JP2010189685A - Microcrystal-amorphous coexisting gold alloy and plated film, plating liquid therefor and method of forming plated film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microcrystal-amorphous coexisting gold alloy plated film excellent in electrical characteristics and mechanical characteristics and to provide a plating method of the microcrystal-amorphous coexisting gold alloy plated film. <P>SOLUTION: Properties combining advantage of a crystal structure with that of an amorphous structure can be obtained by allowing a micro crystal phase and an amorphous phase to coexist so as to obtain a volume fraction of crystal phase of 10 to 90%. The microcrystal-amorphous coexisting gold alloy plated film is characterized in that an average particle diameter of the microcrystal is 30 nm or less, a volume fraction of the microcrystal is 10 to 90%, a Knoop hardness is Hk180 or more and a specific resistance is 200μΩ cm or less. The microcrystal-amorphous coexisting gold alloy plated film has an improved hardness and wear-resistance while maintaining specific resistance and chemical stability of gold of its own in such an extent as not to be practically out of the question and is useful for contact material of electric and electronic parts such as relay. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  INDUSTRIAL APPLICABILITY The present invention is useful as a plating film for terminals of electronic equipment parts, and has an electric property and an electrical property capable of forming a fine crystal-amorphous mixed gold alloy plating film excellent in electrical characteristics and mechanical characteristics, and this fine crystal-amorphous mixed gold alloy plating film. The present invention relates to a plating solution and an electroplating method using the electroplating solution.

  Gold plating films called hard gold plating films are currently widely used as electrical contact materials for parts that require high reliability, especially in connectors for electrical and electronic parts, small electromechanical relays, and printed wiring boards. ing. The hard gold plating film is obtained by adding cobalt, nickel or the like to gold, and improves the hardness of the film without deteriorating the good conductivity and chemical stability of gold. This hard gold plating film has a fine structure in which gold fine crystals (20 to 30 nm) are aggregated, and this fine structure is at least required to obtain the wear resistance required for contact materials. It is considered that the hardness (Knoop hardness is about Hk 170) can be obtained.

  On the other hand, with the recent miniaturization of electronic components, the size of electrical contacts has also been miniaturized, but the plating film formed at such microcontacts has also been reduced in size and thickness to obtain high wear resistance. There is a need for further improvement in hardness.

  Also, in the near future, the size of the contact is considered to approach the size of the fine crystal of the hard gold plating film described above, and when the hard gold plating film as described above is formed on such a fine contact Because the absolute number of fine crystals constituting the film is reduced, it is expected that the durability equivalent to the case where a hard gold plating film is formed on a contact having a size that is currently applied will not be obtained. The Accordingly, the present inventors have invented an amorphous gold alloy plating film formed of a homogeneous amorphous phase having no fine crystals (for example, Patent Documents 6 to 8). However, it can be said that there is still room for improvement in order to obtain a material with improved hardness while maintaining the good resistivity and chemical stability inherent in gold to such an extent that they do not become a practical problem.

The prior art document information related to the present invention includes the following.
JP-A-60-33382 Japanese Patent Laid-Open No. 62-290893 Japanese Patent No. 3454724 Japanese Patent No. 3983207 JP 2004-300483 A JP 2006-241594 A JP 2007-92157 A JP 2007-169706 A

Satoshi Kawai, “Study on deposition structure of gold-nickel alloy plating”, Metal Surface Technology, 1968, Vol. 19, no. 12, p. 487-491 Yasuo Shimizu et al., "Electron microscopic study on microstructure and phase of electrodeposited Au-Ni alloy", Metal Surface Technology, 1976, Vol. 27, no. 1, p. 20-24 Toru Watanabe, “Fine plating plating structure control technology and its analysis method”, Technical Information Association, February 2002, p256-262 Takashi Omi et al., “High W content and film properties of Ni-W alloy plating film”, Metal Surface Technology, 1988, Vol. 39, no. 12, p. 809-812 Toru Watanabe, “Mechanism of Amorphous Alloy Formation by Plating”, Surface Technology, 1989, Vol. 40, no. 3, p. 21-26

  The present invention has been made in view of the above circumstances, and has a fine crystal-amorphous mixed gold alloy plating film excellent in wear resistance and having good conductivity and chemical stability and improved hardness, and this fine crystal-amorphous An object is to provide an electroplating solution capable of forming a mixed gold alloy plating film and an electroplating method using the electroplating solution.

