area between the maximum value of the Fe weight composition and the current density that is larger than the maximum value. Figure 5 is a cross-sectional view of the plated body and the plated film when the plated film is formed by setting the current density in the flat part to the current density that gives the maximum value of Fe weight composition. Cross-sectional views of the plated object and the plated film when the plated film is formed at a current density higher than the current density at which the maximum value of the weight composition is obtained. Figures 6 to 8 show the current density that is continuously changed. -Time curve, Figure 9 shows Ni-
A cross-sectional view of an object to be plated and a plated film having a stepped surface subjected to Fe alloy plating. Weight composition-current density curve, 1st)
The figure shows a cross-sectional view of the plated object and the plating film when the plating film is applied under the conditions shown in Fig. 10. In Fig. 12, the plating current density in the flat area is set to a current density higher than the maximum value of the Fe weight composition. Fe weight composition-current density curve showing the case where plating is performed. FIG. 13 is a cross-sectional view of the body to be plated and the plating film when the plating film is applied under the conditions shown in FIG. 12. 20... Plating film 21... Patent for plated body Applicant: Sumitomo Metal Industries, Ltd. Agent: Patent attorney Ryuji Iuchi Figure 1 Figure 2 Figure 6 Figure 8 Figure 9 Figure 7 Figure ↓N ＋＃Invalid/Fet amount known blow (0m) Figure 10 Figure 12 (mA/Crrl' J Figure 1, 1

Claims (1)

[Claims] (1) In a plating method in which a plated object having a stepped surface is plated with a Ni-Fe alloy, the current density at a flat part is determined by the current that gives the maximum value of the Fe weight composition in the Fe weight composition-current density curve. A plating method using a Ni-Fe alloy, characterized in that plating is performed while continuously changing the density and a current density higher than the current density.