JP2003225586A - Fine metal particles having narrow particle distribution - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain fine metal particles with a mean particle size of 1-10 μm having a narrow particle distribution and hard to flocculate by an atomizing method. <P>SOLUTION: Fine metal particles obtained by the atomizing method are classified using a precise sieve. The precise sieve used in classification has a thickness of 10-100 μm and the sieve perforations of the precise sieve are formed in a predetermined arrangement so that the opening ratio of them becomes 20-80%. The size of the sieve perforations is 1-10 μm as a diameter in such a case that the plane shape of the sieve perforations is circular and the standard deviation of a pore size distribution is 25% or less of a pore size. Further, when the aspect ratio of each of the perforations defined by the ratio of the depth of perforations to the pore size is not less than 1.5 and the plane shape of each of the sieve perforations is polygonal, the shortest side thereof is 1-10 μm and the standard deviation of a shortest side distribution is 25% or less of the mean value of the shortest sides and the ratio of the depth of each perforation to the length of the shortest side in the projection surface of each perforation is not less than 1.5. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to heating and compression of conductive fine particles having a narrow particle size distribution or a large number of fine particles used for producing an anisotropic conductive adhesive sheet used for connecting terminals of electronic parts. The present invention relates to conductive fine particles having a narrow particle size distribution used for producing a porous metal plate produced in the above manner.

[0002]

2. Description of the Related Art In recent years, particularly in the electrical connection between a plurality of electronic components, not only the size of connection terminals has been reduced, but also the arrangement pitch of the terminals is becoming narrower. This is a movement aimed at increasing the density of parts, and the role played by the material for high-density connection is also extremely important. Therefore, the characteristics relating to the size of the conductive fine particles in the conductive adhesive sheet having anisotropy which is usually used in the narrow pitch connection between the fine terminals are extremely important, and the metal fine particles having a narrow particle size distribution are required. There is.

Further, the fine metal particles are formed by thermocompression bonding,
Regarding the production of porous metal plates used for applications such as filters, the particle size distribution of metal particles is important in controlling the pore size, and metal particles having a narrow particle size distribution are required. Conventionally, an electrolytic method, a chemical vapor deposition method (CVD method), a wet chemical reduction method, or the like has been used as a method for producing metal fine particles. Further, the atomization method, in which the molten metal liquid is rapidly cooled in an inert gas, is also one of the commonly used means because it has the advantage that the content of a plurality of metal components can be controlled. As a method for classifying the metal fine particles produced by these methods, a metal fine particle having a narrowed particle size distribution is formed by classifying by a gas stream classification method, a sedimentation classification method or a classification method using a sieve.

However, the particle size distribution of the metal fine particles classified by the air flow classification method, the sedimentation classification method, etc., has never been wide and satisfactory. As a method for obtaining fine metal particles having a relatively narrow particle size distribution, there is a classification method using a sieve. A method of classifying particles by sieving has existed for a long time, and a sieving in which a wire made of metal or plastic fiber is knitted in a mesh shape so as to form sieving holes (openings) of a predetermined size has been used.

However, in such a conventional sieve, it is necessary to make the wire diameter several tens of μm or more from the viewpoint of mechanical strength. Further, even if it is attempted to reduce the size of the sieve hole, the limit is about several tens of μm. If the sieving hole is a square having a side of 10 μm and the diameter of the wire used is, for example, 20 μm, the area ratio of the sieving hole to the entire surface of the sieving is about 10%, so that the classification speed is extremely low. Furthermore, because it is made by mechanically knitting,
Precise control of the size of the sieve holes is extremely difficult. It has been impossible to produce a sieve having a pore size of 10 μm or less, a strength as a sieve, and a wide opening by the conventional method. That is, the conventional classification method could not produce fine particles having an average particle diameter of 10 μm or less and a uniform particle diameter distribution.

Further, the atomization method is a method of rapidly cooling a molten metal liquid in an inert gas, and in addition to spherical metal fine particles, linear or bent rod-shaped metal fine particles in which a plurality of particles are joined are present. However, the conventional sieve could not separate the rod-shaped metal fine particles. The wet chemical reduction method can produce metal fine particles having a particle size of less than 1 μm and a relatively narrow particle size distribution. With this method, metal fine particles having an average particle size of 1 to 10 μm and a narrow particle size distribution can be produced. It could not be made. In addition, fine metal particles having a particle size of more than 10 μm can be classified by using a sieving method. However, anisotropic metal fine particles for conductive adhesive sheets or fine pores for high-density connection are used. Is not preferable as the metal fine particles for the porous metal plate having

That is, in the prior art, the average particle size is 1 μm.
It was not possible to classify the metal fine particles in the range of m to 10 μm narrowly and efficiently.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and provides metal fine particles having a narrow particle size distribution by a classification operation using a precision sieve. Is an issue.

[0009]

The present invention, which has solved the above-mentioned problems, has the following constitution. 1. Metal fine particles having an average particle diameter of 1 μm to 10 μm and a standard deviation of the particle diameter distribution of 25% or less of the average particle diameter. 2. 2. The metal fine particles according to 1, wherein the odd-shaped particles (particles in which the ratio of the length in the longitudinal direction to the length in the lateral direction is 2 or more) in the metal fine particles is 1% or less.

The metal fine particles according to 3.1 or 2 are
Copper, gold, silver, platinum, nickel, palladium, indium, iron, chromium, tantalum, tin, lead, zinc, cobalt,
Metal fine particles characterized by being titanium, tungsten, bismuth, silicon, antimony, aluminum, magnesium, a rare earth element alone or an alloy of any of these metals, or fine particles having a metal coating on the surface.

