Copper particles and their manufacturing method, paste composition, semiconductor device, electrical component, and electronic component

Abstract

Copper particles according to the present invention are characterized in that, in an X-ray diffraction, a ratio SCu(111) / SCu(220) of a crystallite diameter SCu(111) for a Miller index (111) of copper with respect to a crystallite diameter SCu(220) for a Miller index (220) of copper satisfies formula (1) or formula (2).　(1): SCu(111) / SCu(220)>1.4 (2): SCu(111) / SCu(220)<1.2

Description

[Technical Field]

[0001] The present disclosure relates to copper particles, a method for producing copper particles, a paste composition, and semiconductor devices, electrical components, and electronic components bonded with the paste composition. [Background technology]

[0002] As semiconductor products become larger, faster, and have finer wiring, they generate a lot of heat during operation. Therefore, thermal management, or the ability to dissipate heat from semiconductor products, is becoming increasingly important. For this reason, semiconductor products generally employ methods such as attaching heat dissipation components, such as heat spreaders and heat sinks. Materials used to bond heat dissipation components are required to have higher thermal conductivity.

[0003] Semiconductor elements may also be bonded to organic substrates with heat dissipation mechanisms such as thermal vias. In this case, too, high thermal conductivity is required for the materials used to bond semiconductor elements. Furthermore, due to the recent increase in brightness of white-emitting LEDs, materials used to bond semiconductor elements are also widely used in lighting devices such as backlights for full-color LCD screens, ceiling lights, and downlights. The high current input associated with the high output of light-emitting elements can cause the adhesive connecting the light-emitting element to the substrate to discolor due to heat and light, and its electrical resistance to change over time. In particular, when relying on adhesives to bond light-emitting elements to the substrate, the adhesive strength of the bonding material decreases at the solder melting temperature during soldering of electronic components, resulting in peeling and failure of the device. Furthermore, as the performance of white-emitting LEDs increases, the heat generated by the light-emitting element chip increases, requiring improved heat dissipation capabilities in the LED structure and the components used in them.

[0004] In particular, in recent years, there has been active development of power semiconductor devices that use wide-bandgap semiconductor elements such as silicon carbide (SiC) and gallium nitride (GaN), which have low power loss. These elements themselves have high heat resistance, allowing them to operate at high temperatures of over 250°C with large currents. However, to fully utilize these characteristics, the heat generated during operation must be efficiently dissipated, and bonding materials that have long-term high-temperature resistance in addition to electrical conductivity and heat transfer are required.

[0005] As described above, high thermal conductivity is required for die attach pastes and heat dissipation member adhesive materials used to bond semiconductor devices, electrical components, and electronic components, and these materials must also be able to withstand the reflow process that occurs when the products are mounted on a substrate.

[0006] As a paste material that can meet such requirements, attention has been drawn to a bonding method using silver nanoparticles, which allows bonding at a lower temperature than bulk silver (see, for example, Patent Document 1). Although silver particles have very high conductivity, their high cost and migration problems have led to the study of alternative metals, and attention has been drawn to copper particles, which are cheaper than silver particles and have migration resistance. A bonding material containing copper nanoparticles and copper microparticles or copper submicroparticles, or both, has been proposed (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-240406 [Patent Document 2] Japanese Patent Application Laid-Open No. 2014-167145 Summary of the Invention

[0008] That is, the present disclosure relates to the following: [1] In X-ray diffraction, the crystallite size S of copper at Miller index (220)Cu Crystallite size S of copper at Miller index (111) relative to (220) Cu (111) ratio S Cu (111) / S Cu (220) satisfies the following formula (1) or the following formula (2): S Cu (111) / S Cu (220)>1.4···(1) S Cu (111) / S Cu (220)<1.2···(2) [6] In X-ray diffraction, the crystallite diameter S at Miller index (111) Cu2О A method for producing copper particles according to any one of the above [1] to [5], characterized in that cuprous oxide having a (111) of 70 nm or more is reduced in the presence of a shape stabilizer. [8] A paste composition containing the copper particles according to any one of the above items [1] to [5]. [9] A semiconductor device bonded using the paste composition described in [8] above.

[10] An electrical part bonded using the paste composition described in [8] above.

[11] An electronic component bonded using the paste composition described in [8] above. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a cross-sectional view illustrating a semiconductor device according to an embodiment of the present disclosure. [Figure 2] 1 is a cross-sectional view illustrating an electrical component according to an embodiment of the present disclosure. [Figure 3] 1 is a scanning electron microscope image of a copper cake according to Example 3. [Figure 4] 1 is a scanning electron microscope image of a copper cake according to Example 5. [Figure 5] 1 is a scanning electron microscope image of a copper cake according to Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] Pastes using sinterable copper nanoparticles often have reliability issues due to the voids in the bonding layer formed by sintering. In particular, when bonding LEDs and other components, the bonded body is often sealed with silicone resin, which has high oxygen permeability, or is exposed to the atmosphere, which can lead to oxidation of the bonding layer during reliability tests such as thermal cycling tests, resulting in a decrease in reliability. The present disclosure relates to copper particles that have high bonding strength and that can be sintered to obtain highly dense and reliable semiconductor devices, etc., a method for producing copper particles, a paste composition, and semiconductor devices, electrical components, and electronic components bonded with the paste composition.

[0011] Hereinafter, the present disclosure will be described in detail with reference to an embodiment. In the present disclosure, the "non-volatile content concentration" or "solid content concentration" of a composition means the concentration of components excluding the solvent in the total amount of the composition.

[0012] In this specification, the expression "XX to YY" means "XX or more and YY or less." Furthermore, in this specification, for numerical ranges (e.g., ranges of content, etc.), lower and upper limits described in stages can be independently combined. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in the examples.

