Conductive particles, conductive materials and connection structures

Abstract

Provided are electrically conductive particles that, when used for electrical connection between electrodes, make it possible to bring the electrodes into sufficient contact with the electrically conductive particles, and to enhance conduction reliability.　The electrically conductive particles according to the present invention comprise base material particles and electrically conductive portions that are disposed on the surfaces of the base material particles. The electrically conductive portion has two or more electrically conductive layers. The melting point of at least one of the two or more electrically conductive layers is more than 100°C but not more than 400°C. The ratio of the compressive elastic modulus when the electrically conductive particles are compressed by 5% at 25°C to the compressive elastic modulus when the electrically conductive particles are compressed by 0.5% at 25°C is 0.40 or more.

Description

[Technical Field]

[0001] The present invention relates to a conductive particle having a base particle and a conductive portion 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. [Background technology]

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

[0003] The anisotropic conductive material is used to obtain various connection structures, such as a connection between a flexible printed circuit board and a glass substrate (FOG (Film on Glass)), a connection between a semiconductor chip and a flexible printed circuit board (COF (Chip on Film)), a connection between a semiconductor chip and a glass substrate (COG (Chip on Glass)), and a connection between a flexible printed circuit board and a glass epoxy substrate (FOB (Film on Board)).

[0004] Furthermore, the conductive particles may be composed of a base particle and a conductive layer disposed on the surface of the base particle.

[0005] Patent Document 1 below discloses conductive particles in which a conductive layer is formed on the surface of a core particle. The maximum compressive hardness of the conductive particles is 22,000 N / mm 2 The compressive hardness of the conductive particles is at its highest when the compressibility is less than 5%, and the average compressive hardness of the conductive particles when the compressibility is 20% or more and 50% or less is 5000 N / mm 2 ~18000N / mm 2Furthermore, in the conductive particles, the ratio of the maximum compression hardness to the average compression hardness at a compression ratio of 20% to 50% is 2.0 to 10.0. When the conductive particles are compressed at a load application rate of 0.33 mN / sec, the load value at which the conductive layer breaks is 3.0 mN or more.

[0006] Patent Document 2 listed below discloses a conductive adhesive containing an adhesive composition and conductive particles, in which the compression hardness of the conductive particles when compressed by 20% is 10.0 GPa or more at 25°C and 3.5 GPa or less at 150°C. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2022-008082 [Patent Document 2] Patent Publication No. 2021-178913 Summary of the Invention [Problem to be solved by the invention]

[0008] When a connection structure is produced by electrically connecting electrodes using conductive particles as described in Patent Documents 1 and 2, the electrodes and the conductive particles may not be in sufficient contact with each other, which may result in high connection resistance between the electrodes (lower electrical connection reliability) after a conductivity reliability test under a high-temperature, high-humidity environment.

[0009] An object of the present invention is to provide conductive particles that, when used for electrical connection between electrodes, can ensure sufficient contact between the electrodes and the conductive particles, thereby improving conduction reliability. Another object of the present invention is to provide a conductive material and a connection structure using the conductive particles. [Means for solving the problem]

[0010] The present specification discloses the following conductive particles, conductive materials, and connection structures.

[0011] Item 1. A conductive particle comprising a base particle and a conductive portion disposed on the surface of the base particle, the conductive portion having two or more conductive layers, at least one of the two or more conductive layers having a melting point greater than 100°C and equal to or less than 400°C, and the ratio of the compressive modulus when the conductive particle is compressed 5% at 25°C to the compressive modulus when the conductive particle is compressed 0.5% at 25°C being 0.40 or greater.

[0012] Item 2. The conductive particles according to item 1, wherein the ratio of the compressive modulus when the conductive particles are compressed by 5% at 25°C to the compressive modulus when the conductive particles are compressed by 0.5% at 25°C is 0.40 or more and 0.80 or less.

[0013] Item 3. The conductive particles according to Item 1 or 2, wherein the ratio of the compressive modulus when the conductive particles are compressed by 5% at 100°C to the compressive modulus when the conductive particles are compressed by 0.5% at 100°C is 0.80 or more.

[0014] Item 4. The compressive modulus of the conductive particles when compressed by 0.5% at 25°C is 4000 N / mm 2 More than 8000N / mm 2 4. The conductive particles according to any one of items 1 to 3, which are:

[0015] Item 5. The compressive modulus of the conductive particles when compressed by 0.5% at 100°C is 500 N / mm 2 More than 4000N / mm 2 5. The conductive particles according to any one of items 1 to 4, which are:

[0016] Item 6. The conductive particle according to any one of Items 1 to 5, wherein the melting point of the outermost layer of the conductive portion exceeds 100° C., and the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less.

[0017] Item 7. The conductive particle according to any one of Items 1 to 6, wherein the outermost layer of the conductive portion contains indium.

[0018] Item 8. The conductive particle according to any one of Items 1 to 7, wherein the outermost layer of the conductive portion contains a tin-indium alloy.

[0019] Item 9. The conductive particles according to any one of Items 1 to 8, wherein the particle diameter of the conductive particles is 0.5 μm or more and 50 μm or less.

[0020] Item 10. The conductive particles according to any one of Items 1 to 9, wherein the base particles are resin particles.

[0021] Item 11. The compressive modulus of the base particle when compressed by 5% at 25 ° C. is 5600 N / mm 2 11. The conductive particles according to any one of items 1 to 10, which are:

[0022] Item 12. A conductive material comprising the conductive particles according to any one of items 1 to 11 and a binder resin.

[0023] Item 13. 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 11; and the first electrode and the second electrode are electrically connected by the conductive particles. [Effects of the Invention]

[0024] The conductive particle according to the present invention comprises a base particle and a conductive portion disposed on the surface of the base particle. In the conductive particle according to the present invention, the conductive portion has two or more conductive layers, and at least one of the two or more conductive layers has a melting point of more than 100°C and not more than 400°C. In the conductive particle according to the present invention, the ratio of the compressive modulus when the conductive particle is compressed by 5% at 25°C to the compressive modulus when the conductive particle is compressed by 0.5% at 25°C is 0.40 or more. Because the conductive particle according to the present invention has the above configuration, when used for electrical connection between electrodes, the electrodes and the conductive particle can be in sufficient contact with each other, thereby improving conductivity reliability. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a conductive particle according to a third embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view that schematically shows a connection structure using the conductive particles shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

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

[0027] (Conductive particles) The conductive particle according to the present invention comprises a base particle and a conductive portion disposed on the surface of the base particle. In the conductive particle according to the present invention, the conductive portion has two or more conductive layers, and at least one of the two or more conductive layers has a melting point of more than 100°C and not more than 400°C. In the conductive particle according to the present invention, the ratio of the compressive modulus when the conductive particle is compressed by 5% at 25°C to the compressive modulus when the conductive particle is compressed by 0.5% at 25°C is 0.40 or more.

[0028] When conventional conductive particles are used for electrical connection between electrodes, the electrodes and the conductive particles may not be in sufficient contact. Specifically, when conventional conductive particles are used for electrical connection between electrodes, the conductive particles are hard and cannot be deformed sufficiently, resulting in an insufficient contact area between the electrodes and the conductive particles. In this case, the resulting connection structure may have high connection resistance (low conduction reliability) after a conduction reliability test under a high-temperature, high-humidity environment. Furthermore, the resulting connection structure may have high initial connection resistance between the electrodes.

[0029] The conductive particles according to the present invention have the above-mentioned structure, and therefore when used for electrical connection between electrodes, the electrodes and the conductive particles can be in sufficient contact with each other, thereby improving the reliability of electrical conduction. Furthermore, the conductive particles according to the present invention have the above-mentioned structure, and therefore the initial connection resistance between the electrodes of the resulting connection structure can be reduced.

[0030] Specifically, in the conductive particles according to the present invention, at least one of the two or more conductive layers has a melting point exceeding 100°C and not exceeding 400°C. This allows for good compatibility between the metal components at the contact area between the electrode and the conductive particle (particularly, the conductive portion) when the electrode and the conductive particle are heated during mounting. Furthermore, in the conductive particles according to the present invention, the ratio of the compressive modulus when the conductive particle is compressed 5% at 25°C to the compressive modulus when the conductive particle is compressed 0.5% at 25°C is 0.40 or greater. This allows for a strong connection between the electrode and the conductive particle (particularly, the conductive portion), and the conductive particle deforms appropriately to ensure a sufficient contact area between the electrode and the conductive particle. As a result, the resulting connection structure can have improved electrical connection reliability.

[0031] Furthermore, when conventional conductive particles are used for electrical connection between electrodes, even if the initial connection resistance between the electrodes of the resulting connection structure is low, the connection resistance may become high (the conduction reliability may become low) after a conduction reliability test under a high-temperature, high-humidity environment. A low initial connection resistance does not necessarily mean that the connection resistance after a conduction reliability test under a high-temperature, high-humidity environment will also be low.

