JP2004143517A - Oscillator, and method for plating surface of oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillator made of a tungsten heavy alloy for an oscillation generator incorporated into a portable telephone or the like, in which corrosion resistance to withstand a high temperature and humidity test stipulated in IEC (International Electrotechnical Committee)-68-2-30 can be obtained, and to provide a method for plating the surface of the oscillator. <P>SOLUTION: The oscillator 1 comprises a tungsten heavy alloy, and in which at least nickel plating layers 2a and 2b are formed in order from the surface thereof. The nickel plating layers 2a and 2b are formed respectively by an electroplating method or an electroless plating method. When the nickel plating layer 2a is formed by the electroplating method of heat-treating the nickel plating layer 2a, the denseness of the nickel plating layer 2a and its adhesion to the surface of the oscillator 1 are improved. When it is formed by the electroless plating method, its adhesion to the surface of the oscillator 1 is improved. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a vibrator for a vibration generator built in an electronic device such as a mobile phone.
[0002]
[Prior art]
BACKGROUND ART In a vibrator for a vibration generating device built in an electronic device such as a mobile phone, tungsten heavy metal having a specific gravity of 17.5 to 18.5 is generally used. As the tungsten heavy alloy, those having a main composition of W-Ni-Cu, W-Ni-Fe, and W-Mo-Ni-Fe are known.
[0003]
Such a vibrator made of tungsten heavy alloy is conventionally manufactured by a so-called powder metallurgy method. That is, it is manufactured by sintering a mixed powder obtained by adding a metal powder such as Ni, Cu, Fe, and Mo to tungsten powder in a fan shape at a high temperature of 1300 to 1500 ° C. In order to obtain a high specific gravity, ordinary tungsten heavy metal has a tungsten composition ratio in the range of 90 to 98% by weight, and the remaining 2 to 10% by weight is composed of an additional metal. Then, by generating a liquid phase portion in the added metal during sintering, the alloy is made denser and the toughness is enhanced. The vibrator thus obtained is usually fixed by caulking to the rotating shaft of a small motor in a vibration generator built in an electronic device such as a mobile phone.
[0004]
Such a vibrator is required to have corrosion resistance that can withstand a predetermined environmental test. Tungsten heavy alloy has sufficient corrosion resistance to acids such as hydrogen sulfide and sulfurous acid, or alkali, but on the other hand, in a high-temperature and high-humidity environment, it is easily corroded, such as formation of tungsten hydroxide and tungsten oxide. Become. Conventionally, by forming a nickel plating layer on the surface of a vibrator, improvement in corrosion resistance in a high-temperature and high-humidity environment has been attempted.
[0005]
For this reason, a test is performed in a high-temperature and high-humidity environment. In this test, the vibrator is crimped to the rotating shaft of the motor, for example, left for 1000 hours in an environment of a temperature of 40 ° C. and a humidity of 90%, and It is required that corrosion does not occur on the surface. Here, the vibrator is crimped to the rotating shaft in order to approximate an actual use condition. Also, by fixing the vibrator to the rotating shaft of a small motor by crimping, nickel plating on the vibrator surface is performed. This is because the layer is damaged by microcracks and the like, which causes corrosion, and the effect of such damage on corrosion is to be observed.
[0006]
Conventionally, to form a nickel plating layer, either a so-called electrolytic plating method or an electroless plating method is applied, and a nickel plating layer having a sufficient corrosion resistance is formed relatively easily by any of these methods. The exam was cleared.
[0007]
By the way, according to the electrolytic plating method, a nickel plating layer generally having excellent adhesion to tungsten heavy metal is obtained, but many pinholes are generated and the plating layer is inferior in density. On the other hand, according to the electroless plating method, the denseness is excellent, but the adhesion to tungsten heavy metal tends to be poor. On the other hand, as a method of forming a nickel plating layer excellent in both adhesion and denseness, Patent Literature 1 discloses a method in which an electrolytic plating layer having excellent adhesion is formed on a first layer, A two-layer plating method for forming an electroless plating layer having excellent denseness on a layer is disclosed.
[0008]
[Patent Document 1]
JP-A-7-224345 (page 2)
[0009]
[Problems to be solved by the invention]
In recent years, a vibrator built in a mobile phone has been required to have corrosion resistance in a high-temperature and high-humidity test specified in IEC-68-2-30, which is more strictly conditional than the conventional test described above. Specifically, a test cycle in which the vibrator is crimped on the rotating shaft of the motor and left for 12 hours in an environment of 25 ° C./95% humidity to 12 hours in an environment of 55 ° C./95% humidity is performed. It is required that no corrosion occurs on the surface of the vibrator when the vibration is continued 35 times in total.