[0013] <Copper particles> The copper particles according to the present disclosure have a crystallite diameter S Cu Crystallite size S of copper at Miller index (111) relative to (220) Cu (111) ratio S Cu (111) / S Cu (220) is a copper particle that satisfies the following formula (1) or the following formula (2). S Cu (111) / S Cu (220)>1.4···(1) S Cu (111) / S Cu (220)<1.2···(2) The copper particles according to the present disclosure may contain copper oxide as long as they satisfy formulas (1) and (2).

[0014] The copper particles have good bonding strength, and by sintering, it is possible to obtain a highly dense and reliable semiconductor device, etc. The reason for this is not clear, but is presumed to be as follows. That is, the ratio S Cu (111) / S Cu When (220) is 1.2 or more and 1.4 or less, the trade-off between sintering activity and sintering inhibition due to the particle size cannot be resolved. When (220) is more than 1.4 or less than 1.2, the trade-off can be resolved and high sinterability can be obtained.

[0015] The ratio S Cu (111) / S Cu (220) can be controlled by appropriately adjusting the reduction rate after the formation of the nuclei that will become the plate-shaped particles (plate-shaped copper particles). The formation of the nuclei that will become the plate-shaped particles is influenced by a number of extremely complex factors, including the temperature during nucleation, the reduction rate, the type of shape stabilizer, and the critical saturation concentration. For example, when the nucleation temperature is high, when the crystallinity of the cuprous oxide is low, or when the number of carbon atoms in the carboxylic acid that makes up the shape stabilizer is small, it is often difficult to form the nuclei that will become the plate-shaped particles. From this viewpoint, the above formula (1) may be the following formula (1A), the following formula (1B), the following formula (1C), or the following formula (1D). S Cu (111) / S Cu (220)≧1.45···(1A) S Cu (111) / S Cu (220)≧1.46···(1B) S Cu (111) / S Cu (220)≧1.48···(1C) S Cu (111) / S Cu (220)≧1.5 (1D) S in the above formulas (1A) to (1D)Cu (111) / S Cu There is no particular upper limit to the value of (220). From the viewpoint of ease of production, etc., it may be 10 or less, 5.0 or less, 3.0 or less, or 2.0 or less. From this viewpoint, the above formula (2) may be the following formula (2A), the following formula (2B), the following formula (2C), or the following formula (2D). S Cu (111) / S Cu (220)≦1.0 (2A) S Cu (111) / S Cu (220)≦0.8 (2B) S Cu (111) / S Cu (220)≦0.6 (2C) S Cu (111) / S Cu (220)≦0.5 (2D) S in the above formulas (2A) to (2D) Cu (111) / S Cu There is no particular limitation on the lower limit of the value of (220). From the viewpoint of ease of production, etc., it may be 0.1 or more, 0.2 or more, 0.3 or more, or 0.4 or more.

[0016] The crystallite diameter S Cu The (111) may be 60 nm or less. When it is 60 nm or less, high sinterability can be ensured. From this point of view, the crystallite size S Cu (111) may be 5 to 60 nm, may be 5 to 50 nm, may be 10 to 40 nm, or may be 15 to 40 nm. The crystallite diameter S Cu (220) may be 70 nm or less. When it is 70 nm or less, high sinterability can be ensured. In addition, the crystallite diameter S Cu From the viewpoint of ensuring high sinterability, the (220) crystallite diameter S Cu(220) may be 5 to 70 nm, 10 to 50 nm, or 15 to 35 nm.

[0017] In the present disclosure, the crystallite diameter S Cu The (111) is calculated by the Scherrer method using the peak of the Miller index (111) plane obtained by X-ray diffraction (XRD) measurement. Specifically, it can be measured by the method described in the examples. In the present disclosure, the crystallite diameter S Cu (220) is calculated by the Scherrer method using the peak of the Miller index (220) plane obtained by X-ray diffraction (XRD) measurement. Specifically, it can be measured by the method described in the examples.

[0018] The copper particles may be plate-shaped. The thickness of the copper particles may be 5 nm or more and 50 nm or less, or 10 nm or more and 40 nm or less, from the viewpoint of reducing oxidation and ensuring denseness of the bonding layer. Furthermore, from the viewpoint of reducing oxidation and improving the density of the bonding layer, the major axis of the copper particles may be 30 nm or more and 300 nm or less, 50 nm or more and 200 nm or less, 60 nm or more and 200 nm or less, or 70 nm or more and 150 nm or less. From the above viewpoint, the copper particles may have a thickness of 5 to 50 nm and a diameter of 30 to 300 nm. The plate-like particle has a shape having a pair of substantially parallel flat surfaces, the distance between the pair of flat surfaces being the "thickness" and the longest diameter on the flat surfaces being the "major diameter". From the above viewpoint, the aspect ratio (long diameter / thickness) of the copper particles may be 1.5 or more and 10 or less, 1.8 or more and 10 or less, 2.0 or more and 8.0 or less, 3.0 or more and 6.0 or less, or 4.0 or more and 6.0 or less.

[0019] The thickness and major axis of the copper particles are calculated as the median of the measured length values ​​of at least 200 copper particles extracted from images taken using a scanning electron microscope (e.g., JEOL Ltd., product name: JSM-F100; SEM) at an acceleration voltage of 15 kV and 100,000 magnification. The median of the measured thickness of copper particles is the thickness of the (n / 2)th particle counting from the smallest particle when the thickness of n copper particles is measured. n The thickness of the {(n / 2)+1}th particle counting from the smallest particle is d n+1 Then, {(d n +d n+1 ) / 2}. The median of the measured values ​​of the long diameter of copper particles is the value obtained by measuring the long diameter of n copper particles and counting from the smallest particle, taking the long diameter of the (n / 2)th particle as L n Let the long diameter of the {(n / 2)+1}th particle counting from the smallest particle be L n+1 Then, {(L n +L n+1 ) / 2}. If n is an odd number and the first decimal place of (n / 2) is 5, the decimal point shall be rounded up.