[0032] The conductive particles of the present invention have the above-mentioned configuration, and therefore when used for electrical connection between electrodes, can reduce the initial connection resistance, and can also reduce the connection resistance after a conductivity reliability test under a high-temperature, high-humidity environment.

[0033] In this specification, the ratio of the compressive modulus when the conductive particles are compressed 5% at 25°C (the 5% K value of the conductive particles at 25°C) to the compressive modulus when the conductive particles are compressed 0.5% at 25°C (the 0.5% K value of the conductive particles at 25°C) is referred to as the "ratio (5% K value of the conductive particles at 25°C / 0.5% K value of the conductive particles at 25°C)." Furthermore, the ratio of the compressive modulus when the conductive particles are compressed 5% at 100°C (the 5% K value of the conductive particles at 100°C) to the compressive modulus when the conductive particles are compressed 0.5% at 100°C (the 0.5% K value of the conductive particles at 100°C) is referred to as the "ratio (5% K value of the conductive particles at 100°C / 0.5% K value of the conductive particles at 100°C)."

[0034] In the conductive particles, the ratio of the compressive modulus when the conductive particles are compressed 5% at 25°C to the compressive modulus when the conductive particles are compressed 0.5% at 25°C (5% K value of the conductive particles at 25°C / 0.5% K value of the conductive particles at 25°C) is 0.40 or higher. This ratio (5% K value of the conductive particles at 25°C / 0.5% K value of the conductive particles at 25°C) is preferably 0.45 or higher, more preferably 0.50 or higher, even more preferably 0.55 or higher, particularly preferably 0.60 or higher, and most preferably 0.65 or higher. This ratio (5% K value of the conductive particles at 25°C / 0.5% K value of the conductive particles at 25°C) is preferably 1.00 or lower, more preferably 0.90 or lower, and even more preferably 0.80 or lower. When the ratio (5% K value of conductive particles at 25°C / 0.5% K value of conductive particles at 25°C) is equal to or greater than the lower limit, the conductive particles deform appropriately, ensuring a sufficient contact area between the electrode and the conductive particles, thereby further improving the electrical conductivity reliability. When the ratio (5% K value of conductive particles at 25°C / 0.5% K value of conductive particles at 25°C) is equal to or less than the upper limit, the hardness of the conductive particles (particularly the conductive portion) becomes appropriate, allowing for a strong connection between the electrode and the conductive particles, thereby further improving the electrical conductivity reliability. The ratio (5% K value of conductive particles at 25°C / 0.5% K value of conductive particles at 25°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0035] The compressive elastic modulus of the conductive particles when compressed by 0.5% at 25°C (0.5% K value of the conductive particles at 25°C) is preferably 2000 N / mm 2 More preferably, 3000N / mm 2 More preferably, 4000N / mm 2 More than 4250N / mm 2 More than 4500N / mm 2 The compressive elastic modulus of the conductive particles when compressed by 0.5% at 25°C (0.5% K value of the conductive particles at 25°C) is preferably 20,000 N / mm 2 Less than or equal to 15,000 N / mm 2or less, more preferably 10,000 N / mm 2 Below 8000N / mm 2 Below 7000N / mm, most preferably 2 or less. When the 0.5% K value of the conductive particles at 25°C is equal to or greater than the lower limit, the hardness of the conductive particles (particularly the conductive portion) becomes appropriate, and the electrode and the conductive particles can be firmly connected, thereby further improving the conduction reliability. When the 0.5% K value of the conductive particles at 25°C is equal to or less than the upper limit, when pressure is applied to the electrode and the conductive particles during mounting, the electrode and the conductive particles can maintain contact without being broken. The compressive modulus when the conductive particles are compressed by 0.5% at 25°C (0.5% K value of the conductive particles at 25°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0036] The compressive elastic modulus when the conductive particles are compressed by 5% at 25°C (5% K value of the conductive particles at 25°C) is preferably 1000 N / mm 2 More preferably, 1500N / mm 2 More preferably, 2000N / mm 2 More preferably, 2250 N / mm 2 The compressive elastic modulus when the conductive particles are compressed by 5% at 25°C (5% K value of the conductive particles at 25°C) is preferably 15,000 N / mm 2 Less than or equal to 12500N / mm 2 or less, more preferably 8500N / mm 2 Below 6500N / mm 2or less. If the 5% K value of the conductive particles at 25°C is equal to or greater than the lower limit, when pressure is applied to the electrode and conductive particles during mounting, the conductive particles can contact the electrode without being excessively crushed, thereby further improving the conductivity reliability. If the 5% K value of the conductive particles at 25°C is equal to or less than the upper limit, the conductive particles can deform appropriately and a sufficient contact area between the electrode and the conductive particles can be secured, thereby further improving the conductivity reliability. The compressive modulus when the conductive particles are compressed by 5% at 25°C (the 5% K value of the conductive particles at 25°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0037] The ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is preferably 0.50 or more, more preferably 0.60 or more, even more preferably 0.70 or more, particularly preferably 0.75 or more, and most preferably 0.80 or more. The ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is preferably 1.20 or less, more preferably 1.10 or less, and even more preferably 1.00 or less. When the ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is equal to or greater than the lower limit, the conductive particles deform appropriately, ensuring a sufficient contact area between the electrode and the conductive particles, thereby further improving the conductivity reliability. When the ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is equal to or less than the upper limit, the hardness of the conductive particles (particularly the conductive portion) becomes appropriate, and the electrode and the conductive particles can be firmly connected, thereby further improving the conduction reliability. The ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0038] The compressive elastic modulus when the conductive particles are compressed by 0.5% at 100°C (0.5% K value of the conductive particles at 100°C) is preferably 500 N / mm2 More preferably, 1000N / mm 2 More preferably, 1500N / mm 2 More than 2000N / mm 2 or more, most preferably 2750N / mm 2 The compressive elastic modulus when the conductive particles are compressed by 0.5% at 100°C (0.5% K value of the conductive particles at 100°C) is preferably 15000 N / mm 2 Less than or equal to 10,000 N / mm 2 or less, more preferably 7000N / mm 2 Below 4000N / mm 2 Below 3750N / mm, most preferably 2 or less. When the 0.5% K value of the conductive particles at 100°C is equal to or greater than the lower limit, the hardness of the conductive particles (particularly the conductive portion) becomes appropriate, and the electrode and the conductive particles can be firmly connected, thereby further improving the conduction reliability. When the 0.5% K value of the conductive particles at 100°C is equal to or less than the upper limit, the electrode and the conductive particles can be maintained in contact without being broken when pressure is applied to the electrode and the conductive particles during mounting. The compressive modulus of elasticity when the conductive particles are compressed by 0.5% at 100°C (0.5% K value of the conductive particles at 100°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0039] The compressive elastic modulus when the conductive particles are compressed by 5% at 100°C (5% K value of the conductive particles at 100°C) is preferably 1000 N / mm 2 More preferably, 1500N / mm 2 More preferably, 2000N / mm 2 More preferably, 2250 N / mm 2 The compressive elastic modulus when the conductive particles are compressed by 5% at 100°C (5% K value of the conductive particles at 100°C) is preferably 15,000 N / mm 2 Less than or equal to 12500N / mm 2 or less, more preferably 8500N / mm 2Below 6500N / mm 2 or less. If the 5% K value of the conductive particles at 100°C is equal to or greater than the lower limit, when pressure is applied to the electrode and conductive particles during mounting, the conductive particles can contact the electrode without being excessively crushed, thereby further improving the conductivity reliability. If the 5% K value of the conductive particles at 100°C is equal to or less than the upper limit, the conductive particles can deform appropriately and a sufficient contact area between the electrode and the conductive particles can be secured, thereby further improving the conductivity reliability. The compressive modulus of the conductive particles when compressed 5% at 100°C (the 5% K value of the conductive particles at 100°C) is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0040] The 0.5% K value and 5% K value of the conductive particles at 25° C. and the 0.5% K value and 5% K value of the conductive particles at 100° C. can be measured as follows.

[0041] Using a micro-compression tester, the conductive particles are compressed with a cylindrical (diameter 50 μm, made of diamond) smooth indenter end face at 25°C or 100°C under conditions of applying 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 measurements, the compressive elastic modulus can be calculated using the following formula. Examples of the micro-compression tester that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

[0042] K value (N / mm 2 )=(3 / 2 1 / 2 )·F·S -3 / 2 ·R -1 / 2 F: Load value (N) when the conductive particles are compressed by 0.5% or 5% S: Compression displacement (mm) when the conductive particles are compressed by 0.5% or 5% R: Radius of conductive particle (mm)

[0043] Methods for controlling the 0.5% K value and 5% K value of the conductive particles at 25°C and 100°C, the ratio (5% K value of the conductive particles at 25°C / 0.5% K value of the conductive particles at 25°C), and the ratio (5% K value of the conductive particles at 100°C / 0.5% K value of the conductive particles at 100°C) within preferred ranges include the following methods: A method of adjusting the type of monomer, molecular weight of the monomer, type of crosslinking agent, polymerization temperature, polymerization time, etc. of the material of the base particle; A method of adjusting the type of metal, type of alloy, thickness, etc. of the conductive part; A method of adjusting the arrangement of a conductive layer in the conductive part, which has a melting point of more than 100°C and not more than 400°C.

