JP2000315425A - Conductive fine particles and conductive connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of crack or wrinkle of a metallic coating layer and separation of it from a resin base-material particle, by forming the metallic coating layer around a graft polymeric layer formed around the resin base- material particle. SOLUTION: An average grain size and a grain size variation coefficient of a spherical or spheroidal resin base-material particle 11 made of a linear polymer, a net polymer, a resin material such as thermo-setting resin, or organic or inorganic hybrid material are set in ranges for facilitating formation of a uniform metallic coating layer 13 and joining between micro electrodes. A graft, polymeric layer 12 made of one or more kinds of monomer such as styrene. The metallic coating layer 13 with a single layer or a plurality of layers has a thickness in a range that does not cause high resistance or high cost, and is formed by electroless or electrolytic plating, vacuum deposition, or sputtering of Cu or Ni. The metallic coating layer 13 is engaged with the graft polymeric layer 12 to improve adhesiveness, and is highly reliably used for a conductive connection structure such as a semiconductor element.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to conductive fine particles used for connection between electrodes and a conductive connection structure using the conductive fine particles.

[0002]

2. Description of the Related Art In electronic products such as a liquid crystal display, a personal computer, and a portable communication device, the electrical connection between an electronic component or an electronic component element and an electrode substrate, such as flip-chip bonding or connection using a ball grid array (BGA). In connection, metal fine particles made of solder, nickel, copper, or the like have been used. However, these metal fine particles have the drawback of being too hard or poor in elasticity, and the conductive connection structure using these metal fine particles has cracks in the connection part when a cooling / heating cycle test is performed. There were problems such as easy occurrence.

In order to solve such a problem, an anisotropic conductive film is prepared by using conductive fine particles having a metal coating layer provided around the resin base particles by electroless plating. It has been proposed to use a conductive film for conductive connection between an electronic component or an electronic component element and an electrode substrate. (Japanese Patent Laid-Open No. 61-
JP-A-664882, JP-A-61-277105, JP-A-63-190204, JP-A-01-2
No. 42782 and JP-A-09-137289). However, the conventional conductive fine particles provided with a metal coating layer around the resin base particles by electroless plating or electrolytic plating have the following problems.

That is, in the conventional conductive fine particles, the adhesion between the metal coating layer made of nickel, gold or the like and the resin base material particles is insufficient. When pressure was applied between the substrates or shear stress was applied, the metal coating layer was easily peeled off or detached from the surface of the resin base material particles.

[0005] Further, when a thermal cycle test is performed using a conventional conductive connection structure using conductive fine particles,
Cracks and wrinkles were easily generated in the metal coating layer. Further, since the conventional conductive fine particles have the above-described problems, the resistance value of the conductive fine particles increases at the junction of the conductive connection structure, and the obtained conductive connection structure has a sufficient reliability. Did not have.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and has as its object to provide conductive fine particles having a metal coating layer which does not crack or wrinkle and which does not peel off or detach from resin base particles. Aim. Another object is to provide a highly reliable conductive connection structure manufactured using the conductive fine particles.

[0007]

The present invention is characterized in that a graft polymer layer is formed around resin base particles and a metal coating layer is further formed around the graft polymer layer. Fine particles. Hereinafter, the conductive fine particles of the present invention will be described with reference to the drawings.

FIGS. 1A and 1B are sectional views showing one embodiment of the conductive fine particles of the present invention. As shown in FIG. 1A, the conductive fine particles of the present invention have resin base particles 11
A graft polymerization layer 12 is formed around the
A metal coating layer 13 is formed around the periphery.

The resin base particles 11 include particles made of a resin material or an organic / inorganic hybrid material. As the resin material, for example, polystyrene,
Linear polymers such as polymethyl methacrylate, polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polysulfone, polycarbonate, and polyamide; divinylbenzene, hexatriene, divinyl ether, divinyl sulfone, diallyl carbinol, alkylene diacrylate, oligo or poly Alkylene glycol diacrylate, oligo or polyalkylene glycol dimethacrylate, alkylene triacrylate, alkylene tetraacrylate, alkylene trimethacrylate, alkylene tetramethacrylate, alkylene bisacrylamide, alkylene bismethacrylamide, acryl-modified polybutadiene oligomer at both ends alone or other Network obtained by polymerizing with polymerizable monomer Polymer; phenol formaldehyde resins, melamine formaldehyde resins, benzoguanamine-formaldehyde resins, and thermosetting resins such as urea-formaldehyde resins.

