WO2020105497A1

WO2020105497A1 - Production method for copper particles used in bonding , paste used in bonding, and semiconductor device and electric and electronic component

Info

Publication number: WO2020105497A1
Application number: PCT/JP2019/044166
Authority: WO
Inventors: 知直菊池; 勇哉似内
Original assignee: 京セラ株式会社
Priority date: 2018-11-20
Filing date: 2019-11-11
Publication date: 2020-05-28
Also published as: TW202026074A; JP2020084242A

Abstract

A production method for copper particles used in bonding comprising a step in which, by means of a liquid-phase reduction method, (A) a copper layer is further formed on a surface of a metal copper powder.

Description

Manufacturing method of copper particles for bonding, bonding paste, semiconductor device, and electric / electronic component

The present disclosure relates to a method for manufacturing copper particles for bonding, a bonding paste, and a semiconductor device and an electric / electronic component manufactured by using the bonding paste.

With the large capacity, high-speed processing and fine wiring of semiconductor products, attention has been paid to the processing of heat generated during the operation of semiconductor products. In particular, so-called thermal management, which dissipates heat from semiconductor products, is becoming increasingly important. For this reason, a method of attaching a heat spreader, a heat sink or other heat dissipation member to a semiconductor product is generally adopted, and a material (bonding paste) for adhering the heat dissipation member itself needs to have a higher thermal conductivity. ing.

Patent Document 1 discloses a copper paste containing copper composite particles in which copper hydride fine particles having secondary particles having an average particle diameter of 20 to 350 nm are attached to surfaces of metallic copper particles having an average particle diameter of primary particles of 1 to 20 μm. Is disclosed.

JP, 2010-285678, A

However, in the copper composite particles of Patent Document 1, since the agglomerates of copper hydride fine particles are attached to the surface of the metal copper particles, the specific surface area of the particles increases, and when used as a bonding paste, Due to the increase in viscosity, the filling rate of the copper particles cannot be increased, which may cause a decrease in thermal conductivity or a decrease in strength of the bonding layer.

One aspect of the present disclosure has been made in view of such circumstances, and includes a method for manufacturing copper particles for bonding having high sinterability and thermal conductivity, and copper particles for bonding obtained by the manufacturing method. By using a bonding paste and the bonding paste, a semiconductor device and an electric / electronic component having high bonding strength and excellent reliability are provided.

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the following inventions can solve the problems.

That is, the present disclosure relates to the following.
[1] A method for producing copper particles for bonding, which has a step of further forming a copper layer on the surface of (A) metallic copper powder by a liquid phase reduction method.
[2] The method for producing copper particles for bonding according to the above [1], wherein (A) metallic copper powder, (B) copper compound, and (C) reducing compound are mixed in the liquid phase in the step. ..
[3] The method for producing copper particles for bonding according to the above [1] or [2], wherein the (A) metallic copper powder is prepared by an atomizing method, an electrolytic method, or a chemical reduction method.
[4] The method for producing copper particles for bonding according to any one of the above [1] to [3], wherein (D) an organic protective compound is further added in the step.
[5] The method for producing copper particles for bonding according to the above [4], wherein the (D) organic protective compound is at least one selected from carboxylic acids, alkylamines, and carboxylic acid amine salts.
[6] A bonding paste containing the bonding copper particles obtained by the manufacturing method according to any one of the above [1] to [5].
[7] A semiconductor device bonded by using the bonding paste according to the above [6].
[8] An electric / electronic component joined by using the joining paste according to the above [6].

According to the present disclosure, a method of manufacturing a copper particle for bonding having high sinterability and thermal conductivity, a bonding paste containing the copper particles for bonding obtained by the manufacturing method, and a bonding paste by using the bonding paste, It is possible to provide a semiconductor device and electric / electronic components having high bonding strength and excellent reliability.

2 is an image of a cross section obtained by photographing the copper particles 1 obtained in Synthesis Example 1 with a scanning electron microscope (SEM) (magnification: 20,000 times). The bonding paste of Example 1 is cured at 200 ° C. for 60 minutes, the obtained sintered film is photographed with a scanning electron microscope (SEM) (magnification: 20,000 times), and is an image of a cross section obtained. 3 is an image of a cross section obtained by curing the bonding paste of Comparative Example 1 at 200 ° C. for 60 minutes, photographing the obtained sintered film with a scanning electron microscope (SEM) (magnification: 20,000 times).

<Method of manufacturing copper particles for bonding>
The method for producing copper particles for bonding according to the present disclosure has a step of further forming a copper layer on the surface of (A) metallic copper powder by a liquid phase reduction method.
In the method for producing copper particles for bonding according to the present disclosure, a new copper layer is formed on the surface of the (A) metallic copper powder while suppressing surface oxidation of the (A) metallic copper powder in the liquid phase. Copper particles for bonding (hereinafter, also simply referred to as copper particles) excellent in sinterability and thermal conductivity can be obtained.

Hereinafter, the present disclosure will be described in detail with reference to an embodiment.
The method for producing copper particles for bonding according to one aspect of the present disclosure includes a step (hereinafter, also simply referred to as a copper layer forming step) of further forming a copper layer on the surface of the (A) metallic copper powder by a liquid phase reduction method. If it does, it will not be specifically limited.
In the copper layer forming step, (A) metallic copper powder, (B) copper compound, and (C) reducing compound are mixed in the liquid phase. By performing the above mixing in the liquid phase, the surface oxidation of the (A) metallic copper powder is suppressed. Further, it is presumed that the copper compound (B) is reduced by the reducing compound (C), and the metallic copper released from the copper compound (B) is deposited on the surface of the metallic copper powder (A) to form a copper layer. It
In addition, although all the liberated metallic copper may be deposited on the surface of the (A) metallic copper powder, it does not deposit on the surface of the (A) metallic copper powder and is present in the liquid phase as small-sized copper particles. You may.
The proportion of metallic copper deposited on the surface of (A) metallic copper powder can be determined by appropriately selecting (A) the amount of metallic copper powder, (B) the amount of copper compound, and the temperature condition for the reduction reaction. Can be adjusted.