[0044] From the viewpoint of further improving the effects of the present invention, the compression recovery rate of the conductive particles at 25°C is preferably 20% or more, more preferably 25% or more, even more preferably 30% or more, and is preferably 95% or less, more preferably 90% or less, even more preferably 85% or less.

[0045] The compression recovery rate can be measured as follows.

[0046] Conductive particles are scattered on a sample stage. A microcompression tester is used to apply a load (reversed load value) to each scattered conductive particle at 25°C toward the center of the conductive particle with the smooth end face of a cylindrical indenter (100 μm diameter, made of diamond) until the conductive particle is compressed and deformed by 40%. 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. Examples of the microcompression tester that can be used include the Fischerscope H-100 manufactured by Fischer and the ENT-5 manufactured by Elionix.

[0047] Compression recovery rate (%) = [L2 / L1] x 100 L1: Compression displacement from the load value for the origin to the reverse load value when applying a load L2: Unloading displacement from the reverse load value when releasing the load to the load value for the origin

[0048] The particle diameter of the conductive particles is preferably 0.5 μm or more, more preferably 1.0 μm or more, even more preferably 10 μm or more, and preferably 300 μm or less, more preferably 100 μm or less, even more preferably 50 μm or less, and particularly preferably 30 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 electrodes and the conductive particles can be in more effective contact with each other, and agglomerated conductive particles are less likely to be formed when forming a conductive part. Furthermore, the gap between the electrodes connected via the conductive particles is not too large, and the conductive part is less likely to peel off from the surface of the base particle. Furthermore, 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.

[0049] 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.

[0050] The present invention will be specifically described below with reference to the drawings.

[0051] FIG. 1 is a cross-sectional view schematically showing a conductive particle according to a first embodiment of the present invention.

[0052] The conductive particle 1 shown in Fig. 1 has a base particle 2 and a conductive portion 3 disposed on the surface of the base particle 2. The conductive portion 3 coats 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 portion 3.

[0053] In the conductive particle 1, the conductive portion 3 has two conductive layers. The conductive portion 3 is a conductive layer having a two-layer structure. The conductive portion 3 has a first conductive layer 3A and a second conductive layer 3B. Specifically, the conductive portion 3 has the first conductive layer 3A and the second conductive layer 3B in this order from the inner surface to the outer surface of the conductive portion 3. The first conductive layer 3A is disposed on the surface of the base particle 2. The first conductive layer 3A is in contact with the base particle 2. The first conductive layer 3A is disposed between the base particle 2 and the second conductive layer 3B. The second conductive layer 3B is disposed on the surface of the first conductive layer 3A. The second conductive layer 3B is in contact with the first conductive layer 3A. The second conductive layer 3B is the outermost layer of the conductive portion 3. The second conductive layer 3B is the outermost conductive layer of the conductive particle 1.

[0054] In the conductive particle 1, the melting point of at least one of the two conductive layers in the conductive portion 3 is greater than 100°C and equal to or less than 400°C. In the conductive particle 1, the melting point of the first conductive layer 3A may be greater than 100°C and equal to or less than 400°C, and the melting point of the second conductive layer 3B may be greater than 100°C and equal to or less than 400°C. In the conductive particle 1, the melting points of the first conductive layer 3A and the second conductive layer 3B may each be greater than 100°C and equal to or less than 400°C.

[0055] FIG. 2 is a cross-sectional view schematically showing a conductive particle according to a second embodiment of the present invention.

[0056] 2 has a base particle 2 and a conductive portion 13 disposed on the surface of the base particle 2. The conductive portion 13 coats the surface of the base particle 2. The conductive particle 11 is a coated particle in which the surface of the base particle 2 is coated with the conductive portion 13.

[0057] In the conductive particle 11, the conductive portion 13 has three conductive layers. In the conductive particle 11, the conductive portion 13 is a conductive layer having a three-layer structure. The conductive portion 13 has a first conductive layer 13A, a second conductive layer 13B, and a third conductive layer 13C. Specifically, the conductive portion 13 has the first conductive layer 13A, the second conductive layer 13B, and the third conductive layer 13C in this order from the inner surface to the outer surface of the conductive portion 13. The first conductive layer 13A is disposed on the surface of the base particle 2. The first conductive layer 13A is in contact with the base particle 2. The first conductive layer 13A is disposed between the base particle 2 and the second conductive layer 13B. The second conductive layer 13B is disposed on the surface of the first conductive layer 13A. The second conductive layer 13B is in contact with the first conductive layer 13A. The second conductive layer 13B is disposed between the first conductive layer 13A and the third conductive layer 13C. The third conductive layer 13C is disposed on the surface of the second conductive layer 13B. The third conductive layer 13C is in contact with the second conductive layer 13B. The third conductive layer 13C is the outermost layer of the conductive portion 13. The third conductive layer 13C is the outermost conductive layer of the conductive particle 11.

[0058] In the conductive particle 11, the melting point of at least one of the three conductive layers in the conductive portion 13 is greater than 100°C and equal to or less than 400°C. In the conductive particle 11, the melting point of at least one of the first conductive layer 13A, the second conductive layer 13B, and the third conductive layer 13C is greater than 100°C and equal to or less than 400°C. In the conductive particle 11, the melting point of the first conductive layer 13A may be greater than 100°C and equal to or less than 400°C, the melting point of the second conductive layer 13B may be greater than 100°C and equal to or less than 400°C, and the melting point of the third conductive layer 13C may be greater than 100°C and equal to or less than 400°C. In the conductive particle 11, the melting point of the first conductive layer 13A and the melting point of the second conductive layer 13B may each be greater than 100°C and less than 400°C, and the melting point of the first conductive layer 13A and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C. In the conductive particle 11, the melting point of the second conductive layer 13B and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C. In the conductive particle 11, the melting point of the first conductive layer 13A, the melting point of the second conductive layer 13B, and the melting point of the third conductive layer 13C may each be greater than 100°C and less than 400°C.

[0059] FIG. 3 is a cross-sectional view schematically showing a conductive particle according to a third embodiment of the present invention.

[0060] 3 includes a base particle 2, conductive portions 23 disposed on the surface of the base particle 2, and a plurality of core materials 24. The conductive portions 23 coat the surface of the base particle 2. The conductive particle 21 is a coated particle in which the surface of the base particle 2 is coated with the conductive portions 23.

[0061] In the conductive particle 21, the conductive portion 23 has two conductive layers. The conductive portion 23 is a conductive layer having a two-layer structure. The conductive portion 23 has a first conductive layer 23A and a second conductive layer 23B. Specifically, the conductive portion 23 has the first conductive layer 23A and the second conductive layer 23B in this order from the inner surface to the outer surface of the conductive portion 23. The first conductive layer 23A is disposed on the surface of the base particle 2. The first conductive layer 23A is in contact with the base particle 2. The first conductive layer 23A is disposed between the base particle 2 and the second conductive layer 23B. The second conductive layer 23B is disposed on the surface of the first conductive layer 23A. The second conductive layer 23B is in contact with the first conductive layer 23A. The second conductive layer 23B is the outermost layer of the conductive portion 23. The second conductive layer 23B is the outermost conductive layer of the conductive particle 21.

[0062] The conductive particles 21 have a plurality of protrusions 21a on their surfaces. The conductive portions 23 have a plurality of protrusions 23a on their outer surfaces. The first conductive layer 23A has a plurality of protrusions 23Aa on its outer surface. The second conductive layer 23B has a plurality of protrusions 23Ba on its outer surface.

[0063] In the conductive particle 21, the melting point of at least one of the two conductive layers in the conductive portion 23 is greater than 100°C and equal to or less than 400°C. In the conductive particle 21, the melting point of the first conductive layer 23A may be greater than 100°C and equal to or less than 400°C, and the melting point of the second conductive layer 23B may be greater than 100°C and equal to or less than 400°C. In the conductive particle 21, the melting points of the first conductive layer 23A and the second conductive layer 23B may each be greater than 100°C and equal to or less than 400°C.

[0064] 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".

[0065] [Base material 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. In order to achieve even better effects of the present invention, the base particles are preferably resin particles, inorganic particles excluding metal particles, or organic-inorganic hybrid particles, more preferably resin particles or organic-inorganic hybrid particles, and even more preferably resin particles.

[0066] The base particles are preferably resin particles formed from a resin. When electrically connecting electrodes using the conductive particles, the conductive particles are placed on a first connection target member having a first electrode on its surface, and then a second connection target member having a second electrode on its surface is stacked on the surface of the conductive particles opposite the first electrode, thereby compressing the conductive particles. When the base particles are resin particles, the conductive particles are easily deformed during stacking, allowing for more effective contact between the electrodes and the conductive particles. This can further reduce the initial connection resistance between the electrodes and further reduce the connection resistance after a continuity test under a high-temperature, high-humidity environment (further increasing continuity reliability).