[0020] From the viewpoint of sinterability and bondability, the mass coverage of the shell portion covering the surface of the core portion of the copper particles may be 0.05% or more, 0.1% or more, 0.2% or more, or 0.5% or more. The upper limit of the mass coverage may be 10%, 7%, 5%, or 3%. When the mass coverage is 0.05% or more, the particles are less likely to aggregate, ensuring paste fluidity. When the mass coverage is 10% or less, sintering inhibition can be reduced.

[0021] The copper particles according to the present disclosure may be particles having a core made of copper and no shell on the surface of the core (hereinafter sometimes referred to as single-layer particles). The copper particles according to the present disclosure may have a core made of copper and a shell made of a shape stabilizer, the shell being at least one of an amine and a fatty acid. Furthermore, the copper particles according to the present disclosure may have a core portion made of copper and a shell portion formed from a phosphoric acid derivative. The shell portion of the copper particles may be formed from at least one of an amine and a fatty acid and a phosphoric acid derivative, or may be formed from an amine, a fatty acid, and a phosphoric acid derivative.

[0022] [Single-layer particle or core part] The copper constituting the single-layer particles having a copper core and no shell on the surface of the core, or the copper constituting the core of copper particles having a copper core and a shell, is derived from a copper compound. The copper compound is not particularly limited as long as it contains copper atoms. Examples of copper compounds include copper oxide, copper hydroxide, copper nitride, and copper carboxylate. From the viewpoint of the production rate of plate-like particles, the copper compound may be copper oxide. These compounds may be used alone or in combination of two or more.

[0023] The copper oxide may be at least one of copper(I) oxide (cuprous oxide) and copper(II) oxide, and may be copper(I) oxide from the viewpoint of productivity. The copper oxide may be highly crystalline from the viewpoint of the production rate of plate-shaped particles, and may be copper(I) oxide having a crystallite diameter of 70 nm or more in terms of Miller index (111) by X-ray diffraction, particularly from the viewpoint of the aspect ratio of the plate-shaped particles. Crystallite diameter S Cu2О The cuprous oxide having a (111) of 70 nm or more may be reduced in the presence of a shape stabilizer, which will be described later, to produce single-layer particles or core portions. This increases the production rate of plate-shaped copper particles. Cu2О(111) may be 100 nm or more, 400 nm or more, 600 nm or more, 700 nm or more, or 800 nm or more. Cu2О There is no particular limit to the upper limit of (111), but it may be 3000 nm or less, 2000 nm or less, 1500 nm or less, 1200 nm or less, or 1000 nm or less.

[0024] Examples of copper hydroxide include copper(II) hydroxide and copper(I) hydroxide. Examples of copper nitride include copper(II) nitride and copper(I) nitride.

[0025] Examples of copper carboxylates include copper carboxylate anhydrides or hydrates such as copper(I) formate, copper(I) acetate, copper(I) propionate, copper(I) butyrate, copper(I) valerate, copper(I) caproate, copper(I) caprylate, copper(I) caprate, copper(I) formate, copper(II) acetate, copper(II) propionate, copper(II) butyrate, copper(II) valerate, copper(II) caproate, copper(II) caprylate, copper(II) caprate, and copper(II) citrate. From the viewpoints of productivity and availability, copper(II) acetate monohydrate may also be used as the copper carboxylate. These may be used alone or in combination.

[0026] The carboxylate copper may be commercially available or may be synthesized.

[0027] The copper carboxylate can be synthesized by a known method, for example, by mixing and / or heating copper (II) hydroxide with a carboxylic acid compound.

[0028] The copper particles are coated with an amine and / or a carboxylic acid, which are components constituting the shape stabilizer and coat the copper particles during the copper particle production process.

[0029] [Shell] The shell of the copper particles having a core and a shell may be formed from a shape stabilizer, which improves particle independence and results in uniform sintering. The shape stabilizer may be at least one selected from the group consisting of an amine compound, a carboxylic acid, and a neutralized salt of an amine compound and a carboxylic acid. The shell may also be formed from a phosphate ester. The shell portion may be formed from at least one selected from the shape stabilizer and a phosphate ester, or may be formed from the shape stabilizer and a phosphate ester.

[0030] <<Amine compounds>> Examples of the amine compound used in the present disclosure include monoamines having one amino group and diamines having two amino groups. Examples of monoamines include dipropylamine, butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, 3-aminopropyltriethoxysilane, dodecylamine, oleylamine, monoethanolamine, 2-aminoethoxy-2-ethanol, 3-amino-1-propanol, and 3-amino-2-propanol. Examples of diamines include ethylenediamine, N,N-dimethylethylenediamine, N,N'-dimethylethylenediamine, N,N-diethylethylenediamine, N,N'-diethylethylenediamine, 1,3-propanediamine, 2,2-dimethyl-1,3-propanediamine, N,N-dimethyl-1,3-diaminopropane, N,N'-dimethyl-1,3-diaminopropane, N,N-diethyl-1,3-diaminopropane, 1,4-diaminobutane, 1,5-diamino-2-methylpentane, 1,6-diaminohexane, N,N'-dimethyl-1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, etc. Among these, from the viewpoint of the production rate of copper particles, alkanolamines may be used, and alkanolamines having 4 or more carbon atoms may also be used.

