JP2013214511A - Conductive particle, conductive material, and connection structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive particle that is used to connect between electrodes so as to lower connection resistance between the electrodes, and furthermore improve conduction reliability between the electrodes, and conductive material using the conductive particle.SOLUTION: A conductive particle 1 according to the invention includes a base particle 2, and a conductive layer 3 placed on a surface of the base particle 2. The conductive layer includes a crystal structure, is in contact with the base particle 2, and includes nickel and phosphorus. Conductive material according to the invention includes the above-mentioned conductive particle 1 and binder resin.

Description

  The present invention relates to conductive particles in which a conductive layer is arranged on the surface of base particles, and more particularly to conductive particles that can be used for electrical connection between electrodes, for example. The present invention also relates to a conductive material and a connection structure using the conductive particles.

  Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known. In the anisotropic conductive material, conductive particles are dispersed in a binder resin.

  The anisotropic conductive material is used for connection between an IC chip and a flexible printed circuit board, connection between an IC chip and a circuit board having an ITO electrode, and the like. For example, after disposing an anisotropic conductive material between the electrode of the IC chip and the electrode of the circuit board, these electrodes can be electrically connected by heating and pressing.

  As an example of the conductive particles, the following Patent Document 1 discloses a conductive material in which a nickel conductive layer or a nickel alloy conductive layer is formed on the surface of spherical base particles having an average particle diameter of 1 to 20 μm by an electroless plating method. Sex particles are disclosed. The conductive particles have minute protrusions of 0.05 to 4 μm on the outermost layer of the conductive layer. The conductive layer and the protrusion are substantially continuously connected.

  Patent Document 2 below discloses Ni plated particles in which a Ni coating is formed on the surface of core material particles by an electroless Ni plating method. In this Ni plating particle, the content of P in the thickness direction in the Ni coating is smaller on the Ni coating surface side than on the core material particle side. Moreover, in this Ni plating particle, since the content of phosphorus in the Ni coating is relatively large, the Ni coating does not have a crystal structure.

JP 2000-243132 A JP 2003-034879 A

  When the electrodes are connected using the conductive particles described in Patent Documents 1 and 2, the connection resistance between the electrodes may increase. In the examples of Patent Documents 1 and 2, a conductive layer containing nickel and phosphorus is formed. An oxide film is often formed on the surface of the electrode connected by the conductive particles and the surface of the conductive layer of the conductive particles. When conductive particles having a conductive layer containing nickel and phosphorus are connected between the electrodes, the conductive layer containing nickel and phosphorus is relatively soft. There is a tendency that the connection resistance cannot be sufficiently eliminated and the connection resistance tends to be high.

  If the thickness of the conductive layer containing nickel and phosphorus is increased in order to reduce the connection resistance, the conductive particles are not sufficiently compressed and deformed, and the contact area between the conductive particles and the electrode tends to be reduced. When the contact area between the conductive particles and the electrode is small, the connection resistance tends to increase. Moreover, when the contact area of electroconductive particle and an electrode is small, the conduction | electrical_connection reliability between electrodes will become low.

  An object of the present invention is to provide conductive particles capable of reducing the connection resistance between the electrodes and further improving the conduction reliability between the electrodes when used for the connection between the electrodes, and the conductive particles. It is to provide a conductive material and a connection structure used.

  According to a wide aspect of the present invention, there are provided base particles and a conductive layer disposed on the surface of the base particles, the conductive layer including a crystal layer having a crystal structure, Conductive particles are provided that are in contact with the substrate particles and in which the crystal layer contains nickel and phosphorus.

  On the specific situation with the electroconductive particle which concerns on this invention, content of phosphorus in 100 weight% of the whole said crystal | crystallization layer is 4 weight% or less.

  On the other specific situation of the electroconductive particle which concerns on this invention, the said crystal | crystallization layer has a 1st area | region and a 2nd area | region with more phosphorus content than this 1st area | region.

  In another specific aspect of the conductive particle according to the present invention, the second region is located closer to the base particle in the thickness direction of the crystal layer than the first region.

  In another specific aspect of the conductive particle according to the present invention, the phosphorus content in the second region is 2.0% by weight or more higher than the phosphorus content in the first region.

  In still another specific aspect of the conductive particle according to the present invention, the thickness of the entire conductive layer is 0.05 μm or more and 0.3 μm or less.

  In another specific aspect of the conductive particle according to the present invention, the conductive layer has a protrusion on the outer surface.

  The conductive material according to the present invention includes the conductive particles described above and a binder resin.

  The connection structure according to the present invention includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, and the connection The part is formed of the above-described conductive particles, or is formed of a conductive material containing the conductive particles and a binder resin.

  In the conductive particles according to the present invention, a conductive layer is disposed on the surface of the base particle, and the conductive layer further includes a crystal layer having a crystal structure, and the crystal layer is in contact with the base particle. In addition, since the crystal layer contains nickel and phosphorus, the connection resistance between the electrodes can be lowered when the conductive particles according to the present invention are used for connection between the electrodes. Furthermore, the reliability of conduction between the electrodes can be enhanced.

FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention. FIG. 3 is a cross-sectional view showing conductive particles according to the third embodiment of the present invention. FIG. 4 is a front cross-sectional view schematically showing a connection structure using conductive particles according to the first embodiment of the present invention. FIG. 5 is a schematic cross-sectional view for explaining a state when the conductive particles are compressed. FIG. 6 is a schematic diagram illustrating an example of a relationship between a compressive load and a compressive displacement when a crack occurs in the conductive layer when the conductive particles are compressed.

  Details of the present invention will be described below.

  The electroconductive particle which concerns on this invention has a base material particle and the electroconductive layer arrange | positioned on the surface of this base material particle. In the conductive particles according to the present invention, the conductive layer has a crystal structure. The crystal layer is in contact with the base material particles. The crystal layer includes nickel and phosphorus. The crystal layer is directly laminated on the surface of the base particle. The conductive layer may include only the crystal layer, or may include the crystal layer and a conductive layer (such as a second conductive layer) other than the crystal layer.

  Since the electroconductive particle which concerns on this invention is equipped with the structure mentioned above, the connection resistance between the electrodes in the connection structure obtained can be made low, and the conduction | electrical_connection reliability between electrodes can be improved. Since the crystal layer has a crystal structure, it is relatively hard. In particular, when the crystal layer is in contact with the substrate particles, the conductivity in the conductive layer is increased, and the connection resistance between the electrodes is effectively reduced.

  Moreover, it is preferable that content of phosphorus in 100 weight% of the whole crystal layer is 4 weight% or less. When the phosphorus content is 4% by weight or less, it becomes easier to form a crystal layer having a crystal structure, and the conduction reliability between the electrodes is further enhanced.

  From the viewpoint of effectively reducing the connection resistance between the electrodes, the crystal layer preferably has a first region and a second region having a higher phosphorus content than the first region. The first region and the second region are located on the substrate particle side (inner side) and the opposite side (outer side) of the substrate particle in the thickness direction of the crystal layer, or the substrate particle It is preferable to be located on the opposite side (outer side) and the substrate particle side (inner side). The phosphorus content preferably has a gradient in the thickness direction of the crystal layer. It is preferable that phosphorus is unevenly distributed in the thickness direction of the crystal layer.

  The second region may be located closer to the base particle side (inner side) in the thickness direction of the crystal layer than the first region, and the second region is more than the first region, You may be located in the thickness direction of the said crystal | crystallization layer on the opposite side (outside) with a base particle. The first region and the second region may be positioned so as to be in contact with each other in the thickness direction, or may be positioned at a distance. From the viewpoint of further increasing the connection resistance between the electrodes, the second region is preferably located closer to the base particle side (inside) in the thickness direction of the crystal layer than the first region. The phosphorus content in the crystal layer is such that, in the thickness direction, the phosphorus content on the base particle side (inner side) is larger than the phosphorus content on the opposite side (outer side) from the base particle. It is preferable that the content of has a gradient. In the thickness direction, phosphorus is unevenly distributed in the crystal layer so that the content of phosphorus on the substrate particle side (inner side) is larger than the content of phosphorus on the side opposite to the substrate particle (outer side). preferable.

  The absolute value of the difference between the phosphorus content in the second region and the phosphorus content in the first region is preferably 2% by weight or more, more preferably 1% by weight or more, preferably 0.5%. % By weight or less, more preferably 0.1% by weight or less.

  The second region is preferably a region (crystal layer portion) having a thickness of 5 nm from the surface (inner surface) on the substrate particle side of the crystal layer toward the opposite side (outside) of the substrate particle. The first region is preferably a region (crystal layer portion) having a thickness of 5 nm from the surface (outer surface) opposite to the substrate particle of the crystal layer toward the substrate particle side (inner side).