[0067] As the resin material of the resin particles, various organic substances are suitably used. Examples of the resin material of the resin particles include polyolefin resins such as polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyvinylidene chloride, polyisobutylene, and polybutadiene; acrylic resins such as polymethyl (meth)acrylate and polyisobornyl (meth)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, polyether ether ketone, polyethersulfone, and polymers obtained by polymerizing one or more of various polymerizable monomers having an ethylenically unsaturated group. 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.

[0068] 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.

[0069] 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 (meth)acrylate. alkyl (meth)acrylate compounds such as 2-hydroxyethyl (meth)acrylate, glycerol (meth)acrylate, polyoxyethylene (meth)acrylate, glycidyl (meth)acrylate, and other oxygen atom-containing (meth)acrylate compounds; 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.

[0070] 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)propane ... Examples of suitable (meth)acrylates include polyfunctional (meth)acrylate compounds such as pyrene 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.

[0071] From the viewpoint of further effectively exerting the effects of the present invention, the material of the resin particles preferably contains divinylbenzene or a compound having a (meth)acryloyl group. The material of the resin particles may contain divinylbenzene or a compound having a (meth)acryloyl group.

[0072] When resin particles are obtained using the crosslinkable monomer, a crosslinking agent can be used. Examples of the crosslinking agent include (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, and 1,4-butanediol di(meth)acrylate. The crosslinking agent may be used alone or in combination of two or more.

[0073] From the viewpoint of more effectively exerting the effects of the present invention, the crosslinking agent is preferably (poly)propylene glycol di(meth)acrylate, (poly)tetramethylene glycol di(meth)acrylate, or 1,4-butanediol di(meth)acrylate.

[0074] 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.

[0075] 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, but examples 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.

[0076] 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.

[0077] The compressive modulus of the base particle when compressed by 0.5% at 25°C (0.5% K value of the base particle at 25°C) is preferably 500 N / mm 2 More preferably, 800N / mm 2 More preferably, 1000N / mm 2 More than 2000N / mm 2 The compressive modulus of elasticity when the base particle is compressed by 0.5% at 25°C (0.5% K value of the base particle at 25°C) is preferably 15,000 N / mm 2 Less than or equal to 10,000 N / mm 2 or less, more preferably 7500N / mm 2 Below 6000N / mm 2or less. If the 0.5% K value at 25°C of the base particle is not less than the above lower limit, when electrodes are connected using the resulting conductive particles, the electrodes and conductive particles can be in more effective contact, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved. If the 0.5% K value at 25°C of the base particle is not more than the above upper limit, when electrodes are connected using the resulting conductive particles, the electrodes and conductive particles can maintain contact without being destroyed. The 0.5% K value at 25°C of the base particle is preferably not less than the above lower limit and not more than the above upper limit, and the range can be set by appropriately selecting the above lower limit and upper limit.

[0078] The compressive modulus of the base particle when compressed by 5% at 25°C (5% K value of the base particle at 25°C) is preferably 550 N / mm 2 More preferably, 850N / mm 2 More preferably, 1100N / mm 2 More than 2200N / mm 2 The compressive elastic modulus when the base particle is compressed by 5% at 25°C (5% K value of the base particle at 25°C) is preferably 14000 N / mm 2 Less than or equal to 9500N / mm 2 or less, more preferably 7300N / mm 2 Below 5600N / mm 2 Below 4750N / mm, most preferably 2or less. When the 5% K value at 25°C of the base particle is equal to or greater than the lower limit, the hardness of the resulting conductive particles can be improved, and when electrodes are connected using the conductive particles, the electrodes and the conductive particles can be in more effective contact, thereby further reducing the initial connection resistance. When the 5% K value at 25°C of the base particle is equal to or less than the upper limit, when electrodes are connected using the resulting conductive particles, the contact area between the conductive particles and the electrodes is increased, thereby further reducing the initial connection resistance between the electrodes and further improving the conduction reliability. The 5% K value at 25°C of the base particle is preferably equal to or greater than the lower limit and equal to or less than the upper limit, and the range can be set by appropriately selecting the lower limit and the upper limit.

[0079] The particle diameter of the base particle is preferably 0.1 μm or more, more preferably 1 μm or more, even more preferably 1.5 μm or more, even more preferably 2 μm or more, particularly preferably 2.5 μm or more, and most preferably 3.5 μm or more, and is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 50 μm or less, particularly preferably 30 μm or less, and most preferably 20 μm or less. When the particle diameter of the base particle is above the lower limit, when electrodes are connected using the obtained conductive particles, the electrodes and the conductive particles can be in more effective contact, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved. Furthermore, when a conductive portion 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, the connection resistance between the electrodes is further reduced, and the gap between the electrodes is further reduced.

[0080] 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 of the conductive particles, it can be measured, for example, as follows.

[0081] The conductive particles were added to Kulzer's Technovit 4000 to a content of 30% by weight 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.

[0082] [Conductive part] The conductive portion has two or more conductive layers. The conductive portion has a laminated structure of two or more layers. The conductive portion is formed of a plurality of layers. The conductive portion may have two conductive layers, three conductive layers, three or more conductive layers, or four or more conductive layers. There is no particular upper limit on the number of conductive layers in the conductive portion. The conductive portion may have 10 or less conductive layers, or five or less conductive layers.

[0083] In the conductive particle, at least one of the two or more conductive layers (conductive portion) has a melting point of more than 100°C and not more than 400°C. That is, in the conductive particle, at least one of the two or more conductive layers (conductive portion) has a melting point of more than 100°C and not more than 400°C. In the conductive particle, it is preferable that the melting point of the metal component constituting at least one of the two or more conductive layers (conductive portion) is more than 100°C and not more than 400°C. In this specification, a conductive layer having a melting point of more than 100°C and not more than 400°C is referred to as a "conductive layer (X)." In the conductive particle, the conductive layer (X) may be a single layer, two or more layers, three or more layers, or five or less layers.

[0084] A layer other than the outermost layer of the conductive part may be the conductive layer (X), or the outermost layer of the conductive part may be the conductive layer (X). When the conductive part has two conductive layers, having a first conductive layer and a second conductive layer in this order from the inner surface to the outer surface of the conductive part, the first conductive layer may be the conductive layer (X), and the second conductive layer may be the conductive layer (X). When the conductive part has three conductive layers, having a first conductive layer, a second conductive layer, and a third conductive layer in this order from the inner surface to the outer surface of the conductive part, the first conductive layer may be the conductive layer (X), the second conductive layer may be the conductive layer (X), and the third conductive layer may be the conductive layer (X).

[0085] "Metal components constituting the conductive layer" (metal components constituting the layer) means all the metals contained in the conductive layer (layer). The melting point of the metal components constituting the conductive layer (X) is the melting point of all the metals contained in the conductive layer (X). When the conductive layer (X) contains only one type of metal, the melting point of the conductive layer (X) is the melting point of only one type of metal. When the conductive layer (X) contains two or more types of metals, the melting point of the conductive layer (X) is the melting point of all the two or more metals. When the conductive layer (X) contains two or more types of metals and the two or more metals are contained in the conductive layer (X) as an alloy, the melting point of the conductive layer (X) is the melting point of the alloy of the two or more metals.

[0086] The melting point of the conductive layer (X) is preferably 105° C. or higher, more preferably 110° C. or higher, and preferably 350° C. or lower, more preferably 300° C. or lower, even more preferably 250° C. or lower, even more preferably 200° C. or lower, still more preferably 150° C. or lower, particularly preferably 140° C. or lower, and most preferably 130° C. or lower. When the melting point of the conductive layer (X) is not lower than the above lower limit and not higher than the above upper limit, the effects of the present invention can be more effectively exhibited.

[0087] The innermost layer of the conductive part may be a conductive layer (X). The outermost layer of the conductive part may be a conductive layer (X). The intermediate layer of the conductive part may be a conductive layer (X).

[0088] The conductive layer (X) is preferably a layer other than the innermost layer of the conductive part, and is preferably not in contact with the base particle. The conductive layer (X) is particularly preferably the outermost layer of the conductive part, and the outermost layer of the conductive part is particularly preferably the conductive layer (X). In these cases, immediately after the conductive particles come into contact with the electrode, the conductive particles deform and conform well to the electrode surface, ensuring a sufficient contact area between the electrode and the conductive particles. As a result, the conduction reliability can be further improved.

[0089] The melting point of the outermost layer of the conductive portion (two or more conductive layers) is preferably greater than 100°C, more preferably greater than 105°C, even more preferably greater than 110°C, and preferably less than 400°C, more preferably less than 350°C, even more preferably less than 300°C, even more preferably less than 250°C, even more preferably less than 200°C, even more preferably less than 150°C, particularly preferably less than 140°C, and most preferably less than 130°C. When the melting point of the outermost layer of the conductive portion (two or more conductive layers) is within the above range, the conductive portion deforms sufficiently during mounting, thereby ensuring a sufficient contact area between the electrode and the conductive particles and further improving the conductivity reliability. From the viewpoint of ensuring a sufficient contact area between the electrode and the conductive particles by sufficient deformation during mounting and further improving the conductivity reliability, the melting point of the outermost layer of the conductive portion (two or more conductive layers) of the conductive particles is preferably greater than 100°C, more preferably greater than 100°C and less than 400°C.

