JPS6235477B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an electroless plating bath for producing magnetic storage media (magnetic films) used in magnetic recording bodies such as magnetic disks and magnetic tapes. In recent years, as high-density magnetic recording bodies, storage media such as plated magnetic disks and plated magnetic tapes, which are manufactured by a plating method, have begun to be used. A magnetic recording device consists of the main components of a recording/reproducing head and a recording medium, and the performance of the head used and the characteristics of the storage medium are determined by the required recording density, recording/reproducing speed, etc. When the same head is used, the recording density and output are determined by the film thickness (δ) of the storage medium and the coercive force (Hc) and residual magnetic flux density (Br) as magnetic properties, and have the following relationship. (Recording density)∝(Hc/Br・δ) ^1/2 (1) (Output)∝(Br・δ・Hc) ^1/2 (2) Therefore, a magnetic film suitable for the required recording density and output must be selected. In order to obtain this, it is necessary to maintain the magnetic properties and film thickness of the magnetic film within a certain allowable range. However, when producing a magnetic film using an electroless plating method, it is not easy to change the magnetic properties of the magnetic film obtained from an electroless plating bath prepared with a certain composition. In the case of electroplating, the magnetic properties obtained can be easily changed by changing the current density, but in the case of electroless plating, the plating conditions such as bath pH and bath temperature must be changed significantly. These operations are often accompanied by a reduction in bath life and workability, which poses practical problems. Therefore, in order to obtain a magnetic film with the desired magnetic properties, a separate electroless plating bath must be developed depending on the properties. The purpose of the present invention is to improve these problems and provide an electroless plating bath in which magnetic properties can be controlled by adding tungsten ions to the electroless plating bath to obtain a magnetic film having desired properties. There is a particular thing. The electroless plating bath according to the present invention contains cobalt ions or cobalt ions and nickel ions, a reducing agent for these metal ions, a PH buffer, a PH regulating agent, and a malonic acid group as a complexing agent for the metal ions. The method is characterized by adding tungstate ions to an aqueous solution, whereby the magnetic properties are controlled and a magnetic film having the desired properties can be obtained. Cobalt ions or nickel ions used as metal ions in the present invention include:
It is provided by dissolving a soluble salt of cobalt or nickel, such as sulfate, chloride, or acetate, in an electroless plating bath. The concentration of cobalt ions used is in the range of 0.01 to 2 mol/, preferably in the range of 0.03 to 0.2 mol/. When the plating bath contains cobalt ions and nickel ions, the total concentration of cobalt ions and nickel ions is in the range of 0.01 to 1.5 mol/, preferably in the range of 0.03 to 0.15 mol/, and the cobalt concentration is /Nickel concentration value starts from 100
Used in the range of 0.3. Hypophosphites are commonly used as reducing agents, but hydrazine salts, borohydrides, and the like can also be used. Ammonium salts, carbonates, organic acid salts, etc. are used as pH buffering agents, and pH buffers range from 0.01 to
Concentrations in the range of 2 mol/l are used. As PH regulators, alkalis such as ammonia and sodium hydroxide are used to raise the PH, and acids such as sulfuric acid and hydrochloric acid are used to lower the PH. The malonic acid groups as complexing agent are provided by malonic acid or soluble salts of malonic acid, and concentrations in the range from 0.1 to 2.5 mol/l are used. Gluconic acid groups are provided by gluconic acid or soluble salts of gluconic acid, and concentrations in the range 0.01-1.0 mol/are used. Tungstate ions are supplied by soluble salts of tungstate, including 6 tungstate ions such as sodium tungstate (Na ₂ WO ₄ 2H ₂ O) and potassium tungstate (K ₂ WO ₄ ), which exist stably in solution. Preferred are tungstates of high valence. Hereinafter, the features of the electroless plating bath according to the present invention will be explained using examples. Example 1 A copper substrate that had been degreased with ethanol and washed with water was subjected to activation treatment and acceleration treatment under the following conditions.
A Co-W-p film (500 Å thick) was formed. Activation treatment conditions HS101B (manufactured by Hitachi Chemical) 60 c.c./1, hydrochloric acid 320
cc/, pure water 620c.c./ in active liquid composition.
Soak for minutes. Acceleration treatment conditions ADP201 (manufactured by Hitachi Chemical) 200 c.c./, pure water 800
cc/ for 3 minutes. Plating bath composition Cobalt sulfate 0.10mol / Sodium hypophosphite 0.20mol / Ammonium sulfate 0.50mol / Sodium malonate 0.90mol / Gluconic acid 0.50mol / Sodium tungstate 0 to 0.10mol / Plating conditions Plating bath PH9.0 (PH adjustment with NH ₄ OH at room temperature) Plating bath temperature 85℃ Concentration of sodium tungstate from 0
Figure 1 shows the results of investigating the effect on Hc by varying it up to 0.10 mol/. In FIG. 1, the horizontal axis represents the sodium tungstate concentration, and the vertical axis represents the Hc of the plated magnetic film. Hc was 520 Oe when sodium tungstate was not added, but it became approximately 350 Oe when the sodium tungstate concentration was 0.01 mol/or higher. By adding sodium tungstate to the plating bath, the Hc value obtained could be reduced by more than 150 oersteds. In addition, in order to clarify the crystal structure of these Co-W-p films whose magnetic properties change depending on the sodium tungstate concentration, a sample of several μm suitable for X-ray diffraction was used.
The results of examining the X-ray diffraction intensity using a sample with a film thickness of m are shown in the following table.