(A) The metallic copper powder is not particularly limited, and is prepared by a known method such as an atomizing method, an electrolysis method, a chemical reduction method, a crushing / smashing method, a plasma rotary electrode method, a uniform droplet spraying method, a heat treatment method, or the like. What has been done can be used. As the metal copper powder (A), those prepared by an atomizing method, an electrolytic method, or a chemical reduction method may be used from the viewpoint of controlling the particle diameter and the particle shape.
Further, as the metal copper powder (A), a commercially available product may be used, and specifically, Cu-HWQ (manufactured by Fukuda Metal Foil & Powder Co., Ltd., D50 = 1.5 μm, spherical), 1200Y (Mitsui Metal Co., Ltd.) Mining Industry Co., Ltd., D50 = 2.1 μm, irregular shape) and the like. These may be used alone or in combination of two or more.

The (A) metallic copper powder may have an average particle size of more than 0.5 μm and 30 μm or less, 0.5 μm or more and 20 μm or less, and 1 μm or more and 20 μm or less. Further, the shape of the metal copper powder (A) is not particularly limited, and examples thereof include spherical shape, plate shape, flake shape, scale shape, dendritic shape, rod shape, wire shape, and irregular shape.
The average particle diameter of the (A) metallic copper powder is a volume average particle diameter, and can be measured using a laser diffraction / scattering particle size distribution measuring device or the like.

The above (A) metallic copper powder may be treated with a lubricant or a rust preventive. A typical example of such treatment is treatment with a carboxylic acid compound. Examples of the carboxylic acid compound include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, palmitic acid, oleic acid, stearic acid, isostearic acid, oxalic acid, Malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, diglycolic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, glycolic acid, lactic acid, Examples thereof include tartronic acid, malic acid, glyceric acid, hydroxybutyric acid, tartaric acid, citric acid and isocitric acid. Carboxylic acid compounds are formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, palmitic acid, oleic acid, stearic acid, isostearic acid, from the viewpoint of enhancing sinterability. Acid, oxalic acid, malonic acid, succinic acid, may be glutaric acid, from the viewpoint of dispersibility and oxidation resistance, caproic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, malonic acid, succinic acid, It may be glutaric acid.

The (B) copper compound is not particularly limited as long as it contains a copper atom. Examples of the (B) copper compound include copper carboxylate, copper oxide, copper hydroxide, and copper nitride. The copper compound (B) may be copper carboxylate from the viewpoint of uniformity during the reaction. These may be used alone or in combination of two or more.

Examples of the copper carboxylate include copper (I) formate, copper (I) acetate, copper (I) propionate, copper (I) butyrate, copper (I) valerate, copper (I) caproate, and copper (I) caprylate. ), Copper (I) caprate, copper (II) formate, copper (II) acetate, copper (II) propionate, copper (II) butyrate, copper (II) valerate, copper (II) caproate, caprylic acid Examples thereof include carboxylic acid copper anhydrides or hydrates such as copper (II), copper (II) caprate, and copper (II) citrate. The copper carboxylate may be copper (II) acetate monohydrate from the viewpoint of productivity and availability. These may be used alone or in combination of two or more.

Also, as the copper carboxylate, a commercially available product may be used, or a product obtained by synthesis may be used.

The synthesis of copper carboxylate can be carried out by a known method, for example, copper (II) hydroxide and a carboxylic acid compound can be obtained by mixing and heating.

Examples of copper oxide include copper (II) oxide and copper (I) oxide, and may be copper (I) oxide 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.

The compounding amount of the (B) copper compound may be 0.1 to 10 mol, 0.5 to 5 mol, or 0.7 to 2 mol based on 1 mol of the (A) metal copper powder. Good. When the compounding amount of the (B) copper compound is 0.1 mol or more, the copper layer can be sufficiently formed on the surface of the (A) metallic copper powder, and when the compounding amount is 10 mol or less, the copper layer is formed on the surface. It is possible to suppress the aggregation of the (A) metal copper powders.

(C) The reducing compound is not particularly limited as long as it has a reducing ability to reduce the copper compound (B) and release metallic copper from the copper compound (B). The boiling point of the reducing compound (C) may be 70 ° C. or higher, or may be the heating temperature or higher in the heating step. Further, the (C) reducing compound may be a compound composed of carbon, hydrogen and oxygen, which is soluble in an organic solvent described later.

A typical example of such a (C) reducing compound is a hydrazine derivative. Examples of the hydrazine derivative 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 and the like. These may be used alone or in combination of two or more.

The compounding amount of the reducing compound (C) may be 0.5 to 5 mol, 0.7 to 3 mol, or 0.9 to 2 mol with respect to 1 mol of the (B) copper compound. Good. When the compounding amount of the reducing compound (C) is 0.5 mol or more, the copper compound (B) can be sufficiently reduced and the metal copper powder (A) can be sufficiently coated, and the amount is 5 mol or less. In addition, it is possible to suppress an excessive reaction and suppress the aggregation of generated particles.

In the copper layer forming step, (D) an organic protective compound may be further added. (D) Addition of the organic protective compound enhances sinterability. The (D) organic protective compound is not particularly limited as long as it forms a complex with the (B) copper compound. The organic protective compound (D) may be a compound containing at least one selected from a carboxylic acid, an alkylamine and a carboxylic acid amine salt, or may be a carboxylic acid amine salt, from the viewpoint of enhancing the sinterability. ..
The (D) organic protective compound serves as a reaction medium for the decomposition reaction of the (B) copper compound when the complex of the (B) copper compound and the (D) organic protective compound is heated and the (B) copper compound is decomposed. It works. Furthermore, the (D) organic protective compound has a function of adhering to the surface of metallic copper liberated from the (B) copper compound by thermally decomposing and reducing the (B) copper compound and suppressing oxidation.

Examples of the carboxylic acid include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, hexanoic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, oleic acid, stearic acid, isostearic acid and the like; oxalic acid. , Dicarboxylic acids such as malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, diglycolic acid; benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid, gallic acid, etc. Aromatic carboxylic acids, such as glycolic acid, lactic acid, tartronic acid, malic acid, glyceric acid, hydroxybutyric acid, tartaric acid, citric acid and isocitric acid.