4. A method for producing metal fine particles having a narrow particle size distribution by classifying metal fine particles with a precision sieving plate, wherein the metal fine particles are those produced by an atomizing method, and the precision sieving plate used for classification is The thickness is 10 μm or more and 100 μm or less, the sieving holes are formed in a predetermined arrangement so that the opening ratio is 20% or more and 80% or less, and the sieving holes have a circular or polygonal plan shape, and the size of the sieving holes is When the sieving hole has a circular planar shape, the diameter is 1 to 10 μm, the standard deviation of the hole diameter distribution is 25% or less of the average value of the hole diameter, and the ratio of the hole depth to the hole diameter is If the aspect ratio of the hole is 1.5 or more and the planar shape of the sieve hole is a polygon, the shortest side is 1 to 10 μm, and the standard deviation of the distribution of the shortest side is the average value of the shortest side. Below 25% Ri, method for producing metal microparticles, wherein the ratio of the depth of the hole to the length of the shortest side in the projection plane of the holes is 1.5 or more.

5. A method for producing fine metal particles having a narrow particle size distribution by classifying fine metal particles with a precision sieving plate unit consisting of two precision sieving plates, wherein the fine metal particles are produced by an atomizing method. In the sieving plate unit, two precision sieving plates according to item 4 having the same hole arrangement pitch are arranged in parallel at a constant interval,
The two precision sieving plates are arranged so that the overlapping area of the holes is 90% or less when the holes of the two precision sieving plates are projected on the same plane. The distance between the two precision sieving plates is the shortest. A method for producing fine metal particles, which is a precision sieving plate unit having a length of 1.1 to 2.5 times.

6. Assembling a precision sieve plate having the precision sieve plate according to item 4 or the precision sieve plate unit according to item 5 at the bottom of the cylindrical feeding portion for feeding powder for sieving, and assembling the precision sieve plate or precision sieve plate. A method for producing fine metal particles, characterized in that the unit is placed in a container for receiving powder that has passed through a precision sieve so that the unit is on the lower surface, and ultrasonic vibration is applied to the container while the liquid substance is further placed in the container. .

[About Metal Fine Particles] The average particle size of the metal fine particles obtained in the present invention is in the range of 1 μm to 10 μm, and the standard deviation of the particle size distribution is 25% or less, preferably 15% or less of the average particle size. , And more preferably 10% or less. If the average particle diameter is less than 1 μm, variations in height of the connection terminals cannot be absorbed, which is not preferable. If the average particle diameter exceeds 10 μm, it is unsuitable for narrow pitch connection of minute terminals.

Since the metal fine particles of the present invention are used for producing an anisotropic conductive adhesive sheet used for connecting electronic parts or a porous metal sheet by a heat compression method, it is necessary that the particle size distribution is narrow. Become. When the standard deviation of the particle size distribution is large, exceeding 25% of the average particle size, it is difficult for the anisotropic conductive adhesive sheet to absorb the height variation between the connected bumps. In addition, when a porous metal sheet is manufactured, the packing rate of particles becomes high, which makes it difficult to manufacture a porous metal sheet.

The fine metal particles of the present invention preferably have a deformed particle existence ratio of 1% or less. The irregular-shaped particles are particles having a ratio of the length in the longitudinal direction to the length in the lateral direction of 2 or more. If more than 1% of irregular particles are mixed, in the case of a conductive adhesive sheet having anisotropy, the probability that the film thickness direction of the adhesive sheet and the longitudinal direction of the metal fine particles coincide with each other increases, and the terminals connected by the irregular particles are increased. Is destroyed,
Since irregular connection may occur at the peripheral terminals, it is preferable to remove the irregularly shaped particles as much as possible.

The fine metal particles of the present invention include copper, gold, silver, platinum, nickel, palladium, indium, iron, chromium,
Tantalum, tin, lead, zinc, cobalt, titanium, tungsten, bismuth, silicon, antimony, aluminum, magnesium, rare earth elements alone or an alloy of any of these metals, or fine particles having a metal coating on the surface are preferable. . There are methods such as an electrolytic method, a chemical vapor deposition method (CVD method), and a wet chemical reduction method as a method for producing the fine metal particles before classification. In particular, a molten metal liquid is rapidly cooled in an inert gas. The atomizing method is preferably used. According to this method, not only fine particles of one kind of metal but also fine alloy particles composed of a plurality of elements can be produced by controlling the composition thereof. Further, the surface of the produced metal fine particles can be thinly coated with the same or different metals. The metal to be coated may be an element that constitutes the metal fine particles produced by the atomizing method or another element. Examples of the method for coating the surface of the metal fine particles with a metal include an electrolytic plating method, an electroless plating method, a displacement type plating method, a plasma CVD method, a MOCVD method, and a wet chemical reduction method. In any of the methods, it is necessary to form a thin metal layer on the surface of the metal fine particles, and therefore, in order to uniformly deposit the metal, it is necessary to devise such as applying vibration.

[Regarding Precision Sieve Used for Classification] As the material of the precision sieving plate used in the present invention, general-purpose materials such as metal and resin are used. Suitable materials differ depending on the manufacturing method, which will be described later. In the case of a synthetic resin sieve plate, it is preferable to form a metal thin film on the surface thereof in order to prevent the performance of the sieve from being deteriorated by the influence of static electricity. The shape of the holes of the sieve plate used in the present invention is a circle or a polygon. These shapes may be appropriately selected according to the purpose. For example, in the case of a rectangle or an ellipse, rod-shaped particles may pass through the holes not only in the longitudinal direction but also in the lateral direction, but the classification efficiency is good. On the other hand, in the case of a perfect circle or a regular polygon, classification efficiency is slightly inferior to that of a hole having a rectangular shape or an elliptical shape, but it is possible to obtain particles having a narrow particle size distribution.

