JP6766160B2 - Composition for metal bonding - Google Patents

Description

The present invention relates to a composition for metal bonding, a metal bonding laminate, and an electric control device.

Conventionally, bonding materials such as solder, conductive adhesive, silver paste, and anisotropic conductive film have been used for mechanical, electrical, and / or thermal bonding between metal parts. These joining materials may be used for joining not only metal parts but also ceramic parts, resin parts and the like. Examples of the application of the bonding material include an application of bonding a light emitting element such as an LED to a substrate, an application of bonding a semiconductor chip to a substrate, an application of further bonding these substrates to a heat radiating member, and the like. Prior art documents relating to the bonding material include, for example, Patent Documents 1 to 3.

Patent Document 1 describes a bonding composition containing inorganic particles and organic components, wherein the inorganic particles irreversibly exceed the coefficient of linear expansion of the inorganic substance constituting the inorganic particles as the temperature rises. A bonding composition characterized by swelling is disclosed.

In Patent Document 2, the main silver particles are coated with a carboxylic acid having 6 or less carbon atoms and have an average primary particle diameter of 10 to 30 nm, and the secondary silver particles are coated with a carboxylic acid having 6 or less carbon atoms. A silver particle composed of nanosilver particles having an average primary particle diameter of 100 to 200 nm, submicron silver particles having an average primary particle diameter of 0.3 to 3.0 μm, and a low boiling solvent having a boiling point of 100 to 217 ° C. A bonding material composed of two types of polar solvents having different high boiling points of 230 to 320 ° C. and a dispersant having a phosphate ester group, and the average primary particle size is a TEM image taken at a magnification of 300,000 times. Is the average of the particle diameters measured for 200 or more particles by image software that identifies individual particles by performing circular particle analysis, and the content of the silver particles is 95 mass with respect to the total amount of bonding material. % Or more, the main silver particles are 10 to 40% by mass with respect to the total amount of the bonding material, and the content ratio of the solvent having the lower boiling point and the solvent having the higher boiling point among the two types of solvents is A bonding material characterized by a mass% ratio of 3: 5 to 1: 1 is disclosed.

Patent Document 3 describes metal submicron particles having an average primary particle size (D50 diameter) of 0.5 to 3.0 μm and an average primary particle size of 1 to 200 nm, which are measured by a microtrack particle size distribution measuring device. Therefore, a bonding material containing metal nanoparticles coated with a fatty acid having 6 carbon atoms and a dispersion medium for dispersing them is disclosed.

International Publication No. 2017/006531 Japanese Patent No. 5976684 Japanese Patent No. 5824201

The present inventor is conducting research and development on a composition for metal bonding containing metal particles in order to produce a metal bonding material having high bonding strength, but the metal bonding is performed by a thermal load applied in a heat cycle test or the like. Cracks may occur in the material, and there was room for improvement in durability.

The present invention has been made in view of the above situation, and is a composition for metal bonding suitable for forming a metal bonding material having excellent durability against a thermal load applied in a heat cycle test or the like, and the metal bonding composition. An object of the present invention is to provide a metal-bonded laminate in which metal surfaces are bonded by firing a composition and an electric control device.

The present inventor has studied various compositions for metal bonding suitable for forming a metal bonding material having excellent durability against a thermal load applied in a heat cycle test or the like. As a result, silver particles and a dispersion medium are blended and silver particles are mixed. As a result, the tensile stress at break of the coating film after firing can be improved by using nanoparticles having a particle size of 1 to 99 nm in combination with submicron particles having a particle size of 100 to 999 nm and / or microparticles having a particle size of 1 to 999 μm. I found. Then, the heat cycle test is performed by adjusting the particle size of the silver particles to be blended in the composition for metal bonding, the type of dispersion medium, etc. so that the tensile breaking stress of the coating film when fired at 275 ° C. is 100 MPa or more. The present invention has been completed by finding that an increase in void ratio (void ratio) due to a thermal load applied due to such factors can be suppressed and a metal bonding material having excellent durability can be formed.

The composition for metal bonding of the present invention is a composition for metal bonding used for bonding metal surfaces by firing, and the composition for metal bonding contains silver particles and a dispersion medium, and the silver. The particles include nanoparticles having a particle size of 1 to 99 nm, submicron particles having a particle size of 100 to 999 nm, and / or micron particles having a particle size of 1 to 999 μm, and the tension of the coating film when fired at 275 ° C. It is characterized in that the breaking stress is 100 MPa or more.

The silver particles preferably include the nanoparticles and the submicron particles, and more preferably the mass ratio of the nanoparticles to the submicron particles is 4: 6 to 7: 3.

The metal bonding laminate of the present invention is a metal bonding laminate containing a metal bonding material that joins a first metal surface and a second metal surface, and the metal bonding material has a composition for metal bonding of the present invention. It is characterized by being a sintered body of an object.

At least one of the first metal surface and the second metal surface is preferably the surface of a base material or a plating layer composed of Cu, Ag or Au.

It is preferable that the first metal surface is a part of the semiconductor chip and the second metal surface is a part of the substrate.

The electric control device of the present invention is characterized by comprising the metal bonded laminate of the present invention.

According to the present invention, a metal bonding composition suitable for forming a metal bonding material having excellent durability against a thermal load applied in a heat cycle test or the like, and the metal surface by firing the metal bonding composition. It is possible to provide a metal-bonded laminate in which the above-mentioned material is bonded and an electric control device.

It is a flow chart explaining the manufacturing method of the test piece for measuring the tensile breaking stress of a composition for metal bonding. It is a plane schematic view which showed the shape and size (unit: mm) of the test piece for measuring the tensile breaking stress of a composition for metal bonding. It is sectional drawing which showed the structure of the power device which is an example of a metal-bonded laminated body.

The metal bonding composition of the present embodiment is a metal bonding composition used for bonding metal surfaces by firing, and the metal bonding composition contains silver particles and a dispersion medium, and is described above. The silver particles include nanoparticles having a particle size of 1 to 99 nm, submicron particles having a particle size of 100 to 999 nm, and / or microparticles having a particle size of 1 to 999 μm, and are formed on the coating film when fired at 275 ° C. It is characterized in that the tensile breaking stress is 100 MPa or more.

The metal bonding composition has a tensile stress at break of 100 MPa or more when fired at 275 ° C. The coating may be fired under non-pressurized conditions. The firing time of the coating film is preferably 60 minutes or more. If the tensile breaking stress is less than 100 MPa, a high thermal stress is generated in the heat cycle test in which the upper limit temperature is set to a high temperature such as 175 ° C. or 200 ° C., so that the metal joint material is severely cracked. The upper limit of the tensile breaking stress is not particularly limited, and may be, for example, 500 MPa.

