WO1993002221A2 - Manufacturing method of low melt metal fine particles - Google Patents

Manufacturing method of low melt metal fine particles Download PDF

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Publication number
WO1993002221A2
WO1993002221A2 PCT/US1992/005767 US9205767W WO9302221A2 WO 1993002221 A2 WO1993002221 A2 WO 1993002221A2 US 9205767 W US9205767 W US 9205767W WO 9302221 A2 WO9302221 A2 WO 9302221A2
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Prior art keywords
low melting
metal
organic solvent
melting metal
inactive organic
Prior art date
Application number
PCT/US1992/005767
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French (fr)
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WO1993002221A3 (en
Inventor
Shinji Sugii
Hitoshi Ono
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Minnesota Mining And Manufacturing Company
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Publication date
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Publication of WO1993002221A2 publication Critical patent/WO1993002221A2/en
Publication of WO1993002221A3 publication Critical patent/WO1993002221A3/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
    • H01B1/20—Conductive material dispersed in non-conductive organic material
    • H01B1/22—Conductive material dispersed in non-conductive organic material the conductive material comprising metals or alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/003—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic followed by coating of the granules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J2/00—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic
    • B01J2/02—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops
    • B01J2/06—Processes or devices for granulating materials, e.g. fertilisers in general; Rendering particulate materials free flowing in general, e.g. making them hydrophobic by dividing the liquid material into drops, e.g. by spraying, and solidifying the drops in a liquid medium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material