  In the thickness direction in the crystal layer, the absolute value of the difference between the maximum phosphorus content and the minimum phosphorus content is preferably 2% by weight or more, more preferably 1% by weight or more, preferably 0 .5% by weight or less, more preferably 0.1% by weight or less.

  The crystal size in the crystal layer is preferably 40 nm or more, and preferably 100 nm or less. When the size of the crystal is not less than the above lower limit and not more than the above upper limit, the connection resistance between the electrodes can be effectively lowered, and the 5% K value and the compression displacement causing cracking described below have the specific above values. It is easy to be satisfied. The adjustment of the size of the crystal greatly contributes to the adjustment of the compression displacement in which a 5% K value and cracks described later occur, and particularly contributes to the adjustment of the compression displacement. From the standpoint of making the 5% K value, which will be described later, and the compression displacement at which cracking occurs more optimal, further reducing the connection resistance between the electrodes and further increasing the conduction reliability between the electrodes, the size of the crystal More preferably, it is 70 nm or more.

  The method for adjusting the size of the crystal is not particularly limited, and a conventionally known method can be applied.

  Another conductive layer (a conductive layer other than the crystal layer) may be disposed on the outer surface of the crystal layer. It is preferable that the outer surface of the conductive particles is the crystal layer. In the crystal layer, nickel and phosphorus may be alloyed.

  The crystal layer preferably contains nickel as a main component. The content of nickel in 100% by weight of the crystal layer is preferably 50% by weight or more, more preferably 60% by weight or more, still more preferably 70% by weight or more, and particularly preferably 90% by weight or more. The content of nickel in 100% by weight of the crystal layer may be 97% by weight or more, 97.5% by weight or more, or 98% by weight or more. The upper limit of the nickel content can be appropriately changed depending on the contents of phosphorus, tungsten, molybdenum and the like. The content of nickel in 100% by weight of the crystal layer is preferably 99.85% by weight or less, more preferably 99.7% by weight or less, and still more preferably less than 99.45% by weight. When the nickel content is not less than the lower limit, the connection resistance between the electrodes is further reduced. Moreover, when there are few oxide films in the surface of an electrode or a conductive layer, there exists a tendency for the connection resistance between electrodes to become low, so that there is much content of the said nickel.

  The crystal layer preferably contains at least one of tungsten and molybdenum in addition to nickel and phosphorus. That is, the crystal layer is preferably a nickel-tungsten / molybdenum-phosphorus crystal layer containing at least one of nickel, tungsten, and molybdenum and phosphorus. In 100% by weight of the nickel-tungsten / molybdenum-phosphorus crystal layer, the content of nickel is preferably 70% by weight or more. In the crystal layer, nickel and at least one of tungsten and molybdenum may be alloyed. In the crystal layer, at least one of tungsten and molybdenum and phosphorus may be alloyed. In addition, in the crystal layer containing at least one of nickel, tungsten, and molybdenum and phosphorus, chromium or seaborgium may be used in addition to tungsten and molybdenum.

  In the case of conductive particles having a crystal layer that does not contain both tungsten and molybdenum, the crystal layer that does not contain both tungsten and molybdenum tends to have a relatively low hardness at the initial stage of compression. For this reason, at the time of the connection between electrodes, the effect which eliminates the oxide film on the surface of an electrode and electroconductive particle becomes small, and there exists a tendency for the effect which makes connection resistance low.

  On the other hand, when the thickness of the crystal layer not containing both tungsten and molybdenum is increased in order to further obtain the effect of reducing the connection resistance or to be suitable for an application in which a large current flows, the conductive particles and the electrode The contact area tends to be small. As a result, the conduction reliability between the electrodes in the connection structure tends to be low.

  On the other hand, when the conductive particles have a nickel-tungsten / molybdenum-phosphorus crystal layer, it is easy to set a 5% K value described later to be equal to or higher than the above lower limit. Furthermore, when the conductive particles are compressed by 70% or more of the particle diameter of the conductive particles before compression in the compression direction, the nickel-tungsten / molybdenum-phosphorus crystal layer is appropriately cracked. Easy. By slowing the occurrence of cracks, the contact area between the conductive particles and the electrodes is further increased, and therefore the connection resistance between the electrodes is further reduced.

  Further, when the crystal layer is a nickel-tungsten / molybdenum-phosphorus crystal layer, the nickel-tungsten / molybdenum-phosphorus crystal layer has an appropriate hardness, so that the conductive particles are compressed between the electrodes. When connected, an appropriate indentation can be formed on the electrode. The indentation formed on the electrode is a concave portion of the electrode formed by pressing the electrode with conductive particles.

  The total content of tungsten and molybdenum in 100% by weight of the crystal layer is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, still more preferably 0.2% by weight or more, and still more preferably. Is 0.5% by weight or more, still more preferably 1% by weight or more, particularly preferably more than 5% by weight, most preferably 10% by weight or more. When the total content of tungsten and molybdenum is not less than the above lower limit, the hardness of the outer surface of the conductive layer is further increased. For this reason, when the oxide film is formed on the surface of the electrode or the conductive layer, the oxide film on the surface of the electrode and the conductive particles can be effectively eliminated, the connection resistance can be lowered, and the obtained connection The impact resistance of the structure can be increased. Furthermore, when the total content of tungsten and molybdenum is equal to or greater than the above lower limit, the magnetism of the outer surface of the conductive layer becomes weak, and a plurality of conductive particles are difficult to aggregate. For this reason, the short circuit between electrodes can be suppressed effectively.

  The upper limit of the total content of tungsten and molybdenum in 100% by weight of the crystal layer can be appropriately changed depending on the contents of nickel, phosphorus, and the like. The total content of tungsten and molybdenum in 100% by weight of the crystal layer is preferably 40% by weight or less, more preferably 30% by weight or less, still more preferably 25% by weight or less, and particularly preferably 20% by weight or less. .

  In order to obtain the effect of lowering the connection resistance further, or to be suitable for applications where a large current flows, the thickness of the conductive layer not containing phosphorus is increased, or the thickness of the crystal layer containing nickel and phosphorus is increased. In such a case, the contact area between the conductive particles and the electrode tends to be small. As a result, the conduction reliability between the electrodes in the connection structure tends to be low.

  On the other hand, when the conductive particles have the specific crystal layer, it is easy to set a 5% K value described later to be equal to or higher than the lower limit. Furthermore, when the conductive particles are compressed by 70% or more of the particle diameter of the conductive particles before compression in the compression direction, it is easy to appropriately cause cracks in the crystal layer. In addition, when the conductive particles have a nickel-tungsten / molybdenum-phosphorus crystal layer, it is even easier to set the 5% K value described later to the above lower limit or more. Furthermore, when the conductive particles are compressed by 70% or more of the particle diameter of the conductive particles before compression in the compression direction, the nickel-tungsten / molybdenum-phosphorus conductive layer is more appropriately cracked. Is easy. By slowing the occurrence of cracks, the contact area between the conductive particles and the electrodes is further increased, and therefore the connection resistance between the electrodes is further reduced.

  Furthermore, since the crystal layer has an appropriate hardness, an appropriate indentation can be formed on the electrodes when the conductive particles are compressed to connect the electrodes. The indentation formed on the electrode is a concave portion of the electrode formed by pressing the electrode with conductive particles.

  The phosphorus content in 100% by weight of the crystal layer is preferably 0.1% by weight or more, more preferably 0.5% by weight or more, still more preferably 1% by weight or more, preferably 5% by weight or less, more preferably It is 4% by weight or less, more preferably 3% by weight or less, and particularly preferably 2.5% by weight or less. When the phosphorus content is not less than the above lower limit, the conductive layer becomes harder, the oxide film on the surface of the electrode and conductive particles can be more effectively removed, and the connection resistance between the electrodes is further reduced. Can do. If the phosphorus content is less than or equal to the above upper limit, the content of nickel, tungsten, molybdenum and the like is relatively increased, so that the connection resistance between the electrodes is reduced. In addition, it becomes easy to obtain a favorable crystal structure, so that there is little content of the said phosphorus.

  Further, since the crystal layer contains at least one of tungsten and molybdenum, the crystal layer is considerably hardened. As a result, even when an impact is applied to the connection structure connecting the electrodes by the conductive particles, the conductive layer is conductive. Defects are less likely to occur. That is, the impact resistance of the connection structure can be increased.

  The method for measuring the contents of nickel, tungsten, molybdenum and phosphorus in the crystal layer is not particularly limited, and various known analysis methods can be used. Examples of this measuring method include absorption spectrometry or spectrum analysis. In the above-mentioned absorption analysis method, a flame absorptiometer, an electric heating furnace absorptiometer or the like can be used. Examples of the spectrum analysis method include a plasma emission analysis method and a plasma ion source mass spectrometry method.

