JP6487813B2 - Nickel tungsten alloy and contact probe - Google Patents

Description

  The present invention relates to a nickel tungsten alloy having improved ductility and a contact probe including the same.

The nickel plating film has low heat resistance and corrosion resistance. From the viewpoint of improving the heat resistance and corrosion resistance of the nickel plating film, a nickel tungsten alloy plating film has been proposed (Patent Document 1).
In addition, attempts have been made to improve ductility in bulk nickel-tungsten alloy plating products (Non-Patent Documents 1 and 2).

JP 2001-158998 A

Materials Letters 99 (2013) pp. 65-67. Materials Science & Engineering A 578 (2013) 318-322.

  In the nickel tungsten alloy, it is preferable that the content of tungsten is large from the viewpoint of ensuring high heat resistance and corrosion resistance. However, as taught in Non-Patent Documents 1 and 2, it has been difficult to improve the ductility of the nickel-tungsten alloy when the tungsten content exceeds 2 atomic%.

  An object of the present invention is to provide a nickel tungsten alloy and a contact probe including the same, which are excellent in heat resistance and ductility.

One aspect of the invention includes nickel and tungsten,
The tungsten content is more than 2.0 atomic% and 10.0 atomic% or less,
In an X-ray diffraction (XRD) spectrum, the degree of orientation N ₂₀₀ of the (200) plane relates to a nickel tungsten alloy having N ₂₀₀ > 1.0.

  Another aspect of the present invention relates to a contact probe including the above nickel-tungsten alloy.

  According to the present invention, it is possible to obtain a nickel tungsten alloy that can ensure high ductility and is excellent in heat resistance. Such an alloy is suitable for use in a metal structure that requires elasticity, such as a contact probe.

It is a perspective view showing typically a contact probe concerning one embodiment of the present invention. It is a perspective view which shows typically the contact probe which concerns on other one Embodiment of this invention. It is a top view which shows typically the sample used for the tension test of nickel tungsten alloy. It is a graph which shows the relationship between the tungsten content in the nickel tungsten alloy of an Example, and the particle size of a crystal grain. It is a graph which shows the relationship between the hole petch plot of the nickel tungsten alloy of an Example, and the hole petch of pure nickel. Is a graph showing the relationship between the orientation degree N ₂₀₀ the tungsten content (200) plane in the nickel-tungsten alloy of Examples and Comparative Examples. It is a graph which shows the relationship between the heat processing temperature at the time of heat-processing the nickel tungsten alloy of Example 1, 4, and 5 and the particle size of a crystal grain. It is a graph which shows the relationship between the heat processing temperature at the time of heat-processing the nickel tungsten alloy of Example 5, and micro Vickers hardness. It is a graph which shows the relationship between the tungsten content in the nickel tungsten alloy of an Example, and the current efficiency of a cathode.

[Description of Embodiment of the Invention]
First, the contents of the embodiment of the present invention will be listed and described.
The nickel-tungsten alloy according to an embodiment of the present invention includes nickel and tungsten, and the content of tungsten is more than 2.0 atomic% and not more than 10.0 atomic%. In the XRD spectrum, the (200) plane The degree of orientation N ₂₀₀ is N ₂₀₀ > 1.0. The nickel-tungsten alloy according to the present embodiment is particularly intended for an alloy having a crystal grain size of 100 nm or less formed by an electrolytic deposition method (plating method).

  The nickel tungsten alloy is expected to have improved heat resistance and corrosion resistance compared to nickel metal. However, in practice, as the tungsten content increases, the alloy becomes brittle and inferior in ductility. An alloy with a low tungsten content can ensure a certain degree of ductility, but has insufficient heat resistance and corrosion resistance.

  In the nickel tungsten alloy, the ductility tends to increase as the degree of orientation of the (200) plane in the XRD spectrum increases. However, in the conventional nickel-tungsten alloy, when the tungsten content exceeds 2 atomic%, the degree of orientation of the (111) plane and the (220) plane increases, and it is difficult to improve the degree of orientation of the (200) plane. there were. For this reason, conventionally, in a nickel tungsten alloy, when the tungsten content exceeds 2 atomic%, high ductility cannot be ensured.

