Conductive particles, conductive material, and connection structure

Abstract

Provided are conductive particles capable of achieving both low connection resistance and high conduction reliability even when electrodes are electrically connected at relatively low pressure.　Conductive particles according to the present invention comprise a base material particle and a conductive layer disposed on the surface of the base material particle. In a correlation diagram of a compression test in which the conductive particles are compressed, with compression displacement on the X-axis and compression load on the Y-axis, a variation indicating brittle fracture of the conductive layer is observed in the correlation line before a variation indicating destruction of the base material particle is observed.

Description

Conductive particles, conductive materials and connection structures

[0001] The present invention relates to a conductive particle including a base particle and a conductive layer disposed on the surface of the base particle. The present invention also relates to a conductive material and a connection structure using the conductive particle.

[0002] Anisotropic conductive materials such as anisotropic conductive pastes and anisotropic conductive films are widely known, and in these anisotropic conductive materials, conductive particles are dispersed in a binder resin.

[0003] The anisotropic conductive material is used to electrically connect electrodes of various connection target components such as flexible printed circuit boards (FPCs), glass substrates, and semiconductor chips to obtain connection structures. Furthermore, as the conductive particles, conductive particles having a base particle and a conductive layer disposed on the surface of the base particle may be used.

[0004] As an example of the above-mentioned conductive particles, Patent Document 1 listed below discloses conductive particles obtained by a coating step in which a conductive metal layer containing nickel is formed on the surface of resin particles to produce metal-coated particles, and a heat treatment step in which the metal-coated particles are subjected to a heat treatment at a temperature of 180°C to 350°C in a non-oxidizing atmosphere.

[0005] Furthermore, Patent Document 2 listed below discloses a conductive particle having a base particle and a conductive metal layer covering the outer surface of the base particle. The conductive metal layer includes a nickel plating layer. When a cross section of the nickel plating layer is observed in the thickness direction at a magnification of 100,000 times using a scanning electron microscope, grain boundaries are observed in the cross section, and the grain boundary structure is not a columnar structure oriented in the thickness direction of the nickel plating layer.

[0006] JP 2013-008474 A JP 2013-073694 A

[0007] In recent years, when electrically connecting electrodes using a conductive material or connecting material containing conductive particles, it has been desired to ensure reliable electrical connection between electrodes and reduce connection resistance even at relatively low pressure. For example, in a method for manufacturing a liquid crystal display device, when mounting a flexible substrate in a connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass) method), an anisotropic conductive material is placed on the glass substrate, the flexible substrate is laminated, and thermocompression bonding is performed. With the recent trend toward more flexible adherends (electrodes) and thinner glass substrates, it is desirable to perform thermocompression bonding at relatively low pressure when mounting a flexible substrate using the FOG method. Furthermore, even in methods other than the FOG method, relatively low pressure and temperature during thermocompression bonding are sometimes required.

[0008] When conventional conductive particles such as those described in Patent Documents 1 and 2 are used to electrically connect electrodes at a relatively low pressure, the connection resistance may become high. This is due to the fact that it is difficult to increase the contact area between the electrode and the conductive particles due to insufficient deformation of the conductive particles, and that it is difficult to form recesses (indentations) formed by pressing the conductive particles into the electrode.

[0009] That is, when conventional conductive particles are used to electrically connect electrodes at a relatively low pressure, it is difficult to achieve both low connection resistance and high electrical conductivity reliability.

[0010] An object of the present invention is to provide conductive particles that can achieve both low connection resistance and high conduction reliability even when electrodes are electrically connected at a relatively low pressure. Another object of the present invention is to provide a conductive material and a connection structure using the conductive particles.

[0011] The present specification discloses the following conductive particles, conductive materials, and connection structures.

[0012] Item 1. A conductive particle comprising a base particle and a conductive layer disposed on a surface of the base particle, wherein, in a compression test in which the conductive particle is compressed, a fluctuation indicative of brittle fracture of the conductive layer is observed before a fluctuation indicative of fracture of the base particle is observed in a correlation line in a correlation diagram in which compressive displacement is on the X axis and compressive load is on the Y axis.

[0013] Item 2. The conductive particle according to Item 1, wherein a fluctuation indicating brittle fracture of the conductive layer is observed in the correlation line until the conductive particle is compressed by 30%.

[0014] Item 3. The conductive particle according to Item 1 or 2, wherein in the correlation line, the ratio of the amount of fluctuation in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer to a value twice the thickness of the conductive layer is 0.70 or less.

[0015] Item 4. The conductive particle according to any one of Items 1 to 3, wherein the conductive layer contains nickel as a primary metal, and the average nickel content in a region extending from the inner surface of the conductive layer to half the thickness thereof toward the outside is lower than the average nickel content in a region extending from the outer surface of the conductive layer to half the thickness thereof toward the inside.

[0016] Item 5. A conductive particle comprising a base particle and a conductive layer disposed on a surface of the base particle, the conductive layer containing nickel as a primary metal, the conductive layer containing elements other than nickel in both a region extending from the inner surface of the conductive layer to half its thickness outward and a region extending from the outer surface of the conductive layer to half its thickness inward, and the average nickel content in the region extending from the inner surface of the conductive layer to half its thickness outward is lower than the average nickel content in the region extending from the outer surface of the conductive layer to half its thickness inward.

[0017] Item 6. The compressive modulus of elasticity when the base particle is compressed by 10% is 3000 N / mm ２ More than 20000N / mm ２ Item 6. The conductive particle according to any one of items 1 to 5, wherein:

[0018] Item 7. The conductive particles according to any one of Items 1 to 6, wherein the particle diameter of the conductive particles is 8.0 μm or less.

[0019] Item 8. The conductive particle according to any one of Items 1 to 7, wherein the conductive particle comprises an insulating material disposed on an outer surface of the conductive layer.

[0020] Item 9. The conductive particle according to any one of Items 1 to 8, wherein the conductive particle has protrusions on the outer surface of the conductive layer.

[0021] Item 10. A conductive material comprising the conductive particles according to any one of items 1 to 9 and a binder resin.

[0022] Item 11. A connection structure comprising a first connection-target member having a first electrode on its surface, a second connection-target member having a second electrode on its surface, and a connection portion connecting the first connection-target member and the second connection-target member, wherein a material of the connection portion contains the conductive particles according to any one of Items 1 to 9, and the first electrode and the second electrode are electrically connected by the conductive particles.

[0023] The conductive particle according to the present invention comprises a base particle and a conductive layer disposed on the surface of the base particle, and in a compression test in which the conductive particle is compressed, a fluctuation in the correlation line indicative of brittle fracture of the conductive layer is observed before a fluctuation in the correlation line indicative of fracture of the base particle is observed in a correlation diagram in which the compressive displacement is on the X axis and the compressive load is on the Y axis. Because the conductive particle according to the present invention has the above-mentioned configuration, it is possible to achieve both low connection resistance and high conduction reliability even when electrodes are electrically connected at a relatively low pressure.

[0024] Another conductive particle according to the present invention comprises a base particle and a conductive layer disposed on the surface of the base particle, the conductive layer containing nickel as a primary metal, and the conductive layer containing elements other than nickel in both a region extending from the inner surface of the conductive layer to half its thickness outward and a region extending from the outer surface of the conductive layer to half its thickness inward. In the conductive particle, the average nickel content in the region extending from the inner surface of the conductive layer to half its thickness outward is lower than the average nickel content in the region extending from the outer surface of the conductive layer to half its thickness inward. Because the conductive particle according to the present invention has the above-described configuration, it can achieve both low connection resistance and high electrical reliability even when electrodes are electrically connected at a relatively low pressure.

[0025] FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention. FIG. 3 is a cross-sectional view schematically showing a conductive particle according to a third embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a region with a thickness of 1 / 2 extending from the inner surface of the conductive layer toward the outside, and a region with a thickness of 1 / 2 extending from the outer surface of the conductive layer toward the inside. FIG. 5 is a cross-sectional view schematically showing a connection structure using the conductive particle shown in FIG. 1. FIG. 6 is a correlation diagram showing a correlation line between compressive displacement (X-axis) and compressive load (Y-axis) in a compression test of a conductive particle according to one embodiment of the present invention.

[0026] The present invention will be described in detail below.

[0027] (Conductive Particle) The conductive particle according to the present invention comprises a base particle and a conductive layer disposed on the surface of the base particle. In the conductive particle according to the present invention, in a compression test in which the conductive particle is compressed, a fluctuation indicative of brittle fracture of the conductive layer is observed before a fluctuation indicative of fracture of the base particle is observed on a correlation line (hereinafter sometimes referred to as a "correlation line") in a correlation diagram in which the compressive displacement is on the X axis and the compressive load is on the Y axis.

[0028] That is, in the conductive particles according to the present invention, brittle fracture of the conductive layer occurs before fracture of the base particle in a compression test in which the conductive particles are compressed. In the conductive particles, brittle fracture of the conductive layer occurs before fracture of the base particle in a compression test in which the conductive particles are compressed. In the present invention, fracture of the base particle refers to fracture occurring in at least a portion of the base particle. In this case, complete fracture may occur in the base particle. Note that in the conductive particles, fracture of the base particle may not occur in a compression test in which the conductive particles are compressed. In addition, in the present invention, brittle fracture of the conductive layer refers to brittle fracture occurring in at least a portion of the conductive layer. Brittle fracture, as defined in the English-Japanese Plastics Industry Dictionary (first edition, second printing published on December 1, 1973, published by the Industrial Research Institute), refers to "fracture in which cracks propagate rapidly with little or no deformation of the plastic."

