KR101205041B1 - Conductive particle - Google Patents

Abstract

The present invention covers the core particles (11), the palladium layer (12) and the palladium layer (12) having a phosphorus concentration of 1% by weight or more and 10% by weight or less and a thickness of 20 nm or more and 130 nm or less, covering the core particles (11). It relates to the electrically-conductive particle 8b arrange | positioned at the surface of and provided with the insulating particle 1 whose particle diameter is 20 nm or more and 500 nm or less.

Description

Conductive Particles {CONDUCTIVE PARTICLE}

The present invention relates to conductive particles.

The liquid crystal drive IC is mounted on a glass panel for liquid crystal display by using two types of COG (Chip-on-Glass) and COF (Chip-on-Flex). It can be divided into.

In COG mounting, the IC for liquid crystals is directly bonded on a glass panel using the anisotropic conductive adhesive containing electroconductive particle. On the other hand, in COF mounting, liquid crystal drive IC is bonded to the flexible tape which has metal wiring, and these are bonded to a glass panel using the anisotropic conductive adhesive containing electroconductive particle. Anisotropy here means conducting in a pressurizing direction and maintaining insulation in a non-pressurizing direction.

By the way, with the recent high definition of the liquid crystal display, in the bump which is a circuit electrode of a liquid crystal drive IC, since it is narrowing in pitch and narrowing in area, the electrically-conductive particle of an anisotropic conductive adhesive flows out between adjacent circuit electrodes, and is short. It has been a problem to generate.

In addition, when conductive particles flow out between adjacent circuit electrodes, the number of conductive particles in the anisotropic conductive adhesive supplemented between the bumps and the glass panel decreases, and the connection resistance between the opposing circuit electrodes rises, resulting in poor connection. There was a problem.

As a method of solving these problems, as illustrated in the following Patent Document 1, by forming an insulating adhesive on at least one side of the anisotropic conductive adhesive, a method of preventing the deterioration of the bonding quality in COG mounting or COF mounting, As illustrated in Patent Document 2, there is a method of covering the entire surface of the conductive particles with an insulating coating.

The following patent documents 3 and 4 show the method of coating the nucleus particle of the high molecular polymer covered with the gold layer with insulating magnetic particle. Moreover, in following patent document 4, the method of forming a functional group on the surface of a gold layer is shown by processing the surface of the gold layer which coat | covers a nuclear particle with the compound which has any one of a mercapto group, a sulfide group, and a disulfide group. Thereby, a firm functional group can be formed on a gold layer.

The following patent document 5 shows the method of performing copper / gold plating on resin fine particles as an attempt to improve the electroconductivity of electroconductive particle.

In Patent Document 6, conductive particles comprising a nonmetal fine particle, a metal layer covering 50 wt% or more of copper covering the nonmetal fine particle, a nickel layer covering the metal layer, and a gold layer covering the nickel layer, It is shown and according to this electroconductive particle, there exists a description that electroconductivity improves compared with the electroconductive particle which consists of general nickel and gold.

The following patent document 7 has electroconductive particle which is 90 weight% or more and 99 weight% or less as electroconductive particle which has a substrate fine particle and the metal coating layer provided on the said substrate fine particle, The metal coating layer is characterized by the above-mentioned. .

Japanese Patent Publication No. 08-279371 Japanese Patent No. 2794009 Japanese Patent No. 2748705 International Publication No. 03/02955 Japanese Patent Laid-Open No. 2006-028438 Japanese Patent Laid-Open No. 2001-155539 Japanese Patent Laid-Open No. 2005-036265

However, as shown in the said patent document 1, in the method of forming an insulating adhesive agent on one side of a circuit connection member, when bump area narrows to less than 3000 micrometer <^2> , conduction in a circuit connection member is obtained in order to obtain stable connection resistance. It is necessary to increase the particles. As described above, when the conductive particles are increased, there is still room for improvement in terms of insulation between adjacent electrodes.

Moreover, as shown in the said patent document 2, in order to coat the whole surface of electroconductive particle with an insulating film in order to improve the insulation between adjacent electrodes, although the insulation between circuit electrodes becomes high, the electroconductivity of electroconductive particle There is a problem that it is easy to be lowered.

Moreover, as shown in the said patent documents 3, 4, in the method of covering the conductive particle surface with insulating magnetic particles, it is necessary to use resin magnetic particles such as acrylic due to the problem of adhesion between the magnetic particles and the conductive particles. have. In this case, the magnetic particles made of resin are melted at the time of thermocompression bonding of the circuits, and the conductive particles are brought into contact with both circuits so that conduction is established between the circuits. At this time, when the melted resin of the magnetic particles covered the surface of the conductive particles, it was found that the conductivity of the conductive particles tended to be low, as in the method of coating the entire surface of the conductive particles with an insulating coating. For this reason, as the insulating magnetic particles, those having relatively high hardness and high melting temperature, such as inorganic oxides, are suitable. For example, in the said patent document 4, the method of processing a silica surface with 3-isocyanate propyl triethoxysilane, and making the silica which has an isocyanate group in the surface, and the electroconductive particle which has an amino group in the surface are illustrated.

However, it is generally difficult to modify the surface of particles having a particle diameter of 500 nm or less with a functional group, and a problem that inorganic oxides such as silica aggregates during centrifugation and filtration performed after modifying the functional group is likely to occur. Moreover, in the method illustrated by the said patent document 4, it is difficult to control the coverage of insulating magnetic particle.

In addition, when the metal surface is treated with a compound having any one of a mercapto group, a sulfide group, and a disulfide group, the metal and the compound may be present if a small amount of non-metal such as nickel or an easily oxidizing metal such as copper is present on the metal. Reaction is difficult to proceed.

Moreover, although it became clear by the researches of the present inventors, when inorganic materials, such as silica, are coat | covered on a conductive particle, electroconductivity expresses by pressing and crushing the metal surface on a conductive particle. Therefore, since the silica destroys the conductive metal, if a substance other than a noble metal enters the conductive metal, migration characteristics tend to deteriorate.

Moreover, as shown in the said patent document 6, in recent years, the electroconductive particle of the type which performs gold plating on a nickel layer has become the mainstream, As such a conductive particle, there exists a subject that nickel elutes and produces migration. Moreover, when the thickness of gold plating is set to 40 nm or less, the tendency becomes remarkable.

Moreover, as shown in the said patent document 7, although the electrically-conductive particle coat | covered with the metal coating layer whose content of gold is 90 weight% or more is favorable in terms of reliability, it is high in cost. Therefore, the electrically-conductive particle provided with the metal coating layer with high gold content is hard to be practical, and there exists a tendency for lowering the gold content of a metal coating layer in recent years. On the other hand, the electroconductive particle provided with copper plating is excellent in electroconductivity and cost. However, in the electroconductive particle provided with copper plating, since migration is easy to generate | occur | produce, there exists a problem from a hygroscopic resistance point. Thus, attempts have been made to make up for the shortcomings of both (gold and copper), but neither is complete. For example, in the method shown in the said patent document 5, the shortcomings of both (gold and copper) cannot fully be compensated.

This invention is made | formed in view of the said subject, Comprising: It aims at providing the electrically-conductive particle which is low in cost, high in electroconductivity, and excellent in connection reliability between electrodes, without causing migration.

In order to achieve the above object, the conductive particles according to the first aspect of the present invention cover the core particles (resin fine particles) and the palladium having a phosphorus concentration of 1% by weight to 10% by weight and a thickness of 20 nm to 130 nm. With layers. That is, the electrically-conductive particle which concerns on 1st this invention is provided with the resin fine particle and the conductive layer formed in the surface of the resin fine particle, The conductive layer is a palladium layer containing phosphorus, The phosphorus concentration in a palladium layer is 1 weight% or more and 10 weight% It is% or less, and the thickness of a palladium layer is 20 nm or more and 130 nm or less, It is characterized by the above-mentioned. The feature of the present invention is that the palladium layer is directly formed on the surface of the resin fine particles. In other words, in this invention, it is preferable that metals (for example, nickel) other than palladium do not exist in the surface of resin fine particles. These features of the present invention are indispensable for achieving the following effects of the present invention.

