TW201911989A - Method for manufacturing metal bonded laminate - Google Patents

Abstract

The present invention provides a method for producing a metal bonded laminate, which enables the achievement of high bonding strength, while ensuring good handling properties of a bonding composition. The present invention is a method for producing a metal bonded laminate where a first body to be bonded and a second body to be bonded are bonded to each other by means of a silver particle sintered layer; and this method comprises a step (1) wherein a bonding composition, which contains silver particles and an organic component, is applied to the first body to be bonded, a step (2) wherein the applied bonding composition is heated and dried, a step (3) wherein the second body to be bonded is pressed against the heated and dried bonding composition, and a step (4) wherein the bonding composition is sintered by means of heating, thereby forming the silver particle sintered layer. With respect to this method for producing a metal bonded laminate, the content of the organic component in the bonding composition that is heated and dried in the step (2) is 4% by mass or more.

Description

Method for manufacturing metal bonded laminate

The present invention relates to a method of producing a metal bonded laminate.

In order to perform mechanical, electrical, and/or thermal bonding of the metal parts, a bonding material such as solder, a conductive adhesive, a silver paste, or an anisotropic conductive film is used. These joining materials are used not only for joining metal parts but also for joining ceramic parts, resin parts, and the like. Examples of the use of the bonding material include a use of bonding a light-emitting element such as a light emitting diode (LED) to a substrate, and bonding the semiconductor wafer to the substrate, and further bonding the substrates to the heat release. Use on components, etc.

Patent Document 1 discloses a bonding material comprising a silver paste in which silver fine particles and a solvent are mixed, and a solvent is a diol, and a mixture of one or more methyl groups is mixed. Triol is used as an additive. [Prior Art Document] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2016-8332

[Problems to be solved by the invention]

The present inventors conducted research and development on a bonding composition containing silver particles in order to use a silver particle sintered layer as a bonding material. In addition, it has been found that by using an organic component such as a dispersion medium in the composition for bonding, it is possible to ensure good coatability (printability) or pot life (useable time) of the composition for bonding, but it is used. There is room for improvement in terms of voids or peeling at the time of firing of the sintered silver particles, and the desired joint strength cannot be obtained.

The present invention has been made in view of the above circumstances, and an object of the invention is to provide a method for producing a metal bonded laminate which ensures good workability of a bonding composition and obtains high joint strength. [Means for solving the problem]

The inventors of the present invention have conducted various studies on a method for producing a metal bonded laminate which ensures good workability of the composition for bonding and which has high joint strength, and has focused on the organic component contained in the composition for bonding. In addition, the inventors of the present invention conducted an intensive study and found that the content of the organic component is maintained at 4% by mass or more before the second component to be bonded is applied to the bonding composition applied to the first to-be-joined body. Heating and drying treatment, thereby ensuring coatability (printability) or pot life (useable time) of the composition for bonding, and suppressing void ratio (porosity) in the sintered layer of silver particles, thereby obtaining high joint strength, thereby obtaining high joint strength The present invention has been completed.

The method for producing a metal bonded laminate according to the present invention is a method for producing a metal bonded laminate in which a first bonded body and a second bonded body are joined by a silver sintered layer, and is characterized by comprising the following steps: (1) Applying a bonding composition containing silver particles and an organic component to the first to-be-joined body; and heating and drying the applied bonding composition in step (2); and step (3) The second joined body is pressed against the heat-dried bonding composition; and in the step (4), the bonding composition is heated and sintered to form the silver particle sintered layer, and the The content of the organic component in the bonding composition which is dried by heating in the step (2) is 4% by mass or more.

The void ratio of the sintered silver particle layer is preferably 20% by volume or less.

In the step (2), it is preferred to carry out heat drying at a temperature of 25 ° C or more and 100 ° C or less.

In the step (3), it is preferable that the second joined body is pressed with a load of 1 MPa or less.

In the step (4), it is preferred that the first joined body and the second joined body are joined without pressure. [Effects of the Invention]

According to the present invention, it is possible to provide a method for producing a metal bonded laminate which ensures good workability of the joining composition and which has high joint strength.

The method for producing a metal bonded laminate according to the present embodiment is a method for producing a metal bonded laminate in which a first joined body and a second joined body are joined by a silver sintered layer, and is characterized by comprising the steps (1) a bonding composition containing silver particles and an organic component to the first object to be joined, a step (2) of heating and drying the applied composition, and a step (3); The second object to be joined is pressed to the bonding composition that is dried by heating; and in the step (4), the bonding composition is heated and sintered to form the sintered layer of silver particles, and The content of the organic component in the bonding composition which is dried by heating in the step (2) is 4% by mass or more.

The metal bonded laminate produced in the present embodiment is obtained by joining a first joined body and a second joined body by a sintered layer of silver particles. The type of the first to-be-joined body and the second to-be-joined body is not particularly limited, and it is preferably a member having heat resistance that is not damaged by the temperature at the time of heating and sintering of the bonding composition, and may be rigid. ) can also be flexible. Further, from the viewpoint of obtaining high joint strength, the joint surface of the first joined body and the second joined body preferably contains a metal such as Cu, Ag or Au. Further, the shape and thickness of the first joined body and the second joined body are not particularly limited, and can be appropriately selected.

