CN110603612A - Conductive particle, method for producing conductive particle, conductive material, and connection structure - Google Patents

Conductive particle, method for producing conductive particle, conductive material, and connection structure Download PDF

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Publication number
CN110603612A
CN110603612A CN201880030129.3A CN201880030129A CN110603612A CN 110603612 A CN110603612 A CN 110603612A CN 201880030129 A CN201880030129 A CN 201880030129A CN 110603612 A CN110603612 A CN 110603612A
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Prior art keywords
conductive
particles
conductive portion
particle
conductive particles
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CN201880030129.3A
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CN110603612B (en
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大秦嘉代
真原茂雄
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Sekisui Chemical Co Ltd
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Sekisui Chemical Co Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/18—Layered products comprising a layer of synthetic resin characterised by the use of special additives
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K3/00—Use of inorganic substances as compounding ingredients
    • C08K3/02—Elements
    • C08K3/08—Metals
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K9/00—Use of pretreated ingredients
    • C08K9/12—Adsorbed ingredients, e.g. ingredients on carriers
    • 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
    • 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
    • H01B1/02—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of metals or alloys
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B13/00—Apparatus or processes specially adapted for manufacturing conductors or cables
    • H01B13/0026—Apparatus for manufacturing conducting or semi-conducting layers, e.g. deposition of metal
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
    • H01B5/00—Non-insulated conductors or conductive bodies characterised by their form
    • H01B5/14—Non-insulated conductors or conductive bodies characterised by their form comprising conductive layers or films on insulating-supports
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
    • H01R11/00—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts
    • H01R11/01—Individual connecting elements providing two or more spaced connecting locations for conductive members which are, or may be, thereby interconnected, e.g. end pieces for wires or cables supported by the wire or cable and having means for facilitating electrical connection to some other wire, terminal, or conductive member, blocks of binding posts characterised by the form or arrangement of the conductive interconnection between the connecting locations
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
    • C08K2201/00—Specific properties of additives
    • C08K2201/001—Conductive additives

Abstract

The present invention provides a method for effectively improving the conduction reliability between electrodes, which comprisesConductive particles which effectively prevent cracking of a conductive portion due to external impact. The conductive particle of the present invention comprises: a substrate particle, a first conductive part disposed on a surface of the substrate particle, and a second conductive part disposed on an outer surface of the first conductive part, wherein when the outer surface of the second conductive part is observed by an electron microscope, no pinhole having a size of 50nm or more in a maximum length direction exists, or 1 pinhole/μm exists2The size in the maximum length direction of the pinhole is 50nm or more.

Description

Conductive particle, method for producing conductive particle, conductive material, and connection structure
Technical Field
The present invention relates to conductive particles for electrically connecting electrodes, for example. The present invention also relates to a method for producing the conductive particles, a conductive material using the conductive particles, and a connection structure.
Background
Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are well known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin. As the conductive particles, conductive particles having a surface of a conductive layer subjected to an insulating treatment can be used.
The anisotropic conductive material is used to obtain various connection structures. As the connection through the anisotropic conductive material, for example, there are listed: connection between a flexible printed board and a glass substrate (fog), (film on glass)), connection between a semiconductor chip and a flexible printed board (cof), (chip on film), connection between a semiconductor chip and a glass substrate (cog), (chip on glass), connection between a flexible printed board and a glass epoxy substrate (fob), (film on board), and the like.
As an example of the conductive particles, patent document 1 below discloses conductive particles including base particles and a conductive metal layer covering the surface of the base particles. The substrate particles are polymer particles having a glass transition temperature (Tg) of 50 ℃ or higher and 100 ℃ or lower. The thickness of the conductive metal layer is 0.01-0.15 μm.
Documents of the prior art
Patent document
Patent document 1: japanese unexamined patent publication No. 2012 and 064559
Disclosure of Invention
Technical problem to be solved by the invention
In recent years, with the development of various electronic devices, substrate materials have been diversified. For example, curved panels, freely bendable flexible panels, and the like have been developed. Since the curved panel or the like requires flexibility, it is being discussed that a plastic substrate such as a polyimide substrate is used instead of the conventional glass substrate as a flexible member for the curved panel or the like.
When a semiconductor chip or the like is directly mounted on a plastic substrate, the plastic substrate is easily deformed or broken by the temperature or pressure at the time of mounting, and therefore, it is necessary to keep the temperature or pressure at the time of mounting as low as possible. When the temperature or pressure at the time of mounting is lowered, the conductive particles cannot be sufficiently deformed at the time of conductive connection between the electrodes. As a result, it may be difficult to sufficiently secure a contact area between the conductive particles and the electrode. Further, a force for restoring the compressed conductive particles to their original shape acts, and a phenomenon called springback may occur. When the spring back occurs, it may be difficult to maintain a sufficient contact area between the conductive particles and the electrode. As a result, the reliability of conduction between the electrodes may be reduced.
Further, by using the conventional conductive particles described in patent document 1, high connection reliability can be exhibited to some extent even when the temperature or pressure at the time of mounting is low. However, since the base material particles are relatively soft, the conductive particles are likely to cause cracking of the conductive metal layer (cracking of the conductive portion) by external impact. With conventional conductive particles, it is difficult to prevent cracking of the conductive portion due to external impact.
The invention provides conductive particles which can effectively improve the conduction reliability between electrodes and can effectively prevent the conductive part from cracking caused by external impact. The present invention also provides a method for producing the conductive particles, a conductive material using the conductive particles, and a connection structure.
Means for solving the problems
According to a broad aspect of the present invention, there is provided a conductive particle comprising: a substrate particle, a first conductive part disposed on a surface of the substrate particle, and a second conductive part disposed on an outer surface of the first conductive part, wherein when the outer surface of the second conductive part is observed by an electron microscope, no pinhole having a size of 50nm or more in a maximum length direction exists, or 1 pinhole/μm exists2The size in the maximum length direction of the pinhole is 50nm or more.
According to a broad aspect of the present invention, there is provided a conductive particle comprising: a substrate particle, a first conductive part disposed on a surface of the substrate particle, and a second conductive part disposed on an outer surface of the first conductive part, wherein when the outer surface of the second conductive part is observed by an electron microscope, no pinhole having a size of 50nm or more in a maximum length direction exists, or 1 pinhole/μm exists2The size in the maximum length direction of the pinhole is 50nm to 200 nm.
According to a specific aspect of the conductive particles according to the present invention, the conductive particles satisfy the following formula (1) and have a compression recovery rate at 25 ℃ of 10% or less,
a is less than or equal to 5500-B is multiplied by 100 … formula (1)
In the formula (1), A is 10% K value (N/mm) of the conductive particles2) And B is the average particle diameter (μm) of the conductive particles.
According to a specific aspect of the conductive particles of the present invention, the average particle diameter is 3 μm or more and 30 μm or less.
According to a specific aspect of the conductive particle of the present invention, wherein the second conductive portion includes gold, silver, palladium, platinum, copper, cobalt, ruthenium, indium, or tin.
According to a specific aspect of the conductive particle of the present invention, wherein an ionization tendency of the metal contained in the first conductive portion is larger than an ionization tendency of the metal contained in the second conductive portion.
According to a specific aspect of the conductive particles, wherein the first conductive portion contains nickel and phosphorus.
According to a specific aspect of the conductive particle of the present invention, wherein a phosphorus content on the second conductive portion side in the first conductive portion is larger than a phosphorus content on the base material particle side in the first conductive portion in a thickness direction in the first conductive portion.
According to a broad aspect of the present invention, there is provided a method for producing conductive particles, comprising the steps of: and a step of forming a second conductive part by using conductive particles including base material particles and a first conductive part provided on the surface of the base material particles and applying a plating treatment to the outer surface of the first conductive part, wherein the second conductive part is formed so that no pin hole having a size of 50nm or more in the maximum length direction is present or 1/μm is present when the outer surface of the second conductive part is observed with an electron microscope2The size in the maximum length direction of the pinhole is 50nm or more.
According to a broad aspect of the present invention, there is provided an electrically conductive material comprising: the conductive particles and the binder resin.
According to a broad aspect of the present invention, there is provided a connection structure comprising: the present invention provides a connector including a first member to be connected having a first electrode on a surface thereof, a second member to be connected having a second electrode on a surface thereof, and a connecting portion for connecting the first member to be connected and the second member to be connected, wherein the connecting portion is made of the conductive particles or a conductive material containing the conductive particles and a binder resin, and the first electrode and the second electrode are electrically connected by the conductive particles.
Effects of the invention
The present invention provides a conductive particle, comprising: a base material particle, a first conductive part provided on a surface of the base material particle, and a second conductive part provided on an outer surface of the first conductive part, wherein when the outer surface of the second conductive part is observed with an electron microscope, no pinhole having a size of 50nm or more in a maximum length direction exists, or 1 piece/μm exists2Maximum ofA pinhole having a dimension of 50nm or more in the longitudinal direction. The conductive particles of the present invention have the above-described technical features, and thus can effectively improve the reliability of conduction between electrodes and effectively prevent breakage of a conductive portion due to external impact.
The conductive particle of the present invention comprises: a base material particle, a first conductive part provided on a surface of the base material particle, and a second conductive part provided on an outer surface of the first conductive part, wherein when the outer surface of the second conductive part is observed with an electron microscope, no pinhole having a size of 50nm or more in a maximum length direction exists, or 1 piece/μm exists2The size in the maximum length direction of the pinhole is 50nm to 200 nm. The method for producing conductive particles of the present invention has the above-described features, and therefore, the reliability of conduction between electrodes can be effectively improved, and breakage of a conductive portion due to external impact can be effectively prevented.