When the shape of the open hole is circular, the hole diameter is in the range of 1 μm to 10 μm, and when the shape of the open hole is polygonal, the length of the shortest side is 1 μm to 10 μm. And the standard deviation of the pore size distribution is 25% or less of the average value of the pore size. Aperture ratio of sieve plate (total area of sieve holes / area of sieve plate) is 20% to 80%
Is preferred. The numerical value (%) of the aperture ratio is given by (total area of sieving holes / area of sieving plate) * 100. If the aperture ratio is smaller than this range, the classification efficiency is poor, and if the aperture ratio exceeds this range, the strength of the sieving plate becomes low.

The aspect ratio of the holes in the precision sieve is 1.5 or more. Aspect ratio means that when the hole shape is circular,
It is defined by the depth of the hole relative to the diameter of the circle, and when the shape of the hole is a polygon, it is defined by the depth of the hole relative to the length of the shortest side. The precision sieving used in the classification operation of the present invention solves a large problem when classifying metal fine particles of 1 μm to 10 μm in the prior art, low classification efficiency and wide particle size distribution of classified metal fine particles. it can. Furthermore, it has been found that the classified metal fine particles are less likely to aggregate by using a precision sieve having a large aspect ratio of 1.5 or more and by using ultrasonic vibration in a liquid in the classification operation. It was

[Method for Manufacturing Precision Sieve Plate] As a method for forming holes having a large aspect ratio at a high density, a photosensitive resin layer on a conductive substrate is patterned by using photolithography, and then an electrolytic plating method is used. Using the method of depositing metal on the part where the photosensitive resin pattern does not exist, or patterning the resin layer on the conductive substrate using the laser ablation method, and then using the electroplating method to deposit the metal on the part where the resin pattern does not exist. There is a method of precipitation. Alternatively, a method of directly forming holes in a sheet of metal, resin, or ceramics by using laser ablation, or bringing a needle electrode close to a metal sheet in an insulating fluid to cause discharge between the needle electrode and the metal sheet. A method of forming a through hole by gradually inserting a needle-shaped electrode into a metal sheet while making a metal using a pressing die including a male die having a protrusion and a female die having a recess for receiving the protrusion. There is a method of forming a through hole by punching a sheet or a resin sheet with a press.

In the present invention, when the holes are formed by photolithography, it is necessary to pattern the photosensitive resin in the shape of the holes. For example, when the shape of the hole is circular, the diameter of the hole is extremely small, from 1 μm to 10 μm, and the aspect ratio of the hole is 1.5 or more, preferably 2 or more.
As described above, more preferably 3 or more, it is necessary to form a fine and highly photosensitive resin pattern. Therefore, it is necessary to use a photosensitive resin having extremely high resolution. As the photosensitive resin used in the present invention,
Normal high resolution photosensitive resin can be used,
A particularly preferred composition is an unsaturated polyester having a number average molecular weight of 500 or more and 5000 or less obtained by condensation of a dicarboxylic acid component and a diol component, and the dicarboxylic acid component is a first compound represented by the following formula (1): 2) a second compound represented by the formula, and when the total dicarboxylic acid component is 1, the content ratio of the first compound is 0.1 or more and 0.4 or less in molar ratio, and the content of the second compound is A prepolymer having a molar ratio of 0.1 or more and 0.75 or less,

[0023]

[Chemical 1] (In the formula, R1 and R2 are COOH or CH ₂ COOH
Represents )

[0024]

[Chemical 2] (In the formula, R1 and R2 are COOH or CH ₂ COOH.
And R3 and R4 represent H or CH ₃ . ) A photosensitive resin containing a reactive monomer and a photopolymerization initiator can be mentioned.

A method of producing a precision sieve using photolithography in the present invention will be described with reference to FIG. First, a conductive substrate 7 such as an aluminum plate or a stainless plate is prepared, and its surface is subjected to zinc displacement plating.
A negative photosensitive resin layer 11 having a thickness of 10 to 500 μm is formed thereon by applying the above-mentioned special photosensitive resin. Next, the photosensitive resin layer 11 is patterned by photolithography. That is, first, a photomask M having a light transmitting portion corresponding to the shape of the sieving holes and the arrangement in the surface of the sieving plate is prepared. The photomask M is arranged above the negative photosensitive resin layer 11, and high energy light is irradiated from above the photomask M. This state is shown in FIG. Next, a predetermined development process is performed to remove a portion of the photosensitive resin layer 11 which is not exposed to light.

Examples of the light source of high energy light include an ultra-high pressure mercury lamp, a low pressure mercury lamp, a halogen lamp and a xenon lamp. In order to form a fine pattern having a pore size of 20 μm or less, it is preferable to irradiate parallel rays. As a result, the columnar body 12 made of a cured product of the photosensitive resin is formed on the conductive substrate 7 in a shape and arrangement corresponding to the sieve holes. FIG. 1B shows this state. Next, the metal layer 13 is grown on the conductive substrate 7 by electrolytic plating. FIG. 1C shows this state. This metal layer 13 becomes a precision sieving plate. Here, the thickness of the metal layer 13 is set to be equal to or less than the height of the columnar body 12. When the metal layer 13 is formed to a position higher than the height of the columnar body 12 and the upper surfaces of the adjacent columnar bodies 12 are connected by the metal layer 13, the metal layer on the upper surface of the columnar body 12 is removed.

