Conductive hollow metal particles and method for producing the same

Abstract

The present invention relates to hollow conductive metal particles having soft characteristics. The hollow conductive particles having soft characteristics of the present invention are metal particles in which when an external pressure is applied, the metal layer of the metal particles does not break, and the layer of conductive particles with soft characteristics deforms according to the surface form between the objects to which the pressure is applied. The present invention relates to such hollow conductive metal particles and a method for manufacturing the same.

Description

Technical Field

[0001] The present invention relates to conductive hollow metal particles and a method for manufacturing the same.

Background Art

[0002] Conventionally, there are metal particles used for anisotropic conductive films, electrical connection of elements or substrates, etc., and as an example, there are hollow metal particles. However, conventional hollow metal particles have a problem in that they do not stably provide a contact area sufficient to provide sufficient conductivity to a connection object such as a terminal. In addition, conventional hollow metal particles have a large particle size distribution, and such hollow metal particles with a large particle size distribution have non-uniform sizes, so only some particles with a large size are involved in the connection, and the number of particles involved in the connection and the contact area are not sufficiently provided. As a result, there is a problem in that sufficient conductivity is not provided to the connection object.

Summary of the Invention

Problems to be Solved by the Invention

[0003] An object of the present invention is to solve the problems of the above-described prior art, increase the contact area with a connection object, and as a result, provide conductive hollow metal particles having soft characteristics and a method for manufacturing the same, which improve conductivity.

Means for Solving the Problems

[0004] The hollow conductive metal particles of the present invention for solving the above problems have a metal layer on the surface, there is no internal core particle fixed adjacent to the inside of the metal layer, and there is an empty space adjacent to the inside of the metal layer, having a hollow particle structure, and when the conductive metal particles are pressurized and deformed at a deformation rate of 20%, there is no portion where the metal layer becomes discontinuous and cracks or breaks, which are hollow conductive metal particles having soft characteristics.

[0005] In one embodiment, when the hollow conductive metal particles of the present invention are deformed at a deformation rate of 20% without cracking or breaking such that the conductive metal particles are pressurized and the metal layer becomes discontinuous, the force applied to the conductive metal particles by the pressurization can be 0.5 mN or more and 20 mN or less.

[0006] In one embodiment, the metal layer can contain at least one selected from the group consisting of copper, silver, gold, indium, nickel, and alloys thereof.

[0007] In one embodiment, the hollow conductive metal particles of the present invention have an internal solid substance of the particles that is not fixedly adjacent to the inside of the metal layer, and the maximum particle diameter or length of the internal solid substance of the particles can be 90% or less of the maximum particle diameter of the conductive metal particles.

[0008] In one embodiment, the hollow conductive metal particles of the present invention have an internal solid substance of the particles that is not fixedly adjacent to the inside of the metal layer, and when the conductive metal particles are pressurized and deformed at a deformation rate of 20%, the internal solid substance of the particles may not apply a force to support the metal layer by repelling the deformation of the metal layer.

[0009] In one embodiment, the hollow conductive metal particles of the present invention have an internal solid substance of the particles that is not fixedly adjacent to the inside of the metal layer, and the internal solid substance of the particles can contain at least one of a polymer resin or a carbide of a polymer resin.

[0010] In one embodiment, the particle diameter of the hollow metal particles can be 0.01 μm or more and 1,000 μm or less.

[0011] In one embodiment, the thickness of the metal layer can be 0.002 μm or more and 50 μm or less.

[0012] In one embodiment, the metal layer may include a first plating layer and a second plating layer formed on the first plating layer and containing at least one or more selected from the group consisting of copper, silver, gold, indium, nickel, and alloys thereof.

[0013] Further, the method for manufacturing hollow conductive metal particles of the present invention may include an internal core particle removal step of heating conductive metal particles having a metal layer coated on internal core particles containing a polymer resin to remove all or part of the internal core particles, and an annealing step of heating the conductive metal particles at a temperature equal to or higher than the heating temperature of the internal core particle removal step.

[0014] In one embodiment, the method for manufacturing hollow conductive metal particles of the present invention may further include a metal coating layer forming step of coating and forming a metal layer on the internal core particles containing the polymer resin before the internal core particle removal step.

[0015] In one embodiment, the method for manufacturing hollow conductive metal particles of the present invention may further include a step of coating and forming a further metal layer on the metal layer after the annealing step.

[0016] In one embodiment, the polymer resin can contain at least one resin among polymethyl methacrylate resin, polyacrylonitrile, polystyrene resin, acrylonitrile-styrene-butadiene resin, vinyl resin, polycarbonate resin, polyacetal resin, polysulfone resin, polyphenylene oxide resin, polyester resin, polyolefin resin, and polyurethane resin.

[0017] In one embodiment, the shape of the internal core particles can be spherical, plate-like, fibrous, or amorphous.

[0018] In one embodiment, the coefficient of variation (C.V) of the particle size distribution of the internal core particles calculated by the following formula 1 can be 40% or less.

[0019] Coefficient of variation (C.V, %) = (standard deviation of particle size / average particle size) × 100% - Equation 1

[0020] In one embodiment, the heating temperature in the internal core particle removal step can be set to be equal to or higher than the thermal decomposition temperature at which the polymer chains of the internal core particles are broken by heat and the resin is gasified inside the conductive metal particles.

[0021] In one embodiment, in the internal core particle removal step, the gasified resin can be discharged to the outside of the metal layer through the pores formed in the metal layer.

[0022] In one embodiment, after the internal core particle removal step, there is an internal core substance remaining inside the metal layer, and the mass of the internal core substance can be 90% by mass or less with respect to the mass of the internal core particles before the internal core particle removal step.

[0023] In one embodiment, the heating temperature of the annealing step can be set in the range equal to or higher than the temperature at which the recrystallized texture of the metal layer is formed and equal to or lower than the annealing temperature at which the ratio of the area of the region where the metal layer exists in the total surface area of the conductive metal particles is 80% or more after the annealing step.

[0024] In one embodiment, in the internal core removal step, the heating temperature can be set in the range of 250 to 600 °C, and the heating time can be set in the range of 30 minutes to 3 hours.

[0025] In one embodiment, when the metal layer is a metal layer containing nickel, the heating temperature of the annealing step can be set in the range of 600 to 800 °C, and the heating time can be set in the range of 20 minutes to 3 hours.

Advantages of the Invention

[0026] According to the present invention, it is possible to increase the contact area with the object to be connected and provide hollow metal particles having soft characteristics that improve conductivity.

Brief Description of the Drawings

[0027]

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BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Hereinafter, the hollow conductive metal particles having the soft characteristics of the present invention and a method for manufacturing the same will be described in more detail.

[0029] <Conductive Metal Particles>

[0030] The conductive metal particles of the present invention have a conductive layer containing a metal layer, and all or part of the internal core particles used in the manufacturing process described later are removed from the inside of the conductive metal particles, and a hollow space is formed inside adjacent to the conductive layer. It is a conductive metal particle.