In this embodiment, although the tungsten content is as high as more than 2.0 atomic% and not more than 10.0 atomic%, the orientation degree N ₂₀₀ of the (200) plane may be increased to N ₂₀₀ > 1.0. it can. Therefore, the ductility of the nickel tungsten alloy can be improved and embrittlement of the alloy can be suppressed. Moreover, since there is much tungsten content, while being able to ensure the high heat resistance of an alloy, corrosion resistance can also be improved.

Incidentally, the orientation degree N ₂₀₀ of nickel-tungsten alloy is believed to manufacturing method of the alloy is greatly influenced. For example, in the case of forming an alloy by a plating method (electrodeposition method), such as additives and / or temperature of the plating bath it is believed to affect N _200. For example, by using a predetermined amount of a complexing agent such as sodium gluconate as an additive for the plating bath, the degree of orientation N ₂₀₀ in the nickel tungsten alloy can be increased. This is thought to be due to the suppression of side reactions and the suppression of the generation of by-products such as hydrogen. When the production of by-products is suppressed, the crystal grains of the nickel tungsten alloy generated by electrodeposition are easily aligned, and the degree of orientation N ₂₀₀ can be increased. In addition, since by-products such as hydrogen are suppressed from entering the alloy, embrittlement of the alloy can be suppressed. By suppressing the side reaction, the current efficiency of electrodeposition can be increased. However, the additive for the plating bath is not limited to the above.

The degree of orientation N ₂₀₀ is the relative peak intensity I _r0 of the (200) plane of Ni determined from the XRD spectrum database of the relative peak intensity I _r1 of the (200) plane measured by the powder XRD spectrum of the alloy. As a ratio to. Specifically, first, from the XRD spectrum data of Ni in the database, (200) plane peak intensity i ₂₀₀ and (220) plane peak intensity i when (111) plane peak intensity i ₁₁₁ is taken as 100. ₂₂₀ is obtained. _Then, the _{i 200,} by dividing the sum of i _{111, i 200} and _{i 220,} determine the relative peak intensity _{I r0} of (200) plane and Ni. Then determined in a powder XRD spectra of the alloy, of a peak intensity _{I 111} of (111) plane is taken as 100, the peak intensity _{I 220} of the (200) surface ₂₀₀ and the peak intensity _I (220) plane, respectively. The I _200, by dividing the sum of I _{111, I 200} and _{I 220,} determine the relative peak intensity _{I r1} of the (200) plane of the alloy. Then, the degree of orientation N ₂₀₀ is obtained by dividing the peak intensity I _r1 by the peak intensity I _r0 .

  As the XRD spectrum database, for example, an international diffraction data center (ICDD (registered trademark): International Center for Diffraction Data (registered trademark)) database can be used. The XRD spectrum of Ni of ICDD (registered trademark) is JCPDS card 4-0850.

  If the alloy thickness is small, ductility does not appear. Therefore, in order to ensure high ductility, the alloy needs to have a certain thickness. In the present embodiment, the thickness of the alloy can be increased, for example, 100 μm or more, and high ductility can be ensured.

  In addition, the thickness of an alloy means the thickness of the metal structure (for example, a film, a bulk body, etc.) formed with the alloy, and may be an average thickness. In addition, when the metal structure has a constricted portion and the thickness varies, a minimum thickness (such as a minimum thickness of the constricted portion) may be used. The thickness of the alloy formed by plating is a length along the direction of electrodeposition (alloy deposition direction).

The orientation degree N ₂₀₀ may be 1.0 <N _200, but is preferably 1.3 ≦ N ₂₀₀ ≦ 5.0, or 1.5 ≦ N ₂₀₀ ≦ 3.0. When the orientation degree N ₂₀₀ is in such a range, the ductility of the alloy can be further increased.

In the nickel-tungsten alloy, the content of tungsten only needs to exceed 2.0 atomic%, preferably 2.3 atomic% or more or 2.5 atomic% or more, and preferably 2.8 atomic% or more or 3 More preferably, it is 0.0 atomic% or more. The tungsten content is 10.0 atomic percent or less, and may be 8.0 atomic percent or less or 6.0 atomic percent or less. These lower limit values and upper limit values can be arbitrarily combined. Even if the tungsten content in the alloy is 2.3 atomic% to 10.0 atomic%, 2.3 atomic% to 8.0 atomic%, or 2.3 atomic% to 6.0 atomic%, for example. Good.
When the content of tungsten is within such a range, formation of an amorphous phase is suppressed, and it becomes easier to ensure high ductility.