Definitions

  • This invention relates to a method for the production of a fine powder of a low melting metal and a method for the production of a composition containing the fine powder.
  • 4,582,872 propose a metal powder-containing organic polymer mixture produced by jointly melting a polymer and a metal possessing a melting point between the softening point and the melting point of the polymer.
  • the composition of the metal powder-containing polymer produced by this method exhibits improved impact resistance and thermoconductivity sufficient to be used as an electromagnetic shield because the metal powder-containing polymer is capable of containing metal particles the surface of which avoids contact with the air or oxygen and consequently remains clean.
  • SUBSTITUTE SHEET dispersing the metal powder in the form of ribbons in the polymer at a low rotational speed of 20 r.p.m. at a relatively low temperature in the range of from 100°C to 150°C.
  • Such a dispers . ion imparts continuity to the metal powder in the metal powder-containing polymer, forming flawless metal fibers in the product, and confers mechanical strength upon the product so that the metal powder-containing powder may be rendered usable in applications requiring mechanical strength of a grade sufficient for bearings other than those used in electroconductive materials. Owing to the reinforcing effect of the metal fibers, the product of this invention possesses ample mechanical strength.
  • a method is provided to produce a fine powder of low melting metal in which, an inactive organic solvent, particularly a fluorine type inactive organic solvent, is used as a medium for the fine division of the metal.
  • This solvent contains no dissolved oxygen.
  • the metal during the dispersion in a finely divided form, is not directly exposed to the ambient air.
  • the fine metal powder consequently produced, therefore, has no or a negligible oxide film layer and excels in electroconductivity and durability.
  • the fine metal powder is introduced into the polymer in a form coated with an inactive organic solvent incapable of dissolving other organic compounds.
  • Fig. 1 is a scanning electron micrograph of minute particles of a low melting metal produced in Example 1 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
  • Fig. 2 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 1 in accordance with the present invention.
  • Fig. 3 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
  • Fig. 4. is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 5 in accordance with this invention.
  • Fig. 5 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
  • Fig. 6 is a diagram showing particle size distribution of minute particles of a low melting metal produced in Example 6 in accordance with this invention.
  • Fig. 7 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
  • Fig. 8 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 7.
  • Fig. 9 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 8 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
  • Fig. 10 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 8.
  • Fig. 11 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 9 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
  • Fig. 12 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 9.
  • Fig. 13 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 10 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
  • Fig. 14 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 10.
  • Fig. 15 is a scanning electron micrograph of a fine powder of a low melting metal produced in
  • Example 10 in accordance with the present invention i.e. a photograph illustrating the structure of particles in place of a drawing.
  • This invention provides a method for the production of a fine metal powder having the surface thereof not or sparingly exposed to oxygen in the air and thereby oxidizing and possessing outstanding electroconductivity and durability and a method for the production of a composition containing the fine metal powder.
  • the method for the production of a fine powder of a low melting metal comprises (1) introducing a low melting metal having a melting point in the range of from 47°C to 321°C into an inactive organic solvent having a decomposition point or a boiling point higher than the melting point of the lower melting metal, (2) constantly heating the mixture at a temperature higher than the melting point of the lower melting metal and lower than the boiling point of the inactive organic solvent, and (3) dispersing and mixing the low melting metal in the form of a fine powder by shear stirring in the inactive organic solvent.
  • a method for the production of a composition containing a fine powder of a low boiling metal comprises (1) preparing a fine powder of a low melting metal produced by the method described above in a form having the surface thereof coated with an inactive organic solvent, (2) introducing the fine powder into a polymer or a polymer precursor having a softening point or a melting point lower than the melting point of the low melting metal and kept molten at a temperature lower than the melting point of the low melting metal, and (3) stirring the polymer or polymer precursor thereby dispersing and mixing the fine powder of the low melting metal in the polymer or polymer precursor.
  • the low melting metal having a melting point in the range of from 47°C to 321 ⁇ C and used in this invention may be a simple metal or an alloy. Varying species of solder (having melting points of 70°C, 117 ⁇ C, 143 ⁇ C, 182 ⁇ C, and 220 ⁇ C) may be mentioned as examples.
