WO2015098658A1

WO2015098658A1 - Bonding material containing metal nanoparticles

Info

Publication number: WO2015098658A1
Application number: PCT/JP2014/083442
Authority: WO
Inventors: 裕仁長田; 森脇　雅幸; 義之佐野; 香河村
Original assignee: Dic株式会社
Priority date: 2013-12-24
Filing date: 2014-12-17
Publication date: 2015-07-02
Also published as: TW201538537A

Abstract

The present invention addresses the problem of providing a material that achieves sufficient bonding strength at a low bonding temperature without application of a pressure. This problem is solved by providing a bonding material which is characterized by containing: metal nanoparticles (B) to which a polyethylene glycol-containing organic compound (A) having 8-200 carbon atoms is complexed; and at least one solvent (C) selected from the group consisting of an alcohol solvent having a boiling point of 150°C or more, an ether solvent having a boiling point of 150°C or more, an ester solvent having a boiling point of 150°C or more and a lactam structure-containing solvent having a boiling point of 150°C or more.

Description

Bonding material containing metal nanoparticles

The present invention relates to a bonding material having metal nanoparticles having a particle diameter of 1 to 100 nm as a main bonding agent.

Restrictions on the use of harmful substances are widely imposed in the industry from the viewpoint of environmental protection, but in particular, lead-free solder materials have been strongly promoted in mounting materials based on the enforcement of the European Union's RoHS directive. . As a result, a tin-silver or tin-copper solder has been found and widely used as a joining material that replaces the conventional tin-lead eutectic solder (melting point 183 ° C.) (melting point 220). ~ 230 ° C). However, in mounting where heat resistance and heat transfer are required, such as joining a power device that controls a large current to a heat dissipation base, reliability under high temperature conditions around 250 ° C. is required. However, a bonding material having a performance in place of a tin-lead alloy (melting point: 238 ° C.) has not been found, and a material containing a high content of lead is still used (Non-patent Document 1).

The joining technology using metal nanoparticles is expected as a heat-resistant joining method that does not use lead. Metal nanoparticles of 100 nm or less have a much higher specific surface area per weight than bulk metals, so there is a strong tendency to fuse with each other to reduce surface energy, and particles at a much lower temperature than bulk metals. They can be fused together. Applying this phenomenon called the quantum size effect (Kubo effect), the solder is made fine to the extent that the melting point is lowered, and for bonding using silver nanoparticles that are fused at 350 ° C under no pressure condition A material was developed (Patent Document 1). If metal nanoparticles are applied as a bonding material, it becomes a lead-free bonding technique, and therefore, a practical application of a bonding method and a bonding article using silver nanoparticles is being studied.

When it becomes a bulk metal by heating, it requires a considerably high temperature (melting point of the bulk metal) to be melted again, and therefore, high reliability under high temperature conditions of 250 ° C. or higher can be expected for joining using metal nanoparticles. . That is, it is suitable for soldering for circuit mounting used in high-temperature environments such as the aforementioned power semiconductor bonding and automobile engine rooms. Since it does not remelt up to the melting point of the bulk material, the property that the bonding is stable when performing secondary mounting is also a practical value. Applications are also expected in the assembly of power semiconductor devices for hybrid vehicles.

However, in joining using metal nanoparticles, heating at about 300 ° C. is necessary, and at this temperature, peripheral parts are warped and curved, so in order to perform joining by an existing process, there is no pressure condition. Below, it is necessary to realize low-temperature bonding at 200 ° C. or lower. Although there is also a report that the bonding temperature is lowered to 300 ° C. or less by adding a fluxing agent such as oxydiacetic acid, it is inferior in practicality because it is necessary to perform silver plating treatment on the bonding substrate (Patent Document 2). . In addition, as an example of low-temperature bonding at 200 ° C. or lower, there is a report using a composite composition in which a copolymer of polyethyleneimine and polyethylene glycol is combined with silver nanoparticles as a bonding agent (Patent Document 3). In addition to requiring pressurization of about 5 MPa, the bonding strength test method is a cellophane tape peel test, and so on, so it cannot be said that the performance satisfies the actual power semiconductor manufacturing process.
On the other hand, the silver described above has a weak point that it tends to cause ion migration and easily causes a wiring short circuit, and it is extremely difficult to reduce the price because it is a noble metal. Therefore, investigations have been made on bonding methods and bonding articles using copper nanoparticles (Patent Documents 4 to 5).
The bonding material of Patent Document 4 is characterized in that copper nanoparticles and silver nanoparticles are used in combination, and each metal of the metal nanoparticles is protected with a low molecular amine. Since the interaction between the low molecular amine and the metal nanoparticle is strong, the low molecular amine is not detached from the nanometal unless the temperature is high, and the nanometal cannot be sufficiently sintered. Therefore, in order to obtain a sufficient bonding strength, bonding under a high temperature condition of 350 ° C. in the atmosphere is required.
Moreover, although the joining material of patent document 5 is characterized by using the copper nanoparticle which adjusted the particle size distribution, although there exists an effect which provides the oxidation resistance of copper nanoparticle itself, it is the material of joining material itself. Storage stability is insufficient and the addition of a dispersion stabilizer is essential. In order to ensure sufficient bonding strength in the presence of a dispersion stabilizer, bonding is performed at a high temperature of 300 ° C. to 400 ° C. in a hydrogen gas atmosphere as a reducing gas, but the practicality is poor.
In addition, low molecular weight protective agents having an alkyl chain of about C ₈ to C ₁₂ as a dispersion site and a terminal amine or carboxylic acid as a metal coordination site have been widely used in metal nanoparticle bonding agents (Patent Documents). 6). When metal nanoparticles using such a low molecular weight protective agent are used as a bonding material, a flux agent is added as a reducing agent in order to reduce and remove a very thin metal oxide layer on the surface of the metal nanoparticles. However, the alkyl chain in the protective agent does not completely decompose and volatilize at a low temperature of 200 ° C. or lower, and remains on the surface of the metal nanoparticles, hindering the reduction effect of the flux agent, making it difficult to realize low-temperature bonding. It was.
On the other hand, metal nanoparticle bonding using a phosphate-based protective agent having a hydrophilic site has also been studied, but the metal oxide film removal ability is not sufficient, and bonding at a low temperature of 200 ° C. has not been achieved. No (Patent Document 7).

International Publication No. 2011/155615 JP 2011-240406 A JP 2011-046770 A JP 2011-058041 A JP 2013-091835 A International Publication No. 2011/007402 JP 2013-004309 A

As mentioned above, silver nanoparticles have problems such as migration and cost reduction, and copper nanoparticles need to be bonded under high temperature conditions due to oxidation resistance. It can be used as a bonding agent.
However, although silver and copper nanoparticles have high utility as a bonding agent for power semiconductors, low-temperature bonding at 200 ° C. or lower cannot be achieved, which greatly hinders practical application. For these reasons, it is desired to lower the bonding temperature under no pressure condition.
Therefore, the main problem to be solved by the present invention is a bonding material using metal nanoparticles, which is high under no pressure condition and at a low temperature of 200 ° C. or less without impairing the dispersion stability of the metal nanoparticles. An object of the present invention is to provide a bonding material that can be bonded with strength.

As a result of intensive studies in view of the above circumstances, a polyethylene glycol structure having 8 to 200 carbon atoms is introduced into the dispersion site in the protective agent, and a specific solvent such as an alcohol solvent having a boiling point of 150 ° C. or higher is added. Thus, the metal oxide thin film layer on the surface of the metal nanoparticles can be effectively removed at a low temperature of 200 ° C. or less without the addition of a flux agent, and a metal nanoparticle bonding material that enables high-strength bonding is completed. It came.

