WO2019021637A1

WO2019021637A1 - Method for producing metal bonded laminate

Info

Publication number: WO2019021637A1
Application number: PCT/JP2018/021411
Authority: WO
Inventors: 智文渡辺
Original assignee: バンドー化学株式会社
Priority date: 2017-07-27
Filing date: 2018-06-04
Publication date: 2019-01-31
Also published as: JPWO2019021637A1; JP6467114B1; TW201911989A

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 of manufacturing metal-bonded laminate

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

Conventionally, a bonding material such as a solder, a conductive adhesive, a silver paste, an anisotropic conductive film or the like is used for mechanical, electrical and / or thermal bonding of metal parts. These bonding materials may be used not only for metal parts but also for bonding ceramic parts, resin parts and the like. Examples of applications of the bonding material include applications in which a light emitting element such as an LED is bonded to a substrate, applications in which a semiconductor chip is bonded to a substrate, and applications in which those substrates are further bonded to a heat dissipation member.

Patent Document 1 relates to a bonding material and a bonding method using the same, which is a bonding material comprising silver paste in which silver fine particles and a solvent are mixed, wherein the solvent is a diol and has one or more methyl groups as an additive. A mixture of triols is disclosed.

JP, 2016-8332, A

The present inventor has researched and developed a bonding composition containing silver particles in order to use a silver particle sintered layer as a bonding material. And, it has been found that by blending an organic component such as a dispersion medium in the composition for bonding, it is possible to secure good coating properties (printability) and pot life (use time) of the composition for bonding. There is room for improvement in that voids and peeling are likely to occur at the time of firing to sinter the particles, and a desired bonding strength can not be obtained.

This invention is made in view of the said present condition, and it aims at providing the manufacturing method of the metal-joining layered product which can obtain high junction intensity, securing the good handling nature of the composition for junctions. .

The present inventor variously studied a method for producing a metal-bonded laminate capable of obtaining high bonding strength while securing good handleability of the bonding composition, and focused on the organic component contained in the bonding composition. . Then, as a result of intensive investigations, the inventor of the present invention maintains the content of the organic component at 4% by mass or more before pressing the second bonded body on the bonding composition applied to the first bonded body. Thus, the porosity (void fraction) in the silver particle sintered layer is suppressed, while securing the coatability (printability) and pot life (pot life) of the bonding composition by performing the heat drying treatment, The inventors have found that high bonding strength can be obtained and completed the present invention.

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 bonded by a silver particle sintered layer, A step (1) of applying a bonding composition containing silver particles and an organic component to the material to be bonded, a step (2) of heating and drying the applied bonding composition, and the heat-dried bonding Including the step (3) of pressing the second body to be bonded to the second composition and the step (4) of heating and sintering the bonding composition to form the silver particle sintered layer The content of the organic component in the bonding composition heat-dried in the step (2) is 4% by mass or more.

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

It is preferable to heat-dry at the temperature of 25 degreeC or more and 100 degrees C or less in said process (2).

In the step (3), the second object to be bonded is preferably pressed with a load of 1 MPa or less.

In the step (4), preferably, the first object to be joined and the second object to be joined are joined under no pressure.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the metal-joining laminated body from which high joint strength is obtained can be provided, ensuring the favorable handleability of the composition for joining.

It is the cross-sectional schematic diagram which showed the structure of the power device which is an example of a metal joining laminated body.

The method of manufacturing a metal-bonded laminate according to the present embodiment is a method of manufacturing a metal-bonded laminate in which a first bonded body and a second bonded body are bonded by a silver particle sintered layer, A step (1) of applying a bonding composition containing silver particles and an organic component to one object to be bonded, a step (2) of heating and drying the applied bonding composition, and the above-described heat-dried step Including the step (3) of pressing the second body to be bonded to the bonding composition, and the step (4) of heating and sintering the bonding composition to form the silver particle sintered layer. The content of the organic component in the bonding composition heat-dried in the step (2) is 4% by mass or more.

The metal bonded laminate manufactured in the present embodiment is obtained by bonding a first bonded body and a second bonded body by a silver particle sintered layer. The types of the first and second objects to be joined are not particularly limited, but it is preferably a member having heat resistance not to be damaged by the temperature at the time of heat sintering of the bonding composition, and rigid Or flexible. Further, from the viewpoint of obtaining high bonding strength, it is preferable that the bonding surface of the first body and the second body be formed of a metal such as Cu, Ag, Au or the like. Moreover, the shape and thickness of a 1st to-be-joined body and a 2nd to-be-joined body are not specifically limited, It can select suitably.

