JP2018172771A - Nickel coating copper particles, joint material, and joining method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide metal particles that can realize low cost and high reliability, and are excellent particularly in thermal conductivity.SOLUTION: Nickel coating copper particles have an average particle size by a laser diffraction/scattering method in a range of 0.5 to 100 μm, and each of which is formed of a core layer and a coating layer that covers at least a part of surface of the core layer, in each of which the coating layer contains nickel elements of 50% or more as a concentration of the number of atoms, and the core layer contains 50 wt.% or more of copper elements. When, with a joint material containing nickel coating copper particles interposed between joint members to be joined containing the nickel coating copper particles, by heating at a temperature in a range of 100°C to 500°C, under a reducing gas atmosphere, a joint layer is formed between the joint members to be joined to join the joint members to be joined.SELECTED DRAWING: None

Description

  The present invention relates to nickel-coated copper particles that can be used in the manufacture of electronic components, a bonding material, and a bonding method using the same.

  In recent years, in an effort to save power, higher power conversion efficiency is being promoted in power converters such as inverters. Among these, the practical application of SiC (silicon carbide) is being studied as a next-generation power device semiconductor material that can be expected to reduce power loss. However, since the driving temperature of the current Si (silicon) power device is about 125 ° C., SiC is assumed to be 250 ° C. or higher, and therefore, a bonding material (hereinafter referred to as a bonding material) for bonding a power semiconductor chip using SiC and a mounting substrate. (Also referred to as “bonding material”) requires reliability during driving in a high temperature region of 250 ° C. or higher.

  Conventionally, a solder material has been used as the bonding material. Regarding this solder material, a lead-free solder material is required by the RoHS directive enforced in the EU in 2006, but a lead-free solder material that can withstand driving in the high temperature region and its alternative material are: Not obtained.

  Joining materials using metal fine particles instead of solder materials are being studied. For example, in Patent Document 1, a bonding strength of about 20 to 40 MPa is obtained by evaporating a volatile component at 200 ° C. and heating at 300 ° C. or 350 ° C. in a silver microparticle bonding material having a size of sub-micrometer to several micrometers. Yes.

  Moreover, it replaces with silver microparticles | fine-particles and the joining material using a lower cost copper microparticle is also disclosed. For example, in Patent Document 2, a bonding material containing copper nanoparticles having a particle size of 1 to 35 nm and copper particles having a particle size of 35 to 1000 nm is subjected to pressure sintering in hydrogen at 400 ° C. for 5 minutes, thereby providing a high bonding strength of 40 MPa or more. The materials shown are proposed.

  As described above, metal particulate bonding materials (also referred to as “nano-sinter bonding materials”) are being developed, but silver particulates (silver sintering) are expensive, and in addition, reliability such as thermal cycle When the property test is carried out, there are problems of coarsening of voids and embrittlement of the bonding layer. On the other hand, although the copper fine particle type (copper sinter type) is low in cost, there is a problem that deterioration due to oxidation occurs.

  In view of this, the present inventor has studied a nickel (Ni) fine particle-based bonding material that is low in cost and is unlikely to be deteriorated by oxidation and that can be expected to have high reliability. For example, in Non-Patent Document 1, a bonding material using 90 nm Ni nanoparticles maintains a bonding strength of 10 MPa or more after a lapse of 1000 cyc in a cooling cycle test of −40 ° C. to + 250 ° C. Disclosed that it shows high reliability that no cracks are observed.

  However, nickel has a thermal conductivity of 90.9 W / m · K, which is lower than silver (420 W / m · K) and copper (398 W / m · K), and guarantees driving in the above high temperature range. Therefore, further improvement of heat dissipation, which is an important characteristic, was expected.

JP2011-236494A JP2013-91835A

Journal of Smart Process Society Vol. 4 No. 4 pages 190-195

  An object of the present invention is to provide metal particles that can realize low cost and high reliability and are particularly excellent in thermal conductivity.