Further, the first joined body and/or the second joined body may be subjected to surface treatment in order to improve adhesion to the sintered layer of silver particles. Examples of the surface treatment include dry treatment such as corona treatment, plasma treatment, ultraviolet (Ultra Violet (UV) treatment, and electron beam treatment, or providing an undercoat layer or a conductive paste receiving layer on the member to be joined. Method etc.

As the metal bonded laminate produced in the present embodiment, for example, a power semiconductor element (power device) can be cited. FIG. 1 is a schematic cross-sectional view showing a configuration of a power device as an example of a metal bonded laminate. In the power device shown in FIG. 1, the lower surface of the power semiconductor wafer (second bonded body) 11 is bonded to the upper surface of the copper-clad insulating substrate (first bonded body) 13 by the bonding material 12. The main body of the power semiconductor wafer 11 contains Si, SiC, GaN, or the like, and Au is plated on the lower surface. The bonding material 12 is a sintered silver particle layer obtained by firing a bonding composition containing silver particles and an organic component. The copper-clad insulating substrate 13 has a Cu layer 13b plated with Ag on both surfaces of a substrate 13a including tantalum nitride or the like. The Cu layer 13b is sometimes not plated with Ag.

A heat releasing material 14 and a heat sink 15 are attached below the copper clad insulating substrate 13 to discharge heat generated in the power semiconductor wafer 11. The arrows in Figure 1 indicate the hot release path. Further, a wire bonding wire 16 is attached to the upper portion of the power semiconductor wafer 11 to supply electric power to the power semiconductor wafer 11.

The bonding material 12 including the sintered silver particle layer can bond the power semiconductor wafer 11 to the copper-clad insulating substrate 13 mechanically, electrically, and thermally. In the case where the silver particles are nanoparticles having a nanometer size, the melting point which is peculiar to the nanoparticles can be lowered and sintered at a low temperature, and high conductivity or thermal conductivity close to the metal foil can be achieved. On the other hand, as in the case of using the solder as the bonding material 12 as before, bonding is performed by melting the solder and solidifying it. In this case, the bonding temperature of the bonding material 12 is the melting point of the solder, and the heat resistant temperature (temperature that can be used) of the bonding material 12 is lower than the melting point (bonding temperature) of the solder. Therefore, if the heat resistant temperature of the bonding material 12 is to be increased, the bonding temperature is also increased. In the development of a power device, heat resistance or long-term reliability is required to be improved, and a silver particle sintered layer excellent in reliability at a high temperature compared to solder is preferably used. Here, the term "long-term reliability" means that the mechanical properties of the bonded body are maintained for a long period of time. For example, even if a plurality of thermal cycles are applied, it is difficult to reduce the mechanical properties of the bonded body.

The silver particle sintered layer is formed by using the bonding composition as a raw material and passing through the steps (1) to (4). First, the bonding composition used in the above step (1) will be described.

<Construction Composition> The composition for bonding is not particularly limited as long as it contains silver particles and an organic component, and is preferably in a paste form for easy application. Further, in addition to the silver particles, particles having a higher ionization sequence than hydrogen, that is, particles such as gold, copper, platinum, or palladium may be used in combination to prevent migration.

The average particle diameter of the silver particles is preferably from 1 μm to 20 μm. By using silver particles having an average particle diameter of 1 μm to 20 μm, volume shrinkage due to sintering can be reduced, and a homogeneous and dense bonding material 12 can be obtained. When small particles having an average particle diameter of less than 1 μm are used, sintering is performed at a low temperature. However, as the sintering progresses between the particles, the volume shrinkage increases as the average particle diameter increases, and the joined body cannot follow the volume shrinkage. Worry. In this case, defects such as voids are generated in the bonding material 12, and the bonding strength and reliability of the bonding material 12 are lowered. On the other hand, when particles having an average particle diameter of more than 20 μm are used, sintering at a low temperature is hardly progressed, and there is a concern that large voids formed between the particles remain after sintering.

The average particle diameter of the silver particles can be measured by dynamic light scattering (Dynamic Light Scattering), small-angle X-ray scattering, and wide-angle X-ray diffraction. In the present specification, the "average particle diameter" means a dispersed median diameter. Further, as another method of measuring the average particle diameter, a method of calculating an arithmetic mean value of particle diameters of 50 to 100 particles based on a photograph taken using a scanning electron microscope or a transmission electron microscope is exemplified.

The bonding composition may also contain metal fine particles having a particle diameter smaller than that of the silver particles. The metal fine particles may be dispersed in the bonding composition from the silver particles, or may be attached to at least a part of the surface of the silver particles. Examples of the metal include gold, silver, copper, nickel, ruthenium, tin, iron, and a platinum group element (ruthenium, rhodium, palladium, iridium, iridium, and platinum). Among them, gold, silver, copper and platinum are preferred, and silver is more preferred. These metals may be used singly or in combination of two or more.