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

As a metal junction laminated body manufactured in this embodiment, the semiconductor element for electric power (power device) is mentioned, for example. FIG. 1 is a schematic cross-sectional view showing the configuration of a power device which is an example of a metal bonding laminate. In the power device shown in FIG. 1, the lower surface of the power semiconductor chip (second bonded body) 11 and the upper surface of the copper-clad insulating substrate (first bonded body) 13 are bonded by a bonding material 12. The power semiconductor chip 11 has a main body made of Si, SiC, GaN or the like, and the lower surface thereof is plated with Au. The bonding material 12 is a silver particle sintered 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 sides of a base 13a made of silicon nitride or the like. In some cases, the Cu layer 13b is not plated with Ag.

Under the copper-clad insulating substrate 13, a heat dissipating material 14 and a heat sink 15 are attached in order to release the heat generated in the power semiconductor chip 11. Arrows in FIG. 1 indicate heat release paths. Further, a wire bond 16 is attached to the upper portion of the power semiconductor chip 11 in order to supply power to the power semiconductor chip 11.

The bonding material 12 composed of the silver particle sintered layer can strongly bond the power semiconductor chip 11 to the copper-clad insulating substrate 13 mechanically, electrically and thermally. When the silver particles are nanometer-sized particles, they can be sintered at low temperatures due to the melting point depression specific to the nanoparticles, and high conductivity and thermal conductivity close to those of metal foils can be realized. On the other hand, in the case where solder is used as the bonding material 12 as in the prior art, bonding is performed by melting and solidifying the solder. In this case, the bonding temperature of the bonding material 12 is the melting point of the solder, and the heat resistant temperature (usable temperature) of the bonding material 12 is lower than the melting temperature (the bonding temperature) of the solder. For this reason, if it is going to raise the heat-resistant temperature of the joining material 12, the joining temperature will also rise. In the development of power devices, improvement in heat resistance and long-term reliability is required, and a silver particle sintered layer having high reliability at a higher temperature than solder is preferably used. Here, long-term reliability means that the mechanical properties and the like of the joined body are maintained for a long time, and for example, it is difficult to reduce the mechanical properties and the like of the joined body even by applying a large number of heat cycles. means.

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

<Composition for bonding>
The composition for bonding is not particularly limited as long as it contains silver particles and an organic component, but is preferably in a paste form so as to be easily applied. In addition to silver particles, metals whose ionization sequence is nobler than hydrogen, that is, particles of gold, copper, platinum, palladium, etc. may be used in combination to make migration difficult to occur.

The average particle diameter of the silver particles is preferably 1 to 20 μm. By using silver particles having an average particle diameter of 1 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 size of less than 1 μm are used, sintering proceeds at a low temperature, but when sintering between particles proceeds, the volume shrinkage increases with the increase of the average particle diameter, and the volume shrinkage of the workpiece May not be able to follow In such a case, defects such as voids occur in the bonding material 12 and the bonding strength and reliability of the bonding material 12 are reduced. On the other hand, when particles having an average particle diameter of greater than 20 μm are used, sintering at a low temperature hardly progresses, and large gaps formed between particles may remain even after sintering.

The average particle size of the silver particles can be measured by Dynamic Light Scattering, small-angle X-ray scattering, or wide-angle X-ray diffraction. In the present specification, the "average particle diameter" refers to the dispersion median diameter. As another method of measuring the average particle diameter, there is a method of calculating an arithmetic average value of the particle diameter of about 50 to 100 particles from a photograph taken using a scanning electron microscope or a transmission electron microscope. It can be mentioned.

The above-mentioned composition for junction may contain metal fine particles smaller in diameter than silver particles. The metal fine particles may be separated from the silver particles and dispersed in the bonding composition, or may be attached to at least a part of the surface of the silver particles. Such metals include, for example, gold, silver, copper, nickel, bismuth, tin, iron and platinum group elements (ruthenium, rhodium, palladium, osmium, iridium and platinum). Among them, gold, silver, copper and platinum are preferable, and silver is more preferable. These metals may be used alone or in combination of two or more.