That is, the present invention
Item 1. Metal nanoparticles (B) in which a polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms is combined, an alcohol solvent having a boiling point of 150 ° C. or higher, an ether solvent having a boiling point of 150 ° C. or higher, and an ester solvent having a boiling point of 150 ° C. or higher. And at least one solvent (C) selected from the group consisting of a lactam structure-containing solvent having a boiling point of 150 ° C. or higher, and a bonding material,
Item 2. The polyethylene glycol having 8 to 200 carbon atoms and the contained organic compound (A) are represented by the compound represented by the following general formula (1), the compound represented by the following general formula (2), and the following general formula (3). Or a (meth) acrylic polymer (polymer α) having a structure represented by the following general formula (4) at least at one end and having a polyethylene glycol chain (P) in the side chain, (Meth) acrylic polymer having a structure represented by the following general formula (4) at one end and a phosphate ester residue represented by —OP (O) (OH) ₂ in the side chain ( Item 2. A bonding material according to Item 1, which is a compound containing polymer β).
W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —SX (1)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—] _d Y (2)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—R ^a —] _t Z (3)
[W in the formulas (1), (2) and (3) is a C ₁ to C ₈ alkyl group, n is an integer indicating the number of repetitions of 4 to 100, and X is C ₂ to C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, —R ¹ —OH, —R ¹ —NHR ² , or —R ¹ — (COR ³ ) _m (where R ¹ is C ₁ -C ₄ saturation) R ² is a hydrogen atom, a C ₂ -C ₄ acyl group, a C ₂ -C ₄ alkoxycarbonyl group, or a C ₁ -C ₄ alkyl group or C ₁ -C ₈ on the aromatic ring. A benzyloxycarbonyl group optionally having an alkoxy group as a substituent, R ³ is a hydroxy group, a C ₁ -C ₄ alkyl group or a C ₁ -C ₈ alkoxy group, and m is 1 to 3 is an integer of 3), and Y is carbon directly bonded to a sulfur atom. A is a divalent to tetravalent radical _atom, a saturated hydrocarbon group having a saturated hydrocarbon group or a _C 1 ~ _{C 4} of C 1 ~ _{C 4} is -O -, - S- or -NHR ^{^b} - ^(R ^b Is a C ₁ to C ₄ saturated hydrocarbon group), d is an integer of 2 to 4, and R ^a is a C ₂ to C ₅ alkylcarbonyloxy group. Z is a divalent to hexavalent group in which a carbon atom is directly bonded to a sulfur atom, and a C ₂ to C ₆ saturated hydrocarbon group or a C ₂ to C ₆ saturated hydrocarbon group is —O— , —S— or —NHR ^c — (R ^c is a saturated hydrocarbon group of C ₁ to C ₄ ), or isocyanuric acid —N, N ′, N ″ -triethylene And t is an integer of 2 to 6.]
RS (4)
[In the general formula (4), R represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, or a C 1 to 18 carbon atom. A branched alkoxy group, an aralkyloxy group, a substituted phenyloxy group, a linear alkylcarbonyloxy group having 1 to 18 carbon atoms, a branched alkylcarbonyloxy group having 1 to 18 carbon atoms, a carboxy group, a salt of a carboxy group, Straight chain alkoxycarbonyl group having 1 to 18 carbon atoms, branched alkoxycarbonyl group having 1 to 18 carbon atoms, phosphoric acid group, straight chain alkylphosphoric acid group having 1 to 6 carbon atoms, and 1 to 6 carbon atoms Selected from the group consisting of branched alkyl phosphate groups, sulfonic acid groups, linear alkyl sulfonic acid groups having 1 to 6 carbon atoms, and branched alkyl sulfonic acid groups having 1 to 6 carbon atoms. Even without a linear or branched alkyl group having 1 to 8 carbon atoms having a single functional group. ]
Item 3. The polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms is represented by the compound represented by the following general formula (1), the compound represented by the following general formula (2), or the following general formula (3). Item 2. A bonding material according to Item 1, which is a compound.
W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —SX (1)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—] _d Y (2)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—R ^a —] _t Z (3)
[W in the formulas (1), (2) and (3) is a C ₁ to C ₈ alkyl group, n is an integer indicating the number of repetitions of 4 to 100, and X is C ₂ to C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, —R ¹ —OH, —R ¹ —NHR ² , or —R ¹ — (COR ³ ) _m (where R ¹ is C ₁ -C ₄ saturation) R ² is a hydrogen atom, a C ₂ -C ₄ acyl group, a C ₂ -C ₄ alkoxycarbonyl group, or a C ₁ -C ₄ alkyl group or C ₁ -C ₈ on the aromatic ring. A benzyloxycarbonyl group optionally having an alkoxy group as a substituent, R ³ is a hydroxy group, a C ₁ -C ₄ alkyl group or a C ₁ -C ₈ alkoxy group, and m is 1 to 3 is an integer of 3), and Y is carbon directly bonded to a sulfur atom. A is a divalent to tetravalent radical _atom, a saturated hydrocarbon group having a saturated hydrocarbon group or a _C 1 ~ _{C 4} of C 1 ~ _{C 4} is -O -, - S- or -NHR ^{^b} - ^(R ^b Is a C ₁ to C ₄ saturated hydrocarbon group), d is an integer of 2 to 4, and R ^a is a C ₂ to C ₅ alkylcarbonyloxy group. Z is a divalent to hexavalent group in which a carbon atom is directly bonded to a sulfur atom, and a C ₂ to C ₆ saturated hydrocarbon group or a C ₂ to C ₆ saturated hydrocarbon group is —O— , —S— or —NHR ^c — (R ^c is a saturated hydrocarbon group of C ₁ to C ₄ ), or isocyanuric acid —N, N ′, N ″ -triethylene And t is an integer of 2 to 6.]
Item 4. Item 2. The bonding material according to Item 1, wherein the solvent (C) is at least one solvent selected from the group consisting of an alcohol solvent having a boiling point of 150 ° C or higher and an ether solvent having a boiling point of 150 ° C or higher.
Item 5. Item 2. The bonding material according to Item 1, wherein the metal nanoparticles (B) are silver nanoparticles, copper nanoparticles, silver core copper shell nanoparticles, or copper core silver shell nanoparticles, or
Item 6. Item 2. The bonding material according to Item 1, wherein the content of the polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms in the metal nanoparticles is 2 to 15% by mass.
Item 7. Item 7. The bonding material according to any one of Items 1 to 6, wherein the objects to be bonded are metals or metal oxides.

According to the present invention, bonding is possible with high strength under no pressure condition and at a low temperature condition of 200 ° C. or less.

Next, an embodiment of the present invention will be described.

<Metal species in metal nanoparticles>
The metal species of the metal nanoparticles (B) of the present invention are not particularly limited as long as the later-described polyethylene glycol-containing organic compound can be combined, and preferably copper (Cu) -based, silver (Ag) -based Is preferred. Examples of the copper-based and silver-based nanoparticles include copper nanoparticles, silver nanoparticles, silver core copper shell nanoparticles, copper core silver shell nanoparticles, and the like. Among these, copper nanoparticles are more preferable.

