JP6399494B2 - Method for producing metal film-formed product - Google Patents

Description

  The present invention relates to a method of manufacturing a metal film-formed product, and more particularly to a method of manufacturing a metal film-formed product having a step of forming a laser sintered film including an alloy layer in which metal fine particles are dissolved by laser light irradiation.

  Conventionally, gold-cobalt (Au-Co) alloy electroplating films and electroless plating (chemical plating) films are well known as gold (Au) plating films for connectors of electronic devices. This is because by adding about 0.3-0.5 mass% of metallic Co atoms in the Au plating film, the hardness of the Au plating film can be improved, and the wear resistance in repeated insertion / extraction of the connector can be improved. Is the purpose. However, in this conventional electroplating or electroless plating method, from the problem that the formation of a local plating film on the contact portion of the connector material made of a copper (Cu) alloy such as phosphor bronze becomes very expensive, A method in which Au alloy nanoparticle ink (a dispersion of Au alloy nanoparticles) is partially applied to the contact portion of the connector material and heated and sintered has been studied. At present, for this purpose, Au alloy-based nanoparticles alloyed with Co or nickel (Ni) are being developed.

  Patent Document 1 discloses a novel gold-nickel alloy nanoparticle (particle diameter of 500 nm or less) in which Au and Ni are substantially mixed as a contact material and a manufacturing method thereof. The gold-nickel alloy nanoparticles of Patent Document 1 are mainly composed of a substitutional solid solution of gold and nickel, and the concentration of nickel contained in the gold-nickel alloy is 2.0 wt% to 92.7 wt%. In this method for producing gold-nickel alloy nanoparticles, gold ions, nickel ions and a reducing substance are mixed and gold-nickel alloy nanoparticles are deposited by a chemical reduction reaction.

  Patent Document 2 discloses a method for producing Au alloy nanoparticles by a reduction method as in Patent Document 1. The method described in Patent Document 2 is characterized in that a plasma reduction method is used. Prepare a solution containing metal ions of a metal element for alloying other than Au, place a pair of electrodes made of Au at least one in the solution, and apply a voltage between the electrodes to generate plasma in the solution. An alloy nanoparticle composed of Au released from an electrode by plasma and metal reduced from metal ions by plasma is formed.

  In addition, inks of mixed metal nanoparticles that are not alloyed but mixed with metal particles have been announced. Patent Document 3 discloses a metal particle dispersion containing metal particles, a dispersant and a solvent, a step of coating the metal particle dispersion on a substrate to form a coating film, and a baking treatment of the coating film. A method of manufacturing a sintered film is disclosed. The metal particles of the metal particle dispersion include at least one selected from the group consisting of Au, Ag, Cu, Ni, Pt, Pd, Mo, Al, Sb, Sn, Cr, La, In, Ga, and Ge. Further, it is disclosed that the dispersing agent is a metal particle dispersion of a graft copolymer in which a salt is formed with at least one selected from the group consisting of an acidic phosphorus compound and a sulfonic acid compound. . It is important for the mixed metal nanoparticles that each metal nanoparticle can be stably dispersed. For this reason, Patent Document 3 states that a method for producing mixed metal nanoparticle ink excellent in dispersibility and dispersion stability is established by using a combination of specific metal particles and a specific dispersant. As a method for obtaining a sintered film, a method of raising the temperature to a temperature at which metal particles are fired, a method using surface wave plasma generated by application of microwave energy, and the like are disclosed.

  On the other hand, the furnace firing method in which mixed metal nanoparticles are heated and sintered is very difficult to completely melt and alloy because the melting points of mixed metal nanoparticles are different. As shown in the binary system equilibrium diagram showing the temperature and phase state of the metal alloy system, the alloying of the metal maintained an equilibrium state of uniform mixing of the added metal components at a temperature above its melting point. Thereafter, it is melted and solidified to form an alloy as a solid. As described later, as a sintering method for obtaining an alloy, there is a laser sintering method for obtaining a metal nanoparticle sintered film on a substrate surface by irradiating a laser beam.

  Patent Document 4 discloses a metal film forming method in which noble metal plating is performed on the surface of a base metal, and the passive film formed on the base metal is decomposed by irradiating the surface of the base metal with a laser beam. A surface activation step for removing, and a noble metal nanoparticle dispersion applying step for applying a noble metal nanoparticle dispersion in which noble metal nanoparticles are dispersed in a solvent on the surface of the base metal where the passive film has been decomposed and removed. And a noble metal nanoparticle sintering method in which the noble metal nanoparticle dispersion applied to the surface of the base metal is irradiated with a laser beam to sinter the precious metal nanoparticles. ing. The noble metal nanoparticle dispersion of Patent Document 4 is, for example, a single nanoparticle dispersion of Au or silver (Ag). The features of the laser sintering method are that a sintered film having a short sintering time and excellent adhesion to a metal substrate can be obtained, and that a sintered film having few defects such as voids can be obtained.