The average particle diameter of the metal fine particles is not particularly limited as long as the effects of the present invention are not impaired. However, it is preferable that the metal fine particles have a nanometer size causing melting point depression, and is 1 to 100 nm. Is more preferred. If the average particle diameter of the metal fine particles is 1 nm or more, a bonding composition capable of forming a favorable bonding material 12 can be obtained, and the production of the metal fine particles is practical without increasing the cost. Moreover, if it is 100 nm or less, the dispersibility of the metal fine particles hardly changes with time, which is preferable.

The organic component is not particularly limited, and is used for the purpose of adjusting the dispersibility of silver particles, the viscosity of the bonding composition, the adhesiveness, the drying property, the surface tension and the coating property (printability) other than the dispersion medium. Additives are used.

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

As said hydrocarbon, an aliphatic hydrocarbon, cyclic hydrocarbon, an alicyclic hydrocarbon etc. are mentioned, You may use each independently and may use 2 or more types together.

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

As said cyclic hydrocarbon, toluene, xylene etc. are mentioned, for example.

Examples of the above-mentioned alicyclic hydrocarbon include limonene, dipentene, terpinene, terpinene (also referred to as terpinene), nesol, sinene, orange flavor, terpinolene, terpinolene (also referred to as terpinolene), ferandrene, mentadiene, tereben, dihydro Examples thereof include simen, musulene, isoterpinene, isoterpinene (also referred to as isoterpinene), clitormen, kautuzin, kajepten, eulimen, pinene, turpent, mentane, pinan, terpene, cyclohexane and the like.

The alcohol is a compound containing one or more OH groups in the molecular structure, and includes aliphatic alcohols, cyclic alcohols and alicyclic alcohols, which may be used alone or in combination of two or more. Good. In addition, a part of the OH group may be derived to an acetoxy group or the like within the range not impairing the effects of the present invention.

Examples of the above aliphatic alcohols 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, oleyl alcohol etc. may be mentioned.

Examples of the cyclic alcohol include cresol and eugenol.

As the above-mentioned alicyclic alcohol, for example, cycloalkanol such as cyclohexanol, terpineol (including α, β, γ isomers or any mixture thereof), and terpene alcohol such as dihydroterpineol (monoterpene alcohol etc.) And dihydroterpineol, myrtenol, sobrerole, menthol, carveol, perillyl alcohol, pinocarbeole, sobrerol, verbenol and the like.

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

The initial content in the case of including the dispersion medium in the composition for bonding may be adjusted according to desired characteristics such as viscosity, and the initial content of the dispersion medium in the composition for bonding is 1 to 30% by mass Is preferred. When the initial content of the dispersion medium is 1 to 30% by mass, the effect of adjusting the viscosity can be obtained within the range in which the composition for bonding can be easily used. A more preferable initial content of the dispersion medium is 1 to 20% by mass, and a further preferable initial content is 4 to 15% by mass.

As an additive which improves the dispersibility of the said silver particle, an amine, carboxylic acid, a polymer dispersing agent, unsaturated hydrocarbon etc. are mentioned, for example. Amines and carboxylic acids contribute to the stability of silver particles in a storage state, because the functional group adsorbs to the surface of silver particles with appropriate strength and prevents the silver particles from contacting each other. It is believed that the additive adsorbed on the surface of the silver particles moves and / or volatilizes from the surface of the particles during heating, thereby promoting fusion between the silver particles and bonding with the substrate. The polymer dispersant can maintain dispersion stability without losing the low-temperature sinterability of silver particles by attaching an appropriate amount to at least a part of silver particles.

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

The above-mentioned amine is not particularly limited, and examples thereof include alkylamines (linear alkylamines, which may have a side chain) such as oleylamine, butylamine, pentylamine, hexylamine and hexylamine, and N- (3- (Methoxypropyl) propane-1,3-diamines, alkoxyamines such as 2-methoxyethylamine, 3-methoxypropylamine, 3-ethoxypropylamine etc., cycloalkylamines such as cyclopentylamine, cyclohexylamine etc., allylamines such as aniline etc. Primary amines, secondary amines such as dipropylamine, dibutylamine, piperidine and hexamethyleneimine, tripropylamine, dimethylpropanediamine, cyclohexyldimethylamine, tertiary amines such as pyridine and quinoline, octylamine, etc. Can be carbon atoms include units of the order of 2 to 20, preferably carbon atoms used 4-7 amine. As specific examples of the amine having 4 to 7 carbon atoms, heptylamine, butylamine, pentylamine and hexylamine can be exemplified. Since the amine having 4 to 7 carbon atoms moves and / or volatilizes at relatively low temperature, the low temperature sinterability of silver particles can be fully utilized. The amine may be linear, branched, or have a side chain.

