JPS60128289A - Composite plating method - Google Patents

Abstract

PURPOSE:To obtain a film having superior wear resistance by carrying out plating with pulse current in an acidic noble metal plating bath contg. dispersed wear resistant fine particles of a prescribed particle size. CONSTITUTION:Fine particles of nitride, oxide, boride or carbide of Si, Ti, Zr or Al are dispersed in an acidic noble metal plating bath. The average particle size of the fine particles is <=1mum. Electroplating is carried out with ordinary pulse current in the plating bath to form a film contg. said fine particles on the surface of a body to be plated. The current density may be gradually reduced without using the pulse current. The resulting film has superior wear resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel composite plating method, more specifically,
Forms a highly wear-resistant plating film on the surface of the plated object, consisting of a uniform composite of highly hard fine particles such as nitrides, oxides, borides, and carbides of silicon, titanium, zirconium, and aluminum. Regarding composite plating methods, in the conventional plating of precious metals or precious metal alloys such as acidic gold plating or gold alloy plating, combinations of these and nitrides, oxides, borides, carbides, etc. of silicon, titanium, zirconium, and aluminum have been used. High hardness,
Various plating methods have been proposed in which a plating film with improved wear resistance is formed by combining fine particles with a melting point. For example, a method of composite plating by suspending powdered substances such as silicon carbide, aluminum oxide, tungsten carbide, and zirconium oxide in an electrolytic solution (Japanese Patent Publication No. 56-380
6), a young method for gold plating in which one or more of various carbides, nitrides, borides, silicides, and oxides are eutectoid (JP-A-52-88549, JP-A-57-7)
No. 1812) and the like are disclosed.

However, in commonly used acid plating baths, hydrogen gas is generated from the cathode during plating, and wear-resistant fine particles are adsorbed to this hydrogen gas, or the flow of the bath due to hydrogen gas causes the cathode to emit hydrogen gas. The fine particles are lacking in the vicinity, and as a result, the fine particles are not sufficiently combined in the plating film, and when the cathode current density is lowered to suppress hydrogen gas generation, the fine particles are difficult to be combined.
In addition, there are drawbacks such as a long plating time, and none of the above methods can be said to be necessarily satisfactory.

In addition, wear-resistant particles with a small particle size, especially an average particle size of 1μ
In order to uniformly disperse less than m in the plating bath,
Attempts have been made to add drugs such as surfactants. However, the addition of such a chemical increases the stress of the plating film, and there is a possibility that hydrogen gas may be incorporated into the film. Furthermore, 0, which can be easily and uniformly dispersed without adding such drugs,
Wear-resistant fine particles having a particle size on the submicron order of 1 μm or less are generally difficult to obtain, and even if they are available, they are extremely expensive.

The present inventors have solved these problems and created commercially available plating baths and abrasives without adding chemicals other than those required for normal plating bath compositions, such as surfactants. As a result of extensive research in order to provide a wet plating method that uses wear-resistant fine particles such as, and forms a wear-resistant plating film that is a uniform composite of these fine particles at the same plating speed as normal plating, In the plating bath, as mentioned above, the hydrogen gas generated from the cathode has a particle size of 0.1 to 1 μm.
It was discovered that the generation of hydrogen gas could be suppressed by adversely affecting the precipitation of particles, and by using a pulsed current, the purpose could be achieved. Based on this knowledge, the present invention was completed. reached.

That is, the present invention is made by dispersing wear-resistant fine particles with an average particle size of 1 μm or less in an acidic noble metal plating bath, and performing electroplating using pulsed current to composite the fine particles on the surface of the object to be plated. The present invention provides a composite plating method characterized by forming a plating film.

A feature of the present invention is that by using a pulsed current, it is possible to suppress the generation of hydrogen gas at the cathode, and as a result, it is possible to form a tight coating in which wear-resistant fine particles are uniformly combined.