[0029] In the present invention, the fluctuation indicating fracture of the base particle refers to a fluctuation in the X-axis displacement in a section of the correlation line where there is no Y-axis displacement relative to the X-axis displacement, where the X-axis displacement in the section is 1 / 5 or more of the particle diameter of the conductive particle. Furthermore, the fluctuation indicating brittle fracture of the conductive layer refers to a fluctuation in the compressive displacement within a compressive load value of 1.0 mN, determined based on a section of the correlation line where the compressive displacement (X-axis) changes discontinuously at a slight difference in compressive load (Y-axis) (for example, a compressive load value difference of 1.0 mN), where the amount of change in compressive displacement is less than twice the thickness of the conductive layer.

[0030] The brittle fracture of the conductive layer is clearly different from plating cracks of the conductive layer. In the present invention, plating cracks of the conductive layer are determined based on a section of the correlation line where the compressive displacement (X-axis) changes discontinuously at a slight difference in compressive load (Y-axis) (for example, a difference in compressive load value of 1.0 mN), and refer to a fluctuation in the compressive displacement exceeding twice the thickness of the conductive layer within a range of a compressive load value of 1.0 mN. In the conductive particles, plating cracks of the conductive layer may or may not occur in a compression test in which the conductive particles are compressed. From the viewpoint of further reducing the connection resistance between electrodes and further improving the conduction reliability, it is preferable that the conductive particles do not cause plating cracks of the conductive layer in a compression test in which the conductive particles are compressed.

[0031] The conductive particles according to the present invention have the above-described configuration, and therefore, when electrically connecting electrodes, the contact area between the electrodes and the conductive particles can be increased due to the occurrence of brittle fracture in the conductive layer. As a result, even when electrically connecting electrodes using the conductive particles at a relatively low pressure, both low connection resistance and high conductivity reliability can be achieved. Furthermore, when the conductive particles are used as spacer particles, gap controllability can be improved.

[0032] Another conductive particle according to the present invention comprises a substrate particle and a conductive layer disposed on the surface of the substrate particle, the conductive layer containing nickel as a primary metal, and the conductive layer containing elements other than nickel in both a region extending from the inner surface of the conductive layer to half its thickness outward and a region extending from the outer surface of the conductive layer to half its thickness inward. In the conductive particle, the average nickel content in the region extending from the inner surface of the conductive layer to half its thickness outward is lower than the average nickel content in the region extending from the outer surface of the conductive layer to half its thickness inward. In this specification, the term "average content" refers to the average content on a weight percent basis.

[0033] The conductive particles according to the present invention have the above-described configuration, and therefore can increase the contact area between the electrodes and the conductive particles when electrically connecting the electrodes. As a result, even when the conductive particles are used to electrically connect the electrodes at a relatively low pressure, both low connection resistance and high electrical conductivity reliability can be achieved. Furthermore, when the conductive particles are used as spacer particles, gap controllability can be improved.

[0034] FIG. 6 is a correlation diagram showing a correlation line between compression displacement (X axis) and compression load (Y axis) in a compression test of a conductive particle according to one embodiment of the present invention.

[0035] In the conductive particles according to one embodiment of the present invention, for example, a correlation diagram showing a correlation line between compressive displacement (X axis) and compressive load (Y axis) in a compression test as shown in FIG. 6 can be obtained.

[0036] In the correlation line in the correlation diagram shown in Figure 6, a fluctuation indicative of brittle fracture of the conductive layer is observed before a fluctuation indicative of fracture of the base particle is observed. In the correlation line in the correlation diagram shown in Figure 6, a fluctuation indicative of fracture of the base particle is not observed.

[0037] In the correlation line, fluctuations indicating brittle fracture of the conductive layer are preferably observed until the conductive particles are compressed by 60%, more preferably until 50%, even more preferably until 40%, and particularly preferably until 30%. In these cases, the connection resistance between the electrodes can be further reduced. In particular, if fluctuations indicating brittle fracture of the conductive layer are observed in the correlation line until the conductive particles are compressed by 30%, the connection resistance between the electrodes can be further reduced. Note that, in the correlation line, fluctuations indicating brittle fracture of the conductive layer do not necessarily have to be observed until the conductive particles are compressed by 10%, or even until 20%.

[0038] In the correlation line, fluctuations indicating the destruction of the base particle are preferably not observed until the conductive particle is compressed by 20%, more preferably not until the conductive particle is compressed by 30%, even more preferably not until the conductive particle is compressed by 40%, and particularly preferably not until the conductive particle is compressed by 60%. In these cases, the connection resistance between the electrodes can be further reduced. Furthermore, fluctuations indicating the destruction of the base particle do not need to be observed in the correlation line.

[0039] From the viewpoint of more effectively exerting the effects of the present invention, it is preferable that in the conductive particles, a fluctuation indicating brittle fracture of the conductive layer is observed in the correlation line before a fluctuation indicating plating cracks in the conductive layer is observed.

[0040] In the correlation line, fluctuations indicating plating cracks in the conductive layer are preferably not observed until the conductive particles are compressed by 20%, more preferably not observed until 30%, even more preferably not observed until 40%, and particularly preferably not observed until 60%. In these cases, the connection resistance between the electrodes can be further reduced. From the viewpoint of further reducing the connection resistance between the electrodes, it is most preferable that fluctuations indicating plating cracks in the conductive layer are not observed in the correlation line.

[0041] In the correlation line, the absolute value of the difference between the compressive displacement at the start point of brittle fracture of the conductive layer and the compressive displacement at the end point of brittle fracture of the conductive layer is the fluctuation amount of the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer ("V" in FIG. 6). Note that in the correlation line, the fluctuation amount of the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer is equal to or less than twice the thickness of the conductive layer. In the correlation line, the fluctuation amount of the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer is preferably 20 nm or more, more preferably 30 nm or more, even more preferably 50 nm or more, and preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less. When the fluctuation amount of the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between the electrodes can be further reduced.

[0042] In the correlation line, the ratio of the amount of change in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer to twice the value of the thickness of the conductive layer is defined as the ratio (the amount of change in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer / twice the value of the thickness of the conductive layer). In the correlation line, the ratio (the amount of change in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer / twice the value of the thickness of the conductive layer) is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and preferably 1.00 or less, more preferably 0.70 or less, even more preferably 0.65 or less, and particularly preferably 0.60 or less. When the ratio (the amount of change in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer / twice the value of the thickness of the conductive layer) is above the lower limit and below the upper limit, the connection resistance between the electrodes can be further reduced.

[0043] The compression test for compressing the conductive particles is carried out, for example, as follows: Using a micro-compression tester, a load (reversed load value) is applied with the end face of a smooth cylindrical indenter (diameter 100 μm, made of diamond) until the conductive particles are compressed and deformed by 50% under conditions of 25°C, a compression speed of 0.3 mN / sec, and a maximum test load of 20 mN. As the micro-compression tester, for example, the "Fisherscope H-100" manufactured by Fischer is used.

[0044] The following methods can be used to control the fluctuations in the correlation line that indicate brittle fracture of the conductive layer and the fluctuations that indicate fracture of the base particle so that they satisfy the above-mentioned preferred aspects: A method of making the conductive layer brittle by incorporating an excess of a secondary element only into the conductive layer near the surface of the base particle; A method of forming metal defects in the conductive layer by reacting at a low temperature only when forming the conductive layer near the surface of the base particle.

[0045] The compressive elastic modulus (10% K value) of the conductive particles when compressed by 10% is preferably 5000 N / mm ２ More preferably, 6000 N / mm ２ More preferably, 7000 N / mm ２ More preferably, 8000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ When the 10% K value of the conductive particles is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between electrodes can be further reduced.

[0046] The compressive elastic modulus (20% K value) when the conductive particles are compressed by 20% is preferably 5000 N / mm ２ More preferably, 6000 N / mm ２ More preferably, 7000 N / mm ２ More preferably, 8000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ When the 20% K value of the conductive particles is equal to or greater than the above lower limit and equal to or less than the above upper limit, the connection resistance between electrodes can be further reduced.

[0047] The compressive elastic modulus (30% K value) when the conductive particles are compressed by 30% is preferably 5000 N / mm ２ More preferably, 6000 N / mm ２ More preferably, 7000 N / mm ２ More preferably, 8000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ or less. If the 30% K value of the conductive particles is equal to or greater than the lower limit, when electrodes are connected using the conductive particles, the conductive particles can be pressed strongly into the electrodes, thereby further reducing the connection resistance between the electrodes. If the 30% K value of the conductive particles is equal to or less than the upper limit, when electrodes are connected using the conductive particles, the conductive particles are appropriately deformed, thereby sufficiently increasing the contact area between the conductive particles and the electrodes, thereby further reducing the connection resistance between the electrodes.

[0048] The 10% K value, 20% K value, and 30% K value of the conductive particles can be measured as follows.

[0049] Using a micro-compression tester, the conductive particles are compressed with a smooth cylindrical indenter end face (diameter 50 μm, made of diamond) under conditions of 25°C and a maximum test load of 90 mN for 30 seconds. The load value (N) and compression displacement (mm) at this time are measured. From the obtained measured values, the compressive elastic modulus can be calculated using the following formula. As the micro-compression tester, for example, a Fischerscope H-100 manufactured by Fischer can be used.

[0050] K value (N / mm ２ ) = (3 / 2 １／２ ) F.S. －３／２ ・R －１／２ F: Load value (N) when the conductive particle is compressed and deformed by 10%, 20%, or 30%; S: Compression displacement (mm) when the conductive particle is compressed and deformed by 10%, 20%, or 30%; R: Radius of the conductive particle (mm).

[0051] From the viewpoint of further reducing the connection resistance between electrodes, the compression recovery rate of the conductive particles is preferably 50% or more, more preferably 55% or more, and even more preferably 60% or more, and is preferably 95% or less, more preferably 90% or less, and even more preferably 85% or less.

[0052] The compression recovery rate can be measured as follows.