In addition, when these organic components are chemically or physically bonded to silver particles, it is also considered to be converted into anions or cations, and 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 an amine, such as a hydroxyl group, a carboxyl group, an alkoxy group, a carbonyl group, an ester group or 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 normal temperature is preferably 300 ° C. or less, more preferably 250 ° C. or less.

As said carboxylic acid, the compound which has an at least 1 carboxyl group can be used widely, For example, a formic acid, an oxalic acid, an acetic acid, a hexanoic acid, an acrylic acid, an octylic acid, levulinic acid, an oleic acid etc. are mentioned. A part of carboxyl groups of the carboxylic acid may form a salt with the metal ion. In addition, about the said metal ion, 2 or more types of metal ions may be contained.

The carboxylic acid may be, for example, a compound containing a functional group other than a carboxyl group, such as an amino group, a hydroxyl group, an alkoxy group, a carbonyl group, an ester group or 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 carboxyl groups. The carboxylic acids may be used alone or in combination of two or more. In addition, the boiling point at normal temperature is preferably 300 ° C. or less, more preferably 250 ° C. or less.

Also, the amine and the carboxylic acid form an amide group. An amide group may be contained in the organic component because the amide group is also appropriately adsorbed on the surface of silver particles.

The composition ratio (mass) in the case of using an amine and a carboxylic acid in combination can be optionally selected in the range of 1/99 to 99/1, but is preferably 20/80 to 98/2. Preferably, it is 30/70 to 97/3.

A commercially available polymer dispersant can be used as the above-mentioned polymer dispersant. Commercially available polymer dispersants include, for example, Solsperse (SOLSPERSE) 11200, Solsparse 13940, Solsparse 16000, Solsparse 17000, Solsparse 18000, Solsparse 20000, Solsparse 24000, Solsparse 26000, Solsparse 27000, Solsparse 28000 (Japan Lubrizol, Inc. Made of; DISPERVIK (DISPERBYK) 142, DISPERVIK 160, DISPERVIK 161, DISPERVIK 162, DISPERVIK 163, DISPERVIK 166, DISPERVIK 170, DISPERVIK 180, DISPERVIK 182, DISPERVIK 184, DISPERVIK 190, Disperbic 2155 (above, Big Chemie Ja EFKA-46, EFKA-47, EFKA-48, EFKA-49 (all available from EFKA Chemical Corporation); polymer 100, polymer 120, polymer 150, polymer 400, polymer 401, polymer 401, polymer 402, polymer 403, Polymer 450, Polymer 451, Polymer 452, Polymer 453 (above, made by EFKA Chemical Co., Ltd.); Addisper PB711, Addisper PA 111, Addisper PB 811, Addisper PW911 (above, made by Ajinomoto Co., Ltd.); Floren DOPA-15B, Floren DOPA-22, Floren DOPA-17, FLORENE TG-730W, FLORENE G-700, FLORENE TG-720W (above, manufactured by Kyoeisha Chemical Industry Co., Ltd.) and the like can be mentioned. From the viewpoint of low-temperature sinterability and dispersion stability, it is preferable to use Solsparse 11200, Solsparse 13940, Solsparse 16000, Solsparse 17000, Solsparse 18000, Solsparse 28000, Dispervic 142 or Dispervic 2155.

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

The silver particles can be obtained, for example, by mixing a metal ion source and a dispersing agent and reducing the mixture. In this case, the amount of the organic component can be controlled by adjusting the amounts of the dispersant and the reducing agent to be added.

In order to adjust the amount of organic components attached to the silver particles, heat treatment with silver particles, washing with an acid (sulfuric acid, hydrochloric acid, nitric acid, etc.), washing with a fat-soluble organic solvent such as acetone or methanol, etc. may be used. it can. In addition, an organic component can be removed more efficiently by applying an ultrasonic wave during washing | cleaning.

