JP2757673B2 - Continuous plating method of electroless Ni-P-Mo - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous electroless Ni-P-Mo film which can stably provide a Ni-P-Mo film having excellent film properties such as non-magnetic properties even after long use. To a selective plating method.

[0002]

2. Description of the Related Art
As the nonmagnetic plating film, a Ni-P film is well known. This Ni-P coating is made of an electroless Ni-
This is obtained by using a P plating bath, in which nickel ions are reduced to metallic nickel by a reducing action of hypophosphite ions and are deposited on an object to be plated, thereby performing plating.

Accordingly, as the plating progresses, nickel ions and hypophosphite ions in the Ni—P plating bath decrease, thereby decreasing the deposition rate and the composition of the precipitate (alloy composition of Ni and P). Changes. For this reason, conventionally, nickel ions and hypophosphite ions have been appropriately replenished, the concentrations of these ions have been returned to the initial levels, and plating has been continued. Also, the pH of the plating bath decreases as the plating proceeds, so that NaO
A pH adjuster such as H is supplied to maintain the pH of the plating bath at a predetermined level, thereby enabling continuous plating.

On the other hand, various proposals have been made for electroless Ni-P-Mo plating baths and Ni-P-Mo plating films (Japanese Patent Publication No. 57-54545, Japanese Patent Application Laid-Open No. Sho 62-62).
60878 and JP-A-3-97835). However, in these proposals, there is no description of a continuous plating method for electroless Ni-P-Mo.
It is desired to establish a method of continuously using a plating bath.

[0005]

Means for Solving the Problems and Actions The present inventors have conducted various studies in order to meet the above-mentioned demands, and include a water-soluble nickel salt, a water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent. A nickel salt, molybdate, hypophosphorous acid or a salt thereof and sodium hydroxide, ammonia water, sodium (potassium carbonate) or the like as a pH adjuster are supplied to the electroless Ni-P-Mo plating bath. Continuous plating was performed while maintaining the concentration and pH of the components within a predetermined range. In this case, the concentration and pH of each component of the plating bath are Ni
As in the case of -P plating, replenishment was performed so as to maintain a constant value. As a result, although the bath composition and concentration were the same between the new bath and the bath used to some extent, the characteristics of the obtained Ni-P-Mo film changed, and for example, as shown in the Examples section described later, the non- The magnetic properties were different. For this reason,
As a result of further study, instead of setting the control value of hypophosphite ion to a constant value, the concentration control value of hypophosphite ion was gradually increased from the initial value to obtain a new bath. It has been found that the characteristics of the obtained Ni-P-Mo coating and the characteristics of the Ni-P-Mo coating obtained from the bath after long-term use can be maintained at the same level.

[0006] In this case, when the concentration and pH of the bath components are maintained at constant values, the deposition rate gradually decreases. Accordingly, the present inventors have conducted intensive studies on this point, and as a result, by gradually increasing the pH control value of the plating bath, it is possible to prevent a decrease in the deposition rate and perform continuous plating at a constant rate. The present invention has been found.

Accordingly, the present invention provides a water-soluble nickel salt,
An object to be plated is immersed in an electroless Ni-P-Mo plating bath containing a water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent, and a Ni-P-Mo film is formed on the object. In the electroless Ni-P-Mo plating method of forming nickel, nickel ions in the plating bath generated by the progress of plating,
Reduction of molybdate and hypophosphite ions and pH
Nickel ions, molybdate ions and hypophosphite ions are supplied to the plating bath continuously or intermittently in accordance with the decrease in
The method is characterized in that the pH of the plating bath is adjusted to a predetermined control range by adding an H adjuster, and at this time, the control set value of the concentration of hypophosphite ion in the plating bath is gradually increased in accordance with the progress of plating. Electroless Ni-P-Mo continuous plating method, and in such a method, the control set value of the pH of the plating bath is gradually increased according to the progress of plating.
Provide a method for continuous plating of P-Mo.

Hereinafter, the present invention will be described in more detail. The electroless Ni-P- used in the continuous plating method of the present invention is described below.
The Mo plating bath contains a water-soluble nickel salt, a water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent.

