JP6671881B2 - Conductive fine particles, anisotropic conductive material, and conductive connection structure - Google Patents

Description

The present invention relates to conductive fine particles capable of performing highly reliable electrical connection and producing a conductive connection structure with a high yield. In addition, the present invention relates to an anisotropic conductive material containing the conductive fine particles, and a conductive connection structure connected by the conductive fine particles or the anisotropic conductive material.

As a method of conductively connecting the electrodes of the electronic circuit board, a method of providing a metal layer made of a highly conductive metal on the surface of the base fine particles and using conductive fine particles further formed with a solder layer on the metal layer is known. It has been proposed (for example, Patent Document 1).

In the method of electrically connecting between electrodes of a package substrate using such conductive fine particles, first, conductive fine particles are arranged on electrodes formed on one package substrate, and the solder layer is melted by reflow. Then, a conductive fine particle disposing step of fixing the conductive fine particles on the electrodes is performed, and then, the electrodes formed on the other package substrate are opposed to the electrodes of the package substrate on which the conductive fine particles are disposed. By arranging and reflowing, a conductive connection step of conductively connecting the electrodes of the substrate is performed to obtain a conductive connection structure.
However, when the conductive connection is performed by such a method, scattering of solder is often observed in the obtained conductive connection structure, or the shape or the like of the conductive connection structure is distorted, so that a sufficient yield is obtained. However, there has been a problem that it is not possible to secure the connection reliability of the obtained conductive connection structure.

JP 2001-220691 A

SUMMARY OF THE INVENTION An object of the present invention is to provide conductive fine particles capable of performing highly reliable electrical connection and producing a conductive connection structure with a high yield. Another object is to provide an anisotropic conductive material containing the conductive fine particles and a conductive connection structure connected by the conductive fine particles or the anisotropic conductive material.

The present invention relates to conductive fine particles having base fine particles and a solder layer formed on the surface of the base fine particles, which are measured under conditions in which a sample is heated to 300 ° C. by a thermal desorption GC-MS method. Conductive fine particles having a content of the gas component of 5 ppm or less.
Hereinafter, the present invention will be described in detail.

The conductive fine particles of the present invention include base fine particles and a solder layer formed on the surface of the base fine particles, and have a gas component content of 5 ppm or less.
The inventors of the present invention have conducted intensive studies and as a result, when conducting connection is performed using conventional conductive fine particles, the yield of the obtained conductive connection structure is reduced or connection reliability is poor. It has been found that the cause is a gas component contained in the conductive fine particles.
For example, when the base fine particles of the conductive fine particles are made of a resin, the raw material monomer, solvent, polymerization initiator, and the like used in the production of the resin fine particles remain in the conductive fine particles. Further, components derived from the plating bath used for forming the solder and other metal layers also remain. By heating during reflow at the time of conductive connection, these residual components are volatilized, which may cause voids in the solder layer, scatter solder, or distort the shape of the conductive fine particles. It was thought that this led to a decrease in connection reliability and yield.
Therefore, the inventors of the present invention have further studied diligently, and by setting the content of the gas component contained in the conductive fine particles to 5 ppm or less, preferably 4.8 ppm or less, the connection reliability is remarkably improved. The present inventors have found that a conductive connection structure can be manufactured with a high yield, and have completed the present invention.

In the present specification, the above-mentioned gas component is contained in the conductive fine particles, and is a reflow temperature (generally a peak temperature of 240 to 260 ° C.) when conducting conductive connection using the conductive fine particles. Means any component that can be volatilized.
The gas component means the content of the gas component measured under the condition of heating the sample to 300 ° C. by the thermal desorption GC-MS method. Specifically, for example, 500 mg of conductive fine particles as a sample is put into an empty thermal desorption tube, and EQUITY-1 (non-polar column, 0.32 mm × 60 m × 0.25 μm) is used as a GC column at 50 ° C. (5 min). ) → 10 ° C./min→300° C. (10 min) Measure the content of gas components when heated to 300 ° C. An example of more specific measurement conditions is shown below.
Thermal desorption device: TurboMatrix 650 (PerkinElmer)
Sample heating: 260 ° C, 15 min (20 ml / min)
Secondary desorption: 350 ° C, 10 minutes
Split: Inlet 15ml / min Outlet 20ml / min Injection rate 40%
GC-MS device: JMS Q1000 (manufactured by JEOL Ltd.)
GC column: EQUITY-1 (non-polar) 0.32 mm × 60 m × 0.25 μm
GC temperature rise: 50 ° C (5 min) → 10 ° C / min → 300 ° C (10 min)
He flow rate: 1.5 ml / min
MS measurement range: 35 to 600 amu (scan 500 ms)
Ionization voltage: 70 eV
MS temperature: ion source; 230 ° C, interface; 250 ° C