The method for producing conductive particles of the present invention comprises the steps of: and a step of forming a second conductive part by using conductive particles including base material particles and a first conductive part provided on the surface of the base material particles and applying a plating treatment to the outer surface of the first conductive part, wherein the second conductive part is formed so that no pin hole having a size of 50nm or more in the maximum length direction exists or 1 piece/μm exists when the outer surface of the second conductive part is observed with an electron microscope2The size in the maximum length direction of the pinhole is 50nm or more. The method for producing conductive particles of the present invention, which has the above-described technical features, can effectively improve the reliability of conduction between electrodes and can effectively prevent breakage of a conductive portion due to external impact.
Drawings
Fig. 1 is a sectional view showing conductive particles according to a first embodiment of the present invention;
fig. 2 is a sectional view showing conductive particles according to a second embodiment of the present invention;
fig. 3 is a sectional view schematically showing a connection structure using conductive particles according to a first embodiment of the present invention;
fig. 4 is a view showing an image of the surface of the conductive particle produced in example 1;
fig. 5 is a view showing an image of the surface of the conductive particle produced in comparative example 1;
Detailed Description
Hereinafter, specific embodiments of the present invention will be described in detail.
(conductive particles)
The present invention provides a conductive particle, comprising: the substrate includes a substrate particle, a first conductive portion disposed on a surface of the substrate particle, and a second conductive portion disposed on an outer surface of the first conductive portion. In the conductive particle of the present invention, it is preferable that when the outer surface of the second conductive part is observed with an electron microscope, no pinhole having a size of 50nm or more in the maximum length direction exists, or 1 particle/μm exists2The size in the maximum length direction of the pinhole is 50nm or more. In this case, the conductive particles of the present invention, when the pinholes are present, are calculated to be 1 μm2The number of the pinholes is 1 or less. In the conductive particle of the present invention, the calculated maximum length of the pinhole in the longitudinal direction is 50nm or more. In this case, the conductive particles of the present invention are calculated to be 1 μm per each pinhole2The number of the pinholes is 1 or less. In the conductive particle of the present invention, the calculated size of the pinhole in the maximum length direction is 50nm or more.
In the conductive particles of the present invention, when the outer surface of the second conductive part is observed with an electron microscope, it is preferable that no pinhole having a size of 50nm or more in the maximum length direction is present or 1/μm is present2The size in the maximum length direction of the pinhole is 50nm to 200 nm. In this case, the conductive particles of the present invention were calculated to have a particle size of 1 μm2The number of the pinholes is 1 or less. In the conductive particle of the present invention, the calculated size of the pinhole in the maximum length direction is 50nm to 200 nm.
The present invention has the above technical features, and thus can effectively improve the reliability of conduction between electrodes and effectively prevent breakage of a conductive portion due to external impact.
Even under conditions of low temperature and low pressure during mounting, a connection structure having high connection reliability is obtained, and it is necessary to use conductive particles having relatively soft base material particles. However, conductive particles having relatively soft base material particles are prone to breakage of the conductive portion due to external impact. The inventors of the present invention have intensively studied to suppress the breakage of the conductive portion due to the external impact, and as a result, found that the breakage of the conductive portion due to the external impact is caused by a pinhole generated by the displacement plating treatment of the conductive portion for forming the conductive particles. The present inventors have found that, in conductive particles using base particles having relatively flexibility, cracking of a conductive portion due to external impact occurs from pinholes. The present invention has the above technical features, and thus can effectively prevent the breakage of the conductive part due to external impact.
For example, the pin hole is formed by elution of nickel ions when the second conductive portion is formed by displacement plating on the surface of the first conductive portion formed by nickel plating. For example, when the metal in the first conductive portion is eluted, the missing portion of the first conductive portion is a pinhole.
In the conductive particle of the present invention, when the outer surface of the second conductive part is observed with an electron microscope, it is preferable that no pinhole having a size of 50nm or more in the maximum length direction is present.
In the conductive particle of the present invention, when the outer surface of the second conductive part is observed using an electron microscope, the number of pinholes is 1 piece/μm2The size in the maximum length direction of the pinhole is 50nm or more. When the outer surface of the second conductive part is observed using an electron microscope, the number of the conductive parts is preferably 1/μm2The size in the maximum length direction of the pinhole is 50nm or more. When the number of the pinholes is within the preferable range, the reliability of conduction between the electrodes can be further effectively improved, and the number of the pinholes can be further increasedThe breakage of the conductive portion due to external impact is effectively prevented.
In the conductive particles of the present invention, it is preferable that no pinholes having a size of 50nm to 200nm in the maximum length direction are present when the outer surface of the second conductive part is observed with an electron microscope.
In the conductive particle of the present invention, when the outer surface of the second conductive part is observed using an electron microscope, the number of pinholes is 1 piece/μm2The size in the maximum length direction of the pinhole is 50nm to 200 nm. From the viewpoint of further effectively improving the reliability of conduction between electrodes and from the viewpoint of further effectively preventing breakage of the conductive portion due to external impact, the size of the pinhole in the maximum length direction, the size of which is 50nm or more in the maximum length direction, is preferably 150nm or less, and more preferably 100nm or less. When the outer surface of the second conductive part is observed with an electron microscope, the number of pinholes having a dimension of 50nm to 200nm in the maximum length direction is preferably 0.1 pinhole/μm2The following exist. When the number of the pinholes is within the above preferable range, the reliability of the conduction between the electrodes can be further effectively improved, and the breakage of the conductive portion due to external impact can be further effectively prevented.
The presence or absence of the pinhole can be confirmed by observing an arbitrary conductive particle with an electron microscope, for example. Specifically, the presence or absence of the pinhole can be confirmed by observing any five positions of any conductive particle except for a portion of 0.5 μm inward from the outer periphery thereof with an electron microscope.
For example, the size in the maximum length direction of the pinhole may be calculated by observing any conductive particle with an electron microscope. The dimension of the pinhole in the maximum length direction is a distance obtained by connecting two points on the outer circumference of the pinhole in a straight line, and is a dimension obtained by connecting two points on the outer circumference of the pinhole in a straight line at the maximum distance.
The shape of the pinhole is not particularly limited. The shape of the pinhole may be circular or may be other than circular. When the shape of the pinhole is a circle, the size of the pinhole in the maximum length direction corresponds to the maximum diameter.
Generally, when the conductive portion is formed by electroless plating or the like, a minute region where the conductive portion is not formed may be formed. The longest length dimension of this region is typically less than 50nm and in the present invention these small regions are not included in the pinholes.
From the viewpoint of further effectively improving the conduction reliability between the electrodes, the conductive particles preferably satisfy the relationship of the following formula (1).
A is less than or equal to 5500-B is multiplied by 100 … formula (1)
In the formula (1), A is 10% K value (N/mm) of the conductive particles2) And B is the average particle diameter (μm) of the conductive particles.
From the viewpoint of further improving the reliability of conduction between electrodes, the 10% K value of the conductive particles is preferably 500N/mm2Above, more preferably 1000N/mm2Above, and preferably 4500N/mm2Below, more preferably 4000N/mm2The following.
The 10% K value (compressive modulus when the conductive particles are compressed by 10%) of the conductive particles can be measured as follows.
One conductive particle was compressed with a smooth indenter end face of a cylinder (diameter 100 μm, made of diamond) under a pressure velocity of 0.33mN/s and a maximum test load of 20mN using a micro compression tester. The load value (N) and the compression displacement (mm) at this time were measured. From the obtained measurement values, the 10% K value (10% compressive modulus) at 25 ℃ can be determined by the following equation. As the micro-compression tester, for example, "micro-compression tester MCT-W200" manufactured by Shimadzu corporation and "Fisher Scope H-100" manufactured by Fisher corporation can be used. The 10% K value of the conductive particles at 25 ℃ is preferably calculated by averaging 10% K values of arbitrarily selected 50 conductive particles at 25 ℃.
10% K value (N/mm)2)＝(3/21/2)·F·S-3/2·R-1/2
F: load value (N) when conductive particles are compressed and deformed by 10%
S: compression displacement (mm) when conductive particles are compressed and deformed by 10%
R: radius of conductive particle (mm)
The K value generally and quantitatively represents the hardness of the conductive particles. By using the K value, the hardness of the conductive particles can be quantitatively and uniquely expressed.
From the viewpoint of further improving the reliability of conduction between electrodes, the conductive particles preferably have a compression recovery rate at 25 ℃ of 10% or less, more preferably 8% or less. The lower limit of the compression recovery rate of the conductive particles at 25 ℃ is not particularly limited. The conductive particles may have a compression recovery rate of 3% or more at 25 ℃.
The compression recovery rate of the conductive particles at 25 ℃ can be measured as follows.
Conductive particles are scattered on a sample stage. For one dispersed conductive particle, a load (reverse load value) was applied to 50mN in the case of a particle diameter of 10 μm or more and a load (reverse load value) was applied to 10mN in the case of a particle diameter of less than 10 μm at 25 ℃ with a smooth indenter end face (diameter 100 μm, made of diamond) of a cylinder using a micro compression tester. Then, the load was released to the original load value (0.40 mN). The load-compression displacement during this period can be measured, and the compression recovery rate at 25 ℃ can be determined according to the following equation. The load rate was 0.33 mN/sec. As the micro-compression tester, for example, "micro-compression tester MCT-W200" manufactured by Shimadzu corporation, "Fisher Scope H-100" manufactured by Fisher corporation, and the like can be used.
Compression recovery rate (%) [ L2/L1] x 100
L1: compressive displacement from an origin load value to a rebound load value upon application of a load
L2: load-shedding displacement from rebound load value to origin load value upon load release
Since the conductive particles have the compressive property, the conductive particles can be suitably used for conductive connection use of a bent portion. The conductive particles are effective in exhibiting particularly excellent conduction reliability when used for conductive connection in a bent portion.
The conductive particles have the compressive property, and therefore are preferably used for conductive connection of an electrode of a flexible member, and more preferably for use in conductive connection of an electrode of a flexible member in a bent state. By using the conductive particles, the flexible member can be used in a bent state and exhibits high conduction reliability.
