Paste composition, semiconductor device, electrical component and electronic component

Abstract

A paste composition which contains first copper particles, and which is characterized in that: each one of the first copper particles is obtained by covering a copper particle, which serves as the base material, with at least one compound that is selected from among (a) an amine compound and (b) a carboxylic acid amine salt; and the total content of the amine compound (a) and the carboxylic acid amine salt (b) detected in the paste composition is less than 1% by mass of the entire paste composition.

Description

[Technical Field]

[0001] The present disclosure relates to 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] In some cases, semiconductor elements are 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 using 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] [1] The paste composition of the present disclosure is a paste composition containing first copper particles, The first copper particles are composed of copper particles as a base material coated with at least one compound selected from (a) an amine compound and (b) an amine carboxylic acid salt, and the total content of the (a) amine compound and the (b) amine carboxylic acid salt detected in the paste composition is less than 1 mass% of the entire paste composition. [2] The semiconductor device of the present disclosure is bonded using the paste composition described in [1] above. [3] The electrical component of the present disclosure is bonded using the paste composition described in [1] above. [4] The electronic component of the present disclosure is bonded using the paste composition described in [1] 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. DETAILED DESCRIPTION OF THE INVENTION

[0010] Compared to solder paste, copper paste using sinterable copper nanoparticles requires a longer curing time due to the bonding principle, which means that there is a waiting time after mounting the adherend before placing it in the curing oven. During this waiting time, oxidation of the copper nanoparticle surface can progress, resulting in a decrease in bonding reliability.

[0011] The present disclosure provides a paste composition that is oxidation-resistant and maintains high sinterability and bondability without being affected by the time of exposure to the atmosphere before curing, as well as semiconductor devices, electrical components, and electronic components that are highly reliable when using the paste composition.

[0012] Hereinafter, the present disclosure will be described in detail with reference to an embodiment.

[0013] <Paste composition> The paste composition of the present embodiment contains first copper particles in which copper particles serving as a base material are coated with at least one compound selected from (a) an amine compound and (b) an amine carboxylic acid salt, and the total content of the (a) amine compound and the (b) amine carboxylic acid salt detected in the paste composition is less than 1 mass% of the entire paste composition.

[0014] If the total content of the (a) amine compound and the (b) carboxylic acid amine salt detected in the paste composition of this embodiment is 1% by mass or more of the total paste composition, the paste composition will have low sinterability and bondability, and the sinterability and bondability may further decrease after exposure to the atmosphere. From this perspective, the total content of the (a) amine compound and the (b) carboxylic acid amine salt may be less than 0.8% by mass, less than 0.5% by mass, or less than 0.3% by mass. The (a) amine compound and the (b) carboxylic acid amine salt are blended during the synthesis of the first copper particles. They coat the surfaces of the first copper particles, but may not completely coat them and remain free in the paste composition. The amine compound may also be added as a reducing agent. If the total content of the (a) amine compound and the (b) carboxylic acid amine salt in the paste composition is equal to or greater than the above-mentioned value, the (a) amine compound and the (b) carboxylic acid amine salt will be unevenly distributed in the paste composition during curing of the paste composition, reducing the sinterability of the first copper particles. This reduces the stability of the first copper particles after exposure to the atmosphere. The total content of the (a) amine compound and the (b) carboxylic acid amine salt in the paste composition can be measured by a chromatography method typified by gas chromatography or liquid chromatography, or a method combining a chromatography method with mass spectrometry. Specifically, it can be measured by the method described in the Examples.

[0015] [First copper particles] The first copper particles used in this embodiment are copper particles that serve as a base material and are coated with at least one compound selected from (a) an amine compound and (b) a carboxylic acid amine salt. The first copper particles may be coated with (b) a carboxylic acid amine salt in order to uniform the sintering rate and degree between the inside of the bonding layer and the fillet portion and improve bonding characteristics.

[0016] The copper particles, which are the base material of the first copper particles, are derived from a copper compound. The copper compound is not particularly limited as long as it contains copper atoms. Examples of the copper compound include copper carboxylate, copper oxide, copper hydroxide, and copper nitride. From the viewpoint of uniformity during the reaction, the copper compound may also be copper carboxylate. These compounds may be used alone or in combination of two or more.

[0017] 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.

[0018] The carboxylate copper may be commercially available or may be synthesized.

[0019] 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.