  In addition to the laser sintering method, a method of sintering mixed metal nanoparticles by microwave plasma has been proposed. In Patent Document 5, an organic substance or a solvent as a dispersant is mixed into a mixed metal particle of metal particles (silver, silver, or aluminum) and metal nanoparticles (nanoparticles such as copper, silver, or gold) to form metal fine particles. , By preparing a dispersion liquid (material for forming a conductive metal film) containing nanoparticles, applying this dispersion liquid on a substrate, and then firing by irradiating microwave plasma in a reducing atmosphere, A thick metal film is obtained. In this method, utilizing the characteristics of the low melting point of metal nanoparticles, other metal fine particles are joined to form a thick film.

International Publication No. 2013/137469 JP 2014-101530 A JP 2014-88550 A Patent No. 5760060 JP 2013-247060 A

  In the case of metal film-formed products, especially connectors for electronic equipment, the metal film formed on the base material has excellent electrical properties (high electrical conductivity), as well as excellent adhesion to the base material and wear resistance. It is required to have

  In Patent Documents 1 and 2 described above, a method for producing alloy nanoparticles is disclosed, but a method for forming a metal film on a substrate has not been studied. Even in Patent Document 3, although a method for obtaining a metal film is exemplified, a specific method has not been studied, and the electrical characteristics, adhesion, and wear resistance of the metal film have not been evaluated.

  Patent Document 4 discloses a laser sintering method as a method for forming a metal film, but a method for alloying metal fine particles has not been studied. Further, Patent Document 5 discloses a method for obtaining a bulk conductive metal thick film, but this is also not studied for alloying metal fine particles.

  Therefore, in any of the above patent documents, an alloy film having characteristics (electrical characteristics, adhesion and wear resistance) equal to or better than those of the conventional methods is used without using conventional electroplating or electroless plating. It can be said that a method for producing a metal film-formed product by locally forming on a substrate has not been established.

  In view of the above circumstances, the present invention provides a base material with an alloy film having electrical characteristics, adhesion and wear resistance equal to or higher than those of the conventional methods without using conventional electroplating or electroless plating. An object of the present invention is to provide a method for producing a metal film-formed product that can be formed in a standard manner.

In order to achieve the above object, the present invention provides a coating process in which a dispersion in which two or more kinds of metal fine particles are dispersed in a solvent is applied to the surface of a substrate to form a coating film, and laser light is applied to the coating film. And a laser beam irradiation step of forming a laser sintered film containing an alloy in which the metal fine particles are dissolved in the surface of the base material . The metal fine particles are composed of metal fine particles composed of metal elements constituting the main phase and metal fine particles composed of metal elements that can be dissolved in the main phase. The average particle size of metal fine particles composed of metal elements constituting the main phase is 1 to 10 nm or less, and the average particle size of metal fine particles composed of metal elements that can be dissolved in the main phase is 10 to 100 nm. Furthermore, the metal film characterized in that the content of metal fine particles comprising a metal element that can be dissolved in the main phase is 0.1 to 0.5 parts by mass with respect to the metal element constituting the main phase of the dispersion liquid. A method of manufacturing a molded article is provided.

  According to the present invention, without using conventional electroplating or electroless plating, an alloy film having electrical characteristics, adhesion and wear resistance equal to or better than those of these conventional methods is locally applied to the substrate surface. The manufacturing method of the metal film formation goods which can be formed can be provided.

  Problems, configurations, and effects other than those described above will become apparent from the following description of embodiments.

Sectional drawing which shows typically an example of the manufacturing method of the metal film formation goods which concern on this invention FIG. 2 is an enlarged view schematically showing the vicinity of a laser sintered film 4 in FIG. 1. FIG. 3 is an enlarged view schematically showing second metal fine particles in FIG. 2. The figure which shows the test piece (male terminal) of a present Example The figure which shows the test piece (female terminal) of a present Example Graph showing reflection absorption transmission spectrum of Au nanoparticle coating film Graph showing reflection spectrum of Ni fine particle coating film SEM observation photograph of laser sintered film of test piece of this example Schematic diagram showing the abrasion resistance evaluation test apparatus of this example Schematic diagram showing the abrasion resistance evaluation test method of this example The graph which shows a time-dependent change of the contact resistance of the Au nanoparticle laser sintering film | membrane in the abrasion-resistance evaluation test of a present Example The graph which shows a time-dependent change of the contact resistance of the 0.5 mass part Ni-Au alloy laser sintering film | membrane in the abrasion resistance test of a present Example. The graph which shows the time-dependent change of the contact resistance of 2 mass parts Ni-Au alloy laser sintering film | membrane in the abrasion resistance test of a present Example. The graph which shows the time-dependent change of the contact resistance of 5 mass parts Ni-Au alloy laser sintered film in the abrasion resistance test of a present Example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view schematically showing an example of a method for producing a metal film-formed product according to the present invention. As shown in FIG. 1, the method for producing a metal film-forming product according to the present invention uses a dispersion (ink) in which at least two or more (plural types) of metal fine particles are dispersed in a solvent (solvent). A coating step (a) for coating the surface to form the coating film 2; and an alloy layer in which the metal fine particles contained in the dispersion are solid-dissolved on the surface of the substrate 1 by irradiating the coating film 2 with the laser beam 3 And a laser beam irradiation step (b) for forming a laser sintered film (also referred to as “hybrid metal fine particle sintered film” or “metal fine particle composite”) 4. That is, according to the present invention, the second liquid that can be dissolved in the first metal fine particles (main phase) by the energy of laser light in the dispersion liquid containing the first metal fine particles (metal fine particles constituting the main phase). The metal fine particles (metal fine particles that can be dissolved in the main phase) are prepared to prepare a dispersion containing two or more kinds of metal fine particles (also referred to as “metal fine particle mixed dispersion” or “hybrid metal fine particle dispersion”). Then, the dispersion liquid is applied onto the base material 1 to obtain a coating film 2, and the coating film 2 is irradiated with the laser beam 3 to obtain a laser sintered film 4 of the metal fine particle mixed dispersion liquid on the base material 1. Is. Hereinafter, each process will be described in detail.