The alkylamine is not particularly limited in its structure as long as it is an amine compound having an aliphatic hydrocarbon group such as an alkyl group as a group to be bonded to an amino group, and examples thereof include an alkylmonoamine having one amino group and an amino group. Examples thereof include alkyldiamine having two. The alkyl group may further have a substituent.

Specific examples of the alkyl monoamine include dipropylamine, butylamine, dibutylamine, hexylamine, cyclohexylamine, heptylamine, octylamine, nonylamine, decylamine, 3-aminopropyltriethoxysilane, dodecylamine, oleylamine and the like. Examples of the diamine include ethylenediamine, N, N-dimethylethylenediamine, N, N'-dimethylethylenediamine, N, N-diethylethylenediamine, N, N'-diethylethylenediamine, 1,3-propanediamine and 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. Can be mentioned.
The alkyl monoamine such as primary amine (R ¹ NH ₂ ) or secondary amine (R ² R ³ NH) efficiently reacts with the above-mentioned copper carboxylate to form a carboxylate copper-amine complex.

The carboxylic acid amine salt can be obtained from a carboxylic acid compound and an amine compound, and a commercially available product may be used, or a product obtained by synthesis in advance may be used. Further, the carboxylic acid amine salt may be generated in-situ by separately charging the carboxylic acid compound and the amine compound into the reaction vessel during the production process of the copper particles for bonding.

The carboxylic acid amine salt is produced by mixing a carboxylic acid compound and an amine compound in an organic solvent in an equivalent amount of functional groups and mixing them at a relatively mild temperature condition of room temperature (25 ° C.) to about 100 ° C. .. The carboxylic acid amine salt may be taken out from the reaction solution containing the product by a distillation method or a recrystallization method.

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 acid, dicarboxylic acid, aromatic carboxylic acid, and hydroxy acid. These may be used alone or in combination of two or more. The carboxylic acid compound may be a monocarboxylic acid or a dicarboxylic acid from the viewpoint of sinterability.

The thermal decomposition temperature of the carboxylic acid compound constituting the carboxylic acid amine salt may be 200 ° C. or lower, 190 ° C. or lower, or 180 ° C. or lower. If the thermal decomposition temperature is within this range, the sinterability will be good.

Further, of the carboxylic acid compounds constituting the carboxylic acid amine salt, those having a boiling point in the lower temperature region than the thermal decomposition temperature may have a boiling point of 280 ° C. or lower, or 260 ° C. or lower, 240 It may be below the temperature. If the boiling point is in this range, the sinterability will be good.

Among the carboxylic acid compounds constituting the carboxylic acid amine salt, as monocarboxylic acid, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, oleic acid, stearin Acid, isostearic acid, etc. are mentioned. These may be used alone or in combination of two or more. The monocarboxylic acid, from the viewpoint of sinterability, may be formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, caprylic acid, octylic acid, nonanoic acid, capric acid, valeric acid, caproic acid. It may be caprylic acid, nonanoic acid, or octylic acid.

Among the carboxylic acid compounds constituting the carboxylic acid amine salt, the dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, diglycolic acid and the like. Can be mentioned. 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, diglycolic acid, or oxalic acid, malonic acid, succinic acid, or diglycolic acid. May be.

Among the carboxylic acid compounds that compose 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. The aromatic carboxylic acid may be benzoic acid from the viewpoint of sinterability.

Among the carboxylic acid compounds constituting the carboxylic acid amine salt, examples of the hydroxy acid 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. The hydroxy acid may be glycolic acid, lactic acid, or malic acid from the viewpoint of sinterability.

The amine 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 alkylmonoamine, alkyldiamine, and alkanolamine. These may be used alone or in combination of two or more. The amine compound may be an alkylmonoamine or an alkanolamine from the viewpoint of improving the sinterability.

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

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

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

The boiling point of the organic protective compound (D) may be 70 ° C. or higher and 280 ° C. or lower, 100 ° C. or higher and 260 ° C. or lower, and 120 ° C. or higher and 240 ° C. or lower. When the boiling point of the organic protective compound (D) is within the above range, the obtained copper particles for bonding show even better sinterability. The boiling point of the organic protective compound (D) may be equal to or higher than the heating temperature in the heating step and may be equal to or lower than the sintering temperature during use.

The compounding amount of the (D) organic protective compound may be 0.1 to 10 mol, 0.5 to 5 mol, or 1 to 3 mol with respect to 1 mol of the (B) copper compound. .. When the compounding amount of the (D) organic protective compound is 0.1 mol or more, the metal layer formed on the surface of the (A) metallic copper powder can be satisfactorily coated with the (D) organic protective compound and is 3 mol or less. If so, good sinterability can be obtained.

The solvent used in the copper layer forming step is not particularly limited as long as it can be used as a reaction solvent that does not inhibit the properties of the complex or the like produced from the mixture obtained by mixing the above raw materials. it can. As the solvent, an alcohol that is compatible with the reducing compound (C) may be used.

Further, since the reduction reaction of the copper ion by the reducing compound (C) is an exothermic reaction, it may be an organic solvent that does not volatilize during the reduction reaction. The organic solvent has a boiling point of 70 ° C. or higher and may be composed of carbon, hydrogen and oxygen.

Examples of the alcohol used as the organic solvent include 1-propanol, 2-propanol, butanol, pentanol, hexanol, heptanol, octanol, ethylene glycol, 1,3-propanediol, 1,2-propanediol, butylcarbitol, Examples thereof include butyl carbitol acetate, ethyl carbitol, ethyl carbitol acetate, diethylene glycol diethyl ether, butyl cellosolve and the like. These may be used alone or in combination of two or more.

The organic solvent may be used in such an amount that each of the above-mentioned components can sufficiently react, and for example, about 50 to 2000 mL may be used.

(Formation of mixture)
In the method for producing copper particles for bonding according to one aspect of the present disclosure, first, an organic solvent is housed in a reaction container, and in the organic solvent, the above-mentioned (A) metallic copper powder, (B) copper compound, and ( C) Reducing compound and, if necessary, (D) organic protecting compound are mixed. The order of mixing these compounds is not particularly limited, and the above compounds may be mixed in any order.