<Polyethylene glycol-containing organic compound>
The polyethylene glycol moiety in the protective agent (polyethylene glycol-containing organic compound) used in the present invention is excellent in affinity with the specific solvent of the present invention such as an alcohol solvent having a boiling point of 150 ° C. or higher. Can be strongly suppressed, and high dispersion of metal nanoparticles can be achieved. In other words, since the metal nanoparticles are packed in a high density, void generation due to decomposition and removal of the protective agent and solvent by heat treatment does not occur, and high density bonding is possible by the necking phenomenon between metal particles. And enables high strength bonding under no pressure condition. In addition, the metal nanoparticles synthesized using the protective agent of the present invention have a small amount of protective agent of about 2 to 15%, do not hinder the necking phenomenon between the metal particles at the time of bonding, and have organic components after bonding. Since it hardly remains, it has high reliability as a high heat-resistant bonding agent.
Examples of metal nanoparticles containing a polyethylene glycol-containing organic compound having 8 to 200 carbon atoms contained in the bonding material of the present invention include Japanese Patent No. 4784847, Japanese Patent Application Laid-Open No. 2013-60637, or Japanese Patent No. 5077728. It can be synthesized by the method described in 1. These are characterized in that the thioether type (RS—R ′) compound has an appropriate affinity adsorption effect on the metal particle surface and rapid detachment by heating, and exhibits low-temperature fusion characteristics. Developed as shown metal nanoparticles.
As another example, among the polymer compounds having a thioether group described in JP-A 2010-209421, metal nanoparticles in which a polymer compound having a polyethylene glycol moiety having 8 to 200 carbon atoms is combined, Among the polymer compounds having a thioether group and a phosphate ester group described in Japanese Patent No. 4697356, there are metal nanoparticles in which a polymer compound having a polyethylene glycol moiety having 8 to 200 carbon atoms is complexed. . These polyethylene glycol-containing polymer compounds can be produced according to the methods described in these publications. Further, in the present invention, these polyethylene glycol-containing phosphate ester-type organic compounds have a thioether group and also a phosphate ester group, and by having these groups, the metal nanoparticle surface is reduced. Appropriate affinity adsorption effect and rapid desorption by heating can be imparted.
Among these, thioether type organic compounds represented by the following formulas (1) to (3) are preferable.

<Thioether (RSR) type organic compound>
As an example for explaining the effect of the present invention, copper-based and silver-based nanoparticles combined with thioether type organic compounds represented by the following general formulas (1) to (3) will be described in detail.

W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —SX (1)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—] _d Y (2)
[W— (OCH ₂ CH ₂ ) _n —O—CH ₂ —CH (OH) —CH ₂ —S—R ^a —] _t Z (3)

[W in the formulas (1), (2) and (3) is a C ₁ to C ₈ alkyl group, n is an integer indicating the number of repetitions of 4 to 100, and X is C ₂ to C ₁₂ Alkyl group, allyl group, aryl group, arylalkyl group, —R ¹ —OH, —R ¹ —NHR ² , or —R ¹ — (COR ³ ) _m (where R ¹ is C ₁ -C ₄ saturation) R ² is a hydrogen atom, a C ₂ -C ₄ acyl group, a C ₂ -C ₄ alkoxycarbonyl group, or a C ₁ -C ₄ alkyl group or C ₁ -C ₈ on the aromatic ring. A benzyloxycarbonyl group optionally having an alkoxy group as a substituent, R ³ is a hydroxy group, a C ₁ -C ₄ alkyl group or a C ₁ -C ₈ alkoxy group, and m is 1 to 3 is an integer of 3), and Y is carbon directly bonded to a sulfur atom. A is a divalent to tetravalent radical _atom, a saturated hydrocarbon group having a saturated hydrocarbon group or a _C 1 ~ _{C 4} of C 1 ~ _{C 4} is -O -, - S- or -NHR ^{^b} - ^(R ^b Is a C ₁ to C ₄ saturated hydrocarbon group), d is an integer of 2 to 4, and R ^a is a C ₂ to C ₅ alkylcarbonyloxy group. Z is a divalent to hexavalent group in which a carbon atom is directly bonded to a sulfur atom, and a C ₂ to C ₆ saturated hydrocarbon group or a C ₂ to C ₆ saturated hydrocarbon group is —O— , —S— or —NHR ^c — (R ^c is a saturated hydrocarbon group of C ₁ to C ₄ ), or isocyanuric acid —N, N ′, N ″ -triethylene And t is an integer of 2 to 6.]

The chain-like functional group having ethylene glycol as a repeating unit in the general formulas (1) to (3) functions as a solvent affinity part. The polyethylene glycol preferably has 8 to 200 carbon atoms, and more preferably has 8 to 100 carbon atoms.
In addition, the chain functional group having ethylene glycol as a repeating unit in the general formulas (1) to (3) has a high number of carbon atoms of about 8 to 12 because the smaller the number of carbon atoms, the less the organic component remains. More preferable as a bonding agent having reliability.
On the other hand, chain functional groups having ethylene glycol as a repeating unit in the general formulas (1) to (3) having about 50 to 100 carbon atoms are excellent in dispersion stability and highly disperse metal nanoparticles. It is more preferable in terms of improving the bonding strength under no pressure condition.
Therefore, the carbon number can be appropriately adjusted in the range of 8 to 200 or more preferably in the range of 8 to 100 according to the usage scene.

W in the general formulas (1) to (3) is a linear or branched carbon number of 1 to 8 from the viewpoint of industrial availability and dispersion stability when used as a protective agent. From the viewpoint of stability in an aqueous medium, an alkyl group having 1 to 4 carbon atoms is preferable.

A structure in which X in the general formula (1) includes a carboxyl group, an alkoxycarbonyl group, a carbonyl group, an amino group, or an amide group as a partial structure can constitute a thioether group and a polydentate ligand. Therefore, it is preferable because the coordination force to the surface of the metal nanoparticle becomes strong.

Y in the general formula (2) has a structure containing ether (C—O—C) and thioether (C—S—C) as a partial structure, and R ^a in the general formula (3) is a methylene carboxy group (—CH ₂ COO—) or an ethylene carboxy group (—CH ₂ CH ₂ COO—), wherein Z is an ethylene group, 2-ethyl-2-methylenepropane-1,3-diyl group, 2,2-bis Most preferred is a methylenepropane-1,3-diyl group.

<Method for producing thioether type organic compound>
As described above, in the present invention, the thioether-type organic compound is preferably a compound represented by the general formulas (1) to (3). The method for producing these thioether type organic compounds will be described in detail below.

Examples of a method for easily producing a thioether-type organic compound include a method in which a polyether compound (a1) having a glycidyl group at the terminal and a thiol compound (a2) are reacted.

The polyether compound (a1) having the glycidyl group at the end can be represented by the following general formula (5).

(Wherein, W, R ¹ and n are the same as above.)
As a method for synthesizing the polyether compound (a1) having a glycidyl group at its terminal, for example, a chlorohydrin produced by adding and opening a polyethylene glycol monoalkyl ether to an oxirane ring of epichlorohydrin in the presence of a Lewis acid. There are a method of heating and re-ringing in a concentrated alkali and a method of reacting in a single step using a strong base such as excess alcoholate or concentrated alkali. As a method of obtaining a higher purity polyether compound (a1) Uses a method of Gandour et al. (Gandour, et al.) Which uses polyethylene tert-butoxide to convert polyethylene glycol monomethyl ether into an alkoxide, condenses this with epichlorohydrin, and then continues heating to reform the epoxy ring. J. Org.Chem., 1983, 48, 1 116.) is preferably applied mutatis mutandis.