(A) Application Step (a-1) Preparation of Metal Fine Particle Mixture Dispersion First, a dispersion is prepared in which at least two types (plural types) of metal fine particles are dispersed in a solvent. As the plurality of metal fine particles, a first metal fine particle made of a metal element constituting the main phase and a second metal fine particle made of a metal element that can be dissolved in the main phase are selected. The first metal fine particles and the second metal fine particles are selected from elements that form a solid solution by the energy of laser light in a laser light irradiation process described later.

  Moreover, it is preferable that a 1st metal microparticle consists of an atom which carries out an atomic diffusion in a base material by the laser beam irradiation in the laser beam irradiation process mentioned later. By selecting such a material as the first metal fine particles, high adhesion between the substrate 1 and the laser sintered film 4 can be obtained.

  Specifically, the first metal fine particles are preferably Au or Ag that is practically used for connector terminals. As the second metal fine particles, when the first metal fine particles are Au, germanium (Ge), silicon (Si), zirconium (Zr) or the like which is a metal that can be dissolved in Au can be used. Further, when the first metal fine particles are Ag, examples of the second metal fine particles include Si, titanium (Ti), and Zr that can be dissolved in Ag. In addition, the second metal fine particles may be any metal that can be dissolved in the main phase of the first metal fine particles and can obtain performance as a connector metal terminal.

  In the present invention, since an electrolytic solution such as electroplating or chemical plating is unnecessary, any metal combination capable of forming a substitutional or interstitial solid solution as a metal may be used. Then, it is possible to select an alloy system that is impossible. In so-called electroplating or chemical plating, a combination of metals that can be alloyed because the metal is stably present in the electrolyte and is subject to restrictions such as cathodic reducibility, anodic solubility, or chemical reducibility. There are limitations. In electroplating and chemical plating, multiple layers of base plating may be required to ensure close contact with the substrate metal, but the present invention focuses laser energy light on the substrate interface. Since the main phase metal diffuses into the metal substrate, it is not necessary to provide an underlayer. The present invention is also characterized in that a metal fine particle dispersion film in which the second metal fine particles are atomically diffused with respect to the main phase can be formed. In electroplating, in order to disperse and deposit metal fine particles in a plating film, a method is adopted in which metal fine particles are mixed in a plating solution, and the metal fine particles are captured and contained in the electroplated crystal structure. In this method, since the interface between the electroplating film and the metal fine particles does not diffuse, there is a problem that the dispersed metal particles are peeled off and dropped when applied to the plating film of the connector terminal. In order to prevent this peeling off, an additional process such as diffusion heat treatment after plating is required.

In addition, the present invention has a feature that a sintered film can be formed in a short time because the following processes proceed almost simultaneously in laser sintering.
1) Melting of first metal fine particles as a main phase 2) Diffusion solid solution reaction of second metal fine particles into first metal fine particle molten layer 3) Atom diffusion of molten first metal fine particles into metal substrate 4) Acceleration of atomic diffusion due to temperature rise of metal substrate by transmitted laser beam 5) Film formation by solidification of main phase In the present invention, the above 1) to 5) are completed in a short time of 0.1 to 1 s.

  An outline of a laser sintered film formed through the above process is shown in the figure. FIG. 2 is an enlarged view schematically showing the vicinity of the laser sintered film 4 in FIG. 1, and FIG. 3 is an enlarged view schematically showing the second metal fine particles in FIG. As shown in FIGS. 2 and 3, the laser sintered film 4 includes a main phase (a molten layer of first metal fine particles) 41 and second metal fine particles 42. The interface between the second metal fine particles 42 and the main phase 41 has a diffusion layer 43 to the main phase 41 of the second metal fine particles 42. At the interface between the laser sintered film 4 and the base material 1, there is a diffusion layer 40 in which the first metal fine particles constituting the main phase 41 are atomically diffused in the base material 1.