Electrolytic plating includes copper sulfate plating, copper pyrophosphate plating, nickel plating, chrome plating, palladium,
Any plating such as precious metal plating such as gold may be used. In order to obtain the mechanical strength required for the precision sieving plate, it is preferable to perform nickel plating, chrome plating, and copper plating. Alternatively, a film made of a composite material may be formed on the conductive substrate by incorporating insulating fine particles such as Teflon (registered trademark), silica, or alumina into a metal and performing electroplating. In this case, a precision sieving plate made of a composite material is obtained.

Next, the columnar body 12 is removed by a wet etching method or by physically peeling.
FIG. 1D shows this state. Next, the conductive substrate 7 is
It is removed by a wet etching method or by physically peeling. Thereby, the metal precision sieving plate 1 in which the sieving holes 10 are formed in a predetermined arrangement is obtained. FIG. 1 (e) shows this state. Further, in the case of forming fine holes, metal or ceramics can be deposited on the entire surface of the sieving plate including the inside of the holes formed as described above to form holes having a smaller hole diameter. Figure 1
(F) shows this state. As the method used at this time, electroless plating method, electrolytic plating method, sputter deposition method,
Vacuum deposition method, plasma CVD method, laser ablation method, ion plating method, plasma oxidation / nitridation method,
MOCVD method can be mentioned. Also, when ceramics are deposited, the surface of the sieve plate becomes an insulator,
Since the classification efficiency may decrease due to the influence of static electricity when the particles are put into a classification operation, the surface of the ceramic may be coated with a metal.

[Precision Sieve Plate Unit] In the present invention, even if spherical particles are mixed with rod-shaped particles, only spherical particles can be separated by passing them through a sieving hole. Usually, it is difficult to separate rod-shaped particles with one sieving plate. Therefore, as a result of intensive studies, the inventor of the present invention uses a fine sieving plate unit in which two sieves having holes having the same hole diameter and arrangement pitch are accurately aligned and arranged in parallel by making full use of a fine processing technique. Thus, the present invention has been completed based on the idea that it is possible to produce a sieve that does not allow rod-shaped particles to pass through.

FIG. 2 is a conceptual view of a precision sieving plate having a circular hole shape. In the precision sieving plate unit of the present invention, when the holes of two sieving plates are projected on the same plane, the overlapping area of the holes needs to be 90% or less of the area of the holes. If they are overlapped with each other by more than 90%, rod-shaped particles may pass therethrough, which is not preferable. Further, the distance between the two sieving plates is 1.1 to 2.5 times the shortest hole length. When the ratio is less than 1.1 times, the first sieve plate and the second sieve plate are arranged at positions displaced from each other, so that the spherical particles passing through the first sieve move in the space between the two sieve plates. No, it cannot pass through the second sieve. If the size is larger than 2.5 times, the possibility that rod-shaped particles will pass through increases.

Between the two precision sieving plates, it is necessary to insert spacers with a predetermined spacing at predetermined positions. The spacer must not block the holes in the precision sieve plate. As a method for inserting the spacer, a method using photolithography and a plating method is preferable. That is, the first method is to form a hole of a photosensitive resin in a place other than the hole of the second precision sieving plate, form a metal spacer in the hole using a plating method, and then form the first precision sieve. This is a method of aligning and joining the sieve plate. In this method, since it is necessary to perform accurate alignment, the respective precision sieving plates are attached onto the base material and, as shown in FIG. 3, they are brought close to each other while confirming both patterns using a CCD camera.
An adhesive or solder plating is placed on the surface of the spacer, and it can be bonded to the other precision sieving plate by heating. The second method is to form a metal spacer on the second precision sieving plate and then successively form the first precision sieving plate on it. At this time, since it is necessary to perform photolithography while aligning the patterns, an exposure device that can accurately align the substrate and the exposure mask is required.
Further, in the second method, since it is necessary to remove the photo-cured photosensitive resin between the two precision sieving plates, the temperature at which the material forming the sieve does not deteriorate (in the case of nickel,
The hardness may be significantly reduced by heating.
It is necessary to perform heat treatment at a temperature not exceeding 0 ° C. Alternatively, when a positive-type photosensitive resin is used in photolithography, it dissolves in a solvent, and therefore heat treatment is not particularly necessary and can be removed by dissolving the photosensitive resin in the solvent.

[Regarding Classifier] When fine particles having a particle diameter of 10 μm or less are classified by a sieve, it is difficult to perform the classification simply by moving the sieve. Also, as a method for classifying large particles having a particle diameter of generally more than 10 μm, an ultrasonic vibrator is attached to a sieve to directly transmit ultrasonic waves to a sieving plate, but the sieving plate has a thickness of 50 μm or less. When made of thin material, ultrasonic vibrations can damage the sieve plate. Further, Japanese Patent Laid-Open Publication No. 2001-252588 describes a method of inserting a liquid in which particles to be classified are dispersed into one space of a sieve, and further inserting a rod-shaped tip for transmitting ultrasonic vibration into the liquid. Also, since the sieve plate needs to support the weight of the liquid, it is necessary to install a jig for supporting the sieve plate under the sieve plate, which causes a problem that the opening area is reduced. .

