JPH06108259A - Production of amorphous ni-co-b alloy film - Google Patents

Abstract

PURPOSE:To allow an amorphous Ni-Co-B alloy film to show excellent characteristics as a soft magnetic thin film and a high resistance thin film by adding metal salt and a reducing agent to a plating bath to regulate it and incorporating boron, in a high concentration, into the immersed material to be plated while the decomposing-unstable state of the plating bath is evaded. CONSTITUTION:An amorphous alloy film is produced by an electroless plating method. As metal salt, nickel chloride and cobalt chloride in an optional ratio are added, and, as a reducing agent, a soln. of sodium borohydride is added to regulate the plating bath. The immersed material to be plated is incorporated with boron in a high conc., while the decomposing-unstable state of the plating bath is evaded by adding the soln. of sodium borohydride to the plating bath little by little under the conditions in which the electroless plating is most suitably executed, there by the amorphous Ni-Co-B alloy film is produced. As a stabilizer, lead salt is added to the plating bath. In this way, the alloy film excellent in solderability and, furthermore, small in the discoloration of the surface caused by heat can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for producing an amorphous alloy film by an electroless plating method.

[0002]

2. Description of the Related Art The electroless plating method can form a metal film on a non-conductive material, has good throwing power, and can obtain a very uniform coating film. In particular, the amorphous alloy film has (a) extremely high corrosion resistance, (b) high magnetic permeability, (c) excellent wear resistance, (d) high electrical resistance, and (e) high hardness of plating film. It is suitable for needs in the electronic material field where high performance and high reliability are required. However, on the other hand, the amorphous alloy film is thermally unstable because it is in a metastable state, and crystallization occurs due to the influence of heat (the crystallization temperature increases in proportion to the concentrations of phosphorus P and boron B).
The disadvantage is that the excellent characteristics are lost. Therefore, the problem regarding the thermal stability of the amorphous alloy film is important and has a deep relationship when considering the application and practical application of the amorphous alloy film. In other words, there is a demand for the development of a technique for producing an amorphous alloy film, which is superior in thermal stability to the conventional amorphous alloy film and can be provided with a function according to the application.

Amorphous alloy film technology by electroless plating, which is most commonly used in industry at present, is the Kanigen plating method using hypophosphorous acid as a reducing agent, which is an amorphous Ni-P alloy produced by this method. Membrane (P concentration 8-1
0 wt%) is widely used mainly in advanced technology fields such as computer magnetic disks, drums, condensers, non-magnetic products, and blades of aircraft compressors. However, since this Ni-P alloy film is crystallized at a relatively low temperature (crystallized at 200 ° C to 250 ° C), there is a problem that excellent characteristics as a soft magnetic thin film or a high resistance thin film are lost. In addition, since the coating composition is a two-component system, it is difficult to give an optimal function according to the application.
The melting point of the alloy is relatively low at 890 ° C and there is a problem in heat resistance. There are many problems such as low solderability and discoloration resistance (oxidation resistance), and relatively high film forming temperature of 90 ° C to 93 ° C on the manufacturing side, and there was a limit to the application side. .

By the way, the amorphization of the plating film is
This is because the crystal growth is blocked by adsorbing and mixing metalloid elements such as phosphorus P and boron B at the crystal growth points while the plating film is growing. Therefore, how to form a thermally stable amorphous plating film depends on how many metalloid atoms are adsorbed during the growth of the plating film. The present inventors have found that boron B is more effective than phosphorus P as a crystallization inhibiting element. That is, in the Ni-P alloy film, P in the film is
When the concentration is 8% or more, the Ni-B alloy film is in an amorphous state when the B concentration in the coating is 4% or more, and regarding the crystallization, the Ni-P alloy film containing P of 8.9% is 200C.
It has been confirmed that B is larger than P in the effect of making the plating film amorphous and maintaining its characteristics at 300 ° C. with a Ni—B alloy film containing 4.5% of B and 4.5%. However, as for the Ni-B alloy film, one having a B concentration of 1 wt% in the coating film has been practically used so far, but this is a crystalline alloy film in the as-plated state without heat treatment and in an amorphous state. Can't get Since electroless plating using B (sodium borohydride) as a crystallization inhibiting element (reducing agent) is difficult to manage in the plating bath (decomposition / unstable state), there are few research examples, and it has not been put to practical use. It is in the present situation that has not been done at all.

[0005]

The present invention focuses on highly efficient boron B as a crystallization-inhibiting element (reducing agent) based on the actual situation of the prior art and the findings of the inventors, and this B can be achieved. In a large amount, and as a metal salt, a binary composition of Ni (nickel) and Co (cobalt), that is, a coating composition,
As a ternary system of Co and B, one is excellent in thermal stability,
Secondly, the manufacturing method is a technology (plating composition, type of reducing agent and its addition, plating conditions, etc.) to obtain an amorphous alloy film that allows the Ni / Co ratio to be arbitrarily changed and expands the application in terms of functionality and application. The purpose is to provide as.

