JP7418731B2 - How to join metal parts - Google Patents

Description

The present invention relates to a method for joining metal members, a joined metal member, and a circuit board.

Conventionally, solder has been widely used when joining metal members together, such as joining electronic components and circuit boards, or joining circuits together. However, since the melting point of solder is relatively low, for example, when a module manufactured by solder mounting is further mounted on an electronic board, the solder may remelt during reflow at a temperature of about 260°C. Therefore, there was a problem in that the mounting position was shifted. Furthermore, the operating temperature of a power semiconductor module may reach a high temperature of 200° C. or higher. Therefore, power semiconductor modules obtained by solder mounting also have similar problems.

A conductive adhesive containing metallic silver and a binder, which is a resin component, can solve such problems caused by remelting of solder.
However, since the conductive adhesive contains a binder, it is unavoidable that the electrical resistivity of the joint made of the conductive adhesive becomes high (usually 100 μΩ・cm or more), and this joint There was also a problem that the heat resistance of the parts was insufficient.

On the other hand, a silver ink composition containing silver β-ketocarboxylate has been disclosed as a material that exhibits excellent conductivity when subjected to heat treatment (see Patent Document 1). This silver ink composition is a material that forms metallic silver from silver β-ketocarboxylate by heat treatment, and can form metallic silver with an extremely low volume resistivity of 10 μΩ·cm or less. Moreover, the formed metallic silver does not remelt even if it is exposed to high temperatures such as 200° C. or higher thereafter. Therefore, the above-mentioned problems caused by remelting of the solder can be solved.

Japanese Patent Application Publication No. 2014-193991

However, since the silver ink composition does not contain a binder, when metal members are bonded together using this silver ink composition, the metal members are bonded to each other via metallic silver. There was a problem in that it was difficult to increase the strength of the structure, that is, the bonding strength.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for joining metal members by which metal members can be joined with high strength via a conductive joint.

In order to solve the above-mentioned problems, the present invention provides a method for joining metal members to each other, in which a first member made of metal and a second member made of metal are bonded to the surface of one or both of them. heating the silver ink composition without solidifying at a temperature of 60° C. or higher to obtain a heated silver ink composition; bonding the first member and the second member with metallic silver by firing the heated material while pressing the first member and the second member together, the step of joining the first member and the second member with metallic silver; The composition contains a silver carboxylate having a group represented by the formula "-COOAg", an amine compound, and formic acid, and the silver ink composition forms metallic silver by firing. Provided is a method for joining metal members made of materials such as
In the method for joining metal members of the present invention, the silver ink composition before being heated without solidifying at a temperature of 60° C. or higher contains particles of metallic silver produced from the silver carboxylate, and Preferably, the crystallite size of the silver particles is less than 20 nm.
In the method for joining metal members of the present invention, the silver carboxylate is preferably silver β-ketocarboxylate represented by the following general formula (1).

（式中、Ｒは１個以上の水素原子が置換基で置換されていてもよい炭素数１～２０の脂肪族炭化水素基若しくはフェニル基、水酸基、アミノ基、又は一般式「Ｒ^１－ＣＹ^１ _２－」、「ＣＹ^１ _３－」、「Ｒ^１－ＣＨＹ^１－」、「Ｒ^２Ｏ－」、「Ｒ^５Ｒ^４Ｎ－」、「（Ｒ^３Ｏ）_２ＣＹ^１－」若しくは「Ｒ^６－Ｃ（＝Ｏ）－ＣＹ^１ _２－」で表される基であり；
Ｙ^１はそれぞれ独立にフッ素原子、塩素原子、臭素原子又は水素原子であり；Ｒ^１は炭素数１～１９の脂肪族炭化水素基又はフェニル基であり；Ｒ^２は炭素数１～２０の脂肪族炭化水素基であり；Ｒ^３は炭素数１～１６の脂肪族炭化水素基であり；Ｒ^４及びＲ^５はそれぞれ独立に炭素数１～１８の脂肪族炭化水素基であり；Ｒ^６は炭素数１～１９の脂肪族炭化水素基、水酸基又は式「ＡｇＯ－」で表される基であり；
Ｘ^１はそれぞれ独立に水素原子、炭素数１～２０の脂肪族炭化水素基、ハロゲン原子、１個以上の水素原子が置換基で置換されていてもよいフェニル基若しくはベンジル基、シアノ基、Ｎ－フタロイル－３－アミノプロピル基、２－エトキシビニル基、又は一般式「Ｒ^７Ｏ－」、「Ｒ^７Ｓ－」、「Ｒ^７－Ｃ（＝Ｏ）－」若しくは「Ｒ^７－Ｃ（＝Ｏ）－Ｏ－」で表される基であり；
Ｒ^７は、炭素数１～１０の脂肪族炭化水素基、チエニル基、又は１個以上の水素原子が置換基で置換されていてもよいフェニル基若しくはジフェニル基である。）