In order to efficiently form a complex of the copper compound (B) and the organic protective compound (D), the copper compound (B) and the organic protective compound (D) are mixed first, and the mixture is heated at 0 to 110 ° C. The mixture may be mixed for about 5 to 30 minutes, and then (A) metallic copper powder and (C) reducing compound may be added and mixed.

(Heating the mixture)
In the method for producing copper particles for bonding according to one aspect of the present disclosure, the mixture obtained by mixing the above is then sufficiently heated in a nitrogen atmosphere to advance the reduction reaction of the copper compound (B). Thereby, the metallic copper released from the copper compound (B) can be deposited on the surface of the metallic copper powder (A) to form a copper layer. At this time, by blending the (D) organic protective compound, the (D) organic protective compound adheres to the surface of the metallic copper released from the (B) copper compound, the growth of the metallic copper is controlled, and the metallic copper is controlled. Can be prevented from becoming coarse.

The heating temperature for heating the above mixture may be lower than the boiling points of the raw material compound and the organic solvent, and may be, for example, 70 to 150 ° C. or 80 to 120 ° C. When the heating temperature is within the above range, the copper compound (B) can be sufficiently reacted while controlling the aggregation of particles.

The solid matter deposited here may be separated from the excess (D) organic protective compound by centrifugation or the like, washed with an organic solvent, and dried under reduced pressure. By such an operation, the copper particles for bonding can be obtained.

(Shape and size of copper particles for bonding)
For the copper particles obtained by the method for producing copper particles for bonding of the present embodiment, the type and amount of (A) metallic copper powder, (B) copper compound, and (C) reducing compound, and the reaction temperature are appropriately selected. By doing so, it can be adjusted to any shape and size.

The average particle size of the copper particles may be 0.5 to 30 μm, 0.5 to 20 μm, or 1 to 20 μm from the viewpoint of the denseness of the bonding layer.
The average particle size of the copper particles is a number average particle size, and can be determined by averaging the particle sizes of 10 or more particles measured by scanning electron microscope (SEM) observation. Specifically, it can be measured by the method described in Examples.

The thickness (average value) of the copper layer formed on the surface of the (A) copper metal powder may be 5 to 500 nm, 10 to 200 nm, or 20 to 100 nm. .. When the thickness of the copper layer is 5 nm or more, sufficient sinterability can be obtained, and when it is 500 nm or less, chemical stability is increased, and thus oxidation resistance can be obtained.
In addition, the thickness of the copper layer is an image of a cross section obtained by photographing the copper particles for bonding using a transmission electron microscope (Transmission Electron Microscope, TEM) or a scanning electron microscope (Scanning Electron Microscope, SEM). The thickness of the copper layer can be measured at 100 points and the average value can be obtained.

The coverage of the copper layer (A) with the metal copper powder may be 0.1% or more, 2% or more, or 5% or more.
The coverage of the copper layer is determined by observing the copper particles for bonding using a transmission electron microscope (TEM), an energy dispersive X-ray analyzer (Energy Dispersive X-ray microanalyzer, EDX), and the like (A). The ratio of the portion covering the surface of the metal copper powder can be calculated, and the average value thereof can be obtained.

<Paste for bonding>
The bonding paste of the present embodiment contains the bonding copper particles obtained by the above-described method for manufacturing the bonding copper particles. Therefore, the bonding paste of this embodiment can be bonded without pressure and has excellent adhesiveness. Further, since a cured product having good bonding characteristics can be obtained, it can be used as a die attach paste for element adhesion or a material for adhering a heat dissipation member.

(Thermosetting resin)
By including the thermosetting resin, the bonding paste of the present embodiment can be an adhesive material (paste) having an appropriate viscosity. Further, when the bonding paste of the present embodiment contains a thermosetting resin, the temperature of the bonding paste rises due to the reaction heat during curing, and the sinterability of the bonding copper particles is promoted.
The thermosetting resin is not particularly limited as long as it is a thermosetting resin generally used for adhesives. The thermosetting resin may be a liquid resin or a liquid at room temperature (25 ° C.). Examples of the thermosetting resin include cyanate resin, epoxy resin, radical-polymerizable acrylic resin, and maleimide resin. These may be used alone or in combination of two or more.

Cyanate resin is a compound that has an —NCO group in its molecule, and is a resin that cures by forming a three-dimensional network structure when the —NCO group reacts when heated. Specific examples include 1,3-dicyanatobenzene, 1,4-dicyanatobenzene, 1,3,5-tricyanatobenzene, 1,3-dicyanatonaphthalene, 1,4-dicyanatonaphthalene, 1, 6-dicyanatonaphthalene, 1,8-dicyanatonaphthalene, 2,6-dicyanatonaphthalene, 2,7-dicyanatonaphthalene, 1,3,6-tricyanatonaphthalene, 4,4′-dicyanatobiphenyl, bis (4-Cyanatophenyl) methane, bis (3,5-dimethyl-4-cyanatophenyl) methane, 2,2-bis (4-cyanatophenyl) propane, 2,2-bis (3,5-dibromo) -4-Cyanatophenyl) propane, bis (4-cyanatophenyl) ether, bis (4-cyanatophenyl) thioether, bis (4-cyanatophenyl) sulfone, tris (4-cyanatophenyl) phosphite, tris Examples thereof include (4-cyanatophenyl) phosphate, and cyanates obtained by reacting a novolac resin with a cyanogen halide. Further, as the cyanate resin, a prepolymer having a triazine ring formed by trimerizing the cyanate group of these polyfunctional cyanate resins can also be used. The prepolymer is obtained by polymerizing the above-mentioned polyfunctional cyanate resin monomer using, for example, a mineral acid, an acid such as Lewis acid, a sodium alcoholate, a base such as a tertiary amine, a salt such as sodium carbonate as a catalyst. Be done.

As the curing accelerator for the cyanate resin, generally known ones can be used. For example, zinc octylate, tin octylate, cobalt naphthenate, zinc naphthenate, organometallic complexes such as iron acetylacetone, metal salts such as aluminum chloride, tin chloride, zinc chloride, amines such as triethylamine and dimethylbenzylamine. However, the present invention is not limited to these. These curing accelerators can be used alone or in combination of two or more.