As the organic / inorganic hybrid material, for example, a copolymer of (meth) acrylate having a silyl group in a side chain and a vinyl monomer such as styrene or methyl methacrylate is prepared, and then the silyl group is subjected to a condensation reaction. What was made; tetraethoxysilane, triethoxysilane, diethoxysilane, etc. in the presence of an organic polymer
Gel-reacted ones include those obtained by performing a sol-gel reaction of tetraethoxysilane, triethoxysilane, diethoxysilane, and the like, and then firing at low temperature to leave organic components.

The method for synthesizing the above-mentioned resin material and organic / inorganic hybrid material is not particularly limited, and a conventionally known synthesis method such as a suspension polymerization method, a seed polymerization method, a dispersion polymerization method, and a Steber method by a sol-gel reaction is used. It may be appropriately selected and used.

The shape of the resin base particles 11 is spherical or spheroidal. The average particle diameter of the resin base particles 11, that is, the diameter thereof when the resin base particles 11 are spherical and the long diameter thereof when the resin base particles 11 are spheroidal are preferably from 1 to 1000 µm, more preferably from 2 to 500 µm. Average particle size is 1
If it is less than μm, it is difficult to form a uniform coating layer on the resin base particles, and if it is more than 1000 μm, it is difficult to bond the fine electrodes. The average particle diameter is a value obtained by observing and measuring 300 arbitrary resin base material particles with an electron microscope.

The coefficient of variation (CV value) of the particle size distribution of the resin base particles 11 is preferably 5% or less, more preferably 3% or less. If the CV value is more than 5%, the particle diameter of the resin base particles becomes uneven. Therefore, when the electrodes are connected via the conductive fine particles produced using the resin base particles, the electrodes are involved in the connection. Undesired conductive fine particles may be generated, and a leak phenomenon may occur between adjacent electrodes.

The CV value is defined by the following equation (1): CV value (%) = (σ / Dn) × 100 (1) (where σ represents the standard deviation of the particle diameter) , Dn represent the number average particle diameter). The standard deviation and the number average particle diameter are values obtained by observing and measuring 300 arbitrary resin base particles with an electron microscope.

In the conductive fine particles 10 of the present invention, a graft polymerization layer 12 is formed around resin base particles 11.
The thickness of the graft polymerization layer 12 is preferably from 0.001 to 10 μm, more preferably from 0.01 to 1 μm.

The monomers used for forming the graft polymerized layer 12 include, for example, styrene, α-methylstyrene, methyl acrylate, methyl methacrylate, isobutyl methacrylate, acrylonitrile, vinylpyrrolidone, glycidyl methacrylate, hydroxyethyl Methacrylate, hydroxypropyl methacrylate, lauryl methacrylate, vinyl acetate, vinyl chloride, ethylene, propylene, butadiene, isoprene, allyl phthalate, methacryloxymethyltrimethoxysilane, methacryloxypropyltriethoxysilane, polyalkylene glycol monomethacrylate, acrylic acid, methacryl Acid, ethyl phosphate methacrylate, propyl phosphate methacrylate, butyl phosphate methacrylate, dimethyl methacrylate Minoechiru, dimethylaminoethyl methacrylate methyl chloride salt, acrylamide, methacrylamide. These monomers may be used alone or in combination of two or more.

Of these, those containing a small amount of a carboxyl group, a phosphate group and / or an amino group are preferred. It is also preferable to include a small amount of a polyfunctional monomer such as divinylbenzene, trimethylolpropane triacrylate, or tetramethylolmethanetetraacrylate in the monomer, since the graft chains can be crosslinked. Further, the graft polymerization layer 12 includes
Polymers such as polyamides, polyesters, and polyvinyl alcohols may be bonded by a polymer reaction.