[0053] Conductive particles are scattered on a sample stage. For each scattered conductive particle, a micro-compression tester is used, and a load (reversed load value) is applied at 25°C toward the center of the conductive particle with the end face of a smooth cylindrical indenter (diameter 100 μm, made of diamond) until the conductive particle is compressed and deformed by 33%. The load is then released to the origin load value (0.40 mN). The load-compression displacement during this period is measured, and the compression recovery rate can be calculated using the following formula. The loading rate is 0.33 mN / sec. For example, a Fischerscope H-100 manufactured by Fischer is used as the micro-compression tester.

[0054] Compression recovery rate (%) = [L2 / L1] x 100 L1: Compression displacement from the load value for origin when applying a load to the reverse load value L2: Unloading displacement from the reverse load value when releasing the load to the load value for origin

[0055] The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 1.5 μm or more, particularly preferably 2.0 μm or more, and preferably 500 μm or less, more preferably 300 μm or less, even more preferably 100 μm or less, particularly preferably 10 μm or less, and most preferably 8.0 μm or less. When the particle diameter of the conductive particles is above the above lower limit and below the above upper limit, when electrodes are connected using the conductive particles, the contact area between the conductive particles and the electrodes is sufficiently large, and agglomerated conductive particles are less likely to form when forming a conductive layer. In addition, the gap between the electrodes connected via the conductive particles is not too large, and the conductive layer is less likely to peel off from the surface of the base particle. In addition, when the particle diameter of the conductive particles is above the above lower limit and below the above upper limit, the conductive particles can be suitably used for conductive material applications.

[0056] The particle diameter of the conductive particles is preferably an average particle diameter, and more preferably a number average particle diameter. The particle diameter of the conductive particles can be determined, for example, by observing 50 random conductive particles with an electron microscope or optical microscope and calculating the average particle diameter of each conductive particle, or by performing laser diffraction particle size distribution measurement. In observation with an electron microscope or optical microscope, the particle diameter of each conductive particle is determined as the particle diameter in equivalent circle diameter. In observation with an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random conductive particles is approximately equal to the average particle diameter in equivalent sphere diameter. In laser diffraction particle size distribution measurement, the particle diameter of each conductive particle is determined as the particle diameter in equivalent sphere diameter. The particle diameter of the conductive particles is preferably calculated by laser diffraction particle size distribution measurement.

[0057] The present invention will be specifically described below with reference to the drawings.

[0058] FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention.

[0059] The conductive particle 1 shown in Fig. 1 has a base particle 2 and a conductive layer 3. The conductive layer 3 is disposed on the surface of the base particle 2. In the first embodiment, the conductive layer 3 is in contact with 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. In the conductive particle 1, the conductive layer 3 is a single-layer conductive layer.

[0060] Unlike conductive particles 21 described later, conductive particles 1 do not have a core substance. Conductive particles 1 do not have protrusions on their surfaces, and there are no protrusions on the outer surface of conductive layer 3. Conductive particles 1 are spherical.

[0061] As described above, the conductive particles according to the present invention may not have protrusions on their surfaces, may not have protrusions on the outer surface of the conductive layer, and may be spherical. Furthermore, unlike the conductive particles 21 described below, the conductive particles 1 do not have an insulating material. However, the conductive particles 1 may have an insulating material disposed on the outer surface of the conductive layer 3.

[0062] FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention.

[0063] The conductive particle 11 shown in Fig. 2 has a base particle 2 and a conductive layer 13. The conductive layer 13 is disposed on the surface of the base particle 2 so as to be in contact with the base particle 2. In the conductive particle 11, the conductive layer 13 is a two-layer conductive layer. The conductive layer 13 as a whole has a first conductive layer 13A on the side facing the base particle 2 and a second conductive layer 13B on the side opposite the side facing the base particle 2.

[0064] The only difference between the conductive particle 1 and the conductive particle 11 is the conductive layer. That is, the conductive particle 1 has a single-layer conductive layer 3, whereas the conductive particle 11 has a two-layer structure consisting of a first conductive layer 13A and a second conductive layer 13B. The first conductive layer 13A and the second conductive layer 13B are formed as separate conductive layers.

[0065] The first conductive layer 13A is disposed on the surface of the base particle 2. The first conductive layer 13A is disposed between the base particle 2 and the second conductive layer 13B. The first conductive layer 13A is in contact with the base particle 2. Therefore, the first conductive layer 13A is disposed on the surface of the base particle 2, and the second conductive layer 13B is disposed on the surface of the first conductive layer 13A.

[0066] FIG. 3 is a cross-sectional view schematically showing a conductive particle according to a third embodiment of the present invention.

[0067] 3 includes a base particle 2, a conductive layer 23, a plurality of core materials 24, and a plurality of insulating materials 25. The conductive layer 23 is disposed on the surface of the base particle 2 so as to be in contact with the base particle 2. In the conductive particle 21, the conductive layer 23 is a single-layer conductive layer.

[0068] The conductive particle 21 has a plurality of protrusions 21a on its surface. The conductive layer 23 has a plurality of protrusions 23a on its outer surface. A plurality of core materials 24 are disposed on the surface of the base particle 2. The plurality of core materials 24 are embedded in the conductive layer 23. The core materials 24 are disposed inside the protrusions 21a, 23a. The conductive layer 23 covers the plurality of core materials 24. The outer surface of the conductive layer 23 is raised by the plurality of core materials 24, forming the protrusions 21a, 23a.

[0069] The conductive particles 21 have an insulating material 25 disposed on the outer surface of the conductive layer 23. At least a portion of the outer surface of the conductive layer 23 is coated with the insulating material 25. The insulating material 25 is formed from a material having insulating properties and is an insulating particle. In this way, the conductive particles according to the present invention may have an insulating material disposed on the outer surface of the conductive layer. However, the conductive particles according to the present invention do not necessarily have to have an insulating material.

[0070] Other details of the conductive particles will be described below. In the following description, "(meth)acrylic" means either or both of "acrylic" and "methacrylic", and "(meth)acrylate" means either or both of "acrylate" and "methacrylate".

[0071] [Base Particles] Examples of the base particles include resin particles, inorganic particles excluding metal particles, organic-inorganic hybrid particles, and metal particles. The base particles may be core-shell particles having a core and a shell disposed on the surface of the core. The core may be an organic core. The shell may be an inorganic shell.

[0072] The base particles are preferably resin particles formed from a resin, since this further enhances the effects of the present invention. When connecting electrodes using the conductive particles, the conductive particles are placed between the electrodes and then compressed by pressure bonding. If the base particles are resin particles, the conductive particles are more likely to deform during pressure bonding, increasing the contact area between the conductive particles and the electrodes. This further improves the reliability of conduction between the electrodes.

[0073] As the resin that is the material of the resin particles, various organic substances can be suitably used.As the resin that is the material of the resin particles, for example, can be enumerated: polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, polybutadiene and other polyolefin resins; acrylic resins such as polymethyl methacrylate and polymethyl acrylate; polyalkylene 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, polyetheretherketone, polyethersulfone, and the polymer obtained by polymerizing one or more of various polymerizable monomers having ethylenic unsaturated groups. Since the hardness of the base particle can be easily controlled within a suitable range, it is preferable that the resin for forming the resin particles is a polymer obtained by polymerizing one or more polymerizable monomers having multiple ethylenically unsaturated groups.

[0074] When the resin particles are obtained by polymerizing a polymerizable monomer having an ethylenically unsaturated group, the polymerizable monomer having an ethylenically unsaturated group may be a non-crosslinkable monomer or a crosslinkable monomer.

[0075] Examples of the non-crosslinkable monomer include styrene-based monomers such as styrene and α-methylstyrene; carboxyl group-containing monomers such as (meth)acrylic acid, maleic acid, and maleic anhydride; methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, cyclohexyl (meth)acrylate, and isobornyl Examples of the monomer include alkyl (meth)acrylate compounds such as (meth)acrylate; oxygen atom-containing (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, and glycidyl (meth)acrylate; nitrile-containing monomers such as (meth)acrylonitrile; and halogen-containing monomers such as trifluoromethyl (meth)acrylate, pentafluoroethyl (meth)acrylate, vinyl chloride, vinyl fluoride, and chlorostyrene.

[0076] Examples of the crosslinkable monomer include tetramethylolmethane tetra(meth)acrylate, tetramethylolmethane tri(meth)acrylate, tetramethylolmethane di(meth)acrylate, trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol penta(meth)acrylate, glycerol tri(meth)acrylate, glycerol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly) Examples of suitable monomers include polyfunctional (meth)acrylate compounds such as propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate; and silane-containing monomers such as triallyl (iso)cyanurate, triallyl trimellitate, divinylbenzene, diallyl phthalate, diallyl acrylamide, diallyl ether, γ-(meth)acryloxypropyltrimethoxysilane, trimethoxysilylstyrene, and vinyltrimethoxysilane.

[0077] The resin particles can be obtained by polymerizing the polymerizable monomer having an ethylenically unsaturated group by a known method, such as a suspension polymerization method in the presence of a radical polymerization initiator, or a method in which non-crosslinked seed particles are used to swell and polymerize the monomer together with the radical polymerization initiator.

[0078] When the base particles are inorganic particles other than metal particles or organic-inorganic hybrid particles, examples of the inorganic material of the base particles include silica and carbon black. Preferably, the inorganic material is not metal. The particles formed from silica are not particularly limited. Examples of the particles formed from silica include particles obtained by hydrolyzing a silicon compound having two or more hydrolyzable alkoxysilyl groups to form crosslinked polymer particles, and then optionally baking the particles. Examples of the organic-inorganic hybrid particles include organic-inorganic hybrid particles formed from a crosslinked alkoxysilyl polymer and an acrylic resin.

[0079] When the base particles are metal particles, examples of the metal particles include silver, copper, nickel, silicon, gold, titanium, etc. However, the base particles are preferably not metal particles, and are preferably not copper particles.