In the said 1st this invention, since a palladium layer is soft, when connecting a pair of electrodes using the anisotropic conductive adhesive provided with the said electroconductive particle, a palladium layer is hard to be broken even after compressing an electroconductive particle. Therefore, it becomes possible to improve the electroconductivity of the electroconductive particle after compression, and the connection reliability between electrodes, and, at the same time, it becomes possible to prevent migration of palladium resulting from fracture of a palladium layer. In addition, palladium is inexpensive and practical in comparison with precious metals such as gold and platinum. Therefore, the conductive particles according to the first aspect of the present invention having a palladium layer are lower in cost than the conductive particles using only gold or platinum.

In the said 1st this invention, since the thickness of a palladium layer is 20 nm or more, it becomes possible to acquire sufficient electroconductivity.

In said 1st this invention, since the palladium layer contains 1 weight% or more and 10 weight% or less, since the hardness is high, it penetrates into the counter electrode surface and the electrically conductive film which has sufficient strength is obtained.

The conductive particles according to the second aspect of the present invention are disposed on the surface of the palladium layer and the palladium layer covering the core particles, the palladium layer having a phosphorus concentration of 1% by weight or more and 10% by weight or less and a thickness of 20 nm or more and 130 nm or less. The insulating particle which is 20-500 nm is provided.

When placing an anisotropically conductive adhesive (anisotropic conductive film) obtained by dispersing a plurality of the above conductive particles in an adhesive agent between a pair of electrodes, and connecting a pair of electrodes (thermal compression bonding), the longitudinal direction (the direction in which the pair of electrodes opposes) ), The whole conductive particles are compressed by a pair of electrodes. As a result, the insulating particles become lodged from the surface of the palladium layer toward the core particles, whereby the exposed palladium layer can be brought into contact with the pair of electrodes. That is, between a pair of electrodes is conductive through the palladium layer of electroconductive particle. On the other hand, in the horizontal direction (direction perpendicular to the direction in which the pair of electrodes opposes), the insulating particles are in contact with each other with the insulating particles included in the respective conductive particles between the adjacent conductive particles. Therefore, in the horizontal direction, insulation is maintained between the pair of electrodes and the electrode adjacent thereto.

In the second aspect of the present invention, since the palladium layer is ductile, it is possible to improve the conductivity of the conductive particles after compression and the connection reliability between the electrodes as in the first aspect of the present invention, and to prevent migration of palladium. It becomes possible. In addition, palladium is inexpensive and practical in comparison with precious metals such as gold and platinum. Therefore, the conductive particles according to the second invention having the palladium layer are lower in cost than the conductive particles using only gold or platinum.

In the said 2nd this invention, since the palladium layer whose thickness is 20 nm or more is provided as a conductive layer, it becomes possible to acquire sufficient electroconductivity.

In the said 1st and 2nd this invention, it is preferable that a palladium layer is a palladium layer of a reduction plating type. Thereby, the coverage of the palladium layer with respect to a core particle improves, and it becomes easy to improve the electroconductivity of electroconductive particle.

Further, when the palladium layer is a reduced plating palladium layer, a dense and homogeneous palladium layer can be formed on the resin fine particles, and it is possible to provide conductive particles with little exposure to the surface of the resin fine particles. Moreover, it is possible to set the thickness of a palladium layer arbitrarily according to the amount of plating liquid. That is, the thickness of the palladium layer can be controlled to the thickness as needed.

In the present invention, the components (elemental composition and phosphorus concentration of the conductive layer) in the conductive layer are preferably qualitatively and quantified by Energy Dispersive X-ray Spectroscopy (EDX).

In the said 1st and 2nd this invention, it is preferable that insulating particle is silica. The insulating particle containing silica is excellent in insulation, easy to control a particle diameter, and inexpensive. In addition, when silica is dispersed in water to form a water-soluble colloidal silica, the silica has a hydroxyl group on the surface thereof, and therefore, the bonding property with the palladium layer is excellent. In addition, the hydroxyl group on the silica surface is also excellent in bonding with a functional group formed on the surface of the palladium layer. Therefore, insulating particles containing silica can be firmly adsorbed onto the surface of the palladium layer or the gold layer.

According to the present invention, conductive particles can be provided that are low in cost, high in conductivity, and excellent in connection reliability between electrodes without causing migration.

1 is a schematic cross-sectional view of conductive particles according to a first embodiment of the present invention.
2 is a schematic cross-sectional view of conductive particles according to a second embodiment of the present invention.
Fig. 3 (a) is a schematic cross-sectional view of the anisotropic conductive adhesive having conductive particles according to the second embodiment of the present invention, and Figs. It is a schematic sectional drawing for demonstrating this.

EMBODIMENT OF THE INVENTION Hereinafter, the best form for implementing invention is demonstrated in detail. However, this invention is not limited to the following embodiment.

[First Embodiment]

(Conductive particles)

As shown in FIG. 1, the electrically-conductive particle 8a which concerns on 1st Embodiment of this invention coat | covers the core particle 11 and the whole core particle 11, The thickness is 20 nm or more and 130 nm or less, and phosphorus concentration is carried out. The palladium layer 12 which is 1 weight% or more and 10 weight% or less is provided. Below, the electrically-conductive particle 8a which concerns on 1st Embodiment is described as "parent particle 2a" as the case may be.

<Core Particles 11>

It is preferable that the particle diameter of the core particle 11 used by this invention is smaller than the minimum space | interval of the 1st electrode 5 and the 2nd electrode 7 of FIG. 3 mentioned later. In addition, when the particle diameter of the core particle 11 is fluctuate | varied in the height (electrode spacing) of an electrode, it is preferable that it is larger than the fluctuation of height (maximum spacing of electrodes). For these reasons, it is preferable that the particle diameter of the core particle 11 is 1-10 micrometers, It is more preferable that it is 1-5 micrometers, It is especially preferable that it is 2.0-3.5 micrometers.

The core particle in the conventional electrically-conductive particle is either particle | grains which consist only of metal, or particle | grains which consist of organic substance or an inorganic substance, The core particle 11 in this embodiment is resin fine particle which consists of resin.

There is no restriction | limiting in particular as the core particle 11 of organic substance, Polyolefin resin, such as acrylic resin, such as polymethylmethacrylate and polymethylacrylate, polyethylene, polypropylene, polyisobutylene, and polybutadiene, polystyrene, and divinyl Resin particles which consist of a benzene polymer, a divinylbenzene-styrene copolymer, a benzoguanamine formaldehyde resin, etc. are preferable.

<Palladium Layer 12>

Since the palladium layer 12 is ductile, it is difficult to cause metal cracking after compressing the conductive particles 8a, and hardly to cause migration due to metal cracking. Moreover, the palladium layer 12 is excellent in acid resistance and alkali resistance compared with a base metal or copper. In addition, since the palladium layer 12 is an alloy containing phosphorus, it is more excellent in acid resistance and alkali resistance. Therefore, it couples stably with functional groups, such as a mercapto group, a sulfide group, or a disulfide group mentioned later. In addition, palladium, gold, and platinum have the same tendency in bonding with these functional groups, and when these noble metals are compared in the same volume, palladium is the cheapest and most practical. Moreover, the palladium layer 12 is excellent in electroconductivity. For these reasons, the palladium layer 12 is preferable as the metal layer covering the core particles 11.

Although phosphorus concentration in the palladium layer 12 is 1 weight% or more and 10 weight% or less from a viewpoint of connection resistance, it is preferable that they are 1 weight% or more and 8 weight% or less, and it is more preferable that they are 1 weight% or more and 6 weight% or less. Moreover, compared with the pure palladium layer which does not contain phosphorus, the palladium layer containing phosphorus has high hardness (refer nonpatent literature 1 "surface description P651, Vol55, No10, 2004"). When the hardness of the surface of the palladium layer in contact with the electrode is high, the conductive particles are likely to be stuck to the electrode surface, penetrate through the oxidized electrode, and secure the conduction performance. On the other hand, when the content rate of phosphorus exceeds 10 weight%, the conduction resistance of a palladium layer is too big. Moreover, when the content rate of phosphorus exceeds 10 weight%, when forming the palladium layer 12 by plating, for example, palladium plating is hard to advance and the time required for a plating process becomes long.

The palladium layer 12 is preferably a reduced plating palladium layer. Thereby, the coverage of the palladium layer 12 with respect to the core particle 11 improves, and the electroconductivity of the electroconductive particle 8a improves more. The reducing agent for vaccinating phosphorus and alloying palladium preferably contains at least a reducing agent containing phosphorus such as hypophosphorous acid and salts thereof, phosphorous acid and salts thereof. As a reducing agent, if the said phosphorus containing reducing agent is included, another reducing agent may be included and it is not specifically limited. Even when it contains another reducing agent, it is known that phosphorus vacancies in a palladium film | membrane from a phosphorus containing reducing agent.