As a method for forming the graft polymerization layer 12 around the resin substrate particles 11, a conventionally known method ("Graft Polymerization and Its Application" by Fumio Ide, Polymer Publishing Association, 1
984; Japanese Patent Application Laid-Open No. 9-244034). Specifically, for example, a method in which an unsaturated bond such as a double bond existing on the surface of the resin base material particles is cleaved using a radical polymerization initiator to graft-polymerize a vinyl monomer; cerium salt (IV), A method in which radicals are generated on the surface of resin base particles having a reducing group such as an alcoholic hydroxyl group on the surface thereof with an oxidizing agent such as iodate, and a vinyl monomer is graft-polymerized from the radicals; persulfate-halogen Method for graft polymerization using a redox catalyst such as lithium fluoride, persulfate-acid sulfite, persulfate-Ag, persulfate-hydroxyl, hydrogen peroxide-metal salt, etc .; perester group Graft polymerization starting from a functional group such as a mercapto group or a diazo group;
A method of activating the surface of resin base particles by physical means such as low-temperature plasma, electron beam, or gamma-ray irradiation and then graft-polymerizing a polymerizable monomer; amino groups, hydroxyl groups, etc. present on the surface of the resin base particles A method in which a graft polymer is bonded to the reactive group by a polymer reaction.

In the conductive fine particles 10 of the present invention, a metal coating layer 13 is further formed around the graft polymerization layer 12. The thickness of the metal coating layer 13 is preferably 0.05 to 100 μm, and more preferably 0.1 to 50 μm. If the thickness of the metal coating layer 13 is less than 0.05 μm, the resistance value of the conductive fine particles may increase, and sufficient conductivity may not be obtained. On the other hand, even if the thickness of the metal coating layer 13 exceeds 100 μm, the resistance value of the conductive fine particles hardly changes, which is disadvantageous in cost.

The structure of the metal coating layer 13 may be a single layer structure or a multilayer structure of two or more layers. When the metal coating layer has a multilayer structure composed of two layers as shown in FIG. 1 (b), the outer metal coating layer 13b is formed of a low-melting-point metal from the viewpoint of easy fusion. It is preferred that Also in the case of a multilayer structure having three or more metal coating layers, the outermost layer is preferably a metal coating layer made of a low melting point metal. The low-melting-point metal means a metal having a lower melting point than the metal constituting the inner metal coating layer.

Examples of the metal used for forming the metal coating layer 13 include IB group and VII in the periodic table.
Examples include metals belonging to Group I, Group IIB, Group IIIB, Group IVB, Group VB, and the like. Among them, group IB includes copper, silver and gold, group VIII includes nickel, palladium and platinum, group IIB includes zinc, group IIIB includes gallium, aluminum, indium, and IV.
As group B, tin and lead are preferable, and as group VB, bismuth is preferable. These metals may be used alone or in combination of two or more alloys.

The method for forming the metal coating layer 13 is not particularly limited, and a conventionally known method can be used.
Specifically, for example, electroless plating, electrolytic plating,
Examples thereof include a vacuum evaporation method and a physical evaporation method using sputtering.

Hereinafter, nickel-gold plating, which is an example of a metal coating layer formed by using such a method, will be described. In the above-mentioned nickel-gold plating, after electroless nickel plating is performed on the surface of the resin substrate particles on which the graft polymerized layer is formed, a gold plating layer is formed on the surface by displacement plating. The electroless nickel plating includes a catalyst application step and a nickel reduction plating step.

In the catalyst application step, a catalyst serving as a plating nucleus is deposited or adsorbed on the surface of the resin base material particles on which the graft polymerization layer is formed. In this case, a platinum group metal compound may be used. preferable. Specifically, after immersing the resin base particles having the graft polymerization layer in a hydrochloric acid solution of stannous chloride, the resin substrate particles are further immersed in a hydrochloric acid solution of palladium chloride, heated and washed with water. In the particles thus obtained, palladium is precipitated as ultrafine particles having a particle diameter of 50 nm or less in the graft polymerization layer and on the surface of the graft polymerization layer.

Alternatively, the resin base particles having the graft polymerization layer may be immersed in a mixed solution of tin chloride and palladium chloride, and then tin may be eluted and removed using an aqueous solution of hydrochloric acid or sulfuric acid. Also in this case, similarly to the above, ultrafine particles of palladium are precipitated in the graft polymerization layer and on the surface of the graft polymerization layer.