  The present inventor has made extensive studies to achieve the above object, and as a fine structure of a plating film that does not lower the hardness even with a minute contact, the amorphous phase structure is more gold than the crystalline structure. Although the hardness and wear resistance can be improved while maintaining good specific resistance and chemical stability at a level that does not cause any practical problems, the mean free path of electrons is shorter than that of crystal films, so Research was conducted with the expectation that cracks would easily occur in the plating film due to low conductivity and internal stress, and contained gold cyanide salt, nickel salt and / or cobalt salt at a predetermined concentration. Furthermore, by electroplating using an electroplating solution having good liquid stability containing a complexing agent such as organic acid, inorganic acid or salt thereof and ammonia or ammonium ion. Surprisingly, a microcrystalline-amorphous mixed gold alloy plating film formed by mixing a microcrystalline phase and an amorphous phase can be obtained, and this film has a good resistivity value and chemical stability inherent to gold. As a result of discovering that the hardness is improved while maintaining a practically useful level, and further researching it, the present invention has been completed.

That is, the present invention provides (1) a fine crystal-amorphous mixed gold alloy plating film characterized by being formed by mixing a fine crystal phase and an amorphous phase, and (2) a gold cyanide salt having a gold standard of 0 A concentration of 0.0001-0.4 mol / dm ³ , a nickel salt concentration of 0.001-0.5 mol / dm ^{3 on} a nickel basis, and / or a cobalt salt basis of 0.001-0.5 mol / dm ³ on a cobalt basis. Preferably, a complexing agent such as an organic acid, an inorganic acid or a salt thereof is added at a concentration of 0.001 to 2.0 mol / dm ³ , and ammonia or ammonium ions are added at a concentration of 0.001 to 5.0 mol / liquid stability good electroplating solution, characterized in that it contains a concentration of dm ^3, and (3) the electroplating solution to be plated onto the fine crystals with - amorphous mixed gold alloy Providing an electroplating method and forming the Kki film.

  The fine crystal-amorphous mixed gold alloy plating film of the present invention is formed by a mixture of a fine crystal phase and an amorphous phase, and as a result, the practically useful resistivity value and chemical stability of gold are practically useful. Therefore, it is useful as a contact material for electrical and electronic parts such as relays. In general, in the case of a crystal film composed of fine crystals, if the size of the constituting crystal grains is reduced, the hardness increases up to a certain limit (for example, about 4 nm in the case of nickel), but if the crystal grains are further reduced, the hardness is increased. It is known to decline. Although there is no example of actual measurement whether or not the general theory can be applied to gold, according to the present invention for realizing a microcrystalline-amorphous mixed crystal film for the first time in gold, a fine crystal-amorphous mixed gold alloy plating film is obtained as described above. As we have confirmed for the first time that it is fully applicable as a micro-contact material for electrical and electronic parts such as connectors and relays because it solves all the problems, has high electrical conductivity, and does not easily crack. is there.

It is a figure which shows the XRD pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Examples 1, 2, 3, 4, and 5 and the gold alloy plating film obtained in Comparative Examples 1 and 2. It is a figure which shows the TEM image (100,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 1. FIG. It is a figure which shows the TEM image (1 million times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 1. FIG. It is a figure which shows the THEED pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 1. FIG. It is a figure which shows the TEM image (500,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 2. FIG. It is a figure which shows the TEM image (1 million times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 2. FIG. It is a figure which shows the THEED pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 2. It is a figure which shows the TEM image (300,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 3. FIG. It is a figure which shows the TEM image (1 million times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 3. It is a figure which shows the THEED pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 3. It is a figure which shows the TEM image (200,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 4. It is a figure which shows the TEM image (700,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 4. FIG. It is a figure which shows the THEED pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 4. It is a figure which shows the TEM image (400,000 times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 5. FIG. It is a figure which shows the TEM image (1 million times) of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 5. It is a figure which shows the THEED pattern of the fine crystal-amorphous mixed gold alloy plating film obtained in Example 5. It is a figure which shows the TEM image (1,000,000 times) of the amorphous gold alloy plating film obtained by the comparative example 1. It is a figure which shows the THEED pattern of the amorphous gold alloy plating film obtained by the comparative example 1.