[0010]
Therefore, the present inventor performed the above-described high-temperature and high-humidity test on a vibrator in which a nickel plating layer was formed on the surface of tungsten heavy alloy by a conventional electroplating method and a two-layer plating method. It has been found that none of the techniques can prevent corrosion of the vibrator.
[0011]
The present invention relates to a vibrator made of tungsten heavy alloy for a vibration generator incorporated in a mobile phone or the like, which vibrator has corrosion resistance enough to withstand a high-temperature and high-humidity test specified in IEC-68-2-30, and a vibrator. An object of the present invention is to provide a method for forming a plating on a surface.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a vibrator of the present invention has the following configuration. That is, it contains tungsten heavy metal, and at least a first nickel plating layer and a second nickel plating layer are formed in this order from the surface, and the first nickel plating layer and the second nickel plating layer are formed by electrolytic plating or It is formed by any one of the electroless plating methods. By subjecting the first nickel plating layer to heat treatment, when the first nickel plating layer is formed by an electrolytic plating method, the first nickel plating layer has a high density and a good adhesion to the surface of the vibrator. When the first nickel plating layer is formed by an electroless plating method, the first nickel plating layer has improved ductility and adhesion to the surface of the vibrator.
[0013]
In order to achieve the above object, a method for forming a plating on a vibrator surface according to the present invention has the following configuration. That is, a step of performing an etching process on the surface of a vibrator including tungsten heavy alloy, a step of forming a first nickel plating layer by either an electrolytic plating method or an electroless plating method, and a step of forming a first nickel plating layer on the first nickel plating layer. On the other hand, (a) a step of performing a heat treatment in a temperature range of 700 to 1000 ° C., (b) a reducing atmosphere, a non-oxidizing gas atmosphere, or a vacuum, with a processing time of 5 to 60 minutes. And forming a second nickel plating layer on the first nickel plating layer by either an electrolytic plating method or an electroless plating method.
[0014]
With these configurations, a highly corrosion-resistant nickel-plated layer can be formed on the surface of the vibrator made of tungsten heavy alloy, and a vibrator having corrosion resistance that can withstand the high-temperature and high-humidity test specified in IEC-68-2-30 is obtained.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration of a vibrator for a vibration generator according to the present embodiment. Reference numeral 1 denotes a vibrator made of tungsten heavy alloy having a composition ratio of W 95% by weight-Ni 3% by weight-Cu 2% by weight and a specific gravity of 18.2, and is manufactured by a powder metallurgy method. A nickel plating layer 2 is formed on the surface of the vibrator 1. The vibrator 1 has a sector shape with a radius R = 3 mm, a circumferential length L = 7.3 mm, and a wall thickness t = 3 mm, and a mounting groove 3 is provided at the center thereof. Reference numeral 5 denotes a rotating shaft of the small motor 4, and the rotating shaft 5 is fitted into the mounting groove 3 of the vibrator 1 and caulked. Thus, the vibrator 1 is fixed to the small motor 4.
[0016]
In order to realize the vibrator 1 having corrosion resistance that can withstand the high temperature and high humidity test specified in IEC-68-2-30, the present inventor has described the configuration and method of forming a nickel plating layer formed on the surface of the vibrator 1. We examined from both sides.
[0017]
FIG. 2 shows the configuration of the nickel plating layer 2 formed on the surface of the vibrator 1 based on the results of this study. Here, the nickel plating layer 2 has a two-layer structure of a nickel plating layer 2a and a nickel plating layer 2b from the surface of the vibrator 1. The nickel plating layer 2 may have a configuration of three or more layers composed of a nickel plating layer formed by any one of an electroless plating method and an electrolytic plating method.
[0018]
Here, the nickel plating layer 2 is characterized in that the following heat treatment is applied to the nickel plating layer 2a formed by the forming step, that is, either the electrolytic plating method or the electroless plating method. That is, (a) in a temperature range of 700 to 1000 ° C., (b) in a reducing atmosphere such as hydrogen or green gas, a non-oxidizing gas atmosphere such as argon gas, or in a vacuum, or (c) a processing time of 5 to 60. This is a heat treatment performed within the range of minutes.
[0019]
Then, it is necessary that the nickel plating layer 2b is formed on the nickel plating layer 2a by any one of the electrolytic plating method and the electroless plating method.
[0020]
According to the analysis of the present inventor, by performing a heat treatment on the nickel plating layer 2 a in the vibrator 1, even if the nickel plating layer 2 a is formed by the electrolytic plating method or the electroless plating method, It was found that the corrosion resistance of the plating layer 2 was greatly improved.
