JP6656555B2 - Manufacturing method of metal film-formed product - Google Patents

Description

The present invention relates to the production how the metal film forming products.

  In the formation of precious metal films on the hermetic seal (terminal sealing by solder connection or glass sealing) of optical fiber connector terminals and on the surface of metal terminals for electrical contacts, the cross-sectional shape of the substrate on a circular or polygonal substrate Partial metal film formation is required. For example, in an optical fiber connector, a gold film is formed at the end of a cylindrical glass fiber, aligned with a seal ring of Kovar alloy or the like, and sealed with solder bonding or molten glass. In the electrical contact connector terminal, the male terminal has a rod shape with a circular cross section, and a low contact resistance gold film is formed in a portion that contacts the female terminal.

  Conventional techniques for forming a metal film on the surface of these substrates include an electroplating method, a chemical plating method (electroless plating method), and a vapor deposition method. The electroplating method is mainly a method of forming a film on a conductive metal surface, and the chemical plating method is known as a method of forming a film on a metal surface or a nonconductive resin surface. These are all wet film forming methods. On the other hand, methods practically used as a vapor phase film formation method include vapor deposition, sputtering, and CVD (Chemical Vapor Deposition). The wet electroplating method and the chemical plating method use many chemicals and use a large amount of washing water for surface cleaning, and thus have a problem of environmental pollution of water to rivers and the like. Since the vapor phase film forming method is a non-wet method, there is no problem of the above-mentioned wet method, but there is a problem that equipment costs increase, such as using a large and expensive vacuum chamber.

  The biggest problem of the film forming method by the wet method and the chemical vapor method is that it is very difficult to selectively form a partial film on a substrate. For example, in a semiconductor device, when performing on-demand micro-part plating (plating only at a required part (micro-part) only) on an electrode pad joint, a method other than film formation such as formation or peeling of a plating mask is used. The process is very expensive. In particular, in vapor phase film formation, there is a method of using a metal mask for partial film formation, but it is necessary to recover a noble metal attached to the mask. When the base material such as an optical fiber is glass, a method of performing chemical plating by attaching a palladium catalyst to a substrate having a roughened plating surface is used. In such partial film formation using the wet plating method, there is a problem that equipment (a processing liquid, a processing tank, etc.) in each processing step such as a chemical processing step, a cleaning step, and a waste liquid processing step is required. Further, in the chemical plating method, a trace amount of eluted substance from the plating resist film may stop a normal reaction of the chemical plating solution, and it is difficult to perform partial plating not only in terms of cost but also in the process. In addition, in the electroplating method, dedicated plating resist processing equipment (for example, a photoresist process in a semiconductor process) and a process are required to partially form a metal film on the surface of the base material.

  Recently, as a film forming method other than the film forming method by the wet method and the chemical vapor method, a method of forming a metal film on a substrate surface of a metal or a non-conductive material using metal nanoparticles has attracted attention. In this method, a metal nanoparticle ink (paste) is partially applied to the surface of a base material, and then a metal film is partially formed on the base material by furnace firing or laser sintering. The metal nanoparticle paste has features of being excellent in ink jet printing and partial applicability by a dispenser, and capable of being sintered at a low temperature equal to or lower than the melting point of the metal. In particular, the laser sintering method is characterized in that it can be sintered in less than one second as compared with furnace sintering, and that the quality of the sintered film is excellent in that there are few voids. Furnace sintering usually requires heating at a temperature of 230-300 ° C. for about one hour, and has problems such as oxidation of the base material. However, laser sintering is a method that completes sintering in a short time. In addition, there is an advantage that oxidation of the substrate hardly occurs.

  This laser sintering method is also a film forming method utilizing the optical characteristics of the metal nanoparticle paste. By selecting the wavelength of the laser that has the optimal absorptance for the metal nanoparticle paste and the substrate, a metal film with no voids and excellent adhesion to the substrate is formed on the substrate. Can be formed. The irradiated laser light is partially absorbed by the metal nanoparticle paste, but is partially transmitted to the base material and heats and raises the temperature of the base material surface. Start bulking into crystals. For this reason, in the case of a metal substrate, mutual thermal diffusion of metal atoms and metal nanoparticles occurs simultaneously with the bulking of the metal nanoparticles, and high adhesion at the interface can be obtained. In particular, by irradiating the metal nanoparticles with laser light having a wavelength of near-infrared light having a lower absorptance, the laser light is absorbed by the substrate, heating and sintering occur from the substrate side, and the sintered film and the base High adhesion to the material can be obtained.

  According to such a dry laser sintering method, a large-scale facility such as electroplating or chemical plating is not required, and a film is locally formed without forming a plating mask on a substrate surface. Therefore, the amount of noble metal used can be reduced, and a low-cost, highly adherent metal film-formed product can be obtained. A method for manufacturing a metal film-formed product using a laser sintering method is described in, for example, Patent Document 1 and Non-Patent Document 1 below.

  Patent Literature 1 discloses a method for forming a metal film on a surface of a base metal by plating a noble metal on a surface of the base metal, and irradiating a laser beam to the surface of the base metal to form a passive film formed on the base metal. A surface activation step of decomposing and removing, and a noble metal nanoparticle dispersion liquid coating step of applying a noble metal nanoparticle dispersion liquid in which noble metal nanoparticles are dispersed in a solvent to the surface of the base metal on which the passive film has been decomposed and removed. A method for forming a metal film, comprising: a noble metal nanoparticle sintering step of sintering the noble metal nanoparticles by irradiating a laser beam to the noble metal nanoparticle dispersion applied to the surface of the base metal. is there.