Here, as the water-soluble nickel salt, nickel sulfate, nickel chloride or the like is used, and the concentration in the plating bath is 2 to 10 g / l, particularly 4 to 8 g / l as nickel.
It is preferable that

As the water-soluble molybdate, sodium molybdate, ammonium molybdate, potassium molybdate, calcium molybdate, phosphomolybdic acid, ammonium phosphomolybdate and the like are used. 01-5 g / l, especially 0.
It is preferable to set the amount to 0.5 to 1 g / l. When the concentration of molybdate is lower than 0.01 g / l, the molybdenum content in the plating film decreases, and the effect of heat and non-magnetic properties cannot be sufficiently obtained. On the other hand, when the concentration exceeds 5 g / l, the deposition rate decreases, In some cases, poor throwing may occur.

As the hypophosphorous acid or a salt thereof, sodium hypophosphite, potassium hypophosphite and the like are preferably used, and the concentration in the plating bath is 10 to 50 g / l, especially 20 to 50 g / l.
It is preferably 40 g / l.

As complexing agents, monocarboxylic acids such as glycolic acid, lactic acid, gluconic acid and propionic acid, tartaric acid,
Dicarboxylic acids such as malic acid and succinic acid; tricarboxylic acids such as citric acid; and carboxylic acids such as sodium salts, potassium salts and ammonium salts thereof alone or in combination with 2 or more.
Two or more dicarboxylic acids or salts thereof may be used in combination as a complexing agent, particularly from the viewpoint of obtaining an amorphous Ni-P-Mo film having good nonmagnetic properties, although a combination of two or more species may be used. In addition, it is preferable that at least one of them is oxydicarboxylic acid or a salt thereof. In this case, it is particularly preferable to use a combination of an oxydicarboxylic acid or a salt thereof and a dicarboxylic acid or a salt thereof containing no OH group in terms of nonmagnetic properties, deposition rate, and bath stability. It is recommended that the molar ratio be 10: 1 to 0.5: 1, particularly 8: 1 to 1: 1 because the combined effect can be more effectively exhibited. A monooxydicarboxylic acid or a salt thereof and a polyoxydicarboxylic acid or a salt thereof can be used in combination. However, in this case, it is preferable to use them together in the same ratio as described above.

The amount of the complexing agent is appropriately selected.
1 to 7 mol, especially 2 to 6 mol per mol of the water-soluble nickel salt
It is preferred to be molar.

In the electroless Ni-P-Mo plating bath, components such as lead salts and other stabilizers and pH adjusters can be added, and the pH thereof is acidic, especially pH 4-5.
It is preferable to be within the range. If the pH is too low, the deposition rate may decrease, and if the pH is too high, the stress of the plating film may increase and the bath may become unstable.

Using the plating bath of the present invention, Ni-P-Mo
When a plating film is obtained, the object to be plated may be immersed in the plating bath. In this case, the plating temperature is 70 to 95 ° C.
It is preferable to carry out in. The plating rate is usually 5 to 10 μm / hr at a plating temperature of 90 ° C. In plating, it is preferable to stir the plating bath appropriately by a method such as stirring with a stirrer, stirring with a pump, or rocking the object to be plated, so that a good heat-resistant nonmagnetic plating film is reliably obtained by stirring. be able to.

The Ni-P-Mo plating film thus obtained is amorphous in a deposited state, and is generally Ni82-
Preferably, the composition has a composition of 90.9% by weight, P 9 to 13% by weight, and Mo 0.1 to 5% by weight.
The i-P-Mo plating film retains non-magnetism even after heat treatment at a high temperature (for example, 300 ° C.) for a long time (for example, 3 hours). Also, this Ni-P-Mo plating film is
Since the Mo content is small, the advantages of the Ni-P plating film, that is, the advantages of uniform precipitation, high corrosion resistance, high hardness, and high abrasion resistance are effectively exhibited.