The nickel tungsten alloy preferably has an elongation percentage of 7% or more, more preferably 10% or more or 12% or more when a tensile test is performed at room temperature (25 ° C.). Since the degree of orientation N ₂₀₀ is N ₂₀₀ > 1.0, high ductility can be obtained, so that the alloy exhibits such a high elongation rate even though the content of tungsten is high.

The elongation percentage of the alloy is an elongation percentage when a tensile test is performed using the test piece S shown in FIG. The test piece S is a plate-shaped test piece having a length L ₁ (= 44 mm), a width W (= 10 mm), and a thickness (= 100 μm or more). The test piece S has a grip portion 11 formed at both ends, and a parallel portion 12 formed at the center in the length direction and having a width smaller than that of the grip portion 11. Between the parallel part 12 and the grip part 11, a shoulder part 13 whose width gradually increases from the end of the parallel part 12 toward the grip part 11 is formed. Formed on the end portion of the specimen S, the length L ₂ of the portion of the width W is 10 mm. In the parallel portion 12, two mark points 14 are marked at symmetrical positions with respect to the center in the length direction of the test piece S. A marking line 15 parallel to the length direction of the test piece S is marked between the two gauge points 14. The distance D between the two gauge points 14 is 12 mm. The radius R of the shoulder 13 is 7.5 mm.

The tensile test can be performed according to JIS Z 2241. Specifically, one grip portion 11 of the test piece S can be fixed to a tensile tester (for example, a universal tester manufactured by Instron) and the other grip portion 11 can be pulled. At this time, the test piece S may be pulled at a constant strain rate. The length of the marking line 15 at the time when the maximum elongation was shown in the elastic region was measured, and the ratio (%) of the maximum elongation when the length of the marking line 15 before the tensile test was taken as 100% was calculated as follows. Elongation rate. If the strain rate at the time of pulling a test piece with a tensile tester is the strain rate of a general tensile test (for example, 10 ⁻⁵ s ⁻¹ to 10 ⁻⁴ s ⁻¹ ), the elongation rate is the strain rate. Almost no dependence. The strain rate is obtained by dividing the tensile rate (mm / min) when the test piece is pulled by the initial length (mm) of the parallel portion 12.

  The nickel tungsten alloy is suitable for use as a metal structure (or bulk body) having a three-dimensional structure. Nickel tungsten alloy is particularly suitable for use as a contact probe that requires such characteristics because it has high ductility, suppression of embrittlement, and high heat resistance. By using the nickel-tungsten alloy described above for the contact probe, it is possible to suppress deterioration of mechanical properties and deformation even under a high temperature environment. In addition, it is possible to suppress a decrease in position accuracy and instability of the pressing load due to deformation.

[Details of the embodiment of the invention]
Specific examples of the nickel tungsten alloy according to the embodiment of the present invention will be described below with reference to the drawings as appropriate. In addition, this invention is not limited to these illustrations, is shown by the attached claim, and is intended that all the changes within the meaning and range equivalent to the claim are included. .

(Nickel tungsten alloy)
In the nickel-tungsten alloy, tungsten (W) is preferably present as a solid solution with nickel (Ni). In this case, the crystal grain size of the alloy tends to be small, and high ductility is easily secured.

  The alloy may contain an element (third element) other than Ni and W. Examples of such a third element include typical nonmetallic elements such as hydrogen, carbon, nitrogen, and oxygen, and metallic elements other than Ni and W. The alloy may contain one kind of third element, or may contain two or more kinds. Although it does not restrict | limit especially as a metallic element (it is also called 3rd metallic element) as a 3rd element, For example, periodic table group 6 elements (however, except W), such as chromium and molybdenum, etc. are mentioned. The content of the third element in the alloy is, for example, 0.1 atomic% or less. When the alloy contains carbon, high strength is easily obtained. From the viewpoint of ensuring both high strength and high ductility, the carbon content in the alloy is, for example, 0.1 atomic percent or less, and preferably 0.04 atomic percent or less.

Nickel tungsten alloy contains nano-sized crystal grains and can also be referred to as nanocrystalline alloy. The crystal grain size of the alloy is, for example, 10 nm to 100 nm, preferably 10 nm to 50 nm, and more preferably 10 nm to 30 nm. When the crystal grains have such a particle size, it is easy to ensure high strength while ensuring high ductility of the alloy.
In addition, the grain size of a crystal grain is a grain size calculated | required using the Scherrer formula from the peak width of the peak of the (111) plane of the XRD pattern of an alloy.