[0006]

In order to achieve the above object, the present invention provides a technique for producing an amorphous alloy film by an electroless plating method, wherein nickel chloride and cobalt chloride (Ni / Co) in arbitrary ratios as metal salts, A plating bath is adjusted by adding a sodium borohydride solution (boron B solution) as a reducing agent. At that time, if necessary, auxiliary components such as a stabilizer, a pH adjuster, a buffer, a complexing agent, an accelerator and an improving agent are added to increase the stability of the plating bath and improve the reduction precipitation efficiency. Then, the sodium borohydride solution is added to the plating bath little by little under the conditions (pH, plating temperature, etc.) under which electroless plating is optimally performed, thereby avoiding decomposition and instability of the plating bath, Further, the stability is further increased by adding a lead salt as a stabilizer to the plating bath. Then, the object to be plated is immersed in the plating bath. Then, metal ions of the main components, that is, nickel chloride and cobalt chloride, are deposited on the object to be plated to form an amorphous Ni-Co-B alloy film containing high concentration boron B.

[0007]

EXAMPLES Specific examples will be described below. (1) Plating bath composition Main component: As a metal salt Nickel chloride 0.02 mol / L Cobalt chloride 0.03 mol / L: As a reducing agent Sodium borohydride (boron B) 0.05 mol / L (4 × 10-min / min) 2 mol) Auxiliary component: Lead salt as stabilizer 10 mg / L: Sodium tartrate as complexing agent 0.4 mol / L The above auxiliary component is added to the above main component to form a plating bath. (2) Reducing agent and addition method Since a plating bath using sodium borohydride (boron B) as a reducing agent is extremely unstable and easily decomposed, a lead salt is added as a stabilizer as described above, and By adding a small amount of 4 × 10 −2 mol / min by “Automatic quantitative continuous addition device of sodium borohydride” as shown in FIG. 1, reduction precipitation is promoted in an extremely stable state. (3) Plating conditions Plating temperature 65 ° C pH 12.0 (4) Immersion of test material (object to be plated) Activated by palladium chloride in advance in the electroless plating solution prepared in (1) to (3) above. Was processed 10
A platinum plate of × 10 × 0.1 mm is immersed as an object to be plated. Reduction precipitation. (5) Completion of amorphous Ni-Co-B alloy coating

[0008]

[Characteristics of coatings completed by Examples] The alloy composition of the coatings obtained as described above was obtained by dissolving the coatings deposited on the platinum plate in sulfuric acid (1 + 1) and then using Ni, Co by atomic absorption spectrometry.
The amount of B was quantified by methylene bull-absorptiometry. The structural analysis was performed by the X-ray diffraction method and the electron diffraction pattern. As a result, the alloy composition was 17Ni-
It was revealed from the X-ray diffraction and electron diffraction patterns of FIG. 2 that the coating film was amorphous with 75Co-8B (wt%). Now, let's look at this in relation to heat treatment. The heat treatment was performed by using a vacuum furnace at a vacuum degree of 2 × 10 −7 Torr to raise the temperature to a set temperature (heating rate 8 ° C./min) and holding for 1 hour. As a result, from the X-ray diffraction pattern shown in the figure, it was confirmed that the amorphous state was maintained at a heat treatment temperature of 390 ° C. or lower, and the boride was precipitated by the heat treatment at 400 ° C. or higher. In the processing of 400 ° C ~ 600 ° C, Co2
Although B was deposited and the amount of Co2 B deposited increased in proportion to the heat treatment temperature, the peak position and peak intensity ratio of the X-ray diffraction pattern were almost the same, and a large difference was observed in the crystal structure of the alloy coating. I couldn't do it. Also, two X-ray diffraction patterns of Co2 B and Co3 B were observed in the treatment at 800 ° C to 1000 ° C. The electron beam diffraction results show that the alloy coating that has been heat-treated before the heat treatment at 300 ° C. is amorphous, and that the heat treatment at 600 ° C. results in a polycrystalline structure. This result is X
It agrees with the line diffraction result.

The results of the differential thermal analysis are shown in FIG. In general, the rising temperature is often set as the crystallization temperature, and from this analysis result, the temperature at which the amorphous Ni—Co—B alloy coating film is crystallized by the influence of heat is 416.1 ° C.

From the above results, the amorphous Ni-Co-B alloy coating film according to the present invention is an amorphous Ni-P alloy coating film (P concentration 8 to 10) obtained by the conventional Kanigen plating method.
It was confirmed that it is extremely thermally stable in comparison with a crystallization temperature of 200 ° C. to 250 ° C. at wt%.