  The present inventors have a core-shell type in which copper having a low cost and excellent thermal conductivity is used as a core layer, nickel is used as a coating layer at a low cost and is not easily deteriorated by oxidation, and high reliability can be expected. It discovered that the said subject could be solved by the nickel covering copper particle which is particle | grains.

The nickel-coated copper particles of the present invention have the following conditions (i) to (iv)
(I) the average particle size by laser diffraction / scattering method is in the range of 0.3-200 μm;
(Ii) formed of a core layer and a coating layer covering at least a part of the surface of the core layer;
(Iii) The coating layer contains nickel element in an atomic number concentration of 50% or more;
(Iv) The core layer contains 50% by weight or more of copper element;
It is characterized by comprising.

  In the nickel-coated copper particles of the present invention, the content of nickel element in the coating layer may be 90% or more in terms of atomic number concentration. Moreover, the average thickness of the said coating layer may exist in the range of 0.01 micrometer-1 micrometer. Further, it may be used for a bonding material.

  In the bonding material of the present invention, the content of the nickel-coated copper particles is in the range of 10 to 90% by weight.

  The bonding material of the present invention may further contain an organic solvent having a boiling point in the range of 100 to 350 ° C., and the content of the organic solvent may be in the range of 2 to 40% by weight. Furthermore, you may contain an organic binder in the range of 0.05 to 5.0 weight% with respect to the total amount of particles.

  Moreover, the joining method of this invention interposes the said joining material between to-be-joined members, and heats it by the temperature within the range of 100 to 500 degreeC in reducing gas atmosphere, to-be-joined member A bonding layer is formed between the members to be bonded, and the members to be bonded are bonded to each other.

  According to the nickel-coated copper particles, the bonding material and the bonding method of the present invention, while maintaining the low cost and high reliability, which are the characteristics of the nickel particle-based bonding material, the copper particle-based characteristics are excellent. It is possible to form a bonding layer having high thermal conductivity. Therefore, for example, it can be suitably used as a bonding material for bonding a power semiconductor chip using SiC and a mounting substrate, which requires reliability during driving in a high temperature region of 250 ° C. or higher. Moreover, it can also be used as a joined body that requires other heat dissipation, such as joining of an LED and an electrode.

Embodiments of the present invention will be described below.

(Nickel coated copper particles)
The nickel-coated copper particles of the present invention have the following conditions (i) to (iv)
(I) the average particle size by laser diffraction / scattering method is in the range of 0.3-200 μm;
(Ii) formed of a core layer and a coating layer covering at least a part of the surface of the core layer;
(Iii) The coating layer contains nickel element in an atomic number concentration of 50% or more;
(Iv) The core layer contains 50% by weight or more of copper element;
It is characterized by comprising.

  When the nickel-coated copper particles are used as, for example, a bonding material, the nickel-coated copper particles are present between the bonded objects to be bonded, the viewpoint of favorably conducting the heat conduction between the bonded objects, and the volume when the bonding layer is formed by heating. From the viewpoint of suppressing shrinkage, the average particle diameter (D50) by laser diffraction / scattering method is in the range of 0.3 to 200 μm, preferably in the range of 0.5 to 100 μm, more preferably 1. ˜30 μm. When the average particle diameter of the nickel-coated copper particles is less than 0.3 μm, the volume shrinkage is large when the bonding layer is formed by heating, and the objects to be bonded are not sufficiently bonded to each other. On the other hand, when the average particle diameter of the nickel-coated copper particles exceeds 200 μm, problems such as poor applicability to the joined body and difficulty in adjusting the bonding layer thickness occur.

  The nickel-coated copper particles have different thermal conductivity depending on the shape and composition of the core layer and the coating layer. However, in order to develop excellent thermal conductivity when the bonding layer is formed, the thermal conductivity is 100 W / m · It is preferable that the shape or composition is K or more.

  If a core layer is a range of said average particle diameter as nickel covering copper particle, a shape and a composition will not ask | require. That is, for the reason of excellent thermal conductivity, the core layer only needs to contain 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more of the copper element. Any other components are not required. Preferred examples of the component other than the copper element include silver, gold, platinum, aluminum, silicon, silicon carbide, aluminum nitride, and diamond having a thermal conductivity of 100 W / m · K or more as a simple substance. Various shapes such as a spherical shape, a polyhedron shape, a fiber shape, a spike shape, and a flake shape can be used. Preferably, the bonding material is spherical or spiked, which is excellent in filling property and bonding strength. More preferably, it has a spike shape.