[0090] Examples of metals contained in the conductive layer (X) include indium, tin, bismuth, lead, silver, copper, and zinc. The conductive layer (X) preferably contains these metals. The conductive layer (X) may contain only one type of metal, or two or more types of metals. When the conductive layer (X) contains two or more types of metals, the two or more types of metals may be alloyed, or may be contained in the conductive layer (X) as an alloy.

[0091] The metal contained in the conductive layer (X) is preferably indium, tin, or bismuth, more preferably indium. The conductive layer (X) preferably contains indium, tin, or bismuth, more preferably indium. In these cases, immediately after the conductive particles come into contact with the electrode, the conductive particles (particularly the conductive layer (X)) deform and conform well to the electrode surface, ensuring a sufficient contact area between the electrode and the conductive particles. As a result, the conduction reliability can be further improved. When the conductive layer (X) contains indium, the indium may be alloyed with another metal.

[0092] From the viewpoint of ensuring a sufficient contact area between the electrode and the conductive particles by sufficiently deforming the conductive portion during mounting and further enhancing the conduction reliability, the metal contained in the outermost layer of the conductive portion is preferably indium, tin, or bismuth, and more preferably indium. From the viewpoint of ensuring a sufficient contact area between the electrode and the conductive particles by sufficiently deforming the conductive portion during mounting and further enhancing the conduction reliability, the metal contained in the outermost layer of the conductive portion is preferably a tin-bismuth alloy or a tin-indium alloy, and more preferably a tin-indium alloy. From the viewpoint of ensuring a sufficient contact area between the electrode and the conductive particles by sufficiently deforming the conductive portion during mounting and further enhancing the conduction reliability, the metal component constituting ... outermost layer of the conductive portion preferably contains indium, tin, or bismuth, and more preferably contains indium. From the viewpoint of ensuring a sufficient contact area between the electrode and the conductive particles by sufficiently deforming the conductive part during mounting and further improving the reliability of conduction, it is preferable that the outermost layer of the conductive part contains a tin-bismuth alloy or a tin-indium alloy, and it is even more preferable that it contains a tin-indium alloy.

[0093] The conductive part may have a conductive layer other than the conductive layer (X). In this specification, the conductive layer other than the conductive layer (X) is referred to as the "conductive layer (Y)." In the conductive particle, the conductive layer (Y) may be one layer, two or more layers, three or more layers, or five or less layers.

[0094] The melting point of the conductive layer (Y) may be 100°C or lower or may exceed 400°C. The melting point of the metal component constituting the conductive layer (Y) may be 100°C or lower or may exceed 400°C. The conductive part may have, as the conductive layer (Y), a conductive layer composed of a metal component having a melting point of 100°C or lower, or a conductive layer composed of a metal component having a melting point of higher than 400°C. The conductive part may have, as the conductive layer (Y), a conductive layer composed of a metal component having a melting point of 100°C or lower or higher than 400°C. The metal contained in the conductive layer (Y) is not particularly limited. Examples of metals contained in the conductive layer (Y) include gold, silver, palladium, copper, platinum, zinc, iron, lead, ruthenium, aluminum, cobalt, nickel, chromium, titanium, antimony, thallium, germanium, cadmium, silicon, and alloys thereof. The conductive layer (Y) preferably contains these metals. The metal constituting the conductive layer (Y) may be tin-doped indium oxide (ITO) or solder. The metal contained in the conductive layer (Y) may be only one type, or may be two or more types. When the conductive layer (Y) contains two or more types of metals, the two or more types of metals may be alloyed, or may be contained in the conductive layer (Y) as an alloy.

[0095] The conductive part preferably has a conductive layer (X) and a conductive layer (Y) because this provides excellent effects of the present invention. In this case, the melting point of the conductive layer (Y) may be 100° C. or lower, or may exceed 400° C., but the melting point of the conductive layer (Y) preferably exceeds 400° C. because this provides even better effects of the present invention. The conductive part may have only the conductive layer (X), or may not have the conductive layer (Y).

[0096] From the viewpoint of further reducing the initial connection resistance and further increasing the conduction reliability when electrodes are connected using conductive particles, the metal contained in the conductive layer (Y) is preferably nickel, palladium, copper, silver, or gold, and more preferably nickel. From the viewpoint of further reducing the initial connection resistance and further increasing the conduction reliability when electrodes are connected using conductive particles, the conductive layer (Y) preferably contains nickel, palladium, copper, silver, or gold, and more preferably contains nickel.

[0097] The method for forming the conductive portion on the surface of the base particle is not particularly limited. Examples of the method for forming the conductive portion 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. Since the formation of the conductive portion is simple, the method for forming the conductive portion is preferably electroless plating. Examples of the physical vapor deposition method include vacuum deposition, ion plating, and ion sputtering.

[0098] The thickness of the conductive portion (thickness of the entire conductive portion) is preferably 250 nm or more, more preferably 300 nm or more, even more preferably 350 nm or more, even more preferably 400 nm or more, particularly preferably 500 nm or more, and most preferably 600 nm or more, and is preferably 5000 nm or less, more preferably 2000 nm or less, even more preferably 1500 nm or less, and particularly preferably 1000 nm or less. The thickness of the conductive portion is the thickness of the entire conductive portion (total thickness of the conductive layer). When the thickness of the conductive portion is above the above lower limit and below the above upper limit, sufficient conductivity is obtained, and when the obtained conductive particles are used to connect electrodes, the electrodes and the conductive particles can contact more effectively, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved.

[0099] The thickness of the outermost layer of the conductive portion is preferably 100 nm or more, more preferably 200 nm or more, even more preferably 250 nm or more, particularly preferably 300 nm or more, and preferably 3000 nm or less, more preferably 1500 nm or less, even more preferably 1200 nm or less, particularly preferably 1000 nm or less. When the thickness of the outermost layer of the conductive portion is equal to or greater than the above-mentioned lower limit, the hardness of the conductive particles (particularly the conductive portion) at the initial stage of mounting becomes appropriate, and a strong connection with the conductive particles can be achieved, thereby further improving the reliability of conduction. When the thickness of the outermost layer of the conductive portion is equal to or less than the above-mentioned upper limit, the hardness of the conductive particles (particularly the conductive portion) at the initial stage of mounting becomes appropriate, and when pressure is applied to the electrode and the conductive particles during mounting, the electrode and the conductive particles can maintain contact without being broken.

[0100] To obtain even better effects of the present invention, it is preferable that the melting point of the outermost layer of the conductive portion exceeds 100°C and the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less. In this case, the melting point of the outermost layer of the conductive portion may be 400°C or less, or may exceed 400°C. To obtain even better effects of the present invention, it is preferable that the melting point of the outermost layer of the conductive portion is more than 100°C and 400°C or less, and the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less.

[0101] The thickness of the conductive layer (X) is preferably 100 nm or more, more preferably 200 nm or more, even more preferably 250 nm or more, particularly preferably 300 nm or more, and preferably 3000 nm or less, more preferably 1500 nm or less, even more preferably 1200 nm or less, particularly preferably 1000 nm or less. When the thickness of the conductive layer (X) is equal to or greater than the above-mentioned lower limit, the conductive particles deform and conform well to the electrode surface immediately after contact between the conductive particles and the electrode, thereby ensuring a sufficient contact area between the electrode and the conductive particles. As a result, the conduction reliability can be further improved. When the thickness of the conductive layer (X) is equal to or less than the above-mentioned upper limit, softening (deformation) of the conductive particles during mounting can be suppressed to a certain level, thereby ensuring a sufficient contact area between the conductive particles and the electrode. Note that when the conductive layer (X) is two or more layers, the thickness of the conductive layer (X) refers to the total thickness of the two or more conductive layers (X).

[0102] The ratio of the thickness of the conductive layer (X) having a melting point of more than 100°C and not more than 400°C to the thickness of the conductive portion (the thickness of the entire conductive portion) is defined as the ratio (thickness of conductive layer (X) / thickness of conductive portion). The ratio (thickness of conductive layer (X) / thickness of conductive portion) is preferably 0.20 or more, more preferably 0.35 or more, even more preferably 0.40 or more, particularly preferably 0.50 or more, and most preferably 0.60 or more, and is preferably 1.00 or less, more preferably 0.95 or less, even more preferably 0.90 or less, particularly preferably 0.85 or less, and most preferably 0.80 or less. When the ratio (thickness of conductive layer (X) / thickness of conductive portion) is equal to or greater than the lower limit, the conductive layer (X) is sufficiently deformed by heating, ensuring a sufficient contact area between the electrode and the conductive particles, thereby further improving the conduction reliability. When the above ratio (thickness of the conductive layer (X) / thickness of the conductive portion) is equal to or less than the above upper limit, softening (deformation) of the conductive particles during mounting can be suppressed to a certain level, and a sufficient contact area between the conductive particles and the electrode can be ensured.