  Further, Patent Document 1 has a liquid repellent coating step of coating a liquid repellent on the surface of the base metal before the surface activation step, and the surface activation step further includes the base metal. A method for forming a metal film, wherein the application area of the noble metal nanoparticle dispersion is limited by decomposing and removing the liquid repellent coated on the surface of the metal film. By applying a dispersant on the surface of the base material and then partially removing the water repellent by laser irradiation, the metal nanoparticle dispersion can be selectively applied to the locations where the water repellent has been removed. It becomes possible to partially form a laser sintered film of metal nanoparticles on a material.

Patent No. 5760060

Katsuhiro Maekawa et al. (2012). Laser sintering technology for printed electronics: Fine wiring and functional film formation using silver nanoparticle paste Journal of Japan Institute of Electronics Packaging, 15 [1], 96-105.

  Hereinafter, problems to be solved by the present invention will be described. Each of the laser beam sources used in Patent Document 1 and Non-Patent Document 1 described above is a circular beam in which the shape of the laser beam projected onto the substrate is called a spot beam. The spot diameter, which is the diameter of the circular beam, is indicated by a theoretical value at the focal point of the laser condenser lens. In a spot beam, the energy intensity distribution is a Gaussian distribution in which the energy is higher at the center of the beam and decreases toward the outer periphery of the spot. When a metal nanoparticle sintered film is partially formed on the surface of a base material having a circular or square cross section using this spot beam laser, laser light irradiation must be performed on the side surface in multiple parts. However, as a result, there is a problem that the thickness and quality of the sintered film are not uniform over the entire sintered film.

In view of the above circumstances, the present invention provides a laser sintering method in which a dispersion containing metal particles is applied to the surface of a substrate to form a coating film, and the coating film is irradiated with laser light to obtain a sintered film of metal particles. in technology (laser plating technique), a uniform overall thickness and quality film, and aims to provide a manufacturing how the metal coating formed article having excellent adhesion to the coating and the substrate.

In order to achieve the above object, the method for manufacturing a metal film-formed product according to the present invention includes, as laser light applied to the coating film, a ring beam having an annular condensing portion , A configuration using a laser beam having a spot beam having a condensing portion was adopted .

  More specific configurations of the present invention are described in the claims.

  According to the present invention, in a laser sintering technique of applying a dispersion containing metal particles to the surface of a substrate to form a coating film, and irradiating the coating film with laser light to obtain a sintered film of metal particles, It is possible to provide a method for producing a metal film-formed product having a uniform film thickness and film quality as a whole, and excellent adhesion between the film and the substrate, and a metal film-formed product.

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

It is a flowchart which shows an example of the manufacturing method of the metal film formation product which concerns on this invention. It is a flowchart which shows the other example of the manufacturing method of the metal film formation product which concerns on this invention. FIG. 3 is a flowchart illustrating in detail a part (S21 to S23) of the flow in FIG. 2 together with a cross-sectional view. It is a figure which shows the condensing part of a ring beam, and its energy density distribution typically. It is a figure which shows typically the beam condensing part which combined the ring beam and the spot beam. It is a schematic diagram which shows an example of the base material in which the coating film was formed. It is a schematic diagram which shows the other example of the base material in which the coating film was formed. It is a figure which shows the flat-plate-shaped base material and the droplet of the dispersion liquid typically. It is a schematic diagram which shows an example (metal terminal) of the metal film formation product which concerns on this invention. FIG. 2 is a schematic cross-sectional view illustrating an optical system of laser light according to the first embodiment. FIG. 2 is a cross-sectional view schematically illustrating a pure copper terminal (rod-shaped terminal) and a tin microparticle sintered film in a laser irradiation step in Example 1. FIG. 3 is a schematic diagram showing an inert gas atmosphere cell used in a laser irradiation step in Example 1. 4 is a photograph showing a rod-shaped terminal after a coating film forming step in Example 1. 4 is a photograph showing a rod-shaped terminal (tip portion of a base material) after a laser irradiation step in Example 1. 4 is a photograph showing a rod-shaped terminal (a central portion of a coating film) after a laser irradiation step in Example 1. 4 is a photograph showing a rod-shaped terminal (below a coating film) after a laser irradiation step in Example 1. It is a cross-sectional observation photograph of FIG. 13B. 4 is an observation photograph of a side surface of the optical fiber manufactured in Example 2.

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

[Production method of metal film-formed product]
FIG. 1 is a flowchart illustrating an example of a method for manufacturing a metal film-formed product according to the present invention, and FIG. 2 is a flowchart illustrating another example of a method for manufacturing a metal film-formed product according to the present invention. As shown in FIG. 1, the method for producing a metal film-formed product according to the present invention includes a metal particle dispersion production step (S10) of mixing metal particles and a solvent to produce a metal particle dispersion, A coating film forming step of applying the liquid to the surface of the base material to obtain a coating film (S11); and a laser beam irradiation step of irradiating the coating film with a laser beam to obtain a sintered film of the metal particles (S12). As an essential step. Further, as shown in FIG. 2, between the coating film forming step and the laser beam irradiation step, a drying step of heating the coating film applied to the surface of the substrate to dry and remove the solvent contained in the dispersion (S22). May be provided. Hereinafter, each step will be described in detail with reference to the flowchart having the drying step in FIG.