The terminal oxirane ring of the polyether compound (a1) having the glycidyl group at the terminal can be opened with the thiol compound (a2) to obtain the desired thioether-type organic compound. This reaction uses a nucleophilic reaction of a thiol group, and various activation methods can be mentioned for this reaction.
For example, synthesis by activation of an epoxide with a Lewis acid has been widely performed. Specifically, it is known to use zinc tartrate or a lanthanide Lewis acid. In addition, a method using a Lewis base is often performed.

Furthermore, the method of utilizing fluorine ions as a base catalyst is described in James H. et al. It is described in detail in Clark's review. Penso et al. Have applied this as a ring opening method for epoxides with excellent regioselectivity, and by using quaternary ammonium fluoride as a catalyst, addition ring opening reaction of thiol to epoxide proceeds under mild conditions. It is reported that.

In particular, from the viewpoint that the thioether-type organic compound used in the present invention can be obtained with high efficiency, a method utilizing fluorine ions as a base catalyst is preferred. By applying this method, a thioether-type organic compound can be obtained without any special purification after the reaction between the polyether compound (a1) having a glycidyl group at the terminal and the thiol compound (a2).

The polyether compound (a1) can be reacted with various thiol compounds (a2). Examples include alkanethiols and benzenethiols, thioglycol, thioglycolic acid and esters thereof, mercaptopropionic acid and esters thereof which are easily available because they are widely used as radical polymerization chain transfer agents. Mercaptopolycarboxylic acids such as thiomalic acid, thiocitric acid and their esters may be reacted. Further, compounds having a plurality of thiol groups in the molecule, that is, alkylenedithiols such as ethanedithiol, trimethylolpropane = tris (3-mercaptopropionate), pentaerythritol = tetrakis (3-mercaptopropionate), Dipentaerythritol = hexakis (3-mercaptopropionate) and the like can be similarly reacted and introduced. Since the compound obtained as a result has a plurality of thioether structures in the molecule, it can exhibit affinity for the copper-based nanoparticles by a plurality of regions.

<Polyphosphate type organic compound containing polyethylene glycol>
As an example for explaining the effect of the present invention, copper-based and silver-based nanoparticles combined with a polyethylene glycol-containing phosphate ester-type organic compound will be described in detail.
The compound used in the present invention is a (meth) acrylic polymer (polymer α) having a structure represented by the following general formula (4) at at least one terminal and having a polyethylene glycol chain (P) in the side chain. And (meth) acrylic having a structure represented by the following general formula (4) at at least one terminal and a phosphate ester residue represented by —OP (O) (OH) ₂ in the side chain A compound containing a polymer (polymer β),
RS (4)
[In the general formula (4), R represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, or a C 1 to 18 carbon atom. A branched alkoxy group, an aralkyloxy group, a substituted phenyloxy group, a linear alkylcarbonyloxy group having 1 to 18 carbon atoms, a branched alkylcarbonyloxy group having 1 to 18 carbon atoms, a carboxy group, a salt of a carboxy group, Straight chain alkoxycarbonyl group having 1 to 18 carbon atoms, branched alkoxycarbonyl group having 1 to 18 carbon atoms, phosphoric acid group, straight chain alkylphosphoric acid group having 1 to 6 carbon atoms, and 1 to 6 carbon atoms Selected from the group consisting of branched alkyl phosphate groups, sulfonic acid groups, linear alkyl sulfonic acid groups having 1 to 6 carbon atoms, and branched alkyl sulfonic acid groups having 1 to 6 carbon atoms. Even without a linear or branched alkyl group having 1 to 8 carbon atoms having a single functional group. ]
Here, the suitable carbon number of polyethylene glycol is the same as that of the above-mentioned thioether type organic compound.

<Method for producing polyethylene glycol-containing phosphate ester type organic compound>
As the thiol compound (Q) used for obtaining a polymer compound having a structure represented by the general formula (4) in the molecule, a thiol compound generally used as a chain transfer agent can be used. Specifically, thioglycol, 2-mercaptopropanol, 3-mercaptopropanol, 8-mercaptooctanol, 2,3-dihydroxypropanethiol, 2-methoxyethanethiol, 2-ethoxyethanethiol, 2-hexyloxyethanethiol, 2- (2-ethylhexyloxy) ethanethiol, 2-benzyloxyethanethiol, 2- (4-methoxybenzyloxy) ethanethiol, 2-phenyloxyethanethiol, 2- (4-methoxyphenyloxy) ethanethiol, 2 -(2,4-dimethoxyphenyloxy) ethanethiol, 6- (4-hydroxymethylphenyloxy) hexanethiol, 2-acetoxyethanethiol, 2-heptanoyloxyethanethiol, 2-octanoyloxyeta Thiol, 2-octadecanoyloxyethanethiol, 2-isobutyryloxyethanethiol, 2-pivaloyloxyethanethiol, thioglycolic acid, β-mercaptopropionic acid, 7-mercaptooctanoic acid, 2-mercaptopropionic acid , 2-mercaptosuccinic acid, and inorganic salts, ammonium salts and organic amine salts of these carboxylic acids, methyl thioglycolate, ethyl thioglycolate, octyl thioglycolate, ethyl β-mercaptopropionate, β-mercaptopropionic acid Octyl, β-mercaptopropionic acid dodecyl, β-mercaptopropionic acid-2- (methoxyethyl), β-mercaptopropionic acid-2- (methoxyethoxyethoxy), β-mercaptopropionic acid-2- (4-methoxybutoxy) , Thioglycolic acid-2-ethylhexyl, β-mercaptopropionic acid-2-ethylhexyl, β-mercaptopropionic acid-3-methoxybutoxy, 2-mercaptoethyl phosphate, 2-mercaptoethylphosphinic acid, 2-mercaptopropyl phosphate, 2-mercaptopropyl phosphinic acid, ω-mercaptoethoxyethyl phosphate, ω-mercaptopropyloxypropyl phosphate, 2-mercaptoethyl dimethyl phosphate, dimethyl 2-mercaptoethyl phosphinate, 2-mercaptoethyl diethyl phosphate, 2- Mercaptopropyl diethyl phosphate, 2-mercaptoethyl diisopropyl phosphate, 2-mercaptoethyl diisobutyl phosphate, 2-mercaptoethyl sulfate, 2 Mercaptoethyl sulfonic acid, 2-mercaptopropyl sulfonic acid, 2-mercaptoethyl methyl sulfate, methyl 2-mercaptoethyl sulfonate, 2-mercaptoethyl ethyl sulfate, ethyl 2-mercaptoethyl sulfonate, methyl 2-mercaptopropyl sulfone Nert, ethyl 2-mercaptopropyl sulfonate and the like. Among them, when thioglycol, 2,3-dihydroxypropanethiol, thioglycolic acid, β-mercaptopropionic acid, ethyl β-mercaptopropionate, and 2-ethylhexyl β-mercaptopropionate are reactive, readily available, and thinned In view of surface smoothness, methyl β-mercaptopropionate is most preferable.