The average particle diameter of the metal fine particles is not particularly limited as long as it does not impair the effects of the present invention, and among the metal fine particles, a nanometer size at which the melting point is lowered is preferable, and more preferably 1 nm to 100 nm. When the average particle diameter of the metal fine particles is 1 nm or more, a bonding composition capable of forming a good bonding material 12 is obtained, and the production cost of the metal fine particles is not high and practical. On the other hand, when it is 100 nm or less, the dispersibility of the metal fine particles is less likely to change with time.

The organic component is not particularly limited, and may be used in addition to a dispersion medium to adjust the dispersibility of the silver particles, or the adhesion, adhesion, drying property, surface tension, and coatability (printability) of the composition for bonding. Additives and the like used for the purpose.

Examples of the dispersion medium include organic solvents such as hydrocarbons, alcohols, and carbitols. The dispersion medium is preferably difficult to volatilize during the step of applying the composition for bonding, and is preferably difficult to volatilize at room temperature.

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

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

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

Examples of the alicyclic hydrocarbons include limonene, dipentene, terpinene, terpinene (also known as terpinene), nesol, and cinene. Orange flavor, terpinolene, terpinolene (also known as terpinolene), phellandrene, menthadiene, terebene, dihydroanimate Dihydrocymene, γ-terpinene (moslene), isodecene, isonene (also known as isoterpene), crithmene, kautschin, leukocholium (cajeputene), bulimen, pinene, turpentine, menthane, pinane, terpene, cyclohexane, and the like.

The alcohol is a compound containing one or more OH groups in a molecular structure, and examples thereof include an aliphatic alcohol, a cyclic alcohol, and an alicyclic alcohol, and they may be used alone or in combination of two or more. Further, a part of the OH group may be derived from an ethenyloxy group or the like within the range which does not impair the effects of the present invention.

Examples of the aliphatic alcohol include heptanol, octanol (1-octanol, 2-octanol, 3-octanol, etc.), decyl alcohol (1-nonanol, etc.), lauryl alcohol, and fourteen. A saturated or unsaturated C6-30 aliphatic alcohol such as a base alcohol, cetyl alcohol, 2-ethyl-1-hexanol, octadecyl alcohol, hexadecenol or oleyl alcohol.

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

Examples of the alicyclic alcohol include a cycloalkanol such as cyclohexanol, terpineol (including an α, β, γ isomer, or a mixture of any of these), and dihydroterpineol. Enol (monoterpene alcohol, etc.), dihydroterenol, myrtenol, sobrerol, menthol, carveol, perillyl alcohol , pine carveol (pinocarveol), sobrerol (sobrerol), waffenol (verbenol) and the like.

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

The initial content in the case where the dispersion composition contains a dispersion medium may be adjusted according to characteristics required for viscosity or the like, and the initial content of the dispersion medium in the bonding composition is preferably from 1% by mass to 30% by mass. When the initial content of the dispersion medium is from 1% by mass to 30% by mass, the effect of adjusting the viscosity in a range that is easy to use as a composition for bonding can be obtained. A more preferable initial content of the dispersion medium is from 1% by mass to 20% by mass, and further preferably, the initial content is from 4% by mass to 15% by mass.

Examples of the additive for improving the dispersibility of the silver particles include an amine, a carboxylic acid, a polymer dispersant, and an unsaturated hydrocarbon. The amine or the carboxylic acid is adsorbed to the surface of the silver particles with a moderate strength and prevents the silver particles from coming into contact with each other, thereby contributing to the stability of the silver particles in the storage state. The additive adsorbed on the surface of the silver particles is transferred and/or volatilized from the surface of the particles upon heating, whereby it is considered that the silver particles are promoted to be bonded to each other and to the substrate. The polymer dispersant is allowed to adhere to at least a part of the silver particles, whereby the low-temperature sinterability of the silver particles is not lost, and the dispersion stability can be maintained.

It is preferred that the organic component adheres to at least a part of the surface of the silver particle (that is, at least a part of the surface of the silver particle is coated with an organic protective layer containing an organic component), and the organic component (organic protective layer) contains an amine. It is preferable to provide an organic protective layer on at least a part of the surface of the metal particles to stably store the nano-sized silver particles showing the melting point lowering ability. Here, since the amine is adsorbed on the surface of the silver particles with a moderate strength, it can be suitably used as an organic protective layer.