[0031] In the conductive metal particles of the present invention, all of the internal core particles used in the manufacturing process described later may be removed from the inside, and substantially no solid substance may remain inside the conductive layer of the conductive metal particles.

[0032] Alternatively, in the conductive metal particles of the present invention, even after the thermal decomposition process in the internal core particle removal step and the annealing step of the present invention described later, a part of the substance of the internal core particles and / or a part of the thermal decomposition products are not completely removed and remain in a solid state. In this case, the remaining solid substance inside the particles may exist in a state where it does not support the conductive layer inside the conductive metal particles. That is, in the conductive metal particles of the present invention, when the conductive layer is pressed by a force applied from the outside of the conductive metal particles and the conductive metal particles are deformed at a predetermined deformation rate, the solid substance inside the particles may exist in a form that does not support the conductive layer in the direction of resisting the deformation inside the particles. Hereinafter, as described above, even after the thermal decomposition process in the internal core particle removal step and the annealing step of the present invention, a part of the substance of the internal core particles and / or a part of the thermal decomposition products are not completely removed and remain in a solid state inside the conductive metal particles. The remaining substance is referred to as "solid substance inside the particles".

[0033] For example, when the conductive metal particles are pressurized and deformed at a deformation rate of 20%, even if there is an internal solid substance of the particles in a form where there is no support structure that supports this inside the particles and resists the deformation when the conductive layer deforms, it is acceptable. Here, the deformation rate can be measured by the rate of change in the length of the particles before and after deformation in the direction in which the particles are pressurized, and the deformation rate can be appropriately selected according to the connection environment to which the conductive metal particles are applied. In other words, in the present invention, when there is an internal solid substance of the particles inside the conductive metal particles, the maximum particle diameter or length thereof can be equal to or less than a predetermined ratio of the maximum particle diameter of the conductive metal particles. Preferably, the maximum particle diameter or length of the internal solid substance of the particles can be 90% or less, more preferably 80% or less, 60% or less, 40% or less, 20% or less, 10% or less, 5% or less, 3% or less, 1% or less, 0.1% or less of the maximum particle diameter of the conductive metal particles.

[0034] In addition, in the present invention, there may also be a case where a small amount of carbon agent obtained by carbonizing the internal core substance remains inside the conductive layer as a thermal decomposition product of the substance of the internal core particles. Even in such particles, an empty space is formed on the inner side adjacent to the conductive layer, and the remaining carbon agent only occupies a part of the inner space. Therefore, it is a hollow conductive metal particle of the present invention.

[0035] In the conductive metal particles of the present invention, when there is an internal solid substance of the particles, the internal solid substance of the particles may have any shape and may exist in a form that freely moves inside the particles or in a form that adheres to a part inside the particles.

[0036] The metal layer of the present invention can contain at least one or more selected from the group consisting of copper, silver, gold, indium, nickel, and alloys thereof. Preferably, when considering the manufacturing cost, nickel or a nickel alloy can be mentioned.

[0037] When the conductive metal particles of the present invention are pressurized by an external force within a predetermined range, the metal layer has soft characteristics such that it does not crack or break. Preferably, the force applied in addition to a deformation rate of 20% in a state where the metal layer does not crack or break has soft characteristics of 0.5 mN to 20 mN. Thereby, when the conductive metal particles of the present invention are pressurized by a conductive object to be connected, the metal layer does not crack or break, and the contact area with the object to be connected can be increased. As a result, the electrical resistance in the connection with the object to be connected during energization can be reduced.

[0038] The size of the conductive metal particles of the present invention is not particularly limited. For example, the average particle diameter can be 0.01 μm or more and 1,000 μm or less, preferably 0.1 μm or more and 500 μm or less, and more preferably 0.5 μm or more and 300 μm or less. Alternatively, the size of the conductive metal particles of the present invention can be in a range obtained by adding the following range of the thickness of the conductive layer to the above range.

[0039] Also, the thickness of the conductive layer of the conductive metal particles of the present invention is not particularly limited. Preferably, it can be 0.002 μm or more and 50 μm or less, preferably 0.02 μm or more and 50 μm or less, more preferably 0.1 μm or more and 20 μm or less, 0.15 μm or more and 15 μm or less.

[0040] <Manufacturing method of conductive metal particles> The manufacturing method of the conductive metal particles of the present invention includes an internal core particle removal step and an annealing step, and may further include a metal coating layer formation step and / or an additional coating layer formation step. Each step will be described in detail below.

[0041] <Metal coating layer formation step> The metal coating layer formation step of the present invention is a step of forming a metal coating layer on the internal core particles.

[0042] In the present invention, a metal coating layer is formed on the surface of the internal core particles by this step, and all or part of the internal core particles are removed by the internal core removal step described later that follows this step. As a result, the metal coating layer remains as the metal layer described above.

[0043] For this reason, the internal core particles of the present invention are preferably polymer resin particles containing a polymer resin, and as the polymer resin, a conventionally known polymer resin capable of thermal decomposition can be used. The polymer resin is preferably polymethyl methacrylate resin, polyacrylonitrile, polystyrene resin, acrylonitrile-styrene-butadiene resin, vinyl resin, polycarbonate resin, polyacetal resin, polysulfone resin, polyphenylene oxide resin, polyester resin, polyolefin resin (for example, polyethylene, polypropylene, polybutylene, etc.), polyurethane resin, and these can be used alone or in combination of two or more.

[0044] The shape of the internal core particles of the present invention is not particularly limited, and examples include spherical, plate-like, fibrous, or amorphous shapes. Further, as the internal core particles, hollow particles having a void space formed inside the particles can be used, and porous particles having a plurality of holes formed on the surface can also be used. For example, hollow spherical particles, porous spherical particles, etc. can be used. However, in the present invention, the internal core particles are not limited to these, and particles that do not have a void space formed inside or are not porous can also be used.

[0045] Although there is no limitation on the particle size distribution of the internal core particles of the present invention, from the viewpoint of the size uniformity of the conductive metal particles, it is preferable to use particles having a narrow particle size distribution with a coefficient of variation (C.V, Coefficient of variation) % value calculated by the following formula 1 of preferably 20% or less.

[0046] Coefficient of variation (C.V, %) = (standard deviation of particle size / average particle size) x 100 - Formula 1

[0047] Generally, in the case of non-hollow particles, it is even easier to produce particles with a narrow particle size distribution. In the present invention, even when using non-hollow core particles, hollow conductive metal particles can be produced through the internal core removal process and annealing process described later. As a result, hollow conductive metal particles with a narrow particle size distribution can be produced more easily.

[0048] However, according to the present invention, since good soft characteristics can provide a good electrical connection to the object to be connected, even when using internal core particles with a wide particle size distribution, a good electrical connection to the object to be connected can be provided by the good soft characteristics. For example, even when using internal core particles with a wide particle size distribution with a C.V. value of 33% or less, and thus 40% or less, 50% or less, the hollow conductive metal particles produced according to the present invention can provide a good electrical connection to the object to be connected by the good soft characteristics.

[0049] The size of the internal core particles of the present invention is not particularly limited. For example, the average particle diameter can be 0.01 μm or more and 1,000 μm or less, preferably 0.1 μm or more and 500 μm or less, more preferably 0.5 μm or more and 300 μm or less.