  When measuring the contents of nickel, tungsten, molybdenum and phosphorus in the crystal layer, it is preferable to use an ICP emission analyzer. Examples of commercially available ICP emission analyzers include ICP emission analyzers manufactured by HORIBA.

  When measuring each content of nickel, tungsten, molybdenum and phosphorus in the thickness direction of the conductive layer, it is preferable to use an FE-TEM apparatus. Examples of commercially available FE-TEM devices include JEM-2010 manufactured by JEOL Ltd.

  A method for forming a conductive layer (the other conductive layer and the crystal layer) on the surface of the base particle is not particularly limited. As a method for forming the conductive layer, for example, a method by electroless plating, a method by electroplating, a method by physical vapor deposition, and a paste containing metal powder or metal powder and a binder is used for base particles or other conductive layers. For example, a method of coating the surface. Especially, since formation of a conductive layer is simple, the method by electroless plating is preferable. Examples of the method by physical vapor deposition include methods such as vacuum vapor deposition, ion plating, and ion sputtering.

  The method for forming the crystal layer having the above crystal structure includes a method for controlling the pH of the plating solution used for forming the conductive layer, a method for controlling the temperature of the plating solution used for forming the conductive layer, and the phosphorus concentration in the plating solution. And a post-plating heat treatment method and the like. Especially, since it is excellent in reaction control, the method of controlling the pH of plating reaction is suitable. Specifically, for example, the base material particles provided with the catalyst, and at least one complexing agent selected from the group consisting of citric acid, malic acid, succinic acid, propionic acid, lactic acid, and acetic acid. A crystal layer can be formed on the surface of the substrate particles by using the nickel plating solution contained, adjusting the pH during nickel plating reaction to 6 to 9, and adjusting the temperature to 50 to 80 ° C. The pH during the nickel plating reaction is preferably 7 to 9, and the temperature is preferably 55 to 65 ° C.

  Examples of a method for controlling the content of nickel, tungsten, molybdenum and phosphorus in the crystal layer include, for example, a method for controlling the pH of a nickel plating solution when forming the crystal layer by electroless nickel plating, and electroless nickel. When forming the crystal layer by plating, a method for adjusting the concentration of the phosphorus-containing reducing agent, a method for adjusting the tungsten concentration in the nickel plating solution, a method for adjusting the molybdenum concentration in the nickel plating solution, and in the nickel plating solution And a method of adjusting the nickel salt concentration.

  In the method of forming by electroless plating, generally, a catalyzing step and an electroless plating step are performed. Hereinafter, an example of a method for forming an alloy plating layer containing at least one of nickel, tungsten, and molybdenum and phosphorus on the surface of the resin particles by electroless plating will be described.

  In the catalyzing step, a catalyst serving as a starting point for forming a plating layer by electroless plating is formed on the surface of the resin particles.

  As a method of forming the catalyst on the surface of the resin particles, for example, after adding the resin particles to a solution containing palladium chloride and tin chloride, the surface of the resin particles is activated with an acid solution or an alkali solution, A method of depositing palladium on the surface of the resin particles, and after adding the resin particles to a solution containing palladium sulfate and aminopyridine, the surface of the resin particles is activated by a solution containing a reducing agent. Examples thereof include a method of depositing palladium on the surface. As the reducing agent, a phosphorus-containing reducing agent such as sodium hypophosphite is used.

  In the electroless plating step, a nickel plating bath containing a nickel salt, at least one of a tungsten-containing compound and a molybdenum-containing compound, and the phosphorus-containing reducing agent is used. By immersing the resin particles in the nickel plating bath, nickel can be deposited on the surface of the resin particles on which the catalyst is formed, and includes at least one of nickel, tungsten and molybdenum, and phosphorus. A conductive layer can be formed.

  Examples of the tungsten-containing compound include tungsten boride and sodium tungstate.

  Examples of the molybdenum-containing compound include molybdenum boride and sodium molybdate.

  Examples of the phosphorus-containing reducing agent include sodium hypophosphite, potassium hypophosphite, and ammonium hypophosphite.

  The thickness of the crystal layer is preferably 0.005 μm or more, more preferably 0.01 μm or more, still more preferably 0.05 μm or more, preferably 1 μm or less, more preferably 0.3 μm or less. When the thickness of the crystal layer is not less than the above lower limit and not more than the above upper limit, sufficient conductivity is obtained, and the conductive particles do not become too hard, and the conductive particles are sufficiently deformed when connecting the electrodes. To do.

  When the conductive layer has a laminated structure of two or more layers, the thickness of the crystal layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.05 μm or more, preferably 0.5 μm or less. More preferably, it is 0.3 μm or less, and further preferably 0.1 μm or less. When the thickness of the crystal layer is not less than the above lower limit and not more than the above upper limit, the coating with the crystal layer can be made uniform, and the connection resistance between the electrodes becomes sufficiently low.

  The thickness of the crystal layer is particularly preferably 0.05 μm or more and 0.3 μm or less. Furthermore, it is particularly preferable that the particle diameter of the base particles is 2 μm or more and 5 μm or less, and the thickness of the crystal layer is 0.05 μm or more and 0.3 μm or less. The total thickness of the conductive layer is particularly preferably 0.05 μm or more and 0.3 μm or less. Furthermore, it is particularly preferable that the particle diameter of the substrate particles is 2 μm or more and 5 μm or less, and the thickness of the entire conductive layer is 0.05 μm or more and 0.3 μm or less. In these cases, the conductive particles can be suitably used for applications in which a large current flows. Furthermore, when the conductive particles are compressed to connect the electrodes, it is possible to further suppress the electrodes from being damaged.

  When the conductive layer has a laminated structure of two or more layers, the total thickness of the conductive layer is preferably 0.001 μm or more, more preferably 0.01 μm or more, still more preferably 0.05 μm or more, and particularly preferably 0.1 μm. The thickness is preferably 1 μm or less, more preferably 0.5 μm or less, still more preferably 0.3 μm or less, and still more preferably 0.1 μm or less. When the thickness of the entire conductive layer is not less than the above lower limit and not more than the above upper limit, the covering of the entire conductive layer can be made uniform, and the connection resistance between the electrodes becomes sufficiently low.

  The thickness of the crystal layer and the thickness of the entire conductive layer can be measured, for example, by observing the cross section of the conductive particles using a transmission electron microscope (TEM).

  The metal for forming the other conductive layer (second conductive layer or the like) is not particularly limited. Examples of the metal include gold, silver, copper, palladium, platinum, zinc, iron, tin, lead, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, and tungsten. , Molybdenum, and alloys thereof. Examples of the metal include tin-doped indium oxide (ITO) and solder. Especially, since the connection resistance between electrodes becomes still lower, an alloy containing tin, nickel, palladium, copper or gold is preferable, and nickel or palladium is more preferable. The metal constituting the conductive layer preferably contains nickel.

  The conductive particles according to the present invention preferably have protrusions on the conductive surface. The conductive layer preferably has a protrusion on the outer surface. An oxide film is often formed on the surface of the electrode connected by the conductive particles. Furthermore, an oxide film is often formed on the surface of the conductive layer of the conductive particles. By using the conductive particles having protrusions, the oxide film is effectively eliminated by the protrusions by placing the conductive particles between the electrodes and then pressing them. For this reason, an electrode and electroconductive particle can be contacted still more reliably and the connection resistance between electrodes can be made low. Further, when the conductive particles have an insulating material on the surface, or when the conductive particles are dispersed in a binder resin and used as an anisotropic conductive material, the conductive particles and the electrodes are formed by protrusions of the conductive particles. The resin between can be effectively eliminated. For this reason, the conduction | electrical_connection reliability between electrodes can be improved.

  It is preferable that there are a plurality of protrusions. The number of protrusions on the outer surface of the conductive layer per one conductive particle is preferably 3 or more, more preferably 5 or more. The upper limit of the number of protrusions is not particularly limited. The upper limit of the number of protrusions can be appropriately selected in consideration of the particle diameter of the conductive particles.

In the conductive particles according to the present invention, the compression modulus (5% K value) when compressed by 5% is preferably 7000 N / mm ² or more. Furthermore, when the conductive particles according to the present invention are compressed, the conductive layer is preferably cracked when the conductive particles are compressed by 70% or more of the particle diameter of the conductive particles before compression in the compression direction. For example, when the conductive particles are appropriately compressed, it is preferable that the conductive layer is moderately partially broken.

In the conductive particles according to the present invention, when the compression elastic modulus (5% K value) when compressed by 5% is 7000 N / mm ² or more, the conductive particles in the initial stage of compression have sufficient hardness. Have For this reason, the oxide film on the surface of the electrode and the conductive particles can be effectively eliminated at the initial stage of compression of the conductive particles at the time of connection between the electrodes. As a result, the electrode and the conductive layer in the conductive particles are effectively in contact, and the connection resistance between the electrodes can be further reduced.