It is easy to control the plating thickness of the palladium layer 12 by using reduction plating. For example, since the plating thickness after precipitation can be calculated in advance from the palladium ion concentration contained in the plating liquid to be used, unnecessary palladium and reagents are not used, thereby reducing the cost.

Although the thickness of the palladium layer 12 is 20 nm or more and 130 nm or less, it is preferable that they are 20 nm or more and 100 nm or less, and it is more preferable that they are 20 nm or more and 80 nm or less. If the thickness of the palladium layer is less than 20 nm, sufficient conductivity cannot be obtained. On the other hand, when the thickness of the palladium layer 12 exceeds 130 nm, there exists a tendency for the elasticity of the whole core particle 11 to fall. When the elasticity of the entire mother particle 2a is lowered, when the conductive particles 8a are sandwiched between the pair of electrodes and crushed in the longitudinal direction, the palladium layer 12 is caused by the elasticity of the mother particle 2a. The effect of being sufficiently pressurized to the surface becomes difficult to be obtained. Therefore, there exists a tendency for the contact area of the palladium layer 12 and both electrodes to become small, and the effect of this invention which improves the connection reliability between electrodes becomes small. In addition, the thicker the palladium layer 12 is, the higher the cost is, which is not economically desirable, and the conductive layer of the conductive particles 8a sandwiched between a pair of electrodes and crushed in the longitudinal direction when mounted and pressed, that is, A crack may arise in the palladium layer 12, and there exists a tendency for the connection resistance between electrodes to rise.

(Analysis of Plating Layer)

An atomic absorption photometer can be used for component analysis of the palladium layer 12 which coat | covers the core particle 11 surface. For example, there exists a method of analyzing the liquid which melt | dissolved the palladium layer 12 by acid etc. using the atomic absorption photometer, and measuring and calculating metal ion concentration. In addition, the palladium layer 12 can also be analyzed using an ICP emission spectrometer. By using the ICP emission spectrometer, quantitative determination of phosphorus can be performed simultaneously with qualitative analysis. In addition, the phosphorus concentration in the palladium layer 12 can also be quantified using EDX. Moreover, as EDX measurement in low magnification obtains information from a plurality of particles, EDX measurement in high magnification is preferable.

[Second Embodiment]

Next, the electrically-conductive particle concerning the 2nd Embodiment of this invention, and the manufacturing method of an electrically-conductive particle are demonstrated. In addition, below, only the difference between 1st Embodiment and 2nd Embodiment mentioned above is demonstrated, and description is abbreviate | omitted about the matter which is common to both.

(Conductive particles)

As shown in FIG. 2, the conductive particles 8b according to the second embodiment include not only the core particles 11 and the palladium layer 12, but also a plurality of insulating particles 1 disposed on the surface of the palladium layer 12. ) Is different from the conductive particles 8a according to the first embodiment.

Insulating Particles (1)

It is preferable that the insulating particle 1 is an inorganic oxide. For example, when the insulating particle 1 is an organic compound, the insulating particle 1 deform | transforms in the manufacturing process of an anisotropically conductive adhesive, and there exists a tendency for the characteristic of the anisotropically conductive adhesive obtained to change easily.

As the inorganic oxide constituting the insulating particle 1, an oxide containing at least one element selected from the group consisting of silicon, aluminum, zirconium, titanium, niobium, zinc, tin, cerium, and magnesium is preferable. These oxides can be used individually or in mixture of 2 or more types. Further, among oxides containing the above-described elements as the inorganic oxide, the insulating property is excellent, and can control the particle size distribution of colloidal silica (SiO ₂₎ is most preferred.

As a commercial item of the insulating particle which consists of such an inorganic oxide (henceforth "inorganic oxide microparticles | fine-particles"), for example, a snortex, a snortex UP (manufactured by Nissan Chemical Industries, Ltd.), and a coutron PL series (Fuso Kagaku) Kogyo Co., Ltd.) etc. are mentioned.

The particle diameter of the inorganic oxide fine particles is preferably smaller than the resin fine particles. Although the average particle diameter of an inorganic oxide fine particle is 20-500 nm specifically, it is preferable that it is 30-400 nm, and it is more preferable that it is 40-350 nm. In addition, the particle diameter of an inorganic oxide fine particle is measured by the specific surface area conversion method or X-ray incineration scattering method by BET method. If the particle diameter is less than 20 nm, the inorganic oxide fine particles adsorbed to the mother particles 2a do not act as an insulating film, and there is a tendency to generate a short between the electrodes. On the other hand, when the particle size exceeds 500 nm, the electrode and the conductive layer (palladium layer 12) of the conductive particles 8b are difficult to contact when they are mounted and crimped, so that the connection resistance between the electrodes becomes high and good conductivity is obtained. There is a tendency not to lose.

(Method for Producing Conductive Particles)

The manufacturing method of the electrically-conductive particle 8a which concerns on 1st Embodiment of this invention is equipped with the process (S1) of forming the palladium layer 12 on the surface of the core particle 11. In the method for producing the conductive particles 8b according to the second embodiment of the present invention, after step S1, the surface of the palladium layer 12 is treated with a compound having any one of a mercapto group, a sulfide group, or a disulfide group. To form a functional group on the surface of the palladium layer 12, to process (S3) the surface of the palladium layer on which the functional group is formed with a polymer electrolyte, and to form a functional group, The step (S4) of immobilizing the insulating particle 1 by chemisorption on the surface of the palladium layer 12 is provided. In addition, below, the case where the insulating particle 1 is an inorganic oxide fine particle in which the hydroxyl group was formed in the surface is demonstrated.

<S1>

First, the palladium layer 12 is formed on the surface of the core particle 11, and the mother particle 2a (conductive particle 8a which concerns on 1st Embodiment) is obtained. As its specific method, the plating by palladium is mentioned, for example. In this plating process, after degreasing the surface of the core particle 11 with alkali etc., it neutralizes with an acid and performs surface adjustment of the core particle 11. After that, a palladium catalyst is provided and it is good to perform reduction type electroless palladium plating with the phosphorus containing reducing agent mentioned above. As a composition of a reduced type electroless palladium plating liquid, it is preferable to add (1) water-soluble palladium salt like palladium sulfate, (2) reducing agent, (3) complexing agent, and (4) pH adjuster. As a method of adjusting the phosphorus concentration in the palladium layer 12 to 1 weight% or more and 10 weight% or less, the method of adjusting the component shown to (1)-(4) which comprises the palladium plating liquid shown above is used, for example. do. In particular, the method of controlling phosphorus concentration in a palladium plating liquid, such as a method of selecting a reducing agent containing phosphorus, a method of adjusting the amount of the reducing agent, a method of controlling the pH of the plating reaction, a method of adjusting the plating temperature, etc. may be mentioned. have. Moreover, even if it is a method of adjusting the kind and concentration of a complexing agent, the phosphorus concentration can be adjusted. Especially, since the reaction control is excellent, the method of controlling pH of a plating reaction is used preferably. Although the method shown above may be used independently, in combination with each other, adjustment of phosphorus concentration is easy and control of stability of a plating liquid is also easy.

<S2>

In the case of forming the conductive particles 8b according to the second embodiment, any one of the mercapto group, sulfide group, or disulfide group which forms a coordination bond with respect to palladium is further formed on the surface of the palladium layer 12. The compound is treated with. As a result, a functional group is formed on the surface of the palladium layer 12.

Specifically as a compound used for the surface treatment of the palladium layer 12, mercaptoacetic acid, 2-mercaptoethanol, methyl mercaptoacetic acid, mercaptosuccinic acid, thioglycerine, cysteine, etc. are mentioned. As a functional group formed in the surface of the palladium layer 12 processed with these compounds, a hydroxyl group, a carboxyl group, an alkoxyl group, or the alkoxycarbonyl group is mentioned.

Palladium is less likely to react with thiol groups (mercapto groups), whereas nonmetals such as nickel are less likely to react with thiol groups. Therefore, the palladium particles (core particles 11 coated with palladium layer 12) of the present embodiment are more likely to react with thiol groups than conventional nickel / gold particles (core particles coated with nickel layer and gold layer). In addition, when the thickness of gold is 30 nm or less, the nickel / gold particles tend to have a higher nickel ratio on the particle surface.