(In the formula, R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group of the general formula "R ¹ -CY ¹ ₂ -", "CY ¹ ₃ -", "R ¹ -CHY ¹ -", "R ² O-", "R ⁵ R ⁴ N-", "(R ³ O) ₂ CY ¹ -" or " A group represented by "R ⁶ -C(=O)-CY ¹ ₂ -";
Y ¹ is each independently a fluorine atom, chlorine atom, bromine atom, or hydrogen atom; R ¹ is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group; R ² is an aliphatic group having 1 to 20 carbon atoms; R ³ is an aliphatic hydrocarbon group having 1 to 16 carbon atoms; R ⁴ and R ⁵ are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms; R ⁶ is an aliphatic hydrocarbon group having 1 to 18 carbon atoms; An aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-";
X ¹ is each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group or benzyl group in which one or more hydrogen atoms may be substituted with a substituent, a cyano group, N -phthaloyl-3-aminopropyl group, 2-ethoxyvinyl group, or general formula "R ⁷ O-", "R ⁷ S-", "R ⁷ -C(=O)-" or "R ⁷ -C( is a group represented by “=O)-O-”;
R ⁷ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group, or a phenyl group or diphenyl group in which one or more hydrogen atoms may be substituted with a substituent. )

Further, the present invention provides a metal member joined body obtained by the metal member joining method, wherein the metal member joined body has a die shear strength of 15 MPa or more. .
Further, the present invention provides a circuit board in which the metal member assembly is provided on an organic substrate, and the metal member is a metal electrode.
The present invention also provides a metal member joined body, wherein the metal member joined body has a structure in which a first metal member and a second metal member are joined via metal silver. If one or both of the first member and the second member is made of copper, and the first member is made of copper, the metal member joined body is made of the first member and the second member. A layer containing silver as a main constituent element and a layer containing copper and oxygen as main constituent elements are provided in this order between the metallic silver and the metallic silver side, from the first member side to the metallic silver side, When the second member is made of copper, the metal member assembly is arranged such that silver is mainly applied between the second member and the metal silver from the second member side to the metal silver side. The present invention provides a metal member assembly comprising a layer containing copper as a constituent element and a layer containing copper and oxygen as main constituent elements in this order, and having a die shear strength of 15 MPa or more.

According to the present invention, there is provided a method for joining metal members that can join metal members with high strength via a conductive joint.

FIG. 1 is a cross-sectional view schematically illustrating an example of a method for joining metal members according to an embodiment of the present invention. FIG. 3 is a cross-sectional view schematically illustrating another example of a method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating still another example of the method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating still another example of the method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating still another example of the method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating another example of the joining process in the method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating still another example of the joining process in the method for joining metal members according to an embodiment of the present invention. FIG. 7 is a cross-sectional view schematically illustrating still another example of the joining process in the method for joining metal members according to an embodiment of the present invention. This is imaging data obtained when a cross section of the metal member assembly obtained in Example 1 was observed using a transmission electron microscope. This is imaging data obtained when a cross section of the metal member assembly obtained in Example 1 was observed by energy dispersive X-ray spectroscopy, when silver element was detected. This is imaging data obtained when a copper element was detected when a cross section of the metal member assembly obtained in Example 1 was observed by energy dispersive X-ray spectroscopy. This is imaging data obtained when the cross section of the metal member assembly obtained in Example 1 was observed by energy dispersive X-ray spectroscopy, when elemental oxygen was detected.