Hereinafter, the present invention will be described in more detail.
The fine crystal-amorphous mixed gold alloy plating film of the present invention is formed by mixing a fine crystal phase and an amorphous phase.

  The fine crystal-amorphous mixed gold alloy plating film of the present invention contains nickel and / or cobalt in gold, and the fine structure is a structure in which a fine crystal phase and an amorphous phase are mixed. High hardness is achieved with good specific resistance and chemical stability compared to an amorphous gold alloy plating film with an amorphous structure. Such a structure in which a fine crystal phase and an amorphous phase are mixed can be confirmed by an X-ray diffraction (XRD) pattern, a transmission electron microscope (TEM) image, and a transmission high energy electron diffraction (THEED) image.

  The fine crystal-amorphous mixed gold alloy plating film of the present invention preferably has an average particle size of fine crystals of 30 nm or less, particularly 20 nm or less, and more preferably 15 nm or less from the viewpoint of maintaining high hardness.

  In addition, the fine crystal-amorphous mixed gold alloy plating film of the present invention has the viewpoint of maintaining the original characteristics of gold (good resistivity and chemical stability) or high hardness not found in conventional gold or gold alloy plating films. Therefore, the volume fraction of fine crystals is preferably 10 to 90%, particularly preferably 15 to 60%.

  According to the present invention, the Knoop hardness is Hk 180 or more, particularly Hk 220 or more, further Hk 300 or more, particularly Hk 350 or more, and the specific resistance is 200 μΩ · cm or less, particularly 150 μΩ · cm or less, particularly 100 μΩ · cm or less. A fine crystal-amorphous mixed gold alloy plating film having high hardness and specific resistance can be obtained. Further, in the fine crystal-amorphous mixed gold alloy plating film of the present invention, the structure in which the fine crystal phase and the amorphous phase are mixed is changed by annealing treatment (maintained for 1 hour) at 300 ° C. or lower (that is, crystallization occurs). The average grain size and volume fraction of the fine crystals will not increase).

  The fine crystal-amorphous mixed gold alloy plating film of the present invention has a high hardness not found in conventional gold or gold alloy plating films, together with its excellent specific resistance and chemical stability. It is effective as a conduction contact for terminals of electrical and electronic parts such as breakers, thermostats, relays, timers, various switches, and printed wiring boards.

The fine crystal-amorphous mixed gold alloy plating film of the present invention has a composition formula: Au _100-xy M _{x Cy} (where Au or M is a main component and inevitable impurities may be contained, and M is Ni And / or Co and C is carbon, which can be represented by 1 atomic% ≦ x ≦ 80 atomic%, 1 atomic% ≦ y ≦ 30 atomic%).

  The fine crystal-amorphous mixed gold alloy plating film of the present invention can be formed by electroplating using an electroplating solution containing a gold cyanide salt, a nickel salt and / or a cobalt salt.

The electroplating solution contains a gold cyanide salt, a nickel salt and / or a cobalt salt. Specific examples of the gold cyanide salt include nickel gold cyanide, sodium gold cyanide, lithium gold cyanide and the like. Specific examples of the salt include nickel sulfate and nickel nitrate, and specific examples of the cobalt salt include cobalt sulfate and cobalt nitrate. The gold cyanide salt concentration in the plating solution is 0.0001 to 0.4 mol / dm ³ , preferably 0.001 to 0.2 mol / dm ³ , more preferably 0.01 to 0.1 mol / dm ^{3 on a} gold basis. , nickel salt concentration 0.001 to 0.5 mol / dm ³ nickel basis, preferably 0.01~0.2mol / dm ^3, the cobalt salt concentration is 0.001 to 0.5 mol / ^dm 3 of cobalt basis, preferably from 0.01~0.2mol / dm ^3. The molar ratio [(Ni + Co) / Au] of gold and nickel and / or cobalt in the plating solution is preferably 0.01 to 300, more preferably 1 to 30.