Specific examples of the method for measuring the tensile breaking stress of the coating film will be described below with reference to FIGS. 1 and 2. FIG. 1 is a flow chart illustrating a method for producing a test piece for measuring tensile stress at break in a composition for metal bonding. FIG. 2 is a schematic plan view showing the shape and dimensions (unit: mm) of the test piece for measuring the tensile stress at break of the metal bonding composition.

(Measurement method of tensile breaking stress)
(1) As shown in FIG. 1 (a), the metal bonding composition 52 is slid using a dumbbell-shaped No. 7 type (see FIG. 2) metal mask (plate thickness 90 μm) defined in JIS K 6251. Print on glass 51.
(2) As a preliminary drying, the printed metal bonding composition 52 is placed in an oven set at 70 ° C. and dried for 30 minutes.
(3) As shown in FIG. 1 (b), a slide glass 53 is placed on the dried metal bonding composition 52 (the portion surrounded by the dotted line in FIG. 2), and a reflow furnace (Shin Apex Corporation) is placed. (Manufactured) and fired. The firing treatment in the reflow furnace is performed in an air atmosphere, and the temperature is raised from room temperature to a maximum temperature of 275 ° C. at a heating rate of 3.8 ° C./min and then held at 275 ° C. for 60 minutes. During the firing process, no pressurization is performed and no pressurization is performed. Note that no pressurization means joining without applying a load other than the weight of the object to be bonded such as a semiconductor chip. In this measurement method, the slide glass 53 is placed on the object to be bonded in an actual bonding state (subject). The state where the joint is placed) is reproduced.
(4) As shown in FIG. 1 (c), the fired metal bonding composition 52 is taken out from the reflow furnace and then peeled off from the slide glasses 51 and 53 to obtain a test piece 54 for a tensile test.
(5) The tensile test is performed by a universal tensile tester 5969 manufactured by Instron at a measurement speed of 0.72 mm / min. The tensile breaking stress when the test piece 54 breaks is measured.

The tensile breaking stress is measured on a coating film fired at 275 ° C. When firing a composition for metal bonding, the dispersion medium (solvent) is first volatilized or decomposed and volatilized, and then organic components other than the dispersion medium such as a dispersant used for dispersing silver particles are volatilized or decomposed. Although it volatilizes, silver particles have excellent low-temperature sinterability, so if they are fired to 275 ° C, silver is removed by removing organic components in the composition for metal bonding and by necking (partial fusion) between the particles. Sintering of particles can proceed quickly. The composition for metal bonding of the present embodiment is preferably used by firing at 275 ° C.

The composition for metal bonding of the present embodiment preferably has a mass reduction rate of 6 to 20%, more preferably 8 to 15%, and even more preferably 11 to 12% after firing. The mass reduction rate can be calculated from the results of differential thermal analysis (TG-DTA). According to TG-DTA, the presence or absence of reaction (mainly combustion / oxidative decomposition) and the end point of the reaction can be confirmed.

According to the Hall Petch formula of the following formula (A), it is considered that the tensile breaking stress can be improved as the crystal grain size is reduced.
σy = σ ₀ + k / √d (A)
σy: yield stress, σ ₀ : frictional stress, k: drag coefficient against slip at grain boundaries, d: average grain size

Here, as a method of reducing the crystal grain size, a method of including nanoparticles in the silver particles blended in the composition for metal bonding, a method of increasing the ratio thereof, or a method of shortening the time during which the silver particles are sintered Can be mentioned. By increasing the ratio of nanoparticles in the silver particles to be blended in the metal bonding composition, the number of necking portions between the silver particles can be increased. If the time during which the silver particles are sintered is shortened, the progress of fusion between the silver particles can be suppressed. Shortening the time it takes for the silver particles to sinter is also achieved by delaying the removal of organic components in the metal bonding composition.

As described above, as a method of adjusting the tensile breaking stress of the coating film when fired at 275 ° C., a method of increasing the ratio of nanoparticles in silver particles to be blended in the composition for metal bonding, a dispersant or a dispersion medium. The method of changing the type of is preferable. As for the dispersant, those that volatilize at less than 275 ° C. (= particles are sintered) are preferable. As for the dispersion medium, it is preferable that the silver particles volatilize before sintering. Further, it is preferable to reduce the amount of solvent remaining before the firing step.

The composition for metal bonding is not particularly limited as long as it contains silver particles and a dispersion medium, but is preferably in the form of a paste so that it can be easily applied. Further, in order to make migration less likely to occur, in addition to silver particles, a metal whose ionization sequence is noble than hydrogen, that is, particles such as gold, copper, platinum, and palladium may be used in combination.

The silver particles include nanoparticles having a particle size of 1 to 99 nm (also referred to as nano silver particles), submicron particles having a particle size of 100 to 999 nm, and / or micron particles having a particle size of 1 to 999 μm (also referred to as micron silver particles). Is included. The nanoparticles may be separated from the submicron particles or micron particles and dispersed in the metal bonding composition, or may be attached to at least a part of the surface of the submicron particles or micron particles. It is preferable that the nanoparticles, submicron particles, and micron particles each have independent peaks of particle size distribution.

The average particle size of the silver particles can be measured by a dynamic light scattering method, a small-angle X-ray scattering method, or a wide-angle X-ray diffraction method, and is suitable for measuring the particle size of micron particles. is there. In the present specification, the "average particle size" means the dispersed median diameter. As another method for measuring the average particle size, there is a method of calculating the arithmetic average value of the particle size of about 50 to 100 particles from photographs taken with a scanning electron microscope or a transmission electron microscope. , Suitable for measuring the particle size of nanoparticles.

The average particle size of the nanoparticles is not particularly limited as long as the effect of the present invention is not impaired. If nanoparticles having an average particle diameter of 1 nm or more are used as the small-diameter silver particles, a composition for metal bonding capable of forming a good metal bonding material can be obtained, and the production of silver particles is not costly and practical. is there. Further, when it is 99 nm or less, the dispersibility of the nanoparticles does not easily change with time, which is preferable.

The silver particles preferably contain nanoparticles and submicron particles, and more preferably have a mass ratio of nanoparticles to submicron particles contained in the silver particles of 4: 6 to 7: 3. If the mass ratio of nanoparticles to submicron particles is less than 4: 6 (the mass ratio of nanoparticles is less than 40%), it becomes difficult for the particles to connect to each other and the bond strength between the particles (equivalent to tensile strength) decreases. , Cracks may occur early in the heat cycle test. When the mass ratio of the nanoparticles to the submicron particles exceeds 7: 3 (the mass ratio of the nanoparticles exceeds 70%), the shrinkage during firing becomes large, so that the metal bonding composition in the sintered body The proportion of voids may become too high.