  Moreover, the manufacturing method of a core layer is not limited, A commercial item may be sufficient. For example, copper powder (product name: Cu-HWQ) manufactured by Fukuda Metal Foil Powder Co., Ltd., copper powder manufactured by Furukawa Chemicals (product name: FMC-10), silicon carbide powder manufactured by Taiheiyo Random (product name: GMF), etc. Commercial products can be preferably used.

  Further, the coating layer may have a nickel element content of 50% or more in terms of atomic number concentration. Below this concentration, when used as a bonding material, the content of nickel element at the surface layer portion and the bonding point is small, so that the bonding strength and reliability are lowered. The content of nickel element is preferably 60% or more, more preferably 80% or more in terms of atomic number concentration. More preferably, it is 90% or more, and most preferably 95% or more.

  Moreover, the external appearance shape of a coating layer and containing components other than a nickel element are not ask | required. The appearance shape of the coating layer represents the shape of the nickel-coated copper particles. For example, spherical shape, polyhedron shape, fiber shape, spike shape, flake shape can be mentioned. Preferably, the bonding material is spherical or spiked, which is excellent in filling property and bonding strength. More preferably, it has a spike shape. Examples of the component other than nickel element include alloys with one or more metals selected from copper, silver, gold, platinum, aluminum and the like, and may further contain silicon, carbon, diamond powder, and the like. .

  Moreover, it is preferable that the average thickness of a coating layer exists in the range of 0.01 micrometer-1 micrometer. If the average thickness of the coating layer is less than 0.01 μm, metal atoms in other particles cannot diffuse into the coating layer, and the bonding strength and reliability tend to be reduced. On the other hand, when the average thickness of the coating layer exceeds 1 μm, the thermal conductivity tends to decrease. The average thickness of the coating layer can be measured from cross-sectional observation with a scanning electron microscope. Further, the coating layer only needs to cover at least a part of the surface of the core layer, but it is preferable that the coating rate is high, and it is more preferable to cover almost the entire surface of the core layer. The “other particles” are, for example, fine particles blended in combination with nickel-coated copper particles in a bonding material.

  In addition, various known methods can be used for producing nickel-coated copper particles. For example, a method of forming a coating layer on the surface of the core layer (particles) by powder plating, sputtering, or the like can be mentioned. Preferably, it is powder plating that is low cost and easy to control the thickness of the core layer.

(Joining material)
In the joined body of the present invention, the content of the nickel-coated copper particles is in the range of 10 to 90% by weight. If it is this range, the joining material which is the feature of nickel covering copper particle, low cost, high thermal conductivity, and hardly to be deteriorated by oxidation can be obtained.

  The bonding material of the present embodiment can further contain an organic solvent having a boiling point in the range of 100 to 350 ° C. as an optional component. The boiling point of the solvent contained in the bonding material is preferably in the range of 150 to 260 ° C. from the viewpoint of practical use. If the boiling point of the organic solvent used is less than 100 ° C, long-term stability tends to be lacking, and if it exceeds 350 ° C, it does not volatilize during heating, resulting in residual carbon in the bonding layer, and sintering of the particles. And tends to inhibit the formation of intermetallic compounds. The joining material is preferably concentrated after adding a high-boiling organic solvent to form a paste.