  • inactive organic solvent refers to an organic solvent that is nonreactive with a solder metal.
  • the inactive organic solvents having decomposition points or boiling points higher than the melting point of the low melting metal include fluorine type organic solvents (such as Fluorinert series, FC-43 (boiling point of 174 ⁇ C) , FC-70 (boiling point of 215°C) , and FC-71 (boiling point of 253°C), Minnesota Mining Manufacturing Company commercially available from) , toluene, xylene, die thylfor amide (DMF) , dimethylsulfoxide (DMSO) , 1,1,2-trichloroethane, tetrachloroethane, and silicon type organic solvents, and the like.
  • fluorine type organic solvents such as Fluorinert series, FC-43 (boiling point of 174 ⁇ C) , FC-70 (boiling point of 215°C) , and FC-71 (
  • fluorine type inactive organic solvent refers to a liquid completely fluorinated organic compound produced by substituting fluorine atoms for all the hydrogen atoms of an ordinary organic compound.
  • the polymer or the polymer precursor having a softening point or a melting point lower than the melting point of the low melting metal may be a thermoplastic polymer, a thermosetting polymer in an uncured state, or an elastomer.
  • an epoxy resin, a bis-phenol A-epichlorohydrin condensation product, a polyamide resin, and a polyimide resin may be used, in view of adhesive power, ther oresistance, electrical properties and the like.
  • a filler may be optionally added before, during, or after the process of mixing the metal powder with the polymer or polymer precursor.
  • the fillers which are usable effectively herein include anhydrous silica, clay, calcium carbonate, various mineral powders, carbon black and the like.
  • the filler used in this invention may be suitably selected in due consideration of the characteristic properties that the finished product is desired to possess or the economy of the product.
  • the content of the low melting metal is in the range of from 2 to 95% by weight, and preferably 2 to 75% by weight, based on the total weight of the metal and the inactive organic solvent.
  • the content of the metal is in the range of from 2 to 95% by weight, preferably from 5 to 65% by weight, based on the total weight of the metal and the polymer or polymer precursor.
  • a scanning electron micrograph of fine metal powder obtained by removing Fluorinert FC-70 from the dispersion of a fine powder of a low melting metal produced in Example 1 is shown together with a ratio of magnification in Fig. 1.
  • the state of particle size distribution is shown in Fig. 2. It is noted from Fig. 2 that minute particles measuring 10 to 45 ⁇ m, particularly 15 to 35 ⁇ m, in diameter were formed in a closely dispersed state in the fluorine type inactive organic solvent.
  • Fine powders of a low melting metal were prepared by following the procedure of Examples 1 to 4, except toluene and other solvents were used as inactive organic solvents. The results are shown in Table 2. The speed of stirring was invariably 11,000 r.p. . TABLE 2
  • a fine powder of a low melting metal was prepared by following the procedure of Examples 1 to 4. The results are shown in Table 3.
  • the particles of the fine powder produced had diameters in the range of from 10 to 20 ⁇ OL.
  • the speed of stirring was 11,000 r.p.m.
  • FIG. 15 A scanning electron micrograph of metal particles from the product of Example 11 is shown in Fig. 15.
  • the dispersions of fine low melting metal powders prepared in Examples 1 to 11 were subjected to shear stirring at a speed of 11,000 r.p. . in epoxy type or polyamide type adhesive binders by the use of Autohomomixer Type M at temperatures lower than the melting points of the relevant alloys, to prepare compositions having fine low melting metal powders homogeneously dispersed in the polymers.
  • the percentage compositions and the stirring conditions are summarized in Table 4.
  • a blend A was prepared by mixing 20 g of the fine dispersion of Example 1, 43 g of EPON 828, 5 g of DICY, 1.9 g of anhydrous silica, 12 g of nitrile type modifier CTBN, and 16.8 g of EPON 1009. It was heated and stirred at about 120 ⁇ C for one hour to evaporate the Florinate (about 10 g contained) . The residue was cooled to below 50°C and then dissolved in 6.3 g of finely divided DICY and 80 g of methylethyl ketone as a solvent. The resultant 50 p thin solution was coated to a silicon-treated PET film, and dried to produce an anisotropic electroconductive film.
  • This anisotropic electroconductive film was used to join a copper circuit formed by patterning on a flexible substrate of CTCpit 0.6 mm under the conditions of 16 kgf/cm 2 of bonding pressure and 215 ⁇ C of bonding temperature for a period of two minutes, using "Bonder J-3" (Sumitomo 3M) .
  • the electroconductivity had a very small magnitude of less than 0.1 ⁇ .
  • Example 2 and 100 g of a polyamide type hotmelt JA-7375 were mixed by stirring. The stirring was continued at a temperature of 160°C, to effect incorporation of solder particles into the polyamide resin and, at the same time, vaporization of Florinate as a dispersant.
  • Example 1 One hundred (100) g of the fine dispersion of Example 1 was left standing for one day to effect sedimentation of solder particles. The supernatant Florinate was discarded and 10 g of the powdery flux resin was dispersed. The resultant creamy paste was heated to produce a creamy solder possessing electroconductivity.