As a connection structure using a flexible member, a flexible panel and the like can be cited. The flexible panel may be used as a curved panel. The conductive particles are preferably used for forming a connecting portion of a flexible panel, and are preferably used for forming a connecting portion of a curved panel.
The conductive particles preferably have an average particle diameter of 3 μm or more, more preferably 5 μm or more, further preferably 7 μm or more, particularly preferably 10 μm or more, preferably 1000 μm or less, more preferably 100 μm or less, further preferably 30 μm or less, particularly preferably 25 μm or less, and most preferably 20 μm or less. When the average particle diameter of the conductive particles is 3 μm or more and 30 μm or less, the conductive particles can be preferably used for conductive connection. When the average particle diameter of the conductive particles is not less than the lower limit and not more than the upper limit, the connection resistance between the electrodes can be further effectively reduced, and the conduction reliability between the electrodes can be further effectively improved.
The average particle diameter of the conductive particles is more preferably a number average particle diameter. The average particle diameter of the conductive particles may be determined by calculating an average value of, for example, 50 arbitrary conductive particles observed by an electron microscope or an optical microscope; or by performing a plurality of measurements using a laser diffraction particle size distribution measuring apparatus and calculating the average value of the measurement results.
The coefficient of variation in the particle diameter of the conductive particles is preferably as low as possible, but is usually 0.1% or more, preferably 10% or less, more preferably 8% or less, and still more preferably 5% or less. When the coefficient of variation of the particle diameter of the conductive particles is not less than the lower limit and not more than the upper limit, the conduction reliability can be further improved. Wherein a coefficient of variation of the particle diameter of the conductive particles may be less than 5%.
The coefficient of variation (CV value) can be measured as follows.
CV value (%) - (ρ/Dn) × 100
ρ: standard deviation of particle diameter of conductive particle
Dn: average particle diameter of conductive particles
The shape of the conductive particles is not particularly limited. The shape of the conductive particles may be spherical or other than spherical, such as flat.
Next, a specific embodiment of the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments, and the following embodiments may be appropriately modified or improved within a range not to impair the features of the present invention. In the drawings referred to, the actual size, thickness, and the like are appropriately changed for convenience of explanation.
Fig. 1 is a sectional view showing conductive particles according to a first embodiment of the present invention;
the conductive particle 1 shown in fig. 1 includes a base particle 2, a first conductive part 3, and a second conductive part 4. The first conductive part 3 is provided on the surface of the base particle 2. The second conductive part 4 is disposed on the surface of the first conductive part 3. The first conductive part 3 is provided between the base particle 2 and the second conductive part 4. The first conductive part 3 is in contact with the surface of the base particle 2. The first conductive part 3 covers the surface of the base particle 2. The second conductive part 4 is in contact with the surface of the first conductive part 3. The second conductive part 4 covers the surface of the first conductive part 3. The conductive particles 1 are coated particles formed by coating the surface of the base material particles 2 with the first conductive part 3 and the second conductive part 4. The second conductive part 4 is located on the outermost surface of the conductive part and is the outermost layer. The conductive particles 1 have a plurality of conductive portions formed therein.
The existence state of the pinholes in the conductive particle 1 shown in fig. 1 satisfies the technical characteristics.
In the conductive particles 1, the first conductive part 3 covers the entire surface of the base material particle 2 to form a conductive layer. The first conductive portion may cover the entire surface of the base material particle, and may not cover the entire surface of the base material particle. The first conductive portion may be a conductive layer covering the entire surface of the base material particle, or may be a conductive layer covering the entire surface of the base material particle. The first conductive portion may be a conductive layer. The conductive particles may have a region where the substrate particles are not covered with the first conductive portion.
In the conductive particles 1, the second conductive part 4 covers the entire surface of the first conductive part 3 to form a conductive layer. The second conductive portion may or may not cover the entire surface of the first conductive portion. The second conductive portion may be a conductive layer that covers the entire surface of the first conductive portion, or may be a conductive layer that does not cover the entire surface of the first conductive portion. The second conductive portion may be a conductive layer. The conductive particles may include a region where the first conductive portion is not covered with the second conductive portion.
The conductive particles 1 do not include a core material. The conductive particles 1 do not have protrusions on the outer surface of the conductive portion. The conductive particles 1 are spherical. The first conductive part 3 and the second conductive part 4 have no protrusion on the outer surfaces. As described above, the conductive particles of the present invention may have no protrusions or may be spherical on the surface of the conductive portion. The conductive particles 1 do not have an insulating material. The conductive particles 1 may have an insulating material provided on the outer surface of the second conductive part 4.
In the conductive particle 1, the first conductive part 3 is directly laminated on the surface of the base particle 2. The conductive particles may have another conductive portion provided between the base material particles and the first conductive portion. The conductive particles may be provided on the surface of the base material particle with the first conductive portion provided by another conductive portion.
Fig. 2 is a sectional view showing conductive particles according to a second embodiment of the present invention.
The conductive particles 21 shown in fig. 2 include base particles 2, a first conductive portion 22, a second conductive portion 23, a plurality of core materials 24, and an insulating material 25. The first conductive part 22 is provided on the surface of the base particle 2. The second conductive portion 23 is disposed on the surface of the first conductive portion 22. The plurality of core materials 24 are disposed on the surface of the substrate particle 2. The first conductive part 22 and the second conductive part 23 cover the base material particle 2 and the plurality of core materials 24. The conductive particles 21 are coated particles in which the surfaces of the base particles 2 and the core material 24 are coated with the first conductive portion 22 and the second conductive portion 23.
The conductive particles 21 have a plurality of protrusions 21a on the outer surface of the conductive portion. The first conductive portion 22 and the second conductive portion 23 have a plurality of protrusions 22a and 23a on the outer surfaces thereof. The plurality of core materials 24 are embedded in the first conductive portion 22 and the second conductive portion 23. The core material 24 is provided inside the protrusions 21a, 22a, and 23a. The outer surfaces of first conductive portion 22 and second conductive portion 23 are raised by a plurality of core materials 24, forming protrusions 21a, 22a, and 23a. As described above, the conductive particles may have protrusions on the outer surface of the conductive portion. The conductive particles may have a protrusion on an outer surface of the second conductive portion and a protrusion on an outer surface of the first conductive portion. The conductive particles may include a plurality of core materials for raising the surface of the second conductive portion inside or outside the second conductive portion so as to form a plurality of protrusions. The core material may be located inside the first conductive part, or outside the first conductive part.
The conductive particles 21 use a plurality of core materials 24 to form the protrusions 21a, 22a, and 23a. The conductive particles may be used to form the protrusions without using a plurality of the core substances. The conductive particles may not have a plurality of the core substances.
The conductive particles 21 have an insulating material 25 provided on the outer surface of the second conductive portion 23. At least a partial region of the outer surface of the second conductive portion 23 is covered with an insulating material 25. The insulating material 25 is made of an insulating material and is insulating particles. As described above, the conductive particles may have an insulating material provided on the outer surface of the conductive portion. The conductive particles may not necessarily have an insulating substance.
Other details of the conductive particles will be described in detail below. In the following description, "(meth) acrylic acid" means either or both of "acrylic acid" and "methacrylic acid", and "(meth) acrylate" means either or both of "acrylate" and "methacrylate". .
(substrate particles)
Examples of the base particles include resin particles, inorganic particles other than metal particles, organic-inorganic hybrid particles, and metal particles. The base material particles are preferably base material particles other than metal particles, and more preferably resin particles, inorganic particles other than metal particles, or organic-inorganic hybrid particles. The substrate particles may be core-shell particles having a core and a shell disposed on a surface of the core.
The base material particles are more preferably resin particles or organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles. By using these preferable base material particles, the effects of the present invention can be more effectively exhibited, and conductive particles more suitable for electrical connection between electrodes can be obtained.
In the case of connecting electrodes using the conductive particles, the conductive particles are provided between the electrodes, and then the conductive particles are compressed by pressure bonding. When the base particles are resin particles or organic-inorganic hybrid particles, the conductive particles are easily deformed at the time of the pressure bonding, and the contact area between the conductive particles and the electrode is increased. Therefore, the reliability of conduction between the electrodes is further improved.
As a material of the resin particles, various resins are suitably used. Examples of the material of the resin particles include: polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene terephthalate, polycarbonate, polyamide, phenol resin, melamine-formaldehyde resin, benzoguanamine-formaldehyde resin, urea-formaldehyde resin, phenol resin, melamine resin, benzoguanamine resin, urea resin, epoxy resin, unsaturated polyester resin, saturated polyester resin, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyamideimide, polyether ether ketone, polyether sulfone, and a polymer obtained by polymerizing one or two or more kinds of polymerizable monomers having an ethylenically unsaturated group.
Since resin particles having physical properties suitable for arbitrary compression of the conductive material can be designed and synthesized, and the hardness of the base material particles can be easily controlled within a suitable range, the material of the resin particles is preferably a polymer obtained by polymerizing one or more polymerizable monomers having an ethylenically unsaturated group.
When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, a non-crosslinkable monomer and a crosslinkable monomer can be used as the polymerizable monomer having an ethylenically unsaturated group.
Examples of the non-crosslinking monomer include: styrene monomers such as styrene and alpha-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; alkyl (meth) acrylate compounds such as methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, and isobornyl (meth) acrylate; oxygen atom-containing (meth) acrylate compounds such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate and glycidyl (meth) acrylate; nitrile-containing monomers such as (meth) acrylonitrile; vinyl acid ester compounds such as vinyl acetate, vinyl butyrate, vinyl laurate and vinyl stearate; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene; halogen-containing monomers such as trifluoromethyl (meth) acrylate, pentafluoroethyl (meth) acrylate, vinyl chloride, vinyl fluoride and chlorostyrene.