[0031] <<Carboxylic Acid>> Carboxylic acids of the present disclosure include monocarboxylic acids such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid (octanoic acid), octylic acid, nonanoic acid, capric acid (decanoic acid), oleic acid, stearic acid, isostearic acid, etc. Dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, diglycolic acid, etc. Examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, and gallic acid. Hydroxy acids include glycolic acid, lactic acid, tartronic acid, malic acid, glyceric acid, hydroxybutyric acid, tartaric acid, citric acid, and isocitric acid. Among these, from the viewpoint of the production rate of copper particles, a monocarboxylic acid may be used, or a monocarboxylic acid having 6 or more carbon atoms may be used. The use of a monocarboxylic acid having 6 or more carbon atoms strengthens the stabilization of the copper atoms produced by reduction, thereby reducing the seed crystal production rate and particle growth rate, and tends to produce copper particles satisfying the above formula (1) or (2). The number of carbon atoms in the monocarboxylic acid may be 7 or more, or 8 or more. The number of carbon atoms in the monocarboxylic acid may be 20 or less, 16 or less, or 12 or less. The monocarboxylic acid may be decanoic acid or octanoic acid.

[0032] The neutralized salt of an amine compound and a carboxylic acid used in the present disclosure includes the neutralized salts of the above-mentioned amine compounds and the above-mentioned carboxylic acids. For example, a neutral salt of an alkanolamine having 4 or more carbon atoms and a fatty acid having 6 or more carbon atoms can be mentioned.

[0033] <<Phosphate ester>> The copper particles may be coated with a phosphate ester. The phosphate ester has the effect of removing an oxide film formed on the surface of the copper particles due to exposure to the atmosphere during heating, thereby increasing the sinterability of the copper particles. In addition, the phosphate ester has a lubricating effect on the copper particles when made into a paste composition, which makes it possible to equalize the volume shrinkage caused by solvent evaporation during curing and form a dense bonding layer.

[0034] The acid value and amine value of the phosphate ester may both be 130 mg KOH / g or less, 120 mg KOH / g or less, or 110 mg KOH / g or less. When the acid value and amine value of the phosphate ester are both below these values, changes in the oxidation degree of the copper particles can be minimized. Here, the acid value (mg KOH / g) can be calculated in accordance with JIS K 0070:1992, and the amine value can be calculated in accordance with JIS K 7237:1995.

[0035] The ratio of the acid value to the amine value of the phosphate ester (acid value / amine value) may be 0 or more and 1.5 or less, or 0 or more and 1.2 or less. When the ratio (acid value / amine value) is within the above range, the change in the oxidation degree of the copper particles can be reduced.

[0036] Examples of the phosphate ester include alkyl phosphates, polyoxyethylene alkyl ether phosphates, polyoxyethylene alkyl phenyl ether phosphates, etc. More specific examples include DISPERBYK (registered trademark; hereinafter abbreviated)-102 (acid value: 101 mg KOH / g), DISPERBYK-111 (acid value: 129 mg KOH / g), DISPERBYK-145 (acid value: 76 mg KOH / g, amine value: 71 mg KOH / g), DISPERBYK-180 (acid value: 94 mg KOH / g, amine value: 94 mg KOH / g), DISPERBYK-185 (amine value: 17 mg KOH / g), DISPERBYK-190 (acid value: 10 mg KOH / g), DISPERBYK-2155 (amine value: 48 mg KOH / g), etc.

[0037] The copper particles may have an oxidation degree of 0.01% or more and 5.0% or less, 0.02% or more and 2.6% or less, 0.05% or more and 2.5% or less, or 0.1% or more and 2.0% or less. By setting the oxidation degree to 0.01% or more, the particles are less likely to be oxidized by exposure to the atmosphere and have good sintering stability, while by setting the oxidation degree to 3.0% or less, the particles are more likely to be sintered. The degree of oxidation can be determined, for example, by using an X-ray diffractometer and analyzing the data obtained by the Rietveld method.

[0038] <Method of manufacturing copper particles> An example of a method for producing copper particles is a method in which a copper compound is reduced with a reducing compound in the presence of a shape stabilizer. The copper compound and shape stabilizer may be those described above in the section <Copper particles>.

[0039] The reducing compound is not particularly limited as long as it has the reducing power to reduce the copper compound and liberate metallic copper, and examples thereof include hydrazine derivatives. Examples of hydrazine derivatives include hydrazine monohydrate, methylhydrazine, ethylhydrazine, n-propylhydrazine, i-propylhydrazine, n-butylhydrazine, i-butylhydrazine, sec-butylhydrazine, t-butylhydrazine, n-pentylhydrazine, i-pentylhydrazine, neo-pentylhydrazine, t-pentylhydrazine, n-hexylhydrazine, i-hexylhydrazine, n-heptylhydrazine, n-octylhydrazine, n-nonylhydrazine, n-decylhydrazine, n-undecylhydrazine, n-dodecylhydrazine, cyclohexylhydrazine, phenylhydrazine, 4-methylphenylhydrazine, benzylhydrazine, 2-phenylethylhydrazine, 2-hydrazinoethanol, acetohydrazine, etc. These may be used alone or in combination of two or more.

[0040] The copper compound, the shape stabilizer, and the reducing compound may be mixed in an organic solvent. The organic solvent may be any solvent that exhibits the properties of the complex formed from the mixture obtained by mixing the above-mentioned raw materials. Any solvent that can be used as a reaction solvent may be used without particular limitation. Among these, alcohols that are compatible with the reducing compound may be used.

[0041] Examples of the alcohol include 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butyl carbitol, butyl carbitol acetate, ethyl carbitol, ethyl carbitol acetate, diethylene glycol diethyl ether, butyl cellosolve, etc. These may be used alone or in combination of two or more.