Further, resin base particles having a graft polymerization layer may be immersed in a mixed aqueous solution of palladium chloride, a water-soluble monomer such as polyvinylpyrrolidone, polyacrylamide, polyvinylpyridine, and the like, and ascorbic acid (Japanese Patent Application Laid-Open (JP-A) no. 61-166977). Also in this case, similarly to the above, ultrafine particles of palladium are precipitated in the graft polymerization layer and on the surface of the graft polymerization layer.

Next, nickel reduction plating is performed using the resin base particles having the graft polymerized layer provided with the catalyst by the above method. As a method for performing the nickel reduction plating, a conventionally known method ("Latest Electroless Plating Technology"published; General Technology Center, 1986, p. 43, etc.) can be used. Can be used. When acid plating is used as the nickel reduction plating, the catalyst-treated particles are immersed in a nickel chloride or nickel sulfate solution, and the nickel reduction is performed while dropping a sodium hypophosphite solution under conditions of pH 4 to 6. By performing the above, a nickel plating layer can be formed on the particle surface.

When alkaline plating is used, a nickel plating layer can be formed on the particle surfaces by reducing nickel while dropping boric acid or borax solution under conditions of pH 8 to 10. . The nickel reduction reaction in the nickel reduction plating proceeds on the graft polymerization layer and the ultrafine particles of palladium existing on the surface of the graft polymerization layer, whereby a nickel plating layer is formed.

Next, a gold plating layer is formed on the particles having the nickel plating layer formed thereon by displacement plating. The gold plating is performed by partially eluting nickel and simultaneously depositing gold on the surface of the nickel plating layer.
Specifically, the method is carried out by charging the particles having the nickel plating layer formed therein into a solution comprising potassium cyanide alloy, EDTA and ammonium chloride, and heating the solution.

The conductive fine particles 10 having such a configuration
In this case, since the metal coating layer 13 is formed so as to bite into the graft polymerization layer 12, the adhesion between the resin base particles and the metal coating layer is extremely good, and the two are not easily separated. Therefore, a highly reliable conductive connection structure can be manufactured by using the conductive fine particles of the present invention.

The above-mentioned conductive connection structure may be obtained by fixing conductive fine particles to a substrate or an electrode part of an electronic component element, or by connecting an electrode part of a substrate or an electronic part element to an electrode part of another substrate or an electronic part element. Are formed by using conductive fine particles to connect between them.

As the substrate used for the conductive connection structure, for example, paper phenol resin, glass epoxy resin,
Examples include a printed wiring board based on a glass polyimide resin or the like, a flexible printed wiring board made of polyimide, a saturated polyester resin, or the like, a ceramic substrate, and the like. The structure of the substrate may be a single-layer structure or a multi-layer structure.

The substrate is provided with wiring made of a material such as gold, silver, copper, aluminum and carbon.
An electrode portion is formed at a specific position of this wiring. The electrode portion is formed at a position corresponding to an electrode portion of an electronic component element or another substrate connected thereto.

Further, the conductive fine particles of the present invention may be fixed to the electrode portion. In order to fix the conductive fine particles to the electrode portion, using a ball mounter or a particle disperser, the conductive fine particles are placed or sprayed on the electrode portion, and then the metal coating layer of the conductive fine particles and the electrode portion of the substrate are used. And a method in which a low-melting metal such as solder is melted and joined, a soft metal such as gold, silver, and indium is pressed and joined, or a resin paste, a conductive paste, or the like is used for fixing. .

Examples of the electronic component element used for the conductive connection structure include a semiconductor element, a resistance element, a capacitor element, a thin film memory element, a crystal oscillator, and the like. Specific examples of the semiconductor element include a diode, a transistor, an IC, an LSI, an SCR, a photoelectric element, a solar cell, an LED, and the like. Further, the above IC
Specific examples of bare chip, package type I
C, a chip size package (CSP), and the like.

The electrodes of the electronic circuit element in the conductive connection structure of the present invention can be produced by a vapor deposition method, a sputtering method, or the like. Examples of the material of the electrodes of the electronic circuit element include aluminum, copper, nickel chrome-gold (or copper), chromium-gold, nickel chromium-palladium-gold, nickel chromium-copper-palladium-gold, molybdenum-gold, Combinations of titanium-palladium-gold, titanium-platinum-gold and the like can be mentioned. Examples of the arrangement of the electrodes of the electronic circuit element include a peripheral type, an area type, and a mixed type thereof.