[0080] The compressive elastic modulus (10% K value) when the base particle is compressed by 10% is preferably 3000 N / mm ２ More preferably, 4000 N / mm ２ More preferably, 6000 N / mm ２ More preferably, 7000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ Below 20,000 N / mm, most preferably ２or less. When the 10% K value of the base particle is equal to or greater than the above lower limit, the effects of the present invention can be more effectively exhibited. When the 10% K value of the base particle is equal to or greater than the above lower limit, when electrodes are connected using conductive particles, the connection resistance between the electrodes can be further reduced. When the 10% K value of the conductive particle is equal to or less than the above upper limit, the conductive particle is appropriately deformed, thereby sufficiently increasing the contact area between the conductive particle and the electrode, and further reducing the connection resistance between the electrodes.

[0081] The compressive elastic modulus (20% K value) when the base particle is compressed by 20% is preferably 3000 N / mm ２ More preferably, 3500 N / mm ２ More preferably, 6000 N / mm ２ More preferably, 7000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ Below 20,000 N / mm, most preferably ２ or less. When the 20% K value of the base particle is equal to or greater than the lower limit, the effects of the present invention can be more effectively exhibited. When the 20% K value of the base particle is equal to or greater than the lower limit, when electrodes are connected using the conductive particles, the conductive particles can be pressed strongly into the electrodes, thereby further reducing the connection resistance between the electrodes. When the 20% K value of the conductive particles is equal to or less than the upper limit, when electrodes are connected using the conductive particles, the conductive particles are appropriately deformed, thereby sufficiently increasing the contact area between the conductive particles and the electrodes, thereby further reducing the connection resistance between the electrodes.

[0082] The compressive modulus of elasticity (30% K value) when the base particle is compressed by 30% is preferably 3000 N / mm ２ More preferably, 4000 N / mm ２ More preferably, 5000 N / mm ２ More preferably, 6000 N / mm ２More preferably, 7000 N / mm ２ or more, preferably 40,000 N / mm ２ or less, more preferably 35,000 N / mm ２ or less, more preferably 30,000 N / mm ２ Below, particularly preferably 25000 N / mm ２ or less. When the 30% K value of the base particle is equal to or greater than the lower limit, the effects of the present invention can be more effectively exhibited. When the 30% K value of the base particle is equal to or greater than the lower limit, when electrodes are connected using the conductive particles, the conductive particles can be pressed strongly into the electrodes, thereby further reducing the connection resistance between the electrodes. When the 30% K value of the conductive particles is equal to or less than the upper limit, when electrodes are connected using the conductive particles, the conductive particles are appropriately deformed, thereby sufficiently increasing the contact area between the conductive particles and the electrodes, thereby further reducing the connection resistance between the electrodes.

[0083] The ratio of the compressive modulus when the base particle is compressed 10% to the compressive modulus when the conductive particle is compressed 10% is preferably 0.25 or more, more preferably 0.3 or more, even more preferably 0.4 or more, and is preferably 1.5 or less, more preferably 1.0 or less, and even more preferably 0.9 or less. When the ratio (10% K value of base particle / 10% K value of conductive particle) is equal to or greater than the lower limit and equal to or less than the upper limit, when electrodes are connected using the conductive particles, the conductive particles can be pressed strongly into the electrodes, thereby further reducing the connection resistance between the electrodes.

[0084] The 10% K value, 20% K value, and 30% K value of the base particle can be measured in the same manner as the 10% K value, 20% K value, and 30% K value of the conductive particle.

[0085] The particle diameter of the base particle is preferably 0.1 μm or more, more preferably 0.5 μm or more, even more preferably 1.0 μm or more, particularly preferably 1.5 μm or more, and preferably 500 μm or less, more preferably 300 μm or less, even more preferably 50 μm or less, even more preferably 30 μm or less, particularly preferably 10 μm or less, and most preferably 8.0 μm or less. When the particle diameter of the base particle is above the lower limit, the contact area between the conductive particles and the electrode is increased, thereby further improving the electrical connection reliability between the electrodes and further reducing the connection resistance between the electrodes connected via the conductive particles. Furthermore, when a conductive layer is formed on the surface of the base particle by electroless plating, aggregation is less likely to occur, and aggregated conductive particles are less likely to be formed. When the particle diameter of the base particle is below the upper limit, the conductive particles are easily compressed sufficiently, further reducing the connection resistance between the electrodes and further reducing the gap between the electrodes.

[0086] The particle diameter of the base particles refers to the number average particle diameter. The particle diameter of the base particles is determined using a particle size distribution measuring device or the like. The particle diameter of the base particles is preferably determined by observing 50 random base particles with an electron microscope or optical microscope and calculating the average value. When observed with an electron microscope or optical microscope, the particle diameter of each base particle is determined as the particle diameter in equivalent circle diameter. When observed with an electron microscope or optical microscope, the average particle diameter in equivalent circle diameter of 50 random base particles is approximately equal to the average particle diameter in equivalent sphere diameter. When observed with a particle size distribution measuring device, the particle diameter of each base particle is determined as the particle diameter in equivalent sphere diameter. The particle diameter of the base particles is preferably calculated using a particle size distribution measuring device. When measuring the particle diameter of the base particles in the conductive particles, it can be measured, for example, as follows.

[0087] The conductive particles were added to Kulzer's Technovit 4000 to a content of 30 wt % and dispersed to prepare an embedding resin for conductive particle inspection. An ion milling machine (Hitachi High-Technologies Corporation's IM4000) was used to cut out a cross section of the conductive particles dispersed in the embedding resin, passing through the vicinity of the center of the base particle. Then, using a field emission scanning electron microscope (FE-SEM) with an image magnification set to 25,000x, 50 conductive particles were randomly selected and the base particle of each conductive particle was observed. The particle diameter of the base particle for each conductive particle was measured, and the arithmetic average was calculated to determine the particle diameter of the base particle.

[0088] [Conductive Layer] The metal for forming the conductive layer is not particularly limited. Examples of the metal include gold, silver, palladium, copper, platinum, zinc, iron, tin, lead, ruthenium, aluminum, cobalt, indium, nickel, chromium, titanium, antimony, bismuth, thallium, germanium, cadmium, silicon, and alloys thereof. Other examples of the metal include tin-doped indium oxide (ITO) and solder.

[0089] From the viewpoint of more effectively reducing the connection resistance between electrodes, the conductive layer preferably contains silver, tin, copper, or nickel, and more preferably contains nickel, in which case the metal such as nickel may be alloyed with another metal.

[0090] The conductive layer preferably contains nickel as a primary metal. In the present invention, the primary metal refers to the metal contained in the conductive layer with the largest content. In the present invention, the primary metal is preferably a metal whose content in 100% by weight of the conductive layer is 30% by weight or more, more preferably a metal whose content in 100% by weight of the conductive layer is 50% by weight or more, and even more preferably a metal whose content in 100% by weight of the conductive layer is more than 50% by weight.

[0091] The nickel content of the conductive layer (100 wt%) is preferably 30 wt% or more, more preferably 35 wt% or more, and even more preferably 40 wt% or more, and is preferably 90 wt% or less, more preferably 85 wt% or less, and even more preferably 80 wt% or less. When the nickel content is equal to or greater than the lower limit, the connection resistance between electrodes can be further reduced. When the nickel content is equal to or less than the upper limit, when electrodes are connected using conductive particles, the conductive particles can be strongly pressed into the electrodes, thereby further reducing the connection resistance between the electrodes.

[0092] The conductive layer may contain an element other than nickel. Examples of the element other than nickel include phosphorus, boron, tungsten, molybdenum, tin, and copper. The element other than nickel may be used alone or in combination of two or more. From the viewpoint of further reducing the connection resistance, the conductive layer preferably contains phosphorus, boron, tungsten, or tin in addition to nickel, more preferably phosphorus, boron, or tungsten, and even more preferably boron. From the viewpoint of further reducing the connection resistance between electrodes, the conductive layer preferably contains phosphorus in addition to nickel. From the viewpoint of increasing the compressive modulus (K value) of the obtained conductive particles and further reducing the connection resistance between electrodes, the conductive layer preferably contains tungsten or tin in addition to nickel. When the conductive layer contains multiple metals, the multiple metals may be alloyed.

[0093] The content of the elements other than nickel in the conductive layer (100 wt %) is preferably 0.1 wt % or more, more preferably 1.0 wt % or more, and is preferably 10 wt % or less, more preferably 5.0 wt % or less. When the content of the elements other than nickel is equal to or more than the lower limit and equal to or less than the upper limit, the conductive layer can have an appropriate hardness, and the connection resistance between electrodes can be further reduced.

[0094] As shown in FIG. 4, which is an enlarged view of a portion of the conductive particle shown in FIG. 1, the region (R1) is the region between the inner surface of the conductive layer 3 and the dashed line L1. The region (R1) is a region of 1 / 2 thickness in the thickness direction on the base particle 2 side of the conductive layer 3. The region (R1) is a region of 1 / 2 thickness from the inner surface of the conductive layer 3 toward the outside. The region (R2) is a region between the outer surface of the conductive layer 3 and the dashed line L1. The region (R2) is a region of 1 / 2 thickness in the thickness direction on the outer surface side of the conductive layer 3. The region (R2) is a region of 1 / 2 thickness from the outer surface of the conductive layer 3 toward the inside.

[0095] In the conductive particles, it is preferable that the nickel content has a gradient in the thickness direction of the conductive layer. In the conductive particles, it is preferable that nickel is unevenly distributed so that it is more abundant on the outer surface side of the conductive layer than on the inner surface side (substrate particle side) of the conductive layer. In the conductive particles, it is preferable that the average nickel content in the region (R1) at 1 / 2 the thickness from the inner surface of the conductive layer toward the outside is less than the average nickel content in the region (R2) at 1 / 2 the thickness from the outer surface of the conductive layer toward the inside. When the above preferred aspects are satisfied, it is possible to more easily control the fluctuations in the correlation line that indicate brittle fracture of the conductive layer, and the effects of the present invention can be more effectively achieved. In this specification, the "average content" means the average content on a weight percent basis.