[0020] Examples of copper oxide include copper(II) oxide and copper(I) oxide, and copper(I) oxide may be used from the viewpoint of productivity. Examples of copper hydroxide include copper(II) hydroxide and copper(I) hydroxide. These may be used alone or in combination of two or more.

[0021] At least one compound selected from the (a) amine compound and the (b) carboxylic acid amine salt may cover part or all of the surface of the copper particle that is the base material of the first copper particle. The mass coverage of the first copper particles with at least one compound selected from (a) an amine compound and (b) an amine carboxylate covering the surface of the base copper particles may be 0.05% or more, 0.1% or more, 0.2% or more, or 0.5% or more, from the viewpoint of sinterability and bondability. The upper limit of the mass coverage may be 10%, 7%, 5%, or 3%. When the mass coverage is 10% or less, the content of (a) an amine compound and (b) an amine carboxylate detected in a paste composition containing the first copper particles is easily reduced to less than 1% by mass of the entire paste composition. In the present disclosure, the mass coverage is defined as the mass reduction rate calculated from the mass of the first copper particles before heating and the mass of the first copper particles after heating using an infrared lamp heating device, etc. Specifically, the mass coverage can be measured by the method described in the Examples.

[0022] Examples of the amine compound (a) used in this embodiment include monoamines having one amino group and diamines having two amino groups. Examples of the monoamines include dipropylamine, butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, 3-aminopropyltriethoxysilane, dodecylamine, oleylamine, monoethanolamine, 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, and 1,8-diaminooctane.

[0023] The (b) carboxylic acid amine salt used in this embodiment can be obtained from a carboxylic acid compound and an amine compound, and a commercially available product may be used. A product obtained by pre-synthesis may also be used. Alternatively, the carboxylic acid compound and the amine compound may be separately added to a reaction vessel during the production process of the first copper particles, and the salt may be generated in situ.

[0024] A carboxylic acid amine salt is produced by mixing a carboxylic acid compound and an amine compound in an organic solvent in equal amounts of functional groups under relatively mild temperature conditions of room temperature (25° C.) to about 100° C. The salt may be extracted from the reaction solution containing the product by distillation or recrystallization.

[0025] The carboxylic acid compound constituting the carboxylic acid amine salt is not particularly limited as long as it is a compound having a carboxy group, and examples thereof include monocarboxylic acids, dicarboxylic acids, aromatic carboxylic acids, and hydroxy acids. From the viewpoint of sinterability, the carboxylic acid compound may be monocarboxylic acids or dicarboxylic acids. These may be used alone or in combination of two or more.

[0026] From the viewpoint of sinterability, the carboxylic acid compound constituting the carboxylic acid amine salt may have a thermal decomposition temperature of 200° C. or lower, 190° C. or lower, or 180° C. or lower.

[0027] Furthermore, when the carboxylic acid compound constituting the carboxylic acid amine salt has a boiling point lower than the thermal decomposition temperature, the boiling point may be 280°C or lower, 260°C or lower, or 240°C or lower from the viewpoint of sinterability.

[0028] Among the carboxylic acid compounds constituting the carboxylic acid amine salt, examples of monocarboxylic acids include 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, and isostearic acid. These may be used alone or in combination of two or more. From the viewpoint of sinterability, the monocarboxylic acid may be formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, or capric acid, or may be valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, or capric acid.

[0029] Among the carboxylic acid compounds constituting the carboxylic acid amine salt, examples of dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, and diglycolic acid. These may be used alone or in combination of two or more. From the viewpoint of sinterability, the dicarboxylic acid may be oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, or diglycolic acid, or may be oxalic acid, malonic acid, succinic acid, or diglycolic acid.

[0030] Among the carboxylic acid compounds constituting the carboxylic acid amine salt, examples of aromatic carboxylic acids include benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, and gallic acid. These may be used alone or in combination of two or more. From the viewpoint of sinterability, the aromatic carboxylic acid may be benzoic acid.

[0031] Among the carboxylic acid compounds constituting the carboxylic acid amine salt, examples of hydroxy acids include glycolic acid, lactic acid, tartronic acid, malic acid, glyceric acid, hydroxybutyric acid, tartaric acid, citric acid, and isocitric acid. These may be used alone or in combination of two or more. From the viewpoint of sinterability, the hydroxy acid may be glycolic acid, lactic acid, or malic acid.

[0032] The amine compound constituting the carboxylic acid amine salt is not particularly limited as long as it is a compound having an amino group, and examples thereof include alkyl monoamines, alkyl diamines, alkanolamines, etc. These may be used alone or in combination of two or more. The amine compound may be an alkyl monoamine or an alkanolamine from the viewpoint of improving sinterability.