According to the method for producing metal fine particles of the present invention, the precision sieving plate according to claim 4 or the precision sieving unit according to claim 5 is attached to the bottom of the cylindrical charging part for charging the powder for sieving. (Fig. 4), place the precision sieve in a container for receiving powder that has passed through the precision sieve so that the precision sieve plate or the precision sieve unit is on the bottom (Fig. 5), and then put the liquid substance in the container. The container is characterized in that ultrasonic vibration is applied to the container in the inserted state (FIG. 5). By this method, the load on the precision sieving plate can be greatly reduced, and the life of the precision sieving plate can be greatly extended. As the liquid substance used here, it is necessary to select a liquid in which the particles to be classified do not deteriorate or dissolve. For example, alcohols, water, ketones, ethers, esters, etc. can be mentioned.

Since the sieve plate is put in a container for receiving particles that have passed through the precision sieve and the sieve plate is present in the liquid, the load on the precision sieve plate can be reduced, and ultrasonic vibration can be applied to each container for receiving the passed particles. Since it can be placed in an apparatus, for example, an ultrasonic cleaner (FIG. 5), the apparatus configuration is extremely simple.

[About Porous Metal Molded Article] The porous metal molded article formed by using the metal fine particles of the present invention is formed through a step of filling the metal fine particles in a mold and heating and compression, or a step of heating. To be done. In particular, when producing a porous metal molded body containing a large number of voids between particles and having a density significantly smaller than the density of the metal constituting the metal fine particles used,
It is preferable that the particles can be bonded only by the heating step without the heating and compression step.

Therefore, copper, gold, silver, platinum, nickel,
Palladium, indium, iron, chromium, tantalum, tin,
An element selected from lead, zinc, cobalt, titanium, tungsten, bismuth, silicon, antimony, aluminum, magnesium, and rare earth elements, or a metal particle in which the surface of an alloy particle is thinly coated with a metal. It is preferable that the vicinity of the surface is melted and the particles are joined together. At this time, it is necessary to maintain the fine particle shape without melting the individual particles by heating.

The present invention will be described in detail below with reference to examples. The present invention is not limited to the examples.

[Example 1] [Production of precision sieving plate] A precision sieving plate was produced by the method of the first embodiment. An aluminum plate having a thickness of 100 μm is prepared as the conductive substrate 7, the surface thereof is treated by zinc displacement plating, copper is further deposited to 5 μm in a copper pyrophosphate plating bath, and then the deposited copper surface is subjected to EBARADEN. A substrate having a diffuse reflectance of less than 1% was obtained by performing an oxidation treatment with an electrobright solution manufactured by Sangyo Co., Ltd. The photosensitive resin layer 11 was formed by applying the following liquid photosensitive resin.

The photosensitive resin used had a number average molecular weight of 2
Unsaturated polyester prepolymer which is 000: 100
In parts by weight, tetraethylene glycol dimethacrylate: 10.7 parts by weight, diethylene glycol dimethacrylate: 4.3 parts by weight, pentaerythritol trimethacrylate: 15 parts by weight, phosphoric acid (monomethacryloyloxyethyl): 3.6 parts by weight, 2,2-dimethoxy-
2-phenylacetophenone: 2 parts by weight, 2,6-di-
tert-Butyl-4-methylphenol: 0.04 parts by weight, and "OPLAS Yellow 1" manufactured by Orient Chemical Co., Ltd.
40 ": 0.11 parts by weight was added, and the mixture was obtained by stirring and mixing.

The unsaturated polyester prepolymer having a number average molecular weight of 2000 is adipic acid: 0.15, itaconic acid: 0.25, fumaric acid: 0.6, and a molar ratio of diethylene glycol: 1.0. Obtained by dehydration polycondensation reaction. Here, itaconic acid has one of R1 and R2 in the formula (1) is “COOH” and the other is “CH ₂ C”.
OOH "corresponding to the first compound. Further, fumaric acid has the formula (2) in which R1 and R2 are "COOH" and R is
Corresponds to the second compound in which 3 and R4 are "H".
The number average molecular weight was measured using a gel permeation chromatography device manufactured by Shimadzu Corporation and calibrated with a polystyrene standard product.

The shape and arrangement of the sieving holes of the precision sieving plate produced in this example are shown in FIG. FIG. 6A shows
It is a perspective view which shows one sieving hole of this precision sieving board, and its circumference, and Drawing 6 (b) is a partial top view showing this precision sieving board. In this embodiment, as shown in FIG. 6B, circular sieving holes 10 having a diameter of X μm are arranged on the lattice at a pitch (2 × μm) that is twice the diameter of the holes, and the center of the lattice also has a circular shape having a diameter of X μm. As the precision sieving plate 1 in which holes were arranged, a plate A having a plate thickness D of 18 μm, a sieve A having a circular diameter X of 5 μm and a sieve B having a diameter of 7 μm were prepared. In the sieve A, particles having a diameter of 5 μm or less pass through the sieving holes 10, and particles having a diameter of more than 5 μm remain on the sieving plate 1 without passing through the sieving holes 10.

The thickness of the photosensitive resin layer 11 was 20 μm. In addition, as the photomask M of FIG.
A circle having the arrangement shown in (b) was used as a light transmitting portion. As the high-energy light emitted from above the photomask M, light from an ultra-high pressure mercury lamp was processed by a fly-eye lens and several reflecting mirrors into parallel light. In addition, the metal layer 1 is formed by electrolytic nickel plating.
Before forming No. 3, reactive ion etching using oxygen plasma was performed as a pretreatment for plating. The back surface of the aluminum substrate 7 was covered with an adhesive film. Using a nickel plating bath containing a slight amount of boron, the metal layer 13 made of a nickel plating film was grown to a thickness of 18 μm.