Epoxy resin is a compound that has one or more glycidyl groups in the molecule, and is a resin that forms a three-dimensional network structure by heating and reacts with the glycidyl groups to cure. Two or more glycidyl groups may be contained in one molecule. This is because a compound having only one glycidyl group cannot exhibit sufficient cured product characteristics even when reacted. The compound containing two or more glycidyl groups in one molecule can be obtained by epoxidizing a compound having two or more hydroxyl groups. Examples of such a compound include bisphenol compounds such as bisphenol A, bisphenol F and biphenol or derivatives thereof, hydrogenated bisphenol A, hydrogenated bisphenol F, hydrogenated biphenol, alicyclic rings such as cyclohexanediol, cyclohexanedimethanol and cyclohexanediethanol. Diols having a structure or their derivatives, butanediol, hexanediol, octanediol, nonanediol, decanediol, and other aliphatic diols or their derivatives, etc., which are epoxidized, bifunctional, trihydroxyphenylmethane skeleton, aminophenol Examples include trifunctional compounds obtained by epoxidizing compounds having a skeleton, and polyfunctional compounds obtained by epoxidizing phenol novolac resins, cresol novolac resins, phenol aralkyl resins, biphenyl aralkyl resins, and naphthol aralkyl resins. It is not limited. In addition, since the above-mentioned epoxy resin is made into a paste at room temperature (25 ° C) as a bonding paste, it may be liquid at room temperature (25 ° C) alone or as a mixture. It is also possible to use reactive diluents as is customary. Examples of the reactive diluent include monofunctional aromatic glycidyl ethers such as phenyl glycidyl ether and cresyl glycidyl ether, and aliphatic glycidyl ethers.

At this time, a curing agent is used for the purpose of curing the epoxy resin, and examples of the curing agent for the epoxy resin include aliphatic amines, aromatic amines, dicyandiamide, dihydrazide compounds, acid anhydrides, and phenol resins. .. Examples of the dihydrazide compound include adipic acid dihydrazide, dodecanoic acid dihydrazide, isophthalic acid dihydrazide, carboxylic acid dihydrazide such as p-oxybenzoic acid dihydrazide, and the like, and acid anhydrides include phthalic anhydride, tetrahydrophthalic anhydride, hexahydro. Examples thereof include phthalic anhydride, endomethylenetetrahydrophthalic anhydride, dodecenylsuccinic anhydride, a reaction product of maleic anhydride and polybutadiene, and a copolymer of maleic anhydride and styrene.

Furthermore, a curing accelerator can be blended to accelerate curing, and as the curing accelerator for the epoxy resin, imidazoles, triphenylphosphine or tetraphenylphosphine and salts thereof, amine compounds such as diazabicycloundecene, and The salt etc. are mentioned. Examples of the curing accelerator include 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-methyl-5-hydroxymethylimidazole, 2-phenyl-4. An imidazole compound such as 5,5-dihydroxymethylimidazole, 2-C ₁₁ H ₂₃ -imidazole, an adduct of 2-methylimidazole and 2,4-diamino-6-vinyltriazine may be used. The curing accelerator may be an imidazole compound having a melting point of 180 ° C. or higher.

Radically polymerizable acrylic resin is a compound that has a (meth) acryloyl group in its molecule, and is a resin that cures by forming a three-dimensional network structure by the reaction of the (meth) acryloyl group. One or more (meth) acryloyl groups may be contained in the molecule.

Here, examples of the acrylic resin include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 3-hydroxybutyl. (Meth) acrylate, 4-hydroxybutyl (meth) acrylate, 1,2-cyclohexanediol mono (meth) acrylate, 1,3-cyclohexanediol mono (meth) acrylate, 1,4-cyclohexanediol mono (meth) acrylate, 1,2-Cyclohexanedimethanol mono (meth) acrylate, 1,3-Cyclohexanedimethanol mono (meth) acrylate, 1,4-Cyclohexanedimethanol mono (meth) acrylate, 1,2-Cyclohexanediethanol mono (meth) acrylate 1,3-cyclohexanediethanol mono (meth) acrylate, 1,4-cyclohexanediethanol mono (meth) acrylate, glycerin mono (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane mono (meth) acrylate, trimethylol Propane di (meth) acrylate, pentaerythritol mono (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, neopentyl glycol mono (meth) acrylate and other (meth) acrylates having a hydroxyl group and these Examples thereof include a (meth) acrylate having a carboxyl group obtained by reacting a (meth) acrylate having a hydroxyl group with a dicarboxylic acid or a derivative thereof. Examples of the dicarboxylic acid that can be used here include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, phthalic acid, and tetrahydrophthalic acid. , Hexahydrophthalic acid and their derivatives.

As the acrylic resin, a polyether having a molecular weight of 100 to 10,000, a polyester, a polycarbonate, a poly (meth) acrylate compound having a (meth) acrylic group, a (meth) acrylate having a hydroxyl group, and a hydroxyl group (meth ) It may be acrylamide or the like.

Maleimide resin is a compound that contains one or more maleimide groups in one molecule, and is a resin that cures by forming a three-dimensional network structure by the reaction of maleimide groups by heating. For example, maleimide resins include N, N '-(4,4'-diphenylmethane) bismaleimide, bis (3-ethyl-5-methyl-4-maleimidophenyl) methane, 2,2-bis [4- (4- Examples include bismaleimide resins such as maleimidophenoxy) phenyl] propane. The maleimide resin may be a compound obtained by the reaction of a dimer acid diamine and maleic anhydride, or a compound obtained by the reaction of a maleimidated amino acid such as maleimidoacetic acid and maleimidocaproic acid with a polyol. The maleimidated amino acid is obtained by reacting maleic anhydride with aminoacetic acid or aminocaproic acid, and the polyol may be a polyether polyol, a polyester polyol, a polycarbonate polyol, or a poly (meth) acrylate polyol. It may not contain a group ring.

Here, when the thermosetting resin is blended, the blending amount is 1 to 20 parts by mass with respect to 100 parts by mass of the copper particles. When the amount of the thermosetting resin is 1 part by mass or more, the adhesiveness of the thermosetting resin becomes good. When the content of the thermosetting resin is 20 parts by mass or less, the content of the copper component increases, so that high thermal conductivity can be sufficiently ensured and heat dissipation can be improved. In addition, the bonding paste does not have an excessive amount of organic components and suppresses deterioration due to light and heat, and as a result, the life of the light emitting device can be extended. By setting the content in such a range, it is possible to easily maintain the mechanical strength of the entire adhesive layer by utilizing the adhesive performance of the thermosetting resin.