  As the solvent having a boiling point in the range of 100 to 350 ° C., for example, alcohol-based, aromatic-based, hydrocarbon-based, ester-based, ketone-based, and ether-based solvents can be used. Examples of alcohol solvents include 1-heptanol, 1-octanol, 2-octanol, 2-ethyl-1-hexanol, 1-nonanol, 3,5,5-trimethyl-1-hexanol, 1-decanol, 1-decanol, C7 or more aliphatic alcohols such as undecanol, isobornylcyclohexanol, ethylene glycol, diethylene glycol, propylene glycol, trimethylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butane Polyols such as diol, 1,6-hexanediol, 1,8-octanediol, tetramethylene glycol and methyltriglycol, terpineols such as α-terpineol, β-terpineol and γ-terpineol, and ethylene glycol mono The Pil ether, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, diethylene glycol monohexyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, methyl methoxybutanol, diethylene glycol, dipropylene glycol, 2-phenoxyethanol, 1-phenoxy-2-propanol Alcohols having an ether group such as Examples of the hydrocarbon solvent include octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, and pentadecane.

  The content of the organic solvent in the bonding material of the present embodiment is preferably in the range of 2 to 40% by weight, more preferably in the range of 4 to 30% by weight, and 5 to 15% by weight. Within the range is more preferable. When the content of the organic solvent in the bonding material is less than 2% by weight, the fluidity tends to decrease and the usability as a bonding material tends to decrease. On the other hand, when the content of the organic solvent exceeds 40% by weight, for example, it becomes necessary to repeat coating several times, which causes unevenness, and sufficient bonding strength tends not to be obtained.

  Moreover, in the joining material in this invention, an organic binder can be contained as an arbitrary component. The organic binder contributes to the formation of a massive bonding layer having high bonding strength by connecting nickel-coated copper particles or nickel-coated copper particles and other particles to form a wide-range network structure.

  As the organic binder, any binder that can be dissolved in an organic solvent can be used without particular limitation. For example, a thermosetting resin such as a phenol resin, an epoxy resin, an unsaturated polyester resin, a urea resin, a melamine resin, or polyethylene. Examples thereof include thermoplastic resins such as resin, acrylic resin, methacrylic resin, nylon resin, acetal resin, and polyvinyl acetal resin. Among these, a polyvinyl acetal resin is preferable, and a polyvinyl acetal resin having an acetal group unit, an acetyl group unit, and a hydroxyl unit in the molecule is more preferable.

  The organic binder preferably has a molecular weight of 30000 or more, more preferably 100000 or more in order to suppress the sedimentation of nickel-coated copper particles and other particles and maintain a sufficiently dispersed state.

  Moreover, as said organic binder, commercial items, such as Sekisui Chemical Co., Ltd. product polyvinyl acetal resin (ESREC BH-A; brand name), can be used preferably, for example.

  Moreover, it is preferable that the compounding quantity of the said organic binder in a joining material exists in the range of 0.05 to 5.0 weight% with respect to the total amount of particles in a joining material, More preferably, it is 0.1-2.5. It is in the range of wt%, more preferably in the range of 0.3 to 1.5 wt%, and still more preferably in the range of 0.5 to 1.2 wt%. Here, the “total particle amount” tends to result in insufficient sintering between the nickel-coated copper particles or between the nickel-coated copper particles and the other particles. It tends to be impossible.

The bonding material of the present embodiment can further contain other particles as an optional component. The material and shape of other particles are not limited, but excellent thermal conductivity as a sintered material, such as tin, titanium, cobalt, copper, chromium, manganese, iron, zirconium, tungsten, molybdenum, vanadium, and other base metals, gold And metal elements such as noble metals such as silver, platinum, palladium, iridium, osmium, ruthenium, rhodium and rhenium. These may be contained alone or in combination of two or more. More preferred are cobalt, silver, copper, solder, and nickel, which are excellent in conductivity and sinterability, and more preferred is nickel.
When nickel particles are used as the other particles, the other particles may contain a metal other than nickel in a range of less than 50% by weight. It is preferably 10% by weight or less, and more preferably 2% by weight or less. More preferably, the metal component is only nickel. Hereinafter, the other particles are also referred to as “component A”, and the nickel-coated copper particles are also referred to as “component B”.