[0096] The average nickel content in the region R1 is preferably 75 wt% or more, more preferably 80 wt% or more, even more preferably 85 wt% or more, particularly preferably 90 wt% or more, and is preferably 100 wt% or less, more preferably 99.5 wt% or less, even more preferably 99 wt% or less, particularly preferably 98.5 wt% or less. When the average nickel content in the region R1 is equal to or greater than the lower limit and equal to or less than the upper limit, fluctuations in the correlation line that indicate brittle fracture of the conductive layer can be more easily controlled, and the effects of the present invention can be more effectively exhibited.

[0097] The average nickel content in the region R2 is preferably 90% by weight or more, more preferably 95% by weight or more, even more preferably 96% by weight or more, particularly preferably 97% by weight or more, and is preferably 100% by weight or less, more preferably 99.9% by weight or less, even more preferably 99.5% by weight or less, particularly preferably 99% by weight or less. When the average nickel content in the region R2 is equal to or greater than the lower limit and equal to or less than the upper limit, fluctuations in the correlation line that indicate brittle fracture of the conductive layer can be more easily controlled, and the effects of the present invention can be more effectively exhibited.

[0098] From the viewpoint of more easily controlling the fluctuations indicating brittle fracture of the conductive layer in the correlation line and more effectively demonstrating the effects of the present invention, the average nickel content in the region R1 is preferably at least 0.1 wt % less than the average nickel content in the region R2, and more preferably at least 0.5 wt % less. From the viewpoint of more easily controlling the fluctuations indicating brittle fracture of the conductive layer in the correlation line and more effectively demonstrating the effects of the present invention, the average nickel content in the region R1 is preferably at most 20.0 wt % less than the average nickel content in the region R2, and more preferably at most 18.0 wt % less. From the viewpoint of even more easily controlling the fluctuations indicating brittle fracture of the conductive layer in the correlation line and more effectively demonstrating the effects of the present invention, the average nickel content in the region R1 is more preferably at most 5.0 wt %, and particularly preferably at most 3.0 wt % less. Preferably, the average nickel content in the region R1 is less than the average nickel content in the region R2 by at least the lower limit and not more than the upper limit.

[0099] It is preferable that the content of elements other than the main metal has a gradient in the thickness direction of the conductive layer. It is preferable that the elements other than the main metal are unevenly distributed so that they are present in greater amounts on the inner surface side (substrate particle side) of the conductive layer than on the outer surface side of the conductive layer. It is preferable that the total average content of elements other than the main metal in a region (R1) extending from the inner surface of the conductive layer to half the thickness toward the outside is greater than the total average content of elements other than the main metal in a region (R2) extending from the outer surface of the conductive layer to half the thickness toward the inside. When the above preferred aspects are satisfied, it is possible to more easily control the fluctuation in the correlation line indicating brittle fracture of the conductive layer, and the effects of the present invention can be more effectively exerted.

[0100] From the viewpoint of more easily controlling the fluctuations in the conductive layer that indicate brittle fracture and more effectively achieving the effects of the present invention, it is preferable that the conductive layer contain an element other than the main metal in both the region (R1) that is ½ thickness from the inner surface of the conductive layer toward the outside and the region (R2) that is ½ thickness from the outer surface of the conductive layer toward the inside. From the viewpoint of more easily controlling the fluctuations in the conductive layer that indicate brittle fracture and more effectively achieving the effects of the present invention, it is preferable that the conductive layer contain an element other than nickel in both the region (R1) that is ½ thickness from the inner surface of the conductive layer toward the outside and the region (R2) that is ½ thickness from the outer surface of the conductive layer toward the inside. From the viewpoint of more easily controlling the fluctuations in the conductive layer that indicate brittle fracture and more effectively achieving the effects of the present invention, it is preferable that the main metal and an element other than the main metal are present in both the region R1 and the region R2. From the viewpoint of more easily controlling the fluctuations that indicate brittle fracture of the conductive layer and more effectively exerting the effects of the present invention, it is preferable that nickel and elements other than nickel are present in both the region R1 and the region R2.

[0101] From the viewpoint of more easily controlling the fluctuations that indicate brittle fracture in the conductive layer and more effectively achieving the effects of the present invention, the total average content of elements other than the main metal (preferably elements other than nickel) in region R1 is preferably at least 0.5 wt % higher, and more preferably at least 1.0 wt %, than the total average content of elements other than the main metal (preferably elements other than nickel) in region R2. From the viewpoint of more easily controlling the fluctuations that indicate brittle fracture in the conductive layer and more effectively achieving the effects of the present invention, the average content of elements other than the main metal (preferably elements other than nickel) in region R1 is preferably at most 20.0 wt % higher, and more preferably at most 18.0 wt % higher, than the average content of elements other than the main metal (preferably elements other than nickel) in region R2. The average content of elements other than the main metal (preferably elements other than nickel) in region R1 is preferably less than the average content of elements other than the main metal (preferably elements other than nickel) in region R2 by at least the above-mentioned lower limit and at most the above-mentioned upper limit.

[0102] The difference between the total average content of elements other than the main metal in region R1 and the total average content of elements other than the main metal in region R2 (the total average content of elements other than the main metal in region R1 - the total average content of elements other than the main metal in region R2) is preferably 0.5 wt % or more, more preferably 1.0 wt % or more, even more preferably 1.5 wt % or more, and is preferably 20.0 wt % or less, more preferably 19.0 wt % or less, and even more preferably 18.0 wt % or less. When this difference is equal to or greater than the above lower limit and equal to or less than the above upper limit, the connection resistance between electrodes can be further reduced.

[0103] The ratio of the total average content of elements other than the main metal in region R1 to the total average content of elements other than the main metal in region R2 is preferably 1.0 or more, more preferably 2.0 or more, even more preferably 5.0 or more, and is preferably 50 or less, more preferably 40 or less, and even more preferably 30 or less. When the ratio (total average content of elements other than the main metal in region R1 / total average content of elements other than the main metal in region R2) is equal to or greater than the lower limit and equal to or less than the upper limit, fluctuations in the correlation line that indicate brittle fracture of the conductive layer can be more easily controlled, and the effects of the present invention can be more effectively exhibited.

[0104] The content and average content of each element contained in the conductive layer can be measured using various known analytical methods. Examples of the measurement method include absorption spectrometry and spectral analysis. Examples of the absorption spectrometry include a flame absorption spectrophotometer and an electric heating furnace absorption spectrophotometer. Examples of the spectral analysis include plasma emission spectrometry and plasma ion source mass spectrometry.

[0105] When measuring the content of each element contained in the conductive layer, it is preferable to use an ICP optical emission analyzer. Examples of commercially available ICP optical emission analyzers include the "ICP optical emission analyzer" manufactured by HORIBA.

[0106] When measuring the content and average content of each element in each region in the thickness direction of the conductive layer, it is preferable to use an FE-TEM device. Examples of commercially available FE-TEM devices include "JEM-2010" manufactured by JEOL Ltd.

[0107] From the viewpoint of further reducing the connection resistance between electrodes, the brittle fracture of the conductive layer preferably occurs inside the conductive layer. From the viewpoint of further reducing the connection resistance between electrodes, the brittle fracture of the conductive layer preferably occurs in the region R1. From the viewpoint of further reducing the connection resistance between electrodes, the brittle fracture of the conductive layer preferably occurs in a region extending from the inner surface of the conductive layer to the outside, which is half the thickness of the conductive layer, and more preferably occurs in a region extending from the inner surface of the conductive layer to the outside, which is one-third the thickness of the conductive layer.

[0108] The conductive layer may be formed of a single layer, as in the conductive particles 1 and 21 shown in Figures 1 and 3. The conductive layer may be formed of multiple layers, as in the conductive particle 11 shown in Figure 2. That is, the conductive layer may have a laminated structure of two or more layers.

[0109] The thickness of the conductive layer (thickness of the entire conductive layer) is preferably 0.01 μm or more, more preferably 0.05 μm or more, and preferably 1.0 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less. The thickness of the conductive layer is the thickness of the entire conductive layer when the conductive layer is multilayered. When the thickness of the conductive layer is equal to or greater than the above lower limit and equal to or less than the above upper limit, sufficient conductivity is obtained, and the conductive particles do not become too hard, so that the conductive particles deform sufficiently when connecting electrodes.

[0110] The thickness of the conductive layer can be measured by observing the cross section of the conductive particle using, for example, a transmission electron microscope (TEM).

[0111] The method for forming the conductive layer on the surface of the base particle is not particularly limited. Examples of the method for forming the conductive layer include electroless plating, electroplating, physical vapor deposition, and coating the surface of the base particle with a metal powder or a paste containing a metal powder and a binder. Electroless plating is preferred because it is easy to form the conductive layer. Examples of the physical vapor deposition method include vacuum deposition, ion plating, and ion sputtering.

[0112] [Core Material] From the viewpoint of further reducing the connection resistance and further increasing the conduction reliability, it is preferable that the conductive particles have a plurality of protrusions on the outer surface of the conductive layer. Furthermore, it is preferable that the conductive particles have a plurality of core materials in the conductive layer that raise the outer surface of the conductive layer so as to form the plurality of protrusions. The conductive particles do not necessarily have protrusions on the outer surface of the conductive layer.

[0113] The core material is embedded in the conductive layer, which makes it easy to form a plurality of protrusions on the outer surface of the conductive layer. However, the core material does not necessarily have to be used to form the protrusions on the surface of the conductive particle and the surface of the conductive layer.

[0114] Methods for forming the protrusions include the following: A method in which a core substance is attached to the surface of a base particle, and then a conductive layer is formed by electroless plating. A method in which a conductive layer is formed on the surface of a base particle by electroless plating, and then a core substance is attached, and then a conductive layer is formed by electroless plating. A method in which a core substance is added during the process of forming a conductive layer on the surface of a base particle by electroless plating.