The amine is not particularly limited, and examples thereof include an alkylamine such as an oleylamine, a butylamine, a pentylamine, a hexylamine or a hexylamine (a linear alkylamine which may have a side chain), and N. Alkoxyamines such as -(3-methoxypropyl)propane-1,3-diamine, 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine a primary amine such as a cycloalkylamine such as cyclopentylamine or cyclohexylamine; an allylamine such as aniline; a secondary amine such as dipropylamine, dibutylamine, piperidine or hexamethyleneimine; a tertiary amine such as propylamine, dimethylpropanediamine, cyclohexyldimethylamine, pyridine or quinoline; a carbon number of 2 to 20 such as octylamine or the like, preferably a carbon number of 4 ~7 amine. Specific examples of the amine having 4 to 7 carbon atoms include heptylamine, butylamine, pentylamine, and hexylamine. Since the amine having 4 to 7 carbon atoms is transferred and/or volatilized at a relatively low temperature, the low-temperature sinterability of the silver particles can be sufficiently utilized. Further, the amine may be linear, may be branched, or may have a side chain.

Further, it is considered that the organic components are changed to an anion or a cation when chemically or physically bonded to the silver particles. In the present embodiment, ions or complexes derived from the organic components are also included in the embodiment. Among the organic ingredients.

The amine may also be a compound containing a functional group other than an amine such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group or a mercapto group. Further, the amines may be used alone or in combination of two or more. Further, the boiling point at normal 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, caproic acid, acrylic acid, octanoic acid, levulinic acid, oleic acid and the like. A carboxyl group of a part of the carboxylic acid may also form a metal ion and a salt. Further, the metal ions may contain two or more kinds of metal ions.

The carboxylic acid may be a compound containing a functional group other than a carboxyl group such as an amine group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group or a fluorenyl group. In this case, the number of carboxyl groups is preferably at least the number of functional groups other than the carboxyl group. Further, the carboxylic acids may be used alone or in combination of two or more. Further, the boiling point at normal temperature is preferably 300 ° C or lower, more preferably 250 ° C or lower.

Further, the amine forms a guanamine group with the carboxylic acid. The guanamine group is also moderately adsorbed on the surface of the silver particles, and therefore the amide group may be contained in the organic component.

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

As the polymer dispersant, a commercially available polymer dispersant can be used. As a commercially available polymer dispersant, for example, SOSOLPERS 11200, Sonupas 13940, Sonupas 16000, Sonupas 17000, Sonupas 18000, Sonupas 20000, Sonupas 24000, Sonupas 26000, Sonupas 27000, Sonupas 28000 (above, manufactured by Lubrizol, Japan); DISPERBYK 142, Di Spabike 160, Despabike 161, Despabike 162, Despabike 163, Despabike 166, Despabike 170, Despabike 180, Diss Pabike 182, Despabike 184, Disparbike 190, Despabike 2155 (above, BYK-Chemie Japan); Efka (EFKA)-46 EFKA-47, EFKA-48, EFKA-49 (above, manufactured by EFKA Chemical Co., Ltd.); polymer 100, polymer 120, polymer 150, polymer 400, polymer 401, polymerization 402, polymer 403, polymer 450, polymer 451, polymer 452, polymer 453 (above, manufactured by EFKA Chemical Co., Ltd.); Ajisper PB711, Ajispa PA111, Ajispa PB811, Ajispa PW911 (above, Ajinomoto); Floren DOPA-15B, Floren DOPA- 22. Floren DOPA-17, Floren TG-730W, Floren G-700, Floren TG-720W (above, manufactured by Kyoeisha Chemical Industry Co., Ltd.), and the like. From the viewpoints of low-temperature sinterability and dispersion stability, it is preferable to use Sonupas 11200, Sonupas 13940, Sonupas 16000, Sonupas 17000, Sonupas 18000, Sonupa 28000, Despabike 142 or Despabike 2155.

The content of the polymer dispersant is preferably from 0.1% by mass to 15% by mass. When the content of the polymer dispersant is 0.1% by mass or more, the dispersion stability of the obtained bonding composition is good, but when the content is too large, the bondability is lowered. From such a viewpoint, a more preferable content of the polymer dispersant is 0.03% by mass to 3% by mass, and further preferably a content of 0.05% by mass to 2% by mass.

The silver particles can be obtained, for example, by mixing a metal ion source with a dispersing agent and using a reduction method. In this case, the amount of the organic component can be controlled by adjusting the amount of the added dispersant or reducing agent or the like.

In order to adjust the amount of the organic component adhering to the silver particles, heat treatment with silver particles, washing with an acid (sulfuric acid, hydrochloric acid, nitric acid, or the like), washing with a fat-soluble organic solvent such as acetone or methanol, or the like can be used. Furthermore, the organic component can be removed more efficiently by applying ultrasonic waves during cleaning.

Examples of the unsaturated hydrocarbon include ethylene, acetylene, benzene, acetone, 1-hexene, 1-octene, 4-vinylcyclohexene, cyclohexanone, decene alcohol, and allyl alcohol. , oleyl alcohol, 2-palmitoleic acid, petroselinic acid, oleic acid, anti-oleic acid, tianshic acid, ricinoleic acid, linoleic acid , linolelaidic acid, linolenic acid, arachidonic acid, acrylic acid, methacrylic acid, gallic acid, salicylic acid, and the like.