The nickel tungsten alloy may contain hydrogen generated by a side reaction of the plating process. However, in this embodiment, since side reactions are greatly suppressed, the hydrogen content in the alloy can be significantly reduced. The hydrogen content in the alloy is, for example, 0.03 atomic% or less, and preferably 0.02 atomic% or less.
The hydrogen content in the alloy can be determined, for example, by an inert gas melting-thermal conductivity method. Argon or nitrogen is used as an inert gas (carrier gas) for melting the alloy.

(Metal structure)
The alloy according to the present embodiment is suitable for use as a metal structure (or bulk body) having a three-dimensional structure because it is excellent in heat resistance and corrosion resistance and has high ductility. It can also be used as a fine metal structure having spring properties. The spring property is a property of deforming when a force is applied to a certain material and restoring to the same original shape without deformation when the force is removed. The spring property is exhibited by the elasticity of the material.

  The fine metal structure having spring properties (hereinafter simply referred to as a metal structure) is not particularly limited. Examples include contact probes, connectors such as spring connectors and ring connectors, microactuators, fine gears, and turbine blades.

1a and 1b are perspective views schematically showing contact probes according to different embodiments, respectively. The contact probe 10 includes a support portion 1, a spring portion 2 extending from the support portion 1, and a tip portion 3 formed on the opposite side of the spring portion 2 from the support portion 1. The spring property of the contact probe 10 is mainly provided by the spring portion 2 and is exhibited by the elasticity of the spring portion 2. The maximum length of the contact probe 10 is indicated by L _max and the minimum length is indicated by L _min . The minimum length L _min of the contact probe 10 corresponds to the thickness of the contact probe 10.

  The metal structure such as the contact probe only needs to contain the above-described nickel-tungsten alloy, and may be entirely formed of an alloy or may partially contain the alloy. In particular, it is preferable that the portion (for example, the spring portion 2 of the contact probe 10) that gives the spring property of the metal structure is made of an alloy. The metal structure may include a coat layer that covers at least a part of the metal structure in order to increase conductivity.

  The shape of the metal structure is not particularly limited, and can be set as appropriate according to the application. For example, in the case of a contact probe, the shape may be a vertical type as shown in FIG. 1a or a cantilever type as shown in FIG. 1b. In the contact probe 10, the support portion 1, the spring portion 2, and the distal end portion 3 may be integrally molded, or may be joined by welding or the like after molding each member. In the case of a connector, the shape is, for example, a ring shape or a spiral shape.

The magnitude | size of a metal structure is not specifically limited, It can set suitably according to a use. In the contact probe, the maximum length L _max is, for example, 100 μm to 10 mm, and the minimum length L _min is, for example, 100 μm to 200 μm.

(Alloy manufacturing method)
The method for producing the nickel-tungsten alloy according to the present embodiment is not particularly limited as long as an alloy having a tungsten content and an orientation degree N ₂₀₀ in the above ranges can be obtained. For example, the nickel-tungsten alloy can be obtained by an electrodeposition method. . More specifically, the manufacturing method of an alloy includes the process of electrodepositing an alloy on the surface of a base material in a plating bath. In the case of electroforming, an alloy production method includes a preparation step of preparing a base die as a base material, an electroforming step of electrodepositing (or electrodeposition) metal on the base die, And a peeling step of peeling the electrodeposition layer (plated product). The manufacturing method may further include a step of heat treating the alloy. Electroforming is a kind of electroplating technology. Electrodeposited metal ions are electrodeposited onto the surface of the master (master), and then the electrodeposition layer is peeled off to faithfully follow the master. This is a method for manufacturing a metal product.

(Electrodeposition process (or electrodeposition process))
In the electrodeposition step, a nickel (tungsten) alloy is electrodeposited on the surface of the substrate by immersing the substrate (or matrix) in a plating bath and applying a current.
In order to increase the degree of orientation N ₂₀₀ despite the high tungsten content in the alloy, the composition and / or electrodeposition conditions of the plating bath (electrodeposition bath) used for electrodeposition are important. Among these, the type and amount of additives added to the plating bath, the temperature of electrodeposition, the bath flow, and the like greatly affect the degree of orientation of the alloy. For example, the degree of orientation N ₂₀₀ can be easily increased by making the bath flow impinge at a certain angle (for example, 60 ° to 90 °) rather than being parallel to the main surface of the substrate. In particular, it is preferable that the bath flow strikes the main surface of the substrate perpendicularly or at an angle close thereto (for example, 80 ° to 90 °).