(1) Metal particle dispersion production step (S20)
In the metal particle dispersion production step, metal particles serving as a raw material of a metal film to be formed on a substrate and a solvent for dispersing the metal particles are mixed to obtain a metal particle dispersion (ink). If necessary, a particle binder (binder) or a viscosity modifier may be further added to the metal particle dispersion. As the metal particles, those that can be sintered in the laser light irradiation step described later can be selected in consideration of the use of the metal film-formed product. Specifically, Sn (tin) Cu (copper), Au (gold), and Ag (silver) nanoparticles and microparticles can be used. When metal nanoparticles are used, commercially available nanoparticles having an average particle diameter of 5 to 30 nm (5 nm to 30 nm) can be used. In general, a monomolecular film of an organic compound chemically bonded to a metal nanoparticle is formed on the surface of the metal nanoparticle to keep the metal nanoparticle having a high surface energy stable without agglomeration in a dispersion liquid (in a solvent). Have been.

  When the substrate is a transparent material such as a glass fiber that does not absorb laser light, silica-coated nanoparticles coated with silica, which is a component of the substrate, can be used as the metal particles. When a silica-coated nanoparticle covered with a silica thin film is irradiated with laser light having a wavelength of near-infrared light, the silica coat is destroyed and the nanoparticle sinters, and passes through a sintered silica film constituting the silica coat. In addition, a metal particle sintered film and a substrate such as glass can be joined, and high adhesion can be obtained.

  Also, microparticles can be used as the metal particles. Since special measures are required to form a dispersant on nanoparticles, the use of nanoparticles contributes to an increase in manufacturing cost.However, microparticles have a dispersant like nanoparticles. Since it is unnecessary, the manufacturing cost can be reduced.

  Furthermore, when using microparticles, the thickness of a coating film that can be formed in one application is larger than when using nanoparticles, so the number of coatings when obtaining a coating film with a large thickness should be reduced. And the effect that the cost can be reduced can be obtained. When the coating thickness of the nanoparticles is increased, the solvent cannot be completely dried and remains in the drying before laser irradiation, so that it is difficult to obtain a dense laser sintered film. On the other hand, in the case of microparticles, since the gap between the particles is large, drying is easy, so that a thick film can be applied, and a thick laser sintered film can be formed by one application. In the case of metal nanoparticles, the laser sintered film thickness that can be formed by one application of the metal nanoparticle ink is about 0.5 μm. On the other hand, for example, with a copper microparticle ink having an average particle diameter of 1 μm, a laser sintered film having a maximum of 20 μm can be formed by one application.

  The average particle size of the microparticles is preferably 1 to 3 μm. If it is less than 1 μm, the effect of reducing the number of times of application described above cannot be obtained remarkably, and if it is more than 3 μm, it becomes difficult to perform sintering in a laser beam irradiation step described later.

  The solvent in which the metal microparticles are dispersed is not particularly limited, but is preferably a solvent that easily evaporates in a heat treatment (about 80 to 150 ° C.) in a drying step described later. Specifically, organic solvents such as ethanol (boiling point: 78.3 ° C.) and methanol (boiling point: 64.5 ° C.) are preferred.

  In addition to the metal particles and the organic solvent, the dispersion may also contain a particle binder and a viscosity modifier as additives. These additives are dried and removed by a heat treatment in a drying step (S22) to be described later, or a solvent having a low boiling point (350 ° C. or lower) that completely decomposes in a laser beam irradiation step (S23), or a low molecular weight. It is preferable to use (10,000 or less) organic compounds. Specifically, ethyl cellulose (molecular weight: 1,000 to 3,000) is effectively used as a particle binder, and decanol (boiling point: 231 ° C.) or castor oil (boiling point: 313 ° C.) is effectively used as a viscosity modifier. Can be.

(2) Coating film forming step (S21)
FIG. 3 is a flowchart illustrating a part (S21 to S23) of the flow in FIG. 2 in detail together with a sectional view. As shown in FIG. 3, the prepared dispersion is applied to a substrate 1a to form a coating film 2. The application method is not particularly limited, and various ink application methods such as an inkjet method, a dip coating method, and a dispenser method can be used. The application amount of the dispersion is determined according to the thickness required for the sintered film obtained after the laser light irradiation step (S23) described later. Before the coating film forming step (S21), the base material 1a may be subjected to a water repellent treatment in advance in order to suppress the spread of the dispersion from the coating area. As the water repellent, a fluorine-based release agent can be used in addition to a silicone-based release agent.

  As the shape of the base material 1a, a shape having a shape capable of irradiating a ring beam used in a laser light irradiation step described later is preferable along the entire periphery of the surface. That is, a curved body having a surface capable of adjusting the diameter of the converging portion of the ring beam can be preferably used. When a substrate having such a shape is used, the effects of the present invention can be sufficiently exerted. More specifically, as the substrate having a curved surface, a columnar (rod-shaped) substrate, a hollow cylindrical substrate (a substrate having a hollow cylindrical interior), a conical substrate, and the like can be used. It can be preferably used.

  In addition, a polyhedral base material such as a quadrangular prism can be used as the base material 1a. In the case of a polyhedral base material, the ring beam cannot be irradiated along the entire circumference of the coating film on the base material surface, and there are portions irradiated with laser and portions not irradiated with laser along the circumference of the base material However, due to heat conduction from the portion irradiated with the laser, the coating film in the portion not irradiated with the laser is also sintered. As a result, as in the case of the above-mentioned curved substrate, a sintered film having a uniform thickness and film quality can be obtained over the entire periphery of the coating film formed on the surface of the substrate. Further, a spherical base material and a flat base material can be used as the base material 1a. In the following description, the substrate 1a is a hollow cylindrical substrate.

