JP2508506B2 - Spherical fine powder manufacturing method and manufacturing apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Prior Art] The present invention relates to the production of spherical fine powder, and more particularly to the production of spherical metal fine powder suitable for forming high-density printed circuits and the like.

[Prior Art and Problems] To form a high-density printed circuit, a paste containing metal fine powder is applied on an insulating substrate to form a desired circuit pattern. The fine metal powder used in this printed circuit is a fine particle of about several thousand angstroms to about ten and several μ. Conventionally, these fine metal particles are produced by (a) a method of reducing a metal oxide, (b) a method of electrolyzing a metal salt aqueous solution, (c) a method of mechanically crushing metal particles. In many cases, the surface of the obtained metal particles is oxidized, and
Since the particle shape is flaky or amorphous, it is not possible to reduce the line width and line spacing of the circuit pattern.
There is a problem that high-density minute circuits cannot be formed.

On the other hand, as a method for producing spherical metal particles, a gas atomizing method, a rotating electrode method and the like have been conventionally known, but it is difficult to produce fine particles having a particle size of 20 μm or less by these methods. In order to form a high-density circuit, fine metal particles of 20 μm or less are necessary, and the above-mentioned manufacturing method is not suitable because the particle size is too large.

There is also known a method in which metal powder is heated by an arc and sintered to form a temporary sphere, which is then placed on a substrate and irradiated with a laser beam to be melted to adjust the shape into a spherical shape (special feature. (Kaisho No. 58-151402), this method requires heating in two steps, and therefore the process is complicated, and it produces relatively large particles, and produces fine particles of about several μm. Not suitable for.

Furthermore, a method of irradiating a solid metal raw material with a laser beam to vaporize the metal and cooling the metal vapor to produce a metal powder is known (Japanese Patent Laid-Open No. 61-1365606). The obtained particles are ultrafine particles having a particle size in the angstrom region and are not suitable for printed circuits. Further, unlike the case of melting the surface, the vaporized vapor is rapidly cooled, so that the particle shape is likely to be indefinite.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for producing metal fine particles, which solves the above problems in the conventional production method. According to the present invention, there is provided a manufacturing method for easily manufacturing fine metal particles having a particle size on the order of several μm, a spherical shape, a low oxygen content, and which is most suitable for manufacturing a printed circuit.

[Structure of the Invention] That is, the present invention provides a method and an apparatus for manufacturing a spherical metal fine powder having the following structure.

(1) The irregular or flaky raw material metal powder is guided to the laser beam irradiation part by a reducing gas flow, and while reducing the surface oxide film, the metal powder is sprayed from a nozzle irradiated with the laser beam to obtain the metal powder. A method for producing a spherical fine powder, which comprises melting and quenching to obtain a spherical metal powder having an average particle diameter of 2.1 to 0.05 μm.

(2) It has a melting and cooling chamber for the raw material metal powder and a collection chamber communicating with the melting and cooling chamber, and the melting and cooling chamber is divided into a melting part and a cooling part by a partition having a hole for guiding a gas flow. The melting section is provided with a laser beam irradiation section and a reducing gas supply path for supplying the raw material metal powder to the focal region of the laser beam, and the cooling section is provided with cooling means. An apparatus for producing spherical fine powder characterized in that

[Detailed Description] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a schematic view of a manufacturing apparatus according to the present invention, and FIG.
The figure is a schematic view of a laser irradiation unit.

(1) Manufacturing Apparatus As shown in the figure, this apparatus has a melting and cooling chamber 10 for melting and cooling the raw material metal powder, and a collection chamber 20 communicating with the melting and cooling chamber 10. The inside of the melting and cooling chamber 10 is divided into a melting portion 10a and a cooling portion 10b by a partition wall 11, and the melting portion 10a and the cooling portion 10b communicate with each other through a hole 17 in the partition wall 11. The melting portion 10a has a laser beam irradiation portion 1
2 is provided, and the irradiation unit 12 has a laser oscillator 13
Is connected. Further, a collector 19 for collecting the unmelted powder is attached to the bottom of the melting section 10a. On the other hand, a cooling pipe 18 for cooling the molten metal powder is provided on the outer periphery of the cooling unit 10b, and a filter unit for collecting the metal powder is housed inside the collection chamber 20. A cooling pipe 23 is arranged on the outer periphery of the cooling pipe 23. Further, the collection chamber 20 is provided with an outlet 21 at the bottom thereof, and an exhaust duct is continuously provided at the top thereof.

On the other hand, as shown in FIG. 2, the irradiation unit 12 is provided with a lens 14 for converging the laser beam and a gas supply path 15 for supplying the raw material powder to the focal region of the laser beam. The gas supply path 15 has a conical nord 16 that opens near the focal point of the laser beam, and the raw material powder is jetted from the nozzle 16 in a direction substantially coaxial with the laser beam by a reducing gas that is a carrier gas. It The ejection direction of the raw material powder is not limited to the coaxial with the laser beam.