[0042] In the mixing, the amounts of the copper compound, the shape stabilizer, and the reducing compound used may be such that, relative to 1 mol of the copper compound, the shape stabilizer is 0.5 mol to 10 mol and the reducing compound is 0.5 mol to 5 mol, or the shape stabilizer is 1 mol to 6 mol and the reducing compound is 0.8 mol to 3 mol. When both an amine compound and a carboxylic acid are used as the shape stabilizer, the amount of the carboxylic acid used per 1 mol of the amine compound may be 0.1 to 10 mol, 0.5 to 10 mol, 1 to 5 mol, or 1.5 to 3 mol. The organic solvent may be used in an amount that allows each component to react sufficiently, for example, in an amount of about 10 volumes or more and 1000 volumes or less per 100 volumes of at least one compound selected from the shape stabilizers.

[0043] Next, the mixture is heated sufficiently to promote the reduction reaction of the copper compound, which can eliminate unreacted copper compounds and allow metallic copper to be favorably precipitated and grown to form copper particles. The heating temperature of the mixture may be -20°C or higher and 140°C or lower, 25°C or higher and 120°C or lower, or 40°C or higher and 100°C or lower. The heating time may be 20 minutes or higher and 360 minutes or lower, 30 minutes or higher and 300 minutes or lower, or 40 minutes or higher and 240 minutes or lower. When the heating temperature and heating time are within the above ranges, the oxidation degree of the resulting copper particles can be easily controlled within the above ranges. The heating may be performed after the reducing compound is mixed in. This allows the critical saturation state to be established at a relatively low temperature, reduces the by-production of granular seed crystals that tend to be generated at high temperatures, and selectively produces plate-shaped seed crystals, making it easier to obtain copper particles that satisfy the above-mentioned formula (1) or (2).

[0044] The mixture is preferably heated at a given rate, which can increase the rate of plate-like particle formation. For example, starting from a reaction temperature of 25°C, the mixture is heated to 100°C at a rate of 5°C / min, which can promote the reaction to form plate-like particles.

[0045] The mixture is preferably heated in a stepwise manner, which can increase the rate of plate-like particle formation. For example, the reaction for forming plate-like particles can be carried out at 25°C for 10 minutes, 40°C for 60 minutes, 80°C for 10 minutes, and 100°C for 180 minutes.

[0046] The solid matter precipitated by heating is preferably separated from the excess (a) amine compound and / or (b) carboxylic acid amine salt by centrifugation or the like, washed with an organic solvent, and then centrifuged to obtain a copper cake. Copper particles (copper cake) can be obtained by such an operation. The organic solvent for cleaning may be an alcohol. Examples of alcohol include ethanol, 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, diethylene glycol, 1,3-propanediol, 1,2-propanediol, butyl carbitol, butyl carbitol acetate, ethyl carbitol, ethyl carbitol acetate, diethylene glycol diethyl ether, and butyl cellosolve. For example, ethanol and diethylene glycol may be used. These may be used alone or in combination of two or more. The copper cake may contain copper particles and the organic solvent. When the copper cake contains an organic solvent, the content of copper particles (solid content) in the copper cake may be 50 to 95 mass %, 65 to 90 mass %, or 75 to 85 mass %. The content of copper particles and the content of organic solvent in the copper cake can be determined by measuring the weight loss upon heating. The washing can be appropriately adjusted by adjusting the number of washings, the amount of organic solvent used, the washing time, and the like. The number of washings may be, for example, 2 to 20 times, 3 to 16 times, 4 to 12 times, or 5 to 10 times. The amount of the organic solvent used may be, for example, 10% by volume or more, 100% by volume or more, or 1000% by volume or more, in terms of volume ratio relative to the copper particles. The cleaning time may be 1 minute or more and 40 minutes or less, 3 minutes or more and 35 minutes or less, or 5 minutes or more and 30 minutes or less.

[0047] <Paste composition> The paste composition according to the present disclosure contains the copper particles. The content of the copper particles may be 10% by mass or more and 95% by mass or less, 20% by mass or more and 90% by mass or less, or 30% by mass or more and 85% by mass or less, based on the total amount of the paste composition.

[0048] The paste composition of the present disclosure may contain a phosphate ester, such as those listed above. The amount of the phosphate ester added may be 0.01% by mass or more and 2.0% by mass or less, 0.1% by mass or more and 1.8% by mass or less, or 0.5% by mass or more and 1.5% by mass or less, relative to the total amount of the paste composition.

[0049] The paste composition of the present disclosure may contain an organic solvent. The organic solvent may be an alcohol, such as an aliphatic alcohol, such as an aliphatic monohydric alcohol or an aliphatic polyhydric alcohol. Examples of the aliphatic monohydric alcohol include propanol. Examples of the aliphatic polyhydric alcohol include glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 3-methyl-1,5-pentanediol, glycerin, and polyethylene glycol. These organic solvents may be used alone or in combination of two or more.

[0050] When the paste composition of the present disclosure contains an organic solvent, the content thereof may be 10 parts by mass or more and 50 parts by mass or less, or 20 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of copper particles. When the content is 10 parts by mass or more, the viscosity does not become too high, and workability can be improved, and when the content is 50 parts by mass or less, a decrease in viscosity is reduced, and sinking of copper in the paste composition is reduced, and reliability can be improved.

[0051] In addition to the above components, the paste composition of the present disclosure may contain various additives, such as thermosetting resins, curing accelerators, stress reducing agents such as rubber and silicone, coupling agents, antifoaming agents, surfactants, colorants such as pigments and dyes, polymerization inhibitors, antioxidants, and other additives that are generally blended into compositions of this type, as needed. Each of these additives may be used alone or in combination of two or more.