Examples of the crosslinkable monomer include: polyfunctional (meth) acrylate compounds such as tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, glycerol tri (meth) acrylate, glycerol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, (poly) tetramethylene glycol di (meth) acrylate, and 1, 4-butanediol di (meth) acrylate; and silane-containing monomers such as triaryl (iso) cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ - (meth) acryloyloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.
The resin particles can be obtained by polymerizing the polymerizable monomer having the ethylenically unsaturated group by a known method. As the method, a suspension polymerization method in the presence of a radical polymerization initiator; a method of swelling a non-crosslinked seed particle with a radical polymerization initiator and polymerizing a monomer.
When the base particles are inorganic particles excluding metal particles or organic-inorganic hybrid particles, examples of the inorganic substance as a material of the base particles include: silica, alumina, barium titanate, zirconia, carbon black, and the like. The inorganic substance is preferably a non-metal. The particles formed of the silica are not particularly limited, and include, for example, particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then, if necessary, firing the crosslinked polymer particles. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed by crosslinking an alkoxysilyl polymer and an acrylic resin.
The organic-inorganic hybrid particles are preferably core-shell type organic-inorganic hybrid particles having a core and a shell disposed on the surface of the core. The core is preferably an organic core. The shell is preferably a mineral shell. From the viewpoint of further effectively reducing the connection resistance between the electrodes, the substrate particles are preferably organic-inorganic hybrid particles having an organic core and an inorganic shell disposed on the surface of the organic core.
Examples of the material of the organic core include the material of the resin particles.
As the material of the inorganic shell, inorganic substances listed as the material of the base particles can be cited. The material of the inorganic shell is preferably silica. The inorganic shell is preferably formed by forming a metal alkoxide in the shell by a sol-gel method on the surface of the core, and then firing the shell. The metal alkoxide is preferably a silanolate. The inorganic shell is preferably formed from a silanolate.
When the base particles are metal particles, examples of the metal particle material include: silver, copper, nickel, silicon, gold, titanium, and the like. Among them, the base material particles are preferably non-metal particles.
The particle diameter of the base material particles is preferably 1 μm or more, more preferably 2 μm or more, still more preferably 2.5 μm or more, particularly preferably 3 μm or more, preferably 1000 μm or less, more preferably 100 μm or less, further preferably 30 μm or less, and particularly preferably 5 μm or less. When the particle diameter of the base material particles is not less than the upper limit or not less than the lower limit, the contact area between the conductive particles and the electrode becomes large, the conduction reliability between the electrodes is further improved, and the connection resistance between the connection electrodes can be further effectively reduced. Further, when the conductive portion is formed on the surface of the base material particle, the conductive portion is less likely to aggregate, and aggregated conductive particles are less likely to be formed. When the particle diameter of the base material particles is not more than the upper limit, the conductive particles are easily sufficiently compressed, and the connection resistance between electrodes connected via the conductive particles can be further effectively reduced. In addition, even if the distance between the electrodes is reduced and the thickness of the conductive portion is increased, small conductive particles can be obtained.
The particle diameter of the base material particle indicates the diameter when the base material particle is in a regular spherical shape, and indicates the maximum diameter when the base material particle is in a non-regular spherical shape.
The particle size of the base material particle represents a number average particle size. The particle size of the base material particles can be determined using a particle size distribution measuring apparatus or the like. The particle size of the base material particles is preferably determined by observing 50 arbitrary base material particles with an electron microscope or an optical microscope and calculating the average value. In the case of measuring the particle diameter of the base material particle in the conductive particle, the measurement can be performed as follows.
Conductive particles were added and dispersed in "Technobit 4000" manufactured by Kulzer corporation so that the content of the conductive particles was 30% by weight, and a embedding resin for conductive particle inspection was prepared. A cross section of the conductive particles was cut using an ion milling apparatus ("IM 4000" manufactured by HitachiHigh-Technologies Corporation) so that the cross section passed near the center of the conductive particles dispersed in the embedding resin for inspection. Then, the image magnification was set to 25000 times using a field emission scanning electron microscope (FE-SEM), and 50 conductive particles were randomly selected, and the base particles of each conductive particle were observed. The particle diameter of the base material particle in each conductive particle was measured, and the average was taken as the particle diameter of the base material particle.
(first conductive part and second conductive part)
The conductive particles have a first conductive portion. The metal as a material of the first conductive portion is not particularly limited. As the metal, there may be mentioned: gold, silver, palladium, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, and the like, and alloys thereof, and the like. Further, examples of the metal include tin-doped indium oxide (ITO) and solder. The metal used as the material of the first conductive portion may be used alone or in combination of two or more.
From the viewpoint of further effectively improving the conduction reliability between the electrodes, the metal as the material of the first conductive portion preferably contains an alloy of nickel, tin, nickel, palladium, copper, or gold, and more preferably nickel or palladium.
From the viewpoint of further effectively improving the conduction reliability between the electrodes, the first conductive portion preferably contains nickel and phosphorus. The first conductive portion is preferably a conductive portion containing nickel, and preferably contains nickel as a main metal. The nickel content in 100 wt% of the first conductive portion is preferably 10 wt% or more, more preferably 50 wt% or more, further preferably 60 wt% or more, further preferably 70 wt% or more, and particularly preferably 90 wt% or more. The nickel content in 100 wt% of the first conductive portion may be 97 wt% or more, 97.5 wt% or more, or 98 wt% or more. When the nickel content of the first conductive portion is not less than the lower limit, the conduction reliability between the electrodes is further effectively improved.
The phosphorus content in 100 wt% of the first conductive portion is preferably 0.1 wt% or more, more preferably 0.5 wt% or more, and is preferably 15 wt% or less, more preferably 10 wt% or more. When the phosphorus content of the first conductive portion is not less than the lower limit and not more than the upper limit, the connection resistance between the electrodes is further effectively reduced.
From the viewpoint of further effectively improving the reliability of conduction between electrodes, and from the viewpoint of further effectively preventing cracking of the conductive portion due to external impact, it is preferable that the phosphorus content on the second conductive portion side in the first conductive portion is larger than the phosphorus content on the base material particle side in the first conductive portion in the thickness direction of the first conductive portion.
The phosphorus content in 100 wt% of the 1/2-thick region (region 50% thick on the outer surface side) of the first conductive portion from the second conductive portion side toward the inner side is preferably higher than the phosphorus content in 100 wt% of the 1/2-thick region (region 50% thick on the inner surface side) of the first conductive portion from the base material particle side toward the outer side. By setting the phosphorus content in 100 wt% of the region having a thickness of 50% on the outer surface side to be higher than the phosphorus content in 100 wt% of the region having a thickness of 50% on the inner surface side, the inter-electrode conduction reliability is further effectively improved, and breakage of the conductive portion due to external impact can be further effectively prevented.
The phosphorus content in 100 wt% of the 1/2 thickness region (region having a thickness of 50% on the outer surface side) of the first conductive portion from the second conductive portion side toward the inner side is preferably 1 wt% or more, more preferably 3 wt% or more, preferably 15 wt% or less, and more preferably 10 wt% or less. When the phosphorus content in 100 wt% of the 50% thickness region on the outer surface side is not less than the lower limit and not more than the upper limit, the conduction reliability between the electrodes can be further effectively improved. It is possible to further effectively prevent the breakage of the conductive portion due to the external impact.
The phosphorus content in 100 wt% of the 1/2 thickness region (region having a thickness of 50% on the inner surface side) of the first conductive portion from the substrate particle side to the outside is preferably 0.1 wt% or more, more preferably 0.5 wt% or more, preferably 10 wt% or less, and more preferably 5 wt% or less. When the phosphorus content in 100 wt% of the 50% thickness region on the inner surface side is not less than the lower limit and not more than the upper limit, the conduction reliability between the electrodes can be further effectively improved, and the breakage of the conductive portion due to external impact can be further effectively prevented.
The phosphorus content was measured using a field emission type transmission electron microscope ("JEM-2010 FEF", manufactured by japan electronics corporation) generation energy dispersive X-ray analyzer (EDS) using a thin film slice of a conductive particle prepared using a focused ion beam.
The thickness of the first conductive portion is preferably 100nm or more, more preferably 150nm or more, preferably 300nm or less, and more preferably 250nm or less. When the thickness of the first conductive part is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between the electrodes can be further effectively reduced. The thickness of the first conductive portion is a thickness of a portion where the first conductive portion is formed, and does not include a portion where the first conductive portion is not formed. The thickness of the first conductive portion represents an average thickness of the first conductive portions in the conductive particles.
The thickness of the first conductive portion is measured, for example, by observing the cross section of the conductive particle using a Transmission Electron Microscope (TEM).
The conductive particles have a second conductive portion. The second conductive portion preferably contains gold, silver, palladium, platinum, copper, cobalt, ruthenium, indium, or tin, more preferably contains gold or silver, and still more preferably contains gold.
As metals that can be used for the second conductive portion, there can be mentioned: gold, silver, copper, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, palladium, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, tungsten, molybdenum and tin-doped indium oxide (ITO). These metals may be used alone or in combination of two or more.
The second conductive portion is preferably a conductive portion containing gold, preferably containing gold as a main metal. The gold content in 100 wt% of the second conductive portion is preferably 10 wt% or more, more preferably 50 wt% or more, further preferably 60 wt% or more, further preferably 70 wt% or more, and preferably 90 wt% or more. The gold content of the second conductive portion may be 97 wt% or more, 97.5 wt% or more, or 98 wt% or more, based on 100 wt%. When the content of gold or the like in the second conductive portion is not less than the lower limit, the connection resistance between the electrodes can be further effectively reduced.
From the viewpoint of further effectively improving the conduction reliability between the electrodes and from the viewpoint of further effectively preventing the conductive portion from being broken due to external impact, it is preferable that the ionization tendency of the metal contained in the first conductive portion be larger than the ionization tendency of the metal contained in the second conductive portion.