  In the present invention, each of the first metal fine particles and the second metal fine particles is not limited to one type, and two or more types of metal fine particles may be mixed. By mixing a plurality of kinds of metal fine particles, a multi-component alloy laser sintered film 4 can be formed on the substrate 1.

  As described above, the first metal fine particle and the second metal fine particle of the present invention can be selected in consideration of the characteristics required for the laser sintered film 4 and the possibility of solid solution of both, and the above example It is not limited to.

The average particle diameter of the first fine metal particles is in the range of 1 to 10 nm, the average particle diameter of the second fine metal particles and 10 to 100 nm (10 nm or more 100nm or less). The reason why the average particle diameter of the second metal fine particles is set to 10 to 100 nm is that when the metal terminal of the connector having the electrical contact portion is used as the base material 1, the thickness of the plating film formed on the electrical contact portion is usually 0. This is because the thickness is about 0.05 to 0.2 μm. When the average particle size of the second metal fine particles is larger than 100 nm, the particle size of the second metal fine particles becomes greater than the film thickness, and the average (uniform) dispersion of the second metal fine particles in the laser sintered film 4 is achieved. It is because is inhibited. Further, when the second metal fine particles are nanoparticles, most of the second metal fine particles become an alloy phase in which the second metal fine particles are dissolved in the first metal fine particles by laser light irradiation. When the average particle diameter of the second metal fine particles is 10 nm or more, the surface of the second metal fine particles is dissolved in the first metal fine particles, but the inside of the second metal fine particles that cannot be dissolved is the main phase (first phase). In a phase composed of fine metal particles). Since the second metal fine particles mixed in the form of particles without causing a solid solution reaction with the first metal fine particles are particles that are strongly metal-bonded in the main phase and do not fall off, wear resistance of the metal terminals of the connector The property can be further improved.

  In the present invention, the term “metal fine particles” is meant to include the sizes (on the order of nanometers) of the first metal fine particles and the second metal fine particles.

  The first metal fine particles and the second metal fine particles described above are dispersed in a solvent to obtain a dispersion. There is no limitation in particular as a solvent, It is preferable to use the solvent of the low boiling point (350 degrees C or less) which decomposes | disassembles completely with a laser in the laser beam irradiation process mentioned later. This is because if these components are not decomposed and are present in the wiring film, voids may be generated and electrical resistance may be increased. Specifically, alcoholic, paraffinic, and naphthenic organic solvents can be used.

  As a method for mixing the first metal fine particles, the second metal fine particles, and the solvent, the second metal fine particles are mixed in a dispersion liquid (first metal fine particle ink) in which the first metal fine particles are dispersed in advance. A metal fine particle mixed dispersion can be prepared. As a method for mixing the second metal fine particles, there is a method in which the second metal fine particle powder is directly charged into the first particle dispersion and then uniformly mixed with an ultrasonic stirrer or a planetary mill. Since metal fine particles of 10 nm or more have a small tendency to decrease in melting point due to the particle effect that is characteristic of nanoparticles, it is not necessary to coat the surface of the metal fine particles with a dispersant having a strong electronegativity binding group, and the powder is mixed as it is. And can be mixed with stirring. Of course, the second metal fine particles may be treated with a dispersant, mixed with a solvent, and mixed with the first metal fine particle dispersion. Dispersibility in the dispersion can be enhanced by the treatment with the dispersant.

Moreover, content in the dispersion liquid of 2nd metal microparticles shall be 0.1-0.5 mass part with respect to 1st metal microparticles. If the amount is less than 0.1 parts by mass, the effect of adding the second metal fine particles cannot be obtained. On the other hand, if the amount exceeds 0.5 parts by mass, the dispersion of the second metal fine particles on the surface of the sintered film becomes non-uniform, and the electrical characteristics deteriorate.

  Further, the dispersion may contain additives such as a binder and a viscosity modifier as necessary. It is preferable to use a low boiling point (350 ° C. or lower) solvent or a low molecular weight (10,000 or lower) organic compound that can be completely decomposed by a laser.

(A-2) Preparation of base material The shape and material of the base material 1 are not particularly limited, but when a metal terminal is applied as a metal film-formed product, a copper-based alloy can be mentioned. Examples of the copper-based alloy include phosphor bronze, brass, Corson copper alloy, and magnesium copper alloy. For the metal terminal used for the connector, other than phosphor bronze or brass, a copper alloy with improved spring characteristics is also used. Usually, a terminal is made by pressing the copper alloy using a metal press die. Since the non-volatile press oil may adhere to the pressed terminal, the remaining press oil is cleaned and removed using a hydrocarbon cleaner or the like. This metal terminal includes a male terminal and a female terminal, each having a different shape, and is manufactured using each press die. The laser sintered film 4 is formed by a laser beam irradiation process described later on the electrical contact portions of the male terminal and the female terminal.