Moreover, the particle diameter of the component A has the average primary particle diameter by scanning electron microscope (SEM) observation within the range of 20-300 nm from a viewpoint of a filling property and bondability. For example, when the component B is heated and sintered at a temperature of 300 ° C. to form a bonding layer, the average primary particle size of the component A is preferably in the range of 30 to 200 nm, preferably 30 to 100 nm. It is more preferable to be within the range.
For example, when the component A is nickel particles, when the bonding material is heated and sintered at a temperature of 350 ° C., the average primary particle size of the component A is more preferably in the range of 30 to 160 nm. When the average primary particle size of component A is less than 20 nm, components A tend to aggregate and uniform mixing with component B becomes difficult. On the other hand, when the average primary particle diameter of component A exceeds 300 nm, the sinterability between components A or between component A and component B is insufficient, resulting in a decrease in bonding strength.
In this specification, the average primary particle diameter of component A, including the values used in the examples, was taken with a field emission scanning electron microscope (FE-SEM). Then, 200 are randomly extracted from these, the respective areas are obtained, and the values are calculated on the basis of the number of particles when converted to a true sphere.

  In addition, the component A may contain a nonmetallic element such as an oxygen element or a carbon element. When carbon element is contained in component A, the content is preferably in the range of 0.3 to 2.5% by weight, more preferably in the range of 0.5 to 2.0% by weight. . The carbon element is derived from an organic compound present on the surface of the component A, and contributes to improving the dispersibility of the component A. Therefore, if it is this range, since it has the outstanding dispersibility and electroconductivity, it is preferable. If the carbon content of component A is less than 0.3% by weight, the dispersibility tends to decrease. If it exceeds 2.5% by weight, carbonization occurs after firing to become residual carbon, and the conductivity of the bonding layer Tends to decrease. Further, when component A contains an oxygen element, the sinterability may be lowered, so the content thereof is, for example, 7.5% by weight or less, preferably 2.0% by weight or less, more preferably 1. 0% by weight or less. If it is in this range, since it becomes easier to sinter, it is preferable.

  In addition to the above components, the bonding material can include, for example, a thickener, a thixotropic agent, a leveling agent, a surfactant, and the like as optional components.

  Moreover, when the said joining material contains the component A, it can prepare by mixing the component B and the component A homogeneously. The mixing method is not particularly limited, and a mixing means such as a known mixer can be used.

Moreover, in the said joining material, when the component A is included, it is preferable that the weight ratio (component A: component B) of the component B and the component A exists in the range of 10: 90-90: 10. When the ratio of the component B is larger than the above range, the volume shrinkage is increased during the formation of the bonding layer, and the reliability tends to be lowered. Further, when the ratio of the component B is increased, the number of contacts between the component A and the component B is small, and thus the reliability tends to be lowered. More preferably, it exists in the range of 20: 80-80: 20.
In addition, a compounding ratio can be measured by the cross-sectional observation of the particle | grains, for example by ICP emission spectroscopy analysis (high frequency inductively coupled plasma emission spectroscopy, ICP-OES / ICP-AES) and / or SEM-EDX.

(Preparation of bonding material)
The bonding material can be prepared by mixing component B and an optional component homogeneously. The mixing method is not particularly limited, and a mixing means such as a known mixer can be used. In the preparation of the bonding material, it is preferable to mix component B and component A and then mix with other optional components, but the order of blending is arbitrary, for example, either component A or component B After mixing with other optional components, the other may be added.

(Joining method)
Further, the bonding material is interposed between the members to be bonded, and in a reducing gas atmosphere, for example, in the range of 100 ° C. to 500 ° C., preferably in the range of 200 to 400 ° C., more preferably 230 to 350. By heating at a temperature in the range of ° C., a bonding layer can be formed between the members to be bonded, and the members to be bonded can be bonded to each other. Here, “under a reducing gas atmosphere” includes an atmosphere containing hydrogen gas and an atmosphere containing formic acid. Preferably, it is under an atmosphere containing hydrogen gas with good reduction efficiency.
In this joining method (hereinafter referred to as “the present joining method”), in order to advance the sintering between the components B or between the components B and A, the coating layer surfaces of the components B and A are exposed. It is considered necessary. The heating temperature for volatilizing or decomposing organic substances present on these surfaces and removing the passive layer is preferably 200 ° C. or higher, more preferably 250 ° C. or higher. On the other hand, if the heating temperature exceeds 400 ° C., the periphery of the semiconductor device as the bonded member may be damaged.