The silver particles preferably contain nanoparticles and micron particles, and more preferably have a mass ratio of nanoparticles to micron particles contained in the silver particles of 7: 3 to 8: 2. If the mass ratio of the nanoparticles to the micron particles is less than 7: 3 (the mass ratio of the nanoparticles is less than 70%), the tensile strength decreases, so that cracks may occur early in the heat cycle test. If the mass ratio of nanoparticles to micron particles exceeds 8: 2 (mass ratio of nanoparticles exceeds 80%), the proportion of voids in the sintered body of the metal bonding composition may become too high. There is.

The average particle size of the micron particles is not particularly limited as long as the effect of the present invention is not impaired, but is preferably 1 to 20 μm. By using micron particles having an average particle size of 1 to 20 μm, volume shrinkage due to sintering can be reduced, and a homogeneous and dense bonding material can be obtained. When submicron particles with an average particle size of less than 1 μm are used as large-diameter silver particles, sintering proceeds at a low temperature, but as the sintering of particles progresses, volume shrinkage increases as the average particle size increases. The object to be joined may not be able to follow the volume shrinkage. In such a case, defects such as voids occur in the metal bonding material, and the bonding strength and reliability of the metal bonding material are lowered. On the other hand, when particles having an average particle size of more than 20 μm are used, sintering at a low temperature hardly proceeds, and large voids formed between silver particles may remain even after sintering. The average particle size of the micron particles is more preferably 1 to 10 μm.

The silver particles can be obtained by a reduction method, for example, by mixing a metal ion source and a dispersant.

The dispersion medium is not particularly limited as long as it can disperse the silver particles, and examples thereof include organic solvents such as hydrocarbons, alcohols, and carbitols. The dispersion medium is preferably one that is volatile during the step of applying the composition for metal bonding, and preferably one that is hard to volatilize at room temperature.

Examples of the above-mentioned hydrocarbons include aliphatic hydrocarbons, cyclic hydrocarbons, and alicyclic hydrocarbons, which may be used alone or in combination of two or more.

Examples of the aliphatic hydrocarbons include saturated or unsaturated aliphatic hydrocarbons such as tetradecane, octadecane, heptamethylnonane, tetramethylpentadecane, hexane, heptane, octane, nonane, decane, tridecane, methylpentane, normal paraffin and isoparaffin. Hydrogen is mentioned.

Examples of the cyclic hydrocarbon include toluene, xylene and the like.

Examples of the alicyclic hydrocarbons include limonene, dipentene, terpinene, tarpinene (also referred to as terpinene), nesole, sinen, orange flavor, terpinene, tarpinolene (also referred to as terpinene), phellandrene, mentadiene, teleben, and dihydro. Examples thereof include cymen, moslen, isotelpinene, isotapinene (also referred to as isotelpinene), critomen, kautsin, kajeptene, oilimene, pinene, televisionn, menthane, pinane, terpene, cyclohexane and the like.

The alcohol is a compound containing one or more OH groups in its molecular structure, and examples thereof include fatty alcohols, cyclic alcohols, and alicyclic alcohols, which may be used alone or in combination of two or more. Good. Further, a part of the OH group may be derived to an acetoxy group or the like as long as the effect of the present invention is not impaired.

Examples of the above-mentioned fatty alcohol include heptanol, octanol (1-octanol, 2-octanol, 3-octanol, etc.), decanol (1-decanol, etc.), lauryl alcohol, tetradecyl alcohol, cetyl alcohol, 2-ethyl-1. -Saturated or unsaturated C6-30 aliphatic alcohols such as hexanol, octadecyl alcohol, hexadecenol and oleyl alcohol can be mentioned.

Examples of the cyclic alcohol include cresol, eugenol and the like.

Examples of the alicyclic alcohol include cycloalkanols such as cyclohexanol, terpineols (including α, β, γ isomers, or any mixture thereof), and terpene alcohols such as dihydroterpineols (monoterpene alcohols, etc.). , Dihydroterpineol, myltenol, sobrerol, menthol, carbeol, perylyl alcohol, pinocarbeol, sobrelol, berbenol and the like.

Examples of the carbitols include butyl carbitol, butyl carbitol acetate, hexyl carbitol and the like.

When the dispersion medium is contained in the metal bonding composition, the initial content may be adjusted according to desired properties such as viscosity, and the initial content of the dispersion medium in the metal bonding composition is 1 to 30. It is preferably by mass%. When the initial content of the dispersion medium is 1 to 30% by mass, the effect of adjusting the viscosity can be obtained within a range that is easy to use as a composition for metal bonding. The more preferable initial content of the dispersion medium is 1 to 20% by mass, and the more preferable initial content is 1 to 15% by mass.

Hexylcarbitol and butylcarbitol acetate are suitable as the dispersion medium to be blended in the metal bonding composition. It is preferable that hexylcarbitol is contained in the dispersion medium in an amount of 50% by mass or more. The preferable solid content concentration of the metal bonding composition is 88 to 93% by mass. If these conditions are satisfied, the viscosity can be adjusted within an appropriate range without lowering the bonding strength and the void ratio, so that a composition for metal bonding having excellent printability with a metal mask can be obtained. Further, since the stability of the viscosity with time can be ensured, the pot life of the metal bonding composition can be extended.

The composition for metal bonding may contain an organic component other than the dispersion medium. The organic component is not particularly limited, and is an additive used for the purpose of adjusting the dispersibility of silver particles, the viscosity, adhesion, drying property, surface tension, and coatability (printability) of a composition for metal bonding. Is used.

Examples of the additive for improving the dispersibility of the silver particles include amines, carboxylic acids, polymer dispersants, unsaturated hydrocarbons and the like. Amines and carboxylic acids contribute to the stability of silver particles in a stored state because functional groups are adsorbed on the surface of silver particles with appropriate strength and hinder mutual contact of silver particles. It is considered that the additive adsorbed on the surface of the silver particles moves and / or volatilizes from the surface of the silver particles during heating, thereby promoting the fusion of the silver particles and the bonding with the base material. By adhering an appropriate amount of the polymer dispersant to at least a part of the silver particles, the dispersion stability can be maintained without losing the low temperature sinterability of the silver particles.

An organic component is attached to at least a part of the surface of the silver particles (that is, at least a part of the surface of the silver particles is covered with an organic protective layer composed of the organic component), and the organic component (organic protection). The layer) preferably contains an amine. In order to stably store nanometer-sized particles exhibiting melting point lowering ability, it is desirable to provide an organic protective layer on at least a part of the surface of the metal particles. Here, since the functional group adsorbs the functional group on the surface of the silver particles with an appropriate strength, the amine can be suitably used as an organic protective layer.