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

Among the above-mentioned unsaturated hydrocarbons, unsaturated hydrocarbons having a hydroxyl group are preferably used. The hydroxyl group is easily coordinated to the surface of the silver particle, and aggregation of the silver particle can be suppressed. Examples of the unsaturated hydrocarbon having a hydroxyl group include terpene alcohols, allyl alcohol, oleyl alcohol, thianic acid, ricinoleic acid, gallic acid, salicylic acid and the like. Preferably, they are unsaturated fatty acids having a hydroxyl group, and examples thereof include thianic acid, ricinoleic acid, gallic acid, salicylic acid and the like.

In the above organic component, an oligomer component that plays a role as a binder, a resin component, an organic solvent (a part of solid content may be dissolved or dispersed), 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 resins, polyurethane resins such as blocked isocyanate, polyacrylate resins, polyacrylamide resins, polyether resins, melamine resins, terpene resins, etc. These may be used alone or in combination of two or more.

As the organic solvent, except for those mentioned above as the dispersion medium, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 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 to 1,000 Polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having a weight average molecular weight in the range of 300 to 1,000, N, N-dimethylformamide, dimethyl sulfoxide, - methyl-2-pyrrolidone, N, N- dimethylacetamide, glycerin, acetone and the like may be used each of which alone or in combination of two or more.

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

The surfactant is not particularly limited, and any of anionic surfactants, cationic surfactants, and nonionic surfactants can be used, and examples thereof include alkyl benzene sulfonates, quaternary ammonium salts and the like. Be Fluorine-based surfactants are preferred because the effect can be 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 according to this embodiment is preferably 5 to 50% by mass. If the initial content is 5% by mass or more, the storage stability of the bonding composition tends to be improved, and if the initial content 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 to 30% by mass, and a further preferable initial content is 5 to 15% by mass.

In addition, as a method of adjusting the initial content of the organic component to a predetermined range, it is simple to adjust by heating. Moreover, you may carry out by adjusting the quantity of the organic component added at the time of producing silver particle, and may change the washing | cleaning conditions and frequency | count after silver particle preparation. The heating can be performed in an oven, an evaporator, or the like, and may be performed under reduced pressure. When carried out under normal pressure, it can be carried out in the atmosphere or in an inert atmosphere. Furthermore, the above-mentioned amine, carboxylic acid and the like can be added later to finely adjust the initial content of the organic component.

The organic component contained in the bonding composition and the amount thereof can be confirmed, for example, by measurement using TG-DTA / GC-MS manufactured by Rigaku Corporation. The conditions for this measurement may be adjusted as appropriate, but for example, TG-DTA / GC-MS measurement is performed when a 10 mg sample is kept in the air up to room temperature to 550 ° C. (heating rate 10 ° C./min). It is good.

<Step (1)>
At the said process (1), the composition for joining is apply | coated to a 1st to-be-joined body. Here, the term "application" is a concept that includes the case of applying the bonding composition in a planar manner and the case of applying (drawing) in a linear manner. The shape of the coating film made of the bonding composition in the state of being applied and before firing by heating can be made into a desired shape. Therefore, the bonding material (silver particle sintered layer) 12 of the present embodiment after sintering by heating may be either planar or linear, and may be continuous on the first body to be bonded. It may be discontinuous.

Examples of the method for applying the bonding composition include screen printing (metal mask printing), dispenser method, pin transfer method, dipping, spray method, bar coating method, spin coating method, ink jet method, brush application method, It may be appropriately selected from a casting method, a flexo method, a gravure method, an offset method, a transfer method, a hydrophilic / hydrophobic pattern method, a syringe method and the like.

The viscosity of the 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 still more preferably in the range of 1 to 100 Pa · S. By setting it as the said viscosity range, a wide method can be applied as a method of apply | coating the composition for joining. The viscosity can be adjusted by adjusting the particle size of silver particles, adjusting the content of the organic component, adjusting the compounding ratio of each component, adding a thickener, and the like. The viscosity of the bonding composition can be measured, for example, by a cone and plate 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 object to be joined has a large amount of organic component to secure the coatability (printability) and the pot life (pot life). When the bonded body is pressed and heated and sintered, many voids (voids) are generated in the formed silver particle sintered layer. Therefore, before pressing the second body to be bonded to the bonding composition, the bonding composition is dried by heating in step (2) to reduce the content of the organic component in the bonding composition in advance. At this time, if the content of the organic component in the composition for bonding is too small, the second bonded body does not sufficiently adhere to the composition for bonding, so that voids and peeling occur. Therefore, the heating and drying (preliminary drying) in the step (2) is performed such that the content of the organic component in the heat-dried bonding composition is 4% by mass or more. Further, from the viewpoint of suppressing the generation of voids in the silver particle sintered layer to be generated, the content of the organic component in the heat-dried bonding composition is preferably 6% by mass or less.