[0033] Among the amine compounds constituting the carboxylic acid amine salt, alkyl monoamines include methylamine, ethylamine, propylamine, butylamine, hexylamine, octylamine, decylamine, and dodecylamine. These may be used alone or in combination of two or more. The alkyl monoamine may be hexylamine, octylamine, or decylamine from the viewpoint of improving sinterability.

[0034] Among the amine compounds constituting the carboxylic acid amine salt, alkyl diamines include 1,1-methanediamine, 1,2-ethanediamine, 1,3-propanediamine, 1,4-butanediamine, 1,6-hexanediamine, and 1,8-octanediamine. These may be used alone or in combination of two or more. The alkyl diamine may be 1,4-butanediamine or 1,6-hexanediamine from the viewpoint of improving sinterability.

[0035] Among the amine compounds constituting the carboxylic acid amine salt, examples of alkanolamines include monoethanolamine, monopropanolamine, monobutanolamine, 2-(2-aminoethylamino)ethanol, 2-(2-aminoethoxy)ethanol, 1-amino-2-propanol, 2-amino-1-propanol, and 3-amino-1,2-propanediol. These may be used alone or in combination of two or more. From the viewpoint of improving sinterability, the alkanolamine may be monoethanolamine, monopropanolamine, monobutanolamine, 1-amino-2-propanol, or 2-amino-1-propanol.

[0036] From the viewpoint of reducing oxidation and increasing the density of the bonding layer, the first copper particles may have a median diameter (D50) of 50 nm to 500 nm, 55 nm to 400 nm, 60 nm to 300 nm, or 60 nm to 200 nm. The smaller the median diameter, the larger the specific surface area and the more susceptible to oxidation. The median diameter of the first copper particles is calculated as the median of the equivalent area circle diameters of at least 2,000 copper particles extracted from an image taken with a scanning electron microscope (e.g., JEOL Ltd., trade name: JSM-F100; SEM) at an accelerating voltage of 15 kV and a magnification of 50,000. Specifically, it can be measured by the method described in the Examples.

[0037] The first copper particles may have a crystallite diameter of 30 nm or more and 150 nm or less, or may be greater than 50 nm and 120 nm or less, or greater than 50 nm and 100 nm or less. By setting the crystallite diameter to 30 nm or more, the particles are less likely to be oxidized by exposure to the atmosphere and have good sintering stability, while by setting the crystallite diameter to 150 nm or less, low-temperature sintering properties can be ensured. In the present disclosure, the crystallite size is calculated by the Scherrer method using the Cu(111) peak obtained by X-ray diffraction (XRD) measurement. Specifically, it can be measured by the method described in the Examples.

[0038] The first copper particles may have an oxidation degree of 0.01% or more and 3.0% 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 susceptible to oxidation due to exposure to the atmosphere and have good sintering stability, while by setting the oxidation degree to 3.0% or less, the particles are more sinterable. The degree of oxidation can be determined, for example, by analyzing data obtained using an X-ray diffractometer by the Rietveld method. Specifically, it can be measured by the method described in the Examples.

[0039] The content of the first copper particles may be 10% by mass or more and 90% by mass or less, 10% by mass or more and 60% by mass or less, or 10% by mass or more and 40% by mass or less, based on the total amount of the paste composition.

[0040] [First copper particle manufacturing method] The first method for producing copper particles includes, for example, a method in which a copper compound is reduced with a reducing compound in the presence of at least one compound selected from (a) an amine compound and (b) a carboxylic acid amine salt. The copper compound, (a) the amine compound, and (b) the carboxylic acid amine salt can be the same as those described above in the section [First copper particles].

[0041] 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.

[0042] The copper compound, at least one compound selected from (a) the amine compound and (b) the carboxylic acid amine salt, and the reducing compound may be mixed in an organic solvent. The organic solvent is not particularly limited as long as it can be used as a reaction solvent that does not inhibit the properties of the complex formed from the mixture obtained by mixing the above-mentioned raw materials. In particular, an alcohol that is compatible with the reducing compound may be used.

[0043] 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.

[0044] The order of mixing the compounds is not particularly limited, and the compounds may be mixed in any order. For example, the copper compound and at least one compound selected from (a) the amine compound and (b) the carboxylic acid amine salt may be mixed and mixed at a temperature of 0°C to 110°C for about 5 to 30 minutes, and then the reducing compound may be added and mixed.