  From the viewpoint of further reducing the connection resistance between the electrodes, the compression displacement at which the conductive layer is cracked is more preferably 75% or more. From the viewpoint of ensuring a sufficient space between the electrodes, the compressive displacement that causes cracking in the conductive layer is preferably 95% or less, more preferably 90% or less, still more preferably 85% or less, particularly preferably 80% or less. It is.

  The compression elastic modulus (5% K value) can be measured as follows.

  Using a micro-compression tester, the conductive particles are compressed under the conditions of a compression speed of 2.6 mN / sec and a maximum test load of 10 gf on the end face of a cylindrical indenter (diameter 50 μm, made of diamond). The load value (N) and compression displacement (mm) at this time are measured. From the measured value obtained, the compression elastic modulus can be obtained by the following formula. As the micro compression tester, for example, “Fischer Scope H-100” manufactured by Fischer is used.

K value (N / mm ² ) = (3/2 ^1/2 ) · F · S ⁻³ / ² · R ^−1/2
F: Load value when the conductive particles are compressively deformed by 5% (N)
S: Compression displacement (mm) when conductive particles are 5% compressively deformed
R: radius of conductive particles (mm)

  The compression elastic modulus universally and quantitatively represents the hardness of the conductive particles. By using the compression elastic modulus, the hardness of the conductive particles can be expressed quantitatively and uniquely.

  The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1 μm or more, preferably 100 μm or less, more preferably 20 μm or less. When the particle diameter of the conductive particles is not less than the above lower limit and not more than the upper limit, when the electrodes are connected using the conductive particles, the contact area between the conductive particles and the electrode is sufficiently large, and the conductive layer is formed. Aggregated conductive particles are less likely to be formed during formation. Further, the distance between the electrodes connected via the conductive particles does not become too large, and the conductive layer is difficult to peel from the surface of the base material particles.

  The particle diameter of the conductive particles indicates the diameter when the conductive particles are true spherical, and indicates the maximum diameter when the conductive particles are not true spherical.

  Hereinafter, the present invention will be clarified by describing specific embodiments and examples of the present invention with reference to the drawings.

  FIG. 1 is a cross-sectional view showing conductive particles according to the first embodiment of the present invention.

  As shown in FIG. 1, the conductive particle 1 includes a base particle 2, a conductive layer 3, a plurality of core substances 4, and a plurality of insulating substances 5. The conductive layer 3 is a crystal layer having a crystal structure. The conductive layer 3 (crystal layer) is in contact with the substrate particles 2 and the conductive layer 3 (crystal layer) includes a crystal layer containing nickel and phosphorus.

  The conductive layer 3 is disposed on the surface of the base particle 2. The conductive particle 1 is a coated particle in which the surface of the base particle 2 is coated with the conductive layer 3.

  The conductive particle 1 has a plurality of protrusions 1a on a conductive surface. The conductive layer 3 has a plurality of protrusions 3a on the outer surface. A plurality of core substances 4 are arranged on the surface of the base particle 2. A plurality of core materials 4 are embedded in the conductive layer 3. The core substance 4 is disposed inside the protrusions 1a and 3a. The conductive layer 3 covers a plurality of core materials 4. The outer surface of the conductive layer 3 is raised by the plurality of core materials 4 to form protrusions 1a and 3a.

  The conductive particles 1 have an insulating material 5 disposed on the outer surface of the conductive layer 3. At least a part of the outer surface of the conductive layer 3 is covered with the insulating material 5. The insulating substance 5 is made of an insulating material and is an insulating particle. Thus, the electroconductive particle which concerns on this invention may have the insulating substance arrange | positioned on the outer surface of an electroconductive layer. However, the conductive particles according to the present invention do not necessarily have an insulating material.

  FIG. 2 is a cross-sectional view showing conductive particles according to the second embodiment of the present invention.

  The conductive particles 11 shown in FIG. 2 include substrate particles 2, a first conductive layer 12, a second conductive layer 13 (another conductive layer), a plurality of core materials 4, and a plurality of insulating materials 5. And have. The first conductive layer 12 is a crystal layer having a crystal structure. The first conductive layer 12 (crystal layer) is in contact with the base particle 2 and the first conductive layer 12 (crystal layer) includes a crystal layer containing nickel and phosphorus.

  Only the conductive layer is different between the conductive particles 1 and the conductive particles 11. That is, the conductive particle 1 has a single-layered conductive layer, whereas the conductive particle 11 has a two-layered first conductive layer 12 and second conductive layer 13 formed. Yes.

  The second conductive layer 13 is disposed on the surface of the base particle 2. The first conductive layer 12 is disposed between the substrate particle 2 and the second conductive layer 13 (other conductive layer). Therefore, the first conductive layer 12 is disposed on the surface of the base particle 2, and the second conductive layer 13 is disposed on the surface of the first conductive layer 12. The second conductive layer 13 has a plurality of protrusions 13a on the outer surface. The conductive particles 11 have a plurality of protrusions 11a on the surface.

  FIG. 3 is a cross-sectional view showing conductive particles according to the third embodiment of the present invention.

  The conductive particles 21 shown in FIG. 3 have base material particles 2 and a conductive layer 22. The conductive layer 22 is disposed on the surface of the base particle 2. The conductive layer 22 is a crystal layer having a crystal structure. The conductive layer 22 (crystal layer) is in contact with the base particle 2 and the conductive layer 22 (crystal layer) includes a crystal layer containing nickel and phosphorus.

  The conductive particles 21 do not have a core substance. The conductive particles 21 do not have protrusions on the conductive surface. The conductive particles 21 are spherical. The conductive layer 22 has no protrusion on the surface. Thus, the electroconductive particle which concerns on this invention does not need to have a processus | protrusion, and may be spherical. Further, the conductive particles 21 do not have an insulating material. However, the conductive particles 21 may have an insulating material disposed on the surface of the conductive layer 22.

The 5% K value of the conductive particles 1, 11 and 21 is preferably 7000 N / mm ² or more. Further, when the conductive particles 1, 11, 21 are compressed, the conductive particles 1, 11, 21 are compressed and displaced by 70% or more of the particle diameter of the conductive particles 1, 11, 21 before compression in the compression direction. It is preferable that the conductive layers 3, 12, and 22 are cracked. That is, in the conductive particles 1, 11, and 21, when the particle diameter of the conductive particles 1, 11, 21 before compression in the compression direction is X, the particle diameter of the conductive particles 1, 11, 21 in the compression direction Is preferably 0.30X or less, the conductive layers 3, 12, and 22 are preferably cracked. For example, when the particle diameter of the conductive particles 1, 11, 21 before compression in the compression direction is 5 μm, the conductive particles 1, 11, 21 are compressed and the conductive particles 1, 11, 11 in the compression direction are compressed. When the particle size of 21 is 1.5 μm or less, it is preferable that cracks occur in the conductive layers 3, 12, and 22. In addition, the partial crack of the whole conductive layers 3, 12, and 22 may arise. In the conductive particles 11, only the first conductive layer 12 may be cracked, or only the second conductive layer 13 may be cracked.

  The “crack” indicates the first (first) crack in the conductive layer. Therefore, in the electroconductive particle 1,11,21 which concerns on this embodiment, when the electroconductive particle 1,11,21 which has the electroconductive layer 3,12,22 without a crack is compressed, electroconductive particle 1,11,21 When 21 is compressed and displaced by 70% or more of the particle diameter of the conductive particles 1, 11, 21 before compression in the compression direction, the conductive layers 3, 12, 22 are preferably cracked.

Specifically, the measurement of the compressive displacement at which the conductive layers 3, 12, and 22 are cracked is performed as follows. In FIG. 5, the conductive particles 21 are used.

  As shown in FIG. 5, the conductive particles 21 are placed on the base 71. Using a micro compression tester (“Fischerscope H-100” manufactured by Fischer), a cylinder (diameter 50 μm, made of diamond) is used as the compression member 72 under conditions of a compression speed of 0.33 mN / sec and a maximum test load of 10 mN. The smooth end surface 72a of the compression member 72 is lowered toward the conductive particles 21 in the direction indicated by the arrow A. The conductive particles 21 are compressed by the smooth end surface 72a. The compression is continued until the crack 22a is partially generated in the conductive layer 22 of the conductive particles 21. In the case of conductive particles 1 and 11, the same measurement is performed.

  In the cross-sectional view shown in FIG. 5, the state in which the crack 22 a is formed in the conductive layer 22 at the upper and lower portions of the conductive particles 21 is illustrated, but the position at which the crack is generated in the conductive layer is not particularly limited.

  When the conductive particles are compressed as described above, the conductive layer may crack when the conductive particles are compressed and displaced by 70% or more of the particle diameter of the conductive particles before compression in the compression direction. preferable.