[0050] For connection purposes such as in electronic circuits, it is preferable to use spherical internal core particles with an average particle diameter of 0.5 μm or more and 1,000 μm or less, more preferably 1 μm or more and 300 μm or less.

[0051] In one embodiment, the metal coating layer can be formed on the surface of the internal core particles by an electroplating process. For example, an electroless plating process can be used. Alternatively, the metal coating layer can also be formed by a known coating process for forming a metal layer on the surface of the core particles. For example, a vapor deposition method, a sputtering method, etc. can also be used.

[0052] When using a plating process for metal coating, the metal coating layer forming process may include a known plating process, a surface etching process (surface modification process) for removing particulate impurities and increasing surface roughness, a sensitization process of adsorbing an ionic substance (such as Sn) with reducing power on the surface of the material as a process for forming catalyst nuclei (such as Pd, Ag, etc.) necessary for the initial deposition of electroless plating, an activation process of attaching catalyst nuclei to cause a reduction reaction of plating, and a surface treatment process necessary for acceleration for improving reactivity, etc. After dissolving precious metal ions in the reactor, they may be introduced into the plating solution together with a reducing agent to perform a plating process. In one embodiment, it is also possible to select a process that does not use expensive precious metal ions.

[0053] <Internal core removal process> This process is a process of removing all or part of the internal core particles from the internal core particles on which a metal coating layer is formed through a thermal decomposition process, thereby producing hollow metal particles having a metal layer. In the present invention, by removing all or part of the internal core particles, it is possible to remove or reduce the deformation repulsion resistance that may be generated by the internal core during external pressurization of the conductive metal particles. In the present invention, the hollow metal particles that are the result of the internal core removal process mean particles in which an empty space is formed inside adjacent to the metal coating layer when all or part of the internal core particles supporting the metal coating layer are removed by the internal core removal process. Not only particles in which the entire internal core particles are removed and an empty space is formed throughout the inside of the metal coating layer, but also when only part of the internal core particles are removed and the substance or thermal decomposition product of the internal core particles remains, as long as an empty space is formed inside adjacent to the metal coating layer, the deformation repulsion resistance can be removed or reduced, and thus these are referred to as hollow metal particles. For example, even when the internal core particles are thermally decomposed by the thermal decomposition process of the internal core particle removal process and gasified and discharged outside the metal layer as described later, there may be a case where a small amount of carbon agent obtained by carbonizing the internal core substance as a thermal decomposition product of the internal core particle substance remains inside the metal coating layer, and particles in such a state are also the hollow conductive metal particles of the present invention.

[0054] In this process, as will be described later, in order to thermally decompose the internal core particles, the conductive metal particles are heated at a predetermined heating temperature for a predetermined heating time, which is set according to the thermal decomposition temperature of the internal core particles. For example, in this process, the thermal decomposition process can be carried out using a furnace whose process conditions of heating temperature and heating time are set according to the thermal decomposition temperature of the internal core particles. At this time, it is preferable to use a rotary type or an air floating type or the like for the furnace in order to prevent the particles from aggregating with each other during the heating process to the maximum extent.

[0055] Also, in this process, preferably, heating is carried out in an atmosphere of an inert gas such as argon or nitrogen.

[0056] Generally, the behavior of a polymer resin changes with heat. Depending on the characteristics, molecular weight, and molecular structure of the polymer in the polymer resin, there are a glass transition temperature (Tg), a crystallization temperature (Tc) if there is crystallization, and a melting temperature (Tm). The thermal decomposition process in this step is for thermal decomposition carried out at a temperature higher than the above-described thermal behavior of the polymer resin. The polymer resin is heated at a temperature above the thermal decomposition temperature for a predetermined time with the heating temperature, and the polymer chains of the polymer resin are broken by heat and decomposed into unit molecular weights, monomers, and / or molecular units, thereby gasifying the resin. This is a process of reducing the weight of the original polymer of the polymer resin compared to before heating. That is, in the present invention, the thermal decomposition temperature of the polymer resin is the temperature at which the polymer resin is gasified by thermal decomposition by heating and the weight decreases. Such a thermal decomposition temperature can be measured by measuring the change in weight using a TGA (Thermal Gravity Analysis) device while heating the polymer resin. Such a thermal decomposition process is more easily carried out in thermoplastic resins, but is not limited thereto. Even in thermosetting resins such as epoxy, the polymer resin can be thermally decomposed and gasified, so that the weight of the original polymer of the polymer resin can be reduced compared to before heating. According to this step, the polymer resin of the internal core particles is gasified with the polymer chains broken at a high temperature above the thermal decomposition temperature, the resin on the surface of the internal core particles is gradually thermally decomposed, and the thermally decomposed gas passes through the metal coating layer, and the internal core particles are reduced and / or removed. At this time, the gas can be discharged to the outside through the fine pores formed in the metal coating layer, and such fine pores through which the gas can be discharged may be present at least during the internal core removal step. That is, when forming a coating layer on the internal core particles in the metal coating layer forming step, fine pores and cracks can exist in the metal coating layer, and the internal gas can be discharged to the outside of the particles through such fine pores during the thermal decomposition step.Alternatively, among the points where a part of the thickness of the metal coating layer formed in the metal coating layer forming step is thin, fine pores are formed by the pressure due to the generation of internal gas in the thermal decomposition step, and the internal gas can be discharged to the outside of the particles. For this reason, in the metal coating layer forming step, it is preferable to form the metal coating layer with a thickness at which the internal gas generated by thermal decomposition during the internal core removal step can be discharged to the outside, that is, at a thickness at which fine pores through which the internal gas can be discharged to the outside have already been formed or can be formed during the internal core removal step. Here, the fine pores mean a passage through which the internal gas can be discharged to the outside of the particles, and their shape is not limited.

[0057] In this step, there may be a case where a small amount of carbon agent carbonized as a result of thermal decomposition of the internal core substance remains inside the metal coating layer. Alternatively, in this step, a part of the internal core particles may remain without being thermally decomposed, and a part of the core substance may remain inside the metal layer.

[0058] The heating temperature of this step can vary depending on the type of polymer resin. As described above, it is sufficient that the heating temperature is equal to or higher than the thermal decomposition temperature of the polymer resin at which the polymer chains of the polymer resin forming the internal core particles are broken by heat and gasified by being decomposed into unit molecular weights, monomers, and / or molecular units.

[0059] Generally, the resin of the polymer starts thermal decomposition at 250 to 600 °C, and weight loss of the resin due to thermal decomposition occurs. Therefore, the heating temperature of the internal core removal step of the present invention can be in the range of 250 to 800 °C, preferably in the range of 250 to 600 °C.