The conductive fine particles of the present invention may be fixed to the electrode part of the electronic component element. As a method of fixing the conductive fine particles to the electrode portion, a method similar to the method of fixing the conductive fine particles to the electrode portion on the substrate can be used.

As a method for manufacturing the conductive connection structure having such a configuration, for example, the following method can be used. That is, after the conductive fine particles are fixed to the electrode portion of the substrate or the electronic component element by the above-mentioned method, the conductive fine particles can be manufactured by connecting the conductive fine particles to the electrode portion of another substrate or the electronic component element. . At the time of connection, cream solder, resin paste, conductive paste, or the like may be used as an auxiliary.

Further, after the conductive fine particles are placed or sprayed on at least the substrate or the electrode portion of the electronic component element using a ball mounter or a particle disperser, the other substrate or the electronic component element is connected to the other electrode section. At opposite positions,
Overlap. Then, using a bonding machine, by applying heat and / or pressure, to melt the low melting point metal forming the metal coating layer of the conductive fine particles,
It can be produced by pressing a soft metal such as gold, silver or indium. When connecting,
A cream solder, a resin paste, a conductive paste, or the like may be used as an auxiliary.

Further, after dispersing the conductive fine particles in a resin binder solution, the film is cast by casting to obtain a film. The film is placed on a substrate or an electronic component element, and then the other substrate or the electronic component element. Are placed at positions where the electrode portions face each other, and are superposed. In addition, instead of the above film, conductive fine particles are mixed with a liquid resin binder,
A conductive paste may be prepared by dispersing the paste, and the paste may be applied to the substrate or the electrode-side surface of the electronic component element. Next, in this state, a conductive connection structure can be manufactured by applying heat and / or pressure using a bonding machine. In general, a conductive protrusion called a bump is formed in advance on one of the electrodes of the substrate or the electronic component element, but such a bump may be omitted.

As a package system of these conductive connection structures, a flip chip shown in a sectional view in FIG. 2 and a ball grid array shown in a sectional view in FIG. 3 are preferably used. In the flip chip shown in FIG. 2, an electrode portion 24a provided on a semiconductor element 22 and an electrode portion 24b provided on a substrate 23 are connected via conductive fine particles 21,
The gap between the semiconductor element 22 and the substrate 23 is filled with an underfill material 25 as a resin binder.

In the ball grid array shown in FIG. 3, a semiconductor element 32 is connected to one surface of a substrate 33 by a package method such as the above-mentioned flip chip.
Is covered with a sealing resin 36, and the other surface of the substrate 33 is provided with an electrode portion 34 to which the conductive fine particles 31 are fixed. Note that the conductive fine particles 31 are connected to an electrode portion of another substrate or the like, but are not illustrated here.

As the conductive fine particles used in the conductive connection structure, in the case of the flip chip, the particle diameter is 1
In the case of the ball grid array, those having a particle diameter of 50 to 700 μm are preferable.

In the conductive connection structure, one or a plurality of the conductive fine particles are arranged per electrode portion. Usually, the gap between the electronic component element and the substrate is filled with an underfill material as a resin binder. However, there is no particular problem even if the use of the underfill material is omitted.

The conductive connection structure thus obtained is produced using conductive fine particles having a metal coating layer which does not crack or wrinkle and does not peel off or detach from the resin base particles. Therefore, its reliability is high. The above-described conductive connection structure is also one aspect of the present invention.

[0046]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Embodiment 1Preparation of resin base particles  800 g of a 3% solution of polyvinyl alcohol in divinyl
A mixture of 100 g of benzene and 2 g of benzoyl peroxide
In addition, gently agitate to reduce the center particle diameter of the monomer droplet.
Was adjusted to about 100 μm. That
Thereafter, the temperature was raised to 80 ° C. while stirring, and the reaction was carried out for 15 hours.
To obtain fine particles. The obtained fine particles are
After washing, it was classified. As a result, the polyvinyl chloride
Fine particles having a hydroxyl group of nyl alcohol were obtained. This fine
The average particle size of the particles is 42.0 μm, and the standard deviation is
0.5 μm and has a substantially normal particle size distribution.
Was. Using the fine particles obtained by the above operation as resin base particles,
The following operations were performed.