Abstract

A method for the production of a fine powder of a metal having the surface thereof not oxidized or negligibly oxidized by contact with oxygen in the ambient air and excelling in electroconductivity and durability and a method for the production of a composition containing the said fine metal powder are proposed. The fine metal powder is produced by introducing a low melting metal possessing a melting point in the range of from 47 °C to 321 °C into an inactive organic solvent possessed of a decomposition point or a boiling point higher than the melting point of the low melting metal and constantly heated to a temperature higher than the melting point of the low melting metal and lower than the boiling point of the inactive organic solvent and subjecting the metal to shear stirring thereby dispersing and mixing the low melting metal in the form of minute particles in the inactive organic solvent.

Description

Manufacturing Method of Low Melt Metal Fine Particles
Technical Field This invention relates to a method for the production of a fine powder of a low melting metal and a method for the production of a composition containing the fine powder.
Background of Invention The fine metal powder heretofore used for the impartation of electroconductivity to an adhesive has been produced by the atomizing method and the mechanical pulverizing method.
In accordance with the conventional method for producing the fine metal powder, however, the produced fine metal powder fails to acquire outstanding electroconductivity and highly satisfactory durability because the surface of the fine metal powder succumbs to oxidation on contact with the oxygen in the ambient air. U.S. Patent No. 4,533,685 and U.S. Patent No.
4,582,872 propose a metal powder-containing organic polymer mixture produced by jointly melting a polymer and a metal possessing a melting point between the softening point and the melting point of the polymer. The composition of the metal powder-containing polymer produced by this method exhibits improved impact resistance and thermoconductivity sufficient to be used as an electromagnetic shield because the metal powder-containing polymer is capable of containing metal particles the surface of which avoids contact with the air or oxygen and consequently remains clean.
The invention of these U.S. patents contemplates
SUBSTITUTE SHEET dispersing the metal powder in the form of ribbons in the polymer at a low rotational speed of 20 r.p.m. at a relatively low temperature in the range of from 100°C to 150°C. Such a dispers.ion imparts continuity to the metal powder in the metal powder-containing polymer, forming flawless metal fibers in the product, and confers mechanical strength upon the product so that the metal powder-containing powder may be rendered usable in applications requiring mechanical strength of a grade sufficient for bearings other than those used in electroconductive materials. Owing to the reinforcing effect of the metal fibers, the product of this invention possesses ample mechanical strength. The electric resistance of the product, however, is such that a disc formed of this product in a diameter of 10 cm exhibits an electric resistance of only about 15 ohms. Thus, the composition is not satisfactory in terms of electroconductivity. Summary Briefly, in one aspect of the invention a method is provided to produce a fine powder of low melting metal in which, an inactive organic solvent, particularly a fluorine type inactive organic solvent, is used as a medium for the fine division of the metal. This solvent contains no dissolved oxygen. The metal, during the dispersion in a finely divided form, is not directly exposed to the ambient air. The fine metal powder consequently produced, therefore, has no or a negligible oxide film layer and excels in electroconductivity and durability.
In the method for the production of a composition containing the fine metal powder, the fine metal powder is introduced into the polymer in a form coated with an inactive organic solvent incapable of dissolving other organic compounds. The composition consequently obtained, therefore, contains a fine metal powder that is essentially not oxidized. BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a scanning electron micrograph of minute particles of a low melting metal produced in Example 1 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Fig. 2 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 1 in accordance with the present invention.
Fig. 3 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
5 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Fig. 4. is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 5 in accordance with this invention. Fig. 5 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
6 in accordance with the present invention; i.e. a photograph showing the structure of particles in place of a drawing. Fig. 6 is a diagram showing particle size distribution of minute particles of a low melting metal produced in Example 6 in accordance with this invention.
Fig. 7 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example
7 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Fig. 8 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 7.
Fig. 9 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 8 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing. Fig. 10 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 8.
Fig. 11 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 9 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Fig. 12 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 9.
Fig. 13 is a scanning electron micrograph of a fine powder of a low melting metal produced in Example 10 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Fig. 14 is a diagram showing particle size distribution of a fine powder of a low melting metal produced in Example 10.
Fig. 15 is a scanning electron micrograph of a fine powder of a low melting metal produced in
Example 10 in accordance with the present invention; i.e. a photograph illustrating the structure of particles in place of a drawing.
Detailed Description of Invention
This invention, provides a method for the production of a fine metal powder having the surface thereof not or sparingly exposed to oxygen in the air and thereby oxidizing and possessing outstanding electroconductivity and durability and a method for the production of a composition containing the fine metal powder. The method for the production of a fine powder of a low melting metal comprises (1) introducing a low melting metal having a melting point in the range of from 47°C to 321°C into an inactive organic solvent having a decomposition point or a boiling point higher than the melting point of the lower melting metal, (2) constantly heating the mixture at a temperature higher than the melting point of the lower melting metal and lower than the boiling point of the inactive organic solvent, and (3) dispersing and mixing the low melting metal in the form of a fine powder by shear stirring in the inactive organic solvent.
A method for the production of a composition containing a fine powder of a low boiling metal comprises (1) preparing a fine powder of a low melting metal produced by the method described above in a form having the surface thereof coated with an inactive organic solvent, (2) introducing the fine powder into a polymer or a polymer precursor having a softening point or a melting point lower than the melting point of the low melting metal and kept molten at a temperature lower than the melting point of the low melting metal, and (3) stirring the polymer or polymer precursor thereby dispersing and mixing the fine powder of the low melting metal in the polymer or polymer precursor. The low melting metal having a melting point in the range of from 47°C to 321βC and used in this invention may be a simple metal or an alloy. Varying species of solder (having melting points of 70°C, 117βC, 143βC, 182βC, and 220βC) may be mentioned as examples.