[0045] In the mixing, the amounts of the copper compound, the at least one compound selected from the (a) amine compound and the (b) carboxylic acid amine salt, and the reducing compound may be such that, relative to 1 mol of the copper compound, the amount of the at least one compound selected from the (a) amine compound and the (b) carboxylic acid amine salt is 0.5 mol to 10 mol and the amount of the reducing compound is 0.5 mol to 5 mol, or the amount of the at least one compound selected from the (a) amine compound and the (b) carboxylic acid amine salt may be 1 mol to 5 mol and the amount of the reducing compound is 0.8 mol to 3 mol. The organic solvent may be used in an amount that allows each component to react sufficiently, for example, about 10 to 1000 volumes per 100 volumes of at least one compound selected from (a) the amine compound and (b) the carboxylic acid amine salt.

[0046] Next, the mixture obtained by mixing is heated sufficiently to promote the reduction reaction of the copper compound, which can eliminate unreacted copper compound and allow metallic copper to be favorably precipitated and grown to form copper particles. The heating temperature of the mixture may be 25°C or higher and 120°C or lower, 50°C or higher and 120°C or lower, or 80°C or higher and 120°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 first copper particles can be easily controlled within the above ranges.

[0047] The solid matter precipitated by the heating may be 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 dried under reduced pressure to obtain first copper particles. The washing can be appropriately adjusted by changing the number of washings, the amount of organic solvent used, the washing time, etc., and the oxidation degree of the resulting first copper particles may be adjusted to fall within the aforementioned range. 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% or more by volume, 100% or more by volume, or 1000% or more by volume relative to the volume of the first 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.

[0048] Here, the washing reduces the content of impurities such as (a) amine compounds and (b) carboxylic acid amine salts in the paste composition containing the first copper particles, but the degree of oxidation of the first copper particles increases with the number of washings. Therefore, it is necessary to appropriately adjust the washing to control the total content of (a) amine compounds and (b) carboxylic acid amine salts in the paste composition to less than the above value and to control the degree of oxidation of the first copper particles to within the above range.

[0049] [Second copper particles] From the viewpoint of storage stability, the paste composition of this embodiment may further contain second copper particles having a particle size larger than that of the first copper particles. The second copper particles may have a median diameter (D50) of 1 μm or more and 8 μm or less, or 1.5 μm or more and 7 μm or less, or 2 μm or more and 6 μm or less. When the median diameter is within the above range, internal shrinkage during sintering is suppressed, and the sinterability with the bonding interface (dissimilar metals) is improved, thereby improving bonding strength.

[0050] The second copper particles may have a crystallite diameter of 70 nm to 140 nm, 75 nm to 130 nm, or 80 nm to 120 nm. When the crystallite diameter is within the above range, internal shrinkage during sintering is reduced, and the sinterability with the bonding interface (dissimilar metals) is improved, resulting in improved bonding strength. The second copper particles may be used alone or in combination of two or more types. The median diameter of the second copper particles is based on the number of particles, and can be measured using a laser diffraction / scattering particle size distribution measuring device or the like.

[0051] The shape of the second copper particles is not particularly limited, and examples thereof include spherical, plate-like, flake-like, scale-like, dendritic, rod-like, and wire-like shapes.

[0052] The second copper particles may be commercially available products, such as 1200Y (manufactured by Mitsui Mining & Smelting Co., Ltd., median diameter: 2.1 μm, crystallite diameter: 102 nm) and 1300Y (manufactured by Mitsui Mining & Smelting Co., Ltd., median diameter: 3.9 μm, crystallite diameter: 102 nm).

[0053] The content of the second copper particles may be 10% by mass or more and 90% by mass or less, 10% by mass or more and 70% by mass or less, or 20% by mass or more and 60% by mass or less, based on the total amount of the paste composition.

[0054] [Phosphate ester] From the viewpoint of storage stability, the paste composition of this embodiment may further contain a phosphate ester. The phosphate ester has the effect of removing an oxide film formed on the surface of the first copper particles due to exposure to the atmosphere during heating, and thus the paste composition containing the phosphate ester improves the sinterability of the paste composition. Furthermore, if the total content of the (a) amine compound and the (b) carboxylic acid amine salt contained in the paste composition of this embodiment is less than the above-mentioned value, the effect of the phosphate ester is not reduced.

[0055] 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 the above values, changes in the oxidation degree of the first 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.