Although there is an example of using a pulsed current in ordinary plating (Japanese Unexamined Patent Publication No. 100991/1983), in a system in which wear-resistant fine particles are dispersed in a plating bath as in the present invention, There is no example of using pulsed current for the purpose of suppressing the generation of hydrogen gas, and the present invention can be said to be a novel composite plating method.

The acidic noble metal plating bath used in the method of the present invention is:
There are acidic plating baths for noble metals such as gold, rhodium, and ruthenium, and acidic plating baths for noble metal alloys such as gold alloys and silver alloys, and representative examples include citric acid-based gold-nickel alloy plating baths.

Preferable examples of the wear-resistant fine particles used in the method of the present invention include fine particles having high hardness and high melting point, such as nitrides, oxides, borides, and carbides of silicon, titanium, zirconium, and aluminum.

These wear-resistant fine particles may be used alone or in combination of two or more, and the average particle size thereof is 1 μm or less, preferably 0.5 μm or less. Further, if the particle size of the composite particles having a plating film thickness of about 1.5 to 2.0 μm exceeds 1 μm, the wear resistance of the plating film deteriorates.

The pulsed current used in the method of the present invention is obtained by passing a direct current rectified by a rectifier through a pulse generator. An example of the waveform model for this pulse current is shown in the first example.
As shown in the figure.

In the pulsed current, electrolysis is performed during the ON time and stops during the QFF time.

If the ON time is too long, hydrogen gas will be generated violently at the cathode, and if the OFF time is too short, the cathode will be in a state where hydrogen gas is likely to be generated.For example, when the current density is 7.0 A/dyx2, the ON time is 0.27 seconds or less, ○If the FF time is QN time of 0.27 seconds, it is desirable that it is longer than 0.39 seconds. Also, if the ON time is shorter than 0.27 seconds, the QFF time is 0.3 seconds.
Although the plating time may be 9 seconds or less, it is necessary to lengthen the plating time.

FIG. 2 is an example of a pulse waveform model when the current density of the pulse current is successively lowered. As the current density of the pulsed current is successively reduced in this manner, the combined amount of wear-resistant particles in the plating film is gradually reduced from the surface of the object to be plated toward the upper layer. therefore,
The uppermost layer of the plating film can be in a state in which the fine particles are not combined, and a plated surface with excellent gloss can be obtained. That is, by successively lowering the current density of the pulsed current, it is possible to obtain a glazed coating that is excellent in both wear resistance and gloss.

As for wear resistance, as mentioned above, it is slightly inferior to the one in which the current density is constant, but it is far superior to that in the conventional plating method.

Note that when adopting such a method of successively lowering the current density of the pulse current, there is no problem in using a direct current having a current density similar to that used in the conventional plating method in the final stage.

As mentioned above, in order to reduce the current density sequentially,
A Dk controller can be used.

FIG. 6 is a block diagram showing an example of a plating system for carrying out the composite plating method of the present invention, in which reference numeral 1 is a rectifier for obtaining direct current, 2 is an ammeter, and 3 is a pulse 5 is an electrolytic cell equipped with a pulse generator for obtaining a current, a Dk control device 4 for changing the current density, and a stirring device 6.

In the method of the present invention, a dispersant such as a surfactant may be added to improve the dispersibility of the wear-resistant particles in the plating bath.

According to the method of the present invention, hydrogen gas generation at the cathode during plating can be suppressed by using a pulsed current, and as a result, wear-resistant fine particles such as commercially available abrasives are uniformly distributed in the plating film. Because the material can be dispersed into the material, the abrasion resistance is 3 to 3 times higher than that of the same thickness made using conventional plating methods.
A plating film that is 10 times higher can be obtained. Furthermore, by successively lowering the current density of the pulsed current, it is possible to obtain a plating film that has good wear resistance and excellent gloss comparable to that of conventional plating methods. The present invention will be explained in more detail by way of examples.