(A-3) Application of metal fine particle mixed dispersion The above-described metal fine particle mixed dispersion is applied to the substrate 1 (such as an electrical contact portion of a metal terminal) to form a coating film 2. As a coating method, a conventional ink coating method (so-called on-demand fine area printing method) such as an inkjet method or a dispenser method can be used as it is. In order to suppress the spread of the dispersion from the application area, the substrate 1 may be treated with a water repellent. As the water repellent, in addition to a silicone release agent, a fluorine release agent can also be used.

  The amount of dispersion applied is determined according to the thickness of the sintered film required after laser sintering. After the formation of the coating film 2, it is preferable to perform a drying process for removing the solvent to some extent. The drying temperature is preferably a temperature not higher than the boiling point of the solvent and a temperature lower than the boiling point of the metal fine particle mixed dispersion (a temperature at which the sintering of the first metal fine particles and the second metal fine particles does not start). When the drying temperature is higher than the boiling point of the metal fine particle mixed dispersion (for example, 300 ° C. or higher), the metal fine particles in the dispersion are sintered before laser light irradiation, resulting in voids in the sintered film and the denseness. As a result, the adhesiveness between the base material and the laser sintered film is lowered.

(B) Laser light irradiation step The laser sintered film 4 having a melt-solidified structure is obtained by irradiating the coating film 2 with the laser light 3 (laser plating). The laser light 3 in the laser light irradiation process has sufficient energy for the second metal fine particles to melt and dissolve in the first metal fine particles, and the first metal fine particles can sufficiently diffuse into the substrate. The one with the right energy. Examples of practical laser light sources include a neodymium YAG (Nd: YAG) laser with a wavelength of 1064 nm, a second harmonic of a YAG laser with a wavelength of 532 nm, or a laser diode (Laser Diode; LD) laser with a wavelength of 915 nm. It is preferable to select in consideration of the light reflection, absorption and transmission spectrum data of each metal micron contained in the mixed dispersion and the light reflection and absorption spectrum data of the base material 1. Further, as the laser output mode, either standing wave or pulse wave can be used. However, since the physical properties of the sintered film 4 are different in the laser output mode, depending on the type of the metal fine particle mixed dispersion and the type of the substrate 1. It is preferable to select. In the present invention, since it is important that the second metal fine particles are dissolved in the first metal fine particles serving as the base of the sintered film, the second metal fine particles are atomically diffused into the melted first metal fine particles. It is important to select the type of laser that can be dissolved, the output mode, the laser power, and the irradiation time. The first metal fine particles and the second metal fine particles may have a completely solid solution structure or may not have a completely solid solution structure.

  For example, in the present invention, Ni, Co, Cr and the like constituting the second metal fine particles have a higher absorption rate for light having a wavelength of 900 nm than that of Au and Ag constituting the first metal fine particles, and the temperature rises. Although there is an easy feature, Au nanoparticles having an average particle diameter of 10 nm have a small particle diameter, a melting point as low as several hundred degrees C due to the particle effect, and a plasmon absorption effect. From this feature, the laser power is set on the substrate 1 in a short time of 10 to 100 ms by setting the laser power to a temperature sufficient to allow the second metal fine particles to diffuse into the first metal fine particles. The conjunctiva 4 can be formed. In addition, an optimum laser fluence is selected so that the first metal fine particles and the second metal fine particles melted within this time advance atomic diffusion with the underlying base material 1. Thus, by selecting the laser light irradiation conditions, the laser sintered film 4 having excellent adhesion to the substrate 1 can be obtained.

According to the method for producing a metal film-formed product according to the present invention described above, the following effects can be obtained.
(I) A laser sintered film having excellent wear resistance can be formed on the electrical contact portion of the connector metal terminal without using electroplating or electroless plating. Conventionally, the electrical contact portion of the metal terminal has been plated by a special partial plating method. The dimension of the plating range required for the electrical contact portion is as small as about 0.1 to 1.0 mm, but partial plating with a diameter of 0.5 mm or less is almost impossible by electroplating or electroless plating. According to the present invention, it is possible to perform fine and local plating with a size (φ0.5 mm or less) which is impossible with the conventional plating method.
(Ii) The laser sintered film of the metal fine particle mixed dispersion obtained by the present invention forms a metal alloy laser sintered film having excellent adhesion to a base material (metal substrate, etc.) compared with a sintered film obtained by furnace firing. be able to.
(Iii) Compared with electroplating and electroless plating methods, a laser sintered film in which various metal fine particles are mixed in an alloy film with Au or Ag can be obtained, and the characteristics such as wear resistance are further improved. An excellent laser sintered film can be obtained.
(Iv) A sintered film can be obtained in a shorter time (in the order of ms) as compared with furnace firing (a firing time of about 1 h is required at several hundred ° C.). For this reason, it is possible to inline the press process using a metal terminal press die.
(V) The process can be shortened as compared with electroplating, electroless plating, and furnace firing, thereby reducing the manufacturing cost and the amount of carbon dioxide emitted to the external environment.
(Vi) Compared with partial plating by electroplating and electroless plating, the application range of the dispersion liquid can be reduced, so that the amount of noble metals such as Au and Ag can be reduced, and the manufacturing cost is greatly reduced. It becomes possible. In addition, in wet partial plating in electroplating and electroless plating, complicated processes such as a plating masking process and a process of removing masking after plating are necessary, which is an obstacle to cost reduction. The present invention can solve this problem.
(Vii) Since the oxidation of the alloy surface of the substrate 1 can be prevented as compared with the furnace firing, the manufacturing cost can be reduced also in this respect. In the furnace firing, a metal oxide film is formed on the alloy surface of the substrate 1 for firing in the atmosphere or in an inert gas containing oxygen. When this metal oxide film grows thick, peeling occurs. Since this metal oxide film often peels off and drops off from the alloy of the base material 1, it adheres to the terminal surface of a finished product such as a connector and causes problems such as deterioration of wear resistance. For this reason, the furnace firing requires a step of removing this oxide film. For removal of the oxide film, an acidic aqueous solution such as sulfuric acid or a sulfuric acid aqueous solution containing an oxidizing persulfate is used. Since this process is a wet process, drainage treatment and drainage treatment of cleaning water are required, resulting in a significant increase in cost.
(Viii) Waste liquid treatment and waste water treatment in electroplating, electroless plating, etc. are unnecessary, and an environmentally friendly process can be provided.