The amine is not particularly limited, and for example, an alkylamine such as oleylamine, butylamine, pentylamine, hexylamine, hexylamine, and octylamine (a linear alkylamine may have a side chain); N- (3-methoxypropyl) alkoxyamines such as propane-1,3-diamine, 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine; cycloalkylamines such as cyclopentylamine and cyclohexylamine; allylamines such as aniline Primary amines such as dipropylamine, dibutylamine, piperidine, hexamethyleneimine, etc., and tertiary amines such as tripropylamine, dimethylpropanediamine, cyclohexyldimethylamine, pyridine, quinoline, etc. Can be used.

As the amine, an amine having about 2 to 20 carbon atoms is preferable, an amine having 4 to 12 carbon atoms is more preferable, and an amine having 4 to 7 carbon atoms is further preferable. Specific examples of amines having 4 to 7 carbon atoms include heptylamine, butylamine, pentylamine, and hexylamine. Since amines having 4 to 7 carbon atoms move and / or volatilize at a relatively low temperature, the low temperature sinterability of silver particles can be fully utilized. Further, the amine may be linear, may be branched, or may have a side chain.

When these organic components are chemically or physically bonded to silver particles, it is possible that they are changed to anions or cations. In this embodiment, ions derived from these organic components are considered. And complexes are also included in the above organic components.

The amine may be, for example, a compound containing a functional group other than the amine, such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group, and a mercapto group. In addition, the above amines may be used alone or in combination of two or more. In addition, the boiling point at room temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower.

As the carboxylic acid, a compound having at least one carboxyl group can be widely used, and examples thereof include formic acid, oxalic acid, acetic acid, hexanic acid, acrylic acid, octyl acid, levulinic acid, and oleic acid. Some carboxyl groups of the carboxylic acid may form a salt with a metal ion. In addition, about the said metal ion, two or more kinds of metal ions may be contained.

The carboxylic acid may be a compound containing a functional group other than the carboxyl group, such as an amino group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group and a mercapto group. In this case, the number of carboxyl groups is preferably equal to or greater than the number of functional groups other than the carboxyl groups. In addition, the above carboxylic acids may be used alone or in combination of two or more. In addition, the boiling point at room temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower.

In addition, amines and carboxylic acids form amide groups. Since the amide group is also appropriately adsorbed on the surface of the silver particles, the organic component may contain an amide group.

The composition ratio (mass) when the amine and the carboxylic acid are used in combination can be arbitrarily selected in the range of 1/99 to 99/1, but is preferably 20/80 to 98/2. It is preferably 30/70 to 97/3.

As the polymer dispersant, a commercially available polymer dispersant can be used. Examples of commercially available polymer dispersants include SOLSPERSE 11200, SOLSPERSE 13940, SOLSPARS 16000, SOLSPASE 17000, SOLSPARSE 18000, SOLSPARSE 20000, SOLSPARSE 24000, SOLSPARES 26000, SOLSPARES 27000, SOLSPARES 28000, and SOLSPARES 54000 (all in Japan). Lubrizol); Disperbic 142; Disparbic 160, Disparbic 161, Disparbic 162, Disparbic 163, Disparbic 166, Disparbic 170, Disparbic 180, Disparbic 182, Disparbic 184, Disper. BIC 190, DISPERBICK 2155 (above, manufactured by BIC Chemie Japan); EFKA-46, EFKA-47, EFKA-48, EFKA-49 (above, manufactured by EFKA Chemical); Polymer 100, Polymer 120, Polymer 150, Polymer 400, Polymer 401, Polymer 402, Polymer 403, Polymer 450, Polymer 451, Polymer 452, Polymer 453 (above, manufactured by EFKA Chemical); Ajispar PB711, Ajispar PA111, Ajispar PB811, Ajispar PW911 (above, manufactured by Ajinomoto); Examples thereof include polymer DOPA-15B, polymer DOPA-22, polymer DOPA-17, polymer TG-730W, polymer G-700, and polymer TG-720W (all manufactured by Kyoeisha Chemical Industry Co., Ltd.). From the viewpoint of low-temperature sinterability and dispersion stability, it is preferable to use Solsparce 11200, Solsperse 13940, Solsperse 16000, Solsperse 17000, Solsperse 18000, Solsperse 28000, Solsperse 54000, Disperbic 142 or Disparbic 2155.

The content of the polymer dispersant is preferably 0.03 to 15% by mass. If the content of the polymer dispersant is 0.1% by mass or more, the dispersion stability of the obtained metal bonding composition is improved, but if the content is too large, the bonding property is lowered. From this point of view, the more preferable content of the polymer dispersant is 0.05 to 3% by mass, and the more preferable content is 0.1 to 2% by mass.

Examples of the unsaturated hydrocarbon include ethylene, acetylene, benzene, acetone, 1-hexene, 1-octene, 4-vinylcyclohexene, cyclohexanone, terpene alcohol, allyl alcohol, oleic alcohol, 2-palmitoleic acid, and petroselinic acid. , Oleic acid, elaidic acid, thiancic acid, ricinoleic acid, linoleic acid, linoleic acid, linolenic acid, arachidonic acid, acrylic acid, methacrylic acid, petroselinic acid, salicylic acid and the like.

Among the above unsaturated hydrocarbons, unsaturated hydrocarbons having a hydroxyl group are preferably used. The hydroxyl group is easily coordinated to the surface of the silver particles, and the aggregation of the silver particles can be suppressed. Examples of unsaturated hydrocarbons having a hydroxyl group include terpene alcohols, allyl alcohols, oleyl alcohols, thiancic acid, ricinolic acid, gallic acid, salicylic acid and the like. It is preferably an unsaturated fatty acid having a hydroxyl group, and examples thereof include thiancic acid, ricinoleic acid, gallic acid, and salicylic acid.

As the dispersant to be blended in the metal bonding composition, amines or carboxylic acids having a boiling point of 150 to 300 ° C. are preferable, and levulinic acid is particularly preferably used.

In addition, the organic component includes an oligomer component that serves as a binder, a resin component, an organic solvent (a part of the solid content may be dissolved or dispersed), and an interface as long as the effects of the present invention are not impaired. Activators, thickeners, surface tension modifiers and the like may be included.

Examples of the resin component include polyester-based resins, polyurethane-based resins such as blocked isocyanate, polyacrylate-based resins, polyacrylamide-based resins, polyether-based resins, melamine-based resins, and terpene-based resins. These may be used alone or in combination of two or more.