(Organic solvent)
As the organic solvent, a known solvent can be used as long as it functions as a reducing agent.
The organic solvent may be alcohol. Examples of alcohols include aliphatic polyhydric alcohols. Examples of the aliphatic polyhydric alcohol include glycols such as ethylene glycol, diethylene glycol, propylene glycol, diproylene glycol, 1,4-butanediol, glycerin and polyethylene glycol. These organic solvents may be used alone or in combination of two or more.

The bonding paste increases the reducing power of alcohol by using alcohol as an organic solvent, and by increasing the temperature by heat treatment during paste hardening (sintering). The copper oxide partially present in the copper particles and the metal oxide on the metal substrate (for example, copper oxide) are reduced by the alcohol to be a pure metal, and as a result, are more dense and highly conductive, and are It is considered that a cured film having high adhesion can be formed. In addition, since it is sandwiched between the semiconductor element and the metal substrate, the alcohol partially returns to the reflux state during the heat treatment during paste hardening, and the solvent alcohol is not immediately lost from the system due to volatilization. The metal oxide is reduced more efficiently at the curing temperature.

Specifically, the boiling point of the organic solvent may be 100 to 300 ° C, or 150 to 290 ° C. When the boiling point is 100 ° C. or higher, the bonding paste does not have too high volatility even at room temperature, and it is possible to control the reduction of the reduction ability due to the volatilization of the dispersion medium, and obtain stable adhesive strength. You can When the boiling point is 300 ° C. or less, the bonding paste is likely to sinter the cured film (conductive film) and can form a film with excellent compactness, and at the same time volatilizes the organic solvent during sintering. Encourage.

When blending the organic solvent, the blending amount may be 7 to 20 parts by mass when the copper particles are 100 parts by mass. When the blending amount of the organic solvent is 7 parts by mass or more, the viscosity does not become too high and the workability can be improved. When the compounding amount of the organic solvent is 20 parts by mass or less, the viscosity change of the bonding paste is controlled and the sinking of the copper particles in the bonding paste is controlled, so that the reliability can be improved.

In the bonding paste of the present embodiment, in addition to the above respective components, a curing accelerator, rubber, silicone, etc., which are generally blended in a composition of this type, in a range that does not impair the effects of the present disclosure, reduce stress. Agents, coupling agents, defoaming agents, surfactants, colorants (pigments, dyes), various polymerization inhibitors, antioxidants, solvents, and other various additives can be blended as necessary. Each of these additives may be used alone or in combination of two or more.

The bonding paste of the present embodiment, after sufficiently mixing the above-mentioned copper particles, and an additive such as a thermosetting resin, an organic solvent, and a coupling agent that are blended as necessary, further disperse and kneader. It can be prepared by kneading with a three-roll mill or the like and then defoaming.

The viscosity of the bonding paste of the present embodiment may be 20 to 300 Pa · s or 40 to 200 Pa · s.
The bonding strength of the bonding paste of the present embodiment may be 20 MPa or more, or 25 MPa or more.
Further, the thermal conductivity of the bonding paste of this embodiment may be 100 W / mK or higher, or 120 W / mK or higher.
The viscosity, bonding strength, and thermal conductivity can be measured by the methods described in the examples.

The thus obtained bonding paste of the present embodiment has excellent high heat conductivity and heat dissipation. Therefore, when it is used as a bonding material for an element or a heat dissipation member to a substrate or the like, the heat dissipation inside the device to the outside is improved, and the product characteristics can be stabilized.

<Semiconductor device and electric / electronic parts>
The semiconductor device and the electric / electronic component of the present embodiment are excellent in reliability because they are joined by using the above-mentioned joining paste.

The semiconductor device of this embodiment is formed by adhering a semiconductor element onto a substrate that serves as an element supporting member, using the above-mentioned bonding paste. That is, the bonding paste is used here as a die attach paste, and the semiconductor element and the substrate are bonded and fixed via this paste.

Here, the semiconductor element may be any known semiconductor element, and examples thereof include a transistor and a diode. Further, as the semiconductor element, a light emitting element such as an LED can be mentioned. The type of the light emitting element is not particularly limited, and examples thereof include those in which a nitride semiconductor such as InN, AlN, GaN, InGaN, AlGaN, or InGaAlN is formed as a light emitting layer on the substrate by the MOBVC method or the like. Be done.
Further, as the element supporting member, a supporting member formed of a material such as copper, copper-plated copper, PPF (pre-plating lead frame), glass epoxy, or ceramics can be used.

The bonding paste of this embodiment can bond base materials that have not been metal-plated. The semiconductor device thus obtained has dramatically improved connection reliability with respect to the temperature cycle after mounting as compared with the conventional one. Further, since the electric resistance value is sufficiently small and the change with time is small, there is an advantage that the output does not decrease with time even for long-time driving and the life is long.

The electric / electronic component of the present embodiment is formed by bonding the heat dissipation member to the heat dissipation member using the above-mentioned bonding paste. That is, here, the bonding paste is used as a material for bonding the heat dissipation member, and the heat dissipation member and the heat generating member are bonded and fixed via the bonding paste.

The heat generating member may be the above semiconductor element, a member having the semiconductor element, or any other heat generating member. Examples of heat generating members other than semiconductor elements include optical pickups and power transistors. Further, examples of the heat radiation member include a heat sink and a heat spreader.

In this way, by bonding the heat dissipation member to the heat generation member using the above-mentioned bonding paste, it is possible to efficiently dissipate the heat generated in the heat generation member to the outside, thereby increasing the temperature of the heat generation member. Can be suppressed. The heat-generating member and the heat-dissipating member may be directly bonded to each other via a bonding paste, or may be indirectly bonded to each other with another member having high thermal conductivity interposed therebetween.

Next, one embodiment of the present disclosure will be specifically described with reference to examples, but the present invention is not limited to these examples.