Among the unsaturated hydrocarbons, unsaturated hydrocarbons having a hydroxyl group are suitably used. The hydroxyl group is easily disposed on the surface of the silver particles, so that aggregation of the silver particles can be suppressed. Examples of the unsaturated hydrocarbon having a hydroxyl group include a terpene alcohol, an allyl alcohol, an oleyl alcohol, a ginsolic acid, ricinoleic acid, gallic acid, and salicylic acid. The unsaturated fatty acid having a hydroxyl group is preferably, for example, tianshi acid, ricinoleic acid, gallic acid, salicylic acid or the like.

Further, in the range in which the effects of the present invention are not impaired, the organic component may include an oligomer component, a resin component, an organic solvent (a part of the solid component may be dissolved or dispersed), and an interface which functions as a binder. Active agent, thickener, surface tension modifier, and the like.

Examples of the resin component include a polyester resin, a polyurethane resin such as a blocked isocyanate, a polyacrylate resin, a polypropylene phthalamide resin, a polyether resin, and a melamine resin. These may be used alone or in combination of two or more.

The organic solvent is excluded as the dispersion medium, and examples thereof include methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, 1,3-propanediol, and 1,2- Propylene glycol, 1,4-butanediol, 1,2,6-hexanetriol, 1-ethoxy-2-propanol, 2-butoxyethanol, ethylene glycol, diethylene glycol, triethyl Polyethylene glycol, propylene glycol, dipropylene glycol, and tripropylene glycol having a weight average molecular weight of 200 or more and 1,000 or less, and a polypropylene glycol having a weight average molecular weight of 300 or more and 1,000 or less, N, N-di Methylformamide, dimethylhydrazine, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, glycerin, acetone, etc., which may be used alone or in combination More than one species.

Examples of the thickener include clay minerals such as clay, bentonite, and hectorite, polyester emulsion resins, acrylic emulsion resins, and polyurethane emulsion resins. Emulsions such as segment isocyanate, cellulose derivatives such as methyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, xanthan gum, melon A polysaccharide such as guar gum may be used alone or in combination of two or more.

The surfactant is not particularly limited, and any of an anionic surfactant, a cationic surfactant, and a nonionic surfactant may be used, and examples thereof include an alkylbenzenesulfonate and a quaternary ammonium salt. A fluorine-based surfactant is preferred because an effect is obtained with a small amount of addition.

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

Further, as a method of adjusting the initial content of the organic component to a predetermined range, it is simple to perform heating and adjustment. Further, it is also possible to adjust the amount of the organic component added when the silver particles are produced, and to change the cleaning conditions or the number of times after the preparation of the silver particles. The heating can be carried out using an oven or an evaporator or the like, or under reduced pressure. In the case of carrying out under normal pressure, it can be carried out in the atmosphere or in an inert environment. Further, the amine, carboxylic acid or the like may be added afterwards to finely adjust the initial content of the organic component.

In addition, the organic component and the amount contained in the composition for bonding can be confirmed, for example, by measurement using TG-DTA/GC-MS manufactured by Rigaku Corporation. The conditions for the measurement may be appropriately adjusted, for example, TG-DTA/GC-MS when 10 mg of the sample is kept at room temperature to 550 ° C (temperature up rate 10 ° C / min) in the atmosphere. It can be measured.

<Step (1)> In the step (1), a bonding composition is applied to the first to-be-joined body. Here, the term "coating" includes the case where the bonding composition is applied in a planar shape, and the coating (drawing) is linear. The shape of the coating film containing the bonding composition which is applied and baked before being heated can be set to a desired shape. Therefore, the bonding material (silver particle sintered layer) 12 of the present embodiment which has been sintered by heating may be either planar or linear, and may be discontinuous or discontinuous in the first bonded body.

As a method of applying the bonding composition, for example, screen printing (metal mask printing), dispenser method, pin transfer method, dipping, spraying method, and bar coating method can be used. The spin coating method, the inkjet method, the coating method using a brush, a casting method, a flexographic method, a gravure method, a flat plate method, a transfer method, a hydrophilic hydrophobic pattern method, a syringe method, and the like are suitably selected.

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

<Step (2)> In the step (2), the applied bonding composition (coating film) is dried by heating. The bonding composition applied to the first to-be-joined body has a large amount of organic components in order to ensure applicability (printability) and pot life (useable time), and when the second to-be-joined body is directly pressed and heated and sintered, Then, a large amount of voids (pores) are generated in the sintered layer of the generated silver particles. Therefore, before the second object to be joined is pressed to the bonding composition, the bonding composition is heated and dried in the step (2), and the content of the organic component in the bonding composition is reduced in advance. At this time, when the content of the organic component in the bonding composition is excessively reduced, the second to-be-joined body and the bonding composition are not sufficiently adhered to each other, so that voids or peeling occur. Therefore, the heat drying (pre-drying) in the step (2) is carried out so that the content of the organic component in the bonding composition which is dried by heating is 4% by mass or more. In addition, the content of the organic component in the heat-drying bonding composition is preferably 6% by mass or less from the viewpoint of suppressing generation of voids in the sintered silver particle sintered layer.