The deposited nickel surface was protected by coating an adhesive film, the aluminum plate was removed by wet etching with 10% by volume of hydrochloric acid, and further copper was removed using concentrated nitric acid. Further, the film protecting the surface of nickel was peeled off, and the columnar body 12 made of a cured product of the photosensitive resin remaining in the holes was removed by a reactive ion etching method in an oxygen atmosphere. Next, another precision sieving plate having a diameter of 5 μm prepared by the same method is prepared, and the precision sieving plate is immersed in an electroless nickel plating bath to form a nickel layer having a thickness of 0.5 μm. A precision sieving plate C having the same round sieving holes as that of the precision sieving plate A was obtained. The electroless nickel plating bath is Enipack L manufactured by EBARA Eugelite
The bath was built using the V process.

As described above, the precision sieving plate 1 made of nickel, which has a circular sieving hole having a thickness of 20 μm and a diameter of 4 μm in the same arrangement as that of the sieve A, is used.
A precision sieving plate A having a circular sieving hole 10 having a thickness of 18 μm and a diameter of 5 μm in the arrangement shown in FIG.
A precision sieving plate B having a circular sieving hole 10 having a diameter of 7 μm and a diameter of 7 μm in the arrangement shown in FIG. 6B was produced. These precision sieving plates 1 had sufficient mechanical strength to be used as sieving plates. The aperture ratios of the precision sieving plates A, B and C were 39%, 39% and 25%, respectively. The aspect ratios of the sieve holes are 3.6 and 2.
It was 6 and 4.8.

[Preparation of metal fine particles] The alloy fine particles used for classification were prepared by the atomization method. 70 parts by weight of copper and 30 parts by weight of silver were put into a graphite crucible, heated to 1700 ° C. by a high frequency induction heating device, and melted in a helium gas atmosphere of 99% by volume or more. Next, after introducing the molten metal into the spray tank of the helium gas atmosphere from the tip of the crucible, the helium gas (purity 99 volume% or more, oxygen concentration 0.1 volume%,
Atomization was performed by injecting a pressure of 2.5 MPa) to obtain alloy fine particles. The purity of the metal raw materials used was 99% by weight or more for all the metals. The alloy fine particles obtained by the atomization method were classified three times using an airflow classifier (manufactured by Nisshin Engineering Co., Ltd., Turbo Classifier TC15) to gradually narrow the particle size distribution. The particle size was widely distributed from 0.1 μm to 15 μm.
When the obtained alloy fine particles were observed with a scanning electron microscope (S-2700, manufactured by Hitachi, Ltd.), about 98% of the particles were spherical. About 2% of the particles were rod-shaped particles.

[Evaluation of Classification Performance] Using the precision sieving plate 1 produced in this Example 1, a precision sieve shown in FIG. 4 was produced. This sieving comprises a feeding part 61 for putting powder for sieving and a sieving part 62 equipped with the precision sieving plate 1.
And a receiving portion 63 for receiving the powder that has passed through the sieve. Ethanol was put into this precision sieve up to the position where the precision sieve plate was attached, and further put in an ultrasonic cleaner. A portion in which the powder is dispersed in ethanol is put into the charging section 61.
Then, vibration was applied at a frequency of 42 kHz with an ultrasonic cleaner. The output of the ultrasonic cleaner was 120W.

First, the silver-copper alloy fine particles produced by the atomizing method using a precision sieve having the precision sieve plate B (hole diameter 7 μm) as the precision sieve plate 1. Next, the ethanol in which the powder contained in the container 63a was dispersed by this classification was classified as a precision sieving plate 1 using a precision sieving plate having the above-mentioned precision sieving plate A (pore diameter 5 μm). When the particle size of the powder remaining on the precision sieving plate 1 was measured by this classification, the average particle size was 5.3 μm and the standard deviation of the particle size distribution was 0.5 μm.

Further, the ethanol in which the powder contained in the container portion 63 was dispersed by this classification was classified as a precision sieving plate 1 using a precision sieving plate having the above-mentioned precision sieving plate C (pore diameter 4 μm). When the particle size of the powder remaining on the precision sieving plate 1 in this classification was measured, the average particle size was 4.3 μm and the standard deviation of the particle size distribution was 0.4 μm. Very interestingly, as a result of observing the metal fine particles remaining on the precision sieve having a diameter of 5 μm with a scanning electron microscope, no state in which a plurality of particles were aggregated was observed at all.

[0048]

[Example 2] [Production of precision sieving plate] First, a precision sieving plate 1A having a circular hole diameter of 7 µm was produced in the same manner as in Example 1. However, as shown in FIG. 7A, the holes are arranged at the positions of the lattice points, and the arrangement pitch of the adjacent lattice points is 12 μm. Next, the precision sieving plate 1B having the same hole diameter and the same hole arrangement as the precision sieving plate 1A is manufactured by the same method as in Example 1 up to the intermediate step, that is, the patterning of the photosensitive resin on the conductive substrate and the subsequent electrolytic nickel plating step. Up to the same method.

As shown in FIG. 7B, the same photosensitive resin having a thickness of 20 μm was formed again on the formed nickel pattern without removing the photo-cured resin pattern.
Furthermore, the nickel pattern and the mask pattern were aligned and exposed by using an aligner capable of aligning, and a pattern in which circular holes of the photosensitive resin were formed on the nickel layer was obtained through the developing process (FIG. 7 ( c)). In this step, the diameter of the holes was 7 μm, and the array pitch was 12 μm. The mask was aligned so that the formed circular holes of the photosensitive resin were located at the center of the grid in which the holes formed in the nickel layer were arranged.