  When the compressive load value and the compressive displacement are measured while compressing the conductive particles, the relationship between the compressive load value and the compressive displacement is, for example, as shown in FIG. In FIG. 6, the compression is started from the point A0, and the conductive layer is cracked at the point A1. As the conductive layer cracks, the compression displacement (particle diameter) of the conductive particles in the compression direction changes, and the compression displacement moves from the A1 point to the A2 point. When compressing, a compressive load is applied to the conductive particles, and if the conductive layer cracks, the conductive particles are compressed with a relatively small compressive load. Therefore, the compression member that applies the compressive load to the conductive particles moves. The compression displacement (particle diameter) of the conductive particles in the compression direction changes.

In FIG. 6, the slope of the line from point A0 to point A1 is relatively large. This is because the 5% K value of the conductive particles 21 is 7000 N / mm ² or more, and the conductive particles 21 are relatively hard.

  Hereinafter, the substrate particles, the core substance, the insulating substance, and the like will be described in more detail.

[Base material particles]
Examples of the substrate particles include resin particles, inorganic particles excluding metals, organic-inorganic hybrid particles, and metal particles. The base particles may be core-shell particles.

  The substrate particles are preferably resin particles formed of a resin. When connecting between electrodes using the said electroconductive particle, after arrange | positioning the said electroconductive particle between electrodes, the said electroconductive particle is compressed by crimping | bonding. When the substrate particles are resin particles, the conductive particles are easily deformed during the pressure bonding, and the contact area between the conductive particles and the electrode is increased. For this reason, the conduction | electrical_connection reliability between electrodes becomes high.

  Various organic materials are suitably used as the resin for forming the resin particles. Examples of the resin for forming 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; Alkylene terephthalate, polycarbonate, polyamide, phenol formaldehyde 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 Ketones, polyether sulfones, and polymers such as obtained by a variety of polymerizable monomer having an ethylenically unsaturated group is polymerized with one or more thereof. Since the hardness of the substrate particles can be easily controlled within a suitable range, the resin for forming the resin particles is obtained by polymerizing one or more polymerizable monomers having a plurality of ethylenically unsaturated groups. A polymer is preferred.

  When the resin particles are obtained by polymerizing a monomer having an ethylenically unsaturated group, the monomer having the ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer. And a polymer.

  Examples of the non-crosslinkable monomer include styrene monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth) acrylic acid, maleic acid, and maleic anhydride; (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 ( Alkyl (meth) acrylates such as meth) acrylate and isobornyl (meth) acrylate; oxygen such as 2-hydroxyethyl (meth) acrylate, glycerol (meth) acrylate, polyoxyethylene (meth) acrylate and glycidyl (meth) acrylate (Meth) acrylates; nitrile-containing monomers such as (meth) acrylonitrile; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether; vinyl acids such as vinyl acetate, vinyl butyrate, vinyl laurate, vinyl stearate Esters; 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 Is mentioned.

  Examples of the crosslinkable monomer include tetramethylolmethane tetra (meth) acrylate, tetramethylolmethane tri (meth) acrylate, tetramethylolmethane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, and dipenta Erythritol 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) Polyfunctional (meth) acrylates such as acrylate, (poly) tetramethylene di (meth) acrylate, 1,4-butanediol di (meth) acrylate; triallyl (iso) cyanurate, tria Rutorimeriteto, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, .gamma. (meth) acryloxy propyl trimethoxy silane, trimethoxy silyl styrene, include silane-containing monomers such as vinyltrimethoxysilane.

  The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method. Examples of this method include a method of suspension polymerization in the presence of a radical polymerization initiator, and a method of polymerizing by swelling a monomer together with a radical polymerization initiator using non-crosslinked seed particles.

  In the case where the substrate particles are inorganic particles or organic-inorganic hybrid particles excluding metal, examples of the inorganic material for forming the substrate particles include silica and carbon black. Although it does not specifically limit as the particle | grains formed with the said silica, For example, after hydrolyzing the silicon compound which has two or more hydrolysable alkoxysil groups, and forming a crosslinked polymer particle, it calcinates as needed. The particle | grains obtained by performing are mentioned. Examples of the organic / inorganic hybrid particles include organic / inorganic hybrid particles formed of a crosslinked alkoxysilyl polymer and an acrylic resin.

  When the substrate particles are metal particles, examples of the metal for forming the metal particles include silver, copper, nickel, silicon, gold, and titanium. However, the substrate particles are preferably not metal particles.

  The particle diameter of the substrate particles is preferably 0.1 μm or more, more preferably 1 μm or more, still more preferably 1.5 μm or more, particularly preferably 2 μm or more, preferably 1000 μm or less, more preferably 500 μm or less, and even more preferably. Is not more than 300 μm, more preferably not more than 50 μm, particularly preferably not more than 30 μm, and most preferably not more than 5 μm. When the particle diameter of the substrate particles is equal to or greater than the above lower limit, the contact area between the conductive particles and the electrodes is increased, so that the conduction reliability between the electrodes is further increased, and the electrodes are connected via the conductive particles. The connection resistance between them becomes even lower. Further, when forming the conductive layer on the surface of the base particle by electroless plating, it becomes difficult to aggregate and it becomes difficult to form the aggregated conductive particles. When the particle diameter is not more than the above upper limit, the conductive particles are easily compressed, the connection resistance between the electrodes is further reduced, and the distance between the electrodes is further reduced. The particle diameter of the base particle indicates a diameter when the base particle is a true sphere, and indicates a maximum diameter when the base particle is not a true sphere.

  The particle diameter of the substrate particles is particularly preferably 2 μm or more and 5 μm or less. When the particle diameter of the substrate particles is in the range of 2 to 5 μm, even when the distance between the electrodes is small and the thickness of the conductive layer is increased, small conductive particles can be obtained.

[Core material]
Since the core substance is embedded in the conductive layer, it is easy for the conductive layer to have a plurality of protrusions on the outer surface. However, in order to form protrusions on the surfaces of the conductive particles and the conductive layer, the core substance is not necessarily used.

  As the method for forming the protrusions, a core material is attached to the surface of the base particle, and then a conductive layer is formed by electroless plating, and a conductive layer is formed on the surface of the base particle by electroless plating. Thereafter, a method of attaching a core substance and further forming a conductive layer by electroless plating may be used.

  As a method for disposing the core substance on the surface of the base particle, for example, a conductive substance that becomes the core substance is added to the dispersion of the base particle, and the core substance is added to the surface of the base particle, for example, , A method of accumulating and adhering by van der Waals force, and adding a conductive substance as a core substance to the container containing the base particle, and applying mechanical action such as rotation of the container to the surface of the base particle. Examples include a method of attaching a core substance. Especially, since the quantity of the core substance to adhere is easy to control, the method of making a core substance accumulate and adhere on the surface of the base particle in a dispersion liquid is preferable. As another method for forming the protrusion, a first conductive layer is formed on the surface of the base particle, and then a core substance is disposed on the first conductive layer, and then the second conductive layer. And a method of adding a core substance in the middle of forming the conductive layer on the surface of the base particle.

  Examples of the material constituting the core material include conductive materials and non-conductive materials. Examples of the conductive material include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the nonconductive material include silica, alumina, and zirconia. Among them, metal is preferable because conductivity can be increased and connection resistance can be effectively reduced. The core substance is preferably metal particles.

  Examples of the metal include gold, silver, copper, platinum, zinc, iron, lead, tin, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, germanium and cadmium, and tin-lead. Examples include alloys composed of two or more metals such as alloys, tin-copper alloys, tin-silver alloys, tin-lead-silver alloys, and tungsten carbide. Of these, nickel, copper, silver or gold is preferable. The metal constituting the core material may be the same as or different from the metal constituting the conductive layer. The metal constituting the core material preferably includes a metal constituting the conductive layer. It is preferable that the metal which comprises the said core substance contains nickel. It is preferable that the metal which comprises the said core substance contains nickel.

  The shape of the core material is not particularly limited. The shape of the core substance is preferably a lump. Examples of the core substance include a particulate lump, an agglomerate in which a plurality of fine particles are aggregated, and an irregular lump.

  The average diameter (average particle diameter) of the core substance is preferably 0.001 μm or more, more preferably 0.05 μm or more, preferably 0.9 μm or less, more preferably 0.2 μm or less. When the average diameter of the core substance is not less than the above lower limit and not more than the upper limit, the connection resistance between the electrodes can be effectively reduced.

  The “average diameter (average particle diameter)” of the core substance indicates a number average diameter (number average particle diameter). The average diameter of the core material is obtained by observing 50 arbitrary core materials with an electron microscope or an optical microscope and calculating an average value.