Example 1 A citric acid-based Au-Ni alloy plating solution was used as a plating bath, and polishing s with a nominal particle size of 0.5 μm was used as wear-resistant fine particles.
Using tc 1oo fl , l (plating solution), p
) Around 14.0, room temperature, cathode current density Dk 7 A /
6m2 condition and pulse condition ON time 0.1
9 seconds.

The OFF time was set to 0.39 seconds, and the watch case was plated while stirring the plating bath.

Plating was performed for a total of 10 minutes (ON time and QFF time) to obtain a 2.0 μm plated film. Approximately 15 vol.
k 2.0 μm).

The watch case was previously coated with a 2 μm thick nickel plating film as a base.

For comparison, cathode current density Dk3. oA/eL
m2. Plating was carried out for 10 minutes under the same conditions as above except for the absence of pulses. When the surface of the obtained plating film was analyzed using an X-ray microanalyzer and a scanning electron microscope, it was found that SiC was not combined in the plating film.

Example 2 Exactly the same method as in Example 1, except that a plating system as shown in FIG. 6 was used, the cathode current density was lowered stepwise, and a pulsed current having a pulse waveform as shown in FIG. 3 was used. The watch case was plated. The QN time and OFF time in the pulse current are the same as in the first embodiment.

According to this plating method, when the cathode current density is 7Vdml, the most SiO is present in the film, which is 6.3V"7+2
．． 4.9 A/dfiz and the current Wj degree below 1'
)""Ci< D, the composite amount of SiO also decreases, and 3
．． 5 A/dx2 has no SiC composite, but Au-Ni
Therefore, the total s1c content in the coating is 10 Vo1%, which makes it less effective than when the current density is constant, but the coating surface is smooth and the appearance is similar to that of conventional Au- The state was close to that of a Ni alloy plating film.

Further, the wear resistance of this plating film was slightly inferior to that of a constant cathode current density, but was 6 to 5 times higher than that of a conventional Au-Ni alloy plating film.

Example 6 A watch case was plated in the same manner as in Example 1, except that the QN time and QFF time in the pulse current and the current density were changed as shown in Table 2.

Abrasion resistance of the obtained glazed film, surface condition of plating, S
The dispersion state and presence or absence of 1C were investigated, and the results are shown in Table 2.

Regarding the surface condition of the plating, good one is marked as ○, poor one is marked as evaluated.

Also, the scale and Q of the pulse generator used in this example
Table 1 shows the relationship between N time and QFF time.

From Table 1 and Table 2, if the pulse width is short and the period is long, the total ON
If the time is short, the plating film will be thin, if the Dk is too high, the surface condition of the plating will be poor, and if the Dk is too low, the plating film will be thin.
not to combine O, and a particle size of 0.5 μm,
Dk 7,0 A/d77I2i1The conditions under which hydrogen generation can be suppressed are when the maximum QN time is 0.27 seconds.
It can be seen that the QFF time needs to be longer than 0.69 seconds.

[Brief explanation of drawings]