The thickness of the second conductive portion is preferably 20nm or more, more preferably 25nm or more, preferably 40nm or less, and more preferably 35nm or less. When the thickness of the second conductive portion is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between the electrodes is further effectively reduced. The thickness of the second conductive portion is a thickness of a portion where the second conductive portion is formed, and does not include a portion where the second conductive portion is not formed. The thickness of the second conductive portion represents an average thickness of the second conductive portions in the conductive particles.
The thickness of the second conductive portion can be measured, for example, by observing the cross section of the conductive particles using a Transmission Electron Microscope (TEM).
There is no particular limitation as to a method of forming the first conductive portion and the second conductive portion. As a method of forming the first conductive portion and the second conductive portion, for example, there can be mentioned: electroless plating-based methods; a plating-based method; a physical vapor deposition-based method; and a method of applying a paste containing a metal powder or a paste containing a metal powder and a binder to the surface of the particles. The conductive portion is formed simply, and therefore, a method of electroless plating is preferable. The physical vapor deposition method includes: vacuum evaporation, ion plating, ion sputtering and the like.
As a method of controlling the contents of nickel and phosphorus in the first conductive portion, the following method and the like can be mentioned. A method of controlling the pH of a nickel plating solution when forming the first conductive portion by electroless plating. A method for adjusting the concentration of the phosphorous-containing reducing agent when the first conductive portion is formed by electroless plating. A method for adjusting the concentration of nickel in a nickel plating solution.
The method for producing conductive particles comprises a step of providing a second conductive portion on the outer surface of the first conductive portion by plating treatment using conductive particles comprising base particles and a first conductive portion disposed on the surface of the base particles. The step results in conductive particles having the second conductive portion on the outer surface of the first conductive portion.
In the case of forming the first conductive portion, the phosphorus content on the second conductive portion side of the first conductive portion is preferably larger than the phosphorus content on the substrate particle side of the first conductive portion in the thickness direction of the first conductive portion. Forming the first conductive portion in a preferable manner can further effectively improve the conduction reliability between the electrodes, and can further effectively prevent the conductive portion from being broken due to external impact. The phosphorus content on the second conductive portion side in the first conductive portion is made larger than the phosphorus content on the base material particle side in the first conductive portion in the thickness direction of the first conductive portion, whereby elution of a metal (e.g., nickel or the like) as a material of the first conductive portion can be suppressed. As a result, the generation of pin holes in the first conductive part can be suppressed even more effectively, and the breakage of the conductive part due to external impact can be prevented even more effectively.
In the plating treatment for forming the second conductive portion, it is preferable to use displacement gold plating and reduction gold plating in combination from the viewpoint of further effectively improving the reliability of conduction between electrodes and from the viewpoint of further effectively preventing cracking of the conductive portion due to external impact. When the second conductive portion is formed, the substitution gold plating and the reduction gold plating are used in combination, whereby elution of a metal (e.g., nickel or the like) as a material of the first conductive portion can be suppressed. As a result, the generation of pin holes in the first conductive portion can be suppressed even more effectively, and the breakage of the conductive portion due to external impact can be prevented even more effectively.
In addition, as another method for suppressing elution of a metal (e.g., nickel or the like) of the material of the first conductive portion, there is a method of performing nickel plating in advance before performing plating treatment for forming the second conductive portion. By performing nickel plating in advance, nickel for elution eluted by performing plating treatment (displacement gold plating and reduction gold plating) for forming the second conductive portion can be provided in advance on the surface of the first conductive portion. In the plating process (displacement plating and reduction plating) for forming the second conductive portion, elution of a metal (e.g., nickel) as a material of the first conductive portion can be suppressed by elution of nickel for elution. As a result, the generation of pin holes in the first conductive part can be suppressed even more effectively, and the breakage of the conductive part due to external impact can be prevented even more effectively.
From the viewpoint of further effectively improving the reliability of conduction between electrodes, and from the viewpoint of further effectively improving the reliability of conduction between electrodesFrom the viewpoint of effectively preventing breakage of the conductive portion due to external impact, it is preferable that the method for producing the conductive particles is a combination of the above methods. Specifically, it is preferable to combine the following (first technical feature), (second technical feature), and (third technical feature). In the method for producing the conductive particles, a phosphorus content on the second conductive portion side in the first conductive portion in a thickness direction of the first conductive portion is larger than a phosphorus content on the base material particle side in the first conductive portion. (second technical feature) the plating process of forming the second conductive portion uses displacement gold plating and reduction gold plating in combination. (third technical feature) before the plating process for forming the second conductive portion is performed, nickel plating is performed in advance. By combining all the technical features, when the outer surface of the second conductive part is observed with an electron microscope, the second conductive part can be formed so that there is no pinhole having a size of 50nm or more in the maximum length direction or 1/μm2The size in the maximum length direction of the pinhole is 50nm or more.
(core material)
Preferably, the conductive particles have a plurality of protrusions on outer surfaces of the first conductive portion and the second conductive portion. The conductive particles preferably have a plurality of protrusions on outer surfaces of the first conductive portion and the second conductive portion, whereby the conduction reliability between electrodes can be further enhanced. An oxide film is usually formed on the surface of the electrode connected by the conductive particles. An oxide film is usually formed on the surfaces of the first conductive part and the second conductive part of the conductive particles. By using the conductive particles having the protrusions, the conductive particles can be provided between the electrodes, and then, by press-fitting, the oxide film can be effectively removed by the protrusions. Therefore, the electrode and the conductive particles can be brought into contact with each other more reliably, and the connection resistance between the electrodes can be reduced more effectively. In addition, when the conductive particles have an insulating substance on the surface, or when the conductive particles are dispersed in a binder resin and used as a conductive material, the resin between the conductive particles and the electrode is effectively eliminated due to the protrusions of the conductive particles. Therefore, the conduction reliability between the electrodes can be further effectively improved.
The core material is embedded in the first conductive portion and the second conductive portion, whereby a plurality of protrusions can be easily formed on the outer surfaces of the first conductive portion and the second conductive portion. Wherein a core material may not necessarily be used for forming the protrusions on the surfaces of the first conductive portion and the second conductive portion.
A method of forming the protrusions, which comprises attaching a core material to the surface of the base material particles, and then forming the first conductive portion and the second conductive portion by electroless plating; and a method of forming the first conductive portion on the surface of the base material particle by electroless plating, then attaching the core material, and forming the second conductive portion by electroless plating. As another method for forming the protrusion, a method in which a first conductive portion is formed on the surface of the base material particle, then a core material is provided on the first conductive portion, and then a second conductive portion is formed; and a method of adding a core material at an intermediate stage of forming a conductive portion (a first conductive portion, a second conductive portion, or the like) on the surface of the base material particle. In addition, in order to form the protrusion, the following method may be used: the first conductive portion is formed by electroless plating of the base material particles without using the core material, and then the plating layer is deposited in a protruding form on the surface of the first conductive portion, and the second conductive portion may be formed by electroless plating.
As a method of providing the core substance on the outer surface of the base material particle, for example, a method of adding the core substance to a dispersion liquid of the base material particle, and aggregating and adhering the core substance to the surface of the base material particle by van der waals force or the like; a method in which the core material is added to a container containing the base material particles, and the core material is attached to the surface of the base material particles by a mechanical action such as rotation of the container. Since it is easy to control the amount of the core material to be attached, a method of accumulating and attaching the core material to the surface of the base material particles in the dispersion is preferable.
The material of the core material is not particularly limited. Examples of the material of the core material include a conductive material and a non-conductive material. As the conductive substance, there can be mentioned: conductive non-metals such as metals, metal oxides, graphite, and conductive polymers. As the conductive polymer, there may be mentioned: polyacetylene, and the like. As the non-conductive material, there can be mentioned: silica, alumina, barium titanate, zirconia, and the like. The core material is preferably a metal since conductivity can be increased and connection resistance can be effectively reduced. The core material is preferably a metal particle. As the metal as the material of the core material, the metals listed as the material of the conductive material can be suitably used.
The mohs hardness of the material of the core material is preferably high. Examples of the material having a high mohs hardness include: barium titanate (mohs hardness 4.5), nickel (mohs hardness 5), silica (mohs hardness 6-7), titanium oxide (mohs hardness 7), zirconium oxide (mohs hardness 8-9), aluminum oxide (mohs hardness 9), tungsten carbide (mohs hardness 9), diamond (mohs hardness 10), and the like. The core material is preferably nickel, silica, titania, zirconia, alumina, tungsten carbide or diamond, more preferably silica, titania, zirconia, alumina, tungsten carbide or diamond. The core material is more preferably titanium oxide, zirconium oxide, aluminum oxide, tungsten carbide, or diamond, and particularly preferably zirconium oxide, aluminum oxide, tungsten carbide, or diamond. The mohs hardness of the material of the core material is preferably 4 or more, more preferably 5 or more, further preferably 6 or more, further preferably 7 or more, and particularly preferably 7.5 or more.
The shape of the core material is not particularly limited. The shape of the core material is preferably a block. Examples of the core material include a particulate lump, an aggregate of a plurality of fine particles, and an amorphous lump.
The particle diameter of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, and more preferably 0.2 μm or less. When the particle diameter of the core material is not less than the lower limit and not more than the upper limit, the connection resistance between the electrodes can be effectively reduced.
The particle size of the core material means a number average particle size. The particle size of the core material is preferably determined by observing arbitrary 50 core materials with an electron microscope or an optical microscope and calculating the average value.
The number of the protrusions corresponding to 1 conductive particle is preferably 3 or more, and more preferably 5 or more. The upper limit of the number of the protrusions is not particularly limited. The upper limit of the number of the protrusions is appropriately selected in consideration of the particle diameter of the conductive particles, the use of the conductive particles, and the like.