Examples of the organic solvent include those listed as the above-mentioned dispersion mediums, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, 1,3-propanediol, 1,2-propanediol, and the like. 1,4-Butandiol, 1,2,6-hexanetriol, 1-ethoxy-2-propanol, 2-butoxyethanol, ethylene glycol, diethylene glycol, triethylene glycol, weight average molecular weight in the range of 200 or more and 1,000 or less Polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having a weight average molecular weight in the range of 300 or more and 1,000 or less, N, N-dimethylformamide, dimethylsulfoxide, N-methyl-2. -Pyrrolidone, N, N-dimethylacetamide, glycerin, acetone and the like can be mentioned, and these may be used alone or in combination of two or more.

Examples of the thickener include clay minerals such as clay, bentonite, and hectrite, polyester emulsion resins, acrylic emulsion resins, polyurethane emulsion resins, emulsions such as blocked isocyanate, methyl cellulose, carboxymethyl cellulose, and hydroxyethyl cellulose. Cellulose derivatives such as hydroxypropyl cellulose and hydroxypropyl methyl cellulose, polysaccharides such as xanthan gum and guar gum can be mentioned, and these may be used alone or in combination of two or more.

The above-mentioned surfactant is not particularly limited, and any of anionic surfactant, cationic surfactant, and nonionic surfactant can be used, and examples thereof include alkylbenzene sulfonates and quaternary ammonium salts. Be done. Fluorine-based surfactants are preferable because the effect can be obtained with a small amount of addition.

The content of the organic component in the composition for metal bonding of the present embodiment is preferably 5 to 50% by mass. When the content is 5% by mass or more, the storage stability of the metal bonding composition tends to be good, and when the content is 50% by mass or less, the conductivity of the metal bonding composition tends to be good. A more preferable content of the organic component is 5 to 30% by mass, and a more preferable content is 5 to 15% by mass.

The metal bonding composition of the present embodiment is used for bonding metal surfaces by firing. A metal bonding laminate containing a metal bonding material that joins a first metal surface and a second metal surface, and the metal bonding material is a metal bonding body that is a sintered body of the metal bonding composition of the present invention. Laminates are also an aspect of the invention. That is, in the metal bonding laminate of the present embodiment, the first metal bonding body having the first metal surface and the second metal bonding body having the second metal surface burn the metal bonding composition. It is bonded by a metal bonding material composed of a silver particle sintered layer obtained by bonding.

The types of the first object to be bonded and the second object to be bonded are not particularly limited, but it is preferable that the member has heat resistance to the extent that the composition for metal bonding is not damaged by the temperature at the time of heat sintering. It may be rigid or flexible. Further, the shape and thickness of the first object to be joined and the second object to be joined are not particularly limited and can be appropriately selected.

The type of the metal-bonded laminate is not particularly limited, but for example, a power semiconductor element (power device) is suitable. It is preferable that the first metal surface is a part of the semiconductor chip and the second metal surface is a part of the substrate. Further, from the viewpoint of obtaining high bonding strength, it is preferable that at least one of the first metal surface and the second metal surface is the surface of a base material or a plating layer composed of Cu, Ag or Au.

Further, the first bonded body and / or the second bonded body may be surface-treated in order to enhance the adhesion to the silver particle sintered layer. Examples of the surface treatment include a dry treatment such as corona treatment, plasma treatment, UV treatment, and electron beam treatment, and a method of providing a primer layer and a conductive paste receiving layer on the object to be bonded.

FIG. 3 is a schematic cross-sectional view showing the configuration of a power device which is an example of a metal-bonded laminate. In the power device shown in FIG. 3, the lower surface of the power semiconductor chip (second object to be bonded) 11 and the upper surface of the copper-clad insulating substrate (first object to be bonded) 13 are bonded by a metal bonding material 12. .. The main body of the power semiconductor chip 11 is made of Si, SiC, GaN, or the like, and the lower surface is Au-plated. The metal bonding material 12 is a silver particle sintered layer obtained by firing a composition for metal bonding containing silver particles and an organic component. The copper-clad insulating substrate 13 has a Cu layer 13b with Ag plating on both sides of a base material 13a made of silicon nitride or the like. Ag plating may not be applied to the Cu layer 13b.

A heat radiating material 14 and a heat sink 15 are attached under the copper-clad insulating substrate 13 in order to release the heat generated by the power semiconductor chip 11. The arrows in FIG. 3 indicate the heat release path. Further, a wire bond 16 is attached to the upper portion of the power semiconductor chip 11 to supply electric power to the power semiconductor chip 11.

The metal bonding material 12 composed of the silver particle sintered layer can mechanically, electrically, and thermally firmly bond the power semiconductor chip 11 to the copper-clad insulating substrate 13. When the silver particles are nanometer-sized particles, they can be sintered at a low temperature due to the melting point drop peculiar to the nanoparticles, and high conductivity and thermal conductivity close to those of metal foil can be realized. On the other hand, when solder is used as the metal bonding material 12 as in the conventional case, bonding is performed by melting the solder and then solidifying it. In this case, the bonding temperature of the metal bonding material 12 is the melting point of the solder, and the heat resistant temperature (usable temperature) of the metal bonding material 12 is lower than the melting point (bonding temperature) of the solder. Therefore, if an attempt is made to raise the heat resistant temperature of the metal bonding material 12, the bonding temperature will also increase. In the development of power devices, improvement in heat resistance and long-term reliability is required, and a silver particle sintered layer having higher reliability at a higher temperature than solder is preferably used. Here, the long-term reliability means that the mechanical properties of the metal joint are maintained for a long period of time. For example, the mechanical properties of the metal joint are unlikely to deteriorate even when a large number of heat cycles are applied. Means that.

The silver particle sintered layer is formed by, for example, the following steps (1) to (4) using the composition for metal bonding as a raw material.

<Process (1)>
In the above step (1), the metal bonding composition is applied to the first object to be bonded. Here, "coating" is a concept including both a case where the composition for metal bonding is applied in a planar shape and a case where the composition is applied in a linear shape (drawing). The shape of the coating film composed of the composition for metal bonding in a state before being applied and fired by heating can be a desired shape. Therefore, the metal bonding material (silver particle sintered layer) 12 after sintering by heating may be either planar or linear, and may be continuous or discontinuous on the first object to be bonded. There may be.

Examples of the method for applying the metal bonding composition include screen printing (metal mask printing), dispenser method, pin transfer method, dipping, spray method, bar coating method, spin coating method, inkjet method, and brush coating method. , The casting method, the flexographic method, the gravure method, the offset method, the transfer method, the hydrophobic pattern method, the syringe method and the like may be appropriately selected.