[0060] In the present invention, the behavior of weight loss of the polymer resin due to the heating temperature is analyzed by a TGA (thermogravimetric analyzer), the thermal decomposition temperature at which the polymer resin gasifies and the weight decreases is measured, and the heating temperature can be set at a temperature equal to or higher than the thermal decomposition temperature. For example, with the heating temperature as the X-axis value and the weight of the conductive particles including the internal core of the polymer resin as the Y-axis value, in the curve of the weight change measured while raising the heating temperature, the point with the steepest slope is set as the thermal decomposition temperature reference value, and the heating temperature can be set based on the reference value. For example, the reference value itself can be set as the heating temperature of the internal core removal step, or within a predetermined variation range inside and outside the reference value, for example, but not limited to this, within a variation range such as 80%, 70%, 50%, 30%, 10%, 5% of the reference value, etc., the heating temperature can be set. Also, when measuring the weight change using TGA, the heating rate of the heating temperature can be set to any temperature per unit time, preferably, it can be set and measured as 100 °C per minute, 50 °C per minute, 30 °C per minute, 15 °C per minute, 5 °C per minute, 3 °C per minute, etc.

[0061] Also, in this step, the temperature can be gradually raised and heated until the above-mentioned heating temperature is reached. The thermal decomposition of the polymer resin at a low temperature requires a very long time, and the thermal decomposition of the polymer resin at a high temperature may cause severe damage to the surface of the metal coating layer due to the rapid generation of decomposition gas. Therefore, in this step, preferably, it is preferable to gradually raise the temperature and heat until the above-mentioned heating temperature so that the metal coating layer is not destroyed.

[0062] In this process, the internal core is pyrolyzed into gas and escapes through the fine pores formed in the metal coating layer. At this time, the surface of the internal core particles in contact with the metal coating layer is pyrolyzed first, and the density of the surface of the core particles decreases. In this process, as the heating time elapses, the mass of the internal core gradually decreases, and finally, hollow metal particles in a state where the internal core does not substantially exist inside the metal coating layer can be created. However, as described above, in the internal core removal process of the present invention, it is also possible to end the heating with a part of the internal core remaining and a void space formed between the metal coating layer and the internal core. Such remaining internal cores can also be further pyrolyzed in the annealing process described later.

[0063] If the heating temperature of this process is excessively higher than the pyrolysis temperature of the polymer resin of the internal core, the pyrolysis and gasification of the polymer resin are too fast, so the metal coating layer can be destroyed in the process of the pyrolyzed gas being discharged outside the metal coating layer. Or, if the heating temperature of this process is too low or the heating time is too short, the pyrolysis of the internal core becomes insufficient, and excessive internal core substances remain. As a result, due to the rapid pyrolysis of the internal core in the process of being heated at a higher temperature in the annealing process described later, the gas pressure inside the metal layer becomes excessively high, and the coated metal layer can also be destroyed. Therefore, in this process, it is preferable to set the heating temperature and heating time of the internal core particles so that the metal layer is not destroyed in the internal core particle removal process and the annealing process.

[0064] Although the core particles may be 100% pyrolyzed by this process, in the present invention, since an annealing process in a higher heating temperature environment follows after the pyrolysis of the core particles in this process, the core particles do not have to be 100% pyrolyzed. However, if there are too many pyrolysis residues of the internal core particles in this process, the metal layer can be destroyed due to the rapid gasification by the higher heating temperature environment and the increase in the internal gas pressure of the metal layer in the subsequent annealing process (Figure 7). Therefore, the mass ratio of the pyrolysis residues of the internal core particles preferably falls below a predetermined range.

[0065] Therefore, in this step, the heating time must be at least sustained until the mass of the remaining inner core material decreases after the thermal decomposition of the inner core in this step, so that the coating metal layer is not destroyed by the rapid thermal decomposition of the remaining inner core in the subsequent annealing step. For this purpose, in this step, the heating time is preferably reduced to 50% or less, more preferably 10% or less, 5% or less, 3% or less, more preferably 1% or less, 0.1% or less, 0.01% or less of the total mass of the inner core particles and the thermal decomposition product after this step with respect to the mass of the inner core particles before this step, until the total mass of the inner core particles and the thermal decomposition product after this step decreases to 90% or less. Although the upper limit of the heating time in this step is not particularly limited, when the inner core is thermally decomposed and discharged to meet the above-mentioned criteria, it is not necessary to continue heating for a longer time, so the upper limit of the heating time can also be set within the range that meets the above-mentioned criteria.

[0066] In this step, by removing all or part of the inner core particles in this way, when the inner core particles exist in their original size, the deformation and rebound resistance that may occur thereby can be removed or reduced.

[0067] In one embodiment, when using polymethyl methacrylate (PMMA) resin as the polymer resin, the heating temperature is 250 - 600 °C, preferably 380 - 500 °C, and the heating time is 30 minutes - 3 hours to thermally decompose the inner core particles and remove all or part of them.

[0068] By this step, the conductive metal particles become hollow conductive metal particles in which all or part of the inner core particles configured to support the metal layer inside do not exist inside the conductive metal particles.

[0069] <Annealing step> This process is a step of manufacturing the hollow conductive metal particles of the present invention having soft characteristics by annealing the hollow metal particles manufactured through an internal core removal process. The annealing process aims to stabilize the stress and structure of the metal coating layer, reduce the hardness and strength of the metal, and improve the formability. In the present invention, the metal structure is stabilized through the step of annealing the hollow metal particles manufactured in the internal core removal process, and hollow metal particles having formable soft characteristics are manufactured.

[0070] For this purpose, in this process, the conductive metal particles are heated at a heating temperature in the range above the heating temperature of the internal core control process and below the melting point of the metal layer.

[0071] Also, in this process, preferably, heating is performed in an atmosphere of an inert gas such as argon or nitrogen.

[0072] In the present invention, the heating temperature for annealing the metal can be set according to the material of the metal layer. According to an embodiment of the present invention, when the metal layer is nickel, it is known that a recrystallized aggregate structure is formed at a recrystallization temperature of approximately 600°C and an aggregate structure is formed at 680°C after the heat treatment process (Journal of the Heat Treatment Society, Vol. 21, No. 3, 2008).

[0073] In the present invention, the hardness can be reduced by the formation of the recrystallized aggregate structure of the nickel metal layer, and the soft characteristics of the nickel metal layer can be obtained.

[0074] When the heating temperature in the annealing process of the hollow nickel particles of the present invention is 600°C or higher and less than 850°C, hollow nickel particles having soft characteristics can be produced. More preferably, when the heating temperature in the annealing process is 625°C or higher, 650°C or higher, and 750°C or lower, 725°C or lower, hollow nickel particles having stable soft characteristics can be produced. When annealing is performed at a heating temperature of less than 600°C, the soft characteristics deteriorate, and there are many hollow nickel particles that crack during pressurization. Therefore, it is preferable to perform annealing at 600°C or higher, which is the temperature at which the formation of a recrystallized aggregate structure occurs. FIGS. 3 to 6 are diagrams showing the shapes of the particles after pressurization of the produced hollow nickel particles when annealing is performed at a heating temperature of less than 600°C. As shown in the figures, the effect of the soft characteristics is very poor, and instead of showing a soft deformation shape due to an external force, a cracked shape appears. Note that FIG. 8 is a diagram showing the shape of the produced nickel particles when annealing is performed at a heating temperature of 850°C or higher. When the heating temperature is 850°C or higher, self-deformation sequentially occurs from the weak part due to the thickness deviation of the metal layer, etc., the continuity of the surface is interrupted, and the continuity of the nickel metal layer is severely damaged in the remaining region except for the aggregated thick surface region. Such conductive particles with severely damaged continuity result in a significantly increased contact resistance with the object to be connected. Therefore, in this step, it is preferable to set the heating temperature for annealing the hollow nickel particles to less than 850°C.