[0115] Examples of the material for the core substance include conductive and non-conductive substances. Examples of the conductive substance include conductive non-metals such as metals, metal oxides, and graphite, and conductive polymers. Examples of the conductive polymer include polyacetylene. Examples of the non-conductive substance include silica, alumina, tungsten carbide, titanium oxide, barium titanate, and zirconia. As the metal for the core substance, any of the metals listed as the materials for the conductive material can be used as appropriate.

[0116] Specific examples of the core material include barium titanate (Mohs hardness 4.5), nickel (Mohs hardness 5), silica (silicon dioxide, Mohs hardness 6-7), titanium oxide (Mohs hardness 7), zirconia (Mohs hardness 8-9), alumina (Mohs hardness 9), tungsten carbide (Mohs hardness 9), and diamond (Mohs hardness 10). The core material is preferably nickel, silica, titanium oxide, zirconia, alumina, tungsten carbide, or diamond, and more preferably silica, titanium oxide, zirconia, alumina, tungsten carbide, or diamond. Furthermore, the core material is more preferably titanium oxide, zirconia, alumina, tungsten carbide, or diamond, and particularly preferably zirconia, alumina, tungsten carbide, or diamond. The Mohs hardness of the core material is preferably 4 or higher, more preferably 6 or higher, even more preferably 7 or higher, and particularly preferably 7.5 or higher. When the Mohs hardness of the material of the core substance is equal to or greater than the lower limit, the 10% K value of the conductive particles can be easily controlled within a suitable range.

[0117] The shape of the core material is not particularly limited. The core material is preferably in the form of a mass. Examples of the core material include a particulate mass, an aggregate mass formed by aggregating a plurality of microparticles, and an amorphous mass.

[0118] The average particle size of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, and preferably 0.4 μm or less, more preferably 0.3 μm or less. When the average particle size of the core material is equal to or more than the lower limit and equal to or less than the upper limit, the connection resistance between electrodes is effectively reduced.

[0119] The average particle size of the core material is preferably a number average particle size, which can be determined by observing 50 random core materials under an electron microscope or an optical microscope and calculating the average value.

[0120] The number of the protrusions per conductive particle is preferably 3 or more, more preferably 5 or more. The upper limit of the number of the protrusions is not particularly limited. The upper limit of the number of the protrusions can be appropriately selected taking into account the particle diameter of the conductive particles, etc.

[0121] From the viewpoint of further reducing the connection resistance and further increasing the conductivity reliability, the surface area of ​​the portion where the protrusions are located is preferably 10% or more, more preferably 30% or more, and preferably 99% or less, more preferably 95% or less, of the total surface area (100%) of the conductive particle.

[0122] The average height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, and is preferably 0.7 μm or less, more preferably 0.6 μm or less. When the average height of the protrusions is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between the electrodes is effectively reduced.

[0123] [Insulating Material] The conductive particles preferably include an insulating material disposed on the surface of the conductive layer. In this case, using the conductive particles to connect electrodes can further prevent short circuits between adjacent electrodes. Specifically, when multiple conductive particles come into contact with each other, an insulating material is present between the multiple electrodes, preventing short circuits not between upper and lower electrodes but between laterally adjacent electrodes. When connecting the electrodes, applying pressure to the conductive particles with two electrodes can easily remove the insulating material between the conductive layer of the conductive particles and the electrode. When the conductive particles have multiple protrusions on the outer surface of the conductive layer, the insulating material can be more easily removed between the conductive layer of the conductive particles and the electrode.

[0124] The insulating material is preferably insulating particles, since this allows the insulating material to be more easily removed when the electrodes are pressed together.

[0125] Specific examples of the insulating resin that is the material for the insulating substance include polyolefins, (meth)acrylate polymers, (meth)acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, thermosetting resins, and water-soluble resins.

[0126] The particle size of the insulating material can be appropriately selected depending on the particle size of the conductive particles and the application of the conductive particles. Furthermore, from the viewpoint of improving insulating performance, insulating materials with different particle sizes may be mixed and used. The particle size of the insulating material is preferably 0.005 μm or more, more preferably 0.01 μm or more, and preferably 1 μm or less, more preferably 0.5 μm or less. If the particle size of the insulating material is above the lower limit, when the conductive particles are dispersed in the binder resin, the conductive layers of multiple conductive particles are less likely to come into contact with each other. If the particle size of the insulating particles is below the upper limit, excessive pressure and high temperature heating are not required to remove the insulating material between the electrodes and the conductive particles when connecting the electrodes.

[0127] (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 the binder resin and used as a conductive material. The conductive material is preferably an anisotropic conductive material. The conductive particles and the conductive material are preferably used for electrical connection between electrodes. The conductive material is preferably a circuit connection material.

[0128] The binder resin is not particularly limited. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent. Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, and elastomers. Only one type of the binder resin may be used, or two or more types may be used in combination.

[0129] Examples of the vinyl resin include vinyl acetate resin, acrylic resin, and styrene resin. Examples of the thermoplastic resin include polyolefin resin, ethylene-vinyl acetate copolymer, and polyamide resin. Examples of the curable resin include epoxy resin, urethane resin, polyimide resin, and unsaturated polyester resin. The curable resin may be a room temperature curable resin, a thermosetting resin, a photocurable resin, or a moisture curable resin. Examples of the thermoplastic block copolymer include a styrene-butadiene-styrene block copolymer, a styrene-isoprene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer, and a hydrogenated styrene-isoprene-styrene block copolymer. Examples of the elastomer include a styrene-butadiene copolymer rubber and an acrylonitrile-styrene block copolymer rubber.

[0130] The conductive material and the binder resin preferably contain a thermoplastic component or a thermosetting component. The conductive material and the binder resin may contain a thermoplastic component or a thermosetting component. The conductive material and the binder resin preferably contain a thermosetting component. The thermosetting component preferably contains a curable compound that can be cured by heating and a thermosetting agent. The thermosetting agent is preferably a thermal cationic curing initiator. The curable compound that can be cured by heating and the thermosetting agent are used in an appropriate blend ratio so that the binder resin cures. If the binder resin contains a thermal cationic curing initiator, acid is likely to be contained in the cured product. However, by using the conductive particles according to the present invention, the connection resistance between electrodes can be maintained low.

[0131] The conductive material may contain various additives such as a filler, an extender, a softener, a plasticizer, a polymerization catalyst, a curing catalyst, a colorant, an antioxidant, a heat stabilizer, a light stabilizer, an ultraviolet absorber, a lubricant, an antistatic agent, and a flame retardant.

[0132] The conductive material can be used as a conductive paste, a conductive film, or the like. When the conductive material is a conductive film, a film not containing conductive particles may be laminated on a conductive film containing conductive particles. The conductive paste is preferably an anisotropic conductive paste. The conductive film is preferably an anisotropic conductive film.

[0133] The content of the binder resin in 100% by weight of the conductive material is preferably 10% by weight or more, more preferably 30% by weight or more, even more preferably 50% by weight or more, particularly preferably 70% by weight or more, and is preferably 99.99% by weight or less, more preferably 99.9% by weight or less. When the content of the binder resin is equal to or more than the lower limit and equal to or less than the upper limit, the conductive particles are efficiently arranged between the electrodes, and the electrical conductivity reliability of the connection target members connected by the conductive material is further improved.

[0134] The content of the conductive particles in 100% by weight of the conductive material is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, and is preferably 80% by weight or less, more preferably 60% by weight or less, even more preferably 40% by weight or less, particularly preferably 20% by weight or less, and most preferably 10% by weight or less. When the content of the conductive particles is equal to or more than the lower limit and equal to or less than the upper limit, the reliability of conduction between electrodes is further improved.

[0135] (Connection Structure) A connection structure can be obtained by connecting members to be connected using the conductive particles or a conductive material containing the conductive particles and a binder resin.

[0136] 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 material of the connection portion contains the conductive particles. In the connection structure, the first and second connection target members are connected by the conductive particles.

[0137] FIG. 5 is a cross-sectional view that schematically shows a connection structure using conductive particles according to the first embodiment of the present invention.

[0138] The connection structure 51 shown in Fig. 5 includes a first connection target member 52, a second connection target member 53, and a connection portion 54 connecting the first and second connection target members 52, 53. The connection portion 54 is formed by curing a conductive material containing conductive particles 1. Note that in Fig. 5, the conductive particles 1 are shown schematically for convenience of illustration. Instead of the conductive particles 1, conductive particles 11, 21, etc. may be used.

[0139] The first connection target member 52 has a plurality of first electrodes 52a on its surface (upper surface). The second connection target member 53 has a plurality of second electrodes 53a on its surface (lower surface). The first electrodes 52a and the second electrodes 53a are electrically connected by one or more conductive particles 1. Therefore, the first and second connection target members 52, 53 are electrically connected by the conductive particles 1.

[0140] The method for manufacturing the connection structure is not particularly limited. One example of the method for manufacturing the connection structure is a method in which the conductive material is placed between the first connection target member and the second connection target member to obtain a laminate, and then the laminate is heated and pressurized. The pressure of the pressurization is 1.0 × 10 per total area of ​​the connection portions of the electrodes. ６ Pa ~ 4.9 x 10 ８ The pressure is about 120°C to 220°C. In the connection structure according to the present invention, the conductive particles described above are used, so that the electrodes can be electrically connected even at a relatively low pressure. The heating temperature is about 120°C to 220°C.

[0141] The total area of ​​the connection portions of the electrodes is not limited to the area of ​​the portions in contact with the conductive particles, but refers to the total area of ​​the opposing portions of the two electrodes when viewed in a plane (when viewed in the stacking direction of the first connection target member, the connection portion, and the second connection target member).