The viscosity of the metal bonding composition is, for example, preferably in the range of 0.01 to 5000 Pa · S, more preferably in the range of 0.1 to 1000 Pa · S, and further preferably in the range of 1 to 100 Pa · S. .. Within the viscosity range, a wide range of methods can be applied as a method for applying the metal bonding composition. The viscosity can be adjusted by adjusting the particle size of the silver particles, adjusting the content of the organic component, adjusting the blending ratio of each component, adding a thickener, and the like. The viscosity of the metal bonding composition can be measured, for example, with a cone plate type viscometer (for example, a rheometer MCR301 manufactured by Anton Pearl Co., Ltd.).

<Process (2)>
In the above step (2), the applied metal bonding composition (coating film) is heated and dried. The composition for metal bonding applied to the first object to be bonded usually has a large amount of organic components in order to secure coatability (printability) and pot life (pot life), and is used as it is. When the second object to be bonded is pressed and heat-sintered, many voids are generated in the generated silver particle sintered layer. Therefore, before pressing the second object to be bonded against the metal bonding composition, the metal bonding composition is heat-dried in the step (2) to reduce the content of the organic component in the metal bonding composition in advance. ..

The heating temperature (preliminary drying temperature) in the above step (2) is preferably 25 ° C. or higher and 100 ° C. or lower. Below 25 ° C., the dispersion medium in the metal bonding composition cannot be efficiently volatilized. If the temperature exceeds 100 ° C., the dispersion medium can be sufficiently volatilized, but a part of the dispersant adhering to the silver particles may also volatilize and sintering may start. In that case, a second cover is applied. When the joined body is pressed, it cannot be brought into close contact with each other, which makes it difficult to join without pressure. A more preferable lower limit of the pre-drying temperature is 50 ° C., and a further preferable lower limit is 60 ° C. The heating time in the above step (2) is not particularly limited, but it is preferably performed until the content of the organic component in the composition for metal bonding does not change. The method of heat-drying in the above step (2) is not particularly limited, and for example, a conventionally known oven or the like can be used.

<Process (3)>
In the above step (3), the second object to be bonded is pressed against the heat-dried composition for metal bonding. The second object to be joined is preferably pressed with a load of 1 MPa or less. If the pressing load exceeds 1 MPa, there is a concern that the second object to be joined, such as the power semiconductor chip 11, may be damaged (surface scratches or cracks). The pressing load is preferably 0.05 MPa or more. If the pressing load is less than 0.05 MPa, there is a risk of insufficient adhesion and peeling. The method of pressing the second object to be bonded in the above step (3) is not particularly limited, and various conventionally known methods can be applied, but the heat-dried metal bonding composition (dry coating film). Is preferably a method of uniformly pressurizing.

<Process (4)>
In the above step (4), the composition for metal bonding is heated and sintered to form a silver particle sintered layer. In the preheating in the step (2), the dispersion medium mainly volatilizes among the organic components, and the dispersant and the like adhered to the silver particles remain in the composition for metal bonding, but by the heating in the step (4). , Most or all of the organic components in the metal bonding composition volatilize. In the present embodiment, when the composition for metal bonding contains a binder component, the binder component is also sintered from the viewpoint of improving the strength of the bonding material and the bonding strength between the members to be bonded. Depending on the case, the firing conditions may be controlled to remove all the binder components, with the main purpose of adjusting the viscosity of the metal bonding composition for application to various printing methods. The silver particle sintered layer should have a small residual amount of the organic component in terms of obtaining high bonding strength, and preferably does not substantially contain the organic component. However, the organic component is not impaired within the range of the effect of the present invention. It does not matter if a part of is left.

Further, by heating in the step (4), not only the silver particles are bonded to each other in the composition for metal bonding, but also the vicinity of the interface between the first bonded body and the second bonded body and the silver particle sintered layer. Then, the metal diffuses between adjacent layers. As a result, a strong bond is formed between the first object to be bonded and the silver particle sintered layer, and between the second object to be bonded and the silver particle sintered layer.

In the above step (4), the first joined body and the second joined body may be joined while pressurizing, but the first joined body and the second joined body are joined together. It may be joined under no pressure. Joining under no pressurization is excellent in productivity because pressurization and heating are not performed at the same time. In the case of bonding under no pressure, voids are likely to be generated in the silver particle sintered layer due to volatilization of organic components when the metal bonding composition is heated and sintered. Since the content of the organic component in the metal bonding composition is adjusted by the pre-drying in step (2), the generation of voids is suppressed even when bonding under no pressure, and silver particles having high bonding strength. A sintered layer (metal bonding material) can be obtained.

The heating temperature in the step (4) is not particularly limited as long as the silver particle sintered layer can be formed, but is preferably 200 to 300 ° C. When the heating temperature is 200 to 300 ° C., organic components and the like can be removed by evaporation or decomposition while preventing damage to the first bonded body and the second bonded body, and high bonding strength can be obtained. Further, when heating, the temperature may be raised or lowered stepwise, and it is preferable to raise the temperature from room temperature. The heating time in the step (4) is not particularly limited, and may be adjusted so that sufficient bonding strength can be obtained according to the heating temperature. The method of heating in the step (4) is not particularly limited, and for example, a conventionally known oven or the like can be used. The heating in the step (4) may be performed in an air atmosphere or a nitrogen atmosphere.

The silver particle sintered layer is preferably a dense sintered body from the viewpoint of obtaining a mechanically, electrically and thermally strong bonded state, and specifically, the void ratio of the silver particle sintered layer. Is preferably 20% by volume or less. According to the composition for metal bonding of the present embodiment, a silver particle sintered layer having a void ratio of 5 to 20% by volume can be easily formed even when bonded under no pressure.

The thickness of the silver particle sintered layer is, for example, 10 to 200 μm, more preferably 20 to 100 μm. The thickness of the silver particle sintered layer can be easily controlled by the thickness of the coating film.

The application of the metal-bonded laminate of the present embodiment is not particularly limited, but when the metal-bonded laminate is a power semiconductor element (power device), it can be used for an electric control device. An electrical control device including the metal-bonded laminate of the present invention is also an aspect of the present invention. Electric control equipment is used for electric control (electric power switching) in fields such as in-vehicle, electric railway, industrial use, consumer (home appliances), and electric power (power generation).