As a specific method of treating the surface of the palladium layer 12 with the above compound, for example, palladium particles in a liquid obtained by dispersing a compound such as mercaptoacetic acid in about 10 to 100 mmol / l in an organic solvent such as methanol and ethanol are dispersed. A method of dispersing is mentioned.

<S3, S4>

Next, after treating the surface of the palladium layer 12 in which the functional group was formed with the polymer electrolyte, the insulating particles 1 are chemisorbed onto the surface of the palladium layer 12.

The surface potential (zeta potential) of the palladium layer 12 having a functional group such as a hydroxyl group, a carboxyl group, an alkoxyl group, or an alkoxycarbonyl group is usually negative if the pH is a neutral region. On the other hand, since the surface of the insulating particle 1 adsorbed on the surface of the palladium layer 12 in the subsequent step is made of an inorganic oxide having a hydroxyl group, the surface potential of the insulating particle 1 is also usually negative. As described above, the insulating particles 1 having a negative surface potential tend to be difficult to adsorb around the palladium layer 12 having a negative surface potential. Therefore, by treating the surface of the palladium layer 12 with the polymer electrolyte, the surface of the palladium layer 12 can be easily covered with the insulating particles 1.

As a method of adsorbing the insulating particles 1 on the surface of the palladium layer 12 after treatment with the polymer electrolyte, a method of alternately laminating the polymer electrolyte and the inorganic oxide on the surface of the palladium layer 12 is preferable. More specifically, by carrying out the following steps (1) and (2) sequentially, the mother particle 2a, ie, the conductive particle 8b, whose part of the surface is covered with an insulating coating film in which the polymer electrolyte and the inorganic oxide fine particles are laminated. Can be prepared.

Step (1): The mother particles 2a having functional groups on the surface of the palladium layer 12 are dispersed in the polymer electrolyte solution, and the polymer electrolyte is adsorbed on the surface of the palladium layer 12, followed by the mother particles 2a. Rinse the process.

Step (2): After rinsing the mother particles 2a in a dispersion solution of the inorganic oxide fine particles and adsorbing the inorganic oxide particles on the surface (palladium layer 12) of the mother particles 2a, the mother particles 2a Rinsing).

That is, in step (1), a polymer electrolyte thin film is formed on the surface of the mother particle 2a, and in step (2), inorganic oxide fine particles are chemically adsorbed on the surface of the mother particle 2a through the polymer electrolyte thin film. Immobilize. By using this polymer electrolyte thin film, the surface of the mother particle 2a can be uniformly covered with inorganic oxide fine particles without a defect. When the circuit electrodes are connected using an anisotropic conductive adhesive using the conductive particles obtained through the steps (1) and (2), insulation is secured even when the circuit electrode intervals are narrow, and the connection resistance is between the electrodes to be electrically connected. Low and good.

The method having the above steps (1) and (2) is called a layer-by-layer assembly. The alternate lamination method is This is a method for forming an organic thin film published in 1992 by G. Decher et al. (See Thin Solid Films, 210/211, p831 (1992)).

In this alternating stacking method, a polycation adsorbed by electrostatic attraction on a substrate by alternately immersing the substrate in an aqueous solution of a polymer electrolyte (poly cation) having a positive charge and a polymer electrolyte (poly anion) having a negative charge; A group of poly anions are laminated to obtain a composite film (alternatively laminated film).

In the alternate lamination method, since the charge of the material formed on the substrate due to the electrostatic attraction and the material having the opposite charge in the solution are grown by attracting each other, the adsorption proceeds and neutralization of the charge causes further adsorption. This will not happen. Therefore, when a certain saturation point is reached, the film thickness no longer increases.

Lvov et al. Reported a method of applying an alternate lamination method to fine particles and using a fine particle dispersion of silica, titania, and ceria to alternately laminate a polymer electrolyte having an opposite charge to the surface charge of the fine particles (Langmuir , Vol. 13, (1997) p6195-6203).

With this method, fine particles of silica having a negative surface charge and polydiallyldimethylammonium chloride (PDDA) or polyethyleneimine (PEI) or the like, which are poly cations having opposite charges, are alternately laminated, thereby producing fine particles of silica and a polymer. It is possible to form a fine particle laminated thin film in which electrolytes are alternately laminated.

In the manufacturing method of the electrically-conductive particle 8b which concerns on 2nd Embodiment, after immersing a mother particle 2a in the dispersion liquid of a polymer electrolyte solution or an inorganic oxide fine particle, it immersed in the microparticle dispersion liquid or polymer electrolyte solution which has a counter electric charge. Before doing so, it is preferable to wash away the excess polymer electrolyte solution or the dispersion of the inorganic oxide fine particles from the mother particles 2a by rinsing only with a solvent.

Since the polymer electrolyte and the inorganic oxide fine particles adsorbed to the mother particles 2a are electrostatically adsorbed onto the mother particles 2a surface, they do not peel off from the mother particles 2a surface in this rinsing step. However, when excess polymer electrolyte or inorganic oxide fine particles which are not adsorbed by the mother particles 2a are contained in a solution having opposite charges to them, cations and anions are mixed in the solution, and the polymer electrolyte and the inorganic oxide fine particles are aggregated. Or precipitation may occur. This problem can be prevented by rinsing.

Examples of solvents used for rinsing include water, alcohols, acetone, and the like, and ion exchange water (so-called ultrapure water) having a specific resistance of 18 MΩ? Cm or more is generally easy to remove excess polymer electrolyte solution or dispersion of inorganic oxide fine particles. Is used.

The polymer electrolyte solution is obtained by dissolving a polymer electrolyte in water or a mixed solvent of water and a water-soluble organic solvent. Examples of the water-soluble organic solvent that can be used include methanol, ethanol, propanol, acetone, dimethylformamide, acetonitrile and the like.

As the polymer electrolyte, a polymer which is ionized in an aqueous solution and has a functional group having a charge in the main chain or the side chain can be used. In this case, it is preferable to use a poly cation.

As a poly cation, what has a positively charged functional group like polyamines, for example, polyethyleneimine (PEI), polyallylamine hydrochloride (PAH), polydiallyldimethylammonium chloride (PDDA), polyvinyl Pyridine (PVP), polylysine, polyacrylamide and copolymers containing at least one thereof can be used.

Among the polymer electrolytes, polyethyleneimine has a high charge density and a strong bonding force. Among these polymer electrolytes, alkali metal (Li, Na, K, Rb, Cs) ions and alkaline earth metal (Ca, Sr, Ba, Ra) ions, halide ions (fluorine ions, chloride ions) in order to avoid electromigration or corrosion. , Bromine ions, and iodine ions) are preferred.

All of these polymer electrolytes are water-soluble or soluble in a mixture of water and an organic solvent, and the molecular weight of the polymer electrolyte can not be determined uniformly depending on the type of polymer electrolyte used, but generally about 500 to 200,000 is preferable. Do. In addition, the concentration of the polymer electrolyte in the solution is generally preferably about 0.01 to 10% by weight. In addition, the pH of the polymer electrolyte solution is not particularly limited.

The coverage of the inorganic oxide fine particles can be controlled by adjusting the type, molecular weight, or concentration of the polymer electrolyte thin film covering the mother particles 2a.

Specifically, when a polymer electrolyte thin film having a high charge density, such as polyethyleneimine, is used, the coverage of inorganic oxide fine particles tends to increase, and when a polymer electrolyte thin film having a low charge density, such as polydiallyldimethylammonium chloride, is used, There exists a tendency for the coverage of inorganic oxide fine particles to become low.

When the molecular weight of the polymer electrolyte is large, the coverage of the inorganic oxide fine particles tends to be high, and the inorganic oxide fine particles can be firmly adsorbed onto the palladium layer 12. In view of the bonding force, the molecular weight of the polymer electrolyte is preferably 10,000 or more. On the other hand, when the molecular weight of the polymer electrolyte is small, the coverage of the inorganic oxide fine particles tends to be low.

When the polymer electrolyte is used at a high concentration, the coverage of the inorganic oxide fine particles tends to be high, and when the polymer electrolyte is used at a low concentration, the coverage of the inorganic oxide fine particles tends to be low. When the coverage of the inorganic oxide fine particles is high, the insulation tends to be high and the conductivity is poor. When the coverage of the inorganic oxide fine particles is low, the conductivity tends to be high and the insulation is bad.

It is preferable that only one inorganic oxide fine particle is coated. When lamination | multilayer lamination, control of lamination amount becomes difficult. The coverage of the surface of the palladium layer 12 by the inorganic oxide fine particles is preferably in the range of 20 to 100%, more preferably in the range of 30 to 60%.