The term "inactive organic solvent" as used in the present invention refers to an organic solvent that is nonreactive with a solder metal. The inactive organic solvents having decomposition points or boiling points higher than the melting point of the low melting metal include fluorine type organic solvents (such as Fluorinert series, FC-43 (boiling point of 174βC) , FC-70 (boiling point of 215°C) , and FC-71 (boiling point of 253°C), Minnesota Mining Manufacturing Company commercially available from) , toluene, xylene, die thylfor amide (DMF) , dimethylsulfoxide (DMSO) , 1,1,2-trichloroethane, tetrachloroethane, and silicon type organic solvents, and the like.
The term "fluorine type inactive organic solvent" refers to a liquid completely fluorinated organic compound produced by substituting fluorine atoms for all the hydrogen atoms of an ordinary organic compound.
The polymer or the polymer precursor having a softening point or a melting point lower than the melting point of the low melting metal may be a thermoplastic polymer, a thermosetting polymer in an uncured state, or an elastomer. Where the produced composition is intended to be used as an electroconductive adhesive, an epoxy resin, a bis-phenol A-epichlorohydrin condensation product, a polyamide resin, and a polyimide resin may be used, in view of adhesive power, ther oresistance, electrical properties and the like. Not only the polymers enumerated above but also their precursors are usable in this invention. In this invention, a filler may be optionally added before, during, or after the process of mixing the metal powder with the polymer or polymer precursor. The fillers, which are usable effectively herein include anhydrous silica, clay, calcium carbonate, various mineral powders, carbon black and the like. The filler used in this invention may be suitably selected in due consideration of the characteristic properties that the finished product is desired to possess or the economy of the product. In the aspect of the invention relating to the method for the production of a fine powder of a low melting metal, the content of the low melting metal is in the range of from 2 to 95% by weight, and preferably 2 to 75% by weight, based on the total weight of the metal and the inactive organic solvent. In the aspect of the invention relating to the method for the production of a composition containing the fine powder, the content of the metal is in the range of from 2 to 95% by weight, preferably from 5 to 65% by weight, based on the total weight of the metal and the polymer or polymer precursor. Now, this invention will be described more specifically below with reference to working examples, which are not limitative of this invention.
Examples 1 to 4 Production of fine powder of low melting metal In a varying fluorine type inactive organic solvent indicated in Table 1, a varying alloy was subjected to high-speed shear stirring at a rate of 11,000 r.p.m. by the use of a mixing device (produced by Tokushu Kikakogyo K.K. and marketed under trademark designation of "Autohomomixer, Type M) at a temperature exceeding the melting point of the alloy, to produce a dispersion having a fine powder metal homogeneously dispersed and mixed in the fluorine type inactive organic solvent. In each of the compositions, the fluorine type inactive organic solvent and the alloy were used in an equal amount of 198 g. The components and the dispersing temperatures used in the production of the compositions are shown in Table 1. [TABLE 1 ]
Figure imgf000010_0001
A scanning electron micrograph of fine metal powder obtained by removing Fluorinert FC-70 from the dispersion of a fine powder of a low melting metal produced in Example 1 is shown together with a ratio of magnification in Fig. 1. The state of particle size distribution is shown in Fig. 2. It is noted from Fig. 2 that minute particles measuring 10 to 45 μm, particularly 15 to 35 μm, in diameter were formed in a closely dispersed state in the fluorine type inactive organic solvent.
Examples 5 to 10
Fine powders of a low melting metal were prepared by following the procedure of Examples 1 to 4, except toluene and other solvents were used as inactive organic solvents. The results are shown in Table 2. The speed of stirring was invariably 11,000 r.p. . TABLE 2
Figure imgf000011_0001
Scanning electron micrographs of minute metal particles from the products of Examples 5 to 10 are shown together with ratios of magnification and states of particle size distribution are shown in Figs. 3 to 14.
Example 11
A fine powder of a low melting metal was prepared by following the procedure of Examples 1 to 4. The results are shown in Table 3. The particles of the fine powder produced had diameters in the range of from 10 to 20 μOL. The speed of stirring was 11,000 r.p.m.
TABLE 3
Figure imgf000013_0001
A scanning electron micrograph of metal particles from the product of Example 11 is shown in Fig. 15.
Applied Examples 1 to 3.
The dispersions of fine low melting metal powders prepared in Examples 1 to 11 were subjected to shear stirring at a speed of 11,000 r.p. . in epoxy type or polyamide type adhesive binders by the use of Autohomomixer Type M at temperatures lower than the melting points of the relevant alloys, to prepare compositions having fine low melting metal powders homogeneously dispersed in the polymers. The percentage compositions and the stirring conditions are summarized in Table 4.
TABLE 4
Figure imgf000014_0001
Applied Example 1
A blend A was prepared by mixing 20 g of the fine dispersion of Example 1, 43 g of EPON 828, 5 g of DICY, 1.9 g of anhydrous silica, 12 g of nitrile type modifier CTBN, and 16.8 g of EPON 1009. It was heated and stirred at about 120βC for one hour to evaporate the Florinate (about 10 g contained) . The residue was cooled to below 50°C and then dissolved in 6.3 g of finely divided DICY and 80 g of methylethyl ketone as a solvent. The resultant 50 p thin solution was coated to a silicon-treated PET film, and dried to produce an anisotropic electroconductive film.
This anisotropic electroconductive film was used to join a copper circuit formed by patterning on a flexible substrate of CTCpit 0.6 mm under the conditions of 16 kgf/cm2 of bonding pressure and 215βC of bonding temperature for a period of two minutes, using "Bonder J-3" (Sumitomo 3M) .
The electroconductivity had a very small magnitude of less than 0.1 Ω.
Applied Example 2
Twenty (20) g of the fine dispersion of
Example 2 and 100 g of a polyamide type hotmelt JA-7375 were mixed by stirring. The stirring was continued at a temperature of 160°C, to effect incorporation of solder particles into the polyamide resin and, at the same time, vaporization of Florinate as a dispersant.
By molding the residual coating in the form of a film, a hotmelt type anisotropic electroconductive film was produced.
Applied Example 3
One hundred (100) g of the fine dispersion of Example 1 was left standing for one day to effect sedimentation of solder particles. The supernatant Florinate was discarded and 10 g of the powdery flux resin was dispersed. The resultant creamy paste was heated to produce a creamy solder possessing electroconductivity.