[0142] Specific examples of the connection target components include electronic components such as semiconductor chips, capacitors, and diodes, as well as circuit boards such as printed circuit boards, flexible printed circuit boards, glass epoxy boards, and glass boards. The connection target components are preferably electronic components. The conductive particles are preferably used for electrically connecting electrodes in electronic components.

[0143] At least one of the first connection target member and the second connection target member is preferably a flexible printed circuit board. At least one of the first connection target member and the second connection target member is preferably a semiconductor chip. The first connection target member and the second connection target member are preferably a flexible printed circuit board and a semiconductor chip. The material of the flexible printed circuit board is preferably polyimide or polyester, and in the case of polyester, polyethylene terephthalate (PET) is preferable. The conductive particles and the conductive material are suitably used for conduction of the flexible printed circuit board.

[0144] Examples of the electrode provided on the connection target member include metal electrodes such as gold electrodes, nickel electrodes, tin electrodes, aluminum electrodes, copper electrodes, silver electrodes, titanium electrodes, molybdenum electrodes, and tungsten electrodes. When the connection target member is a flexible printed circuit board, the electrode is preferably a gold electrode, nickel electrode, titanium electrode, tin electrode, or copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, titanium electrode, copper electrode, molybdenum electrode, or tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode formed solely of aluminum, or an electrode in which an aluminum layer is laminated on the surface of a metal oxide layer. Examples of materials 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.

[0145] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0146] The following materials were prepared:

[0147] Base particle A: resin particles (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd.'s "Micropearl SP-203", average particle diameter 3.0 μm) Base particle B: organic-inorganic hybrid particles (average particle diameter 3.0 μm) Base particle C: resin particles (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd.'s "Micropearl SP-205", average particle diameter 5.0 μm) Base particle D: resin particles (divinylbenzene copolymer resin particles, Sekisui Chemical Co., Ltd.'s "Micropearl SP-208", average particle diameter 8.0 μm) Base particle E: organic-inorganic hybrid particles (average particle diameter 3.0 μm)

[0148] Example 1 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5 wt% palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.5 mol / L of sodium hypophosphite, 0.5 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 25°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The addition of the nickel plating solution was stopped when half of it had been added, and the suspension was heated to 70°C. After the temperature increase, the nickel plating solution was again added dropwise to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-phosphorus conductive layer disposed on the surface of the base particle A.

[0149] Example 2 Conductive particles were obtained in the same manner as in Example 1, except that the initial temperature of the plating solution when it was dropped was 15°C.

[0150] (Example 3) Conductive particles were obtained in the same manner as in Example 1, except that a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.92 mol / L of dimethylamine borane, and 0.05 mol / L of polyethylene glycol (#400) was used as the plating solution, and the initial temperature of the plating solution when dropped was 5°C.

[0151] Example 4 Conductive particles were obtained in the same manner as in Example 3, except that the initial temperature of the plating solution when it was dropped was 10°C.

[0152] Example 5 Conductive particles were obtained in the same manner as in Example 3, except that 0.01 mol / L of sodium tungstate was added to the plating solution.

[0153] Example 6 Conductive particles were obtained in the same manner as in Example 3, except that 0.01 mol / L of sodium tungstate was added to the plating solution and the initial temperature of the plating solution when it was dropped was set to 10°C.

[0154] (Example 7) Conductive particles were obtained in the same manner as in Example 1, except that a nickel plating solution (pH 8.0) containing 0.14 mol / L of nickel sulfate, 0.45 mol / L of hydrazine, 0.045 mol / L of sodium stannate trihydrate, 0.225 mol / L of sodium gluconate, and 0.05 mol / L of polyethylene glycol (#400) was used as the plating solution.

[0155] Example 8 Conductive particles were obtained in the same manner as in Example 7, except that the initial temperature of the plating solution when it was dropped was 15°C.

[0156] Example 9 Conductive particles were obtained in the same manner as in Example 7, except that base particles A were replaced with base particles B.

[0157] Example 10 Conductive particles were obtained in the same manner as in Example 8, except that base particles A were replaced with base particles B.

[0158] Example 11 Conductive particles were obtained in the same manner as in Example 5, except that the concentration of the plating solution in Example 5 was doubled.

[0159] Example 12 Conductive particles were obtained in the same manner as in Example 1, except that base particles A were replaced with base particles C.

[0160] Example 13 Conductive particles were obtained in the same manner as in Example 3, except that base particles D were used instead of base particles A.

[0161] Example 14: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5 wt% palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.5 mol / L of sodium hypophosphite, 0.5 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 25°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then heated to 70°C. After the temperature increase, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.92 mol / L of dimethylamine borane, and 0.05 mol / L of polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-phosphorus-boron conductive layer disposed on the surface of the base particle A.

[0162] Example 15: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5 wt% palladium catalyst solution using an ultrasonic disperser, and the solution was then filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L nickel sulfate, 0.92 mol / L dimethylamine borane, and 0.05 mol / L polyethylene glycol (#400) was prepared. While stirring the obtained suspension at 10°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then heated to 70°C. After the temperature was raised, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.5 mol / L of sodium hypophosphite, 0.5 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-boron-phosphorus conductive layer disposed on the surface of the base particle A.

[0163] Example 16: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5 wt% palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.5 mol / L of sodium hypophosphite, 0.5 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 25°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then heated to 70°C. After the temperature increase, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.9 mol / L of sodium hypophosphite, 0.9 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-phosphorus conductive layer disposed on the surface of the base particle A.

[0164] (Example 17) Conductive particles were obtained in the same manner as in Example 16, except that the plating solution after the suspension was heated to 70°C was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 1.25 mol / L of sodium hypophosphite, 1.25 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400).

[0165] Example 18: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L nickel sulfate, 0.5 mol / L sodium hypophosphite, 0.5 mol / L sodium citrate, and 0.05 mol / L polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 25°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then heated to 70°C. After the temperature increase, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.14 mol / L nickel sulfate, 0.45 mol / L hydrazine, 0.022 mol / L sodium stannate trihydrate, 0.11 mol / L sodium gluconate, and 0.05 mol / L polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. Thereafter, the suspension was filtered to take out the particles, which were then washed with water and dried to obtain conductive particles in which a nickel-phosphorus-tin conductive layer was disposed on the surface of the base particle A.

[0166] Example 19: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5 wt% palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1 wt% dimethylamine borane solution to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L nickel sulfate, 0.5 mol / L sodium hypophosphite, 0.5 mol / L sodium citrate, and 0.05 mol / L polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 15°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then heated to 70°C. After the temperature increase, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.14 mol / L nickel sulfate, 0.45 mol / L hydrazine, 0.011 mol / L sodium stannate trihydrate, 0.06 mol / L sodium gluconate, and 0.05 mol / L polyethylene glycol (#400). The plating solution was gradually added dropwise to the suspension to complete the electroless plating. Thereafter, the suspension was filtered to take out the particles, which were then washed with water and dried to obtain conductive particles in which a nickel-phosphorus-tin conductive layer was disposed on the surface of the base particle A.

[0167] Example 20: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L nickel sulfate, 0.5 mol / L sodium hypophosphite, 0.5 mol / L sodium citrate, and 0.05 mol / L polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 25°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. The suspension was then cooled to 15°C. After cooling, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L nickel sulfate, 0.25 mol / L sodium hypophosphite, 0.25 mol / L sodium citrate, and 0.05 mol / L polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-phosphorus conductive layer disposed on the surface of the base particle A.

[0168] Example 21: 10 parts by weight of base particles A were dispersed in 100 parts by weight of an alkaline solution containing 5% by weight of a palladium catalyst solution using an ultrasonic disperser, and then the solution was filtered to extract base particles A. Next, base particles A were added to 100 parts by weight of a 1% by weight solution of dimethylamine borane to activate the surface of base particles A. The solution was then filtered to obtain base particles A with palladium attached. The base particles A with palladium attached were stirred and dispersed in 300 mL of ion-exchanged 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 with a core material attached. The obtained resin particles were added to 500 parts by weight of distilled water and dispersed to obtain a suspension. Next, a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.5 mol / L of sodium hypophosphite, 0.5 mol / L of sodium citrate, and 0.05 mol / L of polyethylene glycol (#400) was prepared. While stirring the resulting suspension at 70°C (plating solution temperature), the nickel plating solution was gradually added dropwise to the suspension to perform electroless nickel plating. Thereafter, the plating solution was changed to a nickel plating solution (pH 8.0) containing 0.23 mol / L of nickel sulfate, 0.92 mol / L of dimethylamine borane, and 0.05 mol / L of polyethylene glycol (#400), and the plating solution was gradually added dropwise to the suspension to complete the electroless plating. The suspension was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a nickel-phosphorus-boron conductive layer disposed on the surface of the base particle A.

[0169] Comparative Example 1 Conductive particles were obtained in the same manner as in Example 1, except that polyethylene glycol (#400) was omitted from the plating solution and the temperature of the plating solution was kept at 70°C from the beginning to the end of the dropping.

[0170] Comparative Example 2 Conductive particles were obtained in the same manner as in Example 3, except that polyethylene glycol (#400) was omitted from the plating solution and the temperature of the plating solution was kept at 70°C from the beginning to the end of the dropping.

[0171] Comparative Example 3 Conductive particles were obtained in the same manner as in Example 7, except that polyethylene glycol (#400) was omitted from the plating solution and the temperature of the plating solution was kept at 70°C from the beginning to the end of the dropping.

[0172] (Comparative Example 4) Conductive particles were obtained in the same manner as in Example 3, except that base particle A was replaced with base particle E, polyethylene glycol (#400) was removed from the plating solution, and the temperature of the plating solution was kept at 70°C from the beginning to the end of dropping.

[0173] (Comparative Example 5) Conductive particles were obtained in the same manner as in Example 1, except that base particle A was replaced with base particle E, polyethylene glycol (#400) was removed from the plating solution, and the temperature of the plating solution was kept at 70°C from the beginning to the end of dropping.