It is preferable that the concentration of alkali metal ions and alkaline earth metal ions in the dispersion solution of the inorganic oxide fine particles is 100 ppm or less. Thereby, it becomes easy to improve the insulation reliability between adjacent electrodes. Moreover, as inorganic oxide microparticles | fine-particles, inorganic oxide microparticles | fine-particles manufactured by the hydrolysis reaction of a metal alkoxide, what is called a sol-gel method, are preferable.

In particular, as inorganic oxide fine particles, water dispersion colloidal silica (SiO ₂ ) is preferable. Since water-disperse colloidal silica has a hydroxyl group on the surface, it is preferable for inorganic oxide fine particles from the point of being excellent in binding property with the mother particle 2a, making it easy to make a particle size uniform, and inexpensive.

In general, hydroxyl groups are known to form strong bonds with hydroxyl groups, carboxyl groups, alkoxyl groups, and alkoxycarbonyl groups. Specific examples of the bond between the hydroxyl group and these functional groups include covalent bonds and hydrogen bonds by dehydration condensation. Therefore, the inorganic oxide fine particles having a hydroxyl group on the surface can be firmly adsorbed to the palladium layer 12 (the surface of the parent particle 2a) on which functional groups such as a hydroxyl group, a carboxyl group, an alkoxyl group and an alkoxycarbonyl group are formed.

The hydroxyl group on the surface of the inorganic oxide fine particles can be modified with an amino group, a carboxyl group, or an epoxy group with a silane coupling agent or the like, which is difficult when the particle size of the inorganic oxide is 500 nm or less. Therefore, it is preferable to coat the mother particle 2a with the inorganic oxide fine particles without modifying the functional group.

Bonding of the insulating particle 1 and the mother particle 2a can be strengthened further by heat-drying the electrically conductive particle 8b completed as mentioned above. The reason why the bonding force is increased is, for example, a chemical bond between a functional group such as a carboxyl group on the surface of the palladium layer 12 and a hydroxyl group on the surface of the insulating particle 1, or a carboxyl group and insulating particle on the surface of the palladium layer 12. The dehydration condensation of the amino group of the surface of (1) is mentioned. Moreover, when heating is performed in a vacuum, it is preferable from the viewpoint of metal rust prevention. Moreover, also when the outermost surface of a mother particle is a gold layer, like the case of the palladium layer 12, heat drying can further strengthen bond | coupling of insulating particle and a mother particle.

It is preferable that the temperature of heat drying is 60-200 degreeC, and it is preferable that heating time is 10-180 minutes. When the temperature is less than 60 ° C. or when the heating time is less than 10 minutes, the insulating particles 1 are likely to peel off from the mother particles 2a, when the temperature exceeds 200 ° C. or when the heating time exceeds 180 minutes. It is not preferable because the mother particle 2a is easily deformed.

(Observation of particles)

A scanning electron microscope (SEM) can be used for observation of the plating film (palladium layer) which coat | covers resin microparticles | fine-particles, the insulating particle arrange | positioned on a plating film, etc. By the image, the arrangement position, the number, etc. of the plating film surface and insulating fine particles can be confirmed.

(Anisotropic Conductive Adhesive)

The anisotropically conductive adhesive agent 40 is obtained by disperse | distributing the electrically-conductive particle 8b produced as mentioned above to the adhesive agent 3 as shown to FIG. 3 (a). The manufacturing method of the bonded structure 42 using this anisotropically conductive adhesive agent 40 was shown to FIG. 3 (b), (c). In addition, in FIG.3 (a), FIG.3 (b), FIG.3 (c), the electroconductive particle 8b is described as electroconductive particle 8. In FIG. In addition, the palladium layer 12 with which the electroconductive particle 8 is equipped is abbreviate | omitted for the simplification of drawing.

As shown in FIG.3 (b), the 1st board | substrate 4 and the 2nd board | substrate 6 are prepared, and the anisotropic conductive adhesive 40 is arrange | positioned between them. At this time, the first electrode 5 included in the first substrate 4 and the second electrode 7 included in the second substrate 6 face each other. Then, the 1st board | substrate 4 and the 2nd board | substrate 6 are laminated | stacked while pressing-heating in the direction which the 1st electrode 5 and the 2nd electrode 7 oppose, and connection shown in FIG.3 (c). Obtain the structure 42.

In this way, when the connection structure 42 is manufactured, the insulating particle 1 is embedded in the mother particle 2 in the longitudinal direction, and the first electrode 5 and the second electrode 7 are formed on the surface of the mother particle 2 ( Conductive through the palladium layer, and the insulating direction is maintained by interposing the insulating magnetic particles 1 between the mother particles.

Although anisotropically conductive adhesive for COG has recently been required to have insulation reliability at a narrow pitch of 10 μm, the use of the anisotropically conductive adhesive 40 according to the present embodiment improves the insulation reliability at a narrow pitch of 10 μm. It becomes possible.

As the adhesive 3 used for the anisotropic conductive adhesive 40, a mixture of a thermally reactive resin and a curing agent is used, and specifically, a mixture of an epoxy resin and a latent curing agent is preferable.

Examples of the epoxy resin include bisphenol-type epoxy resins derived from epichlorohydrin and bisphenols A, F, AD and the like, and skeletons containing epichlorohydrin and epoxy novolac resins derived from phenol novolac or cresol novolac and naphthalene rings. It is possible to use various epoxy compounds having two or more glycidyl groups in one molecule, such as naphthalene-based epoxy resins, glycidylamines, glycidyl ethers, biphenyls, and alicyclic compounds, alone or in combination of two or more thereof. It is possible.

As these epoxy resins, it is preferable to use high purity articles which reduced impurity ions (Na ⁺ , Cl ^- etc.), hydrolyzable chlorine, etc. to 300 ppm or less. This makes it easy to prevent electromigration.

Examples of the latent curing agent include imidazole series, hydrazide series, boron trifluoride-amine complexes, sulfonium salts, amineimides, salts of polyamines, dicyandiamides, and the like. In addition, energy ray curable resins, such as a mixture of a radical reactive resin and an organic peroxide, and an ultraviolet-ray, are used for an adhesive agent.

In the adhesive 3, butadiene rubber, acrylic rubber, styrene-butadiene rubber, silicone rubber, etc. can be mixed in order to reduce the stress after adhesion or to improve the adhesiveness.

In addition, as adhesive 3, a paste form or a film form is used. In order to make an adhesive into a film form, it is effective to mix | blend thermoplastic resins, such as a phenoxy resin, a polyester resin, and a polyamide resin. These film-forming polymers are also effective for stress relaxation at the time of curing of a reactive resin. In particular, when the film-forming polymer has a functional group such as a hydroxyl group, it is more preferable because the adhesiveness is improved.

Formation of the film is liquefied by dissolving or dispersing an adhesive composition comprising an epoxy resin, an acrylic rubber, a latent curing agent, and a film-forming polymer in an organic solvent, applying the film on a peelable substrate, and below the active temperature of the curing agent. By removing it. As an organic solvent used at this time, the mixed solvent of an aromatic hydrocarbon type and an oxygen containing system is preferable at the point which improves the solubility of a material.

The thickness of the anisotropically conductive adhesive 40 is relatively determined in consideration of the particle diameter of the conductive particles 8 and the characteristics of the anisotropically conductive adhesive 40, but is preferably 1 to 100 μm. If it is less than 1 micrometer, sufficient adhesiveness will not be obtained, and if it exceeds 100 micrometers, since a large amount of electroconductive particle is required in order to acquire electroconductivity, it is unrealistic. For this reason, the thickness is more preferably 3 to 50 µm.

Examples of the first substrate 4 or the second substrate 6 include glass substrates, tape substrates such as polyimide, bare chips such as driver ICs, rigid package substrates, and the like.

As mentioned above, although the conductive particle which concerns on this invention, and the manufacturing method of the conductive particle were described in detail about preferable embodiment, this invention is not limited to the said embodiment. For example, the electroconductive particle 8a which concerns on 1st Embodiment coat | covers the surface of the palladium layer 12 and the palladium layer 12 which coat | cover the surface of the resin fine particle 11, the resin fine particle 11, and the like. Another conductive layer (for example, a gold layer) may be provided. Moreover, the electroconductive particle 8b which concerns on 2nd Embodiment has the other which coat | covers the surface of the palladium layer 12 and the palladium layer 12 which coat | cover the surface of the resin fine particle 11, the resin fine particle 11, and the other. You may be equipped with a conductive layer (for example, a gold layer) and the some insulating particle 1 arrange | positioned at the surface of a conductive layer.