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Example 1>
While sufficiently stirring 2.0 g of 3-methoxypropylamine with a magnetic stirrer, 3.0 g of silver oxalate was added to thicken the mixture. The obtained viscous substance was placed in a constant temperature bath and reacted, and then 10 g of levulinic acid was added and further reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the nanosilver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of nano-silver particles obtained was 2.1 g. The obtained nano-silver particles and micron silver particles (Ag-HWQ2.5 manufactured by Fukuda Metal Foil Powder Industry Co., Ltd.) were mixed at a mass ratio of 7: 3, and hexylcarbitol (dispersion medium) and ricinolic acid (additive) were mixed. ) Was mixed at a ratio of 9: 1 and mixed so that the total amount of nano-silver particles and micron silver particles and the mass ratio of the mixed solution were 9: 1 and mixed to obtain a composition for metal bonding. It was.

<Example 2>
A composition for metal bonding was prepared in the same manner as in Example 1 except that the mixing ratio of the nano-silver particles and the micron-silver particles was changed to 8: 2.

<Example 3>
A composition for metal bonding was prepared in the same manner as in Example 1 except that the mixing ratio of the nano-silver particles and the micron-silver particles was changed to 9: 1.

<Example 4>
While sufficiently stirring 2.0 g of 3-methoxypropylamine with a magnetic stirrer, 3.0 g of silver oxalate was added to thicken the mixture. The obtained viscous substance was placed in a constant temperature bath and reacted, and then 10 g of levulinic acid was added and further reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the nanosilver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of nano-silver particles obtained was 2.1 g. Further, 5.0 g of 3-methoxypropylamine, 0.5 g of dodecylamine and 6.0 g of diglycolamine were sufficiently stirred with a magnetic stirrer, and 4.5 g of silver oxalate was added to thicken the viscosity. The obtained viscous substance was placed in a constant temperature bath and reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the submicron silver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of submicron silver particles obtained was 3.0 g. The obtained nano-silver particles and submicron silver particles were mixed at a mass ratio of 5: 5, and a mixed solution of hexylcarbitol (dispersion medium) and ricinolic acid (additive) at a ratio of 9: 1 was mixed with the nano-silver particles. And submicron silver particles were added so as to have a mass ratio of 9: 1 to the mass ratio of the mixed solution, and the mixture was stirred and mixed to obtain a composition for metal bonding.

<Example 5>
The same procedure as in Example 4 was carried out except that the maximum temperature of firing was set to 250 ° C. in (1) tensile test, (2) method for producing a metal bonded laminate and measurement of bonding strength, which will be described later.

<Example 6>
While sufficiently stirring 3.0 g of 3-methoxypropylamine with a magnetic stirrer, 3.0 g of silver oxalate was added to thicken the mixture. The obtained viscous substance was placed in a constant temperature bath and reacted, and then 9 g of dodecylamine was added and further reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the nanosilver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of nano-silver particles obtained was 2.1 g. Further, 5.0 g of 3-methoxypropylamine, 0.5 g of dodecylamine and 10.0 g of diglycolamine were sufficiently stirred with a magnetic stirrer, and 4.5 g of silver oxalate was added to thicken the viscosity. The obtained viscous substance was placed in a constant temperature bath and reacted, and then 15 g of dodecylamine was added and further reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the submicron silver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of submicron silver particles obtained was 3.0 g. The obtained nano-silver particles and submicron silver particles were mixed at a mass ratio of 4: 6, and a mixed solution of hexylcarbitol (dispersion medium) and ricinolic acid (additive) at a ratio of 9: 1 was mixed with the nano-silver particles. And submicron silver particles were added so as to have a mass ratio of 9: 1 to the mass ratio of the mixed solution, and the mixture was stirred and mixed to obtain a composition for metal bonding.

<Example 7>
While sufficiently stirring 5.0 g of 3-methoxypropylamine with a magnetic stirrer, 3.0 g of silver oxalate was added to thicken the mixture. The obtained viscous substance was placed in a constant temperature bath and reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the nanosilver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of nano-silver particles obtained was 2.0 g. Further, while sufficiently stirring 15.0 g of diglycolamine with a magnetic stirrer, 4.5 g of silver oxalate was added to thicken the viscosity. The obtained viscous substance was placed in a constant temperature bath and reacted to obtain a suspension. Next, in order to replace the dispersion medium of the suspension, methanol was added and stirred, and then the submicron silver particles were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. The amount of submicron silver particles obtained was 3.0 g. The obtained nano-silver particles and submicron silver particles were mixed at a mass ratio of 4: 6, and a mixed solution of hexylcarbitol (dispersion medium) and ricinolic acid (additive) at a ratio of 9: 1 was mixed with the nano-silver particles. And submicron silver particles were added so as to have a mass ratio of 9: 1 to the mass ratio of the mixed solution, and the mixture was stirred and mixed to obtain a composition for metal bonding.
In the firing atmosphere in (1) tensile test, (2) method for producing a metal bonded laminate, and measurement of bonding strength, which will be described later, nitrogen was flowed to reduce the oxygen concentration to 300 ppm or less.

<Comparative example 1>
A composition for metal bonding was prepared in the same manner as in Example 1 except that the mixing ratio of the nano-silver particles and the micron-silver particles was changed to 6: 4.

<Comparative example 2>
A composition for metal bonding was prepared in the same manner as in Example 1 except that Solsperse 54000 (manufactured by Japan Lubrizol Co., Ltd.) was used instead of ricinoleic acid.

[Evaluation test]
The following evaluation test was carried out using the metal bonding compositions prepared in Examples and Comparative Examples. The results are shown in Table 1.

(A) Measurement of average particle size of silver particles From photographs taken at 200,000 times using a scanning electron microscope (model number: S4800) manufactured by Hitachi, the arithmetic average value of the particle size of about 50 to 100 particles is obtained. The average particle size of nano-silver particles, submicron silver particles, and micron silver particles was obtained by the calculation method.

(B) Measurement of Content of Organic Components Using a thermal analyzer (differential thermal balance: TG-DTA) manufactured by Rigaku Co., Ltd., 20 mg of a sample of the composition for metal bonding is placed in the air at a heating rate of 10 ° C./min. The temperature was raised to 550 ° C., and the volatile matter at that time was taken as the content of the organic component.

(1) Tensile Test Using a dumbbell-shaped No. 7 metal mask (plate thickness 90 μm) specified in JIS K 6251, the metal bonding composition was printed on a slide glass. As a pre-drying, the printed metal bonding composition was placed in an oven set at 70 ° C. and dried for 30 minutes. A slide glass was placed on the dried composition for metal bonding, and the slide glass was placed in a reflow furnace (manufactured by Shinapex Corporation) for firing treatment. The firing treatment in the reflow furnace was carried out in an air atmosphere, and the temperature was raised from room temperature to a maximum temperature of 275 ° C. at a heating rate of 3.8 ° C./min and then maintained at 275 ° C. for 60 minutes. During the firing process, no pressurization was performed and no pressurization was performed. The calcined composition for metal bonding was taken out from the reflow furnace and then peeled off from the slide glass to prepare a test piece for a tensile test.