[0174] (Comparative Example 6) Conductive particles were obtained in the same manner as in Example 7, except that base particle A was replaced with base particle E, polyethylene glycol (#400) was removed from the plating solution, and the temperature of the plating solution was kept at 70°C from the beginning to the end of dropping.

[0175] (Evaluation) (1) 10% K value, 20% K value, and 30% K value of base particle, and 10% K value, 20% K value, and 30% K value of conductive particle The 10% K value, 20% K value, and 30% K value of the base particle and the conductive particle were measured using a micro-compression tester (Fisherscope H-100 manufactured by Fischer) by the method described above.

[0176] (2) Average Contents in Regions R1 and R2, Difference (Total Average Contents of Elements Other Than the Main Metal in Region R1 - Total Average Contents of Elements Other Than the Main Metal in Region R2), and Ratio (Total Average Contents of Elements Other Than the Main Metal in Region R1 / Total Average Contents of Elements Other Than the Main Metal in Region R2) Thin film slices of the obtained conductive particles were prepared using a focused ion beam. Using a transmission electron microscope FE-TEM (JEOL Ltd., "JEM-2010FEF"), the contents of nickel, phosphorus, boron, tungsten, and tin in the thickness direction of the conductive layer were measured with an energy dispersive X-ray analyzer (EDS). From these results, the average contents of nickel, phosphorus, boron, tungsten, and tin were determined in a region (R1) extending from the inner surface of the conductive layer to half the thickness outward and in a region (R2) extending from the outer surface of the conductive layer to half the thickness inward. In addition, the difference (total average content of elements other than the main metal in region R1 - total average content of elements other than the main metal in region R2) and the ratio (total average content of elements other than the main metal in region R1 / total average content of elements other than the main metal in region R2) were calculated.

[0177] (3) Compression test for compressing conductive particles Using a microcompression tester (Fisherscope H-100 manufactured by Fischer), a load (reverse load value) was applied to the obtained conductive particles using a cylindrical (diameter 100 μm, made of diamond) smooth indenter end face at 25 ° C., a compression speed of 0.3 mN / sec, and a maximum test load of 20 mN until the conductive particles were compressed and deformed by 50%. From these results, a correlation diagram was obtained showing a correlation line in which the compressive displacement is on the X axis and the compressive load is on the Y axis. Fluctuations indicative of brittle fracture of the conductive layer were observed on the correlation line in the obtained correlation diagram, and the amount of fluctuation in compressive displacement in the fluctuation indicative of brittle fracture of the conductive layer and the ratio (the amount of fluctuation in compressive displacement in the fluctuation indicative of brittle fracture of the conductive layer / twice the value of the thickness of the conductive layer) were determined. Note that in Comparative Examples 1 to 6, no fluctuations indicative of brittle fracture of the conductive layer were observed, but fluctuations indicative of plating cracks in the conductive layer were observed. In Comparative Examples 4 to 6, fluctuations indicative of fracture of the base particle were also observed. For convenience, the amount of change in compressive displacement in the variation indicating plating cracks in the conductive layer was recorded instead of the amount of change in compressive displacement in the variation indicating brittle fracture of the conductive layer in Comparative Examples 1 to 3. Also, for convenience, the sum of the amount of change in compressive displacement in the variation indicating fracture of the base particle and the amount of change in compressive displacement in the variation indicating plating cracks in the conductive layer was recorded instead of the amount of change in compressive displacement in the variation indicating brittle fracture of the conductive layer in Comparative Examples 4 to 6.

[0178] (4) Initial connection resistance A The obtained conductive particles were added to Mitsui Chemicals' "Structbond XN-5A" to a content of 10 wt% and dispersed to prepare an anisotropic conductive paste. A polyimide substrate (flexible printed circuit board) was prepared having a Ti-Al-Ti multilayer electrode pattern with an L / S of 20 μm / 20 μm on its upper surface. A semiconductor chip was also prepared having a gold electrode pattern with an L / S of 20 μm / 20 μm on its lower surface. The anisotropic conductive paste immediately after preparation was applied to the polyimide substrate to a thickness of 30 μm to form an anisotropic conductive paste layer. Next, the semiconductor chip was stacked on the anisotropic conductive paste layer with the electrodes facing each other. Thereafter, a pressure heating head was placed on the upper surface of the semiconductor chip while adjusting the head temperature so that the temperature of the anisotropic conductive paste layer was 150°C. A pressure of 2.5 MPa per total bump area was applied, and the anisotropic conductive paste layer was cured at 150°C to obtain a connection structure. The connection resistance between the opposing electrodes of the resulting connection structure was measured by a four-terminal method. The initial connection resistance A was evaluated according to the following criteria.

[0179] [Evaluation criteria for initial connection resistance A] ○○○: Connection resistance A is 2.0Ω or less ○○: Connection resistance A is greater than 2.0Ω and less than 3.0Ω ○: Connection resistance A is greater than 3.0Ω and less than 5.0Ω △: Connection resistance A is greater than 5.0Ω and less than 10Ω ×: Connection resistance A is greater than 10Ω

[0180] (5) Connection Resistance B (Conductivity Reliability) After Reliability Test The connection structure obtained in the evaluation of initial connection resistance A in (4) above was left for 500 hours in a high-temperature, high-humidity chamber at 85°C and 85% humidity. By leaving the connection structure under these conditions, the connection portion between the electrodes in the connection structure was exposed to the presence of acid for a certain period of time due to a reaction between water that had penetrated into the binder resin and the acid contained in the binder resin. After leaving the connection structure, the connection resistance between the opposing electrodes of the connection structure was measured using a four-terminal method. The connection resistance B (conductivity reliability) after the reliability test was evaluated according to the following criteria.

[0181] [Evaluation criteria for connection resistance B after reliability test] ○○○: Connection resistance B is less than 1.0 times the connection resistance A. ○○: Connection resistance B is 1.0 times or more but less than 1.5 times the connection resistance A. ○: Connection resistance B is 1.5 times or more but less than 2.0 times the connection resistance A. △: Connection resistance B is 2.0 times or more but less than 5.0 times the connection resistance A. ×: Connection resistance B is 5.0 times or more the connection resistance A.

[0182] The compositions of the conductive particles and the results are shown in Tables 1 to 10 below.

[0183]

[0184]

[0185]

[0186]

[0187]

[0188]

[0189]

[0190]

[0191]

[0192]

[0193] In Examples 1 to 21, in a compression test in which the obtained conductive particles were compressed, a correlation line in a correlation diagram in which the compressive displacement is on the X axis and the compressive load is on the Y axis showed a fluctuation indicative of brittle fracture of the conductive layer until a fluctuation indicative of fracture of the base particle was observed and until the conductive particles were compressed by 30%. Note that in Comparative Examples 1 to 6, no fluctuation indicative of brittle fracture of the conductive layer was observed in the correlation line.

[0194] REFERENCE SIGNS LIST 1...Conductive particle 2...Base particle 3...Conductive layer 11...Conductive particle 13...Conductive layer 13A...First conductive layer 13B...Second conductive layer 21...Conductive particle 21a...Protrusion 23...Conductive layer 23a...Protrusion 24...Core material 25...Insulating material 51...Connection structure 52...First connection target member 52a...First electrode 53...Second connection target member 53a...Second electrode 54...Connection portion

Claims

1. A conductive particle comprising a base particle and a conductive layer disposed on a surface of the base particle, wherein, in a compression test in which the conductive particle is compressed, a fluctuation indicative of brittle fracture of the conductive layer is observed before a fluctuation indicative of fracture of the base particle is observed in a correlation line in a correlation diagram in which the compressive displacement is on the X-axis and the compressive load is on the Y-axis.

2. The conductive particle according to claim 1, wherein a fluctuation in the correlation line indicating brittle fracture of the conductive layer is observed up to 30% compression of the conductive particle.

3. A conductive particle as described in claim 1 or 2, wherein in the correlation line, the ratio of the amount of fluctuation in the compressive displacement in the fluctuation indicating brittle fracture of the conductive layer to twice the value of the thickness of the conductive layer is 0.70 or less.

4. A conductive particle according to any one of claims 1 to 3, wherein the conductive layer contains nickel as the main metal, and the average nickel content in a region extending from the inner surface of the conductive layer to half the thickness toward the outside is less than the average nickel content in a region extending from the outer surface of the conductive layer to half the thickness toward the inside.

5. A conductive particle comprising a base particle and a conductive layer disposed on the surface of the base particle, the conductive layer containing nickel as a main metal, the conductive layer containing elements other than nickel in both a region extending from the inner surface of the conductive layer to half the thickness outward and a region extending from the outer surface of the conductive layer to half the thickness inward, and the average nickel content in the region extending from the inner surface of the conductive layer to half the thickness inward is less than the average nickel content in the region extending from the outer surface of the conductive layer to half the thickness inward.

6. The compressive elastic modulus when the base particle is compressed by 10% is 3000 N / mm ２ More than 20000N / mm ２ The conductive particle according to any one of claims 1 to 5, wherein:

7. The conductive particles according to any one of claims 1 to 6, wherein the particle diameter of the conductive particles is 8.0 μm or less.

8. The conductive particle according to any one of claims 1 to 7, further comprising an insulating material disposed on an outer surface of the conductive layer.

9. The conductive particle according to any one of claims 1 to 8, having protrusions on the outer surface of the conductive layer.

10. A conductive material comprising the conductive particles according to any one of claims 1 to 9 and a binder resin.

11. A connection structure comprising: a first connection target member having a first electrode on its surface; a second connection target member having a second electrode on its surface; and a connection portion connecting the first connection target member and the second connection target member, wherein the material of the connection portion contains the conductive particles described in any one of claims 1 to 9, and the first electrode and the second electrode are electrically connected by the conductive particles.

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