[0103] The thickness of the conductive portion and each conductive layer (conductive layer (X) and conductive layer (Y)) can be measured by observing the cross section of the conductive particle using, for example, a transmission electron microscope (TEM).

[0104] The conductive layer (X) may contain components other than metal components having a melting point of more than 100°C and not more than 400°C. The content of metal components having a melting point of more than 100°C and not more than 400°C (metal components constituting the conductive layer (X)) in 100% by weight of the conductive layer (X) is preferably 50% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 100% by weight or less (most preferably 100% by weight (total amount)). When the content of the metal components having a melting point of more than 100°C and not more than 400°C is at least the above lower limit, sufficient conductivity is obtained, and when electrodes are connected using the resulting conductive particles, the electrodes and the conductive particles can be in more effective contact, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved.

[0105] The content of metal components having a melting point of more than 100°C and not more than 400°C (metal components constituting the conductive layer (X)) in 100% by weight of the conductive part is preferably 0.4% by weight or more, more preferably 0.65% by weight or more, and preferably 100% by weight or less, more preferably 95.0% by weight or less, and even more preferably 90.0% by weight or less. When the content of metal components having a melting point of more than 100°C and not more than 400°C is not less than the above lower limit and not more than the above upper limit, sufficient conductivity is obtained, and when the obtained conductive particles are used to connect electrodes, the electrodes and the conductive particles can contact more effectively, the initial connection resistance between the electrodes can be further reduced, and the conduction reliability can be further improved.

[0106] The metal content of the conductive portion can be measured using various known analytical methods. Examples of methods for measuring the metal content of the conductive portion include absorption spectrometry and spectral analysis. In the absorption spectrometry, a flame absorption spectrophotometer, an electric heating furnace absorption spectrophotometer, etc. can be used. Examples of the spectral analysis include plasma emission spectrometry and plasma ion source mass spectrometry.

[0107] The metal content of the conductive portion can be measured using, for example, an ICP optical emission spectrometer. Examples of commercially available ICP optical emission spectrometers include the "ICP optical emission spectrometer" manufactured by HORIBA.

[0108] [Core substance] From the viewpoint of further reducing the connection resistance and further increasing the conduction reliability, the conductive particles preferably have a plurality of protrusions on the outer surface of the conductive portion. Furthermore, the conductive particles preferably include a plurality of core materials in the conductive portion that raise the outer surface of the conductive portion so as to form the plurality of protrusions.

[0109] The core material is embedded in the conductive part, which makes it easy to form a plurality of protrusions on the outer surface of the conductive part. However, it is not necessary to use the core material to form the protrusions on the surface of the conductive particle and the surface of the conductive part.

[0110] Methods for forming the above-mentioned protrusions include a method in which a core material is attached to the surface of a base particle and then a conductive portion is formed by electroless plating, a method in which a conductive portion is formed on the surface of a base particle by electroless plating, then a core material is attached, and then a conductive portion is formed by electroless plating, and a method in which a core material is added during the process of forming a conductive portion on the surface of a base particle by electroless plating.

[0111] 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, as well as 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, the metals listed as the metals contained in the conductive layer (X) and the conductive layer (Y) can be used as appropriate.

[0112] 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. The core material is further 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 higher than the lower limit, the compressive elastic modulus of the conductive particles can be easily controlled within a suitable range.

[0113] 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 particulate masses, aggregates formed by aggregating multiple microparticles, and amorphous masses.

[0114] The average particle size of the core material is preferably 0.001 μm or more, more preferably 0.05 μm or more, and preferably 0.9 μm or less, more preferably 0.2 μm or less. When the average particle size of the core material is equal to or greater than the lower limit and equal to or less than the upper limit, the connection resistance between electrodes is effectively reduced.

[0115] 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.

[0116] 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 consideration the particle diameter of the conductive particles, etc.

[0117] From the viewpoint of further reducing the initial connection resistance and further increasing the conductivity reliability when electrodes are connected using conductive particles, the surface area of ​​the portion where the protrusions are located is preferably 10% or more, more preferably 30% or more, and preferably 95% or less, more preferably 90% or less, of the total surface area (100%) of the conductive particles.

[0118] The average height of the plurality of protrusions is preferably 0.001 μm or more, more preferably 0.05 μm or more, and preferably 0.9 μm or less, more preferably 0.5 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 initial connection resistance can be further reduced and the electrical connection reliability can be further improved when used for electrical connection between electrodes.

[0119] [Insulating material] The conductive particles may or may not include an insulating material disposed on the surface of the conductive portion. From the viewpoint of further reducing the initial connection resistance and further increasing the conduction reliability when electrodes are connected using the conductive particles, it is preferable that the conductive particles do not include an insulating material.

[0120] Examples of the insulating material include polyolefins, (meth)acrylate polymers, (meth)acrylate copolymers, block polymers, thermoplastic resins, crosslinked thermoplastic resins, thermosetting resins, and water-soluble resins.

[0121] (Conductive materials) The conductive material according to the present invention includes the conductive particles described above and a binder resin. The conductive particles are preferably dispersed in a binder resin before use. The conductive particles are preferably dispersed in a binder resin before use as a conductive material. The conductive particles are preferably used to obtain an anisotropic conductive material (use of the conductive particles to obtain an anisotropic conductive material). The conductive material is preferably an anisotropic conductive material (use of the conductive material to obtain an anisotropic conductive material). The conductive particles are preferably used for electrical connection between electrodes (use of the conductive particles for electrical connection between electrodes). The conductive material is preferably used for electrical connection between electrodes (use of the conductive material for electrical connection between electrodes). The conductive material is preferably a conductive material for circuit connection (use of the conductive material for circuit connection).

[0122] The binder resin is not particularly limited. A known insulating resin is used as the binder resin. The binder resin preferably contains a thermoplastic component (thermoplastic compound) or a curable component, and more preferably contains a curable component. Examples of the curable component include a photocurable component and a thermosetting component. The photocurable component preferably contains a photocurable compound and a photopolymerization initiator. The thermosetting component preferably contains a thermosetting compound and a thermosetting agent.

[0123] Examples of the binder resin include vinyl resins, thermoplastic resins, curable resins, thermoplastic block copolymers, elastomers, etc. The binder resins may be used alone or in combination of two or more.

[0124] 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. The curable resin may be used in combination with a curing agent. Examples of the thermoplastic block copolymer include styrene-butadiene-styrene block copolymer, styrene-isoprene-styrene block copolymer, a hydrogenated product of styrene-butadiene-styrene block copolymer, and a hydrogenated product of styrene-isoprene-styrene block copolymer. Examples of the elastomer include styrene-butadiene copolymer rubber and acrylonitrile-styrene block copolymer rubber.

[0125] In addition to the conductive particles and the binder resin, the conductive material may contain various additives such as fillers, extenders, softeners, plasticizers, polymerization catalysts, curing catalysts, colorants, antioxidants, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antistatic agents, and flame retardants.

[0126] The method for dispersing the conductive particles in the binder resin can be a conventionally known dispersion method and is not particularly limited. Examples of the method for dispersing the conductive particles in the binder resin include the following methods: A method in which the conductive particles are added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the conductive particles are uniformly dispersed in water or an organic solvent using a homogenizer or the like, then added to the binder resin and then kneaded and dispersed using a planetary mixer or the like; A method in which the binder resin is diluted with water or an organic solvent or the like, then the conductive particles are added, and then kneaded and dispersed using a planetary mixer or the like.

[0127] The viscosity (η25) of the conductive material at 25°C is preferably 30 Pa·s or more, more preferably 50 Pa·s or more, and preferably 400 Pa·s or less, more preferably 300 Pa·s or less. When the viscosity of the conductive material at 25°C is equal to or greater than the lower limit and equal to or less than the upper limit, the insulation reliability between horizontal electrodes can be more effectively improved, and the conduction reliability between vertical electrodes can be more effectively improved. The viscosity (η25) can be adjusted appropriately by changing the types and amounts of the components.

[0128] The viscosity (η25) can be measured, for example, using an E-type viscometer ("TVE22L" manufactured by Toki Sangyo Co., Ltd.) under conditions of 25° C. and 5 rpm.

[0129] 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.

[0130] 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 connection reliability of the connection target members connected by the conductive material can be further improved.

[0131] 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 electrical conductivity reliability and the insulating reliability can be further improved.

[0132] (Connection structure) A connection structure can be obtained by connecting electrodes using the conductive particles or a conductive material containing the conductive particles and a binder resin.

[0133] The connection structure according to the present invention comprises 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. In the connection structure according to the present invention, the material of the connection portion contains the conductive particles described above. In the connection structure according to the present invention, the first electrode and the second electrode are electrically connected by the conductive particles. Because the connection structure according to the present invention has the above configuration, the electrodes and the conductive particles can be in sufficient contact with each other, thereby improving electrical connection reliability.