(3) Drying step (S22)
Next, the coating film 2 is heated to dry and remove the solvent contained in the coating film 2. The drying temperature is preferably a temperature equal to or higher than the boiling point of the solvent and lower than the boiling point of the dispersion (a temperature at which sintering of the metal particles does not start). If the drying temperature is set to a temperature higher than the melting point of the metal particles (for example, 300 ° C. or higher), the metal particles in the dispersion liquid are sintered before the laser light irradiation, so that voids are generated in the sintered film obtained after the laser light irradiation. As a result, a dense sintered film cannot be obtained, and as a result, the adhesion between the substrate and the laser sintered film is reduced.

  The thickness of the dried coating film 3 can be adjusted by the concentration of the dispersion used in the above-described coating film forming step and the amount of the applied liquid. The higher the ink concentration and the greater the amount of application, the greater the thickness of the coating film 3 after drying.

(4) Laser beam irradiation step (S23)
Next, the coating film is irradiated with laser light to obtain a sintered film. In the present invention, a “ring beam” having an annular condensing portion is used as laser light. FIG. 4A is a diagram schematically showing a condensing portion of a ring beam and its energy density distribution. As shown in FIG. 4A, the ring beam has an annular condensing portion 80, and the energy density has a peak near the outer periphery (A in FIG. 4A) or the inner periphery (B in FIG. 4A) of the ring. It has an intensity distribution. Since the energy density is constant within the same circumference in the annular condensing section 80, if the condensing section 80 irradiates a ring beam along the coating film formed on the base material surface, the coating film Can be irradiated with laser light of a constant intensity over the entire circumference of. As a result, a sintered film having a uniform thickness and quality can be obtained over the entire circumference of the coating film formed on the base material. In the present invention, the uniform film quality of the sintered film means that there is no unsintered portion, there is no void interposed in the film, and there is no pinhole.

  FIG. 4B is a diagram schematically illustrating a beam condensing portion obtained by combining a ring beam and a spot beam. As shown in FIG. 4B, in the present invention, a ring beam having an annular condensing portion 80 and a spot beam having a point-shaped condensing portion 81 may be used in combination as laser light. The spot beam is a point-shaped condensed beam having a Gaussian distribution type energy density distribution, which has a point-shaped condensing part and the central part of the condensing part has the highest energy density. When such a beam is used, the coating film formed on the outer surface of the hollow cylindrical substrate and the coating film formed on the inner surface can be simultaneously sintered. Alternatively, the coating film formed on the end face of the base material and the coating film formed on the side face of the base material can be simultaneously sintered. Since the output of the ring beam and the output of the spot beam can be controlled independently, it is possible to sinter the coating film on the end face and side face of the base material with the minimum output necessary for sintering, respectively. It becomes possible. This point will be described in detail in Examples.

  When a spot beam is used as a laser beam instead of a ring beam, in order to sinter a coating film formed on the surface of a base material such as a curved body, a polyhedron, and a sphere, a plurality of pieces are formed along the length direction of the base material. It is necessary to irradiate (scan) the laser light over each time, but the present inventors have found the following problem in such a case.

(1) It is necessary to irradiate the laser several times in the circumferential direction, and the efficiency is poor. (2) When the laser irradiation is performed in a plurality of times, the film quality of the boundary part is different, so that it is uniform in the circumferential direction. (3) Changes in mechanical properties of the substrate due to multiple laser irradiations, oxidative deterioration, etc. (4) When the substrate is metal, changes in the metal structure due to multiple laser irradiations (Crystal coarsening, growth of intermetallic compounds, etc.) and breakage due to thermal damage. (5) When the base material is resin, deformation, melting breakage, and burnout breakage due to heat damage. In the case of inorganic materials such as quartz, melt deformation or disconnection occurs. (7) When the laser beam position is fixed and the base material is rotated and sintered, the metal applied in the circumferential direction can be obtained by rotating the base material once. Although sintering of nanoparticle films is possible, laser Since morphism start and end can (one rotation of the start and end points) of overlapping uneven points sintered film in terms not uniform film was obtained in the circumferential direction.
As described above, when sintering the entire circumference of a base material such as a curved body, a polyhedron, and a sphere using a spot beam, avoid a double irradiation at a place where laser light is irradiated or, conversely, avoid a double irradiation. Irradiation in this way may result in portions where laser light is not irradiated. When such a situation occurs, it becomes difficult to obtain a sintered film having a uniform thickness and a thickness over the entire circumference of the coating film formed on the base material.

  Also, the base material is fixed, and the spot beam is scanned from one end to the other end of the base material along the longitudinal direction, or the spot beam is fixed, and the base material is moved in the longitudinal direction of the base material and irradiated. In the case, since the energy density at the center of the spot beam is extremely high and the energy density at the peripheral portion is low, when an attempt is made to sinter a coating film to be irradiated on a portion where the energy density of the spot beam is low, Problems such as fusing of a portion irradiated with the center of the spot beam occur. In order to prevent this fusing, it is necessary to arrange a filter at the center of the Gaussian distribution having a high energy density to reduce the energy density at the center.