The tensile test was carried out with a universal tensile tester 5969 manufactured by Instron at a measurement speed of 0.72 mm / min. The tensile stress at break and the elongation at break (strain) when the test piece broke were measured. Further, the slope in the obtained stress-strain curve (SS curve) in the range of 0.05 to 0.25% was calculated from the approximate formula and used as Young's modulus.

(2) Method for manufacturing metal bonded laminate and measurement of bonding strength Silver-plated DBC substrate (area: 30 mm x 40 mm, cross-sectional structure: Cu plate / SiN base material / Cu plate = 0.2 mm thickness / 0.32 mm thickness / A metal bonding composition was applied to an 11 mm square using a metal mask (plate thickness 90 μm). As a preliminary drying, the applied metal bonding composition was placed in an oven set at 70 ° C. and dried for 30 minutes. A gold-sputtered Si chip (bottom area: 5 mm × 5 mm or 10 mm × 10 mm) was laminated on the dried composition for metal bonding and pressed at 0.2 MPa. Then, the obtained laminate was placed in a reflow furnace (manufactured by Shinapex Corporation) and fired. The firing treatment in the reflow furnace was carried out in an air atmosphere, and the temperature was raised from room temperature to a maximum temperature of 275 ° C. at a heating rate of 3.8 ° C./min, and then the temperature was raised, and then the temperature was maintained at 275 ° C. for 60 minutes. During the firing process, no pressurization was performed and no pressurization was performed. After the completion of the firing treatment, a metal bonding laminate obtained by bonding Si chips subjected to gold sputtering to a silver-plated DBC substrate with a metal bonding material composed of a sintered metal bonding composition was obtained.

The bonding strength of the metal bonding laminate was measured at room temperature using a bond tester (manufactured by Reska). As a test piece, a stack of 5 mm × 5 mm Si chips was used. The load cell used for the bond tester is 100 kgf, and the upper limit of measurement is 40 MPa when a 5 mm × 5 mm chip is used.

(3) Measurement of void ratio The metal-bonded laminate obtained in (2) above is subjected to an ultrasonic flaw detector manufactured by Nippon Clout Kramer (ultrasonic frequency: 80 MHz, probe diameter: φ3 mm, focal length PF =. Voids were confirmed at 10 mm). It was finely adjusted to the place where the reflection peak at the junction interface was the highest, and measured with the material sound velocity = Si: 9600 mm / s and Gain = 65 dB. The threshold value of the reflection intensity was set to 55%, and the threshold value higher than that was regarded as a void. The area of the void obtained by binarizing with the threshold value was calculated using software, and the void ratio was calculated. As the test piece, one in which 10 mm × 10 mm Si chips were laminated was used.

(4) Heat cycle test The metal-bonded laminate obtained in (2) above is placed in a thermal shock tester (manufactured by Hutec) and held at -40 ° C and 200 ° C for 10 minutes, respectively, as one cycle. It was taken out after 1000 cycles. After taking out, the void rate of (3) above was measured, and the amount of increase in the void rate with respect to 0 cycles (initial void rate) was calculated. As the test piece, one in which 10 mm × 10 mm Si chips were laminated was used.

(5) Printability The printability of the composition for metal bonding is evaluated by printing with a hand-printing printing machine using a plastic squeegee (manufactured by Toyo Giken Co., Ltd.) and a metal mask plate (manufactured by Murakami Co., Ltd.). did.
〇: Good △: Printing is possible, but stringing occurs ×: High viscosity, printing is not possible

(6) Pot life The pot life of the composition for metal bonding was printed by a hand-printing printing machine in the same manner as in the above evaluation of (5) printability, and evaluated according to the following criteria.
〇: Can be printed after being left for 5 hours in the released state △: Can be printed after being left for 1 to 4 hours in the released state ×: Cannot be printed after being left for 1 hour in the released state

As can be seen from Table 1, all of the metal bonding compositions of Examples 1 to 7 had a tensile stress at break of 100 MPa or more when fired at 275 ° C., and were excellent in printability and pot life. .. It was confirmed that all of the metal bonding laminates produced by using such a metal bonding composition had a measured value of bonding strength of 40 MPa, which is the upper limit of measurement, and had a high bonding strength of 40 MPa or more. Further, a heat cycle test was carried out on the metal bonding laminates prepared by using the metal bonding compositions of Examples 1 to 7, and the void ratio after the test (= initial void ratio + void increase amount after heat cycle). Was 40% or less in each case, and it was confirmed that they had high joining reliability.

On the other hand, the metal bonding compositions of Comparative Examples 1 and 2 had a tensile breaking stress of less than 100 MPa when fired at 275 ° C., and were produced using the metal bonding compositions of Comparative Examples 1 and 2. When a heat cycle test was carried out on the metal-bonded laminate, the void ratio increased significantly after the test and exceeded 40%. It is considered that this is because cracks were generated by the heat cycle test. Further, in the metal bonding laminate produced by using the metal bonding composition of Comparative Example 2, the void ratio after the test was as high as 75%, and the bonding strength was as low as 31 MPa.

11 Power semiconductor chip 12 Metal bonding material 13 Copper-clad insulation substrate 13a Base material 13b Cu layer 14 Heat sink 15 Heat sink 16 Wire bond 51, 53 Slide glass 52 Metal bonding composition 54 Test piece

Claims (3)

A composition for metal bonding used for bonding metal surfaces by firing.
The composition for metal bonding contains silver particles and a dispersion medium, and contains silver particles and a dispersion medium.
The silver particles, at least a part of the surface are those with an organic protective layer comprising an amine having 4 to 12 carbon atoms, and the nanoparticles having an average particle diameter 45～99Nm, the average particle size of 100~999nm It contains submicron particles and
The average particle size is an arithmetic mean value of the particle size of 50 to 100 silver particles measured from a photograph taken at 200,000 times using a scanning electron microscope.
The ratio of the nanoparticles to the total mass of the nanoparticles and the submicron particles is 70% or less.
The feature is that the tensile breaking stress is 100 MPa or more when the coating film formed by printing on a glass substrate and firing at 275 ° C. without pressure is measured using a test piece obtained by peeling it from the glass substrate. Composition for metal bonding. The composition for metal bonding according to claim 1, wherein the mass ratio of the nanoparticles to the submicron particles is 4: 6 to 7: 3. The composition for metal bonding according to claim 1 or 2, wherein the dispersion medium contains hexylcarbitol.

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