The electroplating solution preferably further contains a complexing agent. Examples of the complexing agent include organic acids, inorganic acids or salts thereof having a complexing action and pH buffering action. Examples of organic acids, inorganic acids and salts thereof include citric acid, tartaric acid, malic acid, pyrophosphoric acid, phosphorus. Examples include acids, sulfamic acids, and sodium salts, potassium salts, and ammonium salts thereof. The concentration of the complexing agent in the plating solution is preferably 0.001 to 2.0 mol / dm ³ , particularly 0.01 to 1.0 mol / dm ³ , particularly preferably 0.1 to 0.3 mol / dm ³ . The ratio of complexing agent to nickel and / or cobalt in the plating solution [complexing agent / (Ni + Co)] is preferably in the range of 0.01 to 100, more preferably 1 to 4 as a molar ratio.

The electroplating solution preferably further contains ammonia or ammonium ions. Specific examples of ammonia or ammonium ions include aqueous ammonia, ammonium sulfate, and ammonium salts of complexing agents. The concentration of ammonia or ammonium ions in the plating solution is preferably 0.001 to 5.0 mol / dm ³ , particularly preferably 0.01 to 2.0 mol / dm ³ . This ammonia is greatly involved in the crystal state of the plating film, such as the average grain size of the crystal phase and the volume fraction of fine crystals (or amorphous), and the stability of the plating bath.

  The pH of the electroplating solution is preferably 3 to 11, particularly preferably 5 to 9, particularly around pH 6. For pH adjustment, a conventionally known pH adjuster such as aqueous ammonia or potassium hydroxide can be used.

  Further, this electroplating solution has no significant influence on the film physical properties (volume fraction and average particle diameter of fine crystals, peak half width of XRD pattern, Knoop hardness, specific resistance) and film composition of the plating film. If necessary, surfactants, solvents, etc. for purposes such as improving glossiness, preventing pits, imparting conductivity, imparting buffering properties, expanding the usable current density range, promoting precipitation rate, improving heat resistance, improving wettability, etc. (See, for example, JP-A Nos. 7-11476, 2004-76026, and 2006-37164).

The electroplating conditions are not particularly limited, but the plating temperature is preferably 20 to 95 ° C, particularly 50 to 90 ° C. Cathode current density vary with the composition of the plating solution, it is not particularly limited, low current density range (e.g. 1 mA / cm ² or more 10 mA / cm less than ²⁾ and a high current density range (e.g. 10 mA / cm ² than The fine crystal-amorphous mixed gold alloy plating film can be obtained at both of 200 mA / cm ² or less. Further, an insoluble anode such as platinum can be used as the anode. Nickel and / or cobalt may be used as the anode. On the other hand, examples of the object to be plated include metal materials such as copper and nickel used for electric wiring and the like. This metal material may be formed as a base layer on a metal substrate or a non-metal substrate. In addition, although the presence or absence of stirring is not ask | required, it is preferable to plate with stirring and you may apply an electric current with a pulse current.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example. In the examples, methods and conditions for each analysis and measurement are as follows.

Crystalline, by the grain size manufactured by Rigaku Corporation RINT2100-Ultima +: XRD method CuKα (40kV / 40mA)
Or, by HF-2200 manufactured by Hitachi High-Technologies Corporation: TEM and THEED method Acceleration voltage 200V Bright field image
Volume fraction : HF-2200 manufactured by Hitachi High-Technologies Corporation: TEM method and THEED method Acceleration voltage 200V Bright field image
According to SEA5100, metal composition SII Nanotechnology, Inc .: EDXRF method
Nonmetallic element measurement EMIA-920V manufactured by Horiba, Ltd., TC-436 manufactured by LECO, USA
Knoop hardness Measured according to JIS Z 2251: Load 5 gf Load holding time 30 seconds Measured with a 30 μm-thick plating film formed on a copper plate
Specific resistance Kyowa Riken Co., Ltd. K-705RS: Measured according to JIS K 7194 (four-probe method)

[Example 1]
Contains KAu (CN) ₂ 0.035 mol / dm ³ , NiSO ₄ · 6H ₂ O 0.076 mol / dm ³ , triammonium citrate 0.21 mol / dm ³ and adjusts the pH to 6 with KOH and sulfuric acid Using the electroplating solution, a fine crystal-amorphous mixed gold alloy plating film (film thickness: 1 μm) was formed on a copper plate having a temperature of 70 ° C. and a current density of 10 mA / cm ² and a purity of 99.96%. A platinum-coated titanium electrode (network) was used as the anode, and the plating bath during plating was vigorously stirred.