[Example]

Hereinafter, the present invention will be described by way of examples.

(Parental parent 1)

3 g of crosslinked polystyrene particles (resin fine particles) having an average particle diameter of 3.5 µm were neutralized with an acid after alkali degreasing. The resin fine particles were added to 100 ml of the cationic polymer liquid adjusted to pH 6.0, stirred at 60 ° C. for 1 hour, filtered through a membrane filter (manufactured by Millipore) with a diameter of 3 μm, and washed with water. Water fine resin after water washing was added to 100 mL of palladium catalysis liquid containing 8 weight% of Atotech Neogant 834 (Atotech Japan Co., Ltd. brand name) which is a palladium catalyst, and it stirred at 35 degreeC for 30 minutes, and then diameter 3 It filtered with the membrane filter (made by Millipore), and washed with water. Resin fine particles were repeatedly added to the palladium catalyst solution, and a sufficient amount of palladium catalyst was applied to the surface of the resin fine particles. In addition, a "palladium catalyst" is a catalyst for forming a palladium layer on the resin fine particle surface, and is not the palladium layer itself in this invention.

Next, the resin fine particles after washing with water were added to 3 g / L sodium hypophosphite solution adjusted to pH 6.0 to obtain resin fine particles (resin core particles) with activated surfaces. Thereafter, the surface-activated resin fine particles were immersed in distilled water and ultrasonically dispersed.

The above liquid was filtered with a membrane filter (manufactured by Millipore) having a diameter of 3 µm, and the resin whose surface was activated under the conditions of 50 ° C in APP (Ishihara Yakuhin Kogyo Co., Ltd., brand name) which is an electroless palladium plating solution. The fine particles were immersed, and 20 nm of electroless Pd plating was performed on the surface of the resin fine particles. It is known that APP which is an electroless palladium plating liquid contains phosphorus-containing substances, such as hypophosphorous acid and its salt, phosphoric acid, and its salt which are reducing agents as a main component.

Then, it filtered with the membrane filter (made by Millipore) of diameter 3 micrometers, and washed with water three times. After vacuum drying at 40 ° C. for 7 hours, the agglomeration was released by disintegration to prepare mother particle 1 having a 20 nm thick palladium layer on the resin fine particles.

(Parent 2)

Instead of performing electroless Pd plating using the electroless palladium plating solution APP described above, a resin having a surface activated under a 50 ° C condition on a melt plate Pal6700 (product name manufactured by Meltex Co., Ltd.) which is an electroless palladium plating solution. A mother particle 2 having a palladium layer having a thickness of 40 nm was prepared on the resin core particles in the same manner as the mother particle 1 except that the fine particles were immersed and electroless palladium plating was performed at pH 8. Melplate Pal6700, an electroless palladium plating solution, is known to contain phosphorus-containing substances such as hypophosphorous acid and its salts, phosphoric acid and salts thereof as the main component.

(Parent 3)

A palladium layer of 80 nm thickness was formed on the resin core particles in the same manner as the mother particle 2, except that sodium hypophosphite was added to the electroless palladium plating solution melt plate Pal6700 (product name manufactured by Meltex Co., Ltd.). The mother particle 3 which had was produced.

(Parent 4)

A palladium catalyst was applied in the same manner as the parent particle 1, and the activated resin fine particles were dispersed in a 70 ° C bath in which 50 g / L of sodium citrate was dissolved. Using the metering pump, the plating liquid a and the plating liquid b were added simultaneously and in parallel at 10 ml / min, and electroless palladium plating was performed on the resin fine particles. As the plating solution a, palladium: 20 g / L, sodium citrate: 50 g / L, ethylenediamine 20 g / L were mixed, and the liquid adjusted to pH = 6.0 was used. In addition, in the plating liquid a, palladium is melt | dissolved in the state of an ion and a complex, and said amount "20 g / L" of palladium is a weight conversion value as metal palladium. As the plating solution b, sodium hypophosphite: 1.2 mol / L was mixed, and the liquid adjusted to pH = 6.0 with sodium hydroxide was used. The thickness of the electroless palladium layer formed on the resin fine particle surface was adjusted by the analysis by the atomic absorption photometer of the sampled particle. The addition of the electroless plating solution was stopped when the thickness of the electroless palladium layer became 130 nm. After completion | finish of addition, it waited for generation | occurrence | production of foam | bubble to stop, and performed filtration and water washing. PH was 6.0 when reaction stopped. The parent particle 4 which has the 130 nm-thick electroless palladium layer on the resin core particle was produced by the above method. The obtained mother particle 4 was gray.

(Parent 5)

A palladium catalyst was applied in the same manner as the parent particle 1, and the activated resin fine particles were dispersed in a 70 ° C bath in which 50 g / L of sodium citrate was dissolved. Using a metering pump, the plating solution c and the plating solution d were added simultaneously and in parallel at 4 ml / min, and electroless palladium plating was performed on the resin fine particles. As the plating solution c, palladium: 20 g / L, sodium citrate: 80 g / L, ethylenediamine: 20 g / L were mixed, and the liquid adjusted to pH = 5.0 was used. As the plating solution d, sodium hypophosphite: 2.4 mol / L was mixed, and the liquid adjusted to pH = 5.0 with sodium hydroxide was used. The thickness of the electroless palladium layer formed on the resin fine particle surface was adjusted by the analysis by the atomic absorption photometer of the sampled particle. The addition of the electroless plating solution was stopped when the thickness of the electroless palladium layer became 80 nm. After completion | finish of addition, it waited for generation | occurrence | production of foam | bubble to stop, and filtered and washed with water. PH was 4.8 when reaction was stopped. The parent particle 5 which has the 80 nm-thick electroless palladium layer on the resin core particle was produced by the above method. The obtained mother particle 5 was gray.

(Parent 6)

A palladium catalyst was applied in the same manner as the parent particle 1, and the activated resin fine particles were dispersed in a 70 ° C bath in which 20 g / L of sodium tartrate was dissolved. Using the metering pump, the plating solution e and the plating solution f were added simultaneously and in parallel at 15 ml / min, and the addition electroless nickel plating was performed on the resin fine particles. As the plating solution e, a liquid obtained by mixing nickel: 224 g / L and sodium tartrate: 20 g / L was used. As the plating solution f, a liquid obtained by mixing sodium hypophosphite: 226 g / L and sodium hydroxide: 85 g / L was used. The film thickness of nickel was adjusted by the analysis by the atomic absorption photometer of the sampled particle. The addition of the electroless plating solution was stopped when the nickel film thickness became 40 nm. After completion | finish of addition, it waited for generation | occurrence | production of foam | bubble to stop, and filtered and washed with water. When the reaction was stopped, the pH was 6.2 and the fine particles were gray. Next, the resin fine particles after electroless nickel plating were immersed in 50 degreeC conditions of APP (Ishihara Yakuching Kogyo Co., Ltd. product) which is an electroless palladium plating liquid, and electroless palladium plating was performed.

The above liquid was filtered through a membrane filter (manufactured by Millipore) with a diameter of 3 µm, and washed with water three times. Thereafter, vacuum drying was performed at 40 ° C. for 7 hours to loosen the agglomeration by disintegration. This obtained the mother particle 6 which has a resin fine particle, the 40 nm-thick electroless nickel layer which coat | covers the resin fine particle surface, and the 40 nm electroless palladium layer which coat | covers the surface of an electroless nickel layer.

(Parent 7)

Instead of electroless palladium plating, nickel formed by HGS-500 (product name manufactured by Hitachi Kasei Kogyo Co., Ltd.), which is an electroless gold plating solution, in a solution bathed at 80 ° C. in the same manner as in the case of the mother particles 6 The plated resin fine particles were immersed, the substitution gold plating was performed, and filtration and water washing were performed. Subsequently, the particles were immersed in a solution in which HGS-2000 (the product name of Hitachi Kasei Kogyo Co., Ltd.), an electroless gold plating solution, was dried at 60 ° C., and filtered and washed with water. Except these matters, by treating in the same manner as the parent particle 6, the mother particle 7 having the resin fine particles, a 40 nm thick nickel layer covering the resin fine particles, and a 40 nm thick Au layer covering the nickel layer surface Was produced.