[0052] <Method of manufacturing paste composition> The paste composition of the present disclosure can be prepared by thoroughly mixing the above-mentioned copper particles and, if necessary, additives such as second copper particles, phosphate ester, organic solvent, thermosetting resin, and coupling agent, followed by further kneading using a disperse, kneader, triple-roll mill, or the like, and then degassing.

[0053] The viscosity of the paste composition of the present disclosure may be 20 Pa·s or more and 300 Pa·s or less, or 40 Pa·s or more and 200 Pa·s or less. The bonding strength of the paste composition of the present disclosure may be 25 MPa or more, or 30 MPa or more. The viscosity and bonding strength can be measured by the methods described in the examples.

[0054] The paste composition of the present disclosure obtained in this manner has good storage stability and oxidation resistance, and can maintain high sinterability and bondability without being affected by the time of exposure to the atmosphere before curing.

[0055] By using the paste composition of the present disclosure, a bonded body having good connection reliability against temperature cycles can be obtained. It is clear that the bonded body has good connection reliability against temperature cycles even when not sealed with an epoxy sealant or the like.

[0056] <Semiconductor devices, electrical components and electronic components> The semiconductor device, electrical component, and electronic component of the present disclosure are bonded using the paste composition described above, and therefore have high reliability.

[0057] The semiconductor device of the present disclosure is formed by bonding a semiconductor element to a substrate serving as an element support member using the paste composition described above. That is, the paste composition is used as a die attach paste, and the semiconductor element and the substrate are bonded and fixed via this paste.

[0058] 1 shows an example of a semiconductor device according to the present disclosure. In the semiconductor device 10, a semiconductor element 3 is provided on a lead frame 1 via a cured paste composition 2. Electrodes 4 on the semiconductor element 3 are connected to leads 5 of the lead frame 1 by bonding wires 6, and these are further encapsulated with a cured encapsulating resin composition 7.

[0059] Here, the semiconductor element may be any known semiconductor element, such as a transistor or a diode. Further examples of the semiconductor element include wide bandgap semiconductor elements such as SiC and GaN, and light-emitting elements such as LEDs. The type of light-emitting element is not particularly limited. Examples include light-emitting layers formed on a substrate by MOBVC or other methods using nitride semiconductors such as InN, AlN, GaN, InGaN, AlGaN, and InGaAlN. Examples of the element support member include support members made of materials such as copper, silver-plated copper, PPF (pre-plating lead frame), glass epoxy, and ceramics.

[0060] The paste composition of the present disclosure provides a semiconductor device with excellent connection reliability against temperature cycles after mounting. Furthermore, the paste composition has the advantage of providing a long life with little change in output over time even when driven for a long period of time, due to the low oxidation of copper particles and stable sintering.

[0061] The electrical and electronic components of the present disclosure are obtained by bonding a heat-generating component to a heat-dissipating component using the paste composition. That is, the paste composition is used as a material for bonding a heat-dissipating component, and the heat-generating component and the heat-dissipating component are bonded and fixed together via the paste composition.

[0062] An example of an electrical component according to the present disclosure is shown in Fig. 2. Electrical component 20 has heat-generating member 13 provided on heat-dissipating member 11 with cured paste composition 12 interposed therebetween. The heat-generating component may be the semiconductor element or a component having the semiconductor element, or may be any other heat-generating component. Examples of heat-generating components other than semiconductor elements include optical pickups and power transistors. Examples of heat-dissipating components include heat sinks and heat spreaders.

[0063] In this way, by joining a heat-generating component to a heat-dissipating component using the paste composition, it becomes possible for the heat-dissipating component to efficiently dissipate heat generated in the heat-generating component to the outside, thereby reducing the temperature rise of the heat-generating component. The heat-generating component and the heat-dissipating component may be joined directly via the paste composition, or may be joined indirectly by sandwiching another component with high thermal conductivity therebetween. [Example]

[0064] The present disclosure will now be described in detail with reference to examples, but the present disclosure is not limited to these examples in any way.

[0065] (Production of copper particles) [Example 1] As a copper compound, cuprous oxide (manufactured by Furukawa Chemicals Co., Ltd., product name: FRC-10A, crystallite diameter S in Miller index (111) Cu2О10 mmol of (111):625 nm), 20 mmol of dodecylamine (Farmin 20D, manufactured by Kao Corporation), 40 mmol of decanoic acid (capric acid, manufactured by New Japan Chemical Co., Ltd.), 10 mmol of hydrazine monohydrate (trade name: Hydrazine Monohydrate, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 10 mL of 1-propanol (1-propanol, manufactured by Tokyo Chemical Industry Co., Ltd.) as an organic solvent were placed in a 50 mL sample bottle and mixed at 25°C for 15 minutes in an aluminum block heated stirrer. The temperature was then changed to 100°C and the mixture was mixed for 180 minutes. The resulting reaction solution was centrifuged at 10,000 rpm at 25°C for 15 minutes, and the supernatant was discarded. Ethanol (Tokyo Chemical Industry Co., Ltd., product name: Ethanol) was added as a washing solvent, and the mixture was stirred in a vacuum planetary centrifugal mixer at 10,000 rpm and 25°C for 10 minutes, followed by centrifugation at 10,000 rpm and 25°C for 15 minutes, after which the supernatant was discarded. This procedure was repeated four times. The same procedure was repeated twice more, except that ethanol was replaced with diethylene glycol (Tokyo Chemical Industry Co., Ltd.), to obtain a copper cake (solid material). The obtained copper cake was analyzed as described below, and found to have a thickness of 31 nm, a major axis of 60 nm, and a crystallite diameter S of 100 nm in terms of copper Miller index (220). Cu (220) 38 nm, crystallite diameter S at Miller index (111) of copper Cu (111) 55 nm copper particles.