[0134] FIG. 4 is a cross-sectional view that schematically shows a connection structure using conductive particles according to the first embodiment of the present invention.

[0135] The connection structure 51 shown in FIG. 4 includes a first member to be connected 52, a second member to be connected 53, and a connection portion 54 connecting the first member to be connected 52 and the second member to be connected 53. The material of the connection portion 54 includes conductive particles 1. The connection portion 54 may be formed from a conductive material including the conductive particles 1. The connection portion 54 is preferably formed by hardening a conductive material including a plurality of conductive particles 1. Note that the conductive particles 1 are shown schematically in FIG. 4 for ease of illustration. Instead of the conductive particles 1, conductive particles 11 or conductive particles 21 may be used.

[0136] 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 connection target member 52 and the second connection target member 53 are electrically connected by the conductive portions 3 of the conductive particles 1.

[0137] The method for producing the connection structure is not particularly limited. One example of a method for producing a connection structure is a method in which the conductive material is placed between a first member to be connected and a second member to be connected, a laminate is obtained, and then the laminate is heated and pressurized. The pressure of the thermocompression bonding is preferably 0.1 MPa or more, more preferably 1 MPa or more, even more preferably 40 MPa or more, particularly preferably 60 MPa or more, and preferably 90 MPa or less, more preferably 70 MPa or less. The heating temperature of the thermocompression bonding is preferably 80°C or more, more preferably 100°C or more, and preferably 140°C or less, more preferably 120°C or less. When the pressure and heating temperature of the thermocompression bonding are above the above lower limit and below the above upper limit, the electrical conductivity reliability between electrodes can be further improved.

[0138] The heating temperature for the thermocompression bonding is at least the melting point of the conductive layer (X) minus 50°C, more preferably the melting point of the conductive layer (X) minus 30°C, even more preferably the melting point of the conductive layer (X) minus 20°C, and is preferably the melting point of the conductive layer (X) plus 100°C or less, more preferably the melting point of the conductive layer (X) plus 50°C or less, even more preferably the melting point of the conductive layer (X) plus 30°C or less. When the heating temperature is not less than the above lower limit and not more than the above upper limit, the reliability of conduction between electrodes can be further improved.

[0139] The first and second connection target members are not particularly limited. Specific examples of the first and second connection target members include electronic components such as semiconductor chips, semiconductor packages, LED chips, LED packages, capacitors, and diodes, as well as electronic components such as resin films, printed circuit boards, flexible printed circuit boards, flexible flat cables, rigid-flexible boards, glass epoxy boards, and glass boards. The first and second connection target members are preferably electronic components.

[0140] 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, molybdenum electrodes, silver electrodes, SUS electrodes, and tungsten electrodes. When the connection target member is a flexible printed circuit board, the electrode is preferably a gold electrode, nickel electrode, tin electrode, silver electrode, or copper electrode. When the connection target member is a glass substrate, the electrode is preferably an aluminum electrode, copper electrode, molybdenum electrode, silver electrode, or tungsten electrode. When the electrode is an aluminum electrode, it may be an electrode made of aluminum alone, 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.

[0141] The thickness of the connection portion is preferably 1 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, particularly preferably 4 μm or more, and is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 30 μm or less, particularly preferably 20 μm or less, and most preferably 10 μm or less. When the thickness of the connection portion is not less than the above lower limit and not more than the above upper limit, the adhesive strength between the electrodes can be improved, and the electrical connection between the electrodes can be improved.

[0142] 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.

[0143] The following materials were prepared:

[0144] (base material particles) Base particle A: Resin particles (acrylate copolymer resin particles, Sekisui Chemical Co., Ltd. "EZ3P-020", average particle diameter 20 μm) Base particle B: Resin particles (divinylbenzene copolymer resin particles, "SP-020" manufactured by Sekisui Chemical Co., Ltd., average particle diameter 2 μm) Base particle C: Resin particles (divinylbenzene copolymer resin particles, "EYP-003" manufactured by Sekisui Chemical Co., Ltd., average particle diameter 3 μm) Base particle D: Resin particles (acrylate copolymer resin particles, "EZ3P-005" manufactured by Sekisui Chemical Co., Ltd., average particle diameter 5 μm) Base particle E: Resin particles (divinylbenzene copolymer resin particles, "SP-050" manufactured by Sekisui Chemical Co., Ltd., average particle diameter 50 μm)

[0145] Example 1 (1) Preparation of conductive particles Formation of the first conductive layer: 10 parts by weight of the above 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 the solution was then 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 surfaces of base particles A. The surface-activated base particles A were thoroughly washed with water, and then added to 500 parts by weight of distilled water and dispersed to obtain dispersion A.

[0146] Furthermore, a nickel plating solution (1) (pH 8.5) containing 0.14 mol / L of nickel sulfate, 0.46 mol / L of dimethylamine borane, and 0.2 mol / L of sodium citrate was prepared.

[0147] While stirring the dispersion A containing 10 parts by weight of base particles A at 70°C, 0.5 parts by weight of a nickel core material (average particle diameter 0.1 μm) was added to the dispersion A and stirred for 10 minutes. Then, nickel plating solution (1) was added dropwise at a rate of 30 mL / min for 10 minutes. Subsequently, the nickel plating solution was added dropwise at a rate of 10 mL / min for 40 minutes, and then at a rate of 4 mL / min for 80 minutes. This controlled the amount of boron incorporated into the plating film, allowing electroless nickel-boron alloy plating to be performed. The resulting dispersion was then filtered to remove the particles, which were then washed with water and dried to obtain particles A in which a core material and a first conductive layer (nickel layer) were disposed on the surface of the base particles A.

[0148] Formation of the second conductive layer: Ten parts by weight of the resulting particles A were dispersed in 500 parts by weight of ion-exchanged water using an ultrasonicator to obtain suspension B. A tin-indium plating solution (1) (adjusted to pH 8.5 with sodium hydroxide) containing 15 g / L of tin sulfate, 34 g / L of indium sulfate, 70 g / L of ethylenediaminetetraacetic acid, 30 g / L of sodium gluconate, and 1.5 g / L of phosphinic acid was prepared. Furthermore, reducing solution A (adjusted to pH 10.0 with sodium hydroxide) containing 5 g / L of sodium borohydride was prepared.

[0149] While stirring the resulting suspension B at 55°C, the tin-indium plating solution (1) was gradually added to suspension B, and then electroless tin-indium plating was performed by reduction with reducing solution A to form a second conductive layer. A second conductive layer (tin-indium alloy layer) was disposed on the surface of the first conductive layer, and conductive particles with protrusions on the surface were obtained.

[0150] (2) Preparation of conductive materials A mixture was obtained by mixing the following materials: 10 parts by weight of bisphenol A epoxy resin ("jER1009" manufactured by Mitsubishi Chemical Corporation); 40 parts by weight of acrylic rubber (weight average molecular weight approximately 800,000); 200 parts by weight of methyl ethyl ketone; 50 parts by weight of microcapsule-type curing agent ("HX3941HP" manufactured by Asahi Kasei E-materials Corporation); and 2 parts by weight of silane coupling agent ("SH6040" manufactured by Toray Dow Corning Silicones Co., Ltd.). Conductive particles were added to this mixture to a content of 3% by weight and dispersed to obtain a conductive material.

[0151] The obtained conductive material was applied to a PET (polyethylene terephthalate) film (separator, thickness 50 μm) with one side treated for release, and dried with hot air at 70°C for 5 minutes to produce an anisotropic conductive film. The thickness of the obtained anisotropic conductive film was 50 μm.

[0152] (3) Fabrication of connection structure A polyimide substrate (flexible printed circuit board) was prepared having an Au electrode pattern (electrode (Au circuit): Ni / Au thin film on Cu) with an L / S of 200 μm / 200 μm on its upper surface. A printed circuit board was also prepared having an Au electrode pattern (electrode (Au bump): Ni / Au thin film on Cu) with an L / S of 200 μm / 200 μm on its lower surface. The resulting anisotropic conductive film was applied to the upper surface of the polyimide substrate at 80°C and 0.98 MPa (10 kgf / cm). 2), and then the separator was peeled off. The Au bumps on the printed circuit board were then aligned with the Au circuits on the polyimide substrate. Next, a pressure and heating head was placed on the top surface of the printed circuit board, and a low pressure of 2 MPa calculated from the bonding area was applied while the anisotropic conductive film was cured at 140°C, yielding a connection structure.

[0153] Examples 2 to 5 Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that the thickness of the second conductive layer was changed as shown in Table 1 below.

[0154] Examples 6 to 8 Conductive particles, conductive materials, and connection structures were obtained in the same manner as in Example 1, except that the type of base particle, the thickness of the first conductive layer, and the thickness of the second conductive layer were set as shown in Table 3 below.

[0155] Example 9 Conductive particles, conductive materials, and connection structures were obtained in the same manner as in Example 1, except that the type of base particle, the thickness of the first conductive layer, and the thickness of the second conductive layer were set as shown in Table 3 below, and the thickness of the anisotropic conductive film was changed from 50 μm to 70 μm.