(Production of copper particles)
[Synthesis example 1]
(A) 20 mmol of metal copper powder (manufactured by Fukuda Metal Foil Powder Co., Ltd., trade name: Cu-HWQ, spherical particles having an average particle diameter of 1.5 μm) and (B) copper compound (manufactured by Tokyo Kasei Kogyo Co., Ltd.) , Trade name: copper (II) acetate monohydrate) 20 mmol, (D) organic protective compound (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: hexanoic acid) 40 mmol, and butyl cellosolve as an organic solvent (Tokyo Chemical Industry ( (Manufactured by K.K. Co., Ltd.) in a 50 mL sample bottle, and mixed in an aluminum block-type heating stirrer at 90 ° C. for 5 minutes in a nitrogen atmosphere. After the obtained copper powder mixed solution was cooled to room temperature (25 ° C.), hydrazine monohydrate (C) as a reducing compound was added to 3 mL of 1-propanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., trade name: A solution in which 20 mmol of hydrazine monohydrate) was dissolved was added to the metallic copper powder mixed solution in the sample bottle and stirred for 5 minutes. The mixture was again heated and stirred for 2 hours with an aluminum block type heating and stirring machine at 90 ° C. After 5 minutes, 2 mL of ethanol (special grade, manufactured by Kanto Chemical Co., Inc.) was added, and a solid substance was obtained by centrifugation (4000 rpm (1 minute)). The centrifuged solid matter was dried under reduced pressure to obtain powdery copper particles 1 having a copper luster and an average particle diameter of 1.6 μm.
Note that FIG. 1 shows an image obtained by photographing the copper particles 1 with a scanning electron microscope (SEM) (S-3400NX, manufactured by Hitachi High-Technologies Corporation) (magnification: 20,000 times). The copper particles 1 have a polyhedral shape unlike the shape (spherical particles) of the (A) metallic copper powder, and it can be seen that a new copper layer is formed on the surface of the (A) metallic copper powder. ..

[Synthesis example 2]
(D) A powder having an average particle diameter of 1.7 μm and having a copper luster in the same manner as in Synthesis Example 1 except that 40 mmol (trade name: octylamine, manufactured by Tokyo Chemical Industry Co., Ltd.) was used as the organic protective compound. Copper particles 2 having a shape of a circle were obtained.

[Synthesis example 3]
Nonanoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., trade name) 40 mmol and hexylamine (Tokyo Chemical Industry Co., Ltd., trade name) 40 mmol were placed in a 50 mL sample bottle and stirred at 70 ° C. for 30 minutes, and (D ) Hexylamine nonanoate salt as an organic protective compound was synthesized. Thereafter, 40 mmol of the obtained (D) organic protective compound (hexylamine nonanoate salt) and (A) metallic copper powder (manufactured by Fukuda Metal Foil & Powder Co., Ltd., trade name: Cu-HWQ, average particle size 1. 20 mmol of spherical particles of 5 μm), 20 mmol of (B) copper compound (manufactured by Tokyo Chemical Industry Co., Ltd., trade name: copper (II) acetate monohydrate), and butyl cellosolve (manufactured by Tokyo Chemical Industry Co., Ltd.) as an organic solvent. ) 3 mL and 50 mL were put into a 50 mL sample bottle, and mixed in an aluminum block-type heating stirrer at 90 ° C. for 5 minutes under a nitrogen atmosphere. After the obtained copper powder mixed solution was cooled to room temperature (25 ° C.), hydrazine monohydrate (C) as a reducing compound was added to 3 mL of 1-propanol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd., trade name: A solution in which 20 mmol of hydrazine monohydrate) was dissolved was added to the metallic copper powder mixed solution in the sample bottle and stirred for 5 minutes. The mixture was again heated and stirred for 2 hours with an aluminum block type heating and stirring machine at 90 ° C. After 5 minutes, 2 mL of ethanol (special grade, manufactured by Kanto Chemical Co., Inc.) was added, and a solid substance was obtained by centrifugation (4000 rpm (1 minute)). The centrifuged solid matter was dried under reduced pressure to obtain powdery copper particles 3 having a copper luster and an average particle diameter of 1.6 μm.

[Synthesis example 4]
(B) In the same manner as in Synthesis Example 3 except that 20 mmol of cuprous oxide (trade name: FRC-10A, manufactured by Furukawa Chemicals Co., Ltd.) was used as the copper compound, an average particle size of 1.6 μm having a copper luster was obtained. Powdery copper particles 4 were obtained.

[Synthesis example 5]
(A) Powdered copper particles 5 having an average particle diameter of 50 nm and having a copper luster were obtained in the same manner as in Synthesis Example 3 except that the metallic copper powder was not added.
The average particle size of the copper particles 1 to 5 is 10 copper particles (n = n) arbitrarily selected based on an observation image of a scanning electron microscope (Hitachi High-Technologies Corporation, trade name: S-3400NX). It is a value calculated as the average value of 10).

(Example 1)
100 parts by mass of the copper particles 1 obtained in Synthesis Example 1 and 15 parts by mass of diethylene glycol (manufactured by Tokyo Chemical Industry Co., Ltd.) as an organic solvent were prepared and kneaded with a roll to obtain a bonding paste. ..

(Examples 2 to 4 and Comparative Example 1)
A bonding paste was obtained in the same manner as in Example 1 except that the types and blending amounts shown in Table 2 were changed. In addition, in Table 2, a blank column represents no compounding.

The bonding pastes obtained in the above Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 2.
<Evaluation method of bonding paste>
[Pot life]
Using an E-type viscometer (manufactured by Toki Sangyo Co., Ltd., product name: VISCOMETER-TV22, applicable cone-plate type rotor: 3 ° x R17.65), the value at 25 ° C and 5 rpm was measured to obtain the initial viscosity. And Next, the viscosity when the bonding paste was allowed to stand in a constant temperature bath at 25 ° C. was measured, and the number of days until the viscosity increased 0.7 times or more the initial viscosity was measured.