Subsequently, nickel was deposited to a height of 10 μm by using the electrolytic nickel plating method. Following electrolytic nickel plating, electrolytic solder plating was performed to form a solder layer having a height of 5 μm (FIG. 7 (d)). Next, the photocured photosensitive resin was removed by reactive ion etching in an oxygen atmosphere. Further, the aluminum layer used as the conductive substrate was removed by etching using a 10% by volume hydrochloric acid aqueous solution, and the exposed copper substrate was removed by etching using concentrated nitric acid.

The precision sieving plate 1B in which a laminated convex pattern made of nickel and solder is formed on the surface of the nickel precision sieving formed as described above, and the nickel precision sieving plate 1A already prepared are shown in FIG. As shown in the sectional view of (a), make sure that the holes in both sieve plates do not overlap CC
Accurate alignment was performed using a D camera, and partial temporary fixing was performed using a solder paste having a melting point higher than that of the formed solder plating. Finally, the temperature was brought to a temperature at which the solder plating melted, and both precision sieves were bonded.

The distance between the precision sieving plates 1A and 1B is 12 μm.
Met. Further, when the sieve holes of the two precision sieve plates were projected on the same plane, the overlap of the holes was 10% or less in area.

[Evaluation of classification performance] As shown in FIG. 8, each precision sieving plate 1A, 1B connected by soldering.
A cylindrical body 67 having a different diameter was attached to the sheet using an adhesive to form a precision sieve. The precision sieve was then placed in a container that received the powder that passed through the sieve, and ethanol was poured into the container until the precision sieve plate was immersed. Then, as in Example 1, the container was inserted into an ultrasonic cleaner,
Particles were classified by applying ultrasonic vibration.
The particles before the classification operation were particles having an average particle size of 7.1 μm and a standard deviation of particle size distribution of 0.6 μm, and contained rod-shaped particles. Scanning electron microscope (S
As a result of observation with EM), the existence probability of rod-shaped particles is about 2%.
Met. When the particles that passed through the precision sieve were observed using SEM, no rod-shaped particles were present.

[0054]

[Example 3] In a precision sieving plate having a structure in which two precision sieving plates are stacked, the overlapping of the holes when the sieving holes are projected on the same plane is 60% in area, which is surprising.
A precision sieving plate was produced by the same method. Furthermore, as a result of classifying the same metal fine particles as in Example 2, it was confirmed that the rod-shaped metal fine particles could not pass through the sieving holes of the precision sieving plate and remained on the precision sieving plate.

[0055]

[Fourth Embodiment] [Preparation of precision sieving plate] As shown in FIG. 9, the precision sieving plate has holes arranged at the lattice points having a regular hexagon as a unit cell and at the center thereof, and the hole diameter X of the sieving hole is 5.
μm and 7 μm, length of one side of regular hexagon (X + 4μ
Precision sieving plates A and B were produced in the same manner as in Example 1 except that m) was two types of precision sieving plates having a diameter of 9 μm and 11 μm, and the thickness of the precision sieving plate was 20 μm. Precision sieve plate A with hole diameter X of 5 μm and X of 7 μm
m corresponds to the precision sieve plate B. The opening ratio of the precision sieving plate A was 25%, and the opening ratio of the precision sieving plate B was 40%. In addition, the aspect ratio of the sieving hole is the precision sieving plate A
4 and the precision sieve plate B was 2.9.

[Evaluation of classification performance] A precision sieve was assembled in the same manner as in Example 1, and classification was performed using a precision sieve and a classifier in which the same metal fine particles as in Example 1 were assembled.
The particles were classified using the precision sieving plates A and B, and the particle size of the metal fine particles remaining on the precision sieving plate A was measured.
The average particle size is 5.4 μm, and the standard deviation of the particle size distribution is 0.
It was 5 μm.

[0057]

[Comparative Example 1] The same powder classification as in Example 1 was performed using an airflow classifier "Turbo Classifier TC15" manufactured by Nisshin Engineering Co., Ltd. The target average particle size during classification was set to 6 μm. As a result, the average particle size of the powder after classification was 5.7 μm, which was close to the set value of 6 μm, but the particle size was widely distributed from 1 μm to 15 μm, and the standard deviation of the particle size distribution was 3 μm. .

[0058]

[Comparative Example 2] The shape of the sieve hole is circular, and the diameter is 5μ.
m, the diameter is 7μ if the hole pitch is 25μm.
m, and two kinds of sieves having a sieve hole arrangement of 35 μm were prepared. The opening ratio of these sieves was 6%. These sieves are produced by patterning a nickel sheet by an etching method, and the cross-sectional shape of the holes is trapezoidal due to the undercut phenomenon in which even the lower part of the resist pattern is etched. Therefore, in the cross-sectional shape of the hole, the portion where the size of the hole was 5 μm was less than 1 μm in the thickness direction of the sieve. The fine metal particles used for classification are the same as the fine metal particles used in Example 1.

As in Example 1, the classification device was assembled,
The classification operation was carried out in the same manner. As a result, ultrasonic vibration was applied for the same time as in Example 1, but the weight of the particles that passed through the sieve was less than 1/5. In addition, as a result of observing the fine metal particles remaining on the sieve having a diameter of 5 μm with a scanning electron microscope, the average particle diameter was 5.6 μm, the standard deviation of the particle diameter distribution was 1.5 μm, and a plurality of particles were aggregated. Was found in more than half of the particles.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a process for producing a precision sieving plate of the present invention.