  As described above, when a metal film is partially formed on a base material such as a curved body, a polyhedron, and a sphere by a conventional laser sintering method using a spot beam, the entire surface of the base material may not be covered. As a result, a laser beam cannot be irradiated at the same time, and a sintered film having a uniform film thickness and film quality cannot be obtained. The present inventors formed a spot beam laser beam into a ring beam using a lens, thereby simultaneously sintering the entire circumference of the surface of a base material such as a curved body, a polyhedron, and a sphere, thereby reducing the film thickness and film quality. The inventors have found that a uniform laser sintered film can be formed, and have completed the present invention. By using a ring beam, laser light having a uniform energy density can be emitted over the entire circumference of the base material, and thus it is not necessary to dispose a filter as described above.

  In order to obtain a ring beam, in the flow of FIG. 3, before the laser beam irradiation step (S23b) on the substrate 1a, the laser beam shaping step (beam shaping step) of shaping the spot beam 4 into the ring beam 7 (S23a) )have. As a beam shaping optical element that can obtain a ring beam, there is a spatial light modulator that can display arbitrary phase information on sub-micrometer pixels and transmit or reflect the beam to control the wavefront shape, The element is expensive and may be damaged by irradiation with high-intensity laser light. Therefore, it is preferable to shape the ring beam 7 using an optical system including the axicon lens 5 and the convex lens 6. With this optical system, high-intensity laser light irradiation and beam width control become possible.

  FIG. 5 is a schematic diagram illustrating an example of a substrate on which a coating film is formed, and FIG. 6 is a schematic diagram illustrating another example of a substrate on which a coating film is formed. In FIG. 5, a coating film 2 is formed on the outer surface of a hollow cylindrical substrate 1a. In this case, the position of the ring beam 7 and the position of the base material 1a are adjusted so that the coating film 2 formed on the outer surface of the base material 1a fits between the inner diameter 82 and the outer diameter 83 of the converging portion 80 of the ring beam 7. The position and the size of the light collector 80 are adjusted.

  In order to irradiate the entire surface of the coating film 2 with the ring beam 7, the substrate 1a or the ring beam 7 is moved so that the condensing unit 80 scans over the coating film 2. Either the substrate 1a or the ring beam 7 may be moved, but it is easier and preferable to move the substrate 1a. The moving direction of the base material 1a is not particularly limited, but the moving direction of the coating film 2 from the end of the coating film 2 opposite to the end overlapping with the end of the base material 1a (portion 10a in FIG. 5). It is preferable to set the direction (the direction of the arrow in FIG. 5) toward the end (the portion 10b in FIG. 5) overlapping the end of the substrate 1a. If the drying step is not performed after the application of the coating film 2, the coating film may flow from the end 10 a of the coating film, and a sintered film of a desired size may not be obtained. By doing so, such a situation can be prevented.

  In FIG. 6, a coating film is formed on the inner surface of a hollow cylindrical base material. In this case, the position of the ring beam 7 and the position of the base material 1a are set so that the coating film 2 formed on the inner surface of the base material 1a fits between the inner diameter 82 and the outer diameter 83 of the converging portion 80 of the ring beam 7. And the size of the light collecting unit 80 are adjusted. As described above, according to the present invention, a sintered film having uniform film quality and thickness can be formed on the inner surface of the cylindrical substrate 1a. It is extremely difficult to partially form a metal film inside a cylindrical base material by a film forming method such as a wet method or a chemical vapor method. The direction of movement of the substrate 1a is not particularly limited, but, as in the case of FIG. 5, from the end 10a of the coating film 2 opposite to the end overlapping with the end of the substrate 1a, from the end 10a of the substrate 1a. It is preferable to set the direction toward the end 10b overlapping the end (the direction of the arrow in FIG. 6).

  When the base material is a hollow cylindrical member and has a coating film on both the outer surface and the inner surface of the base material, if the laser beam combining the ring beam and the spot beam shown in FIG. The coating film on the outer surface and the inner surface can be simultaneously sintered. That is, the coating film formed on the outer surface of the substrate by the ring beam can be sintered, and the coating film formed on the inner surface of the substrate by the spot beam can be sintered. By simultaneously sintering the outside and inside of the substrate, the production time can be reduced. When a coating film is formed on the end surface of a curved or polyhedral base material, both the coating film formed on the end surface of the base material and the coating film formed on the side surface of the base material are simultaneously sintered. Therefore, the manufacturing time can be reduced.

  FIG. 7 is a diagram schematically showing a flat substrate and droplets of a dispersion. Until now, the effect when the hollow cylindrical base material is used has been described, but the effect when the base material is flat is described below. As shown in FIG. 7, the thickness of the droplet 60 formed by dropping the dispersion liquid on the surface of the flat base material 1 b is larger at the peripheral portion 62 of the droplet 60 than at the central portion 61. This is because the drying of the solvent in the peripheral portion 62 occurs more actively than the central portion 61, and the metal particles in the dispersion liquid move to the peripheral portion where the drying of the solvent is active. Or it is called coffee stain phenomenon.). In the present invention, in the laser light irradiation step, the laser light is applied to the droplet 60 so that the annular condensing portion of the laser light overlaps the peripheral edge 62 of the droplet 60, so that The laser beam can be focused. In the case of a spot beam having a Gaussian distribution, since the energy intensity at the center is high and the energy at the outer periphery is low, a complete sintered film at the outer periphery cannot be obtained. The central portion 61 not directly irradiated with the ring beam is sintered by heat conduction from the peripheral portion 62 to which the ring beam is irradiated.