[0048]Preparation of resin base particles having a graft polymerization layer
Made  In a separable flask, add 250 g of ion-exchanged water,
5 g of xymethyl methacrylate and the resin base particles 5
g was added and sufficiently dispersed, followed by stirring. this
0.1 mol / l nitric acid prepared with 1N nitric acid aqueous solution
12.5 g of ceric ammonium salt solution was added,
A graft polymerization layer is formed by reacting for 5 hours.
Resin base particles were obtained. Wash the obtained resin base particles thoroughly
Purified and dried. After drying, the cross section of the resin base particles
When observed with an electron microscope, a 0.08 μm thick
A raft polymerized layer was formed.

[0049]Applying plating catalyst  5 g of the resin base particles having the graft polymerized layer formed thereon was tin
Solution consisting of a double salt of palladium and palladium (Okuno Pharmaceutical Company)
10%, 37% hydrochloric acid 10ml
And immersed in 10 ml of methanol, followed by filtration. filtration
After completion, the residue on the filter paper is washed with 5% sulfuric acid and further washed with water.
As a result, fine particles provided with a plating catalyst were obtained.
The obtained fine particles exhibit a light brown color, and are contained in the graft polymerization layer.
Ultra fine particles of palladium were precipitated.

[0050]Nickel reduction plating  Nickel sulfate 17g / 100ml and sodium pyrophosphate
Plating with a composition of 34g / 100ml
Adjust the solution and add the fine particles with the plating catalyst
And then stirred at 70 ° C. for 60 minutes while stirring
While dropping 17g / 100ml of sodium acid
Nickel plating on the surface
Fine particles were obtained.

[0051]Gold displacement plating  The resulting nickel-plated particles are suspended in water
And with stirring, gold consisting of potassium gold cyanide 5%
By heating to 70 ° C while dropping the displacement plating solution
A metal replacement reaction was performed to obtain conductive fine particles. In addition,
The progress of the conversion reaction is when the particles change from black gray to gold
Confirmed by After completion of the gold substitution reaction, the resulting conductive fine
Observation of the cross section of the particles with an electron microscope revealed that the thickness was 0.3
5μm nickel plating layer and 0.09μm thick gold plating
A stick layer was formed. In addition, 5% compression
It was 0.08Ω when the resistance was measured under the condition that strain was given.
And showed good conductivity.

[0052]Adhesion of metal coating layer to resin substrate particle surface
Evaluation  The obtained conductive fine particles were placed in two pieces of glass having a thickness of 1.1 mm.
60 pieces per square mm between
The end of the glass plate was sealed with tape. Next, the gala
50 times of rubber roller with a load of 5 kg applied to the surface of the plate
Ironing was given by reciprocating. After ironing,
Observation of conductive fine particles with a magnifying glass of 50x magnification
Of course, the metal coating layer of conductive fine particles is not damaged at all.
And no peeling was observed.
It had adhesive properties.

Comparative Example 1 Example 1 was repeated except that no graft polymerization layer was formed.
In the same manner as in the above, conductive fine particles were obtained. With respect to the obtained conductive fine particles, the adhesion of the metal coating layer to the resin base material particle surface was evaluated in the same manner as in Example 1, and peeling of the metal coating layer was observed.

Example 2 Fine particles having a graft polymerization layer formed thereon were obtained in the same manner as in Example 1. A plating catalyst was applied to the obtained fine particles in the same manner as in Example 1, and further, nickel reduction plating was performed.
The nickel film thickness after the completion of the nickel reduction plating was 0.10 μm. Next, 10 g of the obtained fine particles whose surface was nickel-plated were taken, and the surface was subjected to electroplating using an electroplating apparatus 40 shown in a sectional view in FIG.

The electroplating apparatus 40 includes a vertical drive shaft 50.
A disk-shaped bottom plate 47 fixed to the upper end of the bottom plate 47, an annular porous body 49 disposed on the outer peripheral upper surface of the bottom plate 47 and passing only the plating solution, and an energizing contact ring disposed on the upper surface of the porous body 49 48, a substantially conical hollow cover 41 having an opening 46 in the center where an annular lower outer peripheral portion is disposed on the contact ring 48, and between the lower outer peripheral portion of the hollow cover 41 and the bottom plate 47. A rotatable plating tank 51 formed by sandwiching a porous body 49 and a contact ring 48, an electrode 42 inserted through an opening 46 of the plating tank 51 and contacting a plating solution,
A supply pipe 44 for supplying a plating solution from the opening 46 to the plating tank 51, a container 43 for receiving the plating solution scattered from the holes of the porous body 49, and a discharge pipe 45 for discharging the plating solution accumulated in the container 43. Have.