[0021]
For example, when the nickel plating layer 2a is formed by an electrolytic plating method, defects such as pinholes are reduced or dissipated, and the denseness of the plating layer and the adhesion of the plating layer to tungsten heavy metal on the surface of the vibrator 1 are improved. On the other hand, when formed by electroless plating, the ductility and the adhesion of the plating layer to tungsten heavy metal on the surface of the vibrator 1 are improved.
[0022]
In addition, the nickel plating layer 2 is composed of two or more layers as described above, and the interface formed between the nickel plating layer 2a and the nickel plating layer 2b generates the nickel plating layer 2b by caulking the vibrator 1. Propagation of the micro cracks to the nickel plating layer 2a is suppressed, and the nickel plating layer 2a on the surface of the vibrator 1 is protected from damage.
[0023]
As described above, in the present embodiment, by performing the heat treatment on the nickel plating layer 2a on the surface of the vibrator 1, both the denseness and the adhesion are excellent. Further, by forming the nickel plating layer 2 from two or more layers, the first plating layer 2a is protected from damage.
[0024]
Even if the nickel plating layer 2 is composed of two or more layers, if the nickel plating layer 2a is not subjected to a heat treatment, the nickel plating layer 2a has corrosion resistance enough to withstand the high temperature and high humidity test specified in IEC-68-2-30. Even if the nickel plating layer 2a is subjected to a heat treatment, if the nickel plating layer 2 has a single-layer structure composed of only the nickel plating layer 2a, similarly, sufficient corrosion resistance cannot be obtained.
[0025]
In the present embodiment, the nickel plating layer 2 is formed by the following (i) pretreatment step- (ii) formation step of first plating layer (nickel plating layer 2a)-(iii) heat treatment step- (iv) It is formed by a series of steps including a step of forming two or more plating layers.
[0026]
(I) Pretreatment Step A vibrator 1 made of tungsten heavy alloy is prepared, and the vibrator 1 is subjected to a conventional alkaline degreasing cleaning using a caustic soda solution or the like and a hydrochloric acid active cleaning, followed by electrolytic degreasing. Next, the vibrator 1 after the cleaning is subjected to an etching process using a potassium ferricyanide, a hydrofluoric-nitric acid, or a hydrogen peroxide solution to form irregularities on the surface of the vibrator 1. Subsequently, an electrolytic nickel strike layer of about 0.2 μm is formed on the surface of the vibrator 1 by a conventional method.
[0027]
According to the results of the study by the present inventors, it has been found that the irregularities formed on the surface of the vibrator 1 are effective for improving the adhesion between the surface of the vibrator 1 and the nickel plating layer 2a.
[0028]
(Ii) Step of Forming First Plating Layer (Nickel Plating Layer 2a) (A) In the case of electrolytic plating, the vibrator 1 is set as a cathode and this is placed in a watt bath containing nickel sulfate as a main component. By immersing and operating in an appropriate current density range, Ni is precipitated on the surface of the vibrator 1.
[0029]
(B) In the case of the electroless plating method, the oscillator 1 is immersed in a plating solution in which nickel sulfate as a metal salt and sodium hypophosphite as a reducing agent are dissolved, and Ni is precipitated on the surface of the oscillator 1 by a chemical reaction. Let it.
[0030]
Here, in any of the plating methods, the thickness of the first nickel plating layer 2a is set in the range of 0.5 to 3.0 μm.
[0031]
(Iii) Heat treatment step The first nickel plating layer 2a formed on the surface of the vibrator 1 is subjected to (a) a temperature range of 700 to 1000 ° C., (b) a reducing atmosphere of hydrogen, green gas, etc., argon In a non-oxidizing gas atmosphere such as a gas or in a vacuum, (c) heat treatment is performed within a processing time of 5 to 60 minutes. In this case, in (A), if the temperature is lower than 700 ° C., the effect of the heat treatment cannot be obtained, while if it exceeds 1000 ° C., the vibrators 1 are fixed to each other. If the time is less than 5 minutes in (c), the effect of the heat treatment cannot be obtained, and if it exceeds 60 minutes, no further effect can be expected.
[0032]
(Iv) Step of forming second and subsequent plating layers The second and subsequent nickel plating layers formed on the nickel plating layer 2a are formed in the same manner as the nickel plating layer 2a shown in (i). However, with the thickness of the nickel plating layer 2a being set in the range of 0.5 to 3.0 μm in any plating method, the nickel plating layers of the second and subsequent layers are in the range of 1 to 7 μm. In addition, the thickness of the entire nickel plating layer 2 needs to be set in the range of 1.5 to 10.0 μm. By setting the thickness of the first nickel plating layer 2a smaller than the thickness of the second and subsequent nickel plating layers in this manner, the adhesion of the nickel plating layer 2a to the surface of the vibrator 1 is enhanced.