[Insulating material]
The conductive particles according to the present invention preferably include an insulating material disposed on the surface of the conductive layer. In this case, when the conductive particles are used for connection between the electrodes, a short circuit between adjacent electrodes can be prevented. Specifically, when a plurality of conductive particles are in contact with each other, an insulating material is present between the plurality of electrodes, so that it is possible to prevent a short circuit between electrodes adjacent in the lateral direction instead of between the upper and lower electrodes. Note that when the conductive particles are pressurized with the two electrodes at the time of connection between the electrodes, the insulating substance between the conductive layer of the conductive particles and the electrodes can be easily excluded. In the case where the conductive particles have a plurality of protrusions on the outer surface of the conductive layer, the insulating material between the conductive layer and the electrode of the conductive particles can be more easily removed.

  It is preferable that the insulating material is an insulating particle because the insulating material can be more easily removed when the electrodes are pressed.

  Specific examples of the insulating resin that is the material of the insulating material include polyolefins, (meth) acrylate polymers, (meth) acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, and thermosetting. Resin, water-soluble resin, and the like.

  Examples of the polyolefins include polyethylene, ethylene-vinyl acetate copolymer, and ethylene-acrylic acid ester copolymer. Examples of the (meth) acrylate polymer include polymethyl (meth) acrylate, polyethyl (meth) acrylate, and polybutyl (meth) acrylate. Examples of the block polymer include polystyrene, styrene-acrylic acid ester copolymer, SB type styrene-butadiene block copolymer, SBS type styrene-butadiene block copolymer, and hydrogenated products thereof. Examples of the thermoplastic resin include vinyl polymers and vinyl copolymers. As said thermosetting resin, an epoxy resin, a phenol resin, a melamine resin, etc. are mentioned. Examples of the water-soluble resin include polyvinyl alcohol, polyacrylic acid, polyacrylamide, polyvinyl pyrrolidone, polyethylene oxide, and methyl cellulose. Of these, water-soluble resins are preferable, and polyvinyl alcohol is more preferable.

  Examples of a method for disposing an insulating material on the surface of the conductive layer include a chemical method and a physical or mechanical method. Examples of the chemical method include an interfacial polymerization method, a suspension polymerization method in the presence of particles, and an emulsion polymerization method. Examples of the physical or mechanical method include spray drying, hybridization, electrostatic adhesion, spraying, dipping, and vacuum deposition. In particular, since the insulating substance is difficult to be detached, a method of disposing the insulating substance on the surface of the conductive layer through a chemical bond is preferable.

  The average diameter (average particle diameter) of the insulating material can be appropriately selected depending on the particle diameter of the conductive particles, the use of the conductive particles, and the like. The average diameter (average particle diameter) of the insulating material is preferably 0.005 μm or more, more preferably 0.01 μm or more, preferably 1 μm or less, more preferably 0.5 μm or less. When the average diameter of the insulating material is not less than the above lower limit, the conductive layers of the plurality of conductive particles are difficult to contact when the conductive particles are dispersed in the binder resin. When the average diameter of the insulating particles is not more than the above upper limit, it is not necessary to make the pressure too high in order to eliminate the insulating material between the electrodes and the conductive particles when the electrodes are connected. There is no need for heating.

  The “average diameter (average particle diameter)” of the insulating material indicates a number average diameter (number average particle diameter). The average diameter of the insulating material is obtained using a particle size distribution measuring device or the like.

(Conductive material)
The conductive material according to the present invention includes the conductive particles described above and a binder resin. The conductive particles are preferably dispersed in a binder resin and used as a conductive material. The conductive material is preferably an anisotropic conductive material.

  The binder resin is not particularly limited. As the binder resin, a known insulating resin is used.

  Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. As for the said binder resin, only 1 type may be used and 2 or more types may be used together.

  Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resins, ethylene-vinyl acetate copolymers, and polyamide resins. Examples of the curable resin include an epoxy resin, a urethane resin, a polyimide resin, and an unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated product of a styrene-butadiene-styrene block copolymer, and a styrene-isoprene. -Hydrogenated product of a styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

  In addition to the conductive particles and the binder resin, the conductive material includes, for example, a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, and a light stabilizer. Various additives such as an agent, an ultraviolet absorber, a lubricant, an antistatic agent and a flame retardant may be contained.

  The method for dispersing the conductive particles in the binder resin is not particularly limited, and a conventionally known dispersion method can be used. Examples of a method for dispersing the conductive particles in the binder resin include a method in which the conductive particles are added to the binder resin and then kneaded and dispersed with a planetary mixer or the like. The conductive particles are dispersed in water. Alternatively, after uniformly dispersing in an organic solvent using a homogenizer or the like, it is added to the binder resin and kneaded with a planetary mixer or the like, and the binder resin is diluted with water or an organic solvent. Then, the method of adding the said electroconductive particle, kneading with a planetary mixer etc. and disperse | distributing is mentioned.

  The conductive material according to the present invention can be used as a conductive paste and a conductive film. When the conductive material according to the present invention is a conductive film, a film that does not include conductive particles may be laminated on a conductive film that includes conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

  In 100% by weight of the conductive material, 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, particularly preferably 70% by weight or more, preferably 99.% or more. It is 99 weight% or less, More preferably, it is 99.9 weight% or less. When the content of the binder resin is not less than the above lower limit and not more than the above upper limit, the conductive particles are efficiently arranged between the electrodes, and the connection reliability of the connection target member connected by the conductive material is further increased.

  In 100% by weight of the conductive material, the content of the conductive particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, preferably 40% by weight or less, more preferably 20% by weight or less, More preferably, it is 10 weight% or less. When the content of the conductive particles is not less than the above lower limit and not more than the above upper limit, the conduction reliability between the electrodes is further enhanced.

(Connection structure)
A connection structure can be obtained by connecting the connection target members using the conductive particles of the present invention or using a conductive material containing the conductive particles and a binder resin.

  The connection structure includes a first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members, and the connection portion is a conductive member of the present invention. The connection structure is preferably formed of conductive particles or formed of a conductive material (such as an anisotropic conductive material) containing the conductive particles and a binder resin. In the case where conductive particles are used, the connection portion itself is conductive particles. That is, the first and second connection target members are connected by the conductive particles.

  In FIG. 4, the connection structure using the electroconductive particle which concerns on the 1st Embodiment of this invention is typically shown with front sectional drawing.

  4 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 that connects the first and second connection target members 52 and 53. Prepare. The connection portion 54 is formed by curing a conductive material including the conductive particles 1. In FIG. 4, the conductive particles 1 are schematically shown for convenience of illustration. Instead of the conductive particles 1, conductive particles 11, 21 and the like may be used.

  The first connection target member 52 has a plurality of electrodes 52b on the upper surface 52a (front surface). The second connection target member 53 has a plurality of electrodes 53b on the lower surface 53a (front surface). The electrode 52 b and the electrode 53 b are electrically connected by one or a plurality of conductive particles 1. Therefore, the first and second connection target members 52 and 53 are electrically connected by the conductive particles 1.

  The manufacturing method of the connection structure is not particularly limited. As an example of the manufacturing method of the connection structure, the conductive material is disposed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated and pressurized. Methods and the like.

The pressure of the said pressurization is about 9.8 * 10 < ⁴ > -4.9 * 10 < ⁶ > Pa. The temperature of the said heating is about 120-220 degreeC.

  Specific examples of the connection target member include electronic components such as semiconductor chips, capacitors, and diodes, and electronic components that are circuit boards such as printed boards, flexible printed boards, glass epoxy boards, and glass boards. The connection target member is preferably an electronic component. The conductive particles are preferably used for electrical connection of electrodes in an electronic component.

  Examples of the electrode provided on the connection target member include metal electrodes such as a gold electrode, a nickel electrode, a tin electrode, an aluminum electrode, a copper electrode, a molybdenum electrode, and a tungsten electrode. When the connection object member is a flexible printed board, the electrode is preferably a gold electrode, a nickel electrode, a tin electrode, or a copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, a copper electrode, a molybdenum electrode, or a tungsten electrode. In addition, when the said electrode is an aluminum electrode, the electrode formed only with aluminum may be sufficient and the electrode by which the aluminum layer was laminated | stacked on the surface of the metal oxide layer may be sufficient. Examples of the material for the metal oxide layer include indium oxide doped with a trivalent metal element and zinc oxide doped with a trivalent metal element. Examples of the trivalent metal element include Sn, Al, and Ga.

  Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. The present invention is not limited only to the following examples.

Example 1
Divinylbenzene copolymer resin particles having a particle size of 3.0 μm (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) were prepared.

  After dispersing 10 parts by weight of the resin particles in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, the resin particles were taken out by filtering the solution. Next, the resin particles were added to 100 parts by weight of a 1% by weight dimethylamine borane solution to activate the surface of the resin particles. The resin particles whose surface was activated were sufficiently washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

  Also prepared is a nickel plating solution (pH 9.0) containing 0.25 mol / L nickel sulfate, 0.25 mol / L sodium hypophosphite, 0.15 mol / L sodium citrate and 0.12 mol / L sodium tungstate. did.