The conductive fine particles of the present invention include base fine particles and a solder layer formed on the surface of the base fine particles.
The base fine particles may be resin fine particles made of resin or metal fine particles made of highly conductive metal.
When the base fine particles are metal fine particles, examples thereof include gold, silver, copper, platinum, palladium, cobalt, and nickel. These metals may be used alone or in combination of two or more. Among them, copper is particularly preferable because of its excellent conductivity.
When the base fine particles are resin fine particles, even if distortion or expansion and contraction occur due to an external environment change on the package substrate conductively connected using the conductive fine particles of the present invention, the flexible resin fine particles have conductive properties. Since the stress applied to the fine particles is reduced, high connection reliability can be exhibited.

The resin fine particles are not particularly limited, and include, for example, polyolefin resin, acrylic resin, polyalkylene terephthalate resin, polysulfone resin, polycarbonate resin, polyamide resin, phenol formaldehyde resin, melamine formaldehyde resin, benzoguanamine formaldehyde resin, urea formaldehyde resin, and the like. Resin fine particles.
The polyolefin resin is not particularly limited, and examples thereof include a polyethylene resin, a polypropylene resin, a polystyrene resin, a polyisobutylene resin, a polybutadiene resin, a polyvinyl chloride resin, a polyvinylidene chloride resin, and a polytetrafluoroethylene resin.
The acrylic resin is not particularly limited, and examples thereof include polymethyl methacrylate resin and polymethyl acrylate resin.
These resins may be used alone or in combination of two or more.

A preferred lower limit of the 10% K value of the resin fine particles is 1000 MPa, and a preferred upper limit is 15000 MPa. If the 10% K value is less than 1000 MPa, the resin fine particles may be broken when the conductive fine particles of the present invention are compressed and deformed. If the above 10% K value exceeds 15000 MPa, the conductive fine particles may damage the electrode. A more preferred lower limit of the above 10% K value is 2,000 MPa, and a more preferred upper limit is 10,000 MPa.
The 10% K value was measured using a microcompression tester (eg, “PCT-200” manufactured by Shimadzu Corporation) to compress the resin fine particles at a smoothing end face of a diamond cylinder having a diameter of 50 μm at a compression speed of 2.6 mN / The compression displacement (mm) when the sample is compressed under the condition of a maximum test load of 10 g in seconds is measured, and can be obtained by the following equation.
K value (N / mm ² ) = (3 / √2) · ^FS -3 / 2 · R- ^{1 / 2}
F: Load value (N) at 10% compression deformation of resin fine particles
S: Compressive displacement (mm) at 10% compressive deformation of resin fine particles
R: radius of resin fine particles (mm)

The method for producing the resin fine particles is not particularly limited, and examples thereof include a method using a polymerization method, a method using a polymer protective agent, and a method using a surfactant.
The method by the above polymerization method is not particularly limited, and examples thereof include a method by a polymerization method such as emulsion polymerization, suspension polymerization, seed polymerization, dispersion polymerization, and dispersion seed polymerization.

The preferable lower limit of the average particle diameter of the base fine particles is 25 μm, and the preferable upper limit is 380 μm. When the average particle size is less than 25 μm, the base fine particles are likely to aggregate, and the conductive fine particles obtained using the aggregated base fine particles may short-circuit adjacent electrodes. If the average particle size exceeds 380 μm, the average particle size may exceed the particle size suitable for the conductive fine particles.
A more preferred lower limit of the average particle size is 30 μm, and a more preferred upper limit is 300 μm. A more preferred lower limit of the average particle size is 40 μm, and a more preferred upper limit is 290 μm.
In addition, the average particle diameter of the base fine particles means an average value of diameters obtained by observing 50 base fine particles randomly selected using an optical microscope or an electron microscope.

The preferable upper limit of the CV value of the particle diameter of the base fine particles is 15%. If the CV value exceeds 15%, the connection reliability of the conductive fine particles may decrease. A more preferred upper limit of the CV value is 10%. The CV value is a numerical value represented by a percentage (%) of a value obtained by dividing the standard deviation by the average particle diameter.

When the base fine particles are resin fine particles, in order to further enhance the connection reliability between the conductive fine particles of the present invention and the electrodes of the package substrate, a metal layer is further provided between the resin fine particles and the solder layer. It is preferred to have.
Examples of the metal forming the metal layer include gold, silver, copper, platinum, palladium, cobalt, and nickel. In particular, the metal layer preferably contains copper because of its excellent effect of improving connection reliability.
The metal layer may be formed directly on the resin fine particles, or a base metal layer such as a nickel layer may be formed between the metal layer and the resin fine particles.