[0075] Thus, the heating temperature in the annealing process of the present invention is preferably set in the range of not less than the temperature at which the recrystallized aggregate structure of the metal layer is formed and not more than the temperature at which the continuity of the metal layer is not damaged after the annealing process. In the present invention, the continuity of the metal layer not being damaged means that the ratio of the area of the region where the metal layer exists in the total surface area of the conductive metal particles is 80% or more, preferably 90% or more, 95% or more, more preferably 99% or more, 99.9% or more.

[0076] Also, the heating time in the annealing process of the present invention is preferably set within a range that is equal to or longer than the heating time during which a recrystallized aggregate structure of the metal layer is formed when heated within the above-mentioned heating temperature range, and equal to or shorter than the heating time during which the continuity of the metal layer is not damaged after the annealing process.

[0077] In one embodiment, when a polymethyl methacrylate (PMMA) resin is used as the polymer resin and the gold coating layer is a metal layer containing nickel, the heating temperature is 600 to 800°C, and the heating time is 20 minutes to 3 hours, preferably 30 minutes to 1 hour. Through the annealing process of heating, the metal layer can have soft characteristics.

[0078] According to this process, a crystal change occurs in the metal layer, and the softness and conductive characteristics can be improved.

[0079] Also, although impurities may be included when the metal coating layer is formed in the metal coating layer forming process, according to this process, such impurities can be decomposed and removed, the metal component of the metal layer can be increased, and the conductive characteristics can be improved. For example, when coating a nickel metal layer by electroless plating, impurities other than conductive metals contained in a reducing agent (such as sodium hypophosphite, dimethylamine borane, sodium borohydride, etc.) and a sensitizer (such as tin chloride, etc.) during the electroless plating process inhibit the conductive characteristics of pure nickel. However, such impurities are decomposed and removed through the annealing process, resulting in an increase in the metal component of pure nickel and an improvement in the conductive characteristics.

[0080] Also, according to this process, even when there are substances of the internal core remaining inside the metal layer and / or thermal decomposition products after the internal core removal process, these can be further decomposed and / or burned.

[0081] In addition, in the present invention, even when the conductive metal particles are pressurized by an external force within a predetermined range through an annealing process, the metal layer has soft properties such that it does not crack or break. Preferably, the force applied in addition to a deformation rate of 20% in a state where the metal layer does not crack or break has soft properties of 0.5 mN to 20 mN. Thereby, when the conductive metal particles of the present invention are pressurized by a conductive connection object, the contact area with the connection object can be increased without the metal layer cracking or breaking. As a result, the electrical resistance in the connection with the connection object during energization can be reduced.

[0082] The thickness of the conductive layer of the conductive metal particles of the present invention is not particularly limited, and preferably can be 0.002 μm or more and 50 μm or less, preferably 0.02 μm or more and 50 μm or less, more preferably 0.1 μm or more and 20 μm or less, 0.15 μm or more and 15 μm or less.

[0083] The hollow conductive metal particles having soft properties of the present invention are interposed between connection objects and, when pressurized and / or heated, can be deformed without cracking or breaking, and can be freely deformed corresponding to the surface properties and shape of the connection objects. In one embodiment, the hollow conductive metal particles having soft properties of the present invention can be deformed without the particles being broken as shown in FIGS. 1 and 2. Therefore, according to the conductive metal particles of the present invention, the contact area and / or the number of contact points with the connection object can be improved. As a result, the contact resistance between the conductive metal particles and the connection object can be reduced, and the conductivity can be improved.

[0084] <Additional coating layer forming step> In one embodiment, the present invention can further include an additional coating layer forming step of forming an additional conductive layer on the metal layer in order to strengthen the elasticity, restoring force, and / or supporting force of the metal layer of the conductive metal particles.

[0085] In one embodiment, a metal layer of the same material as the already formed metal layer can be additionally coated to further thicken the conductive layer, thereby improving the elasticity of the conductive layer and reducing the electrical resistance. Or, a metal layer such as copper, silver, gold, indium, etc. whose metal itself has soft characteristics can be additionally coated on the already formed metal layer to modify the performance such as the elasticity, deformability, and conductivity of the conductive layer.

[0086] In one embodiment, a further metal coating layer can be formed on the surface of the conductive metal particles by a plating process. For example, a further metal coating layer can be formed by an electroless plating process. Or, the coating layer can also be formed by a known coating process for forming a conductive layer on the surface of the core particles. For example, vapor deposition methods, sputtering methods, etc. can also be used.

[0087] According to the present invention, after forming a metal coating layer having functions such as conductivity and / or electromagnetic shielding on internal core particles of various shapes and various components, it is possible to manufacture hollow conductive metal particles having soft characteristics through a process of decomposing and annealing the internal core. According to the present invention, when the conductive metal particles are interposed between connection objects, the contact area with the connection objects can be increased. As a result, the contact resistance can be reduced and the conductivity can be improved.

[0088] Since the conductive metal particles manufactured by the present invention are hollow metal particles having soft characteristics, their shape is deformed by the pressing surface during use. Therefore, when the conductive metal particles of the present invention are used as a conductive material in the form of an anisotropic conductive film, a heat-sealing connector, or a tape for adhering up and down, even if there are some particles with large sizes in the particles, the particles will deform without cracking during pressing and are pressed and deformed by a size corresponding to the terminal distance, film, or coating thickness. Therefore, when using the conductive metal particles of the present invention, the contact area becomes large at the pressed portion, the contact resistance characteristics are improved, and at the same time, there is no shape in which large particles protrude. A large number of particles contribute to the connection between terminals, the connection conductivity becomes good, and a product with a low roughness on the surface of the film or coating layer can be obtained.

[0089] The hollow conductive metal particles having the soft characteristics of the present invention can be used to make electrical contact with an object to be connected and conduct electricity. For example, they are suitable for use as a conductive material for connecting electrodes such as anisotropic conductive films (ACF), heat seal connectors, display panels, and other conductive materials to a circuit board for connection.

[0090] Example Hereinafter, the present invention for producing the hollow conductive metal particles having the soft characteristics of the present invention will be described in more detail based on examples. However, the scope of the present invention is not limited to such examples.

[0091] [Example 1] Electroless plating uses the pretreatment and electroless plating processes described below. As the internal core particles, PMMA 20-μm spherical particles with a narrow particle size distribution having a C.V% value of 20% or less in the particle size distribution were used.