  The obtained fine crystal-amorphous mixed gold alloy plating film was analyzed by XRD, TEM and THEED. An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. A broad peak having a peak half-value width of 1 degree or more peculiar to fine crystals or amorphous can be confirmed in the vicinity of 2θ = 40 degrees of the XRD pattern. Further, in the TEM image, it is possible to observe a mixture of crystal stripes peculiar to crystals and irregular structures peculiar to amorphous. In the THEED pattern, it can be observed that a diffraction spot peculiar to crystal and a halo ring peculiar to amorphous are mixed. This result shows that the obtained plating film has a fine crystal-amorphous mixed structure. As a result of observing the TEM image, the average grain size of the fine crystals was 10 nm, and the volume fraction of the fine crystal phase was 50%. On the other hand, composition analysis, Knoop hardness and specific resistance of the obtained fine crystal-amorphous mixed gold alloy plating film were measured. Gold was detected at a content of 41.2 atomic% as a metallic element, 46.0 atomic% of nickel, and 12.8 atomic% as a nonmetallic element. The Knoop hardness was Hk347, and the specific resistance was 89 μΩ · cm.

[Example 2]
Except for adding 20 vol% of n-propanol, plating was performed in the same manner as in Example 1, and XRD, TEM, and THEED analysis were performed on the obtained plating film. An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. A broad peak having a peak half-value width of 1 degree or more peculiar to fine crystals or amorphous can be confirmed in the vicinity of 2θ = 40 degrees of the XRD pattern. Further, in the TEM image, it is possible to observe a mixture of crystal stripes peculiar to crystals and irregular structures peculiar to amorphous. In the THEED pattern, it can be observed that a diffraction spot peculiar to crystal and a halo ring peculiar to amorphous are mixed. This result shows that the obtained plating film has a fine crystal-amorphous mixed structure. As a result of observing the TEM image, the average grain size of the fine crystals was 10 nm, and the volume fraction of the fine crystal phase was 50%. On the other hand, composition analysis, Knoop hardness and specific resistance of the obtained fine crystal-amorphous mixed gold alloy plating film were measured. Gold was detected at a content of 48.1 atomic% as a metallic element, 38.1 atomic% of nickel, and 13.8 atomic% of carbon as a nonmetallic element. The Knoop hardness was Hk348, and the specific resistance was 89 μΩ · cm.

[Example 3]
The citric acid concentration is 0.143 mol / dm ³ , the ammonia concentration is 1.2 mol / dm ^3, and current density is 1 mA / cm ² (energization time 50 seconds) and 10 mA / cm ² (energization time 5 seconds). Plating was performed in the same manner as in Example 1 except that electrolytic plating was alternately performed, and XRD, TEM, and THEED analysis were performed on the obtained plating film. An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. A broad peak having a peak half-value width of 1 degree or more peculiar to fine crystals or amorphous can be confirmed in the vicinity of 2θ = 40 degrees of the XRD pattern. Further, in the TEM image, it is possible to observe a mixture of crystal stripes peculiar to crystals and irregular structures peculiar to amorphous. In the THEED pattern, it can be observed that a diffraction spot peculiar to crystal and a halo ring peculiar to amorphous are mixed. In the case of constant current plating, only a crystalline phase was obtained at a current density of 1 mA / cm ² and only an amorphous phase was obtained at 10 mA / cm ² . From this result, it can be seen that the plating film obtained by pulse plating has a fine crystal-amorphous mixed structure. Further, as a result of observing the TEM image, the average particle diameter of the fine crystals was 10 nm, and the volume fraction of the fine crystal phase was 60%. On the other hand, composition analysis, Knoop hardness and specific resistance of the obtained plating film were measured. Gold was detected at a content of 47.4 atomic% as a metallic element, 47.0 atomic% of nickel, and 5.6 atomic% as a nonmetallic element. The Knoop hardness was Hk222, and the specific resistance was 57 μΩ · cm.