Thus, the continuous plating method of the present invention provides an electroless N containing the above-described water-soluble nickel salt, water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent.
When an object to be plated is immersed in an i-P-Mo plating bath and a Ni-P-Mo film is formed on the object to be plated, nickel ions, molybdate ions, hypoxia, and the like in the plating bath generated by the progress of plating. Nickel ions, molybdate ions, and hypophosphite ions are continuously or intermittently supplied to the plating bath according to the decrease in phosphate ions and the decrease in pH to adjust the concentration of these ions to a predetermined control range, and
The adjusting agent is added to adjust the pH of the plating bath to a predetermined control range.

Here, as the chemicals for replenishing nickel ions, molybdate ions and hypophosphite ions, those exemplified in the above description of the components are used, and preferably the same as the chemicals constituting the plating bath. Use Also,
As the pH adjuster, sodium hydroxide, aqueous ammonia, sodium carbonate, potassium carbonate and the like are used.

The concentration control value of nickel ions and molybdate ions is a constant value within the above-mentioned range of the nickel salt concentration and molybdate concentration in the plating bath. Agents can be added.

On the other hand, in the case of hypophosphite ions, the concentration control set value of hypophosphite ions in the plating bath is gradually increased in accordance with the progress of plating. In this case, the degree of the gradual increase is one turn with respect to the initial set value of the hypophosphite ion concentration (one turn consumes or precipitates the entire amount of nickel ions contained in the first Ni-P-Mo bath). If, for example, 6 g / l of nickel ions were present in the first Ni-P-Mo bath, the case where 6 g / l of nickel ions were consumed or precipitated is defined as one turn). 1 to 3 g / l of hypophosphite ion,
More preferably, the added amount of 1.5 to 2.5 g / l is preferably set as the management set value. However, it is preferable to set the first management value so that the management setting value does not exceed the range of the hypophosphorous acid concentration. By gradually increasing hypophosphite ions in this manner, Ni-P-
The non-magnetic properties of the Mo film can be maintained at a constant level.

As a method for gradually increasing the concentration of hypophosphite ions in the bath, a replenisher containing hypophosphite ions in an amount of Ag / l in order to maintain the concentration of hypophosphite ions in the plating solution at the time of building the bath. Is necessary to replenish Bml, the replenishing solution containing the hypophosphite ion concentration in an amount exceeding Ag / l is used, and Bml is replenished. The above-mentioned hypophosphite ion is contained in Ag / l. A method of gradually increasing the replenishing amount of the replenishing liquid to more than Bml, a method of combining these, and the like are included.

It is also preferable that the pH is gradually increased in accordance with the progress of the plating process.
In this case, it is preferable that the degree of the gradual increase be such that the pH increases by 0.05 to 0.15 every one turn, so that the deposition rate can be maintained at a constant level. As described above, the pH range is preferably in the range of 4 to 5, particularly preferably in the range of 4.4 to 4.8,
If the pH is too high, the plating film may have high stress and cracks may occur.
When the pressure is 0 kg / mm ² or more, cracks are likely to occur. Therefore, when the pH is gradually increased, it is preferable to determine the initial pH set value so that the final pH set value does not exceed the upper limit of the pH range. .

The hypophosphite ions and the pH may be increased gradually or intermittently, for example, every 0.1 to 1 turn.

In the continuous plating, the complexing agent is not essentially consumed, but is reduced by pumping out.
It is preferable to replenish as appropriate.

[0025]

EXAMPLES The present invention will be described below in detail with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Examples 1, 2 and Comparative Examples An electroless Ni-P-Mo plating bath having the following composition was prepared, and a zinc-substituted aluminum plate was used as a sample to be plated at 90 ° C. under stirring with a stirrer. Plating was performed continuously.
In this case, the following replenishers were added in the amounts shown below.

The nonmagnetic properties and the deposition rate of the Ni—P—Mo coating were measured every turn (consumption of 6 g / l of nickel). The results are shown in FIGS.