The thickness of the metal layer is not particularly limited, but a preferred lower limit is 1 μm and a preferred upper limit is 70 μm. If the thickness of the metal layer is less than 1 μm, a sufficient effect of improving connection reliability may not be obtained. If the thickness of the metal layer exceeds 70 μm, the flexibility of the conductive fine particles may be impaired. A more preferred lower limit of the thickness of the metal layer is 3 μm, and a more preferred upper limit is 50 μm.
The thickness of the metal layer is a thickness obtained by observing a cross section of ten randomly selected conductive fine particles by a scanning electron microscope (SEM) and arithmetically averaging the measured values.

When the base fine particles are resin fine particles and have a metal layer between the resin fine particles and the solder layer, it is preferable to further include a barrier layer between the metal layer and the solder layer.
When the solder layer and the metal layer are in direct contact, tin contained in the solder layer and a metal such as copper contained in the metal layer form an alloy, and are hard at the interface between the solder layer and the metal layer. A brittle alloy layer (for example, a tin-copper alloy) may be formed. When the conductive fine particles on which such a hard and brittle alloy layer is formed are used for connection of a circuit board or the like, an impact such as a drop is applied thereto, and the alloy layer is broken, which may cause disconnection. Further, since the wettability of the solder layer is reduced, the strength of the connection interface between the conductive fine particles and the electrode is reduced, and disconnection may occur at the connection interface. By providing a barrier layer between the metal layer and the solder layer, the formation of such a hard and brittle alloy layer can be prevented.

The material for forming the barrier layer is not particularly limited, and examples thereof include nickel, titanium, tantalum, titanium nitride, zirconia, and zirconia nitride. Above all, it is preferable that the barrier layer contains nickel because the barrier layer is easily formed. The barrier layer preferably has an amorphous structure, and specific examples include a nickel-phosphorous layer and a nickel-boron layer. When the barrier layer has an amorphous structure, the number of crystal grain boundaries is reduced, so that copper is difficult to diffuse into the solder layer.

The thickness of the barrier layer is not particularly limited, but a preferred lower limit is 0.2 μm and a preferred upper limit is 2 μm. When the thickness of the barrier layer is less than 0.2 μm, diffusion of a metal such as copper into the solder layer cannot be prevented, or a hard and brittle alloy is formed at the interface between the solder layer and the copper-containing metal layer. In some cases, formation of a layer (tin-copper) cannot be prevented. If the thickness of the barrier layer exceeds 2 μm, the flexibility of the conductive fine particles may be impaired. A more preferred lower limit of the thickness of the barrier layer is 0.5 μm, and a more preferred upper limit is 1 μm.
The thickness of the barrier layer is a thickness obtained by observing a cross section of ten randomly selected conductive fine particles with a scanning electron microscope (SEM) and arithmetically averaging the measured values.

The solder layer has a role of being melted by reflow to adhere to the electrodes of the package substrate when connecting the electrodes of the package substrate using the conductive fine particles of the present invention.
Preferably, the solder layer contains tin. By containing tin, the strength and the like of the solder layer can be improved.
The solder layer may contain a metal other than tin, such as silver, antimony, copper, bismuth, indium, germanium, aluminum, zinc, and nickel. Specifically, for example, a solder layer containing tin, tin / silver, tin / zinc, tin / silver / copper, tin / bismuth and the like can be mentioned. Above all, it is preferable to use a solder layer containing tin and silver since the melting point of the solder layer is lowered and the strength of the solder layer is improved.

It is preferable that the conductive fine particles of the present invention have nickel, cobalt, iron, manganese, titanium, phosphorus, or bismuth attached to the surface of the solder layer. Among them, nickel or cobalt is preferred.
When the conductive fine particles to which these metals are attached are used for connecting the electrodes of the package substrate, the crystal structure of the intermetallic compound formed at the connection interface between the conductive fine particles and the electrode after reflow is refined. When the intermetallic compound has a fine crystal structure, the crystal structure is hardly broken. When the crystal structure of the intermetallic compound is miniaturized, cracks in the solder layer and breakage due to destruction of the connection interface between the electrode and the conductive fine particles are less likely to occur even when an impact due to dropping or the like is applied. Further, conductive fine particles that are not easily fatigued even when repeatedly subjected to heating and cooling can be obtained. In addition, since it is conceivable that the fine crystal structure of the intermetallic compound distributed at the connection interface exerts an anchor effect, the connection interface between the conductive fine particles and the electrode is less likely to be broken even when an impact such as a drop is applied. .