Claims

WHAT IS CLAIMED IS:
1. A method for the production of a fine powder of a low melting metal, characterized by introducing a low melting metal having a melting point in the range of from 47°C to 321βC into an inactive organic solvent possessed of a decomposition point or boiling point higher than the melting point of said low melting metal and constantly heated at a temperature higher than the melting point of said low melting metal and lower than the boiling point of said inactive organic solvent, and dispersing and mixing said low melting metal in the form of minute particles by shear stirring in said inactive organic solvent.
2. A method according to claim 1, wherein said low melting metal is solder.
3. A method according to claim 1, wherein said inactive organic solvent is a fluorine type inactive organic solvent.
4. A method according to claim 1, wherein said inactive organic solvent is toluene, xylene, diemthylformamide, dimethylsulfoxide,
1,1,2-trichloroethane, tetrachloroethane, or a silicon type organic solvent.
5. A method for the production of a composition containing a fine powder of a low melting metal, characterized by preparing a fine powder of a low melting metal produced by the method set forth in any of claims 1 to 4 in a state having the surface thereof coated with an inactive organic solvent, introducing said coated fine powder into a polymer or a polymer precursor having a softening point or a melting point lower than the melting point of said low melting metal and stirring said polymer or polymer precursor thereby dispersing and mixing said fine powder of low melting point in said polymer or polymer precursor.
6. A method according to claim 5, wherein said polymer is a polyamide resin.
7. A method according to claim 5, wherein said inactive organic solvent is a fluorine type inactive organic solvent.
PCT/US1992/005767 1991-07-15 1992-07-09 Manufacturing method of low melt metal fine particles WO1993002221A2 (en)

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US20020046627A1 (en) 1998-06-10 2002-04-25 Hitoshi Amita Solder powder, flux, solder paste, soldering method, soldered circuit board, and soldered joint product
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JP5807421B2 (en) * 2011-07-19 2015-11-10 三菱マテリアル株式会社 Detergent for solder powder and method for producing solder powder
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JPH0533017A (en) 1993-02-09

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