The magnetic measurement conditions are as follows. Magnetic measurement conditions : Vibrating sample magnetometer (BHV- manufactured by Riken Denshi)
50 model) applied magnetic field 2500O _e sensitivity 0.005EMU sample 1 × 1 cm number of measurements n = 2

Bath composition (at building bath ) Nickel sulfate (as nickel) 6 g / l Sodium hypophosphite 30 {Sodium molybdate 0.3} Malic acid 18 {Succinic acid 16} Stabilizer Fine pH 4.5

Replenisher composition A: nickel sulfate 450 g / l B: sodium molybdate 50 g / l C: sodium hypophosphite 500 g / l D: sodium hydroxide 150 g / l

No. 1 (Example 1) Nickel ion concentration control value: 6 g / l (constant) Replenishing solution A addition amount: 60 ml / l (each turn) Molybdate ion concentration control value: 0.3 g / l (constant) Liquid B addition amount: 2 ml / l (every one turn passes) Hypophosphite ion concentration control value: 30 g / l at start,
Thereafter, gradually increase to 40 g / l (final time: 40 g / l) Replenishing solution C addition amount: 80 ml / l (each turn) pH control value: 4.5 at start, gradually increase to 4.7 afterwards (final time) 4.7) Amount of replenisher D added: 60 ml / l (each turn) No. 2 (Example 2) Nickel ion concentration control value: 6 g / l (constant) Replenishing solution A addition amount: 60 ml / l (each turn) Molybdate ion concentration control value: 0.3 g / l (constant) Liquid B addition amount: 2 ml / l (every one turn has passed) Hypophosphite ion concentration control value: 30 g / l at start,
Then gradually increase to 40 g / l (final 40 g / l) Replenishment liquid C addition amount: 80 ml / l (every one turn) pH control value: 4.5 (constant) Replenishment liquid D addition amount: 50 ml / l ( No. 1 turn) No. 3 (Comparative example) Nickel ion concentration control value: 6 g / l (constant) Replenishing solution A addition amount: 60 ml / l (every one turn) Molybdate ion concentration control value: 0.3 g / l (constant) Replenishing solution B addition amount: 2 ml / l (every one turn) Hypophosphite ion concentration control value: 30 g / l (constant) Replenishment solution C addition amount: 70 ml / l (each one turn) pH control value: 4 .5 (constant) Replenishment liquid D addition amount: 50 ml / l (each turn)

From the results shown in FIG. 1, it can be seen that by increasing the hypophosphite ion concentration gradually with the progress of plating, the coating obtained after being used for a long time was non-magnetic, When the acid ion concentration is kept constant, it is recognized that the Ni-P-Mo film obtained from the plating bath after being used for a long time becomes magnetic.

From the results shown in FIG. 2, it is recognized that the deposition rate can be kept constant by gradually increasing the pH as the plating proceeds.

[0034]

According to the present invention, the Ni-P-Mo film obtained from the plating bath after continuous use for a long time maintains the same film properties as those of the new bath. Can be done.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the number of turns and the saturation magnetic flux density of Ni—P—Mo films obtained from the plating baths of Examples 1 and 2 and a plating bath of a comparative example.

FIG. 2 is a graph showing the relationship between the deposition rate and the number of turns of Ni—P—Mo films obtained from the plating baths of Examples 1 and 2 and the plating bath of Comparative Example.

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masahiro Saito 1-5-1, Hirakata Exit, Hirakata City, Osaka Prefecture Uemura Industry Co., Ltd. Development Technology Research Laboratory (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 18/31 C23C 18/50

Claims (2)

(57) [Claims] An object to be plated is immersed in an electroless Ni-P-Mo plating bath containing a water-soluble nickel salt, a water-soluble molybdate, hypophosphorous acid or a salt thereof, and a complexing agent, Electroless Ni— forming a Ni—P—Mo film on the object to be plated
In the P-Mo plating method, nickel ions, molybdate ions, molybdate ions, molybdate ions, molybdate ions, and molybdate ions in the plating bath continuously or intermittently depending on the decrease in pH and the decrease in pH in the plating bath,
Hypophosphite ions are supplied to the plating bath to adjust the concentration of these ions to a predetermined control range, and a pH adjuster is added to adjust the pH of the plating bath to a predetermined control range. A continuous plating method for electroless Ni-P-Mo, characterized by gradually increasing a control set value of the concentration of hypophosphite ion in a plating bath over time. 2. The continuous electroless Ni-P-Mo plating method according to claim 1, wherein the control set value of the pH of the plating bath is gradually increased as the plating progresses.