The number of protrusions corresponding to 1 conductive particle is preferably determined by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating an average value.
The height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, and is preferably 0.9 μm or less, more preferably 0.2 μm or less. When the height of the protrusion is not less than the lower limit and not more than the upper limit, the connection resistance between the electrodes can be effectively reduced.
The heights of the plurality of protrusions are determined by observing 50 arbitrary conductive particles with an electron microscope or an optical microscope and calculating an average value.
(insulating Material)
The conductive particles preferably include an insulating material provided on a surface of the conductive portion. In this case, when the conductive particles are used for connection between electrodes, short-circuiting between adjacent electrodes can be further prevented. Specifically, when the plurality of conductive particles are in contact with each other, an insulating substance is present between the plurality of electrodes, so that short-circuiting between adjacent electrodes in the lateral direction, not between the top and bottom, can be prevented. In addition, when the conductive particles are connected between the electrodes, the insulating material between the conductive portion of the conductive particles and the electrodes can be easily removed by pressurizing the conductive particles with two electrodes. When the conductive particles have a plurality of protrusions on the outer surface of the conductive portion, the insulating material between the conductive portion of the conductive particles and the electrode can be removed more easily.
The insulating material is preferably insulating particles, because the insulating material can be more easily removed when the pressure bonding is performed between the electrodes.
Examples of the material of the insulating material include a material of the resin particles and an inorganic material as a material of the base particles. The material of the insulating material is preferably the material of the resin particles. The insulating material is preferably the resin particles or the organic-inorganic hybrid particles, and may be resin particles or organic-inorganic hybrid particles.
Examples of other materials of the insulating material include: polyolefin compounds, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked products of thermoplastic resins, thermosetting resins, water-soluble materials, and the like. The material of the insulating material may be used alone or in combination of two or more.
As the polyolefin compound, there can be mentioned: polyethylene, ethylene-vinyl acetate copolymers, ethylene-acrylate copolymers, and the like. As the (meth) acrylate ester polymer, there may be mentioned: polymethyl (meth) acrylate, polydodecyl (meth) acrylate, and polystearyl (meth) acrylate, and the like. As the block polymer, there may be mentioned: polystyrene, styrene-acrylate copolymers, SB type styrene-butadiene block copolymers, SBs type styrene-butadiene block copolymers, and hydrogenated products thereof, and the like. As the thermoplastic resin, there may be mentioned: vinyl polymers and vinyl copolymers, and the like. As the thermosetting resin, there can be mentioned: epoxy resins, phenolic resins, melamine resins, and the like. The crosslinked product of the thermoplastic resin may be introduced with: polyethylene glycol methacrylate, alkoxylated trimethylolpropane methacrylate, alkoxylated pentaerythritol methacrylate, and the like. Examples of the water-soluble resin include: polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, methyl cellulose, and the like. In addition, a chain transfer agent may be used to adjust the degree of polymerization. Examples of the chain transfer agent include: mercaptans, carbon tetrachloride, and the like.
As a method for providing an insulating material on the surface of the conductive portion (second conductive portion), there can be mentioned: chemical, physical or mechanical methods, and the like. As the chemical method, there may be mentioned: interfacial polymerization, suspension polymerization in the presence of particles, emulsion polymerization, and the like. As the physical or mechanical method, there may be mentioned: spray drying, hybridization, electrostatic adhesion, spraying, dipping, vacuum evaporation, and the like. Since the insulating material is less likely to be detached, it is preferable that the insulating material is provided on the surface of the second conductive part by chemical bonding.
The outer surface of the conductive portion (second conductive portion) and the surface of the insulating material may be coated with a compound having a reactive functional group. The outer surface of the conductive portion (second conductive portion) and the surface of the insulating material may not be directly chemically bonded, but may be indirectly chemically bonded through a compound having a reactive functional group. After the carboxyl group is introduced into the outer surface of the conductive portion (second conductive portion), the carboxyl group can be chemically bonded to the functional group on the surface of the insulating material via a polymer electrolyte such as polyethyleneimine.
The particle size of the insulating material may be appropriately selected according to the particle size of the conductive particles, the use of the conductive particles, and the like. The particle diameter of the insulating material is preferably 10nm or more, more preferably 100nm or more, preferably 4000nm or less, and more preferably 2000nm or less. When the particle diameter of the insulating material is not less than the lower limit, the conductive particles are dispersed in the binder resin, and the conductive portions of the plurality of conductive particles are less likely to contact each other. When the particle diameter of the insulating material is not more than the upper limit, it is not always necessary to remove the insulating material between the electrode and the conductive particles by excessively increasing the pressure and heating to a high temperature at the time of connection between the electrodes.
The particle diameter of the insulating material is expressed as a number average particle diameter. The particle diameter of the insulating material can be determined using a particle size distribution measuring apparatus or the like. It is preferable to determine the particle size of the insulating material by observing 50 arbitrary insulating materials with an electron microscope or an optical microscope and calculating the average value. When the particle diameter of the insulating material is measured, the conductive particles can be measured, for example, as follows.
Conductive particles were added and dispersed in "Technobit 4000" manufactured by Kulzer corporation so that the content of the conductive particles was 30% by weight, and a embedding resin for conductive particle inspection was prepared. A cross section of the conductive particles was cut using an ion milling apparatus ("IM 4000" manufactured by HitachiHigh-Technologies Corporation) so that the cross section passed near the center of the conductive particles dispersed in the embedding resin for inspection. Then, the base material particles of each conductive particle were observed by randomly selecting 50 conductive particles with an image magnification of 5 ten thousand times using a field emission scanning electron microscope (FE-SEM). The particle diameter of the insulating material in each conductive particle was measured, and the average was taken as the particle diameter of the insulating material.
(conductive Material)
The conductive material of the present invention includes the conductive particles and a binder resin. The conductive particles are preferably used as dispersed in a binder resin, and are preferably used as a conductive material dispersed in a binder resin. The conductive material is preferably an anisotropic conductive material. The conductive material is preferably used for electrical connection between the electrodes. The conductive material is preferably a conductive material for circuit connection.
The binder resin is not particularly limited. A known insulating resin is used as the binder resin. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent.
As the binder resin, there may be mentioned: vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, elastomers, and the like. The binder resin may be used alone or in combination of two or more.
As the vinyl resin, there can be mentioned: vinyl acetate resins, acrylic resins, styrene resins, and the like. As the thermoplastic resin, there may be mentioned: polyolefin resins, ethylene-vinyl acetate copolymers, polyamide resins, and the like. Examples of the curable resin include: epoxy resins, polyurethane resins, polyimide resins, unsaturated polyester resins, and the like. The curable resin may be a room temperature curable resin, a thermosetting resin, a photo-curable resin, or a moisture-curable resin. The curable resin may be used in combination with a curing agent. As the thermoplastic block copolymer, there can be mentioned: styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, hydrogenated products of styrene-butadiene-styrene block copolymers, hydrogenated products of styrene-isoprene-styrene block copolymers, and the like. As the elastomer, there may be mentioned: styrene-butadiene copolymer rubber, acrylonitrile-styrene block copolymer rubber, and the like.
The conductive material may contain, in addition to the conductive particles and the binder resin, for example: fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, UV absorbers, lubricants, antistatic agents, flame retardants, and the like.
From the viewpoint of further effectively reducing the connection resistance between the electrodes and from the viewpoint of further effectively improving the conduction reliability between the electrodes, the viscosity (η 25) of the conductive material at 25 ℃ is preferably 20Pa · s or more, more preferably 30Pa · s or more, preferably 400Pa · s or less, and more preferably 300Pa · s or less. The viscosity (. eta.25) may be appropriately adjusted depending on the type of the components to be mixed and the amount to be mixed.
The viscosity can be measured, for example, using an E-type viscometer ("TVE 22L" manufactured by eastern mechanical industries co., ltd.) at 25 ℃ and 5 rpm.
The conductive material can be used as a conductive paste, a conductive film, and the like. When the conductive material is a conductive film, a film containing no conductive particles may be stacked on the conductive film containing conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.
The content of the binder resin is preferably 10% by weight or more, more preferably 30% by weight or more, still more preferably 50% by weight or more, and particularly preferably 70% by weight or more, of 100% by weight of the conductive material. Preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is not less than the lower limit and not more than the upper limit, the conductive particles are effectively provided between the electrodes, and the connection reliability of the connection target members connected by the conductive material is further effectively improved.
The content of the conductive particles is preferably 0.01 wt% or more, more preferably 0.1 wt% or more, and preferably 80 wt% or less, more preferably 60 wt% or less, more preferably 40 wt% or less, particularly preferably 20 wt% or less, and most preferably 10 wt% or less, in 100 wt% of the conductive material. When the content of the conductive particles is not less than the lower limit and not more than the upper limit, the conduction reliability between the electrodes is further enhanced.
(connection structure)
The connection structure can be obtained by connecting members to be connected using the conductive particles or a conductive material containing the conductive particles and a binder resin.
The connection structure is provided with: the first connection object member, the second connection object member, and a connecting portion that connects the first connection object member and the second connection object member together. The material of the connecting portion is preferably the conductive particles, or preferably a conductive material containing the conductive particles and a binder resin. Preferably, the connecting portion is formed of the conductive particles or a conductive material containing the conductive particles and a binder resin. When conductive particles are used, the connecting portion itself is conductive particles.
The first connection target member preferably has a first electrode on a surface thereof. The second connection target member preferably has a second electrode on a surface thereof. Preferably, the first electrode and the second electrode are electrically connected by the conductive particles.
The connection structure preferably includes a flexible member as the first connection target member or the second connection target member. In this case, at least one of the first member to be connected and the second member to be connected may be a flexible member, or both of the first member to be connected and the second member to be connected may be a flexible member. The connection structure is preferably used in a state where the flexible member is bent. The connection structure is preferably used in a state where the connection portion is bent.