  Hereinafter, the present invention will be described in more detail based on examples. In the following examples, a description will be given of an example of preparing a Ni-Au alloy laser sintered film by preparing a metal fine particle mixed dispersion obtained by mixing Ni fine particles in an Au nanoparticle dispersion and applying it to the electrical contact portion of a connector metal terminal. To do.

(A) Coating step (a-1) Preparation of metal fine particle mixed dispersion Ni fine particles with an average particle size of 20 nm were added to Au nanoparticle paste with an average particle size of 7 nm (Halima Kasei Co., Ltd. model name: NPG-J). Mixing was performed at respective ratios of 0, 0.5, 2 and 5 parts by mass with respect to the Au-containing mass of the Au nanoparticle paste, and four types of Ni fine particle-containing mixed metal fine particle dispersions were prepared. The Ni fine particles are metal fine particles manufactured by Iritech Co., manufactured by the atomization method, put into the Au nanoparticle paste in the form of fine particles, and an ultrasonic stirring device (manufactured by AS ONE Co., Ltd., model: USK-1R type, 40 KHz). , 55W) for 60 minutes. Au nanoparticle paste manufactured by Harima Kasei Co., Ltd. is prepared by dispersing Au nanoparticles treated with a dispersant in a solvent mainly composed of a naphthenic organic solvent. : 7.5 mPa · s, Au content: 57% by mass). After mixing Ni microparticles with Au nanoparticle paste, it was stored in a transparent glass container.

(A-2) Preparation of Substrate (Metal Terminal for Abrasion Resistance Test) FIG. 4 is a view showing a test piece (male terminal) of this example, and FIG. 5 is a test piece (female terminal) of this example. FIG. In this example, a male terminal and a female terminal test piece for an abrasion resistance test were prepared using a phosphor bronze material (JIS (Japan Industrial Standards) C5210) having a thickness of 0.25 mm used for the connector. The dimension of the test piece is 0.25 mm × 20 mm × 8 mm, and in order to prevent Cu from diffusing from the base material to the sintered film, electric Ni plating with a thickness of 1.0 μm is applied to both the male terminal and the female terminal on the surface of the test piece. I gave it to the whole surface.

  On the male terminal, an embossed shape (convex shape) of R1.0 mm was processed with a press die in a portion to be an electric contact portion before electric Ni plating. After electro Ni plating, as described later, a 0.3 μm thick Ni—Au laser sintered film and a 0.5 μm thick 0.3 mass% Co—Au alloy electroplated film were formed.

  On the other hand, a non-embossed female terminal was subjected to electroplating with a thickness of 1.0 μm on the entire surface, and then with 0.3 mass% Co—Au alloy electroplating with a thickness of 0.5 μm over the entire surface.

(A-3) Application of metal fine particle mixed dispersion The metal fine particle mixed dispersion prepared in (a-1) above was embossed with male terminals using a dispenser (manufactured by Nordson Corporation, product name: LV-100). It was applied to the top of the part. The coating area was 1.0 mm, and the coating amount was 2.2 nl so that the film thickness after laser sintering was 0.3 μm. After coating, the mixture was heated for 1.5 minutes at a temperature of 373 to 523 K in the atmosphere, and a part of the solvent in the dispersion was removed by drying.