[0056] The phosphate ester may have a ratio of the acid value to the amine value [acid value / amine value] of 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, a change in the oxidation degree of the first copper particles can be reduced.

[0057] 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.

[0058] When the paste composition of the present embodiment contains a phosphate ester, the content thereof may be 0.01 mass % or more and 2.0 mass % or less, 0.1 mass % or more and 1.8 mass % or less, or 0.5 mass % or more and 1.5 mass % or less, relative to the total amount of the paste composition.

[0059] The paste composition of this embodiment may contain an organic solvent. The organic solvent may be an alcohol, for example, an aliphatic polyhydric alcohol. Examples of the aliphatic polyhydric alcohol include glycols such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, glycerin, and polyethylene glycol. These organic solvents may be used alone or in combination of two or more.

[0060] When the paste composition of this embodiment 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 the first copper particles. When the content is 10 parts by mass or more, the viscosity does not become too high, and workability can be improved. 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.

[0061] In addition to the above components, the paste composition of this embodiment 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.

[0062] [Method for producing paste composition] The paste composition of this embodiment can be prepared by thoroughly mixing the above-mentioned first 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.

[0063] The viscosity of the paste composition of this embodiment 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 this embodiment 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.

[0064] The paste composition of the present embodiment obtained in this manner has excellent 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.

[0065] <Semiconductor devices, electrical components and electronic components> The semiconductor device, electrical component, and electronic component of this embodiment are bonded using the paste composition described above, and therefore have high reliability.

[0066] The semiconductor device of this embodiment is formed by bonding a semiconductor element to a substrate that serves 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.

[0067] 1 shows an example of a semiconductor device according to this embodiment. 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 then sealed with a cured encapsulating resin composition 7.

[0068] 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, and examples include those in which a nitride semiconductor such as InN, AlN, GaN, InGaN, AlGaN, or InGaAlN is formed as a light-emitting layer on a substrate by MOBVC or the like. 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.

[0069] By using the paste composition of this embodiment, a semiconductor device can be obtained that has good connection reliability against temperature cycles after mounting. In addition, there is an advantage that the copper particles are less oxidized and the sintering property is stable, so that there is little change in output over time even when driven for a long time, resulting in a long life.

[0070] The electrical and electronic components of this embodiment are obtained by joining a heat-generating component to a heat-dissipating component using the paste composition. That is, the paste composition is used as a material for joining a heat-dissipating component, and the heat-dissipating component and the heat-generating component are joined and fixed together via the paste composition.

[0071] 2 shows an example of an electrical component according to this embodiment. 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.

[0072] 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]

[0073] 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.

[0074] (Synthesis of amine carboxylic acid salts) [Preparation Example 1] 40 mmol of nonanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: Nonanoic acid) and 40 mmol of hexylamine (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: Hexylamine) were placed in a 50 mL sample bottle, and the bottle was stirred and mixed in an aluminum block-type heated stirrer at 60°C for 15 minutes, and then cooled to room temperature (25°C) to obtain nonanoic acid hexylamine salt (yield: 10.3 g, 99.2%).

[0075] [Preparation Example 2] 40 mmol of octanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: octanoic acid) and 40 mmol of 2-amino-1-propanol (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: 2-amino-1-propanol) were placed in a 50 mL sample bottle, stirred and mixed in an aluminum block-type heated stirrer at 60°C for 15 minutes, and then cooled to room temperature (25°C) to obtain 2-aminopropanol octanoate (yield: 8.7 g, 98.7%).

[0076] [Preparation Example 3] 40 mmol of decanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: decanoic acid) and 40 mmol of octylamine (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: n-octylamine) were placed in a 50 mL sample bottle, and the mixture was stirred and mixed in an aluminum block-type heated stirrer at 60°C for 15 minutes, and then cooled to room temperature (25°C) to obtain decanoic acid octylamine salt (yield: 12.01 g, 99.6%).

[0077] (Production of first copper particles) [Synthesis Example 1] 20 mmol of copper(II) acetate monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: Copper(II) Acetate Monohydrate) as a copper compound, 40 mmol of the hexylamine nonanoate salt obtained in Preparation Example 1, and 3 mL of 1-propanol (manufactured by Tokyo Chemical Industry Co., Ltd.) as an organic solvent were placed in a 50 mL sample bottle and mixed in an aluminum block heated stirrer at 90°C for 5 minutes to produce a copper precursor solution. After cooling the copper precursor solution to room temperature (25°C), a solution prepared by dissolving 20 mmol of hydrazine monohydrate (manufactured by Fujifilm Wako Pure Chemical Industries Co., Ltd., trade name: Hydrazine Monohydrate) as a reducing compound in 3 mL of 1-propanol was added to the copper precursor solution in the sample bottle and stirred for 5 minutes.