In addition, since the metal is attached to the surface of the solder layer, tin and the like contained in the solder layer at the time of reflow and the metal attached to the surface preferentially have a crystal structure of a fine intermetallic compound. It is considered to form In particular, when the conductive fine particles of the present invention are mounted on an electrode on which a nickel-phosphorus plating layer and a substitutional gold plating layer are sequentially formed toward the outermost surface, tin and nickel form a crystal structure of a fine intermetallic compound during reflow. Since it is formed, nickel derived from the nickel-phosphorus plating layer can be prevented from diffusing into the solder layer. By preventing the diffusion of nickel derived from the nickel-phosphorus plating layer, the formation of a phosphorus-enriched layer that reduces the strength of the connection interface between the solder layer and the electrode can be suppressed.
The term “the metal adheres to the surface of the solder layer” means that a metal such as nickel is present on the surface of the solder layer and that the metal layer such as nickel completely covers the surface of the solder layer. Means that no is formed.

The amount of the metal adhered to the surface of the solder layer is adhered to the surface of the solder layer in the total of the metal contained in the solder layer and the metal adhered to the surface of the solder layer. The lower limit of the content of the metal adhered to the surface of the solder layer is defined as 0.0001% by weight, and the upper limit is 5.0% by weight. When the content of the metal adhering to the surface of the solder layer is less than 0.0001% by weight, the anchor effect is not sufficiently exhibited, and when an impact such as a drop is applied, the connection between the electrode and the conductive fine particles is caused. The interface is easily broken, and disconnection may occur. If the content of the metal adhering to the surface of the solder layer exceeds 5.0% by weight, the flexibility of the conductive fine particles may be impaired, or the conductive fine particles may not be mounted on the electrode during reflow. A preferable lower limit of the content of the metal adhering to the surface of the solder layer is 0.002% by weight, and a preferable upper limit is 3.0% by weight.
The content of the metal adhering to the surface of the solder layer can be measured using an X-ray fluorescence analyzer (“EDX-800HS” manufactured by Shimadzu Corporation) or the like. The attachment of a metal such as nickel to the surface of the solder layer can be confirmed by a field emission scanning electron microscope FE-SEM (“S-4100” manufactured by Hitachi, Ltd.) or the like.

The method for producing the conductive fine particles of the present invention is not particularly limited. However, in order to reduce the content of the gas component to 5 ppm or less, it is necessary to perform a step of removing the gas component from the conductive fine particles.
The step of removing the gas component from the conductive fine particles is not particularly limited. For example, a method of heating and drying under a temperature condition of 100 to 180 ° C (heating drying method), immersing the conductive fine particles in a solvent such as acetone, A method of removing gas components by pressurizing using an autoclave or the like (solvent pressurizing method); a method of precipitating conductive fine particles in an oil component such as peanut oil; Is dissolved to remove the gas component, and the oil component is cooled to around room temperature to return to the original shape of the conductive fine particles (wet back method). Among them, the heat drying method is preferred from the viewpoint of easiness of the process.

When performing the above heat drying method, heating may be performed under reduced pressure in order to further promote the removal of gas components. Although the degree of the pressure reduction is not particularly limited, the pressure may be reduced to about -0.05 to -0.1 MPa.
The heating time is not particularly limited as long as the content of the gas component can be reduced to 5 ppm or less, and is, for example, preferably 12 hours or more, and more preferably 24 hours or more. There is no particular upper limit on the heating time, but it is practically 100 hours or less from an industrial viewpoint.

When the conductive fine particles of the present invention have the metal layer or the barrier layer, it is preferable to perform the step of removing a gas component from the conductive fine particles a plurality of times. Even if the step of removing the gas component from the conductive fine particles is performed only after the formation of the solder layer, it may be difficult to sufficiently remove the gas components contained in the base fine particles, the metal layer, and the barrier layer. is there.
A method for producing conductive fine particles having a metal layer, a barrier layer, and a solder layer using resin fine particles as the base fine particles will be described below.

First, when a metal layer is formed on the surface of the resin fine particles, a nickel layer (hereinafter also referred to as a base nickel plating layer) is formed as a base plating layer on the surface of the resin fine particles by an electroless plating method.
Next, a metal layer is formed on the surface of the base nickel plating layer.
The method for forming the metal layer is not particularly limited, and examples thereof include a method using an electrolytic plating method, an electroless plating method, and the like.

Next, a step of removing a gas component (hereinafter, a “first gas component removal step”) is performed on the resin fine particles on which the base nickel plating layer and the metal layer are formed. Specifically, after filtering the plating solution and sufficiently washing with water, the obtained fine particles are subjected to a temperature of 100 to 180 ° C. and a reduced pressure of −0.05 to −0.1 MPa for 12 to 100 hours. Heat drying under the conditions is mentioned.
By the first gas component removing step, most of the gas components contained in the resin fine particles, the underlying nickel plating layer, and the metal layer can be removed.
Note that a step of removing gas components may be performed on the resin fine particles before applying the base nickel plating layer, but care must be taken since plating properties may be reduced.