(Insulation coating processing)

Next, the conductive particles 1 to 7 were produced using the mother particles 1 to 7 obtained above. The insulating coating treatment which adsorb | sucks the silica fine particle which is insulating particle on the surface of a mother particle was performed by the method disclosed by Unexamined-Japanese-Patent No. 2008-120990. In addition, in the Example, for the convenience of description, the mother particle provided with the insulating particle on the surface is described as "conductive particle", and is distinguished from the mother particle which does not have the insulating particle on the surface. And all the electrically-conductive particles 1-5 mentioned later correspond to the electrically-conductive particle which concerns on this invention.

(Conductive Particle 1)

8 mmol of mercaptoacetic acid was dissolved in 200 ml of methanol to prepare a reaction solution.

Next, 1 g of the mother particle 1 was added to the reaction solution, and stirred at a room temperature of 25 ° C. with a three-way motor and a stirring blade having a diameter of 45 mm for 2 hours. After wash | cleaning with methanol, the mother particle 1 was filtered with the membrane filter (made by Millipore) of diameter 3 micrometers, and the mother particle 1 which has a carboxyl group on the surface was obtained.

Next, a 30% aqueous polyethyleneimine solution (manufactured by Wako Junyaku Kogyo Co., Ltd.) having a molecular weight of 70000 was diluted with ultrapure water to obtain a 0.3 wt% aqueous polyethyleneimine solution. 1 g of the mother particles 1 having the carboxyl group was added to a 0.3 wt% polyethyleneimine aqueous solution and stirred at room temperature for 15 minutes.

Thereafter, the mother particles 1 were filtered with a membrane filter (manufactured by Millipore) having a diameter of 3 µm, and placed in 200 g of ultrapure water and stirred at room temperature for 5 minutes. Furthermore, the mother particle 1 was filtered with the membrane filter (made by Millipore) of diameter 3 micrometers, and the polyethyleneimine which was not adsorbed to the mother particle 1 was removed by washing twice with 200 g of ultrapure water on the said membrane filter.

Next, the dispersion liquid of colloidal silica which is insulating particle (mass concentration 20%, Fuso Chemical Co., Ltd. make, product name: Cuatlon PL-3, average particle diameter 35nm) was diluted with ultrapure water, and 0.1 weight% silica dispersion solution. Got. The mother particle 1 after the process in the said polyethyleneimine was put into 0.1 weight% silica dispersion solution, and it stirred at room temperature for 15 minutes.

Next, the mother particle 1 was filtered with the membrane filter (made by Millipore) of diameter 3 micrometers, it put in ultrapure water 200g, and stirred at room temperature for 5 minutes. Furthermore, the mother particle 1 was filtered with the membrane filter (made by Millipore) of 3 micrometers in diameter, and wash | cleaned twice with 200 g of ultrapure water on the said membrane filter, and the silica which did not adsorb to the mother particle 1 was removed. Thereafter, drying was carried out at 80 ° C. for 30 minutes, and heat drying was performed at 120 ° C. for 1 hour to prepare conductive particles 1 having silica (magnetic particles) adsorbed on the surface of mother particle 1.

(Conductive particle 2)

The mother particle 2 was used instead of the mother particle 1, and PL-7 (mass concentration 20%, Fuso Chemical Co., Ltd. make, product name: Cuatron PL-7, average particle diameter instead of PL-3 as colloidal silica dispersion liquid). Except having used 75 nm), the conductive particle 2 was produced by the method similar to the conductive particle 1.

(Conductive particle 3)

The mother particle 3 was used instead of the mother particle 1, and PL-13 (mass concentration 20%, Fuso Chemical Co., Ltd. make, product name: Cuatron PL-13, average particle diameter instead of PL-3 as colloidal silica dispersion liquid). Except having used 130 nm), the conductive particle 3 was produced by the method similar to the conductive particle 1.

(Conductive particle 4)

The mother particle 4 was used instead of the mother particle 1, and PL-20 (mass concentration 20%, Fuso Chemical Co., Ltd. make, product name: Cuatron PL-20, average particle diameter instead of PL-3 as colloidal silica dispersion liquid). Except having used (200n) m), the electrically-conductive particle 4 was produced by the method similar to the electrically-conductive particle 1.

(Conductive Particle 5)

The mother particle 5 was used instead of the mother particle 1, and PL-50 (mass concentration 20%, Fuso Chemical Co., Ltd. make, product name: Cuatron PL-50, average particle diameter instead of PL-3 as colloidal silica dispersion liquid). Except having used 500 nm), the electrically-conductive particle 5 was produced by the method similar to the electrically-conductive particle 1.

(Conductive Particle 6)

Except having used the parent particle 6 instead of the parent particle 3, the electrically conductive particle 6 was produced by the method similar to the electrically conductive particle 3.

(Conductive Particle 7)

A conductive particle 7 was produced in the same manner as the conductive particle 3 except that the mother particle 7 was used instead of the mother particle 3.

(Example 1)

<Production of Adhesive Solution>

Copolymer of 10 g of phenoxy resins (manufactured by Union Carbide, trade name: PKHC) and acrylic rubber (40 parts of butyl acrylate, 30 parts of ethyl acrylate, 30 parts of acrylonitrile, 3 parts of glycidyl methacrylate, molecular weight: 850,000) 7.5 g was dissolved in 30 g of ethyl acetate to obtain a 30 wt% solution.

Next, 30 g of a liquid epoxy (epoxy equivalent 185, manufactured by Asahi Kasei Epoxy Co., Ltd., product name: Novacure HX-3941) containing a microcapsule latent curing agent was added to this solution, and stirred to prepare an adhesive solution.

4 g of conductive particles 1 prepared above were dispersed in 10 g of ethyl acetate.

The particle dispersion was dispersed in the adhesive solution so that the conductive particles 1 became 37% by weight with respect to the adhesive, and the solution was applied to the separator (silicon-treated polyethylene terephthalate film, 40 μm thick) with a roll coater, It dried for 10 minutes and produced the 25-micrometer-thick anisotropic conductive adhesive film.

Next, using the produced anisotropic conductive adhesive film, a chip (1.7 × 17 mm, thickness: 0.5 mm) with gold bumps (area: 30 × 90 μm, space 10 μm, height: 15 μm, bump number 362) and The bonded structure sample of the glass substrate (thickness: 0.7 mm) with an ITO circuit was produced with the following method.

First, after attaching an anisotropic conductive adhesive film (2x19 mm) to a glass substrate with an ITO circuit at 80 ° C and 0.98 MPa (10 kgf / cm ² ), the separator is peeled off, and the bump of the chip and the glass substrate with the ITO circuit are The position alignment of was performed. Subsequently, heating and pressurization were performed from the upper side of a chip | tip on 190 degreeC and the conditions of 5 second, and this connection was made and the sample was obtained.

(Example 2)

Using the conductive particles 2 instead of the conductive particles 1, the proportion of the conductive particles 2 added to the adhesive was adjusted so that the number of conductive particles dispersed per unit area of the anisotropic conductive adhesive film produced in Example 2 was the same as in Example 1. A sample was produced in the same manner as in Example 1 except for the one.

(Example 3)

A sample was produced in the same manner as in Example 2 except that Conductive Particle 3 was used instead of Conductive Particle 2.

(Example 4)

A sample was produced in the same manner as in Example 2 except that Conductive Particle 4 was used instead of Conductive Particle 2.

(Example 5)

A sample was produced in the same manner as in Example 2 except that Conductive Particle 5 was used instead of Conductive Particle 2.

(Comparative Example 1)

A sample was produced in the same manner as in Example 2 except that Conductive Particle 6 was used instead of Conductive Particle 2.

(Comparative Example 2)

A sample was produced in the same manner as in Example 2 except that Conductive Particle 7 was used instead of Conductive Particle 2.

(Measurement of film thickness of metal)

In the measurement of the film thicknesses of Pd, Ni, and Au, after dissolving each particle in 50 volume% of aqua regia, resin fine particles and solids were separated by filtration using a membrane filter (manufactured by Millipore) with a diameter of 3 m, and the atoms were removed. After measuring the quantity of each metal by the light absorption photometer S4700 (product name of the Hitachi Seisakusho make), it was converted into thickness.

(Component Analysis in Plating Film)

As component analysis in a plating film, after dissolving each particle in 50 volume% of aqua regia, resin was separated by filtration with a membrane filter (made by Millipore) of 3 micrometers in diameter, and ICP (inductively coupled plasma) light emission analyzer P4010 (Product name manufactured by Hitachi Seisakusho Co., Ltd.) was used.