There is no limitation in particular as a polymeric compound made to react with the said thiol compound (Q), A well-known polymeric compound can be used. Specifically, (meth) acrylic acid, (meth) acrylic acid ester compounds, vinyl alcohol ester compounds, styrene compounds, allyl alcohol compounds, allylamine compounds, and the like.
The protective agent for metal nanoparticles of the present invention can be designed according to the metal species to be used and the desired physical properties by appropriately selecting a polymerizable compound having a functional group having an affinity for metal. Possible and characteristic. Specifically, a carboxy group, a phosphoric acid group, a sulfonic acid group, or a heteroaromatic group (for example, an imidazole group) having a slightly strong adsorption ability for a metal, shows a moderate interaction, and depends on the liquidity of the dispersion medium. An amino group (for example, dimethylaminoethyl group, dimethylaminopropyl group) whose adsorptive capacity changes, and a hydroxy group (hydroxyethyl group, hydroxypropyl group), an aromatic group (for example, a smaller interaction with the metal surface than the former) By using a polymerizable compound having a benzyl group), it is possible to freely give the functional group to the protective agent for metal nanoparticles, and it is possible to freely change these ratios, The adsorptivity can also be changed freely.
For example, by using a polymerizable compound having a polyethylene glycol chain such as polyalkylene glycol methacrylate as the polymerizable compound, the polymer compound having a structure represented by the general formula (4) in the molecule is added to the polyethylene glycol chain. Can be incorporated.
Similarly, by using (meth) acrylic acid or the like as a polymerizable compound, a carboxy group is used, a dimethylaminoethyl methacrylate or the like is used, an amino group is used, or methacryloyloxyethyl phosphate or the like is used. Hydroxy group by using hydroxyethyl methacrylate, etc. Acid group, sulfonic acid group using modified (meth) acrylic acid ester having sulfonic acid group as polymerizable compound, heteroaromatic compound by using heteroaromatic vinyl compound Aromatic groups can be introduced. Thus, an amino group, a carboxy group, an imidazole group, a phosphoric acid group, a sulfonic acid group, or the like can be incorporated into the polymer compound having the structure represented by the general formula (4) in the molecule.
Specific examples of these polymerizable compounds include 2-dimethylaminoethyl methacrylate, vinylimidazole, 2-methacryloyloxyethyl phosphate, and 2-acrylamido-2-methylpropanesulfonic acid.
The polymerization method of the protective agent for metal nanoparticles according to the present invention may be an ordinary radical polymerization method. The thiol compound and the polymerizable compound may be dissolved in an appropriate solvent, and a percarboxylic acid ester or the like may be added and heated as a polymerization initiator. .

<Synthesis of Copper or Silver Nanoparticles Composed of Polyethylene Glycol-Containing Organic Compounds with 8 to 200 Carbons>
As an example for explaining the effect of the present invention, a method for producing metal nanoparticles in which a polyethylene glycol-containing organic compound having 8 to 200 carbon atoms contained in the bonding material of the present invention is combined is described in the presence of a thioether type organic compound. It has the process of mixing a bivalent copper ion compound or a monovalent silver ion compound with a solvent, and the process of reduce | restoring a copper ion or a silver ion, It is characterized by the above-mentioned.

As the divalent copper ion compound, generally available copper compounds can be used, and sulfates, nitrates, carboxylates, carbonates, chlorides, acetylacetonate complexes and the like can be used. In the case of obtaining a complex with zero-valent copper nanoparticles, the complex may start from a divalent compound or may be produced from a monovalent compound, or may have moisture or crystal water. Specifically, if expressed excluding crystal water, CuSO ₄ , Cu (NO ₃ ) ₂ , Cu (OAc) ₂ , Cu (CH ₃ CH ₂ COO) ₂ , Cu (HCOO) ₂ , CuCO ₃ , CuCl ₃ ₂ , Cu ₂ O, C ₅ H ₇ CuO _{2 and the} like. Further, basic salts obtained by heating the above salts or exposing them to a basic atmosphere, such as Cu (OAc) ₂ .CuO, Cu (OAc) ₂ .2CuO, Cu ₂ Cl (OH) _3, etc. Most preferably, it can be used. These basic salts may be prepared within the reaction system, or those prepared separately outside the reaction system may be used. Further, a general method can be applied in which ammonia or an amine compound is added to form a complex to ensure solubility and then used for the reduction.

As the monovalent silver ion compound, generally available silver compounds can be used. Silver nitrate, silver oxide, silver acetate, silver fluoride, silver acetylacetonate, silver benzoate, silver carbonate, silver citrate Silver hexafluorophosphate, silver lactate, silver nitrite, silver pentafluoropropionate, and the like. From the viewpoint of ease of handling and industrial availability, silver nitrate or silver oxide is preferably used.

These copper or silver ion compounds are dissolved or mixed in a medium in which a thioether type organic compound is previously dissolved or dispersed. As the medium that can be used at this time, although depending on the structure of the organic compound to be used, water, ethanol, acetone, ethylene glycol, diethylene glycol, glycerin and a mixture thereof are preferably used, and a water-ethylene glycol mixture is particularly preferable. preferable.

The concentration of the thioether-type organic compound in various media is preferably adjusted to a range of 0.3 to 10% by mass from the viewpoint of easy control of the subsequent reduction reaction.

In the medium prepared above, the copper or silver ion compound is added all at once or divided and mixed. In the case of using a medium that is difficult to dissolve, a method in which the medium is dissolved in a small amount of a good solvent in advance and then added to the medium may be used.

The proportion of the thioether-type organic compound to be mixed and the copper or silver ion compound is preferably selected as appropriate according to the protective ability of the thioether-type organic compound in the reaction medium, but usually 1 mol of copper or silver ion compound. The thioether-type organic compound is prepared in the range of 1 mmol to 30 mmol (about 2 to 60 g when a polymer having a molecular weight of 2000 is used), and particularly preferably used in the range of 15 to 30 mmol.

Subsequently, copper or silver ions are reduced using various reducing agents. Examples of reducing agents include hydrazine compounds, hydroxylamine and its derivatives, metal hydrides, phosphinates, aldehydes, enediols, hydroxyketones, etc. A compound that can be allowed to proceed is preferred because it provides a complex with less precipitate formation.

In the reduction of copper ions, specifically, strong reducing agents such as hydrazine hydrate, asymmetric dimethylhydrazine, hydroxylamine aqueous solution, sodium borohydride and the like are suitable. Since these have the ability to reduce the copper compound to zero valence, the divalent and monovalent copper compounds are reduced copper and are suitable for producing a composite of an organic compound and nano-copper particles.

The conditions suitable for the reduction reaction vary depending on the copper compound used as a raw material, the type of reducing agent, the presence or absence of complexation, the medium, and the type of thioether type organic compound. For example, when copper (II) acetate is reduced with sodium borohydride in an aqueous system, zero-valent nano copper particles can be prepared even at a temperature of about ice cooling. On the other hand, when hydrazine is used, the reaction is slow at room temperature, and a smooth reduction reaction occurs only after heating to about 60 ° C., and when copper acetate is reduced in an ethylene glycol / water system, about 60 hours at 60 ° C. The reaction time is required. When the reduction reaction is completed in this manner, a reaction mixture containing a complex of an organic compound and copper-based nanoparticles is obtained.

In the reduction of silver ions, specifically, reducing agents such as dimethylaminoethanol and sodium citrate are suitable. These are capable of reducing silver ions to zero valence under relatively mild conditions. In the case of reducing silver nitrate in an aqueous system, the reduction reaction is completed by carrying out the reaction at 40 ° C. for about 2 hours, A reaction mixture containing a complex of organic compound and silver-based nanoparticles is obtained.

Due to the effect of the protective agent, the metal nanoparticles prepared in this way can be completely dispersed in the same way as before drying even after the solvent is added again after completely removing moisture to form a dry powder. It is.