Figure 1 shows an example of a waveform model for the current when the current density of the pulsed current is constant, and Figure 2 shows an example of a waveform model for the current when the current density of the pulsed current is gradually decreased. . FIG. 3 is a block diagram showing an example of a plating system for implementing the composite plating method of the present invention, in which reference numeral 1 is a rectifier, 2 is an ammeter, 3 is a pulse generator, and 4 is a Dk The control device and 5 are electrolytic cells. Patent Applicant Orient Watch Co., Ltd. Agent Agata Ming Procedural Amendment 1985 1? , 3rd Japan Patent Office Commissioner Manabu Shiga 1, Indication of the case, Patent Application No. 232799 of 1982, 2, Name of the invention Composite plating method 3, Person making the amendment Relationship with the case Patent applicant Sotokanda, Chiyoda-ku, Tokyo 2J 4-4 Orient Watch Co., Ltd. Representative Ritsu Tohki 4, Agent Kawashima Kunishin Building 8th floor 5, 2-2-2 Shinbashi, Minato-ku, Tokyo
, Date of amendment order Initiation 6, Number of inventions increased by amendment 0 7, Subject of amendment Column 8 for detailed explanation of the invention in the specification, Contents of amendment (1) 4th line from the bottom of page 3 of the specification ~ Line 3, “can be easily and uniformly dispersed without adding such drugs”,
I would like to correct this to ``In order to obtain a desirable composite plating film, it is better to use as fine particles as possible.'' (2) Change [Precipitation] on page 4, line 11 to [Composite].
I will correct it. (3) In the 6th line of the 6th page of the same page, ``also'' is corrected to ``this\ wa''. (4) [Deteriorate] on page 6, line 8. ”, [for deterioration]. ” will be corrected. (5) On page 14, line 8, after "I understand, etc.", add the following sentence on a new line. [Example 4] A citric acid-based Au-Ni alloy plating solution was used as a plating bath, and a nominal average particle size of 0.3 μm (1) was used as wear-resistant fine particles.
a-A120: Using +100y# (plating solution), p
Around l+4.0, room temperature, cathode current density Dk25 A/d
Plating was applied to the watch case under the conditions of p2 and the pulse conditions were set to ON time 0.18 seconds and OFF time 0.39 seconds, and the plating bath was vigorously stirred with a magnetic stirrer. did. Plating was carried out for 10 minutes in total of ON time and OFF time to obtain a plated film with a thickness of 2.0 μm. U-A1203 is uniformly dispersed in this coating, and the wear resistance of this coating is higher than that of conventional A1203.
Approx.
It was double that. Note that the watch case was previously coated with a nickel plating film with a shoulder thickness of 2μ as a base. Example 5 A citric acid-based pure gold plating solution was used as a plating solution, and TiN10 (h/
Using ρ (plating solution), pH was around 6.5, room temperature, cathode current density DklOOA/civ2, and pulse conditions were set to ON time of 0.18 seconds and OFF time of 0.39 seconds.
The watch case was subjected to high-speed plating while the plating solution was flowing at a high speed of 10 z/see. Plating was performed for 30 seconds in total for ON time and OFF time to obtain a plated film with a thickness of 0.3 μm. TiN is uniformly dispersed in this film, and the wear resistance of this film is higher than that of the conventional Au-Co alloy plating film (0.3μ
shoulder) was approximately 10 times larger. In addition, the watch case includes
A nickel plating film with a thickness of 2 μM was previously applied as a base. Example 6 A citric acid-based Au-Ni alloy plating solution was used as a plating bath, and Zr with a nominal average particle size of 1.0 μm was used as wear-resistant fine particles.
Using 02100y# (plating solution), plating was performed under the conditions of pH around 4.0, room temperature, cathode current density Dk30 A/dII2, and pulse conditions of ON time 0.18 seconds and OFF time 0139 seconds. Plating was applied to the watch case while stirring the bath vigorously using a magnetic cooler. The total of ON time and Kano F time is 1
Plating was performed for 0 minutes to obtain a plated film with a thickness of 2.0 μI. ZrO2 is uniformly dispersed in this coating, and the wear resistance of this coating is as high as α-At)20.
It was equivalent to or better than a film made by uniformly dispersing. Note that the watch case was previously coated with a 2 μl thick nickel plating film as a base. ]

Claims (1)

[Claims] 1. Wear-resistant fine particles with an average particle size of 1 μm or less are dispersed in an acidic noble metal plating bath, and electroplating is performed using pulsed current to make the fine particles composite on the surface of the object to be plated. A composite plating method characterized by forming a plating film consisting of: 2. The method according to claim @1, in which the current density of the pulsed current is successively reduced. 6 Wear-resistant fine particles include silicon, titanium, zirconium,
The method according to claim 1 or 2, wherein the fine particles are aluminum nitride, oxide, boride, and carbide.