  The plating bath used for electrodeposition (or electrodeposition) is preferably a sulfamic acid bath. An alloy obtained using a sulfamic acid bath is suitable for electroforming because it has a low internal stress and is easily peeled off. The sulfamic acid bath contains a nickel source such as nickel sulfamate, but also contains a tungsten source and additives.

Examples of the nickel source include nickel sulfamate, nickel chloride, and nickel metal. In a sulfamic acid bath, the nickel source includes at least nickel sulfamate.
The concentration of nickel sulfamate in the plating bath is preferably 50 to 700 g / L, and more preferably 100 to 500 g / L. If the concentration of nickel sulfamate is in this range, an alloy having a large thickness can be easily obtained, and precipitation of by-products such as nickel hydroxide can be suppressed while securing a certain degree of precipitation rate.

  Examples of the tungsten source include tungstates such as sodium tungstate and potassium tungstate. Each of the nickel source and the tungsten source may be used alone or in combination of two or more.

  The concentration of the tungsten source in the plating bath is, for example, 10 g / L to 60 g / L, preferably 10 g / L to 55 g / L, and more preferably 12 g / L to 50 g / L. If the concentration of the tungsten source is within this range, the content of tungsten in the alloy can be easily adjusted to the above range.

  Examples of the additive include a complexing agent (chelating agent), a brightening agent, a pH buffering agent, a pit preventing agent (surfactant), a stress adjusting agent, and a hardness increasing agent. An additive can be used individually by 1 type or in combination of 2 or more types.

  The complexing agent forms a complex with the metal ion in the plating bath and stabilizes it. Examples of the complexing agent include carboxylic acids such as propionic acid, citric acid, gluconic acid, and ethylenediaminetetraacetic acid or salts thereof. A complexing agent may be used individually by 1 type, and may be used in combination of 2 or more type. Among the complexing agents, monocarboxylic acid or a salt thereof is preferable.

Examples of the monocarboxylic acid include gluconic acid and propionic acid. Examples of the salt of monocarboxylic acid include inorganic salts such as sodium salt, potassium salt and ammonium salt. Of these, sodium gluconate is preferably used as the complexing agent. By using sodium gluconate, the degree of orientation N ₂₀₀ on the (200) plane can be increased while maintaining a high tungsten content in the alloy.

The concentration of the complexing agent such as sodium gluconate in the plating bath is preferably 10 g / L to 60 g / L, more preferably 10 g / L to 55 g / L or 10 g / L to 50 g / L. . By concentration of the complexing agent is within such a range, while maintaining a high tungsten content in the alloy, it is possible to increase the degree of orientation N ₂₀₀ of (200) plane.

Molar ratio of tungsten source of the complexing agent (= complexing agent / tungsten source) is, for example, 0.2 to 2.0, from easily viewpoint enhance orientation _{N 200,} 0.3 to 1.7 It is preferable that it is 0.5-1.5.

  The brightener smoothes the surface of the electrodeposition layer. An organic substance is used as the brightener. Examples of the organic substance include saccharin, sodium saccharin, sodium naphthalene disulfonate, sodium allyl sulfonate, and butynediol. A brightener can be used individually by 1 type or in combination of 2 or more types.

  The pH buffering agent prevents precipitation of metal ions, and those used for the sulfamic acid bath can be used without particular limitation. Examples of the pH buffering agent include boric acid, acetic acid, and / or citric acid. As the surfactant, the stress adjusting agent, and the hardness increasing agent, those used in the sulfamic acid bath can be used without any particular limitation. Examples of the surfactant include sodium dodecyl sulfate and / or polyoxyethylene alkyl ether. The amounts of pH buffering agent, surfactant, stress adjusting agent, hardness increasing agent and the like can be determined as appropriate.

  The pH of the sulfamic acid bath is preferably 3.5 to 5, and more preferably 3.5 to 4.5. When the pH is in such a range, precipitation of by-products such as nickel hydroxide can be suppressed while securing high current efficiency to some extent. The pH may be adjusted by adding sulfuric acid, sodium hydroxide or the like.