In addition, when a mixed liquid in which nano silver is added to a mixed liquid of a thioether type organic compound, the medium, and the copper ion compound is prepared in advance, and then a reducing agent is added to reduce the copper ions by the above method, nano silver is obtained. Silver core copper shell nanoparticles whose surface is coated with copper can be obtained.

Conversely, when a liquid mixture in which nanocopper is added to a liquid mixture of a thioether-type organic compound and the medium and a silver ion compound is prepared in advance, and then a reducing agent is added to reduce silver ions by the above method, The copper core silver shell nanoparticle which silver coat | covered the nanocopper surface can be obtained.

<Method for producing dispersion>
After the reduction reaction, a step of removing a metal compound residue, a reducing reagent residue, an excess polyethylene glycol-containing organic compound and the like is provided as necessary. For the purification of the complex, reprecipitation, centrifugal sedimentation or ultrafiltration can be applied, and the reaction mixture containing the resulting complex is washed with a washing solvent such as water, ethanol, acetone and a mixture thereof. The aforementioned impurities can be washed away.

<Method for manufacturing joining material>
As described above, the metal nanoparticle-organic compound composite is obtained as an aqueous dispersion. In the final stage of purification, instead of adding a cleaning solvent to the composite, an easy-to-use solvent is added as a bonding material, or By exchanging the medium, suitability as a bonding material can be imparted.

The bonding material can obtain higher bonding strength as the metal concentration in the material is higher, but on the other hand, it is necessary to supply the material to the bonding part by application, dispenser, mask printing, screen printing, etc. It is necessary to add a viscosity adjusting solvent or an additive or adjust the concentration of the metal contained in the material so that the characteristics are suitable. Therefore, the metal concentration of the aqueous dispersion is adjusted so that the maximum metal concentration is obtained in the viscosity range suitable for the printing method. Generally, about 50 to 95% is preferable because it can be easily supplied to the joint.

The bonding material of the present invention can be used by adding metal nanoparticles having a particle size of about 200 to 1000 nm.

The joining material of the present invention can be used with a further reducing power by adding a flux component.

The bonding material prepared in this way is stable for about 1 to 3 months regardless of the preparation concentration if stored in a closed container.

The level said to be practically sufficient in the technical field of the present invention is that a strength of 15 MPa or more is obtained in a shear strength test described later. The bonding material of the present invention exhibits a strength of 15 MPa or more, and preferably exhibits a strength of 20 MPa or more. Moreover, a particularly preferable material for the bonding of the present invention is one that can obtain a strength of 30 MPa or more.

<Solvent (C) of the present invention>
Examples of the solvent (C) that can be used in the present invention include alcohol solvents having a boiling point of 150 ° C. or higher, ether solvents having a boiling point of 150 ° C. or higher, ester solvents having a boiling point of 150 ° C. or higher, and lactam structure-containing solvents having a boiling point of 150 ° C. or higher. Etc. can be used suitably.

Here, the alcohol solvent having a boiling point of 150 ° C. or more specifically includes monofunctional alcohol types such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, decyl alcohol, ethylene glycol, propylene glycol, diethylene glycol, and triethylene. Bifunctional alcohol types such as glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, trifunctional alcohol types such as propanetriol, butanetriol, pentanetriol, hexanetriol, heptanetriol, propanetetraol, butane Tetrafunctional alcohol types such as tetraol, pentanetetraol, hexanetetraol, heptanetetraol, pentanepentaol, hexa Those penta-functional alcohol type, such as penta ol. It is also possible to use alcohol compounds having a cyclic structure such as benzenetriol, biphenylpentaol, benzenepentaol, and cyclohexanehexaol. In addition, compounds having an alcohol group such as citric acid and ascorbic acid may be used. Further, alcohol derivatives containing an ether structure, such as propylene glycol monomethyl ether, 3-methoxybutanol, propylene glycol-n-propyl ether, propylene glycol-n-butyl ether, dipropylene glycol methyl ether, diethylene glycol monoethyl ether, dipropylene glycol -N-propyl ether, dipropylene glycol-n-butyl ether, tripropylene glycol methyl ether, tripropylene glycol-n-butyl ether and the like may be used.

Here, specific examples of the ether solvent having a boiling point of 150 ° C. or higher include polyethylene glycol and polypropylene glycol having a molecular weight of 200 to 400.

Here, the ester solvent having a boiling point of 150 ° C. or more specifically includes cyclohexanol acetate, dipropylene glycol dimethyl ether, propylene glycol diacetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1 , 4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, and crown ethers having a cyclic structure.

Here, the lactam structure-containing solvent having a boiling point of 150 ° C. or more specifically includes β-lactams such as β-lactam, ε-caprolactam, σ-lactam, N-methyl-2-pyrrolidone, pyroglutamic acid, piracetam, and penicillin. System compounds and the like.

Among them, it is preferable to use an alcohol solvent having a boiling point of 150 ° C. or higher and an ether solvent having a boiling point of 150 ° C. or higher.
Among them, more preferably, an alcohol solvent having a boiling point of 150 ° C. or higher of a bifunctional alcohol type such as ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, propanediol, butanediol, pentanediol, hexanediol, heptanediol, An ether solvent at 150 ° C. or higher is preferred.

Of these, ethylene glycol, diethylene glycol, and polyethylene glycol having a molecular weight of 200 to 400 are more preferable.

It can be used if the amount used is in the range of 5 to 50% with respect to the metal, and more preferably in the range of 5 to 15%.

<Joint>
The bonding material thus prepared is applied to two copper rods (diameter 10 mm × thickness 5 mm, diameter 3 mm × thickness 2 mm) previously washed with dilute hydrochloric acid, and the copper or silver is applied as it is or slightly pressed. It is possible to produce a joining test piece by heating to a temperature at which the nanoparticles are fused. At this time, it can also be carried out under a forming gas containing hydrogen, in a nitrogen atmosphere, or in an atmosphere of formic acid-containing nitrogen that has been passed through formic acid.

When heated for bonding, the polyethylene glycol site and metal coordination site complexed with copper or silver nanoparticles at 200 ° C. or lower decompose and volatilize.

In the present invention, examples of members to be bonded (bonded objects) include metals (including alloys and intermetallic compounds), ceramics, plastics, composite materials thereof, and the like. Including joining of alloys and metals) is preferred. Further, the shape of the member is not particularly limited as long as these powders or pastes can be appropriately disposed between the members.

<Bonding strength measurement>
In accordance with the method described in JIS Z-03918-5: 2003 “Lead-free solder test method”, a shear force was applied to the above-mentioned joint test piece, and the joint strength was measured. In this specification, it is also called a shear strength test.

Hereinafter, the present invention will be described by way of examples. Unless otherwise specified, “%” is based on mass.

Synthesis example 1
<Synthesis of Copper Nanoparticles Compounded with Polyethylene Glycol-Containing Organic Compounds (Thioether Type Organic Compounds (A1) to (A4)) having 8 to 200 carbon atoms>
Copper (II) acetate monohydrate (3.00 g, 15.0 mmol), ethyl 3- (3- (methoxy (polyethoxy) ethoxy) -2-hydroxypropylsulfanyl) propionate [polyethylene glycol methyl glycidyl ether (polyethylene glycol chain) The molecular weight of 200 (carbon number 8), 1000 (carbon number 46) 2000 (carbon number 91), 3000 (carbon number 136)) methyl 3-mercaptopropionate addition compound (depending on the molecular weight of the polyethylene glycol chain, respectively) Thioether type organic compounds (A1), (A2), (A3), (A4)), the following formula] (0.451 g)

The mixture consisting of ethylene glycol (10 mL) was heated while blowing nitrogen at a flow rate of 50 mL / min, and deaerated by aeration and stirring at 125 ° C. for 2 hours. The mixture was returned to room temperature, and a solution of hydrazine hydrate (1.50 g, 30.0 mmol) diluted with 7 mL of water was slowly added dropwise using a syringe pump. About 1/4 amount was slowly dropped over 2 hours. The dropping was temporarily stopped here, and after stirring for 2 hours, it was confirmed that foaming subsided, and then the remaining amount was further dropped over 1 hour. The resulting brown solution was heated to 60 ° C. and further stirred for 2 hours to complete the reduction reaction.