The heating temperature (pre-drying temperature) in the step (2) is preferably 25 ° C or more and 100 ° C or less. If it is less than 25 ° C, the dispersion medium in the bonding composition cannot be volatilized efficiently. When it exceeds 100 ° C, the dispersion medium can be sufficiently volatilized, but a part of the dispersing agent adhering to the silver particles is volatilized, and there is a fear that sintering starts. In this case, it is difficult to adhere the second joined body when it is pressed. Bonding without pressure is performed. A more preferred lower limit of the pre-drying temperature is 50 ° C, and a preferred lower limit is 60 ° C. Further, the organic component in the pre-dried bonding composition does not substantially contain an organic component having a boiling point equal to or lower than the highest temperature pre-dried. The heating time in the step (2) is not particularly limited, and it is preferred that the content of the organic component in the composition for bonding does not change. The method of performing the heat drying in the step (2) is not particularly limited, and for example, a previously known oven or the like can be used.

<Step (3)> In the step (3), the second joined body is pressed to the heat-dried joining composition. The second joined body is preferably pressed with a load of 1 MPa or less. When the pressing load exceeds 1 MPa, damage (scratch or crack of the surface) may occur in the second joined body of the power semiconductor wafer 11 or the like. The pressing load is preferably 0.05 MPa or more. When the pressing load is less than 0.05 MPa, the adhesion is insufficient and there is a concern that peeling may occur. The method of pressing the second joined body in the step (3) is not particularly limited, and various conventionally known methods can be applied, and it is preferable to uniformly heat the dried bonding composition (dry coating film). The method of applying pressure.

By the way, in the case of pre-drying after the step (3), the dispersion medium cannot be volatilized efficiently, and it takes not only a long time but also a case of pre-drying before the step (3). In a state in which the first to-be-joined body and the second to-be-joined body are sandwiched, the dispersion medium volatilizes only from the side of the coating film. Therefore, only the end portions of the coating film are joined, and the organic component is likely to remain in the coating film to cause voids.

<Step (4)> In the step (4), the bonding composition is heated and sintered to form a sintered silver particle layer. In the pre-heating of the step (2), a dispersant or the like which mainly disperses the dispersion medium and adheres to the silver particles in the organic component remains in the bonding composition, and is heated by the step (4) to form a bonding composition. Most or all of the organic components are volatilized. In the present embodiment, when the bonding composition contains the binder component, the binder component is sintered in view of the improvement of the strength of the bonding material and the bonding strength between the bonding members. It is applied to various printing methods to adjust the viscosity of the bonding composition as a main component of the binder component, and the calcination conditions are controlled to remove all of the binder components. Regarding the silver particle sintered layer, in terms of obtaining high joint strength and high reliability, the residual amount of the organic component is preferably small, preferably not substantially containing the organic component, and the present invention may be omitted. A part of the organic component remains in the range of the effect. The content of the organic component in the sintered layer of silver particles is preferably less than 1% by mass.

Further, by the heating in the step (4), not only the silver particles in the bonding composition are bonded to each other, but also the metal is adjacent to the interface between the first joined body and the second joined body and the sintered layer of the silver particles. The layers spread out. Thereby, a strong bond is formed between the first joined body and the sintered silver particle layer, and between the second joined body and the sintered silver particle layer.

In the step (4), the first joined body and the second joined body may be joined while being pressed, or the first joined body and the second joined body may be joined without pressure. The bonding without pressurization does not simultaneously pressurize and heat, and therefore is excellent in productivity. When the bonding is performed under no pressure, volatilization of the organic component when the bonding composition is heated and sintered is likely to cause voids in the silver particle sintering layer. In the present embodiment, the step is performed by the step. (2) The pre-drying and the content of the organic component in the composition for bonding are adjusted, so that the occurrence of voids is suppressed even when the bonding is performed without pressure, and a sintered layer of silver particles (joining material) having high bonding strength is obtained. . Therefore, in the method of the present embodiment, the step (4) is preferably a case where the first joined body and the second joined body are joined without pressure.

The heating temperature in the step (4) is not particularly limited as long as it can form a sintered layer of silver particles, and is preferably 200 to 300 °C. When the heating temperature is 200 ° C to 300 ° C, damage in the first joined body and the second joined body is prevented, and the organic component or the like can be removed by evaporation or decomposition, and high joint strength can be obtained. Further, when heating is performed, the temperature may be gradually increased or decreased, and it is preferred to raise the temperature from room temperature. The heating time in the step (4) is not particularly limited as long as it is adjusted in accordance with the heating temperature and sufficiently obtaining the joint strength. The method of performing the heating in the step (4) is not particularly limited, and for example, a previously known oven or the like can be used.