[0092] Electroless plating pretreatment process As a pretreatment for electroless plating, an etching process (surface modification process) (PT01-01, Pretreatment 01-01 process) for removing impurities and imparting surface roughness is performed. Due to the conditions in the manufacturing process of the polymer resin particle powder, impurities are present in the particle powder, and such impurities must be removed in order to obtain a uniform plating quality. For this purpose, impurities can be removed using an MEK aqueous solution, a sodium hydroxide aqueous solution, an ethanol aqueous solution, hydrochloric acid, a sulfuric acid aqueous solution, a chromic acid aqueous solution, etc., and the chemicals can be used differently or mixed depending on the state of the internal core powder.

[0093] In Example 1, 4 g of PMMA powder is washed 2 to 3 times with an 80% ethanol aqueous solution and physically filtered to remove impurities.

[0094] Next, in order for the plating to adhere uniformly to the surface of the particles, a step of increasing the surface roughness is performed. As the step of increasing the roughness, 7 g of potassium permanganate (KMnO 4 ) is dissolved in 100 ml of distilled water at 80°C, then 6 g of sodium hydroxide (NaOH) is dissolved, PMMA powder is added, and the mixture is stirred for 10 minutes. Then, it is washed several times with distilled water and filtered through filter paper to increase the surface roughness. Thereafter, PMMA powder for the inner core with a rough surface on which nickel can be well reductively deposited is obtained.

[0095] Thereafter, the PMMA powder is stirred in 100 ml of an aqueous solution of 2% ammonium hydroxide (NH 4 OH) for 10 minutes, then washed several times with distilled water, filtered through filter paper, the inner core powder with a finely rough surface is neutralized, then washed several times and filtered to obtain the inner core powder that has undergone a neutralization process with a pH of 5 to 6. (PT01-2 process)

[0096] Thereafter, 2 g of tin chloride (SnCl 2 ) is dissolved in 100 ml of distilled water at 50°C, the inner core powder with increased roughness and enhanced adhesion after the above pretreatment is stirred for 10 minutes, then washed several times with distilled water and physically filtered to undergo a process of increasing activation so that a chemical plating reaction occurs well on the surface (PT02-01 process).

[0097] The thus-activated inner core powder is stirred in 100 ml of distilled water at 55°C after dissolving 0.1 g of palladium chloride (PdCl 2 ) in distilled water for 10 minutes to generate palladium (Pd, Palladium) fine particles on the surface of the inner core powder. (PT02-02 process)

[0098] Thereafter, for the activation of the reaction of the Pd fine particles generated on the surface of the inner core powder particles, 10% hydrochloric acid (HCl) is put into 100 ml of distilled water at 50°C, the inner core powder is put in, stirred for 10 minutes, washed several times with distilled water and physically filtered to prepare a powder with Pd catalyst attached to the surface (PT02-03). Thereby, all the pretreatment of the inner core powder is completed.

[0099] Electroless plating process In the present invention, in order to form a plating layer on the surface of the internal core powder surface-treated in the above pretreatment step, an aqueous solution of Ni chloride salt or Ni sulfide salt, and a reducing agent such as sodium hypophosphite, dimethylamine borane (DMAB), dimethylamine borane, hydrazine, etc. can be used, and two or more of these can be mixed and used.

[0100] Furthermore, in the plating step of the present invention, a stabilizer and a dispersant for effective electroless nickel deposition can also be used. Although not particularly limited, for example, nonionic, cationic, and water-soluble polymer substances can be used. As the nonionic surfactant, polyoxyalkylene ether-based ones such as polyethylene glycol, polyoxyethylene alkyl ether, and polyoxyethylene alkyl phenyl ether can be used. As the cationic surfactant, betaine-based surfactants such as alkyl dimethyl acetic acid betaine, alkyl dimethyl carboxymethyl acetic acid betaine, and alkyl dimethyl amino acetic acid betaine can be used. As the water-soluble polymer, polyvinyl alcohol, polyvinyl pyrrolidone, hydroxyethyl cellulose, etc. can be used. Also, compounds of Group IV elements (i.e., selenium-based, thiourea, thiocyanate, etc.), unsaturated organic acids (i.e., maleic acid, itaconic acid, etc.), oxygen-containing anions (i.e., molybdate anion, etc.), cetyl trimethyl ammonium bromide (CTAB), etc. can be used. Also, citrate-based, hydroxyacetic acid, stannic acid, malic acid, gluconic acid, sodium acetate and sodium citrate, glycine, etc. can be used as complexing agents. Also, two or more of these can be mixed and used.

[0101] In Example 1, the electroless reduction reaction is carried out as follows by selectively using the exemplified chemical substances.

[0102] In this embodiment, prior to entering the electroless reduction reaction, in order to improve the dispersibility, the inner core powder pretreated through the plating pretreatment steps (PT01-01 to PT02-3) specified above is put into 100 ml of distilled water at 70 to 75 °C, 0.01 g of PVP and 0.01 g of CTAB are added, and stirred for 20 minutes to prepare the inner core powder solution after the pretreatment is completed.

[0103] After that, a solution of 1 mol of nickel sulfide salt and 1 mol of glycine is prepared in a 100 ml beaker, and 2 mol of sodium hypophosphite as a reducing agent, 1 mol of hydrazine, and 1 mol of sodium hydroxide as a pH adjuster are separately prepared in a 100 ml beaker.

[0104] While maintaining the Ni aqueous solution and the reducing solution prepared as above at 70 to 75 °C, 100 ml of the inner core powder solution after the pretreatment is completed is stirred, and they are added little by little using a micro rotary metering pump respectively. In this embodiment, dropping is performed for 30 to 60 minutes, and the reaction is carried out for 90 to 120 minutes to stably deposit Ni on the inner core powder, inducing the formation of nuclei so that plating can be performed.

[0105] The conductive metal powder thus prepared is washed several times with distilled water, physically filtered, and dried, and finally manufactured into conductive metal particles having a plating layer with a nickel plating layer of 0.200 to 0.450 μm.

[0106] Internal core removal process The thermal decomposition process must be set differently according to the thermal decomposition behavior of the polymer resin. In this embodiment, the PMMA particles used are N 2In a furnace with a quartz tube that can create a gas environment and is capable of in / out, a pyrolysis process is carried out under a nitrogen environment, heating from room temperature of about 25°C to 450°C over 2 hours and maintaining for 1 hour. At this time, the internal core is decomposed, turns into gas, escapes through the pores on the surface of the plating layer, is decomposed first at the surface part of the internal core particles in contact with the plating layer, and finally, there is substantially no internal core resin in the nickel metal layer, and hollow conductive metal particles with a nickel layer plated are manufactured. The heating rate can be set to 2 - 15 minutes / °C in the final stage, but in this example, the heating rate was set within 3 - 5°C / min. The heating rate conditions can be changed according to the performance and capacity of the furnace equipment so that there is no serious damage to the plating surface.

[0107] Annealing process After manufacturing the hollow conductive metal particles manufactured above, in the furnace used above, heat is raised from 450°C to 725°C over 30 minutes and maintained for 30 minutes for a total of 1 hour in an N 2 atmosphere for annealing, and then cooled gradually sufficiently in an N 2 atmosphere to manufacture hollow nickel metal particles with soft characteristics. The heating rate can be set to 5 - 20 minutes / °C in the final stage, but in this example, the heating rate was set within 5 - 10°C. Depending on the performance of the equipment, it can also be extended for several more hours for sufficient annealing.