In the electroplating apparatus 40, fine particles are charged into the plating tank 51, and a plating solution is supplied from the supply pipe 44 into the plating tank 51. Since the plating solution flows out of the plating tank 51 through the porous body 49 with the rotation of the drive shaft 50, the reduced amount is supplied from the supply pipe 44.

The fine particles are energized and plated while being pressed against the contact ring 48 by the action of centrifugal force due to the rotation of the plating tank 51. Since the rotation is also decelerated and stopped simultaneously with the stop of energization, the fine particles are dragged by the flow due to gravity and the inertia of the plating solution and move toward the center of the bottom plate 47. While being mixed with the plating solution, it is pressed against the contact ring 48 in another posture and plated. By repeating this cycle, a plating layer having a uniform thickness is formed on all the fine particles present in the plating tank 51.

The plating conditions in this operation were as follows: the temperature of the plating solution was 50 ° C., the current was 36 A, and the current density was 0.
36 A / dm ² voltage is set to 15 to 16 V, and 2
The electricity was supplied for 0 minutes. The peripheral speed of the plating tank 51 is 250 m
/ Min, and the rotation direction was reversed every 11 seconds. By performing this electroplating, nickel-plated fine particles having a nickel film thickness of 2.0 μm were obtained.

Next, the obtained nickel-plated fine particles 10
g, and eutectic solder plating was performed using an electroplating apparatus 40.

The plating conditions in this operation were as follows. An alloy of tin (Sn): lead (Pb) = 6: 4 was used for the electrode 42, and an acidic bath (537 manufactured by Ishihara Chemical Co., Ltd.) was used as a plating solution.
A) was used. The temperature of the plating solution was 20 ° C., the current was 24.8 A, and the current density was 0.5 A / dm ² . The plating solution had a total metal concentration of 21.39 g /
1, containing 65.3% of metal ratio Sn% in the bath, 106.4 g / l of alkanolsulfonic acid, and 40 mL of additive.

After plating, conductive fine particles having a solder coating were obtained. When the solder coating of the conductive fine particles was analyzed by an atomic absorption method, Sn was 61.3%,
Melting point was 187 ° C. The resistance under the condition where 5% compression strain was applied to the fine particles was 0.02Ω.
And showed good conductivity. Further, with respect to the obtained conductive fine particles, the adhesion of the metal coating layer to the surface of the resin substrate particles was evaluated in the same manner as in Example 1. The metal coating layer was not damaged at all. However, it had strong adhesion to the resin base particles.

Comparative Example 2 Example 2 was repeated except that no graft polymerization layer was formed.
In the same manner as in the above, conductive fine particles were obtained. With respect to the obtained conductive fine particles, the adhesion of the metal coating layer to the resin base material particle surface was evaluated in the same manner as in Example 1, and peeling of the metal coating layer was observed.

Embodiment 3Preparation of resin base particles  2.4 g of polyvinylpyrrolidone, anionic surfactant
(Aerosol OT, manufactured by Wako Pure Chemical Industries, Ltd.) 1.2 g
2.8 g of azobisisobutyronitrile in ethanol
Under a nitrogen stream while stirring the solution dissolved in 180 g
30 g of styrene is added, and the temperature is raised to 70 ° C. for 24 hours.
A polymerization reaction was performed. Thus, the average particle size is 1.6 μm.
m, and seed particles having a standard deviation of 0.032 μm were obtained. Get
200 g of ion-exchanged water and lauri
0.13 g of sodium sulphate is added and dispersed uniformly,
A seed particle dispersion was obtained.

Separately, 5.1 g of benzoyl peroxide was added to 340 g of a monomer mixture consisting of 30 parts by weight of styrene, 20 parts by weight of glycidyl methacrylate, and 50 parts by weight of divinylbenzene, and the mixture was roughly dispersed with a homogenizer. An emulsion having an average particle diameter of the monomer droplets of 0.2 μm was obtained by sonication. Next, this emulsion was added to the seed particle dispersion and stirred at 25 ° C. for 3 hours. As a result, the monomer mixture was completely absorbed by the seed particles.