  The wavelength of the ring beam 7 is preferably from 800 to 1200 nm. Practical laser light sources include a neodymium yag (Nd: YAG) laser having a wavelength of 1064 nm, a second harmonic of a YAG laser having a wavelength of 532 nm, or a laser diode (Laser Diode; LD) laser having a wavelength of 915 nm. It is preferable to select in consideration of light reflection, absorption, and transmission spectrum data of each metal particle contained in the dispersion liquid, and light reflection and absorption spectrum data of the substrate 1. As the laser output mode, either a standing wave (CW laser) or a pulse wave can be used. However, since the physical properties of the sintered film differ in the laser output mode, the laser beam is selected according to the type of the metal particles and the base material 1. Is preferred. When microparticles are used as metal particles, it is preferable to use pulsed laser light. The details of laser sintering of microparticles using pulsed laser light are described in detail, for example, in Japanese Patent No. 5859075.

  According to the method for producing a metal film-formed product according to the present invention described above, chemical treatment, cleaning step, waste liquid treatment, and the like, which are required for conventional plating, are not required, and a reduction in the amount of raw material used for the metal film can be expected. As a conventional technique, welding and heat treatment of a base material using a ring beam are known. However, forming a metal film (sintered film) on a base material using a ring beam is a novel and unprecedented technique. Is the way. The following describes a reference regarding processing of a metal member using a ring beam as a reference.

  Reference 1: JP-A-2010-194558, Reference 2: JP-A-2013-75331, Reference 3: JP-A-2004-291031, Reference 4: JP-A-2004-291031, Reference 5: Yu Aratani (2014). First Laser Welding (First Welding Series), Sanho Publishing, 84-85. Reference 6: Welding of cylindrical resin nozzle by laser, Hamamatsu Industrial Technology Center research results casebook, published in 2006 (research in 2005), 32, Reference 7: Laser Platform Association (2010). Introduction to Laser Manufacturing II-From equipment introduction to process development, Sanpo Publishing, 85-89.

[Metal film forming product]
Next, a metal film-formed product manufactured by the above-described method for manufacturing a metal film-formed product according to the present invention will be described. FIG. 8 is a schematic view showing an example (metal terminal) of the metal film-formed product according to the present invention. By the above-described method for manufacturing a metal film-formed product according to the present invention, the metal terminals 800 (male terminal) and 801 (female terminal) shown in FIG. 8 and a hermetic seal of an optical fiber can be manufactured. The metal film 9 has a sintered body having a melt-solidified structure formed on a surface of a curved body, a polyhedron, and a sphere base material, and has a laser scanning boundary portion (when laser irradiation is performed a plurality of times). (Patterns between the scans generated during the scanning). It can be confirmed by microscopic observation that the metal film has a melt-solidified structure and has no laser scanning boundary.

  Hereinafter, the present invention will be described in more detail based on examples.

  In Example 1, a columnar pure copper terminal (rod-shaped terminal, size: φ0.8 mm × 25 mm) was used as the substrate 1 c, and a metal film-formed product having a tin sintered film as a metal film on the surface of the substrate was produced. . Tin ink particles (tin paste) having compositions shown in the following table (Table 1) were prepared by using tin microparticles (average particle diameter φ2.5 μm) of SFR-Sn of Japan Atomize Processing Co., Ltd. as tin particles. In Table 1, PVP is an additive for making the coating film uniform.

  For uniform dispersion of the solvent and binder and the tin microparticles, a stirrer (AR-100) manufactured by Shinky Corporation was used. In the tin microparticle paste prepared by this method, a copper terminal degreased by acetone and alcohol immersion was sequentially immersed and vertically pulled up to form a coating film of tin microparticles on the copper terminal surface. A coating film was formed on one end face and a part of the side face of the copper terminal. The coating length was 10 mm. Thereafter, using an electric furnace (MMF-2) manufactured by As One Co., Ltd., the mixture was heated at a temperature of 80 ° C. for 3 minutes to evaporate a solvent component in the coating film to form a tin-microparticle film from which the solvent was removed. Then, the tin microparticle coating film was immediately sintered by a ring beam laser using a CW (Continuous Wave Operation) Nd: YAG laser source having a wavelength of 1,064 nm.

  FIG. 9 is a schematic sectional view showing an optical system of laser light in Example 1, and FIG. 10 is a sectional view schematically showing a pure copper terminal (rod-like terminal) and a tin microparticle sintered film in a laser light irradiation step. is there. The axicon lens 5 has an opening 90 having a diameter of 1.8 mm at the center, and the laser beam passing through the opening 90 at the center becomes a spot beam 4 having a diameter of 1.4 mm, and is applied to the end face of the rod-shaped terminal 1c. Configuration. With such a configuration, the tin microparticle coating film applied to the end face and the side face of the rod-shaped terminal 1 can be simultaneously sintered. In the present embodiment, the spot beam diameter is set to φ1.4 mm, in order to facilitate alignment with a pure copper terminal of φ0.8 mm. The spot beam diameter can be changed by adjusting the focus of the convex lens 6 in addition to the diameter of the opening 90 of the axicon lens 5. As shown in FIG. 9, the outer diameter of the converging portion of the ring beam was 3 mm, and the length of the ring beam at the focal point (converging portion) was 2 mm.