When a barrier layer is formed on the surface of the metal layer after the first gas component removing step, a method of forming, for example, a nickel layer as the barrier layer is not particularly limited, and examples thereof include an electrolytic plating method and an electroless plating method. And the like.
Next, a solder layer is formed on the surface of the barrier layer to obtain conductive fine particles. The method for forming the solder layer is not particularly limited, and includes, for example, a method using an electrolytic plating method.

Next, a step of removing a gas component from the obtained conductive fine particles (hereinafter, a “second gas component removing step”) is performed. Specifically, after the plating solution is filtered and sufficiently washed with water, the obtained conductive fine particles are heated at a temperature of 100 to 180 ° C. under a reduced pressure of −0.05 to −0.1 MPa for 12 to 100 MPa. Heat drying under the condition of time is mentioned.
By the second gas component removing step, gas components remaining in the resin fine particles, the underlying nickel plating layer and the metal layer, and gas components contained in the barrier layer and the solder layer can be removed.

When a metal is adhered to the surface of the solder layer, the content of the metal adhered to the surface of the solder layer in the total of the metal contained in the solder layer and the metal adhered to the surface of the solder layer Is attached to the surface of the solder layer so that the content is 0.0001 to 5.0% by weight.
The method for attaching a metal to the surface of the solder layer is not particularly limited as long as the solder layer is not completely covered with the metal layer, and examples thereof include an electroless plating method, an electrolytic plating method, and a sputtering method. The metal may be partially attached to the surface of the solder layer by forming the solder layer and attaching the metal to the surface of the solder layer by an electroless plating method, a sputtering method, or the like. Among them, the electroless plating method is preferable because the amount of metal adhered can be controlled by appropriately setting the concentration of the plating solution, pH, reaction temperature, plating reaction time, and the like.
The metal adhering to the surface of the solder layer may partially diffuse into the solder layer.
Further, if necessary, a step of removing a gas component (hereinafter, referred to as a “third gas component removing step”) may also be performed on the conductive fine particles having a metal adhered to the surface of the solder layer. Specifically, after the plating solution is filtered and sufficiently washed with water, the obtained conductive fine particles are heated at a temperature of 100 to 180 ° C. under a reduced pressure of −0.05 to −0.1 MPa for 12 to 100 MPa. Heat drying under the condition of time is mentioned.
By the third gas component removing step, it is possible to remove gas components remaining on the resin fine particles, the underlying nickel plating layer, the metal layer, the barrier layer, the solder layer, and gas components contained in the metal adhered to the surface of the solder. it can.

An anisotropic conductive material can be produced by dispersing the conductive fine particles of the present invention in a binder resin. Such an anisotropic conductive material is also one of the present invention.
Examples of the anisotropic conductive material of the present invention include an anisotropic conductive paste, an anisotropic conductive ink, an anisotropic conductive adhesive, an anisotropic conductive film, and an anisotropic conductive sheet.

The binder resin is not particularly limited, and examples thereof include a vinyl resin, a thermoplastic resin, a curable resin, a thermoplastic block copolymer, and an elastomer.
The vinyl resin is not particularly limited, and examples thereof include a vinyl acetate resin, an acrylic resin, and a styrene resin. The thermoplastic resin is not particularly limited, and examples thereof include a polyolefin resin, an ethylene-vinyl acetate copolymer, and a polyamide resin. The curable resin is not particularly limited, and examples thereof include an epoxy resin, a urethane resin, a polyimide resin, and an unsaturated polyester resin. Although the thermoplastic block copolymer is not particularly limited, styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, styrene-butadiene-styrene block copolymer hydrogenated product, styrene-isoprene -Hydrogenated products of styrene block copolymers. These resins may be used alone or in combination of two or more.
Further, the curable resin may be any one of a room temperature curable resin, a thermosetting resin, a photocurable resin, and a moisture curable resin.

The anisotropic conductive material of the present invention may be, for example, a filler, a plasticizer, an adhesion promoter, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a coloring agent, Various additives such as a flame retardant and an organic solvent may be contained.