The heating temperature (preliminary 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 can not be volatilized efficiently. When the temperature exceeds 100 ° C., the dispersion medium can be sufficiently volatilized, but a part of the dispersant attached to the silver particles may also volatilize, and sintering may start, in which case the second object When the bonded body is pressed, it can not be brought into close contact, and bonding without pressure becomes difficult. A more preferable lower limit of the predrying temperature is 50 ° C., and a further preferable lower limit is 60 ° C. In addition, the organic component in the composition for joining after predrying becomes a thing which does not substantially contain the organic component which has a boiling point below the maximum temperature of predrying. Although the heating time in the said process (2) is not specifically limited, It is preferable to carry out until content of the organic component in the composition for joining does not change. The method of heating and drying in the step (2) is not particularly limited, and, for example, a conventionally known oven can be used.

<Step (3)>
In the step (3), the second workpiece is pressed against the heat-dried bonding composition. The second object to be bonded is preferably pressed with a load of 1 MPa or less. When the pressing load exceeds 1 MPa, there is a concern that the second semiconductor object such as the power semiconductor chip 11 may be damaged (surface damage or cracking). The pressing load is preferably 0.05 MPa or more. If the pressing load is less than 0.05 MPa, the adhesion is insufficient and there is a risk of peeling. The method of pressing the second bonded body in the step (3) is not particularly limited, and various conventionally known methods can be applied. However, the heat-dried bonding composition (dried film) is used. The method of uniformly pressurizing is preferable.

Incidentally, when pre-drying is performed after step (3), the dispersion medium can not be volatilized efficiently, so it takes only a longer time than when pre-drying is performed before step (3). In the state of being sandwiched between the first object and the second object, the dispersion medium is only volatilized from the side of the coating, so only the end of the coating starts to bond, and the inside of the coating is The organic component is likely to remain on the surface, resulting in void formation.

<Step (4)>
In the step (4), the bonding composition is heated and sintered to form a silver particle sintered layer. In the preheating of the step (2), the dispersion medium is mainly volatilized among the organic components, and the dispersing agent and the like attached to the silver particles remain in the bonding composition, but the heating in the step (4) Most or all of the organic components in the bonding composition volatilize. In the present embodiment, when the bonding composition 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 members to be bonded. In order to adjust the viscosity of the bonding composition for application to various printing methods, the main purpose of the binder component may be to control firing conditions to remove all the binder component. The silver particle sintered layer preferably has a small residual amount of the organic component from the viewpoint of obtaining high bonding strength and high reliability, and preferably contains substantially no organic component, but the effect of the present invention is not impaired. A portion of the organic component may remain in the range. The content of the organic component in the silver particle sintered layer is preferably less than 1% by mass.

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

Although the said process (4) may join while pressurizing a 1st to-be-joined body and a 2nd to-be-joined body, a 1st to-be-joined body and a 2nd to-be-joined body It may be joined under no pressure. Bonding under no pressure is excellent in productivity because pressing and heating are not performed simultaneously. In the case of bonding under no pressure, voids are easily generated in the silver particle sintered layer due to volatilization of the organic component when heating and sintering the bonding composition, but in the present embodiment, Since the content of the organic component in the bonding composition is adjusted by the preliminary drying in the step (2), generation of voids is suppressed even when bonding is performed under no pressure, and silver particles are sintered with high bonding strength. A layer (bonding material) is obtained. Therefore, the method of this embodiment is suitable when joining a 1st to-be-joined body and a 2nd to-be-joined body under pressure-free in a process (4).