FIG. 2 is a cross-sectional view (a) of a double-layered precision sieving plate of the present invention and a perspective view showing components.

[Fig. 3] Fig. 3 is a diagram for explaining a situation of alignment when a precision sieving plate having a double structure of the present invention is manufactured.

FIG. 4 is a view showing components of the precision sieve of the present invention.

FIG. 5 is a diagram showing a precision sieving apparatus of the present invention.

FIG. 6 is a perspective view (a) and a plan view (b) of the precision sieving plate of the present invention.

FIG. 7 is a diagram illustrating a process for producing a double-structured precision sieve plate of the present invention.

FIG. 8 is a cross-sectional view of a double-structured precision sieve of the present invention.

FIG. 9 is a view for explaining the arrangement of sieving holes of the precision sieving plate of the present invention.

FIG. 10 is a diagram illustrating the shape and arrangement of sieving holes of the precision sieving plate of the present invention.

[Explanation of symbols]

1 Precision Sieve Plate 1A First Precision Sieve Plate 1B Second Precision Sieve Plate 7 Conductive Substrate 8 Photosensitive Resin Layer 8a Through Hole 10 Sieve Hole (Through Hole) 11 Photosensitive Resin Layer 12 From Cured Material of Photosensitive Resin Columnar body 13 Metal layer 16 Metal or ceramics layer 19 Metallic columnar body 61 Input part 61a Cylindrical part 62 Sieve part 63 Receiving part 64 Ultrasonic cleaner water tank 65 Ultrasonic transducer 66 Liquid substance 67 Cylindrical body 68 Feet 69 hole Unit cell 70 showing the closest packing arrangement of the regular hexagonal sieve unit grid showing the closest packing arrangement of hexagonal sieve holes M photomask M1 photomask h height of metal columnar body D precision sieve plate thickness H second precision Sieve plate thickness W Deviation between the positions of the holes in the first precision sieving plate and the holes in the second precision sieving plate W2 Length of one side of the regular hexagonal sieving hole

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01B 1/22 H01B 1/22 D 13/00 501 13/00 501Z F term (reference) 4D071 AA05 AB45 AB63 DA20 4K017 AA02 BA01 BA02 BA03 BA04 BA05 BA06 BA08 CA07 DA01 EA13 EB00 4K018 BA01 BA02 BA04 BA05 BA08 BA09 BA10 BA13 BC22 BD04 5G301 AA01 AA02 AA03 AA07 AA08 AA09 AA12 AA14 AA15 AA16 AA17 AA19 AA20 AA21 AA22 AA23 AA30 AB20 AD06 AD10 AE10

Claims (6)

[Claims] 1. Metal fine particles having an average particle size of 1 μm to 10 μm and a standard deviation of the particle size distribution of 25% or less of the average particle size. 2. An abundance ratio of irregularly-shaped particles (particles having a ratio of the length in the longitudinal direction to the length in the lateral direction of 2 or more) in the metal fine particles is 1% or less. The metal fine particles described. 3. The fine metal particles according to claim 1 or 2 are copper, gold, silver, platinum, nickel, palladium, indium, iron, chromium, tantalum, tin, lead, zinc, cobalt, titanium, tungsten, bismuth. , Fine particles having a metal coating on the surface thereof, or an alloy of any one of these metals, silicon, antimony, aluminum, magnesium, and rare earth elements. 4. A method for producing fine metal particles having a narrow particle size distribution by classifying fine metal particles with a precision sieving plate, wherein the fine metal particles are produced by an atomization method and used for classification. Precision sieve plate has a thickness of 1
0 μm or more and 100 μm or less, the sieving holes are formed in a predetermined arrangement so that the opening ratio is 20% or more and 80% or less, and the sieving holes have a circular or polygonal planar shape. When the planar shape of the hole is circular, the diameter is 1 to 10 μm, and the standard deviation of the hole diameter distribution is 25% or less of the average value of the hole diameter, and further defined by the ratio of the hole depth to the hole diameter. When the aspect ratio of the hole is 1.5 or more and the planar shape of the sieve hole is polygonal, the shortest side is 1 to 10 μm, and the standard deviation of the distribution of the shortest side is 25% or less of the average value of the shortest side. And the ratio of the depth of the hole to the length of the shortest side on the projection surface of the hole is 1.5 or more. 5. A method for producing fine metal particles having a narrow particle size distribution by classifying fine metal particles by a precision sieving unit consisting of two precision sieving plates, wherein the fine metal particles are produced by an atomizing method. The precision sieving unit comprises two precision sieving plates arranged parallel to each other at a constant interval according to claim 4, wherein the holes have the same arrangement pitch of holes.
The two precision sieving plates are arranged so that the overlapping area of the holes becomes 90% or less when the holes of the two precision sieving plates are projected on the same plane. The distance between the two precision sieving plates is the shortest length of the hole. The method for producing fine metal particles is characterized in that the precision sieving unit is 1.1 times to 2.5 times as large as the above. 6. Assembling a precision sieving plate according to claim 4 or a precision sieving in which the precision sieving unit according to claim 5 is attached to the bottom of a cylindrical feeding part for feeding powder for sieving. Characterized by placing a sieve plate or precision sieving unit in a container for receiving powder that has passed through the precision sieving so that it is on the bottom surface, and further applying ultrasonic vibration to the container with the liquid substance in the container Method for producing fine metal particles.