[0066] [Example 2] A copper cake was obtained in the same manner as in Example 1, except that aminoethoxyethanol (Tokyo Chemical Industry Co., Ltd., trade name: 2-aminoethoxy-2-ethanol) was used as the amine. [Example 3] As a copper compound, cuprous oxide (manufactured by Furukawa Chemicals Co., Ltd., product name: FRC-D30, crystallite diameter S in Miller index (111) Cu2О A copper cake was obtained in the same manner as in Example 2, except that a copper oxide (111):878 nm) was used. [Example 4] A copper cake was obtained in the same manner as in Example 3, except that octanoic acid (manufactured by Kao Corporation, trade name: Lunac 8-98) was used as the carboxylic acid. [Example 5] A copper cake was obtained by the same procedure as in Example 4, except that a 0.5% by mass ethanol solution of phosphate ester (manufactured by BYK Japan Co., Ltd., product name: DISPERBYK145) was used as the washing solvent to obtain copper particles coated with phosphate ester.

[0067] [Comparative Example 1] As a copper compound, cuprous oxide (manufactured by Furukawa Chemicals Co., Ltd., trade name: R, crystallite diameter S in Miller index (111) Cu2О 10 mmol of (111):657 nm), 20 mmol of dodecylamine (Kao Corporation, Farmin 20D), 40 mmol of octanoic acid (Kao Corporation, trade name: Lunac 8-98), and 10 mL of 1-propanol (Tokyo Chemical Industry Co., Ltd., 1-propanol) as an organic solvent were placed in a 50 mL sample bottle and heated to 100 °C in an aluminum block heater / stirrer. Then, 10 mmol of hydrazine monohydrate (Fujifilm Wako Pure Chemical Industries, Ltd., trade name: Hydrazine Monohydrate) was added and mixed at 100 °C for 180 minutes. The resulting reaction solution was centrifuged at 10,000 rpm at 25 °C for 15 minutes, and the supernatant was discarded. Ethanol (Tokyo Chemical Industry Co., Ltd., product name: Ethanol) was added as a washing solvent, and the mixture was stirred in a vacuum planetary centrifugal mixer at 10,000 rpm and 25°C for 10 minutes, followed by centrifugation at 10,000 rpm and 25°C for 15 minutes, after which the supernatant was discarded. This procedure was repeated four times. The same procedure was repeated twice more, except that ethanol was replaced with diethylene glycol (Tokyo Chemical Industry Co., Ltd.), to obtain a copper cake (solid material).

[0068] Comparative Example 2 The carboxylic acid used was acetic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., trade name: acetic acid), and the copper compound used was cuprous oxide (manufactured by Furukawa Chemicals Co., Ltd., trade name: R, crystallite diameter S in Miller index (111)). Cu2ОA copper cake was obtained in the same manner as in Example 2, except that a copper oxide (111):657 nm) was used.

[0069] (Evaluation method) <Evaluation method for copper particles> [Ratio of crystallite diameter] The copper cake obtained in each example and comparative example was applied to a glass plate to a thickness of 200 μm, and the crystallite diameter S was determined by the Scherrer equation for the Miller index (111) and (220) plane peaks using a focusing method with CuKα radiation as the radiation source using an X-ray diffractometer (product name: SmartLab SE, manufactured by Rigaku Corporation). Cu (220) and crystallite diameter S Cu (111) was calculated. Crystallite diameter S Cu The value of (111) is the crystallite diameter S Cu The crystallite size ratio was obtained by dividing by the (220) value. The results are shown in Table 1. The fitting function used was a divided pseudo-Voigt function, the width was FWHD, and the Scherrer constant was 0.94.

[0070] [Thickness and major diameter] The copper cakes produced in each Example and Comparative Example were applied to a brass sample stage with carbon tape attached and dried at 90°C for 3 hours in a nitrogen atmosphere to obtain copper particles. Images were then taken using a scanning electron microscope (JEOL Ltd., trade name: JSM-F100; SEM) at an accelerating voltage of 15 kV and 100,000x magnification. The thickness and major axis were calculated as the median of the measured length values ​​of at least 200 copper particles. Figures 3 to 5 are scanning electron microscope images of the copper cakes of Example 3, Example 5, and Comparative Example 1, respectively. The median of the measured thickness of copper particles is the thickness of the (n / 2)th particle counting from the smallest particle when the thickness of n copper particles is measured. n The thickness of the {(n / 2)+1}th particle counting from the smallest particle is d n+1 Then, {(d n +d n+1 ) / 2}. Similarly, the median of the measured values ​​of the long diameter of copper particles is the value obtained by measuring the long diameter of n copper particles and counting from the smallest particle, that is, the long diameter of the (n / 2)th particle. n Let the long diameter of the {(n / 2)+1}th particle counting from the smallest particle be L n+1 Then, {(L n +L n+1 ) / 2}. If n is an odd number and the first decimal place of (n / 2) is 5, the decimal point shall be rounded up.

[0071] Coverage In each example and comparative example, solid matter was collected before the washing operation with diethylene glycol, and the temperature was raised from 30°C to 450°C at a rate of 20°C / min using a thermogravimetric analyzer (manufactured by Hitachi High-Tech Corporation, product name: STA7200RV). The weight loss rates at 150°C and 450°C were calculated and used as the coverage ratio.

[0072] [Oxidation level] The copper cake obtained in each Example and Comparative Example was applied to a glass plate to a thickness of 200 μm. An X-ray diffractometer (product name: SmartLab SE, manufactured by Rigaku Corporation) was used to measure the copper content by the reference intensity ratio method based on the peak area ratio of the Miller index (111) for copper to the Miller index (111) for cuprous oxide, using a focusing method with CuKα radiation as the radiation source. The fitting function used was a split pseudo-Voigt function.