  Using the optical system shown in FIG. 9, a sintered film was formed under the conditions of a laser scanning speed of 4 mm / s, an output of 30 W, and an inert gas atmosphere (argon gas flow rate of 3 L / min). In the present embodiment, the ring beam 7 is scanned by moving the rod-shaped terminal 1c downward. FIG. 11 is a schematic diagram showing an inert gas atmosphere cell used in the laser irradiation step. As shown in FIG. 11, the cell 110 has an inert gas (eg, argon) inlet 111 and an inert gas outlet 112. By inserting the rod-shaped terminal 1c up to the center of the cell 110 and sealing the upper part of the cell with a lid 113 made of heat-resistant glass that can transmit the laser light 114, laser light irradiation can be performed in an inert atmosphere.

  FIG. 12 is a photograph showing the rod-shaped terminal after the coating film forming step in Example 1. 13A to 13C are photographs showing rod-shaped terminals after the laser irradiation step in Example 1. 13A shows the end face (tip) of the rod-shaped terminal 1c, FIG. 13C shows the end opposite to the end of the sintered film 9a of the rod-shaped terminal 1c, and FIG. 13B shows the end of FIG. 13A and FIG. The sintered film 9a in the region between them is shown. FIG. 14 is a cross-sectional photograph of FIG. 13B. As shown in FIGS. 12 to 14, in the present example, a uniform tin sintered film having a thickness of about 30 μm was obtained over the entire circumference of the rod-shaped terminal 1c.

  The obtained sintered film was subjected to a friction test with a cotton swab dipped in acetone, and no peeling of the tin sintered film was observed. Further, the tin sintered film and the copper substrate were soldered, and then a tensile test was performed to evaluate solderability. As the solder paste, a lead-free solder paste (S70G-HF Type4, Sn-Ag3.0-Cu0.5) manufactured by Senju Metal Industry Co., Ltd. was used. As a result of the tensile test, the copper terminal was broken at a tensile load of about 120 N, and no change was observed in the solder joint. From this, it was shown that the tin sintered film produced in this example had good solderability.

  In Example 2, a hollow cylindrical quartz optical fiber (size: Φ125 μm, length 50 mm) was used as the base material 1 d, and a ring laser beam was used over the entire circumference 6 mm from the tip required for hermetic sealing. A nanoparticle sintered film was formed. As the gold nanoparticle ink, a gold nanoparticle paste (Model No. NPG-J, average particle diameter 7 nm) manufactured by Harima Chemicals, Inc. was used. In order to obtain a uniform coating property of the gold nanoparticle paste on the quartz fiber, the quartz fiber was immersed in a 0.1 M / L hydrochloric acid aqueous solution (normal temperature) for 10 minutes to perform a uniform surface activation treatment. Next, a gold nanoparticle paste coating film was formed on the fiber surface by dipping the optical fiber vertically in the gold nanoparticle paste and pulling it up vertically. The immersion time was 10 minutes. The thickness of the gold nanoparticle paste was adjusted by using a dedicated diluting solvent so that the gold film thickness after laser sintering was 0.2 μm.

  The gold nanoparticle paste NPG-J manufactured by Harima Chemicals Co., Ltd. had a coating thickness of 3 μm in order to obtain a laser sintered film of 0.2 μm or more because the film thickness residual ratio after sintering was 10%. Next, a drying step at 100 ° C. for 2 minutes was performed in order to remove excess solvent in the coating film before laser sintering. The sintering of the gold nanoparticle coating film by the ring laser beam was performed using the same optical system as in Example 1 under the following conditions.

Ring laser beam irradiation equipment and irradiation conditions:
(1) Laser beam source; Nd: YAG laser irradiation device (2) Outer diameter of condensing portion of focus ring beam: 3 mm (see FIG. 9), focus ring beam length: 2 mm (see FIG. 9), central portion Spot beam diameter: φ1.8mm (Ring beam molding with two steps of plano-concave lens and two steps of plano-convex lens)
(3) Irradiation method; fiber moving speed 0.5 mm / s (moving the fiber in the longitudinal direction)
(4) Laser output; 1.0 W
(5) Atmosphere; in the air FIG. 15 is an observation photograph of the side surface of the optical fiber manufactured in Example 2. As shown in the figure, a sintered film having a uniform thickness in the circumferential direction was obtained.

  In the third embodiment, an experiment was performed in which a tin sintered film was formed on a pure copper terminal using a lens having no opening for forming a spot beam in the center of the axicon lens 5 of the optical system used in the first embodiment. Was. In the third embodiment, tin sintering is performed only by the ring beam. However, the coating film on the end face is also sintered by heat conduction from the ring beam irradiation part, and the end face and the side face have a uniform thickness similarly to the first embodiment. A tin sintered film could be formed.

  In order to verify the reason, the output of each of the spot beam and the ring beam was measured. As a result, it was found that the spot beam was about 1.3% of the entire output. From this, it is considered that in Example 1, a tin sintered film similar to that of Example 3 was formed. If the output of the spot beam is too high, the tip of the rod-shaped terminal will melt. In the method of the present invention using both the ring beam and the spot beam, an optimum sintered film can be obtained by changing the output ratio of the two beams. In Examples 1 and 3, a pure copper terminal having a diameter of 0.8 mm was used. However, in the case of a rod-shaped terminal having a larger diameter, in order to increase the output of the spot beam, the firing was optimized by increasing the diameter of the opening. Selection of sintering conditions becomes possible.