(2) Manufacturing method In the natural manufacturing method, a deformed or flaky metal powder is used as a raw material. Here, the irregular shape or the flake shape means an aspherical shape including an indefinite shape. The raw material powder is sprayed by a reducing carrier gas through the gas supply passage 15 from the nozzle 16 irradiated with the laser beam toward the cooling unit 10a. As the reducing gas, hydrogen gas or a mixed gas of hydrogen gas and an inert gas such as nitrogen or argon is used as shown in Examples described later. By using the reducing gas, the surface oxide film of the metal powder is reduced and removed, and the melting by the laser beam becomes uniform and becomes a regular spherical shape. As shown in a comparative example described later, it does not become spherical in a mere inert gas atmosphere.

Regarding the particle size of the raw material powder, the one used as the metal particles for the printed circuit preferably has an average particle size on the order of several μm, and thus a large particle size is not preferable. Further, a method of directly irradiating a metal lump with laser light to vaporize it without using metal powder and cooling the vaporized vapor is not suitable because the grain size is too fine.

The raw material powder is ejected from a nozzle which is irradiated with a laser beam. When the metal powder is simply irradiated with laser light without such gas flow injection, the particles are likely to combine and coarsen, and the melt cooling becomes nonuniform, so the particle size is adjusted to several μ. Spherical particles cannot be obtained.

The optimum amount of raw material powder in the carrier gas and the gas flow rate differ depending on the laser output. For example, in the case of a 5 KW carbon dioxide laser, the amount of raw material powder is appropriately 3 vol% or less. If the amount is larger than this, the raw material powder is not sufficiently melted and the amount of particles that are not spheroidized increases, and the particles are easily bonded to each other.
A suitable gas flow rate is 1000 cm / sec or more at the nozzle port. With this flow rate, particles are unlikely to bond with each other, and fine powder having an average particle size of several μ can be obtained.

The raw material powder introduced into the portion of the nozzle 16 irradiated with the laser beam is melted by the laser beam oscillated from the nozzle oscillation device 13. In this case, heating by the laser beam is limited to near the beam focus,
Immediately after melting, the injected gas flow guides the gas to the cooling section where it is rapidly cooled, so that the melted particles do not combine with each other and become coarse.

When plasma heating is used instead of the laser beam, the heating region is wider than the laser beam, and there is a drawback that the particles are fused with each other and are coarsened while being conveyed to the cooling region. Further, since the temperature of the carrier gas also rises in the plasma heating, there is a problem that even if the carrier gas is out of the heating region, the particles are bound to each other due to the ambient temperature of the carrier gas and become coarse. The laser beam does not have such a problem.

The metal particles melted by the laser beam are guided to the cooling unit 10b through the holes 17 of the partition wall 11, cooled to about 100 ° C., and then collected in the collection unit 20. The carrier gas is discharged to the outside through the exhaust duct 22 and reused as needed. Further, the unmelted powder is collected by the collecting device 19 provided at the bottom of the melting portion.

[Examples and Comparative Examples] Examples 1 to 5 Using the manufacturing apparatus (output 5KW, beam diameter 3 inches, focal length 8 inches) shown in FIG. Below, a spherical powder was produced. The properties of this powder are also shown in the same table. As is clear from this result, all the powders of this example are spherical in shape, and the amount of oxygen is significantly small.

Comparative Examples 1 to 4 Under the conditions shown in Table 1, the spheroidizing of the raw material powder was tried.
The results are summarized in the same table. The powder of Comparative Example 1 does not have a spherical shape, and in Comparative Example 2, irregularly shaped particles and spherical particles are mixed, and the particle diameters of both particles are coarse. Further, the particles of Comparative Examples 3 and 4 are not appropriately melt-cooled and spherical particles cannot be obtained.

[Effects of the Invention] According to the production method of the present invention, spherical particles having a uniform particle size can be easily obtained from a deformed or flaky metal powder as a raw material. Moreover, since the average particle size is about 2 to 0.05 μm, it is suitable as a metal powder used for manufacturing a printed circuit.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a manufacturing apparatus according to the present invention, and FIG. 2 is a partial sectional view of an irradiation part of the apparatus. In the drawing, 10 ... Melting / cooling section, 10a ... Melting section, 10b ... Cooling section, 12 ... Laser beam irradiation section, 15 ... Gas supply path, 18, 23 ... Cooling pipe, 20 ... Collection Room

Claims (2)

(57) [Claims] 1. A metal powder of irregular or flaky raw material powder is guided to a laser beam irradiation section by a reducing gas flow to reduce a surface oxide film, and is jetted from a nozzle irradiated with a laser beam. A method for producing a spherical fine powder, characterized in that the body is melted and rapidly cooled to obtain a spherical metal powder having an average particle diameter of 2.1 to 0.05 μm. 2. A melting and cooling chamber for the raw material metal powder, and a collection chamber communicating with the melting and cooling chamber, wherein the melting and cooling chamber is divided into a melting section and a cooling section by partition walls having holes for introducing a gas flow. The melting section is provided with a laser beam irradiation section and a reducing gas supply path for supplying the raw material metal powder to the focal region of the laser beam, and the cooling section is provided with cooling means. An apparatus for producing spherical fine powder, characterized in that