A scanning microscope was used to observe the surface of the coating. An SEM image of the coating is shown in FIG. according to this,
There was no great difference in the precipitation state of the alloy up to the heat treatment temperature of 600 ° C, and the coatings treated at 800 ° C and 1000 ° C were partially broken.

The film thickness of the coating film was calculated by measuring the weight of the coating film deposited on the platinum plate. As a result, it was 2.5 μm. The average precipitation rate was 13 μg · cm −2 min −1.

The hardness of the coating was measured by a Vickers hardness meter or a dynamic ultra-fine hardness meter using a diamond triangular pyramid indenter with a ridge angle of 115 ° in relation to heat treatment. As a result, as shown in FIG. 5, both the Vickers hardness and the dynamic hardness showed the highest values at the heat treatment temperature of 400 ° C. This is believed to be due to boride (Co2 B) precipitation. It was also reduced by the heat treatment at 800 ° C and 1000 ° C, which is considered to be due to the structural change of the precipitate (new precipitation of Co3 B) or the partial destruction of the coating surface. The indentation depth and the square root diagram of the load were obtained with an ultra-micro hardness tester, and the distance from the surface where the inflection point began to be affected by the substrate was examined. The inflection point was 0.4 μm for a film thickness of 2.5 μm. In order to measure the hardness of the coating itself without being affected by the base, it is sufficient to perform the test with the indenter penetration depth of 0.4 μm or less. The penetration depth of the indenter at a test load of 1 gf is 0.22 μm for the unheated alloy coating,
0.20μm at 200 ° C, 0.18μ at 300 ° C
m, 400 ° C 0.16 μm, 600 ° C 0.16 μm
μm, 0.21 μm at 800 ° C., 0.1 at 1000 ° C.
It was 29 μm. From the above results, it can be said that, regarding the coating film according to the present invention, the dynamic hardness measured with a test load of 1 gf is the hardness of the coating film itself which is not affected by the base.

[0014]

INDUSTRIAL APPLICABILITY As described above, the present invention uses boron (B), which has a high crystallization inhibition efficiency, as a reducing agent and an arbitrary ratio of Ni (nickel) and Co (cobalt) as a main metal salt.
That is, the coating composition is a three-component system of Ni, Co and B,
In addition, a lead salt is added as a stabilizer of an auxiliary component to adjust the plating bath, and in particular, the reducing agent boron B is added little by little to the plating bath to avoid decomposition and instability of the plating bath. Therefore, reduction precipitation can be performed on the immersed object in a very stable state, and the plating film formation temperature is 65%.
Ni-P plating film formation temperature 90 ° C to 93 ° C
An amorphous alloy film can be obtained at a lower temperature than that. And the amorphous Ni-obtained by the present invention
As confirmed by the above-mentioned characteristics, the Co-B alloy film has much better thermal stability than the conventional Ni-P alloy film and is excellent as a soft magnetic thin film or a high resistance thin film. The characteristics can be exhibited. Further, since the coating composition is a ternary system of Ni, Co and B, it is possible to impart functionality according to the application by freely changing the ratio of Ni and CO, and it is possible to expand the range of application. Further, the alloy film obtained by the present invention has 4
Co2 B is precipitated by the heat treatment at 00 ° C, the hardness of the coating is about twice as high as that at room temperature, and the wear resistance is greatly improved. In addition, it was confirmed that the Ni-P alloy film was excellent in solderability, had little surface discoloration due to heat, and was superior in oxidation resistance to the Ni-P alloy film.

From the above various characteristics and advantages, the amorphous Ni-Co-B alloy film obtained by the present invention is expected to be applied in the advanced technical fields such as electronics and aircraft parts, which are required to have high performance and high reliability. It is something.

[Brief description of drawings]

FIG. 1 is a schematic side view of an electroless plating bath apparatus used to carry out the method of the present invention.

FIG. 2 is a graph showing X-ray diffraction and electron beam diffraction patterns of alloy coatings obtained by the method of the present invention at various heat treatment temperatures.

FIG. 3 is a graph showing the results of differential thermal analysis as above.

FIG. 4 shows SEM images of the same as above, where A is room temperature and B is 300.
° C, C is 600 ° C, D is 800 ° C, D is 1000
SEM image at ° C

FIG. 5: Same as above Graph showing relationship between heat treatment temperature and hardness

Claims (2)

[Claims] 1. In the technique for producing an amorphous alloy film by electroless plating, nickel chloride and cobalt chloride in arbitrary ratios as metal salts and sodium borohydride solution as a reducing agent are added to adjust the plating bath, and the hydrogenation is performed. Sodium boron solution is added to the plating bath little by little under the condition that the electroless plating is performed optimally, avoiding decomposition and instability of the plating bath, while high concentration boron is immersed in the immersed object. Amorphous Ni-Co- containing
Method for producing B alloy film. 2. The method for producing an amorphous Ni—Co—B alloy film according to claim 1, wherein a lead salt is added as a stabilizer to the plating bath.