【table】

[Table] Sodium tungstate concentration from 0
It can be seen that as the amount increases to 0.10 mol/, the C axis (axis of easy magnetization) of the α-Cc hexagonal crystal gradually changes from the in-plane direction to the perpendicular direction with respect to the substrate.
The perpendicular magnetization recording method, which uses a magnetic recording medium with an axis of easy magnetization perpendicular to the film surface and is magnetized perpendicular to the film surface, is different from the recording method using horizontal magnetization used in conventional magnetic disk drives. It is stated in Japanese Unexamined Patent Publication No. 134706/1989 that it is superior in high-density recording compared to the conventional magnetic film, but the magnetic film obtained from the soaking bath in which the sodium tungstate concentration is increased according to this example is superior to perpendicular magnetization recording. It can be used for magnetic recording media. Example 2 A Co-Ni-W-P film (film thickness:
500 Å) was formed. Plating bath composition Cobalt sulfate 0.08mol / Nickel sulfate 0.02mol / Sodium hypophosphite 0.20mol / Ammonium sulfate 0.50mol / Sodium malonate 0.90mol / Gluconic acid 0.50mol / Sodium tungstate 0 to 0.10mol / Plating conditions Plating Bath PH9.0 (PH adjusted with NH ₄ OH at room temperature) Plating bath temperature 85℃ Concentration of sodium tungstate from 0
Figure 2 shows the results of investigating the effect on Hc by varying it up to 0.10 mol/. Hc without adding sodium tungstate is 660 oersted, but if the sodium tungstate concentration is
At 0.01 mnl/, Hc reached a maximum value of 690 oersted, and at higher concentrations it decreased to 510 oersted at a sodium tungstate concentration of 0.10 mol/. By adding sodium tungstate to the plating bath, the obtained Hc value could be changed. In this example, even if the concentration of sodium tungstate was increased, the crystal structure did not change, and the axis of easy magnetization showed in-plane orientation. As described above in Examples 1 and 2, according to the present invention, cobalt ions, cobalt ions and nickel ions, reducing agents for these metal ions, PH buffers, PH regulators, and complexes of the metal ions are used. By adding tungstate ions to an aqueous solution containing malonate and gluconic acid groups as a curing agent, magnetic properties can be controlled and a magnetic film having desired properties can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between iron ion concentration and Hc in the plating bath of Example 1, and FIG. 2 is a diagram showing a similar relationship in the plating bath of Example 2.

Claims (1)

[Claims] 1 Cobalt ion, or cobalt ion and nickel ion, reducing agent for these metal ions,
An electroless plating bath characterized in that tungstate ions are added to an aqueous solution containing a PH buffer, a PH regulator, and malonic acid groups and gluconic acid groups as complexing agents for the metal ions.