The heating temperature in the step (4) is not particularly limited as long as it can form a silver particle sintered layer, 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 and second objects to be bonded, and high bonding strength can be obtained. Moreover, when heating, temperature may be raised or lowered stepwise, and it is preferable to raise temperature from room temperature. The heating time in the step (4) is not particularly limited, and may be adjusted according to the heating temperature so that the bonding strength can be sufficiently obtained. The method of heating in step (4) is not particularly limited, and, for example, a conventionally known oven can be used.

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

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

According to the present embodiment, as described above, the content of the organic component in the bonding composition is adjusted by the predrying in the step (2). The adhesion of the bonding composition before firing to the bonded body can be improved, and a silver particle sintered layer (bonding material) having a low porosity and high bonding strength can be obtained. The thickness of the silver particle sintered layer 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 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 solution. The obtained viscous substance was placed in a constant temperature bath and allowed to react, 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 silver particles coated on the surface with levulinic acid were precipitated and separated by centrifugation, and the supernatant was discarded. This operation was repeated once more. To 1 g of silver particles coated on the surface with this levulinic acid and 1 g of micron silver particles (Ag-HWQ 1.5 manufactured by Fukuda Metal Foil & Powder Industry Co., Ltd.), 0.05 g of tridecanol as a dispersion medium, and butyl carbitol acetate was added 0. 06 g and 0.005 g of ricinoleic acid were added and stirred and mixed to obtain a bonding composition A containing silver particles and an organic component.

The obtained bonding composition A was applied on a silver-plated copper plate (20 mm square) to a 11 mm square using a metal mask, and was put in an oven set at 70 ° C. as preliminary drying and dried for 3 minutes. A gold-plated Si chip (bottom area 10 mm × 10 mm) was stacked on the dried bonding composition A, and pressed at 0.2 MPa.

Then, the obtained laminate is placed in a reflow furnace (made by Shin-Apex), raised to a maximum temperature of 250 ° C. at a temperature rising rate of 3.8 ° C./min from room temperature in the air, and held for 60 minutes for firing The treatment was performed to form a silver particle sintered layer. During the firing process, no pressure was applied and no pressure was applied. Metal bonding lamination in which a silver-plated copper plate (first bonded body) and a gold-plated Si chip (second bonded body) are bonded by a silver particle sintered layer by the formation of a silver particle sintered layer The body is complete.

Example 2
A metal-bonded laminate was produced in the same manner as in Example 1 except that the firing treatment was carried out under a nitrogen atmosphere and that a pure copper plate ultrasonically washed with dilute sulfuric acid was used instead of the silver-plated copper plate.

Example 3
Performed except that 0.2 g of hexyl carbitol was added instead of 0.05 g of tridecanol and 0.06 g of butyl carbitol acetate to obtain a bonding composition B, and the predrying 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 firing treatment was carried out in a nitrogen atmosphere, and that a pure copper plate ultrasonically washed with dilute sulfuric acid 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 firing treatment was set to 280 ° C.

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

Example 7
A metal-bonded laminate was prepared in the same manner as in Example 3 except that 1.5 g of 3-ethoxypropylamine and 0.4 g of diglycolamine were added instead of 3-methoxypropylamine to obtain a bonding composition C. Made.

Example 8
A metal-bonded laminate was produced in the same manner as in Example 7 except that the firing treatment was carried out in a nitrogen atmosphere, and that a pure copper plate ultrasonically washed with dilute sulfuric acid was used instead of the silver-plated copper plate.

Comparative Example 1
8.0 g of 3-methoxypropylamine and 0.40 g of dodecylamine were mixed and sufficiently stirred by a magnetic stirrer to prepare an amine mixture. While stirring, 6.0 g of silver oxalate and 10 g of silver particles (reduced powder manufactured by Mitsui Mining & Smelting Co., Ltd., reduced powder, D50 (median diameter) = 1.5 μm) were added to the amine mixed solution to thicken the mixture. The resulting viscous material was placed in a thermostat 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 on the surface with silver fine particles were precipitated by centrifugation and separated, and the supernatant was discarded. This operation was repeated once more. 0.4 g of tridecanol as a dispersion medium, 0.4 g of butyl carbitol acetate, and 0.01 g of ricinoleic acid are added to 15 g of the silver particles whose surface is covered with the silver fine particles as a dispersion medium, and mixed by stirring. Obtained. 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 predrying was not performed.

Comparative Example 3
A metal-bonded laminate was produced in the same manner as in Example 3 except that predrying 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 time in the preliminary drying were set to 100 ° C. for 10 minutes.