The sintered silver particle layer is preferably a dense sintered body from the viewpoint of obtaining a mechanically, electrically and thermally bonded state. Specifically, the sintered ratio of the silver particle sintered layer is preferably 20% by volume. %the following. According to the method for producing a metal bonded laminate of the present embodiment, even if the bonding is performed without pressure, a sintered silver particle layer having a void ratio of 5 vol% to 20 vol% can be easily formed.

The thickness of the sintered silver particle layer is, for example, 10 μm to 200 μm, preferably 20 μm to 100 μm.

According to the present embodiment, as described above, since the content of the organic component in the bonding composition is adjusted by the pre-drying in the step (2), the bonding composition before firing can be improved on the first bonded body and The adhesion of the second to-be-joined body is a sintered silver particle layer (joining material) having a low void ratio and high joint strength. Further, the thickness of the sintered layer of the silver particles can be easily controlled by the thickness of the coating film. [Examples]

Hereinafter, the present invention will be described in more detail by way of examples, but the invention is not limited to the examples.

<Example 1> 2.0 g of 3-methoxypropylamine was sufficiently stirred by a magnetic stirrer, and 3.0 g of silver oxalate was added to make it thick. The obtained viscous substance was placed in a thermostatic chamber and allowed to react, and then 10 g of acetaminophen 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 silver particles coated with acetamidine on the surface were precipitated and separated by centrifugation, and the supernatant was discarded. Repeat this operation again. Add 1 g of silver particles coated with acetopropionic acid to the surface and 1 g of micron silver particles (Ag-HWQ 1.5, manufactured by Fukuda Metal Foil Co., Ltd.) as a dispersion medium, 0.05 g of tridecyl alcohol, butyl carbene 0.06 g of an alcohol acetate and 0.005 g of ricinoleic acid were stirred and mixed to obtain a bonding composition A containing silver particles and an organic component.

The obtained bonding composition A was coated on a silver-plated copper plate (20 mm square) with a metal mask to a thickness of 11 mm square, pre-dried, placed in an oven set at 70 ° C, and dried for 3 minutes. A gold-plated Si wafer (bottom area: 10 mm × 10 mm) was laminated on the dried bonding composition A, and pressed at 0.2 MPa.

Furthermore, the obtained laminated body was placed in a reflow furnace (manufactured by Shinapex Co., Ltd.), and heated in the air at room temperature at a temperature increase rate of 3.8 ° C /min to a maximum temperature of 250 ° C, and then calcined for 60 minutes. Processing to form a sintered layer of silver particles. At the time of the calcination treatment, it was carried out without pressurization without pressure. By forming a sintered layer of silver particles, a metal bonded laminate in which a silver-plated copper plate (first bonded body) and a gold-plated Si wafer (second bonded body) are joined by a silver particle sintered layer is completed.

<Example 2> A metal bonded laminate was produced in the same manner as in Example 1 except that the calcination treatment was carried out in a nitrogen atmosphere, and a silver-free copper plate was used instead of the silver-plated copper plate.

<Example 3> In place of 0.05 g of tridecyl alcohol and 0.06 g of butyl carbitol acetate, 0.2 g of hexyl carbitol was added to obtain a bonding composition B, and the pre-drying time was changed to 15 minutes. A metal bonded laminate was produced in the same manner as in Example 1.

<Example 4> A metal bonded laminate was produced in the same manner as in Example 3 except that the calcination treatment was carried out in a nitrogen atmosphere, and a silver-free copper plate was used instead of the silver-plated copper plate.

<Example 5> A metal bonded laminate was produced in the same manner as in Example 3 except that the maximum temperature in the calcination treatment was 280 °C.

<Example 6> A metal bonded laminate was produced in the same manner as in Example 3 except that the temperature and the time in the pre-drying were changed to 100 ° C for 5 minutes.

<Example 7> The same procedure as in Example 3 except that 1.5 g of 3-ethoxypropylamine and 0.4 g of diglycolamine were added in place of 3-methoxypropylamine to obtain a composition C for bonding. A metal bonded laminate is produced.

<Example 8> A metal bonded laminate was produced in the same manner as in Example 7 except that the calcination treatment was carried out in a nitrogen atmosphere, and a silver-free copper plate was used instead of the silver-plated copper plate.

<Comparative Example 1> An amine mixed liquid was prepared by mixing 8.0 g of 3-methoxypropylamine with 0.40 g of dodecylamine and sufficiently stirring with a magnetic stirrer. While stirring the amine mixed solution, 6.0 g of silver oxalate and 10 g of silver particles (manufactured by Mitsui Mining and Mining Co., Ltd., reduced powder, D50 (median diameter) = 1.5 μm) were added to make the adhesive. The obtained viscous substance was placed in a thermostatic chamber and allowed to react to obtain a suspension. In order to replace the dispersion medium of the suspension, methanol was added and stirred, and then silver particles coated with silver fine particles on the surface were precipitated and separated by centrifugation, and the supernatant was discarded. Repeat this operation again. To the 15 g of silver particles coated with silver fine particles on the surface, 0.4 g of tridecyl alcohol as a dispersion medium, 0.4 g of butyl carbitol acetate, and 0.01 g of ricinoleic acid were added and stirred to obtain a composition for bonding D. . A metal bonded laminate was produced in the same manner as in Example 1 except that the bonding composition D was obtained.