The plating bath includes a cathode and an anode.
A conductive substrate is used as the cathode. Examples of the conductive substrate include a metal substrate including copper, nickel, stainless steel, or a silicon substrate obtained by sputtering a metal material such as titanium or chromium.

  As the anode, a metal plate and / or a metal rod is used. Examples of the metal constituting the metal plate or metal rod include nickel and tungsten. For example, a metal plate or metal rod containing nickel and a metal plate or metal rod containing tungsten may be used in combination.

From the viewpoint of easily obtaining a uniform alloy while securing a high electrodeposition rate to some extent, the cathode current density at the time of plating is, for example, 0.1 A / dm ^{2 to} 20 A / dm ² , and 1 A / it may be a dm ² ~15A / dm ^2. The temperature of the plating bath is, for example, 30 ° C to 60 ° C, and may be 40 ° C to 60 ° C. When the temperature of the plating bath is in such a range, the composition of the plating bath is easily stabilized while securing a somewhat high electrodeposition rate. From the viewpoint of increasing N ₂₀₀ , the temperature is particularly preferably 45 ° C. to 50 ° C.
What is necessary is just to set suitably the time which performs a plating process so that the thickness of a desired electrodeposition layer may be obtained.

(Preparation process of master mold)
In the electroforming application, a matrix serving as a base material is prepared prior to the electrodeposition process (or electroforming process). The mother mold is a mold having a recess having the same shape as an alloy (metal structure) having a desired shape, and a nickel tungsten alloy is deposited (electrodeposited) on the recess. The material of the mother die is not particularly limited, and may be made of metal or resin. Especially, it is preferable that it is resin-made from the point that peeling with an electrodeposition layer is easy in a subsequent peeling process. In the case of using a resin mother die, the conductive treatment is performed on the mother die. The conductive treatment may be performed by forming a conductive film such as indium tin oxide (ITO) on the surface of the mother mold, or may be performed by attaching the mother mold to a conductive substrate.

  A resin matrix can be obtained, for example, by forming irregularities having the same shape as the desired shape of the metal structure on the resin layer formed on the conductive substrate by lithography. The conductive substrate functions as a cathode in the electrodeposition step (electroforming step), and the conductive substrate exemplified for the electrodeposition step is used.

  The material of the resin layer is not particularly limited as long as it is a resin that is cured by light energy. For example, acrylic resin, photosensitive polyimide resin, and the like can be given. What is necessary is just to set the thickness of a resin layer suitably according to the thickness (minimum thickness etc.) of the target alloy (metal structure).

(Peeling process)
In the electroforming application, the matrix and the electrodeposition layer (metal structure) are peeled off after the electrodeposition step (or electroforming step). The peeling method is not particularly limited. From the viewpoint of easily maintaining the shape of the fine electrodeposition layer, the electrodeposition layer may be peeled from the matrix by dry etching or wet etching.

  Next, the conductive substrate is removed by wet etching or mechanical processing, whereby an alloy (metal structure) having a desired shape can be obtained. A coating layer may be formed on the obtained alloy (metal structure) as necessary.

(Heat treatment process)
When the electrodeposition layer is formed in the electrodeposition step and then heat treatment (solution heat treatment) is performed, the heat resistance of the alloy can be further improved. The heat treatment temperature is, for example, 300 ° C. or higher, and may be 400 ° C. or higher. When heat treatment is performed at such a temperature, the solid solution of the nickel-tungsten alloy can be further advanced, and the effect of improving the heat resistance is easily obtained.

  The heat treatment time can be appropriately set, but from the viewpoint of further improving the heat resistance of the alloy, it is preferably 0.5 hours or more, and more preferably 1 hour or more. The heat treatment may be performed after the electrodeposition layer is formed, and may be performed after the peeling step in electroforming applications.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example and a comparative example, this invention is not limited to a following example.

<< Examples 1-7 >>
An alloy was formed by electrodeposition in a plating bath based on nickel sulfamate. A nickel plate (purity of nickel: 99.9% by mass) and a tungsten rod (purity of tungsten: 99.9% by mass) are used as the anode provided in the plating bath, and a copper plate (copper purity: 99.9%) is used as the cathode. Mass%) was used. The cathode was masked so that the exposed portion had a predetermined size and was subjected to a rinsing process.