[0078] The mixture was again heated and stirred at 90°C for 1 hour using an aluminum block-type heating stirrer. After cooling to room temperature (25°C), it was centrifuged (5000 rpm, 5 minutes) to obtain a copper cake. 30 mL of ethanol (Kanto Chemical Co., Ltd., special grade) was added to the copper cake, and the mixture was redispersed by shaking and centrifuged (5000 rpm, 5 minutes). This process was repeated four times. The same procedure was then repeated twice, except that diethylene glycol (Tokyo Chemical Industry Co., Ltd.) was used instead of ethanol, to obtain a solid material. The resulting solid material was dried under reduced pressure to obtain powder-like copper particles 1 with a copper luster (yield: 0.31 g, 97.8%). Analysis of the resulting copper particles 1 revealed a degree of oxidation of 1.6%, a median diameter of 95 nm, a crystallite diameter of 51 nm, and a mass coverage of 1.9%.

[0079] [Synthesis Example 2] Copper particles 2 (yield: 0.30 g, yield: 94.6%) were obtained in the same manner as in Synthesis Example 1, except that copper(II) acetate monohydrate was changed to copper(I) oxide (manufactured by Furukawa Chemicals Corporation, trade name: R) and nonanoic acid hexylamine salt was changed to octanoic acid 2-aminopropanol salt obtained in Preparation Example 2. Analysis of the obtained copper particles 2 revealed that the oxidation degree was 0.9%, the median diameter was 105 nm, the crystallite diameter was 56 nm, and the mass coverage was 1.9%.

[0080] [Synthesis Example 3] Copper particles 3 (yield: 0.26 g, yield: 82.0%) were obtained by the same method as in Synthesis Example 1, except that the heating time at 90°C after adding hydrazine monohydrate was changed from 1 hour to 10 minutes. Analysis of the obtained copper particles 3 revealed that the oxidation degree was 1.9%, the median diameter was 80 nm, the crystallite diameter was 39 nm, and the mass coverage was 2.5%.

[0081] [Synthesis Example 4] Copper particles 4 (yield 0.31 g, 97.8%) were obtained in the same manner as in Synthesis Example 1, except that the organic solvent was changed to 1,3-propanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) and the heating conditions after adding hydrazine monohydrate were changed from 1 hour at 90°C to 3 hours at 110°C. Analysis of the obtained copper particles 4 revealed that the oxidation degree was 0.7%, the median diameter was 115 nm, the crystallite diameter was 90 nm, and the mass coverage was 2.2%.

[0082] [Synthesis Example 5] Copper particles 5 (yield: 0.31 g, yield: 97.8%) were obtained in the same manner as in Synthesis Example 1, except that nitrogen purging was performed during the shaking dispersion with ethanol and diethylene glycol. Analysis of the obtained copper particles 5 revealed that the oxidation degree was 0.02%, the median diameter was 95 nm, the crystallite diameter was 51 nm, and the mass coverage was 2.1%.

[0083] [Synthesis Example 6] Copper particles 6 (yield: 0.31 g, yield: 97.8%) were obtained in the same manner as in Synthesis Example 1, except that air bubbling was performed for 1 minute before the shaking dispersion with ethanol and diethylene glycol. Analysis of the obtained copper particles 6 revealed that the oxidation degree was 2.8%, the median diameter was 95 nm, the crystallite diameter was 51 nm, and the mass coverage was 2.2%.

[0084] [Synthesis Example 7] Copper particles 7 (yield: 0.31 g, yield: 97.8%) were obtained in the same manner as in Synthesis Example 1, except that washing with ethanol was performed twice. Analysis of the obtained copper particles 7 revealed that the oxidation degree was 1.1%, the median diameter was 95 nm, the crystallite diameter was 51 nm, and the mass coverage was 5.2%.

[0085] [Synthesis Example 8] Copper particles 8 (yield: 0.30 g, yield: 94.6%) were obtained in the same manner as in Synthesis Example 1, except that the hexylamine nonanoate was replaced with the octylamine decanoate obtained in Preparation Example 3. Analysis of the obtained copper particles 8 revealed that the oxidation degree was 7.5%, the median diameter was 30 nm, the crystallite diameter was 15 nm, and the mass coverage was 6.8%.