The method for producing the anisotropic conductive material of the present invention is not particularly limited. For example, the conductive fine particles of the present invention are added to the binder resin, uniformly mixed and dispersed, and anisotropic conductive paste, anisotropic conductive paste, And a method for producing a conductive ink, an anisotropic conductive pressure-sensitive adhesive, and the like. Further, as a method for producing the anisotropic conductive material of the present invention, the conductive fine particles of the present invention are added to the binder resin and uniformly dispersed or dissolved by heating to obtain a release paper or a release film. A method for producing an anisotropic conductive film, an anisotropic conductive sheet, etc., by coating the release material of the release material so as to have a predetermined thickness and performing drying and cooling as necessary. Can be Note that an appropriate manufacturing method can be selected according to the type of the anisotropic conductive material.
Further, the binder resin and the conductive fine particles of the present invention may be used separately as an anisotropic conductive material without being mixed.

By using the conductive fine particles or anisotropic conductive material of the present invention, a conductive connection structure can be obtained by conductively connecting the electrodes with high connection reliability.
As a method for producing a conductive connection structure using the conductive fine particles or anisotropic conductive material of the present invention, for example, first, conductive fine particles or anisotropic conductive material are formed on an electrode formed on one substrate or a semiconductor chip. The material is arranged and the solder layer is melted by reflow to perform a conductive fine particle arranging step of fixing the conductive fine particles on the electrodes. Then, the electrode formed on the other substrate or the semiconductor chip is connected to the conductive fine particles. There is a method in which an electrode of a substrate or a semiconductor chip on which conductive fine particles are arranged is opposed to each other, and a conductive connection step of electrically connecting the electrodes of the substrate or the semiconductor chip by reflow is performed.
A conductive connection structure that is conductively connected using the conductive fine particles or the anisotropic conductive material of the present invention is also one of the present invention.

ADVANTAGE OF THE INVENTION According to this invention, highly reliable electrical connection can be performed and the conductive fine particle which can manufacture a conductive connection structure with high yield can be provided. Further, it is possible to provide an anisotropic conductive material containing the conductive fine particles, and a conductive connection structure connected by the conductive fine particles or the anisotropic conductive material.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(Example 1)
(1) Preparation of Resin Fine Particles 50 parts by weight of divinylbenzene and 50 parts by weight of tetramethylolmethanetetraacrylate were copolymerized to prepare resin fine particles (average particle diameter: 180 μm, CV value: 0.56%).

(2) Preparation of conductive fine particles The obtained fine resin particles were subjected to electroless nickel plating to form a 0.3 μm-thick underlying nickel plating layer on the surfaces of the fine resin particles. Next, a 7 μm-thick copper layer was formed by subjecting the resin fine particles on which the base nickel plating layer was formed to electrolytic copper plating. After the plating solution was filtered and sufficiently washed with water, the obtained resin fine particles on which the copper layer was formed were dried by heating under the conditions of a temperature of 150 ° C. and a reduced pressure of −0.08 MPa for 12 hours (hereinafter, referred to as “hereinafter”). Also referred to as "first heat drying").

The nickel fine particles having a thickness of 0.5 μm were formed by further performing electrolytic nickel plating on the resin fine particles on which the copper layer after the first heat drying was formed. Further, by performing electroplating, a solder layer containing tin and silver having a thickness of 34 μm was formed. After the plating solution was filtered and sufficiently washed with water, the obtained resin fine particles on which the solder layer was formed were dried by heating under the conditions of a temperature of 150 ° C. and a reduced pressure of −0.08 MPa for 12 hours (hereinafter, referred to as “below”). Also referred to as “second heat drying”).
By the above method, conductive fine particles having a copper layer, a nickel layer, and a solder layer sequentially formed on the surface of the resin fine particles were obtained.

(3) Measurement of gas component in conductive fine particles 500 mg of the obtained conductive fine particles were placed in an empty thermal desorption tube, and the content of the gas component was measured under the following conditions, and it was 4.79 ppm.
Thermal desorption device: TurboMatrix 650 (PerkinElmer)
Sample heating: 260 ° C, 15 min (20 ml / min)
Secondary desorption: 350 ° C, 10 minutes
Split: Inlet 15ml / min Outlet 20ml / min Injection rate 40%
GC-MS device: JMS Q1000 (manufactured by JEOL Ltd.)
GC column: EQUITY-1 (non-polar) 0.32 mm × 60 m × 0.25 μm
GC temperature rise: 50 ° C (5 min) → 10 ° C / min → 300 ° C (10 min)
He flow rate: 1.5 ml / min
MS measurement range: 35 to 600 amu (scan 500 ms)
Ionization voltage: 70 eV
MS temperature: ion source; 230 ° C, interface; 250 ° C

(Example 2)
Conductive fine particles were obtained in the same manner as in Example 1, except that the conditions for the first heating and drying were changed to a temperature of 150 ° C. and a reduced pressure of −0.08 MPa for 72 hours.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 1.78 ppm.