  This bonding method is, for example, a step of applying a paste-like bonding material to one or both bonded surfaces of a pair of bonded members (application step), bonding the bonded surfaces together, preferably at a temperature of 200 to 400 ° C. In the range of 250 to 400 ° C., more preferably in the range of 250 to 350 ° C., thereby heating the bonding material (sintering step).

  In the coating process, for example, methods such as spray coating, ink jet coating, and printing can be employed. The bonding material can be applied in an arbitrary shape such as a pattern shape, an island shape, a mesh shape, a lattice shape, or a stripe shape according to the purpose. In the coating step, it is preferable to apply the bonding material so that the thickness of the coating film is in the range of 50 to 200 μm. By applying with such a thickness, defects in the joint portion can be reduced, so that an increase in electrical resistance and a decrease in joint strength can be prevented.

  Moreover, in a baking process, to-be-joined members are performed under pressurization or no pressurization. When performed under pressure, the pressure is preferably 10 MPa or less, more preferably 1 MPa or less. By pressurizing under a low pressure of 10 MPa or less or under no pressure, the firing step can be simplified, and further, damage to the bonded member due to pressurization can be reduced.

  This bonding method can be used, for example, in the bonding of Si-based and SiC-based semiconductor materials and the manufacturing process of electronic components. Here, examples of the electronic component mainly include a semiconductor device and an energy conversion module component. When the electronic component is a semiconductor device, for example, between the back surface of the semiconductor element and the substrate, between the semiconductor electrode and the substrate electrode, between the semiconductor electrode and the semiconductor electrode, between the power device or the power module and the heat dissipation member. It can be applied to joining.

  When bonding electronic components, in order to increase the bonding strength, a contact layer made of a material such as Au, Cu, Pd, Ni, Ag, Cr, Ti, or an alloy thereof is previously provided on one or both of the surfaces to be bonded. It is preferable to provide it. When the material of the surface to be joined is SiC or Si or an oxide film on the surface thereof, a contact layer made of a material such as Ti, TiW, TiN, Cr, Ni, Pd, V, or an alloy thereof is used. It is preferable to provide it.

As described above, in the nickel-coated copper particles of the present invention, most of the parts exposed to the air are composed of nickel element. Nickel forms an oxidation passivation film of nickel oxide on the metal surface in the air, so that the progress of oxidation over a certain level can be suppressed, preventing the material from changing over time even when exposed to high temperatures. And has high reliability. Further, the nickel-coated copper particles dispersed in the bonding layer become a heat path, whereby the thermal conductivity of the entire bonding layer is improved. Thus, both high reliability and high thermal conductivity can be achieved.
Therefore, the bonding material of the present invention can be used particularly suitably for each application used in a high temperature region, for example. For example, for example, it can be suitably used as a bonding material for bonding a power semiconductor chip using SiC and a mounting substrate, which requires reliability during driving in a high temperature region of 250 ° C. or higher. In addition, it can be used for bonding between a semiconductor chip using Si and a mounting substrate, bonding between an LED and an electrode, or the like.

  The features of the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the examples. In the following examples, various measurements and evaluations are as follows unless otherwise specified.

[Measurement of average particle diameter of component A]
The average particle size of component A (other particles) was measured by taking a picture of a sample with a field emission scanning electron microscope (FE-SEM) and randomly 200 samples. The respective areas were determined and the average particle diameter of primary particles was calculated based on the number of particles when converted to a true sphere.

[Measurement of Average Particle Size of Component B]
The average particle size of component B (nickel-coated copper particles) was measured by a laser diffraction / scattering method. The apparatus used was LMS-30 manufactured by Seishin Co., Ltd., and measurement was performed in a flow cell using water as a dispersion medium.