<<Method for joining metal members>>
A method for joining metal members according to an embodiment of the present invention is a method for joining metal members together, and includes a first metal member (herein simply abbreviated as "first member"). A silver ink composition attached to the surface of one or both of the metal second member (herein sometimes simply referred to as "second member"); a step of obtaining a heated product of the silver ink composition by heating the product at a temperature of 60° C. or higher without solidifying it (herein sometimes referred to as a “preheating step”); The first member and the second member are bonded to each other by pressing the first member and the second member together with a heated material of a silver ink composition interposed therebetween, and the heated material is fired, thereby bonding the first member and the second member to the metallic silver. (herein sometimes referred to as a "joining step"), wherein the silver ink composition includes a silver carboxylate having a group represented by the formula "-COOAg" ( In this specification, the silver ink composition is formed by blending a silver carboxylate (sometimes simply abbreviated as "silver carboxylate"), an amine compound, and formic acid, and the silver ink composition forms metallic silver by firing. material and joining method.

According to this embodiment, by performing the preheating step and the bonding step using the silver ink composition in the specific range described above, the first member and the second member have high bonding strength through the metallic silver. A joined metal member assembly is obtained.
The method for joining metal members according to this embodiment will be described in detail below.

<Preheating process>
In the preheating step, the silver ink composition adhering to the surface of either or both of the first member and the second member is heated at a temperature of 60° C. or higher without solidifying. By doing so, a heated product of the silver ink composition is obtained.
The silver ink composition used in this step is a material for forming metallic silver, and is a mixture of the silver carboxylate, an amine compound, and formic acid.

In this step, the silver ink composition before starting heating to obtain the heated object, that is, before heating without solidifying at a temperature of 60° C. or higher, typically contains the silver carboxylate composition. Contains particles of metallic silver produced from. This is because the formation of metallic silver from the silver carboxylate is promoted by the action of the formic acid.

In this embodiment, the crystallite diameter of the metallic silver particles is preferably less than 20 nm, more preferably 19 nm or less, and even more preferably 17 nm or less. When the crystallite diameter is less than (or less than) the upper limit value, a metal member joined body with higher bonding strength can be obtained.

The lower limit of the crystallite diameter of the metallic silver particles is not particularly limited. For example, from the viewpoint of easier preparation of a silver ink composition containing such metallic silver particles, the crystallite diameter is preferably 3 nm or more.

The crystallite diameter of the metallic silver particles can be adjusted as appropriate within a range set by any combination of any of the above upper and lower limits.
For example, in one embodiment, the crystallite size of the metallic silver particles may be 3 nm or more and less than 20 nm, 3 to 19 nm, and 3 to 17 nm. However, these are examples of the crystallite diameter of the metallic silver particles.

The crystallite diameter of metallic silver particles is determined by a known method. For example, when metallic silver particles are subjected to X-ray diffraction measurement, the peak of the crystal plane with the highest intensity in the obtained X-ray diffraction profile is determined using Scherrer's formula "D=kλ/βcosθ (wherein, D is the crystallite diameter (nm); k is a constant (0.9 is used here); λ is the wavelength of X-rays (CuKα ray) 0.154 nm; β is the peak half-width (rad) ; θ is 1/2 of the measurement angle.)", the crystallite diameter can be calculated.

The first member is made of metal, and the metal constituting it may be either a single metal or an alloy.
Preferred metals include, for example, copper, silver, gold, palladium, nickel, and alloys containing one or more selected from the group consisting of copper, silver, gold, palladium, and nickel. . Among these, the metal is more preferably copper, silver, gold, palladium or nickel, and even more preferably copper or silver.

In the preheating step, a metal member further provided with a metal layer on its surface may be used as the member including the first member. The metal layer can be formed on the surface of the metal member by, for example, a known method such as vapor deposition or plating.

In a metal member having such a metal layer on its surface, the first member is the part to which a silver ink composition for forming a conductive joint, which will be described later, is attached. For example, when the silver ink composition is applied only to the metal layer, the metal layer becomes the first member. When the silver ink composition is applied to both the metal member and the metal layer, both the metal member and the metal layer become the first member. When the silver ink composition is applied only to a metal member, the metal member becomes the first member.

A preferable example of a metal member having such a metal layer on its surface is a copper member having a silver layer on its surface, but this is just one example.

In the preheating step, a composite of a metal member and a non-metal member may be used as the member including the first member.
Examples of the nonmetallic member include a semiconductor wafer, a semiconductor chip, an organic insulating base material, an inorganic insulating base material, an organic/inorganic composite insulating base material, and any of these may be known.