[Evaluation test]
The following evaluation test was done using the composition for joining produced by the Example and the comparative example. The results are shown in Table 1.

(1) Measurement of average particle diameter of silver particles From a photograph taken at 200,000 magnification using a scanning electron microscope (model number: S4800) manufactured by Hitachi High-Technologies Corporation, the arithmetic average of the particle diameter of about 50 to 100 particles The average particle diameter of silver particles was obtained by the method of calculating the value.

(2) Measurement of the content of the organic component after preliminary drying The mass of the bonding composition is measured before and after preliminary drying, and based on the obtained mass, the content of the organic component after preliminary drying using the following formula The amount was calculated.
Volatile amount of organic component (g) = mass of bonding composition applied (g) -mass of bonding composition after preliminary drying (g)
Content of organic component after preliminary drying (mass%) = {addition amount of organic component (g) -volatilization amount of organic component (g) / mass of bonding composition applied (g)} × 100

(3) Measurement of Bonding Strength A bonding strength test was conducted using a bond tester (made by Lesca) at normal temperature.

(4) Measurement of Void Ratio (Void Ratio) The cross section was exposed by polishing the metallurgical laminate, and the cross section was observed with a scanning electron microscope. From the obtained electron micrograph, the porosity was calculated by dividing the area of the voids in the silver particle sintered layer by the entire area of the silver particle sintered layer. The void ratio of 20% or less was ○, 21 to 30% was Δ, and 31% or more was x. Moreover, regardless of the value of the porosity, the thing in which the big space | gap existed or the interface which joined was peeling was made into x.

As can be seen from Table 1, in Examples 1 to 8, Si chip (second object to be joined) plated with gold for a bonding composition applied on a silver-plated copper plate (first object to be joined) Since the pre-drying was performed to such an extent that the content of the organic component in the bonding composition would be 4% by mass or more before pressing B), the prepared metal bonded laminate had a void of the silver particle sintered layer The rate was low, and high bond strength was obtained.

On the other hand, in Comparative Example 1, the content of the organic component in the composition for bonding D is small, and the content of the organic component in the composition for bonding after the preliminary drying is 3.2 mass%. Even if the pressed Si chip was pressed, it did not adhere sufficiently. For this reason, the porosity of the silver particle sintered layer was low, and high bonding strength was not obtained. Moreover, in Comparative Examples 2 and 3, since preliminary drying was not performed, many voids (voids) were generated in the silver particle sintered layer, and the bonding strength was low. Further, in Comparative Example 4, since the predrying temperature is high and the content of the organic component in the bonding composition after predrying is 3.5% by mass, the Si chip subjected to the gold plating is sufficiently pressed. It did not stick. For this reason, the porosity of the silver particle sintered layer was low, and high bonding strength was not obtained.

11 Power Semiconductor Chip 12 Bonding Material 13 Copper-clad Insulating Substrate

13a Base Material

13b Cu Layer 14 Heat Dissipating Material 15 Heat Sink 16 Wire Bonding

Claims

A method for producing a metal-bonded laminate, in which a first bonded body and a second bonded body are bonded by a silver particle sintered layer,
Applying a bonding composition containing silver particles and an organic component to the first body to be bonded;
Heat-drying the applied bonding composition (2);
A step (3) of pressing the second object to be bonded to the heat-dried bonding composition;
Heating and sintering the bonding composition to form the silver particle sintered layer (4);
Content of the said organic component in the said composition for joining heat-dried by the said process (2) is 4 mass% or more, The manufacturing method of the metal joint laminated body characterized by the above-mentioned.
The porosity of the said silver particle sintered layer is 20 volume% or less, The manufacturing method of the metal-joining laminated body of Claim 1 characterized by the above-mentioned.
In the said process (2), it heat-drys at the temperature of 25 degreeC or more and 100 degrees C or less, The manufacturing method of the metal joining laminated body of Claim 1 or 2 characterized by the above-mentioned.
The method for producing a metal-bonded laminate according to any one of claims 1 to 3, wherein in the step (3), the second bonded body is pressed with a load of 1 MPa or less.
The metal-bonded laminate according to any one of claims 1 to 4, wherein in the step (4), the first object to be joined and the second object to be joined are joined under no pressure. Manufacturing method.