(Example 3)
Conductive fine particles were obtained in the same manner as in Example 1, except that the conditions for the second heating and drying were changed to a temperature of 150 ° C. and a reduced pressure of −0.08 MPa for 72 hours.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 2.75 ppm.

(Example 4)
In the same manner as in Example 1, conductive fine particles having a copper layer, a nickel layer, and a solder layer formed sequentially on the surface of the resin fine particles were obtained.
A weight (53.8 g in this example) of the obtained conductive fine particles having a surface area of 0.223 dm ² was added to 450 mL of the following electroless nickel plating solution (solution temperature 37 ° C., pH 10.5), and the plating solution was added. Was maintained at 37 ° C. to start an electroless nickel plating reaction. Fifteen minutes after the addition of the conductive fine particles, the stirring was stopped and the electroless nickel plating solution was filtered. After the obtained particles were washed with water, they were dried with a vacuum dryer at 50 ° C. A copper layer, a nickel layer, and a solder layer were sequentially formed on the surface of the resin fine particles, and conductive fine particles having nickel adhered to the surface of the solder layer were obtained.

Electroless nickel plating solution composition Nickel acetate: 35 g / L
Hydrazine monohydrate: 50 g / L
Ethylenediaminetetraacetic acid: 20 g / L
Lactic acid: 75 g / L
Boric acid: 25 g / L

The conductive fine particles having nickel adhered to the surface of the solder layer were analyzed by a fluorescent X-ray analyzer (“EDX-800HS” manufactured by Shimadzu Corporation). The content of each metal occupied was 3.5% by weight of silver, 0.2% by weight of nickel, and the balance was tin.

For the conductive fine particles having nickel adhered to the surface of the obtained solder layer, the plating solution was filtered, washed sufficiently with water, and then heated and dried at 150 ° C. under a reduced pressure of −0.08 MPa for 12 hours. (Hereinafter, also referred to as “third heat drying”).
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 4.16 ppm.

(Comparative Example 1)
Conductive fine particles were obtained in the same manner as in Example 1 except that the conditions of the first heating and drying were changed to a temperature of 80 ° C. and a reduced pressure of −0.08 MPa for 12 hours.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 7.02 ppm.

(Comparative Example 2)
Conductive fine particles were obtained in the same manner as in Example 1, except that the conditions of the second heating and drying were changed to a temperature of 80 ° C. and a reduced pressure of −0.08 MPa for 12 hours.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 6.48 ppm.

(Comparative Example 3)
Except that the first heat drying was not performed, conductive fine particles were obtained in the same manner as in Example 1.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 8.46 ppm.

(Comparative Example 4)
Conductive fine particles were obtained in the same manner as in Example 1 except that the second heat drying was not performed.
When the content of the gas component of the obtained conductive fine particles was measured by the same method as in Example 1, it was 8.75 ppm.

(Comparative Example 5)
Conductive fine particles were obtained in the same manner as in Example 1, except that neither the first heating drying nor the second heating drying was performed.
The content of the gas component in the obtained conductive fine particles was measured by the same method as in Example 1, and it was 10.34 ppm.

(Evaluation)
The following evaluation was performed on the conductive fine particles obtained in the examples and comparative examples. The results are shown in Table 1.

(1) Mounting evaluation test A flux (“WS-9160-M7” manufactured by Cookson Electronics Co., Ltd.) was applied to electrode lands (diameter 230 μm) provided at a pitch of 0.4 mm on a silicon chip (5 mm long × 5 mm wide) at a pitch of 0.4 mm. Applied. The obtained conductive fine particles were arranged on all the electrode lands, and reflowed (heating temperature: 250 ° C., 30 seconds) to mount the conductive fine particles on the electrode lands.
For each example, 10 mounted silicon chips and a total of 1210 ball terminals were observed under a microscope, and abnormalities in shape and the presence or absence of solder scattering were checked, and evaluated according to the following criteria.
○: Abnormal shape and no solder scattering ×: Abnormal shape or solder scattering

(2) A flux ("WS-9160-M7" manufactured by Cookson Electronics Co., Ltd.) is applied to electrode lands (diameter 230 μm) provided at 121 pitches of 0.4 mm on a silicon chip (5 mm long × 5 mm wide) with a void observation. did. The obtained conductive fine particles were arranged on all the electrode lands, and reflowed (heating temperature: 250 ° C., 30 seconds) to mount the conductive fine particles on the electrode lands.
The formed ball terminal was observed with an X-ray microscope, and the presence or absence of a void inside the terminal was confirmed, and evaluated according to the following criteria.
○: No void inside ball terminal ×: Void inside ball terminal