(Coverage rate of subsidiary particles)

The coverage of the magnetic particles (insulating particles) was calculated by taking an electron microscope photograph of each conductive particle and analyzing the image. In an electron microscope, it observed at 5000 times or more using S4700 (product name of the Hitachi Seisakusho make).

(Particle test)

1 g of any one of the conductive particles 1 to 7 was collected and dispersed in 50 g of pure water. Next, the sample was put into a 60 ml pressure vessel, and it was left to stand at 100 degreeC for 10 hours.

Then, the dispersion solvent of electroconductive particle was filtered with the 0.2 micrometer filter, and each metal ion in the filtrate was measured with the atomic absorption photometer. The amount of soaked (ion measurement value) was calculated | required by the following formula.

(Component analysis)

Each mother particle before the insulation coating treatment was sprayed onto a conductive tape (Cat No7311, manufactured by Nissin EM Co., Ltd.) fixed to the sample stand, and the sample stand was turned upside down to shake off excess conductive particles. Next, using the EDX analyzer attached to the scanning electron microscope S4700 (product name manufactured by Hitachi Seisakusho Co., Ltd.): EMAX EX-300 (product name manufactured by Horiba Seisakusho Co., Ltd.), it was 30,000 times. The conductive layer on the enlarged mother particle surface was analyzed and quantified. In addition, the phosphorus concentration in palladium measured 10 parent particle | grains, and computed it from the average value. In addition, the flakes of the conductive layer portion of the conductive particles were cut out with a converging ion beam. Using a transmission electron microscope HF-2200 (product name manufactured by Hitachi Seisakusho Co., Ltd.), the flakes were observed at 100,000 times or more, and the component analysis of each region of the conductive layer was carried out using EDRAN, manufactured by NORAN Inc., attached to the apparatus. It was. The concentrations of nickel, palladium and phosphorus in each region were calculated from the obtained values.

(Insulation resistance test and conduction resistance test)

The insulation resistance test (insulation reliability test) and the conduction resistance test of the samples produced in Examples 1 to 5 and Comparative Examples 1 to 2 were performed. It is important for the anisotropic conductive adhesive film to have high insulation resistance between the chip electrodes and low conduction resistance (connection resistance) between the chip electrode and the glass electrode.

The insulation resistance between the chip electrodes measured 20 samples and measured their minimum value. About insulation resistance, the minimum value of the result before and behind a bias test (humidity test of 60% of humidity, 90 degreeC, and 20V DC voltage) is shown. In addition, 100 hours, 300 hours, 500 hours, and 1000 hours shown in Table 1 mean the time of a bias test.

In addition, the average value of 14 samples was measured about the conduction resistance between a chip electrode and a glass electrode. The conduction resistance measured the initial value and the value after a moisture absorption heat test (it left for 1000 hours in 85 degreeC of temperature, 85% of humidity conditions).

(result)

Table 1 shows the measurement results of Examples 1 to 5 and Comparative Examples 1 and 2 described above.

As shown in Table 1, in the conductive particles of Examples 1 to 5 that do not use nickel at all, almost no elution of the metal was observed, as shown in the test results of the frying test.

On the other hand, in Comparative Examples 1 and 2 in which nickel is used as the base, nickel tends to elute as compared with Examples 1 to 5. Therefore, in a narrow pitch COG substrate, it is better not to use nickel.

In addition, palladium, a precious metal, hardly elutes. The insulation reliability test results almost depended on the elution amount of nickel, and the Example with little elution of nickel shows a favorable result, and it is clear that the comparative example with many elution of nickel has low insulation reliability.

Although palladium is relatively inexpensive and practical among precious metals, it is rather expensive compared with nickel which is used a lot as conductive particles for anisotropic conductive films, and therefore, the amount of palladium used is to be reduced as much as possible. On the other hand, when contacting an electrode, the palladium layer on the surface of the electrically conductive particles needs to be dug into the electrode without being torn. In addition, the palladium layer is required to have sufficient strength such that cracking or peeling does not occur due to external force in the conductive particle manufacturing step. Palladium is ductile compared to nickel, but less hard.

In the present invention, by using phosphate-based electroless palladium plating solution such as hypophosphorous acid or phosphorous acid as the reducing agent, vacancy in the palladium layer can provide conductive particles having high hardness and excellent corrosion resistance.

The components in each of the plating films of Examples 1 to 5 were qualitatively analyzed by an ICP (inductively coupled plasma) emission spectrometer P4010 (product name manufactured by Hitachi Seisakusho Co., Ltd.). The element was not detected within the detection error range.

(Example 6)

Instead of using the conductive particles 1, the mother particles 2 were used, except that the amount of the mother particles 2 was adjusted to be half the number of the conductive particles dispersed per unit area of the anisotropic conductive adhesive film produced in Example 1, Samples were prepared in the same manner as in Example 1.

(Comparative Example 3)

Instead of using the conductive particles 1, the mother particles 7 were used, except that the amount of the mother particles 7 was adjusted to be half of the number of the conductive particles dispersed per unit area of the anisotropic conductive adhesive film produced in Example 1, Samples were prepared in the same manner as in Example 1.

In the same manner as in Examples 1 to 5, the soaking test and the conduction resistance test of the particles in Example 6 and Comparative Example 3 were performed.

The test results of Example 6 and Comparative Example 3 are shown in Table 2.

(Evaluation of Particles Not Insulated)

As shown in Table 2, although the connection resistance of Example 6 was favorable, the connection resistance of the comparative example 3 increased with time. This is because it is difficult to penetrate into the electrode because the gold layer of Comparative Example 3 is soft, and it cannot follow the deviation of the electrode position generated with the passage of time.

When the sample was observed with the optical microscope from the glass surface side, the aggregation of particle | grains was observed by the comparative example 3 much. EDX analysis of the parent particle 7 of the comparative example 3 showed that since the phosphorus concentration in nickel was low as 2 weight%, in the comparative example 3, it is thought that the aggregation of the mother particle 7 by magnetism generate | occur | produced.

As shown in Table 2, in Example 6 having only the palladium layer as the metal layer, only a small amount of palladium was eluted in the sagging test, but in Comparative Example 3, nickel was eluted in large quantities. The eluted nickel lowers the conduction resistance because it causes short defects due to migration or forms an oxide film on the surface of palladium. In this way, it is necessary to avoid using a metal (for example, nickel) in which elution may occur.

As a method of electroless palladium plating in which a palladium layer is formed on resin fine particles, in this embodiment, a catalyst is impregnated in a dry electroless palladium plating solution to immerse activated resin fine particles, and a catalyst is provided and activated resin. Although the fine particle was immersed in warm distilled water and the electroless palladium plating liquid was added gradually, disperse | distributing by stirring, the method of palladium plating is not limited to these methods. In addition, as a method of sequentially adding the above-mentioned electroless palladium plating solution, the electroless plating solution after completion of bathing may be dropped, or the components of the electroless palladium plating solution may be divided into at least two or more, and these may be added simultaneously and in parallel. . As a method of dividing the component of an electroless palladium plating liquid, there exists a method of adding a palladium ion, a palladium complex component, and a reducing agent component as a separate liquid, for example.

As described above, according to the present invention, it is possible to provide conductive particles having low cost, high conductivity, and excellent connection reliability between electrodes without causing migration.

1: insulating particles
2, 2a: mother particle
3: adhesive
4: first substrate
5: first electrode
6: second substrate
7: second electrode
8, 8a, 8b: conductive particles
11: core particle
12: palladium layer
40: anisotropic conductive adhesive
42: connection structure

Claims (5)

And a conductive layer formed on the surface of the resin fine particles and the resin fine particles,
The conductive layer is a palladium layer containing phosphorus,
Phosphorus concentration in the said palladium layer is 1 weight% or more and 10 weight% or less,
The thickness of the said palladium layer is 20 nm or more and 130 nm or less, The electrically-conductive particle characterized by the above-mentioned. The electrically-conductive particle of Claim 1 provided with the insulating particle arrange | positioned on the surface of the said palladium layer, and whose particle diameter is 20-500 nm. The conductive particle according to claim 1 or 2, wherein the palladium layer is a reduced plating palladium layer. The conductive particle according to claim 1 or 2, wherein the components in the conductive layer are qualitatively quantified by energy dispersive X-ray spectroscopy. The anisotropic conductive adhesive obtained by disperse | distributing the electrically-conductive particle of Claim 1 or 2 to an adhesive agent.

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