<Preparation of aqueous dispersion>
Subsequently, this reaction mixture is circulated through a hollow fiber type ultrafiltration membrane module (HIT-1-FUS1582, 145 cm ² , molecular weight cut off 150,000) manufactured by Daisen Membrane Systems Co., Ltd., and the same amount as the leached filtrate. A 0.1% hydrazine hydrate aqueous solution was added and circulated until the filtrate from the ultrafiltration module reached about 500 mL for purification. When the supply of the 0.1% hydrazine hydrate aqueous solution was stopped and the solution was directly concentrated by ultrafiltration, an aqueous dispersion of copper nanoparticles in which 2.85 g of the thioether-type organic compounds (A1) to (A4) were combined ( a1) to (a4) were obtained. The non-volatile content in the aqueous dispersions (a1) to (a4) was 16%, and the metal content in the non-volatile materials was 95%.
A thioether type organic compound (A1) having a molecular weight of polyethylene glycol chain of 200 is a thioether type organic compound (A1), a thioether type organic compound (A2) having a molecular weight of 1000, and a thioether type organic compound (A3) having a molecular weight of 2000. A compound having a molecular weight of 3000 is referred to as a thioether type organic compound (A4). Also, aqueous dispersions of copper nanoparticles combined with thioether-type organic compounds (A1) to (A4) are referred to as (a1) to (a4), respectively.

Synthesis example 2
<Synthesis of Silver Nanoparticles Combining a Polyethylene Glycol-containing Organic Compound (Thioether Type Organic Compound (A3)) with 8 to 200 carbon atoms>
Distillation of dimethylaminoethanol (1.78 g, 20 mmol) as a reducing agent into a mixture of silver nitrate (I) (2.55 g, 15.0 mmol), 0.451 g of thioether type organic compound (A3) and distilled water (10 mL) A mixture of 16.02 g of water was dropped using a dropping funnel over 20 minutes, and then heated at 40 ° C. for 2 hours to terminate the reduction reaction, thereby obtaining a black silver nanoparticle reaction mixture.

<Preparation of aqueous dispersion>
Subsequently, this reaction mixture was circulated in a hollow fiber type ultrafiltration membrane module (HIT-1-FUS1582, 145 cm ² , molecular weight cut off 150,000) manufactured by Daisen Membrane Systems Co., Ltd. Purification by circulating until the filtrate was about 500 mL. When concentrated as it was by ultrafiltration, an aqueous dispersion (b) of a complex of 2.15 g of the thioether type organic compound (A3) and silver nanoparticles was obtained. The non-volatile content in the aqueous dispersion (b) was 16%, and the metal content in the non-volatile was 95%.

Test example 1
By enclosing 5 mL of each of the above aqueous dispersions (a1) to (a4) in a 50 mL three-necked flask and heating them to 40 ° C. using a water bath, flowing nitrogen at a flow rate of 5 ml / min under reduced pressure. The water was completely removed to obtain 1.0 g of a dry powder of copper nanoparticle composite. Next, 0.1 g of ethylene glycol bubbled with nitrogen for 30 minutes was added in the glove bag substituted with argon gas to the obtained dry powder, and then mixed for 10 minutes in a mortar to obtain a copper nanoparticle paste having a nonvolatile content of 91%. Obtained.
The obtained copper nanoparticle paste was screen-coated with a metal spatula on a copper bar having a diameter of 10 mm and a thickness of 5 mm using a stainless steel mask having a diameter of 4 mm and a thickness of 150 μm. Thereafter, a copper bar having a diameter of 3 mm and a thickness of 2 mm was mounted on the coated surface, and bonding was performed in a nitrogen atmosphere at 200 ° C. under no pressure condition. Firing is carried out at 43 ° C./min, held at the respective temperatures for 10 minutes, and then naturally cooled, whereby a copper bar joined body (Example 1 (the aqueous dispersion used is (a1)), Example 2 (the aqueous dispersion used was (a2)), Example 3 (the aqueous dispersion used was (a3)), and Example 4 (the aqueous dispersion used was (a4))) were obtained.

Test example 2
Using the water dispersion (a3), a copper bar joined body (in order, Example 5 and Example 6) was obtained in the same manner as in Test Example 1 except that joining was performed at 300 ° C. and 250 ° C., respectively. It was.

Test example 3
The same procedure as in Test Example 1 was conducted except that diethylene glycol and polyethylene glycol having a molecular weight of 200 to 400 (PEG200, PEG300, PEG400) were added to and mixed with the copper nanoparticle composite dry powder of the aqueous dispersion (a3) instead of ethylene glycol. A copper nanoparticle paste was obtained.
Using the copper nanoparticle paste, bonding was performed in the same manner as in Test Example 1 except that the bonding temperature was set to 350 ° C., thereby obtaining a copper bar joined body (in order of Example 7 to Example 10). It was.

Test example 4
The same procedure as in Test Example 1 was conducted except that N-methyl-2-pyrrolidone and propylene glycol diacetate were added and mixed in place of ethylene glycol to the copper nanoparticle composite dry powder of the aqueous dispersion (a3). A copper nanoparticle paste was obtained in the same manner as in Test Example 1 except that terpineol and dimethylformamide were added and mixed as a comparative example instead of ethylene glycol to the copper nanoparticle composite dry powder of the aqueous dispersion (a3). .
By using the copper nanoparticle paste, bonding was performed in the same manner as in Example 1 except that the bonding temperature was set to 200 ° C., so that the copper bar joined bodies (in order of Example 11, Example 12, and Comparative Example 1). Comparative Example 2) was obtained.

Test Example 5
Paste adjustment was performed using the same method as in Test Example 1 except that the aqueous dispersion (b) was used instead of the aqueous dispersion (a3) to obtain a silver nanoparticle paste.
Next, bonding was performed at 350 ° C., 300 ° C., 250 ° C., and 200 ° C. in the same manner as in Test Example 1 except that the silver nanoparticle paste (b) was used instead of the copper nanoparticle paste (a). Copper rod joined bodies (Examples 13 to 16) were obtained.

Evaluation 1
A shear strength test was carried out using the copper bar joined body of Examples 1 to 3 (Examples 1 to 3). The results are shown in Table 1.

Evaluation 2
A shear strength test was performed using the copper bar joined body of Examples 2 to 6 (Examples 5 to 6). The results are shown in Table 2.

As a result of the test, a high shear strength exceeding 20 MPa was exhibited under all temperature conditions.

Evaluation 3
A shear strength test was performed using the copper bar joined body of Example 3 (Examples 7 to 10). The results are shown in Table 3.

As is clear from the test results, not only ethylene glycol but also diethylene glycol and polyethylene glycol having a molecular weight of 200 were used as the solvent, and a high shear strength of 20 MPa or more was obtained at a bonding temperature of 200 ° C. On the other hand, when polyethylene glycols having molecular weights of 300 and 400 were used, the shear strength of 20 MPa or more was not exhibited, but practically sufficient shear strength of 15 MPa or more was exhibited.