Fig. 3 is a sectional view schematically showing a connection structure using conductive particles according to a first embodiment of the present invention.
The connection structure 51 shown in fig. 3 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 that connects the first connection target member 52 and the second connection target member 53. The connection portion 54 is formed of a conductive material containing conductive particles 1. Preferably, the conductive material is thermosetting, and the connection portion 54 is formed by thermosetting the conductive material. For convenience of explanation, fig. 3 schematically shows the conductive particles 1. The conductive particles 1 may be replaced with the conductive particles 21 or the like.
The first connection target member 52 has a plurality of first electrodes 52a on a surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on the surface (lower surface). The first electrode 52a and the second electrode 53a are electrically connected by one or more conductive particles 1. Therefore, the first member to be connected 52 and the second member to be connected 53 are electrically connected by the conductive particles 1.
The method for producing the connection structure is not particularly limited. As an example of manufacturing the connection structure, there is a method in which the conductive material is provided between the first connection target member and the second connection target member to obtain a laminated body, and then the laminated body is heated and pressed. The pressure of the thermocompression bonding is 0.5 × 10 relative to the bonding area6Pa～5×106Pa or so. The heating temperature of the hot pressing is about 70-230 ℃. The heating temperature for the thermocompression bonding is preferably 80 ℃ or higher, more preferably 100 ℃ or higher, preferably 200 ℃ or lower, and more preferably 150 ℃ or lower. The pressure of the thermal compression is preferably 0.5X 106Pa or more, more preferably 1X 106Pa or more, preferably 5X 106Pa or less, more preferably 3X 106Pa or less. When the pressure and temperature of the thermocompression bonding are not lower than the lower limit and not higher than the upper limit, the conduction reliability between the electrodes can be further effectively improved.
As the connection target member, specifically, there are mentioned: and electronic components such as semiconductor chips, capacitors, and diodes, and electronic components such as printed wiring boards, flexible printed circuits, glass epoxy substrates, and glass substrates. The connection target component is preferably an electronic component. The conductive particles are preferably used for electrically connecting electrodes in an electronic component.
Examples of the electrode provided in the connection target member include: metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, silver electrodes, SUS electrodes, copper electrodes, molybdenum electrodes, and tungsten electrodes. When the member to be connected is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the member to be connected is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. When the electrode is an aluminum electrode, the electrode may be formed of aluminum alone or an aluminum layer may be laminated on the surface of the metal oxide layer. Examples of the material of the metal oxide layer include indium oxide doped with a metal element having a valence of 3, zinc oxide doped with a metal element having a valence of 3, and the like. Examples of the trivalent metal element include Sn, Al, and Ga.
Hereinafter, the present invention will be specifically explained by examples and comparative examples. The present invention is not limited to the following examples.
Substrate particles:
substrate particle A: resin particles, copolymer resin particles of divinylbenzene and isobornyl acrylate, particle diameter: 10 μm
Base material particles B: resin particles, copolymer resin particles of divinylbenzene and isobornyl acrylate, particle diameter: 5 μm
Base material particles C: resin particles, copolymer resin particles of divinylbenzene and isobornyl acrylate, particle diameter: 20 μm
(example 1)
(1) Formation of first conductive portion (nickel layer)
In the case of using an ultrasonic disperser, 10 parts by weight of the base material particles a were dispersed in 100 parts by weight of an alkaline solution containing a 5% by weight palladium catalyst solution, and then, the solution was filtered to take out the base material particles a. Then, the substrate particles a were added to 100 parts by weight of a 1% by weight dimethylamine borane solution to activate the surfaces of the substrate particles a. After the base material particles a whose surfaces were activated were sufficiently washed, they were added to 500 parts by weight of distilled water and dispersed to obtain a suspension.
In addition, a nickel plating solution (pH9.0) containing 0.25mol/L nickel sulfate, 0.25mol/L sodium hypophosphite, and 0.15mol/L sodium citrate was prepared.
The resulting suspension was stirred at 70 ℃, and the nickel plating solution was gradually dropped into the suspension to perform electroless nickel plating. Then, the suspension was filtered to take out the particles, and the particles were washed with water and dried to obtain particles in which the first conductive portion (nickel-phosphorus layer, thickness 200nm) was provided on the surface of the substrate particles a. The conductive layer had a nickel content of 94.5 wt% and a phosphorus content of 5.5 wt% in 100 wt%.
(2) Formation of second conductive part (gold layer)
A suspension was obtained by adding 10 parts by weight of particles having the first conductive portion provided on the surface of the base material particle a to 100 parts by weight of distilled water and dispersing. In addition, a reductive gold plating solution containing 0.03mol/L of gold cyanide and 0.1mol/L of hydroquinone as reducing agents was prepared. The resulting suspension was stirred at 70 ℃ and the reduced gold plating solution was gradually added dropwise to the suspension to perform the reduction gold plating. Thereafter, the particles were taken out by filtering the suspension, and by washing with water and drying, conductive particles were obtained. In the obtained conductive particle, a second conductive portion (gold layer, thickness 31nm) was provided on the outer surface of the first conductive portion. Fig. 4 is an image showing the surface of the conductive particle produced in example 1.
(example 2)
(1) Formation of first conductive portion (nickel layer)
After dispersing 10 parts by weight of the base particles B in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, the solution was filtered to remove the base particles B. Then, the substrate particles B were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surfaces of the substrate particles B. After the base particles B whose surfaces were activated were sufficiently washed, they were added to 500 parts by weight of distilled water and dispersed to obtain a suspension.
In addition, a nickel plating solution (pH9.0) containing 0.25mol/L nickel sulfate, 0.25mol/L sodium hypophosphite, and 0.15mol/L sodium citrate was prepared.
The resulting suspension was stirred at 70 ℃, and the nickel plating solution was gradually dropped into the suspension to perform electroless nickel plating. Then, the suspension was filtered to remove the particles, and the particles were washed with water and dried to obtain particles in which the first conductive portion (nickel-phosphorus layer, thickness 210nm) was provided on the surface of the substrate particles B. The conductive layer had a 100 wt% nickel content of 94.5 wt% and a phosphorus content of 5.5 wt%.
(2) Formation of nickel plating
The suspension was obtained by adding 10 parts by weight of particles having the first conductive portion provided on the surface of the base material particle B to 100 parts by weight of distilled water and dispersing. In addition, 52mL of a nickel solution containing 10 wt% nickel sulfate, 10 wt% sodium hypophosphite, 4 wt% sodium hydroxide and 20 wt% sodium succinate was prepared. The resulting suspension was stirred at 80 ℃ and the nickel solution was continuously added dropwise at 5mL/min, and the plating reaction was allowed to proceed by stirring for 20 minutes. After confirming that hydrogen was no longer generated, the plating reaction was terminated. Then, the suspension was filtered to take out the particles, and the particles were washed with water and dried to obtain particles in which the first conductive portion and the nickel plating layer were provided on the surface of the base particles B.
(3) Formation of second conductive part (gold layer)
10 parts by weight of particles provided with the first conductive portion and the nickel plating layer were added to 100 parts by weight of distilled water using an ultrasonic disperser, and dispersed to obtain a suspension. In addition, a reductive gold plating solution containing 0.03mol/L of gold cyanide and 0.1mol/L of hydroquinone as reducing agents was prepared. The resulting suspension was stirred at 70 ℃ and the reductive gold plating solution was gradually dropped into the suspension to perform reductive gold plating. Thereafter, the particles were taken out by filtering the suspension, washed with water and dried to obtain conductive particles. In the obtained conductive particle, the second conductive portion (gold layer, thickness 30nm) was provided on the outer surface of the first conductive portion.
(example 3)
Conductive particles were obtained in the same manner as in example 2 except that the base material particles B were changed to the base material particles C when the first conductive portion was formed and the thickness of the second conductive portion was changed to 35 nm. In the obtained conductive particle, the second conductive portion (gold layer, thickness 35nm) was provided on the outer surface of the first conductive portion.
(example 4)
Conductive particles were obtained in the same manner as in example 2 except that the substrate particles B were changed to the substrate particles a, 1 part by weight of metallic nickel particles (average particle diameter 150nm) were added to the obtained suspension to obtain a suspension containing the substrate particles a with the core material adhered thereto, and the thickness of the second conductive portion was changed to 29 nm. In the obtained conductive particle, a second conductive portion (gold layer, thickness 29nm) was provided on the outer surface of the first conductive portion. The obtained conductive particles have a plurality of protrusions on the outer surfaces of the first conductive portion and the second conductive portion.
(example 5)
When the second conductive portion was formed, the thickness of the first conductive portion was changed to 230nm, the thickness of the second conductive portion was changed to 15nm, and the thickness of the first conductive portion was changed to 230nm, 0.03mol/L gold cyanide was changed to 0.015mol/L gold cyanide, and the thickness of the second conductive portion was changed to 230 nm. Except for this, conductive particles were obtained in the same manner as in example 2. In the obtained conductive particle, a second conductive portion (gold layer, thickness 15nm) was provided on the outer surface of the first conductive portion.
(example 6)
Conductive particles were obtained in the same manner as in example 1, except that gold cyanide was changed to palladium sulfate and the thickness of the second conductive portion was changed to 30nm when the second conductive portion was formed. In the obtained conductive particle, the second conductive part (palladium layer, thickness 30nm) was provided on the outer surface of the first conductive part.
(example 7)
Conductive particles were obtained in the same manner as in example 2, except that the substrate particles B were changed to the substrate particles a and the thickness of the second conductive portion was changed to 32nm when the first conductive portion was formed. In the obtained conductive particle, the second conductive portion (gold layer, thickness 32nm) was provided on the outer surface of the first conductive portion.