[0086] (Examples 1 to 8 and Comparative Examples 1 and 2) The components of the types and amounts shown in Table 1 were mixed and kneaded with a roll to obtain a paste composition.

[0087] Details of each component used in preparing the paste composition and listed in Table 1 are as follows. (First copper particles) Copper particles 1: Copper particles obtained in Synthesis Example 1 (oxidation degree 1.6%, median diameter 95 nm, crystallite diameter 51 nm) Copper particles 2: Copper particles obtained in Synthesis Example 2 (oxidation degree 0.9%, median diameter 105 nm, crystallite diameter 56 nm) Copper particles 3: Copper particles obtained in Synthesis Example 3 (oxidation degree 1.9%, median diameter 80 nm, crystallite diameter 39 nm) Copper particles 4: Copper particles obtained in Synthesis Example 4 (oxidation degree 0.7%, median diameter 115 nm, crystallite diameter 90 nm) Copper particles 5: Copper particles obtained in Synthesis Example 5 (oxidation degree 0.02%, median diameter 95 nm, crystallite diameter 51 nm) Copper particles 6: Copper particles obtained in Synthesis Example 6 (oxidation degree 2.8%, median diameter 95 nm, crystallite diameter 51 nm) Copper particles 7: Copper particles obtained in Synthesis Example 7 (oxidation degree 1.1%, median diameter 95 nm, crystallite diameter 51 nm) Copper particles 8: Copper particles obtained in Synthesis Example 8 (oxidation degree 7.5%, median diameter 30 nm, crystallite diameter 15 nm)

[0088] (Second copper particles) Copper particles 9: 1300Y (product name, manufactured by Mitsui Mining & Smelting Co., Ltd.; median diameter: 3.9 μm, crystallite diameter: 102 nm)

[0089] (phosphate ester) Phosphate ester 1: copolymer (product name: DIPERBYK (registered trademark)-102, manufactured by BYK-Chemie; acid value: 101 mg KOH / g) Phosphate ester 2: alkylol ammonium salt of copolymer (product name: DIPERBYK (registered trademark)-180, manufactured by BYK-Chemie; amine value: 94 mg KOH / g, acid value: 94 mg KOH / g) Phosphate ester 3: copolymer (product name: DIPERBYK (registered trademark)-111, manufactured by BYK-Chemie; acid value: 129 mg KOH / g)

[0090] (organic solvent) Diethylene glycol: Tokyo Chemical Industry Co., Ltd.

[0091] (Evaluation method) <Evaluation method for copper particles> [Crystallite diameter] The copper cake obtained in each synthesis example was applied to a glass plate to a thickness of 500 μm, and an X-ray diffraction analysis was performed using a focusing method with CuKα radiation as the radiation source using the Scherrer equation for the (111) plane peak. The Scherrer constant was 1.33.

[0092] [Median diameter] The copper cake obtained in each synthesis example was applied to a glass surface to a thickness of 500 μm, and the area of ​​2,000 copper particles was extracted from an image taken using a scanning electron microscope (manufactured by JEOL Ltd., product name: JSM-F100; SEM) at an accelerating voltage of 15 kV and a magnification of 50,000. The area of ​​2,000 copper particles was calculated as the median of the equivalent circle diameter.

[0093] [Oxidation level] The copper cake obtained in each synthesis example was applied to a glass surface to a thickness of 500 μm, and quantitative values ​​were obtained by analyzing data obtained by a focusing method using an X-ray diffractometer (product name: SmartLab SE, manufactured by Rigaku Corporation) with CuKα radiation as the radiation source using the Rietveld method.

[0094] [Mass coverage] The mass coverage of copper particles 1 to 8 was measured by the following procedure. After washing the copper particles with ethanol four times, the mass of the resulting copper cake was measured and designated as the mass of the copper particles before heating (M1). Next, the copper cake was heated to 600°C in a nitrogen atmosphere using an infrared lamp heating device (product name: MIRA-700AR, manufactured by Advance Riko Co., Ltd.), and the mass of the copper cake after heating was measured. This was designated as the mass of the copper particles after heating (M2), and the mass coverage was calculated using the following formula (1). Mass coverage (%)=(M1-M2) / M1×100 (1)

[0095] <Method for evaluating paste composition> [Viscosity (initial viscosity)] The values ​​were measured at 25°C and 5 rpm using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: VISCOMETER-TV22, applicable cone-plate rotor: 3° x R17.65).