Evaluation 4
A shear strength test was conducted using the copper bar joined body of Example 4 (Example 11, Example 12, Comparative Examples 1 and 2). The results are shown in Table 4.

A shear strength test was carried out using the copper bar joined body of Example 5 (Example 13 to Example 16). The results are shown in Table 5.

After joining, the joining material of the present invention utilizes the fact that the joining part has a melting point close to that of bulk copper and heat dissipation, so that mounting of semiconductor chips, joining in LED lighting manufacturing processes, joining in power device assembly, etc. In particular, it can be suitably used for assembling devices that are exposed to high temperatures and devices that require reliability at high temperatures. In addition, since the joint does not remelt even when heating is repeated, secondary and tertiary mounting can be performed without restriction of the reflow temperature, which can contribute to the expansion of the mounting procedure.

Claims

Metal nanoparticles (B) in which a polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms is combined, an alcohol solvent having a boiling point of 150 ° C. or higher, an ether solvent having a boiling point of 150 ° C. or higher, and an ester solvent having a boiling point of 150 ° C. or higher. And at least one solvent (C) selected from the group consisting of lactam structure-containing solvents having a boiling point of 150 ° C. or higher.
The polyethylene glycol having 8 to 200 carbon atoms and the contained organic compound (A) are represented by the compound represented by the following general formula (1), the compound represented by the following general formula (2), and the following general formula (3). Or a (meth) acrylic polymer (polymer α) having a structure represented by the following general formula (4) at least at one end and having a polyethylene glycol chain (P) in the side chain, (Meth) acrylic polymer having a structure represented by the following general formula (4) at one end and a phosphate ester residue represented by —OP (O) (OH) 2 in the side chain ( The bonding material according to claim 1, which is a compound containing a polymer β).
W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —SX (1)
[W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —S—] d Y (2)
[W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —S—R a —] t Z (3)
[W in the formulas (1), (2) and (3) is a C 1 to C 8 alkyl group, n is an integer indicating the number of repetitions of 4 to 100, and X is C 2 to C 12 Alkyl group, allyl group, aryl group, arylalkyl group, —R 1 —OH, —R 1 —NHR 2 , or —R 1 — (COR 3 ) m (where R 1 is C 1 -C 4 saturation) R 2 is a hydrogen atom, a C 2 -C 4 acyl group, a C 2 -C 4 alkoxycarbonyl group, or a C 1 -C 4 alkyl group or C 1 -C 8 on the aromatic ring. A benzyloxycarbonyl group optionally having an alkoxy group as a substituent, R 3 is a hydroxy group, a C 1 -C 4 alkyl group or a C 1 -C 8 alkoxy group, and m is 1 to 3 is an integer of 3), and Y is carbon directly bonded to a sulfur atom. A is a divalent to tetravalent radical atom, a saturated hydrocarbon group having a saturated hydrocarbon group or a C 1 ~ C 4 of C 1 ~ C 4 is -O -, - S- or -NHR b - (R b Is a C 1 to C 4 saturated hydrocarbon group), d is an integer of 2 to 4, and R a is a C 2 to C 5 alkylcarbonyloxy group. Z is a divalent to hexavalent group in which a carbon atom is directly bonded to a sulfur atom, and a C 2 to C 6 saturated hydrocarbon group or a C 2 to C 6 saturated hydrocarbon group is —O— , —S— or —NHR c — (R c is a saturated hydrocarbon group of C 1 to C 4 ), or isocyanuric acid —N, N ′, N ″ -triethylene And t is an integer of 2 to 6.]
RS (4)
[In the general formula (4), R represents a linear or branched alkyl group having 1 to 18 carbon atoms, a hydroxyl group, a linear alkoxy group having 1 to 18 carbon atoms, or a C 1 to 18 carbon atom. A branched alkoxy group, an aralkyloxy group, a substituted phenyloxy group, a linear alkylcarbonyloxy group having 1 to 18 carbon atoms, a branched alkylcarbonyloxy group having 1 to 18 carbon atoms, a carboxy group, a salt of a carboxy group, Straight chain alkoxycarbonyl group having 1 to 18 carbon atoms, branched alkoxycarbonyl group having 1 to 18 carbon atoms, phosphoric acid group, straight chain alkylphosphoric acid group having 1 to 6 carbon atoms, and 1 to 6 carbon atoms Selected from the group consisting of branched alkyl phosphate groups, sulfonic acid groups, linear alkyl sulfonic acid groups having 1 to 6 carbon atoms, and branched alkyl sulfonic acid groups having 1 to 6 carbon atoms. Even without a linear or branched alkyl group having 1 to 8 carbon atoms having a single functional group. ]
The polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms is represented by the compound represented by the following general formula (1), the compound represented by the following general formula (2), or the following general formula (3). The bonding material according to claim 1, which is a compound.
W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —SX (1)
[W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —S—] d Y (2)
[W— (OCH 2 CH 2 ) n —O—CH 2 —CH (OH) —CH 2 —S—R a —] t Z (3)
[W in the formulas (1), (2) and (3) is a C 1 to C 8 alkyl group, n is an integer indicating the number of repetitions of 4 to 100, and X is C 2 to C 12 Alkyl group, allyl group, aryl group, arylalkyl group, —R 1 —OH, —R 1 —NHR 2 , or —R 1 — (COR 3 ) m (where R 1 is C 1 -C 4 saturation) R 2 is a hydrogen atom, a C 2 -C 4 acyl group, a C 2 -C 4 alkoxycarbonyl group, or a C 1 -C 4 alkyl group or C 1 -C 8 on the aromatic ring. A benzyloxycarbonyl group optionally having an alkoxy group as a substituent, R 3 is a hydroxy group, a C 1 -C 4 alkyl group or a C 1 -C 8 alkoxy group, and m is 1 to 3 is an integer of 3), and Y is carbon directly bonded to a sulfur atom. A is a divalent to tetravalent radical atom, a saturated hydrocarbon group having a saturated hydrocarbon group or a C 1 ~ C 4 of C 1 ~ C 4 is -O -, - S- or -NHR b - (R b Is a C 1 to C 4 saturated hydrocarbon group), d is an integer of 2 to 4, and R a is a C 2 to C 5 alkylcarbonyloxy group. Z is a divalent to hexavalent group in which a carbon atom is directly bonded to a sulfur atom, and a C 2 to C 6 saturated hydrocarbon group or a C 2 to C 6 saturated hydrocarbon group is —O— , —S— or —NHR c — (R c is a saturated hydrocarbon group of C 1 to C 4 ), or isocyanuric acid —N, N ′, N ″ -triethylene And t is an integer of 2 to 6.]
The bonding material according to claim 1, wherein the solvent (C) is at least one solvent selected from the group consisting of an alcohol solvent having a boiling point of 150 ° C or higher and an ether solvent having a boiling point of 150 ° C or higher.
The bonding material according to claim 1, wherein the metal nanoparticles (B) are silver nanoparticles, copper nanoparticles, silver core copper shell nanoparticles, or copper core silver shell nanoparticles.
The bonding material according to claim 1, wherein the content of the polyethylene glycol-containing organic compound (A) having 8 to 200 carbon atoms in the metal nanoparticles is 2 to 15% by mass.
The bonding material according to any one of claims 1 to 6, wherein the objects to be bonded are metals or metal oxides.