[Example 4]
Amorphous gold alloy plating obtained by plating in the same manner as in Example 1 except that the citric acid concentration was 0.143 mol / dm ³ , the ammonia concentration was 1.2 mol / dm ³ , and the current density was 50 mA / cm ^2. XRD, TEM, and THEED analyzes were performed on the plating film obtained by annealing the film at an annealing temperature (heat retention temperature) of 400 ° C., a temperature increase rate of 10 ° C./min, and a heat retention of 1 hour in an air atmosphere. An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. A broad peak having a peak half-value width of 1 degree or more peculiar to fine crystals or amorphous can be confirmed in the vicinity of 2θ = 40 degrees of the XRD pattern. Further, in the TEM image, it is possible to observe a mixture of crystal stripes peculiar to crystals and irregular structures peculiar to amorphous. In the THEED pattern, it can be observed that a diffraction spot peculiar to crystal and a halo ring peculiar to amorphous are mixed. This result shows that the obtained plating film has a fine crystal-amorphous mixed structure. As a result of observing the TEM image, the average grain size of the fine crystals was 15 nm, and the volume fraction of the fine crystal phase was 60%.

[Example 5]
KAu (CN) ₂ is contained in 0.035 mol / dm ³ , CoSO ₄ .7H ₂ O is contained in 0.076 mol / dm ³ , citric acid / H ₂ O is contained in 0.1 mol / dm ^3, and the ammonia concentration is 0.44 mol / dm ^3. and dm ^3, with KOH and electroplating solution and the pH was adjusted to 6 with sulfuric acid, the temperature 70 ° C., a current density of 10 mA / cm ² with a purity 99.96% of the copper plate on the microcrystalline - amorphous mixed gold alloy plated film ( A film thickness of 1 μm) was formed. A platinum-coated titanium electrode (network) was used as the anode, and the plating bath during plating was vigorously stirred.

  The obtained fine crystal-amorphous mixed gold alloy plating film was analyzed by XRD, TEM and THEED. An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. A broad peak having a peak half-value width of 1 degree or more peculiar to fine crystals or amorphous can be confirmed in the vicinity of 2θ = 40 degrees of the XRD pattern. Further, in the TEM image, it is possible to observe a mixture of crystal stripes peculiar to crystals and irregular structures peculiar to amorphous. In the THEED pattern, it can be observed that a diffraction spot peculiar to crystal and a halo ring peculiar to amorphous are mixed. This result shows that the obtained plating film has a fine crystal-amorphous mixed structure. As a result of observing the TEM image, the average grain size of the fine crystals was 5 nm, and the volume fraction of the fine crystal phase was 15%. On the other hand, composition analysis and Knoop hardness of the obtained fine crystal-amorphous mixed gold alloy plating film were measured. Gold was detected at a content of 36.4 atomic% as a metallic element, 40.6 atomic% of cobalt, and 23.0 atomic% of carbon as a nonmetallic element. Knoop hardness was Hk180.

[Comparative Example 1]
0.143 mol / dm ³ acid concentrations citric, except that the ammonia concentration and 0.46 mol / dm ³ performs the plating in the same manner as in Example 1, the obtained plated film XRD, was TEM and THEED Analysis . An XRD pattern is shown in FIG. 1, and a TEM image and a THEED pattern are shown in FIGS. In the vicinity of 2θ = 40 degrees of the XRD pattern, a broad peak having a peak half-value width of 1 degree or more peculiar to amorphous can be confirmed. Moreover, the irregular structure peculiar to amorphous | non-crystalline substance was confirmed in the TEM image, and the regular structure like a crystal grain boundary or a crystal stripe was not able to be confirmed. Then, halo ring peculiar to amorphous can be confirmed in the THEED pattern. From this result, it can be seen that the obtained plating film has a homogeneous amorphous structure having no fine crystals. Further, composition analysis, Knoop hardness and specific resistance of the obtained plating film were measured. Gold was detected at a content of 15.2 atomic% as a metal element, 67.5 atomic% as a nickel element, and 17.3 atomic% as a nonmetallic element. The Knoop hardness was Hk435, and the specific resistance was 251 μΩ · cm.