[Preparation of thermal conductivity measurement sample]
Using a stainless steel mask (mask width; 5.0 mm × length; 25.0 mm × thickness; 0.2 mm), the sample is applied onto a glass plate (15 mm × 30 mm × 1 mmt) to form a coating film. Calcination was performed under a nitrogen gas flow mixed with 3% by volume of hydrogen. The obtained fired body could be easily peeled from the glass, and this was used as a sample for measuring thermal conductivity.

[Evaluation of thermal conductivity]
The thermal conductivity was measured by the optical alternating current method using a sample for thermal conductivity measurement, and expressed as a thermal conductivity ratio when the thermal conductivity in Comparative Example 1 was 1.

[Calculation of average thickness of coating layer of component B]
The average thickness of the coating layer of component B was measured by taking a cross-sectional observation image (magnification of 50,000 times) of the sample for thermal conductivity measurement with a scanning electron microscope, and measuring the coating layer thickness of component B for 8 particles. Lengthened and obtained as the average value.

[Preparation of nickel fine particle slurry]
A nickel fine particle slurry was prepared according to the following procedure. The amounts of reagents used and the heat treatment time are shown in Tables 1 and 2.

[Synthesis Example 1]
To 182 parts by weight (910 g) of oleylamine, 18.5 parts by weight (92.5 g) of nickel formate dihydrate was added, and the nickel salt was dissolved by heating at 120 ° C. for 10 minutes under a nitrogen stream. A complexing reaction solution 1 was obtained (the complexing reaction step). 121 parts by weight (605 g) of oleylamine was added to this complexing reaction solution 1 and heated at 180 ° C. for 10 minutes using a microwave to obtain a nickel fine particle slurry 1 (the heat treatment step). The supernatant of this nickel fine particle slurry 1 was removed, washed with toluene and methanol, and then dried with a vacuum dryer to obtain nickel fine particles 1.

[Preparation of nickel slurry]
Take 100 parts by weight of the obtained nickel fine particle slurry 1, add 20 parts by weight of octanoic acid thereto, stir for 15 minutes, and then wash with toluene to obtain nickel slurry 1 (solid content concentration 65.0% by weight). Prepared (Nickel slurry preparation step).
Tables 1 and 2 show the raw materials used, the particle diameter and composition of the obtained nickel fine particles 1, and the solid content concentration of the nickel slurry 1.

[Synthesis Examples 2 to 4]
The complexing reaction liquids 2 to 4, the nickel fine particle slurries 2 to 4, the nickel fine particles are the same as in Synthesis Example 1 except that the weight parts of each raw material, the reaction temperature, and the reaction time are as shown in Tables 1 and 2. 2 to 4 and nickel slurries 2 to 4 were obtained. Tables 1 and 2 show the average particle diameter and composition of the obtained nickel fine particles 2 to 4 and the solid content concentration of the nickel slurries 2 to 4. The nickel fine particles 1 to 4 are other particles corresponding to the “component A”.

[Preparation of nickel paste]
A nickel paste was prepared according to the following procedure. The names and amounts of reagents used are shown in Tables 3 and 4.

[Example 1]
The copper particles (FMC-10 manufactured by Furukawa Chemicals Co., Ltd.) to be the core layer were subjected to nickel plating to prepare nickel-coated copper particles having a core layer of copper particles and a nickel coating layer.
Next, 100 parts by weight of nickel slurry 1, 160 parts by weight of nickel-coated copper particles, 16.0 parts by weight of hexyl carbitol as a solvent, and polyvinyl acetal resin as a binder resin (ESREC BH-A; manufactured by Sekisui Chemical Co., Ltd.) Each of 1.23 parts by weight was weighed and mixed, and concentrated at 60 ° C. and 100 hPa to obtain 245 parts by weight of nickel paste 1 (solid content concentration: 93% by weight). About this nickel paste 1, the heat conductivity measurement sample was produced and the heat conductivity was measured.
Tables 3 and 4 show the raw materials used, the average particle size and composition, the properties of the nickel-coated copper particles, the firing temperature, and the measurement results of the thermal conductivity.