  Plating bath A using nickel sulfamate, sodium tungstate, nickel chloride, propionic acid (complexing agent), sodium gluconate (complexing agent), sodium saccharin (brightening agent), and sodium lauryl sulfate (surfactant) -G was prepared. The specific plating bath composition is shown in Table 1. Table 1 also shows the molar ratio (G / T ratio) of sodium gluconate to sodium tungstate and pH in the plating bath.

Then, electrodeposition was performed in a 50 ° C. plating bath under the condition of a cathode current density of 3 A / dm ² to form a nickel tungsten alloy on the cathode surface. At this time, the bath flow of the plating bath was perpendicular to the main surface of the electrode. As the alloy, a coating (electrodeposition layer) having a thickness of about 300 μm and a bulk body having a thickness of about 1 mm were prepared. Examples using plating baths A to G are referred to as Examples 1 to 7, respectively.

<< Comparative Example 1 >>
A nickel-tungsten alloy as in Example 1 except that a plating bath (temperature: 50 ° C.) having the same composition as the plating bath A was used and the bath flow of the plating bath was parallel to the main surface of the electrode. Formed. The tungsten content in the alloy was 1.9 atomic%.

<< Comparative Example 2 >>
A plating bath I was prepared in the same manner as in Example 1 except that the concentration of saccharin sodium in the plating bath A was changed to 5.0 g / L. And using the plating bath I (temperature 45 degreeC),
A nickel tungsten alloy was formed in the same manner as in Example 1. The tungsten content in the alloy was 1.5 atomic%.

<< Comparative Example 3 >>
A nickel-tungsten alloy was formed in the same manner as in Example 1 by using a plating bath (temperature: 50 ° C.) having the same composition as the plating bath I in Comparative Example 2. The tungsten content in the alloy was 1.0 atomic%.

<< Comparative Example 4 >>
Using a plating bath (temperature 55 ° C.) having the same composition as the plating bath I of Comparative Example 2, a nickel tungsten alloy was formed in the same manner as in Example 1. The tungsten content in the alloy was 1.5 atomic%.

<< Comparative Example 5 >>
A nickel-tungsten alloy was prepared in the same manner as in Example 1 by using a plating bath (temperature 60 ° C.) having the same composition as the plating bath A in Example 1. The tungsten content in the alloy was 5.3 atomic%.

<Evaluation>
The following evaluation was performed using the obtained alloy.
(A) Tungsten content in alloy The surface of the alloy was mirror-polished and subjected to composition analysis to determine the tungsten content (atomic%) in the alloy. For the analysis, an SEM-EDS [Scanning Electron Microscope (SEM) equipped with an Energy Dispersive X-ray Spectroscopy (EDS)] was used. The analysis was performed under conditions of an applied voltage of 25 V and an emission of 10 μA.

(B) XRD analysis and (200) plane orientation N ₂₀₀
The mirror-polished alloy was subjected to powder XRD analysis using CuKα rays. The analysis was performed for a range of 30 ° to 90 ° under the conditions of a voltage of 40 kV and a current of 40 mA. From the obtained XRD pattern and Scherrer's formula, the grain size of the crystal grains of the alloy was calculated. The half width of the XRD peak was calculated by smoothing by integral intensity calculation, and removing the background and CuKα components at an intensity ratio of 0.5 using a weighted average and the Sonneveld-Visser method.
Further, the XRD patterns, by the method described above, was determined orientation _{N 200} of (200) plane.

(C) Tensile test A test piece shown in FIG. 2 was produced by subjecting an alloy bulk body to electrical discharge machining. Using the obtained test piece, a tensile test was performed according to the procedure described above to determine the elongation percentage (%) of the alloy. Moreover, the tensile strength (MPa) at the time of showing the maximum elongation in the elastic region was determined.

(D) Heat resistance test First, the micro Vickers hardness of the alloy whose surface was mirror-polished was measured using a micro Vickers hardness tester under conditions of a load of 500 g and a load time of 10 seconds.
The alloy was heat treated (solution heat treatment) at 300 ° C. for 1 hour, the micro Vickers hardness was measured in the same manner as described above, and the grain size of the crystal grains was measured in the same manner as in (b) above. Moreover, the temperature of the heat treatment was changed, and the hardness and the grain size of the crystal grains were measured.