[Comparative Example 2]
KAu (CN) ₂ contains 0.04 mol / dm ³ , NiSO ₄ .6H ₂ O contains 0.0085 mol / dm ³ , citric acid / H ₂ O contains 0.5 mol / dm ³ , and KOH contains 0.7 mol / dm ³ Then, using an electroplating solution whose pH was adjusted to 3.5 with sulfuric acid, a hard gold plating film (film thickness 1 μm) was formed on a copper plate with a temperature of 30 ° C. and a current density of 10 mA / cm ² and a purity of 99.96% . A platinum-coated titanium electrode (network) was used for the anode, and the plating bath during plating was gently stirred.

  The obtained hard gold plating film was analyzed by XRD, TEM and THEED. The XRD pattern is shown in FIG. A sharp peak derived from Au (111) can be confirmed in the vicinity of 2θ = 38 degrees of the XRD pattern. Moreover, it was confirmed from the TEM image and the THEED pattern that it was a crystal. From this result, it can be seen that the obtained plating film has a polycrystalline structure having no amorphous phase. Moreover, as a result of calculating from an XRD pattern, the average particle diameter of the crystal was 13 nm. On the other hand, composition analysis, Knoop hardness and specific resistance of the obtained plating film were measured. Gold was detected as a metal element at a content of 96.5 atomic%, nickel as a 0.77 atomic%, and carbon as a nonmetallic element at a content of 2.7 atomic%. The Knoop hardness was Hk160, and the specific resistance was 17 μΩ · cm.

  In the XRD pattern shown in FIG. 1, the sharp peak observed near 2θ = 50 ° is due to the copper of the substrate.

  In addition, the Knoop hardness of the fine crystal-amorphous mixed gold alloy plating film of Example 1 is that of additive-free hard gold (AFHG), nickel hard gold (NiHG), and CoHG, which are considered to have high hardness in the gold plating film. It can be seen that the Knoop hardness does not reach Hk200, but has a high hardness corresponding to two to three times.

Claims (13)

  A plating film of gold alloy, wherein the plating film is formed by mixing a crystalline phase and an amorphous phase.   The plating film according to claim 1, wherein the volume fraction of the crystal phase is 10 to 90%.   The plating film according to claim 1, wherein an average particle diameter of the crystal phase is 30 nm or less.   The plating film according to claim 1, wherein a peak half-value width in the vicinity of 2θ = 40 degrees in the X-ray diffraction pattern is 1 degree or more.   The plating film in any one of Claims 1-4 whose Knoop hardness is Hk180 or more.   The plating film in any one of Claims 1-5 whose specific resistance is 200 microhm * cm or less. Composition formula: Au _100-xy M _x C _y (where Au or M is the main component, M is Ni and / or Co, C is carbon, 1 atomic% ≦ x ≦ 80 atoms %, 1 atomic% ≦ y ≦ 30 atomic%).   The plating film according to claim 1, which is used as an electrical contact material.   An electroplating solution for forming a plating film according to any one of claims 1 to 8, comprising a gold cyanide salt, a nickel salt and / or a cobalt salt, a complexing agent and a pH adjusting agent. Plating solution.   The complexing agent is one or more selected from the group consisting of citric acid, tartaric acid, malic acid, pyrophosphoric acid, phosphoric acid, sulfamic acid and their sodium, potassium and ammonium salts, and pH adjustment The electroplating solution according to claim 9, wherein the agent is ammonia water or potassium hydroxide.   The electroplating solution according to claim 10, wherein the complexing agent is citric acid and the pH adjusting agent is aqueous ammonia.   A method for forming a gold alloy plating film, wherein a gold alloy plating film in which a crystalline phase and an amorphous phase are mixed is formed on an object to be plated using the electroplating solution according to any one of claims 9 to 11. The forming method.   The electrical / electronic component using the plating film in any one of Claims 1-8.