<Comparative Example 2> A metal bonded laminate was produced in the same manner as in Example 1 except that pre-drying was not performed.

<Comparative Example 3> A metal bonded laminate was produced in the same manner as in Example 3 except that pre-drying was not performed.

<Comparative Example 4> A metal bonded laminate was produced in the same manner as in Example 3 except that the temperature and the time in the pre-drying were changed to 100 ° C for 10 minutes.

[Evaluation Test] The following evaluation tests were carried out using the bonding compositions produced in the examples and the comparative examples. The results are shown in Table 1.

(1) Measurement of Average Particle Diameter of Silver Particles The average particle diameter of silver particles was obtained by the following method: 200,000 times according to a scanning electron microscope (model: S4800) manufactured by Hitachi High-Technologies Co., Ltd. In the photograph, the arithmetic mean of the particle diameters of 50 to 100 particles is calculated.

(2) Measurement of Content of Organic Component after Pre-drying The mass of the composition for bonding was measured before and after pre-drying, and the content of the organic component after pre-drying was calculated based on the obtained mass and using the following formula. The amount of volatilization of the organic component (g) = mass (g) of the composition for bonding to be applied - mass of the component for pre-drying (g) content of organic component after pre-drying (% by mass) = { Amount of addition of organic component (g) - amount of volatilization of organic component (g) / mass of coated composition (g)} × 100

(3) Measurement of joint strength A joint strength test was carried out at room temperature using a bond tester (manufactured by Rhesca Co., Ltd.).

(4) Measurement of void ratio (porosity) The cross section of the metal bonded laminate was exposed by polishing and observed by a scanning electron microscope. The void ratio was calculated from the obtained electron micrograph and the area of the void in the sintered layer of the silver particles was divided by the entire area of the sintered layer of the silver particles. The void ratio is 20% or less, ○, 21% to 30% is Δ, and 31% or more is ×. Further, regardless of the value of the void ratio, the case where a large void or a joint interface is peeled off is set to ×.

[Table 1]

As described in Table 1, in Examples 1 to 8, the gold-plated Si wafer was pressed against the bonding composition applied to the silver-plated copper plate (first bonded body) (the second was Before the bonded body), the content of the organic component in the composition for bonding is pre-dried to a level of 4% by mass or more. Therefore, the sintered metal silver layered product has a low void ratio and a high porosity. Bonding strength.

On the other hand, in Comparative Example 1, the content of the organic component in the bonding composition D was small, and the content of the organic component in the bonding composition after pre-drying was 3.2% by mass, so that even the gold-plated Si was pressed. The wafer will not be fully bonded. Therefore, the void ratio of the sintered layer of silver particles becomes low, and high joint strength cannot be obtained. Further, in Comparative Example 2 and Comparative Example 3, since pre-drying was not performed, voids (pores) were generated in a large amount in the sintered layer of the silver particles, and the joint strength was low. Further, in Comparative Example 4, since the pre-drying temperature was high and the content of the organic component in the pre-dried bonding composition was 3.5% by mass, even if the gold-plated Si wafer was pressed, it would not be sufficiently adhered. Therefore, the void ratio of the sintered layer of silver particles becomes low, and high joint strength cannot be obtained.

11‧‧‧Power semiconductor wafer

12‧‧‧Material

13‧‧‧Copper-clad insulating substrate

13a‧‧‧Substrate

13b‧‧‧Cu layer

14‧‧‧heating materials

15‧‧‧ Heat sink

16‧‧‧Wire bonding wire

FIG. 1 is a schematic cross-sectional view showing a configuration of a power device as an example of a metal bonded laminate.

Claims (5)

A method for producing a metal bonded laminated body, which is a method for producing the metal joined laminated body obtained by joining a first joined body and a second joined body by a silver particle sintered layer, and characterized in that: 1) applying a bonding composition containing silver particles and an organic component to the first object to be joined; and heating and drying the applied bonding composition in step (2); and (3), Pressing the second object to be bonded to the bonding composition that is dried by heating; and step (4), heating and sintering the bonding composition to form the sintered layer of silver particles, and The content of the organic component in the bonding composition which is dried by heating in the step (2) is 4% by mass or more. The method for producing a metal bonded laminate according to claim 1, wherein the sintered silver oxide layer has a void ratio of 20% by volume or less. The method for producing a metal bonded laminate according to the first or second aspect of the invention, wherein the step (2) is carried out by heating and drying at a temperature of 25 ° C or more and 100 ° C or less. The method for producing a metal bonded laminate according to the above aspect, wherein in the step (3), the second joined body is pressed with a load of 1 MPa or less. The method for producing a metal bonded laminate according to the above aspect, wherein in the step (4), the first joined body and the second joined are joined without pressure. Body bonding.