  In addition, in order to evaluate the reflection / transmission / transmission spectral characteristics of the light of the coating film, a dispersion liquid containing only Au nanoparticles and a dispersion liquid containing only Ni fine particles are applied onto a quartz substrate, and dried. Thus, a sample having a coating film formed thereon was produced. Using a spectrophotometer (manufactured by Hitachi High-Technologies Corporation, model: U4100), the reflection absorption transmission spectrum of the coating film forming sample was measured. FIG. 6 is a graph showing the reflection absorption transmission spectrum of the Au nanoparticle coating film, and FIG. 7 is a graph showing the reflection absorption transmission spectrum of the Ni fine particle coating film. As shown in FIG. 6, Au nanoparticles have high transmittance (60 to 80% or more) in the wavelength band of 900 to 1100 nm, and the energy reaching the metal substrate is large. Further, the absorptance is 30% or less in this wavelength band. Therefore, when the laser light of 900 to 1100 nm is irradiated, the sintering of Au nanoparticles proceeds, but the amount of transmitted laser energy to the substrate is larger than that, so the temperature of the substrate rises rapidly, By heat transfer, bulking of Au nanoparticles and atomic diffusion of Au into the metal substrate proceed, and a sintered film with high adhesion can be obtained. On the other hand, as shown in FIG. 7, the Ni fine particles reflect about 10% in the entire wavelength band, do not transmit, and 90% or more are absorbed by the Ni fine particles. From this, Ni fine particles absorb more laser light than Au nanoparticles, the temperature of the particles rises more, the heat propagates to the Au nanoparticles dispersed around the Ni fine particles, and the ambient temperature rises rapidly. Therefore, it can be seen that the solid solution reaction preferentially proceeds around the Ni particles.

(B) Laser light irradiation step The coating film formed in the above (a-3) was irradiated with laser light to form a Ni—Au laser sintered film on the surface of the electrical contact portion of the metal terminal. Laser light irradiation was performed at a fixed point with an irradiation time of 0.1 s using an LD laser having a wavelength of 915 nm, a beam diameter of φ1.2 mm, and a maximum output of 100 W based on the measurement results of the spectral spectra shown in FIGS. 4 and 5, after laser irradiation, a sintered film having a thickness of 0.3 μm and Φ1.0 mm is formed on the male terminal, and a 0.3 mass% Co—Au having a thickness of 0.5 μm is formed on the female terminal. Alloy electroplating was applied to the entire surface.

  FIG. 8 is an SEM (Scanning Electron Microscope) observation photograph of the laser sintered film. In FIG. 8, (a) to (d) show test pieces having Ni contents of 0, 0.5, 2 and 5 parts by mass, respectively. As shown in FIG. 8, when the Ni fine particle content is 0.5 parts by mass (b), the Ni fine particles 61 are only slightly seen in the Ni-Au laser sintered film 60, and almost all of the added Ni fine particles are Au. It can be seen that it is dissolved in the nanoparticle sintered film. When the Ni fine particle content is 2 parts by mass (c) and 5 parts by mass (d), the Ni fine particles 61 are seen distributed on the surface of the Ni—Au laser sintered film 60. In other words, it can be seen that when the Ni fine particle content is 2 and 5 parts by mass, some of the mixed Ni fine particles are present in the Au nanoparticle sintered film without being completely dissolved. It can be seen that the Ni fine particles remaining without being dissolved are agglomerated to a maximum size of φ1 μm, and a smooth sintered film cannot be obtained when the Ni fine particle content is 2 parts by mass or more. From this, it is understood that the content of the Ni fine particles is preferably 0.5 parts by mass or less with respect to the mass of Au as the main phase.

  Next, the abrasion resistance of the produced test piece was evaluated. FIG. 9 is a schematic diagram showing an abrasion resistance evaluation test apparatus, and FIG. 10 is a schematic diagram showing an abrasion resistance evaluation test method. Using the test apparatus shown in FIG. 9, male and female terminals were arranged as shown in FIG. The evaluation conditions were a load of 20 gf, a sliding speed of 1 mm / s, and a sliding distance of 1 mm, and the test piece was slid about 3000 times in the X-axis direction. The contact resistance during sliding was measured by a four-terminal method (energization current 10 mA, release voltage 60 mV).

  FIG. 11 is a graph showing the change over time of the contact resistance of the laser sintered film containing only Au nanoparticles in the wear resistance test. In measurement of change in contact resistance of Au nanoparticle laser sintered film over time, a 0.3 μm thick Au nanoparticle laser sintered film is formed on the male terminal, and the female terminal is composed of 0.3 mass% Co—Au, film. Thickness: An electroplated film having a thickness of 0.5 μm was formed. For comparison, the evaluation result of a test piece on which an electric Au plating film (film thickness: 0.5 μm) is formed is also shown in FIG. The electrical Au plated terminal has a composition of 0.3 mass% Co—Au and a film thickness of 0.5 μm for both the male terminal and the female terminal. As shown in FIG. 11, the contact resistance of the laser-sintered film composed only of Au nanoparticles rapidly increases from around 1000 times the number of sliding compared with the electric Au plating film.