[Examples 2 to 10, Comparative Example 1]
Nickel pastes 2 to 11 were obtained in the same manner as in Example 1 except that the weight parts of the raw materials used and the types of nickel-coated copper particles were as shown in Tables 3 and 4. Furthermore, the heat conductivity measurement sample was produced about the nickel pastes 2-11 by the method similar to Example 1 except having made baking temperature as Table 3 and Table 4, and the heat conductivity was measured. In addition, in the nickel paste 11 of the comparative example 1, it replaced with the nickel covering copper particle and used the copper particle which does not have a coating layer.
Tables 3 and 4 show the raw materials used, the average particle size and composition, the properties of the nickel-coated copper particles, the firing temperature, and the measurement results of the thermal conductivity.

[Evaluation of shear strength (shear strength)]
Shear strength (shear strength) was evaluated according to the following procedure.
Using a stainless steel mask (mask width: 2.0 mm × length; 2.0 mm × thickness: 0.1 mm), the paste 3 obtained in Example 3 and the paste 11 obtained in Comparative Example 1 were each nickel-plated. A coating film was formed by applying to different parts on a copper substrate (width: 10 mm × length; 10 mm × thickness: 1.0 mm). A silicon die (width: 2.0 mm × length; 2.0 mm × thickness: 0.40 mm) was mounted on each coating film, and pressurized at 5 MPa under a nitrogen gas flow in which 3% by volume of hydrogen was mixed. While firing. The shear strength of the obtained bonded body (bonding layer thickness; 10 to 30 μm) was measured with a bonding strength tester (manufactured by Daisy Japan, trade name: Bond Tester 4000). A bond tester tool was pressed from the side of the die at a height of 50 μm from the substrate and a tool speed of 100 μm / second, and the load when the joint was sheared was determined as shear strength (shear strength). The nickel-plated copper substrate is obtained by plating Ni on the surface of a Cu substrate (thickness: 1.0 mm) with a thickness of 4 μm, and the silicon die is bonded to the Si substrate (thickness: 0.40 mm). On the surface, Au is formed by sputtering. The results are shown in Table 5.

  Example 3 uses a nickel paste 3 containing nickel-coated copper particles with high thermal conductivity, so that the bonding layer is compared with the nickel paste 11 of Comparative Example 1 using nickel particles instead of nickel-coated copper particles. As a result, improvement in thermal conductivity was confirmed. Further, the bonding strength of Example 3 was almost the same as that of Comparative Example 1, and it was confirmed that the bonding strength was suitably usable as a bonding material.

As mentioned above, although embodiment of this invention was described in detail for the purpose of illustration, this invention is not restrict | limited to the said embodiment.

Claims (8)

The following conditions (i) to (iv);
(I) the average particle size by laser diffraction / scattering method is in the range of 0.3-200 μm;
(Ii) formed of a core layer and a coating layer covering at least a part of the surface of the core layer;
(Iii) The coating layer contains nickel element in an atomic number concentration of 50% or more;
(Iv) The core layer contains 50% by weight or more of copper element;
Nickel-coated copper particles comprising:   The nickel-coated copper particles according to claim 1, wherein the content of nickel element in the coating layer is 90% or more in terms of atomic number concentration.   The nickel-coated copper particles according to claim 1, wherein an average thickness of the coating layer is in a range of 0.01 µm to 1 µm.   The nickel-coated copper particles according to claim 1, which are used for a bonding material. A bonding material comprising the nickel-coated copper particles according to any one of claims 1 to 4,
Content of the said nickel covering copper particle exists in the range of 10 to 90 weight%, The joining material characterized by the above-mentioned.   The bonding | jointing material of Claim 5 which contains the organic solvent which has a boiling point in the range of 100-350 degreeC, and contains the content of the said organic solvent in the range of 2-40 weight%.   Furthermore, the bonding | jointing material of Claim 5 or 6 which contains an organic binder in the range of 0.05 to 5.0 weight% with respect to the total amount of particles. By interposing the joining material according to any one of claims 5 to 7 between the members to be joined and heating at a temperature in a range of 100 ° C to 500 ° C under a reducing gas atmosphere, A bonding method comprising forming a bonding layer between bonded members and bonding the bonded members together.