[0156] Example 10 A tin-bismuth plating solution (1) (adjusted to pH 8.5 with sodium hydroxide) containing 15 g / L of tin sulfate, 41 g / L of bismuth sulfate, 70 g / L of ethylenediaminetetraacetic acid, 30 g / L of sodium gluconate, and 1.5 g / L of phosphinic acid was prepared. Conductive particles having protrusions on their surfaces and a second conductive layer (tin-bismuth alloy layer) disposed on the surface of a first conductive layer (nickel layer) were obtained in the same manner as in Example 1, except that the tin-indium plating solution (1) was replaced with the tin-bismuth plating solution (1) described above and the thickness of the second conductive layer was changed. Conductive materials and connection structures were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0157] (Comparative Example 1) The particles A obtained in Example 1 were thoroughly washed with water and then dispersed in 500 parts by weight of distilled water to obtain a suspension C. 2 L of a gold plating solution (pH 9.0) containing 0.011 mol / L of potassium gold cyanide, 0.20 mol / L of sodium citrate, 0.08 mol / L of ethylenediaminetetraacetic acid, and 0.5 mol / L of sodium hydroxide was also prepared.

[0158] Also, 1.5 L of a reducing agent solution (pH 9.0) containing 0.09 mol / L of dimethylamine borane and 0.10 mol / L of sodium hydroxide was prepared.

[0159] While stirring the obtained suspension C at 55°C, 0.5 L of the gold plating solution was gradually added dropwise to the suspension C. Then, 1.5 L of the gold plating solution and 1.5 L of the reducing agent solution were simultaneously gradually added dropwise to the suspension C to perform gold plating. The suspension C was then filtered to remove the particles, which were then washed with water and dried to obtain conductive particles having a second conductive layer (gold layer) disposed on the surface of the first conductive layer (nickel layer) and having protrusions on the surface. A conductive material and a connection structure were obtained in the same manner as in Example 1, except that the obtained conductive particles were used.

[0160] (Comparative Example 2) Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that the second conductive layer was not formed.

[0161] (Comparative Example 3) Conductive particles, a conductive material, and a connection structure were obtained in the same manner as in Example 1, except that the thickness of the second conductive layer was changed.

[0162] (evaluation) (1) 5% K value of base particles at 25°C The 5% K value of the base particles at 25° C. was measured by the method described above using a microcompression tester (Fisherscope H-100 manufactured by Fisher).

[0163] (2) 0.5% K value and 5% K value of conductive particles at 25°C, and 0.5% K value and 5% K value at 100°C The 0.5% K value and 5% K value at 25°C and the 0.5% K value and 5% K value at 100°C of the obtained conductive particles were measured using a microcompression tester (Fisherscope H-100 manufactured by Fischer) according to the method described above. In addition, the ratio (5% K value of conductive particles at 25°C / 0.5% K value of conductive particles at 25°C) and the ratio (5% K value of conductive particles at 100°C / 0.5% K value of conductive particles at 100°C) were calculated.

[0164] (3) Contact area between the electrode and the conductive particles The resulting connection structure was cut out using an ion milling machine (Hitachi High-Technologies Corporation, "IM4000") to cut a cross section of the connection structure so that it passed through the center of the contact surface between the conductive particles and the electrode, and the cross section was observed using a field emission scanning electron microscope (FE-SEM). In the cross section, the ratio (%) of the length of the contact surface between the conductive particles and the electrode to the particle diameter of the conductive particles (the maximum diameter of the conductive particles in the direction parallel to the contact surface between the conductive particles and the electrode, usually the diameter at the center) was measured, assuming that this was 100%. The contact area between the electrode and the conductive particles was evaluated according to the following criteria:

[0165] [Criteria for determining the contact area between the electrode and conductive particles] ○○○: The ratio of the length of the contact surface between the conductive particles and the electrode exceeds 70% ○○: The ratio of the length of the contact surface between the conductive particles and the electrode is more than 65% and less than 70% ○: The ratio of the length of the contact surface between the conductive particles and the electrode is more than 60% and 65% or less △: The ratio of the length of the contact surface between the conductive particles and the electrode is more than 50% and 60% or less ×: The ratio of the length of the contact surface between the conductive particles and the electrode is 50% or less

[0166] (4) Initial connection resistance The connection resistance A between the upper and lower electrodes of the resulting connection structure was measured using the four-terminal method. Based on the relationship voltage = current × resistance, the connection resistance can be determined by measuring the voltage when a constant current is applied. The initial connection resistance was evaluated according to the following criteria.

[0167] [Initial connection resistance criteria] ○○○: Connection resistance A is 6.8Ω or less ○○: Connection resistance A is over 6.8Ω and 7.1Ω or less ○: Connection resistance A is over 7.1Ω and 7.4Ω or less ×: Connection resistance A exceeds 7.4Ω

[0168] (5) Conduction reliability After the evaluation of "(4) Initial connection resistance," the connection structure was left at 85°C and 85% humidity for 500 hours to conduct a conduction reliability test under a high-temperature, high-humidity environment. After the conduction reliability test, the connection resistance B between the upper and lower electrodes of the connection structure was measured using the four-terminal method. The conduction reliability was evaluated according to the following criteria.

[0169] [Conductivity reliability criteria] ○○○: Connection resistance B is 7.5Ω or less ○○: Connection resistance B is over 7.5Ω and 8.0Ω or less ○: Connection resistance B is over 8.0Ω and 8.7Ω or less ×: Connection resistance B exceeds 8.7 Ω

[0170] The configurations of the conductive particles and the results are shown in the following Tables 1 to 6. The evaluation results of Example 9 are the evaluation results of a connection structure using an anisotropic conductive film with a thickness of 70 μm, but the evaluation results of a connection structure using an anisotropic conductive film with a thickness of 50 μm were similar.

[0171] [Table 1]

[0172] [Table 2]

[0173] [Table 3]

[0174] [Table 4]

[0175] [Table 5]

[0176] [Table 6] [Explanation of symbols]

[0177] 1, 11, 21...Conductive particles 2...Base material particles 3, 13, 23...Conductive parts 3A, 13A, 23A...first conductive layer 3B, 13B, 23B...Second conductive layer 13C...Third conductive layer 21a, 23a, 23Aa, 23Ba…Protrusion 24…core substance 51...Connection structure 52...First connection target member 52a...first electrode 53...Second connecting member 53a...second electrode 54...Connection

Claims

1. A conductive material includes a base particle and a conductive portion disposed on a surface of the base particle, the conductive portion has two or more conductive layers, At least one of the two or more conductive layers has a melting point of more than 100°C and not more than 400°C, Conductive particles, wherein the ratio of the compressive modulus when the conductive particles are compressed by 5% at 25°C to the compressive modulus when the conductive particles are compressed by 0.5% at 25°C is 0.40 or more and 1.00 or less.

2. 2. The conductive particles according to claim 1, wherein the ratio of the compressive modulus when the conductive particles are compressed by 5% at 25°C to the compressive modulus when the conductive particles are compressed by 0.5% at 25°C is 0.40 or more and 0.80 or less.

3. 3. The conductive particles according to claim 1, wherein the ratio of the compressive modulus when the conductive particles are compressed by 5% at 100°C to the compressive modulus when the conductive particles are compressed by 0.5% at 100°C is 0.80 or more.

4. The compressive modulus of the conductive particles when compressed by 0.5% at 25°C is 4000 N / mm ２ More than 8000N / mm ２ The conductive particle according to claim 1 or 2, wherein:

5. The compressive modulus of the conductive particles when compressed by 0.5% at 100°C is 500 N / mm ２ More than 4000N / mm ２ The conductive particle according to claim 1 or 2, wherein:

6. the melting point of the outermost layer of the conductive portion exceeds 100°C, The conductive particle according to claim 1 or 2, wherein the thickness of the outermost layer of the conductive portion is 300 nm or more and 1000 nm or less.

7. The conductive particle according to claim 1 or 2, wherein the outermost layer of the conductive portion contains indium.

8. The conductive particle according to claim 1 or 2, wherein the outermost layer of the conductive portion contains a tin-indium alloy.

9. The conductive particles according to claim 1 or 2, wherein the particle diameter of the conductive particles is 0.5 μm or more and 50 μm or less.

10. The conductive particle according to claim 1 or 2, wherein the base particle is a resin particle.

11. The compressive modulus of the base particle when compressed by 5% at 25°C is 5600 N / mm ２ The conductive particle according to claim 1 or 2, wherein:

12. A conductive material comprising the conductive particles according to claim 1 or 2 and a binder resin.

13. a first connection target member having a first electrode on a surface thereof; a second connection target member having a second electrode on its surface; a connection portion connecting the first connection target member and the second connection target member, The material of the connection portion contains the conductive particles according to claim 1 or 2, A connection structure in which the first electrode and the second electrode are electrically connected by the conductive particles.

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