Comparative example 1
A displacement gold plating solution containing no hydroquinone was prepared as a reducing agent. Conductive particles were obtained in the same manner as in example 1 except that, when the second conductive portion was formed, the reductive gold plating was changed to the displacement gold plating solution, the reductive gold plating solution was changed to the displacement gold plating solution to form the second conductive portion, the second conductive portion was formed by the displacement gold plating solution instead of the reductive gold plating solution, and the thickness of the conductive portion was changed to 32 nm. In the obtained conductive particle, a second conductive portion (gold layer, thickness 32nm) was provided on the outer surface of the first conductive portion. Fig. 5 shows an image of the surface of the conductive particle prepared in comparative example 1.
(evaluation)
(1) Existence state of pinhole
The surface of the second conductive part of the obtained conductive particles was observed with an electron microscope ("FE-SEM SU 8010" manufactured by High-Technologies Corporation), and the presence or absence of first pinholes having a size of 50nm or more in the maximum length direction was evaluated. Specifically, the obtained conductive particles were charged at a portion other than the 0.5 μm portion from the outer periphery to the inner sideThe sub-microscope observed any five positions, thereby evaluating whether the observation was the presence or absence of the pinhole. When there is a first pinhole having a size of 50nm or more in the maximum length direction, the measurement corresponds to 1 μm2The number of first pinholes is 50nm or more in the maximum length direction. In addition, whether or not there is a second pinhole having a size of 50nm or more and 200nm or less in the maximum length direction was evaluated. When there is a second pinhole having a size of 50nm or more and 200nm or less in the maximum length direction, the measurement corresponds to 1 μm2The number of second pinholes is 50nm to 200nm in the maximum length direction.
(2) 10% K value
The 10% K value of the resulting conductive particles was measured by the method.
(3) Compression recovery at 25 deg.C
The compression recovery rate of the obtained conductive particles at 25 ℃ was measured by the method.
(4) Average particle diameter
The average particle diameter of the obtained conductive particles was measured using a "laser diffraction type particle size distribution measuring apparatus" manufactured by horiba ltd. The average particle diameter of the conductive particles was calculated by averaging the 20 measurements.
(5) Phosphorus content in thickness direction of first conductive part
Thin film slices of the resulting conductive particles were prepared using a focused ion beam. The phosphorus content in the thickness direction of the first conductive portion was measured by an energy dispersive X-ray analyzer (EDS) using a field emission type transmission electron microscope ("JEM-2010 FEF" manufactured by japan electronics corporation). From the results, it was found that the phosphorus content in the region of the first conductive part with a thickness of 1/2 from the substrate particle side toward the outside (region with a thickness of 50% on the inner surface side) was 100% by weight, and the phosphorus content in the region of the first conductive part with a thickness of 1/2 from the second conductive part side toward the inside (region with a thickness of 50% on the outer surface side) was 100% by weight.
(6) Cracking of conductive parts
The obtained conductive particles were used to evaluate cracking of the conductive portion. Cracking of the conductive portion was evaluated as follows. The breakage of the conductive portion is determined according to the following criteria.
Evaluation method of conductive portion cracking:
an electron microscope was used to take 1000 photographs of the conductive particles at 1 magnification of about 100 photographs of the conductive particles. The obtained 1000 photographs of the conductive particles were observed, and the number of the conductive particles having cracks whose length was half or more the diameter of the conductive particles was measured.
[ criterion for judging breakage of conductive part ]
O: the number of the broken conductive particles is less than 100
X: the number of the broken conductive particles is more than 100
(7) Initial connection resistance
Preparation of connecting structure X:
the obtained conductive particles were added to "Structbond XN-5A" manufactured by Mitsui chemical Co., Ltd to give a content of the obtained conductive particles of 10% by weight, and dispersed to prepare an anisotropic conductive paste.
A transparent glass substrate having an ITO electrode pattern with an L/S of 20 μm/20 μm on the upper surface was prepared. In addition, a semiconductor chip having a gold electrode pattern with an L/S of 20 μm/20 μm on the lower surface was prepared.
On the transparent glass substrate, the anisotropic conductive paste just after the preparation was coated to a thickness of 30 μm to form an anisotropic conductive paste layer. Then, the semiconductor chip is laminated on the anisotropic conductive paste layer so that the electrodes face each other. Thereafter, the temperature of the head was adjusted so that the temperature of the anisotropic conductive paste layer was 120 ℃, and a pressure heating head was placed on the upper surface of the semiconductor chip, a low pressure of 1MPa calculated from the pressure area was applied, and the anisotropic conductive paste layer was cured at 100 ℃, resulting in a connection structure body X.
Preparation of connecting structure Y:
the connection structure body Y is manufactured in the same manner as the connection structure body X except that the temperature at which the anisotropic conductive material layer is cured is changed to 150 ℃.
Preparation of connecting structure Z:
the connection structure body Z was manufactured in the same manner as the connection structure body X except that the temperature at which the anisotropic conductive material layer was cured was changed to 200 ℃.
The connection resistance a between the upper electrode and the lower electrode of the obtained connection structures X, Y and Z was measured by the four-terminal method. The connection resistance a can be obtained by measuring the voltage when a constant current flows from the relationship of voltage to current × resistance. The initial connection resistance is determined from the connection resistance a based on the following criteria.
[ criterion for determining initial connection resistance ]
O ≈: the connection resistance A is less than 2.0 omega
O ^ O: the connection resistance A is more than 2.0 omega and less than 3.0 omega
O: the connection resistance A is more than 3.0 omega and less than 5.0 omega
Δ connection resistance A of more than 5.0 Ω and 10 Ω or less
X: the connecting resistance A is more than 10 omega
(8) Connection resistance after high temperature and high humidity placing (conduction reliability)
The connection structure X, Y and Z after the evaluation of the initial connection resistance of (7) were left to stand at 85 ℃ and 85% humidity for 500 hours. After leaving standing for 500 hours, the connection resistance B between the upper and lower electrodes of the connection structure X, Y and Z was measured by the four-terminal method, respectively. The connection resistance (on reliability) of the connection resistor A, B after high-temperature and high-humidity leaving is determined according to the following criteria.
[ criterion for determining connection resistance (on-state reliability) after high-temperature and high-humidity leaving ]
O ≈: the connection resistance B is less than 1.25 times of the connection resistance A
O ^ O: the connecting resistance B is more than 1.25 times and less than 1.5 times of the connecting resistance A
O: the connecting resistance B is more than 1.5 times and less than 2 times of the connecting resistance A
Δ the connection resistance B is 2 times or more and less than 5 times of the connection resistance A
X: the connecting resistance B is more than 5 times of the connecting resistance A
The results are shown in tables 1 and 2 below.
Description of the symbols
Conductive particles
Substrate particles
A first conductive part
A second conductive portion
Conductive particles
A.protrusion
A first conductive portion
A.protrusion
A second conductive portion
A protrusion
Core material
An insulating material
A connection structure
A first connection subject component
A first electrode
53.. second connection object part
A second electrode
54. connecting part

Claims (11)

1. A conductive particle comprising:
a base material particle,
A first conductive part disposed on the surface of the base material particle, and
a second conductive portion disposed on an outer surface of the first conductive portion,
when the outer surface of the second conductive part is observed by using an electron microscope, there is no ruler in the maximum length directionThe size of the pinhole is more than 50nm, or 1/mum exists2The size in the maximum length direction of the pinhole is 50nm or more.
2. A conductive particle comprising:
a base material particle,
A first conductive part disposed on the surface of the base material particle, and
a second conductive portion disposed on an outer surface of the first conductive portion,
when the outer surface of the second conductive part is observed by using an electron microscope, no pinhole having a size of 50nm or more in the maximum length direction exists, or 1 piece/mum exists2The size in the maximum length direction of the pinhole is 50nm to 200 nm.
3. The conductive particle according to claim 1 or 2, which satisfies the following formula (1) and has a compression recovery rate at 25 ℃ of 10% or less,
a is less than or equal to 5500-B is multiplied by 100 … formula (1)
In the formula (1), A is 10% K value (N/mm) of the conductive particles2) And B is the average particle diameter (μm) of the conductive particles.
4. The conductive particle according to any one of claims 1 to 3, having an average particle diameter of 3 μm or more and 30 μm or less.
5. The conductive particle according to any one of claims 1 to 4, wherein the second conductive portion comprises gold, silver, palladium, platinum, copper, cobalt, ruthenium, indium, or tin.
6. The conductive particle according to any one of claims 1 to 5, wherein an ionization tendency of a metal contained in the first conductive portion is larger than an ionization tendency of a metal contained in the second conductive portion.
7. The conductive particle according to any one of claims 1 to 6, wherein the first conductive portion contains nickel and phosphorus.
8. The conductive particle according to any one of claims 1 to 7, wherein a phosphorus content on the second conductive portion side in the first conductive portion is larger than a phosphorus content on the substrate particle side in the first conductive portion in a thickness direction of the first conductive portion.
9. A method for producing conductive particles, comprising the steps of:
a step of providing a second conductive portion by applying plating treatment to the outer surface of the first conductive portion using conductive particles including base material particles and the first conductive portion provided on the surface of the base material particles,
the second conductive part is formed such that when the outer surface of the second conductive part is observed using an electron microscope, pinholes having a size of 50nm or more in the maximum length direction do not exist or 1 piece/μm exists2The size in the maximum length direction of the pinhole is 50nm or more.
10. An electrically conductive material, comprising: the conductive particles according to any one of claims 1 to 8, and a binder resin.
11. A connection structure body is provided with:
a first member to be connected having a first electrode on the surface thereof,
A second connection object member having a second electrode on the surface thereof, and
a connecting portion that connects the first connection target member and the second connection target member together,
the material of the connecting part is the conductive particle according to any one of claims 1 to 8, or a conductive material containing the conductive particle and a binder resin,
the first electrode and the second electrode are electrically connected by the conductive particles.
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