  Next, the abrasion resistance test results of the Ni—Au laser sintered film are shown in FIGS. 12 to 14 are graphs showing the change with time of the contact resistance of the Ni—Au laser sintered film in the wear resistance test. 12 to 14 are 0.5, 2 and 5 parts by mass with respect to the mass of Au as the main phase, respectively. As shown in FIGS. 12 to 14, when the content of Ni fine particles is 2 and 5 parts by mass, the increase in contact resistance from the start of the test is significant. On the other hand, when the Ni fine particle content is 0.5 parts by mass, the average is stable at about 20 mΩ (15 to 30 mΩ) during the sliding test. This is considered to be caused by the uniform distribution of Ni fine particles in the laser sintered film. Practically, it is required to be 100 mΩ or less in 3000 to 5000 sliding tests, but this level is sufficiently achieved with a test sample having a Ni fine particle content of 0.5 parts by mass. Recognize.

  In the case of a test piece with a Ni fine particle content of 2 parts by mass, the contact resistance sharply increased from around the 100th time, but in the case of a test piece with a Ni fine particle content of 5 parts by mass, a stage accompanying an increase in the number of sliding times. Increase in contact resistance was observed. The difference in tendency between the two is considered to be due to the difference in the distribution of Ni fine particles in the sintered film.

  The above wear resistance test results also indicate that the Ni fine particle content is preferably 0.5 parts by mass or less.

  As described above, according to the present invention, an alloy film having substantially the same electrical characteristics, adhesion, and wear resistance as conventional electroplating or chemical plating without using conventional electroplating or electroless plating. It has been demonstrated that a method for producing a metal film-formed product that can be formed in a fine region on a substrate can be provided.

  Note that the above-described embodiments have been specifically described in order to help understanding of the present invention, and the present invention is not limited to having all the configurations described. For example, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, a part of the configuration of each embodiment can be deleted, replaced with another configuration, or added with another configuration.

  DESCRIPTION OF SYMBOLS 1 ... Base material, 2 ... Coating film, 3 ... Laser beam, 4 ... Laser sintered film, 10 ... Metal film formation product, 20 ... Ni-Au laser plating area (0.8 mm (PHI)), 30 ... Co-Au electroplating area | region , 40 ... diffusion layer, 41 ... main phase (melted layer of first metal fine particles), 42 ... second metal fine particles, 43 ... diffusion layer to the main phase of second metal fine particles, 60 ... Ni-Au laser Sintered film, 61 ... Ni fine particle, 70 ... Abrasion resistance evaluation test apparatus, 71 ... XY stage, 72 ... Z-stage, 73 ... Load, 74 ... Load cell, 75 ... Actuator, 76 ... Test piece, 81 ... Current 82, Voltmeter, 83 Female terminal, 84 Co-Au electroplated film, 85 Male terminal, 86 Ni-Au laser plated film, 87 Sliding direction.

Claims (8)

A coating step in which a dispersion in which two or more kinds of metal fine particles are dispersed in a solvent is applied to the surface of the substrate to form a coating film;
Have a, and the laser beam irradiation step of forming a laser-sintered containing the fine metal particles in a solid solution alloy is irradiated with a laser light to the coating film on a surface of the substrate,
The metal fine particles are composed of metal fine particles composed of metal elements constituting the main phase, and metal fine particles composed of metal elements that can be dissolved in the main phase,
The average particle diameter of the metal fine particles composed of the metal element constituting the main phase is 1 to 10 nm or less, the average particle diameter of the metal fine particles composed of the metal element that can be dissolved in the main phase is 10 to 100 nm,
The metal is characterized in that the content of metal fine particles composed of a metal element that can be dissolved in the main phase is 0.1 to 0.5 parts by mass with respect to the metal element constituting the main phase of the dispersion. A method for producing a film-formed product. A metallic element gold or silver constituting the main phase process according to claim 1, wherein the metal coating formed article, wherein the metal element capable solid solution in the main phase is nickel, cobalt or chromium . The alloy has a structure in which metal fine particles composed of metal elements constituting the main phase and metal fine particles composed of metal elements that can be dissolved in the main phase are completely solid solution or partially solid solution. The method for producing a metal film-formed product according to claim 1 or 2 . The laser beam is claims 1 to any one of the 3, characterized in that a laser diode laser with a wavelength of the second harmonic or 915nm of YAG laser having a wavelength of Neodymium Yag laser, 532 nm with a wavelength of 1064nm the method for producing the metal skin film formed article according to claim. The method for producing a metal film-formed product according to any one of claims 1 to 4 , wherein the base material is a copper-based alloy. The process according to claim 5, wherein the metal skin film formed article, wherein the copper-based alloy is phosphor bronze, brass, Corson copper alloy or a magnesium copper alloy. Further, the during the coating process and the laser beam irradiation step, any one of claims 1 to 6, characterized in that it has a drying step of removing the solvent of the coating film the in the coating film by drying the method for producing the metal skin film formed article according to (1). Said substrate is a metal terminal having an electrical contact portion, the laser sintered film, the metal skin layer formed of any one of claims 1 to 7, characterized in that formed on the electrical contact portion Product manufacturing method.

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