  While stirring the obtained suspension at 70 ° C., the nickel plating solution was gradually dropped into the suspension, and electroless nickel plating was performed for 60 minutes (dropping time). Thereafter, by filtering the suspension, the particles are taken out, washed with water, and dried, so that a nickel-tungsten-phosphorus conductive layer (a crystal layer having a crystal structure, thickness 0.1 μm) is disposed on the surface of the resin particles. Conductive particles were obtained. In Example 1 and Examples 2 to 12 described later, the conductive layer in contact with the base particles (resin particles) was a crystal layer having a crystal structure.

(Example 2)
Resin particle surfaces as in Example 1 except that the pH of the nickel plating solution was changed to 10.0 and the temperature of the suspension when the nickel plating solution was dropped was changed to 80 ° C. Thus, conductive particles were obtained in which a nickel-tungsten-phosphorus conductive layer (crystal layer having a crystal structure, thickness of 0.1 μm) was disposed.

(Example 3)
Divinylbenzene copolymer resin particles having a particle size of 3.0 μm (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) were prepared.

  After dispersing 10 parts by weight of the resin particles in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, the resin particles were taken out by filtering the solution. Next, the resin particles were added to 100 parts by weight of a 1% by weight dimethylamine borane solution to activate the surface of the resin particles. The resin particles whose surface was activated were sufficiently washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

  Also, a nickel plating solution (pH 8.0) containing 0.25 mol / L nickel sulfate, 0.25 mol / L sodium hypophosphite, 0.15 mol / L sodium citrate and 0.12 mol / L sodium tungstate is prepared. did.

  While stirring the obtained suspension at 60 ° C., the nickel plating solution was gradually dropped into the suspension, and electroless nickel plating was performed for 30 minutes. Subsequently, a nickel plating solution (pH 10.0) containing nickel sulfate 0.25 mol / L, sodium hypophosphite 0.25 mol / L, sodium citrate 0.15 mol / L and sodium tungstate 0.12 mol / L. The solution was gradually dropped into the suspension and electroless nickel plating was performed for 30 minutes. Thereafter, by filtering the suspension, the particles are taken out, washed with water, and dried, so that a nickel-tungsten-phosphorus conductive layer (a crystal layer having a crystal structure, thickness 0.1 μm) is disposed on the surface of the resin particles. Conductive particles were obtained.

Example 4
(1) Palladium adhesion process The divinylbenzene resin particle ("Micropearl SP-205" by Sekisui Chemical Co., Ltd.) whose particle diameter is 5.0 micrometers was prepared. The resin particles were etched and washed with water. Next, resin particles were added to 100 mL of a palladium-catalyzed solution containing 8% by weight of a palladium catalyst and stirred. Then, it filtered and wash | cleaned. Resin particles were added to 0.5 wt% dimethylamine borane solution at pH 6 to obtain resin particles to which palladium was attached.

(2) Core substance adhesion step The resin particles to which palladium was adhered were stirred and dispersed in 300 mL of ion exchange water for 3 minutes to obtain a dispersion. Next, 1 g of metallic nickel particle slurry (average particle diameter 100 nm) was added to the dispersion over 3 minutes to obtain resin particles to which the core substance was adhered.

(3) Electroless nickel plating step In the same manner as in Example 1, conductive particles in which a nickel-tungsten-phosphorus conductive layer (a crystal layer having a crystal structure, thickness of 0.1 μm) is disposed on the surface of the resin particles are obtained. It was.

(Example 5)
(1) Production of insulating particles A 1000 mL separable flask equipped with a four-neck separable cover, a stirring blade, a three-way cock, a condenser tube and a temperature probe was charged with 100 mmol methyl methacrylate and N, N, N-trimethyl. Ion-exchanged water containing a monomer composition containing 1 mmol of -N-2-methacryloyloxyethylammonium chloride and 1 mmol of 2,2'-azobis (2-amidinopropane) dihydrochloride so that the solid content is 5% by weight. Then, the mixture was stirred at 200 rpm and polymerized at 70 ° C. for 24 hours under a nitrogen atmosphere. After completion of the reaction, it was freeze-dried to obtain insulating particles having an ammonium group on the surface, an average particle size of 220 nm, and a CV value of 10%.

  The insulating particles were dispersed in ion exchange water under ultrasonic irradiation to obtain a 10 wt% aqueous dispersion of insulating particles.

  10 g of the conductive particles obtained in Example 1 were dispersed in 500 mL of ion exchange water, 4 g of an aqueous dispersion of insulating particles was added, and the mixture was stirred at room temperature for 6 hours. After filtration through a 3 μm mesh filter, the particles were further washed with methanol and dried to obtain conductive particles having insulating particles attached thereto.

  When observed with a scanning electron microscope (SEM), only one coating layer of insulating particles was formed on the surface of the conductive particles. The coverage of the insulating particles with respect to the area of 2.5 μm from the center of the conductive particles by image analysis (that is, the projected area of the particle diameter of the insulating particles) was calculated to be 28%.

(Example 6)
Conductive particles were obtained in the same manner as in Example 1 except that the amount of sodium hypophosphite added was changed from 0.25 mol / L to 0.50 mol / L.

(Example 7)
Conductive particles were obtained in the same manner as in Example 1 except that the amount of sodium hypophosphite added was changed from 0.25 mol / L to 0.05 mol / L.

(Example 8)
Conductive particles were obtained in the same manner as in Example 1 except that the dropping time was changed from 60 minutes to 30 minutes.

Example 9
Conductive particles were obtained in the same manner as in Example 1 except that the dropping time was changed from 60 minutes to 180 minutes.

(Example 10)
Conductive particles having a nickel-molybdenum-phosphorus conductive layer (crystal layer having a crystal structure) were obtained in the same manner as in Example 1 except that sodium tungstate was changed to sodium molybdate.

(Comparative Example 1)
Divinylbenzene copolymer resin particles having a particle size of 3.0 μm (“Micropearl SP-203” manufactured by Sekisui Chemical Co., Ltd.) were prepared.

  After dispersing 10 parts by weight of the resin particles in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, the resin particles were taken out by filtering the solution. Next, the resin particles were added to 100 parts by weight of a 1% by weight dimethylamine borane solution to activate the surface of the resin particles. The resin particles whose surface was activated were sufficiently washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain a suspension.

  Further, a nickel plating solution (pH 7.0) containing 0.25 mol / L of nickel sulfate, 0.25 mol / L of dimethylaminoborane, 0.15 mol / L of sodium citrate and 0.12 mol / L of sodium tungstate was prepared.

  While stirring the obtained suspension at 60 ° C., the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. Subsequently, a nickel plating solution (pH 10.0) containing nickel sulfate 0.25 mol / L, dimethylaminoborane 0.25 mol / L, sodium citrate 0.15 mol / L and sodium tungstate 0.12 mol / L is suspended. The solution was gradually dropped into the solution and electroless nickel plating was performed. Thereafter, by filtering the suspension, the particles are taken out, washed with water, and dried to obtain conductive particles in which a nickel-tungsten-boron conductive layer (thickness 0.1 μm) is arranged on the surface of the resin particles. It was.

(Example 11)
Conductive particles were obtained in the same manner as in Example 1 except that the dropping time was changed from 60 minutes to 5 minutes.

(Example 12)
Conductive particles were obtained in the same manner as in Example 1 except that the dropping time was changed from 60 minutes to 270 minutes.

(Evaluation)
(1) Compressive elastic modulus of conductive particles (5% K value)
The compression modulus (5% K value) of the obtained conductive particles was measured using a micro compression tester (“Fischer Scope H-100” manufactured by Fischer).

(2) Conductive layer cracking test Conductive particles were placed on a table. Using a micro compression tester (“Fischerscope H-100” manufactured by Fischer), a cylinder (diameter 50 μm, manufactured by Diamond) was used as a compression member under the conditions of a compression speed of 0.33 mN / sec and a maximum test load of 10 mN. The smooth end surface of the compression member was lowered toward the conductive particles. The conductive particles were compressed by the smooth end face. Compression was performed until cracking occurred in the conductive layer of the conductive particles. Table 1 below shows the compression displacement of the conductive particles having cracks in the conductive layer with respect to the particle diameter of the conductive particles before compression in the compression direction. Regarding the evaluation results of the compression displacement, the average values of the measured values of the three conductive particles are shown in Table 1 below.

(3) Content of nickel, phosphorus, boron, tungsten and molybdenum in 100% by weight of conductive layer (crystal layer) 5 g of conductive particles are added to a mixed solution of 5 mL of 60% nitric acid and 10 mL of 37% hydrochloric acid, and the conductive layer Was completely dissolved to obtain a solution. Using the obtained solution, the contents of nickel, phosphorus, boron, tungsten and molybdenum were analyzed with an ICP-MS analyzer (manufactured by Hitachi, Ltd.).