(E) Current efficiency of cathode The amount of deposited alloy was determined from the mass change of the cathode before and after electrodeposition. The ratio (%) of the deposited amount to the theoretical deposited amount was calculated and evaluated as the current efficiency of the cathode. The theoretical amount of precipitation was determined from the amount of electricity required for electrodeposition.

  The relationship between the tungsten content and the grain size of the grains in the alloy is shown in FIG. FIG. 3b shows the relationship between the hole-petch plot of the alloy and the hole-petch of pure nickel. As shown in FIG. 3a, in the example alloys, the grain size of the grains decreased as the tungsten content increased. Further, as shown in FIG. 3b, the hardness of the alloy of the example increased as the grain size of the crystal grains decreased. In addition, the hardness of the alloy of the example was increased as compared with metallic nickel.

FIG. 4 is a graph showing the relationship between the tungsten content and the degree of orientation N ₂₀₀ of the (200) plane of the alloy. In the plating baths D, E, and F, the tungsten concentration in the plating bath is the same. However, since the concentration of sodium gluconate are different, it can be seen that the tungsten content and the degree of orientation N ₂₀₀ is different alloys obtained. Further, in the comparative example, when the orientation degree N ₂₀₀ is larger than 1.0, the tungsten content in the alloy decreases, and when the tungsten content increases, the orientation degree N ₂₀₀ tends to become smaller than 1. In the figure, Comparative Examples 1 to 3 are indicated by black circles, and Comparative Examples 4 and 5 are indicated by black triangles.

  Table 2 shows the results of the tensile test and the micro Vickers hardness test of the alloys of Examples 3 and 7. About Example 7, it evaluated about three test pieces produced similarly (G-1, G-2, and G-3). In Table 2, “hardness” is micro Vickers hardness.

  As shown in Table 2, the alloys of the examples had high elongation and tensile strength and were excellent in Vickers hardness. On the other hand, in the comparative example, the alloy was too brittle and the tensile test could not be performed.

  FIG. 5 is a graph showing the relationship between the heat treatment temperature and the crystal grain size when the alloys obtained in Examples 1, 4 and 5 are heat treated. FIG. 6 is a graph showing the relationship between the heat treatment temperature and Micro Vickers hardness when the alloy obtained in Example 5 is heat treated. As FIG. 5 shows, it is suppressed that the particle size of the crystal grain by heat processing becomes large as the tungsten content in an alloy increases. Further, from FIG. 6, in Example 5, even when a heat treatment at 400 ° C. was performed, the same hardness as that before the heat treatment was obtained, and high heat resistance was shown.

  FIG. 7 is a graph showing the relationship between the tungsten content in the alloy and the current efficiency of the cathode. From FIG. 7, the current efficiency of the cathode tends to decrease as the tungsten content in the alloy increases. However, in any of the examples, a high current efficiency exceeding 70% was obtained.

  The nickel-tungsten alloy according to the present invention is excellent in heat resistance and ductility, and can be used for various applications such as electronic devices and measuring devices for electronic devices.

1: support part, 2: spring part, 3: tip part, 10: contact probe, L _max : maximum length, L _min : minimum length, S: test piece, 11: grip part, 12: parallel part, 13 : Shoulder, 14: Mark, 15: Mark line, L ₁ : Length of test piece, W: Width of test piece, D: Distance between two mark 14, R: Radius of shoulder 13

Claims (6)

Including nickel and tungsten,
The tungsten content is more than 2.0 atomic% and 10.0 atomic% or less,
In the X-ray diffraction spectrum, the degree of orientation N ₂₀₀ on the (200) plane is N ₂₀₀ > 1.0, which is a nickel tungsten alloy.   The nickel tungsten alloy according to claim 1, wherein the thickness is 100 µm or more. The nickel-tungsten alloy according to claim 1, wherein the degree of orientation N ₂₀₀ is 1.5 ≦ N ₂₀₀ ≦ 3.0.   The nickel-tungsten alloy according to any one of claims 1 to 3, wherein the tungsten content is 2.3 atomic% to 8.0 atomic%.   The nickel-tungsten alloy according to any one of claims 1 to 4, which has an elongation of 7% or more when a tensile test is performed at 25 ° C.   A contact probe comprising the nickel tungsten alloy according to claim 1.

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