[0108] [Example 2] Set the temperature of the annealing process in the steps of Example 1 to 750°C, the same as the above heating and maintaining conditions, and carry out annealing in an N 2 atmosphere, and then cool gradually sufficiently in an N 2 atmosphere to manufacture hollow nickel metal particles with soft characteristics.

[0109] [Example 3] In order to increase the thickness of the plating layer in the steps of Example 1, up to the annealing process, it was the same as Example 1, and further soft metal Ag was additionally plated to manufacture hollow nickel / silver multi-layer metal particles with soft characteristics.

[0110] [Example 4] In the process of Example 1, in order to increase the thickness of the plating layer, the process was made the same as that of Example 1 up to the annealing process, and furthermore, soft metal Au was additionally plated to produce hollow nickel / gold multilayer metal particles having soft characteristics.

[0111] [Example 5] In Example 5, about 1.5 g of hollow polyacrylonitrile (PAN) powder with a tap density (ASTM B527) of 0.2 - 0.4 g / cc was stirred in 65°C ethanol aqueous solution with a concentration of 80% by distilled water for 50 minutes, washed 2 - 3 times with distilled water, physically filtered to remove impurities. Then, 6 g of sodium hydroxide (NaOH) was dissolved in 100 ml of distilled water, the internally core powder treated as above was put in, and stirred for 10 - 30 minutes. Then, it was washed several times with distilled water and filtered with filter paper to strengthen the adhesion so that nickel on the surface could be well reductively adhered. In the case of PAN powder, plating on the surface was possible without separately performing processes such as surface etching with a strong solvent, and this was omitted.

[0112] After that, the above powder was put into 100 ml of distilled water at 60°C, and 2 g of stannous chloride (SnCl 2 ) was mixed with 50 ml of distilled water and 50 ml of 20% hydrochloric acid solution to prepare 100 ml of a mixed solution, stirred for 60 minutes, then washed several times with distilled water and physically filtered to go through the process of increasing activation so that the chemical plating reaction could occur well on the surface.

[0113] In this example, the pretreated PAN powder was put into 100 ml of distilled water at 70 - 75°C, 0.01 of PVP and 0.01 g of CTAB were added, and stirred for 20 minutes for preparation.

[0114] After that, a solution of 1 mol of nickel sulfide salt and 1 mol of glycine was prepared in a 100 ml beaker, and 2 mol of sodium hypophosphite as a reducing agent, 1 mol of hydrazine, and 1 mol of sodium hydroxide as a pH regulator were separately prepared in a 100 ml beaker.

[0115] The Ni salt aqueous solution prepared in this way is stably adhered, nuclei are formed, and plating is induced so that plating can be performed.

[0116] The conductive metal powder thus prepared is washed several times with distilled water, physically filtered and dried, and finally manufactured into hollow conductive metal particles having a nickel plating layer of 0.200 to 2 μm and containing about 80% of nickel plating PAN resin inside. At this time, since the inner core itself of the prepared hollow conductive particles is hollow, the time for thermal decomposition can be reduced, but the thermal decomposition conditions were made the same in order to compare the differences in the annealing process to be performed next.

[0117] After performing the inner core decomposition step of Example 1 on the conductive metal particles thus obtained, the temperature of the annealing step of Example 1 was set to 650 ° C, which was the same as the above-mentioned temperature raising and maintaining conditions, and N 2 Annealing was carried out in an atmosphere, and N 2 Annealing was carried out in an atmosphere, and the mixture was gradually cooled sufficiently to produce hollow nickel metal particles having soft characteristics.

[0118] [Comparative Example 1] In Example 1, the annealing step was not performed, and only the inner core removal step was performed to produce hollow nickel conductive particles having no soft characteristics.

[0119] [Comparative Example 2] The temperature of the annealing step in the process of Example 1 was set to 550 ° C, which was the same as the above-mentioned temperature raising and maintaining conditions, and N 2 Annealing was carried out in an atmosphere, and N 2 Annealing was carried out in an atmosphere, and the mixture was cooled to produce hollow nickel metal particles having soft characteristics.

[0120] In Comparative Example 2, the annealing temperature was less than 600 ° C, and the effect of soft characteristics was very poor. As shown in FIGS. 3 to 6, the particles showed a shape that cracked without showing a soft deformation shape by an external force. In Comparative Example 2, cracks occurred in the particles due to an external force, the conductive characteristics decreased, and the resistance increased.

[0121] [Comparative Example 3] The temperature of the annealing process in the steps of Comparative Example 1 was set to 850 °C, which was the same as the above heating rate and holding conditions, and annealing was carried out in an N 2 atmosphere, and then cooled sufficiently slowly in an N 2 atmosphere to produce hollow nickel metal particles having soft characteristics.

[0122] When the temperature of the annealing process is 850 °C or higher, self-deformation occurs sequentially from the weak parts due to the thickness deviation of the metal layer, etc., and the surface continuity is interrupted (Figure 8). Only the thick nickel surface aggregates and remains, and holes without a surface are formed in the remaining weak parts, showing a shape in which the plating layer is severely damaged or aggregated. Such severely damaged conductive particles showed a result that the resistance was significantly increased.

[0123] [Comparative Example 4] The temperature of the annealing process was set to 550 °C as in the steps of Example 5, which was the same as the above heating rate and holding conditions, and annealing was carried out in an N 2 atmosphere, and then cooled in an N 2 atmosphere to produce hollow nickel metal particles having soft characteristics. Similar to Comparative Example 2, cracks in the particles occurred due to an external force, showing characteristics of a decrease in conductive properties and an increase in resistance.

[0124]

Table 1

[0125] The breaking strength was measured using a Microhardness tester of the FISCHERSCOPE HM2000 model at a measurement temperature of 25°C (room temperature) and a measurement speed of 0.33 mN / sec. The force at the length where 10%, 20%, and 30% of the total particle diameter undergoes deformation was measured, and the examples were compared with the comparative examples. The force applied in addition to the typical 20% deformation rate is preferably 0.5 mN to 20 mN or less, particularly 1 to 15 mN or less.

[0126] The Comprehensive Assessment (CA) in Table 2 below based on the above characteristic values is a quantification of the measured values of three factors, namely resistance, softness characteristics, and cracking after pressurization, which are the main factors considered in the characteristics of the conductive hollow metal particles, into a single numerical value by combining them. This is a single numerical value conversion to facilitate the composite characteristic evaluation of products that must meet various reference values simultaneously, and is defined as follows.