  As described above, according to the present invention, a dispersion containing metal particles is applied to the surface of a substrate to form a coating film, and the coating film is irradiated with laser light to form a sintered film of metal particles. In the obtained laser sintering technology, it is possible to provide a method for producing a metal film-formed product having uniform film thickness and film quality of the entire film, and excellent adhesion between the film and the substrate, and a metal film-formed product. Has been demonstrated.

  ADVANTAGE OF THE INVENTION According to this invention, when forming a noble metal film on the hermetic seal (terminal sealing by solder connection or glass sealing) part of an optical fiber connector terminal, or the metal terminal surface for electrical contact, a columnar shape, a prismatic shape, a hollow cylindrical shape It becomes possible to partially form a metal film on the surface of the substrate. Furthermore, since a laser sintered film having a uniform film quality can be formed on the inner surface having a hollow cylindrical cross section, a female terminal made of an electrical contact material can be manufactured.

  Further, the effects of the present invention are not limited to the above-described ones, and a laser-sintered film may be formed on the outer surface of a cylindrical, prismatic, or hollow cylindrical substrate, or on the inner surface of a hollow cylindrical substrate. The present invention can be applied to, for example, semiconductor mounting parts, electronic substrates, and other industrial products in general that need to be formed, and can contribute to the development of these industrial fields.

  1a, 1b, 1c, 1d: base material, 2: coating film, 3, 3a: coating film after drying, 4: spot beam, 5: axicon lens, 6: convex lens, 60: droplet, 61: droplet , 62 ... peripheral part of droplet, 7 ... ring beam, 9, 9a, 9b ... sintered film, 10a ... end of coating film 2 opposite to end overlapping base material 1a, 10b An end portion of the coating film 2 overlapping the end portion of the substrate 1a, 10c an application film applied to the end surface of the base material, 60 droplets of a dispersion liquid, 61 central portions of the droplets, 62 droplets of the droplets Peripheral edge, 80: Ring beam focusing section, 81: Spot beam focusing section, 82: Ring beam inner diameter, 83: Ring beam outer diameter, 800: Male terminal, 801: Female terminal, 90: Axicon Lens opening, 100: metal film formed product, 110: cell, 111: inert gas inlet, 1 2 ... inert gas outlet section, 113 ... made of heat-resistant glass lid, 114 ... laser light.

Claims (8)

Mixing metal particles and a solvent, a metal particle dispersion producing step of producing a metal particle dispersion,
A coating film forming step of applying the metal particle dispersion to the surface of a substrate to obtain a coating film,
Irradiating the coating film with laser light to obtain a sintered film of the metal particles,
The method for manufacturing a metal film-formed product, wherein the laser beam includes a ring beam having an annular condensing portion and a spot beam having a point-shaped converging portion at the center of the ring beam . The substrate is curved body, a manufacturing method of claim 1 Symbol mounting metal film forming product characterized by comprising the polyhedron and the sphere. The substrate is a columnar or hollow cylindrical substrate,
In the coating film forming step, the metal particle dispersion liquid is applied to the surface of the substrate, forming a coating film of the metal particle dispersion liquid along the entire circumference of the columnar or hollow cylindrical substrate,
In the laser light irradiating step, the annular light condensing portion of the laser light, the laser light so that along the entire circumference of the coating film provided on the surface of the columnar or hollow cylindrical substrate, the laser light The method for producing a metal film-formed product according to claim 1, wherein the coating film is irradiated. The substrate is a hollow cylindrical substrate,
In the coating film forming step, the metal particle dispersion is applied to the outer surface and the inner surface of the base material, and the metal is dispersed along the entire circumference of the outer surface and the inner surface of the base material. Forming a coating film of the particle dispersion,
The laser light irradiating step includes applying the laser light so that the annular condensing portion of the laser light extends along the entire circumference of the coating film provided on the outer surface of the hollow cylindrical base material. Irradiating the film with the laser light so that the annular condensing portion of the laser light is formed along the entire circumference of the coating film provided on the inner surface of the hollow cylindrical substrate. 2. The method according to claim 1, further comprising the step of irradiating the film. The substrate is a hollow cylindrical substrate,
In the coating film forming step, the metal particle dispersion is applied to the outer surface and the inner surface of the base material, and the metal is dispersed along the entire circumference of the outer surface and the inner surface of the base material. Forming a coating film of the particle dispersion,
In the laser beam irradiating step, the laser beam is applied so that the annular condensing portion of the laser beam extends along the entire circumference of the coating film provided on an outer surface of the hollow cylindrical base material. Irradiating the coating film with the laser light so that the point-like condensing portion of the laser light is formed along the entire circumference of the coating film provided on the inner surface of the hollow cylindrical substrate. The method for producing a metal film-formed product according to claim 1 , wherein the metal film is irradiated. The substrate is a columnar or hollow cylindrical substrate,
In the coating film forming step, the metal particle dispersion is applied to an outer end face and a side face of one end of the base material, and a coating film of the metal particle dispersion liquid is formed along the entire periphery of the end face and the side face. Forming
In the laser beam irradiating step, the annular condensing portion of the laser beam irradiates the laser beam to the coating film along the entire circumference of the coating film provided on the side surface, said point-like light collecting unit of claim 1, wherein the metal coating formed article and irradiating the coating film with the laser beam so as to irradiate the entire surface of the coating film provided on the end face Manufacturing method. The method according to any one of claims 1 to 6 , wherein the metal particles are tin, copper, gold, or silver nanoparticles or microparticles. The method according to any one of claims 1 to 7 , wherein the base material is glass, copper, or a copper alloy.

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