[0096] [Storage stability (pot life)] The paste composition was left in a thermostatic chamber at 25°C, and the number of days until the viscosity increased to at least 0.7 times the initial viscosity was measured.

[0097] [Sinterability (coating)] The paste composition was applied to a glass substrate (thickness 1 mm) using screen printing to a thickness of 25 μm and cured at 200°C for 60 minutes. The volume resistivity (Ω·cm) of the resulting sintered film was measured using a Loresta GP (trade name, manufactured by Mitsubishi Chemical Analytical Co., Ltd.) by the four-point probe method. The lower the volume resistivity (Ω·cm), the better the sinterability.

[0098] [Sinterability after exposure to air] The paste composition was squeezed into a 500μm thick coating and stored in an incubator at 25℃ for 24 hours, then fired in a nitrogen (3% hydrogen) atmosphere at 200℃ for 1 hour, and the volume resistivity (Ω·cm) was measured using a Loresta GP (Mitsubishi Chemical Analytech) using the four-point probe method. The lower the volume resistivity (Ω·cm), the better the sintering properties.

[0099] [Total content of (a) amine compound and (b) carboxylic acid amine salt] The paste composition was separated into a liquid component and a solid component by centrifugation, and the liquid component was then quantitatively analyzed by an internal standard method using a gas chromatography mass spectrometer (product name: GCMS QP-2010, manufactured by Shimadzu Corporation).

[0100] <Method for evaluating semiconductor devices> [Preparation of bond strength test pieces] Silicon chips with a 2mm x 2mm gold sputtered layer on their bonding surfaces were mounted on pure copper frames and PPF (Ni-Pd / Au plated copper frames) using the paste composition, and cured at 200°C for 60 minutes in a nitrogen (3% hydrogen) atmosphere. Some of the chips were cured immediately after mounting, while others were cured after 24 hours of exposure to the atmosphere.

[0101] [Joining strength] For the specimens that were cured immediately after mounting, the die shear strength was measured at room temperature (25°C) using a DAGE 4000Plus (product name, manufactured by Nordson Corporation) after curing and after moisture absorption treatment (85°C, 85% relative humidity, 72 hours). In addition, for the specimens that were cured after 24 hours of exposure to the atmosphere, the die shear strength was measured in the same manner as above.

[0102] [Table 1]

[0103] It can be seen that Examples 1 to 8, in which the total content of (a) the amine compound and (b) the carboxylic acid amine salt detected in the paste composition was less than 1 mass %, all had high oxidation resistance and were able to maintain high sinterability and bondability without being affected by the time of exposure to the atmosphere before curing. [Explanation of symbols]

[0104] 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. A paste composition containing first copper particles, the first copper particles are obtained by coating copper particles as a base material with at least one compound selected from (a) an amine compound and (b) a carboxylic acid amine salt; a mass coverage of the at least one compound selected from (a) an amine compound and (b) a carboxylic acid amine salt covering the surfaces of the copper particles is 0.05% or more and 10% or less; A paste composition characterized in that the total content of the (a) amine compound and the (b) carboxylic acid amine salt obtained by an internal standard method is less than 1 mass% of the entire paste composition, after separating the paste composition into a liquid component and a solid component by centrifugation and analyzing the liquid component using a gas chromatography analyzer.

2. The paste composition according to claim 1 , wherein the first copper particles have a median diameter of 50 nm or more and 500 nm or less, and a crystallite diameter of 30 nm or more and 150 nm or less.

3. The paste composition according to claim 1 or 2, wherein the first copper particles have an oxidation degree of 0.01% or more and 3.0% or less.

4. 4. The paste composition according to claim 1, further comprising second copper particles having a median diameter of 1 μm or more and 8 μm or less and a crystallite diameter of 70 nm or more and 140 nm or less.

5. The paste composition according to any one of claims 1 to 4, further comprising a phosphoric acid ester.

6. 6. The paste composition according to claim 5, wherein the acid value and amine value of the phosphate ester are both 130 mg KOH / g or less.

7. 7. The paste composition according to claim 5, wherein the ratio of the acid value to the amine value of the phosphate ester (acid value / amine value) is 0 or more and 1.5 or less.

8. A semiconductor device bonded using the paste composition according to any one of claims 1 to 7.

9. An electrical part which is bonded using the paste composition according to any one of claims 1 to 7.

10. An electronic component bonded using the paste composition according to any one of claims 1 to 7.

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