(3) Bond strength (shear strength) test Flux ("WS-9160-" manufactured by Cookson Electronics Co., Ltd.) was applied to electrode lands (diameter 230 μm) provided at a pitch of 0.4 mm on a silicon chip (5 mm long × 5 mm wide) at a pitch of 0.4 mm. M7 "). The obtained conductive fine particles were arranged on all the electrode lands, and reflowed (heating temperature: 250 ° C., 30 seconds) to mount the conductive fine particles on the electrode lands.
The shear strength test of the formed ball terminals was performed for each of the 20 terminals in each example, and the arithmetic average strength was obtained. The conditions of the shear strength test are as follows.
Apparatus: Bond tester 4000 (manufactured by Dage)
Mode: Shear strength measurement mode Share speed: 300 μm / sec
Shear height: 30 μm

(4) Temperature cycle test A flux (“WS-9160-M7” manufactured by Cookson Electronics Co., Ltd.) was applied to electrode lands (diameter 230 μm) provided at 121 pitches of 0.4 mm on a silicon chip (5 mm long × 5 mm wide). Applied. The obtained conductive fine particles were arranged on all the electrode lands, and reflowed (heating temperature: 250 ° C., 30 seconds) to mount the conductive fine particles on the electrode lands.
Next, a solder paste (“M705-GRN360-K2-V” manufactured by Senju Metal Industry Co., Ltd.) was applied (screen printed) on a printed circuit board (77 mm long × 132 mm wide). The chip on which the conductive fine particles were mounted was mounted on each substrate and reflowed (heating temperature: 250 ° C., 30 seconds), and 15 chips were mounted on a printed circuit board to obtain a conductive connection structure.
Since the obtained conductive connection structure has a daisy-chain circuit, it can detect even a disconnection of one electrode land.
Using the obtained conductive connection structure, a temperature cycle test was performed with -40 ° C to 125 ° C as one cycle. The heat profile of the temperature cycle test was held at -40 ° C for 10 minutes, heated from -40 ° C to 125 ° C for 2 minutes, held at 125 ° C for 10 minutes, and then changed from 125 ° C to -40 ° C for 2 minutes. It was a profile to lower the temperature.
The number of cycles at which 15 chips were disconnected was measured, and the arithmetic average was calculated.

(5) Flux ("WS-9160-M7" manufactured by Cookson Electronics Co., Ltd.) is applied to 121 electrode lands (diameter 230 μm) provided at a pitch of 0.4 mm on a silicon chip (5 mm long × 5 mm wide) at a pitch of 0.4 mm. did. The obtained conductive fine particles were arranged on all the electrode lands, and reflowed (heating temperature: 250 ° C., 30 seconds) to mount the conductive fine particles on the electrode lands.
Next, a solder paste (“M705-GRN360-K2-V” manufactured by Senju Metal Industry Co., Ltd.) was applied (screen printed) on a printed circuit board (77 mm long × 132 mm wide). The chip on which the conductive fine particles were mounted was mounted on each substrate and reflowed (heating temperature: 250 ° C., 30 seconds), and 15 chips were mounted on a printed circuit board to obtain a conductive connection structure.
Since the obtained conductive connection structure has a daisy-chain circuit, it can detect even a disconnection of one electrode land.
In accordance with JEDEC standard JESD22-B111, a drop strength test of the obtained conductive connection structure was performed.
The number of drops at which ten chips were disconnected was measured, and the arithmetic average was calculated.

ADVANTAGE OF THE INVENTION According to this invention, highly reliable electrical connection can be performed and the conductive fine particle which can manufacture a conductive connection structure with high yield can be provided. Further, it is possible to provide an anisotropic conductive material containing the conductive fine particles, and a conductive connection structure connected by the conductive fine particles or the anisotropic conductive material.

Claims (5)

Conductive fine particles having a base fine particle having an average particle size of 380 μm or less and a solder layer formed on the surface of the base fine particle, and heating the sample to 300 ° C. by a thermal desorption GC-MS method. The content of the gas component measured under the conditions is 5 ppm or less,
The substrate fine particles are resin fine particles,
Further comprising a metal layer between the resin fine particles and the solder layer,
Between the metal layer and the solder layer, further the conductive fine particles you further comprising a barrier layer. The surface of the solder layer, nickel, cobalt, iron, manganese, titanium, conductive fine particles according to claim 1, wherein the phosphorus or bismuth is attached. An anisotropic conductive material, wherein the conductive fine particles according to claim 1 or 2 are dispersed in a binder resin. A conductive connection structure which is conductively connected using the conductive fine particles according to claim 1 . A conductive connection structure which is conductively connected using the anisotropic conductive material according to claim 3 .