[0073] [viscosity] The viscosity of the copper paste obtained in each example and comparative example was measured at 0.5 rpm using a cone-plate viscometer (product name: DVNXHBCBG, manufactured by Brookfield) and recorded as the viscosity value. The cone-plate used was CPA-51Z.

[0074] <Reliability test evaluation method> [Test piece with sealing resin] The copper cake obtained in each of the Examples and Comparative Examples was diluted with diethylene glycol to a nonvolatile content of 80 mass % to obtain a copper paste. A 3mm x 3mm x 200µm silicon chip (surface treated with Ti-Au) was bonded to a v-QFP frame (surface treated with Ni-Pd-Au, 4mm x 4mm die pad) using the copper paste, and sintered at 200°C for 60 minutes in a nitrogen (3% by volume hydrogen) atmosphere.Then, the mold was cured with a sealing resin (Kyocera Corporation, product name KE-G3000D).

[0075] [Test piece without sealing resin] The copper cake obtained in each of the Examples and Comparative Examples was diluted with diethylene glycol to a nonvolatile content of 80 mass % to obtain a copper paste (paste composition). A 3mm x 3mm x 200μm AlN piece (surface treated with Ti-Pd-Au) was bonded to a copper plate (surface treated with Ni-Pd-Au) using the copper paste, and sintered at 200°C for 60 minutes in a nitrogen (3% hydrogen by volume) atmosphere.

[0076] [Joining strength] The die shear strength of the test piece without the sealing resin was measured at room temperature (25° C.) using DAGE 4000Plus (product name, manufactured by Nordson Corporation). The results are shown in Table 1. [Density] The specimens without the sealing resin were embedded in epoxy resin, and then cross-sections were processed and observed with an FE-SEM (manufactured by JEOL Ltd., product name: JSM-F100). The area ratio of the copper layer was calculated from the binarized image of the bonding layer edge. The results are shown in Table 1.

[0077] [Reliability test (heat cycle test)] A thermal cycle test was conducted on the test specimens without encapsulating resin and the test specimens with encapsulating resin. The test conditions were -40°C / 30 minutes to 120°C / 30 minutes, with one cycle consisting of 2000 cycles. The rate of change in the thermal resistance of the junction obtained from a transient thermal resistance measuring device (manufactured by Siemens AG, product name: T3Ster) before and after the thermal cycle test was calculated. The results are shown in Table 1. Note that an abnormality is defined as a rate of change exceeding 10%.

[0078] [Table 1]

[0079] The copper particles of Examples 1 to 5 have a ratio S Cu (111) / S Cu Since (220) is greater than 1.4 or less than 1.2, the bonding strength is excellent, the density is high, and the reliability is high. In contrast, the copper particles of Comparative Example 1 were not initially stirred at 25°C for 15 minutes, and therefore the critical saturation state could not be established at a relatively low temperature, and the by-production of granular seed crystals, which tend to occur at high temperatures, increased, and plate-shaped seed crystals could not be selectively produced. Cu (111) / S Cu (220) was in the range of 1.2 to 1.4. Therefore, the bonding strength, density, and reliability were all inferior to those of Examples 1 to 5. In addition, the copper particles of Comparative Example 2 were prepared using a monocarboxylic acid having less than 6 carbon atoms, and therefore were unable to strongly stabilize the copper atoms produced by reduction, and were unable to reduce the seed crystal production rate and particle growth rate. Cu (111) / S Cu (220) was in the range of 1.2 to 1.4. Therefore, the bonding strength, density, and reliability were all inferior to those of Examples 1 to 5. As shown in FIG. 3, the copper cake according to Example 3 has a high proportion of upright plate-like copper particles, so the ratio S Cu (111) / S Cu As shown in FIG. 4, the copper cake according to Example 5 has a high proportion of plate-like copper particles in a lying state, and therefore the ratio S Cu (111) / S Cu On the other hand, as shown in FIG. 5, the copper cake according to Comparative Example 1 has a high ratio of spherical copper particles, and therefore the ratio S Cu (111) / S Cu (220) was in the range of 1.2 to 1.4. [Explanation of symbols]

[0080] 10 Semiconductor devices 20 Electrical Components 1 lead frame 2, 12 Hardened paste composition 3. Semiconductor elements 4 electrodes 5 Lead section 6 Bonding Wire 7. Cured product of encapsulating resin composition 11 Heat dissipation material 13 Heat generating components

Claims

1. Copper particles characterized in that in X-ray diffraction, the ratio SCu(111) / SCu(220) of the crystallite diameter SCu(111) in Miller index (111) of copper to the crystallite diameter SCu(220) in Miller index (220) of copper satisfies the following formula (1) or the following formula (2): SCu(111) / SCu(220)>1.4...(1) SCu(111) / SCu(220)<1.2...(2)

2. 2. The copper particles according to claim 1, wherein the crystallite size SCu(111) is 60 nm or less.

3. 3. The copper particles according to claim 1, wherein the thickness is 5 to 50 nm and the major axis is 30 to 300 nm.

4. 3. The copper particle according to claim 1, having a core made of copper and a shell formed from at least one of an amine compound and a carboxylic acid.

5. 3. The copper particle according to claim 1, having a core made of copper and a shell formed from a phosphoric acid derivative.

6. 3. The method for producing copper particles according to claim 1, wherein cuprous oxide having a crystallite diameter SCuO(111) of 70 nm or more in X-ray diffraction according to Miller indices (111) is reduced in the presence of a shape stabilizer.

7. The method for producing copper particles described in claim 6, characterized in that the shape stabilizer is a neutralized salt of an alkanolamine having 4 or more carbon atoms and a fatty acid having 6 or more carbon atoms.

8. A paste composition containing the copper particles according to claim 1 or 2.

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