[0127] CA (Comprehensive Assessment) = (resistance characteristic) × weighting value 1 + (softness characteristic) × weighting value 2 + (no cracking after pressurization) × weighting value 3 - Equation 2

[0128] Referring to Table 2 below, in Equation 2, the performance superiority and inferiority indicated by the measured values presented in the comparative examples and the examples were easily evaluated by classifying them into three levels: excellent, ordinary, and poor, and assigning 5 points, 3 points, and 1 point respectively. The weighting values for each factor were determined to magnify the differences between performances according to their importance to judge the superiority and inferiority of the performances. In Table 2 below, for the essential resistance characteristic and the presence or absence of cracking under pressure, the weighting values 1 and 3 were set to 3 points each to formulate the weighting values, and for the softness characteristic indicating the force at a 20% deformation rate, the weighting value 2 was increased to 5 points.

[0129]

Table 2

[0130] Figures 9 and 10 are photographs after compression when one conductive metal particle was repeatedly pressurized 5 times with a pressure of 3 mN using a Micro-compression Testing Machine of the Shimadzu MCT-510(E) model.

[0131] Figure 9 shows hollow conductive metal particles having softness characteristics manufactured according to Example 1. As shown in the photograph of Figure 9, they are easily deformed during pressurization, indicating an increase in the number of contact points and the contact area with the object to be pressurized on the upper surface. On the other hand, Figure 10 shows conductive metal particles manufactured according to Comparative Example 1. As shown in the photograph of Figure 10, they are not easily deformed during pressurization, indicating that the contact points and the contact area with the object to be pressurized are substantially maintained without change.

[0132] Figure 11 is a diagram comparing the change in resistance due to compression between the hollow conductive metal particles with softness characteristics manufactured according to Example 1 and the conventional conductive metal particles having a core. As confirmed from Figure 11, the hollow conductive metal particles according to the present invention have improved softness characteristics compared to the conventional conductive particles having a core, with an increase in the number of contact points and the contact area with the object to which an external force is applied, resulting in improved conductivity and the advantageous effect that the force causing compression deformation is smaller.

Claims

1. Hollow conductive metal particles, having a metal layer on the surface, having a hollow particle structure in which there are no internal core particles fixed adjacent to the inside of the metal layer and there is an empty space adjacent to the inside of the metal layer, characterized in that when the conductive metal particles are pressurized and deformed at a deformation rate of 20%, there is no portion where the metal layer becomes discontinuous and cracks or breaks, and having soft characteristics.

2. When the conductive metal particles are pressurized and deformed at a deformation rate of 20% without cracking or breaking so that the metal layer becomes discontinuous, the force applied to the conductive metal particles by the pressurization is 0.5 mN or more and 20 mN or less. The hollow conductive metal particles having soft characteristics according to Claim 1.

3. The metal layer contains at least one selected from the group consisting of copper, silver, gold, indium, nickel, and alloys thereof. The hollow conductive metal particles having soft characteristics according to Claim 1.

4. having an internal solid substance of the particles not fixed adjacent to the inside of the metal layer, wherein the maximum particle diameter or length of the internal solid substance of the particles is 90% or less of the maximum particle diameter of the conductive metal particles. The hollow conductive metal particles having soft characteristics according to Claim 1.

5. having an internal solid substance of the particles not fixed adjacent to the inside of the metal layer, when the conductive metal particles are pressurized and deformed at a deformation rate of 20%, the internal solid substance of the particles does not apply a force to support the metal layer by repelling the deformation of the metal layer. The hollow conductive metal particles having soft characteristics according to Claim 1.

6. having an internal solid substance of the particles not fixed adjacent to the inside of the metal layer, wherein the internal solid substance of the particles contains at least one of a polymer resin or a carbide of a polymer resin. The hollow conductive metal particles having soft characteristics according to Claim 1.

7. The particle diameter of the hollow metal particles is 0.01 μm or more and 1,000 μm or less. The hollow conductive metal particles having soft characteristics according to Claim 1.

8. The thickness of the metal layer is 0.002 μm or more and 50 μm or less. The hollow conductive metal particles having soft characteristics according to Claim 1.

9. The metal layer is, a first plating layer, A second plating layer that is formed on the first plating layer and contains at least one or more selected from the group consisting of copper, silver, gold, indium, nickel, and alloys thereof, and the hollow conductive metal particles having soft characteristics according to claim 1.

10. A method for manufacturing hollow conductive metal particles according to any one of claims 1 to 9, An internal core particle removal step of heating conductive metal particles coated with a metal layer on internal core particles containing a polymer resin and removing all or part of the internal core particles, An annealing step of heating the conductive metal particles at a temperature equal to or higher than the heating temperature in the internal core particle removal step, and a method for manufacturing hollow conductive metal particles.

11. The method for manufacturing hollow conductive metal particles according to claim 10, further comprising a metal coating layer forming step of coating the internal core particles containing the polymer resin with a metal layer before the internal core particle removal step.

12. The method for manufacturing hollow conductive metal particles according to claim 10, further comprising a step of coating and forming a further metal layer on the metal layer after the annealing step.

13. The polymer resin contains at least one resin selected from the group consisting of polymethyl methacrylate resin, polyacrylonitrile, polystyrene resin, acrylonitrile-styrene-butadiene resin, vinyl resin, polycarbonate resin, polyacetal resin, polysulfone resin, polyphenylene oxide resin, polyester resin, polyolefin resin, and polyurethane resin. The method for manufacturing hollow conductive metal particles according to claim 10.

14. The shape of the internal core particles is spherical, plate-like, fibrous, or amorphous. The method for manufacturing hollow conductive metal particles according to claim 10.

15. The coefficient of variation (C.V) of the particle size distribution of the internal core particles calculated by the following formula 1 is 40% or less. The method for manufacturing hollow conductive metal particles according to claim 10. Coefficient of variation (C.V, %) = (particle size standard deviation / average particle size) x 100% - Formula 1

16. The heating temperature in the internal core particle removal step is set to be equal to or higher than the thermal decomposition temperature at which the polymer chains of the polymer resin of the internal core particles are broken by heat and the resin is gasified inside the conductive metal particles. The method for manufacturing hollow conductive metal particles according to claim 10.

17. The manufacturing method of the hollow conductive metal particles according to claim 16, wherein in the internal core particle removing step, the gasified resin is discharged to the outside of the metal layer through pores formed in the metal layer.

18. After the internal core particle removing step, there is an internal core substance remaining inside the metal layer, The mass of the internal core substance is 90% by mass or less with respect to the mass of the internal core particles before the internal core particle removing step, in the manufacturing method of the hollow conductive metal particles according to claim 10.

19. The heating temperature of the annealing step is set in a range that is equal to or higher than the temperature at which a recrystallized aggregate structure of the metal layer is formed, and is equal to or lower than the annealing temperature at which the ratio of the area of the region where the metal layer exists in the total surface area of the conductive metal particles is 80% or more after the annealing step, in the manufacturing method of the hollow conductive metal particles according to claim 10.

20. In the internal core removing step, the heating temperature is set in the range of 250 to 600 °C, and the heating time is set in the range of 30 minutes to 3 hours, in the manufacturing method of the hollow conductive metal particles according to claim 10.

21. When the metal layer is a metal layer containing nickel, the heating temperature of the annealing step is set in the range of 600 to 800 °C, and the heating time is set in the range of 20 minutes to 3 hours, in the manufacturing method of the hollow conductive metal particles according to claim 10.

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