[Sinterability (coating film)]
The sinterability of the bonding paste was evaluated by the following procedure.
(1) The bonding paste was applied to a glass substrate (thickness 1 mm) by screen printing so as to have a thickness of 25 μm.
(2) The applied bonding paste was cured at 200 ° C. for 60 minutes to obtain a sintered film.
(3) The electric resistance of the obtained sintered film was measured by a four-point needle method using Loresta GP (trade name, manufactured by Mitsubishi Chemical Analytical Co., Ltd.).
(4) As a criterion, an electric resistance of 1.0 × 10 ⁻⁴ Ω · m or less was “A”, and an electrical resistance of more than 1.0 × 10 ⁻⁴ Ω · m was “C”.

[Thermal conductivity]
The thermal conductivity of the bonding paste was evaluated by the following procedure.
(1) The bonding paste was applied to a glass substrate (thickness 1 mm) by screen printing so as to have a thickness of 25 μm.
(2) The applied bonding paste was cured at 200 ° C. for 60 minutes to obtain a sintered film.
(3) The thermal conductivity of the obtained sintered film was measured by the laser flash method according to JIS R 1611-1997.

[SEM image]
The SEM image of the bonding paste was evaluated by the following procedure.
(1) The bonding paste of Example 1 and the bonding paste of Comparative Example 1 were each applied to a glass substrate (thickness 1 mm) by screen printing so as to have a thickness of 25 μm.
(2) The applied bonding paste was cured at 200 ° C. for 60 minutes to obtain a sintered film.
(3) The SEM image of the obtained sintered film was photographed at a magnification of 20,000 using a scanning electron microscope (SEM) (manufactured by Hitachi High-Technologies Corporation, S-3400NX).
(4) An image of a cross section of the sintered film obtained from the bonding paste of Example 1 is shown in FIG. FIG. 3 shows an image of a cross section of a sintered film obtained from the bonding paste of Comparative Example 1.

As shown in FIG. 2, since the copper particles 1 obtained by the manufacturing method according to one embodiment of the present disclosure have excellent sinterability, the copper particles 1 themselves, and the copper particles 1 and small particles existing around them. It can be seen that the large diameter copper particles are sintered to form a dense sintered film.
On the other hand, as shown in FIG. 3, in the bonding paste of Comparative Example 1 obtained by mixing small-sized copper particles and large-sized metallic copper powder, the large-sized metallic copper powder was sintered. Because of its low property, small-sized copper particles and large-sized metal copper powder do not sinter, only small-sized copper particles sinter each other, and voids exist in the sintered film. I understand.

<Semiconductor device evaluation method>
[Joint strength]
(1) A silicon chip having a 2 mm × 2 mm bonding surface provided with a gold vapor deposition layer was mounted on a pure copper frame and PPF (Ni—Pd / Au plated copper frame) using a bonding paste.
(2) The above bonding paste was cured at 200 ° C. for 60 minutes in a nitrogen (3% hydrogen) atmosphere.
(3) The silicon chip and the frame joined with the above-mentioned joining paste were subjected to a moisture absorption treatment under the conditions of 85 ° C. and a relative humidity of 85% for 72 hours.
(4) Regarding the bonding strength of the bonding paste, the die shear strength at room temperature (25 ° C.) was measured using DAGE 4000Plus (product name, manufactured by Nordson Co., Ltd.) after curing and after moisture absorption treatment.

[Cold heat shock resistance]
(1) A silicon chip having a 2 mm × 2 mm bonding surface provided with a gold vapor deposition layer was mounted on a copper frame and PPF using a bonding paste.
(2) The above bonding paste was cured at 200 ° C. for 60 minutes in a nitrogen (3% hydrogen) atmosphere.
(3) The silicon chip and the frame bonded with the above-mentioned bonding paste were molded under the following conditions using an epoxy encapsulating material (trade name: KE-G3000D) manufactured by Kyocera Corp., to obtain a semiconductor device.
(4) The semiconductor device was subjected to moisture absorption treatment under the conditions of 85 ° C. and relative humidity of 85% for 168 hours.
(5) In the semiconductor device, an IR reflow treatment (260 ° C., 10 seconds) and a thermal cycle treatment (heating from −55 ° C. to 150 ° C., and cooling to −55 ° C. are set as one cycle, and 1000 cycles of this operation) Cycle).
(6) After each treatment, the number of internal cracks in each semiconductor device was observed with an ultrasonic microscope (Hitachi Power Solution Co., Ltd., trade name: FineSAT).
(7) The thermal shock resistance of the semiconductor device was evaluated by counting the number of samples in which cracks were generated out of 5 samples.

(Molding condition)
Package: 80pQFP (14mm x 20mm x 2mm thickness)
Chip: Gold-plated silicon chip on back side Lead frame: PPF and copper Molding of encapsulant: 175 ° C, 2 minutes Post mold cure: 175 ° C, 8 hours

Examples 1 to 4 using the bonding paste containing the copper particles for bonding obtained by the manufacturing method according to one embodiment of the present disclosure have a high thermal conductivity of 150 W / mK, and both the coating state and the bonding state are sintered. It can be seen that it has excellent properties. On the other hand, Comparative Example 1, which uses a bonding paste obtained by mixing small-sized copper particles and large-sized metal copper powder, shows high sinterability in a coating film state, but a bonded state. It was found that in No. 1 had poor sinterability and had a low thermal conductivity of 40 W / mK.

Claims

(A) A method for producing copper particles for bonding having a step of further forming a copper layer on the surface of the metal copper powder by the liquid phase reduction method.
The method for producing copper particles for bonding according to claim 1, wherein (A) metallic copper powder, (B) copper compound, and (C) reducing compound are mixed in the liquid phase in the step.
The method for producing copper particles for bonding according to claim 1 or 2, wherein the (A) metallic copper powder is prepared by an atomizing method, an electrolysis method, or a chemical reduction method.
The method for producing copper particles for bonding according to any one of claims 1 to 3, wherein (D) an organic protective compound is further added in the step.
The method for producing copper particles for bonding according to claim 4, wherein the (D) organic protective compound is at least one selected from carboxylic acids, alkylamines, and amine salts of carboxylic acids.
A bonding paste containing the bonding copper particles obtained by the manufacturing method according to any one of claims 1 to 5.
A semiconductor device bonded by using the bonding paste according to claim 6.
An electric / electronic component that is joined using the joining paste according to claim 6.