  Conductive particles are etched with a focused ion beam (FIB), cross-sectional analysis is observed with a scanning electron microscope, and the content of nickel, phosphorus, boron, tungsten and molybdenum is measured by energy dispersive X-ray analysis. did.

  Distribution of the content of each component in the thickness direction of the conductive layer (the content of each component in the region of 5 nm thickness from the surface (inner surface) of the conductive layer to the side opposite to the base particle (outside) of the conductive layer) About the amount and the content of each component in the region of 5 nm thickness from the surface (outer surface) opposite to the substrate particle side of the conductive particle toward the substrate particle side (inner side) evaluated.

  Using a focused ion beam, a thin film slice of the obtained conductive particles was prepared. Using a transmission electron microscope FE-TEM (“JEM-2010FEF” manufactured by JEOL Ltd.), each content of nickel, phosphorus, boron, tungsten and molybdenum in the conductive layer by an energy dispersive X-ray analyzer (EDS) Was measured.

(4) Plating state The plating state of 50 conductive particles obtained was observed with a scanning electron microscope. The presence or absence of plating unevenness such as plating cracking or plating peeling was observed. The case where the number of conductive particles in which plating unevenness was confirmed was 4 or less was judged as “good”, and the case where the number of conductive particles in which plating unevenness was confirmed was 5 or more was judged as “bad”.

(5) Aggregation state 10 parts by weight of bisphenol A type epoxy resin (“Epicoat 1009” manufactured by Mitsubishi Chemical Corporation), 40 parts by weight of acrylic rubber (weight average molecular weight of about 800,000), 200 parts by weight of methyl ethyl ketone, and microcapsule type curing 50 parts by weight of the agent (“HX3941HP” manufactured by Asahi Kasei Chemicals Co., Ltd.) and 2 parts by weight of the silane coupling agent (“SH6040” manufactured by Toray Dow Corning Silicone Co., Ltd.) are mixed to give a conductive particle content of 3% by weight. Thus, an anisotropic conductive material was obtained.

  The obtained anisotropic conductive material was stored at 25 ° C. for 72 hours. After storage, it was evaluated whether or not the conductive particles aggregated in the anisotropic conductive material were settled. “Good” when the aggregated conductive particles are not settled, “Slightly good” when the aggregated conductive particles are slightly settled to the extent that there is no problem with the conductive connection, the aggregated conductive particles settle The case is judged as “bad”. In addition, when aggregation has arisen, the conduction | electrical_connection defect between electrodes tends to arise and the conduction | electrical_connection reliability between electrodes becomes low.

(6) Connection resistance Fabrication of connection structure:
10 parts by weight of bisphenol A type epoxy resin (“Epicoat 1009” manufactured by Mitsubishi Chemical Corporation), 40 parts by weight of acrylic rubber (weight average molecular weight of about 800,000), 200 parts by weight of methyl ethyl ketone, and a microcapsule type curing agent (Asahi Kasei Chemicals) "HX3941HP" manufactured by HX3941) and 2 parts by weight of a silane coupling agent ("SH6040" manufactured by Toray Dow Corning Silicone Co., Ltd.) are mixed, and the conductive particles are added so that the content is 3% by weight. A resin composition was obtained by dispersing.

  The obtained resin composition was applied to a 50 μm-thick PET (polyethylene terephthalate) film whose one surface was released from the mold, and dried with hot air at 70 ° C. for 5 minutes to produce an anisotropic conductive film. The thickness of the obtained anisotropic conductive film was 12 μm.

  The obtained anisotropic conductive film was cut into a size of 5 mm × 5 mm. The cut anisotropic conductive film is formed of a glass substrate (width 3 cm, length 3 cm) having an aluminum electrode (height 0.2 μm, L / S = 20 μm / 20 μm) having a lead wire for resistance measurement on one side. Affixed almost at the center on the aluminum electrode side. Next, a two-layer flexible printed board (width 2 cm, length 1 cm) having the same aluminum electrode was bonded after being aligned so that the electrodes overlap each other. The laminated body of the glass substrate and the two-layer flexible printed circuit board was thermocompression bonded under pressure bonding conditions of 10 N, 180 ° C., and 20 seconds to obtain a connection structure. A two-layer flexible printed board in which an aluminum electrode is directly formed on a polyimide film was used.

Connection resistance measurement:
The connection resistance between the opposing electrodes of the obtained connection structure was measured by the 4-terminal method. The connection resistance was evaluated according to the following evaluation criteria.

[Evaluation criteria for connection resistance]
○○: Connection resistance is 2.0Ω or less ○: Connection resistance exceeds 2.0Ω, 3.0Ω or less △: Connection resistance exceeds 3.0Ω, 5.0Ω or less ×: Connection resistance exceeds 5.0Ω

(7) Impact resistance The impact resistance was evaluated by dropping the connection structure obtained in the above (6) connection resistance evaluation from a position of 70 cm in height and confirming conduction. The case where the rate of increase in resistance value from the initial resistance value was 50% or less was determined as “good”, and the case where the rate of increase in resistance value from the initial resistance value exceeded 50% was determined as “bad”.

(8) Presence or absence of indentation Using a differential interference microscope, the electrodes provided on the glass substrate are observed from the glass substrate side of the connection structure obtained in (6) Preparation of the connection structure, and conductive particles The presence or absence of formation of indentations on the electrodes in contact with each other was evaluated.

(9) Crystal size Using an X-ray diffractometer ("RINT2500VHF" manufactured by Rigaku Corporation), the natural width of the diffraction line unique to the apparatus depending on the diffraction angle is calculated by function approximation. When it can be assumed that the expansion is “no lattice strain at all”, the half-value width or the integration width representing the expansion is substituted into Scherrer's equation to calculate the crystallite size.

Crystallite size (nm) = K · λ / (β · cos θ)
K: Scherrer constant λ: Wavelength of X-ray tube used β: Spread of diffraction line depending on crystallite size θ: Diffraction angle 2θ / θ

The crystal size was determined according to the following criteria.
[Criteria of crystal size]
A: Crystal size is 50 nm or more and less than 150 nm B: Crystal size is 10 nm or more and less than 50 nm C: Non-crystal

(10) Crystal State The obtained conductive particles were cut, and the presence or absence of crystals in the conductive layer was observed with a transmission electron microscope. The state of crystals was judged according to the following criteria.

[Criteria of crystal state]
A: Crystal layer B: Amorphous layer

  The results are shown in Table 1 below. The presence or absence of the crystal structure in the conductive layer (whether or not it is a crystal layer) is determined by etching the conductive particles with a focused ion beam (FIB) and observing the cross-sectional analysis with a transmission electron microscope. confirmed.

DESCRIPTION OF SYMBOLS 1 ... Conductive particle 1a ... Protrusion 2 ... Base material particle 3 ... Conductive layer (crystal layer)
3a ... projection 4 ... core material 5 ... insulating material 11 ... conductive particles 11a ... projection 12 ... first conductive layer (crystal layer)
DESCRIPTION OF SYMBOLS 13 ... 2nd conductive layer 13a ... Protrusion 21 ... Conductive particle 22 ... Conductive layer 22a ... Crack 51 ... Connection structure 52 ... 1st connection object member 52a ... Upper surface 52b ... Electrode 53 ... 2nd connection object member 53a ... Lower surface 53b ... Electrode 54 ... Connecting portion 71 ... Pad 72 ... Compression member 72a ... Smooth end face

Claims (9)

Having base particles and a conductive layer disposed on the surface of the base particles;
The conductive layer includes a crystal layer having a crystal structure;
The electroconductive particle in which the said crystal layer is in contact with the said base material particle, and the said crystal layer contains nickel and phosphorus.   2. The conductive particle according to claim 1, wherein the content of phosphorus in the total 100 wt% of the crystal layer is 4 wt% or less.   3. The conductive particle according to claim 1, wherein the crystal layer includes a first region and a second region having a higher phosphorus content than the first region.   4. The conductive particle according to claim 3, wherein the second region is located closer to the base particle side in the thickness direction of the crystal layer than the first region.   5. The conductive particle according to claim 3, wherein the phosphorus content in the second region is 2.0% by weight or more higher than the phosphorus content in the first region.   The electroconductive particle of any one of Claims 1-5 whose thickness of the said whole conductive layer is 0.05 micrometer or more and 0.3 micrometer or less.   The electroconductive particle of any one of Claims 1-6 in which the said electroconductive layer has a processus | protrusion on an outer surface.   The electroconductive material containing the electroconductive particle of any one of Claims 1-7, and binder resin. A first connection target member, a second connection target member, and a connection portion connecting the first and second connection target members;
A connection structure in which the connection portion is formed of the conductive particles according to any one of claims 1 to 7, or is formed of a conductive material including the conductive particles and a binder resin.

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