[0033]
In order to confirm the corrosion resistance of the nickel plating layer 2 in the present embodiment, the nickel plating layers 2 each having two typical configurations A and B were formed on the vibrator 1 by the above-described method. .
[0034]
Here, each of the nickel plating layers 2 of the configuration A and the configuration B has a two-layer configuration. In the configuration A, the first layer is composed of a nickel plating layer 2a formed by an electrolytic plating method with a thickness t ₁ = 1.5 μm, and the second layer is formed by a nickel plating layer 2b formed by an electroless plating method with a thickness t ₂ = 3.5 μm. Consists of In the configuration B, the first layer is made of a nickel plating layer 2a formed by electroless plating with a thickness t ₁ = 1.5 μm, and the second layer is formed by nickel plating formed by electroplating with a thickness t ₂ = 3.5 μm. It consists of layer 2b.
[0035]
The nickel plating layer 2a of the configuration A was subjected to a heat treatment at 850 ° C./30 minutes in a hydrogen atmosphere, and the nickel plating layer 2a of the configuration B was subjected to a heat treatment at a temperature of 780 ° C./40 minutes in a hydrogen atmosphere. . In any case, the vibrator 1 before plating is subjected to a series of pretreatments including alkali degreasing cleaning, electrolytic degreasing cleaning, etching with potassium ferricyanide solution, hydrochloric acid active cleaning, and electrolytic nickel strike processing. Was given.
[0036]
A high-temperature and high-humidity test specified in IEC-68-2-30 was performed in a state where the vibrator 1 having the nickel plating layers 2 of the configuration A and the configuration B was fixed by being caulked to the rotating shaft 5 of the motor 4. As a result, no corrosion occurs in any of the vibrators 1 having the nickel plating layers 2 of the configurations A and B, and the vibrator 1 having the nickel plating layers 2 according to the present embodiment has excellent corrosion resistance. Has been confirmed.
[0037]
【The invention's effect】
According to the present invention, in a vibrator made of tungsten heavy alloy for a vibration generator built in a mobile phone or the like, a vibrator that can obtain corrosion resistance that can withstand a high-temperature and high-humidity test specified in IEC-68-2-30 is particularly provided. can get.
[Brief description of the drawings]
FIG. 1 is a three-dimensional view of a vibrator on which a nickel plating layer according to the present invention is formed. FIG. 2 is a photograph showing a cross section of a nickel plating layer formed on a vibrator according to the present invention.
DESCRIPTION OF SYMBOLS 1 Oscillator 2, 2a, 2b Nickel plating layer 3 Mounting hole 4 Motor 5 Rotation axis

Claims (4)

Including tungsten heavy alloy, at least a first nickel plating layer and a second nickel plating layer are formed in order from the surface,
The first nickel-plated layer and the second nickel-plated layer are each formed by any one of an electrolytic plating method and an electroless plating method.
By performing a heat treatment on the first nickel plating layer,
When the first nickel plating layer is formed by an electrolytic plating method, the first nickel plating layer has improved denseness and adhesion to the surface of the vibrator;
When the first nickel plating layer is formed by an electroless plating method, the first nickel plating layer has improved adhesion to the surface of the vibrator. . The heat treatment was performed in the temperature range of (A) 700 to 1000 ° C., (B) a reducing atmosphere, a non-oxidizing gas atmosphere, or a vacuum, and (C) a processing time of 5 to 60 minutes. The vibrator according to claim 1, wherein the vibrator is a vibrator. A step of performing an etching process on the surface of the vibrator containing tungsten heavy metal,
Forming a first nickel plating layer by either an electrolytic plating method or an electroless plating method;
(B) a treatment time of 5 to 60 minutes for the first nickel plating layer in a (b) reducing atmosphere, a non-oxidizing gas atmosphere, or a vacuum at a temperature range of 700 to 1000 ° C. Performing a heat treatment within the range;
Forming a second nickel plating layer on the first nickel plating layer by either an electrolytic plating method or an electroless plating method. The thickness of the first nickel plating layer is in the range of 0.5 to 3 μm, the thickness of the second nickel plating layer is in the range of 1 to 7 μm, and the total thickness of the nickel plating layer is 1.5 to 3 μm. 4. The method for forming a plating on the vibrator surface according to claim 3, wherein each of the thicknesses is set within a range of 10 μm.

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