Further, 850 g of a 3% solution of polyvinyl alcohol was added to this dispersion, followed by carrying out a polymerization reaction at 70 ° C. for 12 hours to obtain resin base particles. The obtained resin base particles were washed with water and ethanol, and then dried. As a result, the average particle diameter was 6.5 μm, and the standard deviation was 0.1.
14 μm resin base particles were obtained.

[0066]Preparation of resin base particles having a graft polymerization layer
Made  To 10 g of the resin base particles, methyl ethyl ketone 200
g and 30 g of methacryloyl isocyanate.
Reaction at 60 ° C for 60 minutes, polymerizable
And 10 g of the particles are introduced with methyl ethyl group.
Ketone 200 g, isobutyl methacrylate 50 g,
Methyl acrylate 45g, Butyl phosphate methacrylate
5 g and benzoyl peroxide 0.5 g were added and stirred.
The temperature was raised to 70 ° C in a nitrogen stream with stirring, and
The formation of the graft polymerization layer
The obtained resin base particles were obtained. Sufficiently obtained resin base particles
Washed and dried. After drying is completed, the cross section of the obtained fine particles
Was observed with an electron microscope.
A raft polymerized layer was formed.

[0067]Applying plating catalyst  5 g of the resin base particles having the obtained graft polymer layer formed thereon
The plating catalyst was applied in the same manner as in Example 1.
Fine particles were obtained.Nickel reduction plating  Example 1 of the fine particles provided with the plating catalyst
To obtain nickel-plated fine particles
Was.

[0068]Gold displacement plating  Regarding the fine particles whose surface is nickel-plated,
By performing gold displacement plating in the same manner as in Example 1,
Conductive fine particles were obtained. The cross section of the obtained conductive fine particles is
When observed with a microscope, a nickel with a thickness of 0.35 μm
A gold plating layer with a thickness of 0.09 μm.
Had been. In addition, a condition where 5% compression strain is applied to the fine particles
The measured resistance was 0.08Ω, which was good.
Showed conductivity.

[0069]Adhesion of metal coating layer to resin substrate particle surface
Evaluation  About the obtained conductive fine particles, it carried out similarly to Example 1.
When the adhesion of the metal coating layer to the resin substrate particle surface was evaluated
At this time, the metal coating layer of conductive fine particles is damaged
No peeling is observed, strong against resin base particles
It had adhesiveness.

Comparative Example 3 Example 3 was repeated except that no graft polymerization layer was formed.
In the same manner as in the above, conductive fine particles were obtained. With respect to the obtained conductive fine particles, the adhesion of the metal coating layer to the resin base material particle surface was evaluated in the same manner as in Example 1, and peeling of the metal coating layer was observed.

[0071]

Since the conductive fine particles of the present invention have the above-mentioned structure, they do not have cracks or wrinkles and have a metal coating layer which does not peel off or detach from the resin base particles. Further, the conductive connection structure of the present invention is manufactured using the conductive fine particles, and has high connection reliability.

[Brief description of the drawings]

FIGS. 1A and 1B are cross-sectional views showing one embodiment of the conductive fine particles of the present invention.

FIG. 2 is a cross-sectional view showing an example of the conductive connection structure of the present invention.

FIG. 3 is a cross-sectional view showing an example of the conductive connection structure of the present invention.

FIG. 4 is a sectional view showing an electroplating apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 conductive fine particles 11 resin base particles 12 graft polymer layer 13, 13 a, 13 b metal coating layer 21 conductive fine particles 22 semiconductor element 23 substrate 31 conductive fine particles 32 semiconductor element 33 substrate

Continued on the front page F term (reference) 4K022 AA13 AA41 BA01 BA02 BA03 BA08 BA10 BA14 BA17 BA18 BA21 BA25 BA28 DA01 5E319 AA03 AB05 BB04 BB16 GG11 5G307 AA02 HA02 HB06 HC01

Claims (2)

[Claims] 1. A conductive fine particle comprising: a graft polymer layer formed around resin base particles; and a metal coating layer further formed around the graft polymer layer. 2. A conductive connection structure produced using the conductive fine particles according to claim 1.