Examples of the semiconductor wafer or semiconductor chip include a wafer or chip made of a semiconductor such as silicon, silicon carbide, or gallium nitride.
Examples of the organic insulating base material include a polytetrafluoroethylene (PTFE) base material, a polyimide base material, a liquid crystal polymer base material, a cycloolefin polymer base material, and the like.
Examples of the inorganic insulating base material include ceramic base materials.
The organic/inorganic composite insulating base material is a base material whose constituent materials are both an organic material and an inorganic material, and examples thereof include a glass epoxy resin base material.

Regardless of the type of non-metallic member, the composite may be formed by forming a metal member at a desired location of the non-metallic member by vapor deposition, plating, sputtering, printing, etc., or by brazing. Alternatively, it can be produced by joining metal members by bonding with an adhesive or the like.

Up to this point, we have mainly explained metal members provided on semiconductor wafers, semiconductor chips, organic insulating base materials, inorganic insulating base materials, organic/inorganic composite insulating base materials, etc. For example, a metal plate (for example, a heat sink) that is not provided in these is also suitable.

The shape of the first member is not particularly limited, and examples thereof include a sheet, a plate, a prism, a pyramid, a cylinder, a cone, a sphere, a long sphere, and a rod. , prismatic, pyramidal, cylindrical, conical, spherical, spheroidal, and rod-like), and may be a combination or fusion of two or more types selected from the group consisting of .

The size of the first member is not particularly limited.

The shape and size of the first member can be appropriately selected depending on the use of the first member.
For example, when the first member is plate-shaped or rod-shaped, the length of one side of the joint surface (first surface described later) of the first member is 0.01 to 30 mm, 0.02 to 24 mm, and The thickness of the first member may be any of 0.03 to 18 mm, and the thickness of the first member may be any of 0.01 to 5 mm, 0.02 to 3 mm, and 0.03 to 1.5 mm. However, these are examples of the shape and size of the first member. The first member having these shapes and sizes is suitable, for example, as an electrode forming a circuit.
If the shape of the first member is neither plate-like nor rod-like, for example, the first member may be shaped so that the area of the joint surface is equal to the area of the joint surface calculated from the length of one side described above. The size of one member can be adjusted.

The second member is also made of metal.
Examples of the metal constituting the second member include the same metals as the metal constituting the first member described above.
Examples of the shape of the second member include those similar to the shape of the first member.
The size of the second member may be similar to the size of the first member.

Similarly to the first member, the second member can also be used as a member containing the second member. The member including the second member can be used in the same manner as the member including the first member described above.

The first member and the second member may be the same or different.
For example, the first member and the second member to be joined in the joining process described below may be the same or different in terms of material, shape, and size.

In this embodiment, preferable first and second members include, for example, electrodes that constitute a circuit.

In the preheating step, one or both of the first member and the second member is used with a silver ink composition attached to the surface thereof. That is, in the preheating step, (A1) a combination of a first member to which the silver ink composition is attached to the surface and a second member to which the silver ink composition is not attached to the surface (hereinafter referred to as may be referred to as "combination (A1)"), (A2) a first member to which the silver ink composition is not attached to the surface, and a second member to which the silver ink composition is attached to the surface; (In this specification, the combination may be referred to as "combination (A2)"), or (A3) a first member having a silver ink composition attached to its surface, and a first member having a silver ink composition attached to its surface. A combination (sometimes referred to as "combination (A3)" in this specification) of the attached second member is used.

When using combination (A3), the silver ink composition adhering to the surface of the first member and the silver ink composition adhering to the surface of the second member may be the same as each other. However, they may be different from each other.

The silver ink composition can be attached to the surface of the first member or the second member by a known method such as a printing method or a coating method.

Examples of the printing method include a screen printing method, a flexo printing method, an offset printing method, a dip printing method, an inkjet printing method, a dispenser printing method, a jet dispenser printing method, a gravure printing method, a gravure offset printing method, Examples include pad printing method.

The coating method includes, for example, a method using various coaters such as a spin coater, an air knife coater, a curtain coater, a die coater, a blade coater, a roll coater, a gate roll coater, a bar coater, a rod coater, and a gravure coater; Methods to be used include a method using a coating device such as a slot die, a spray method, and the like.

It is preferable to perform a cleaning process to remove impurities before depositing the silver ink composition on the surface of the first member or the second member to which the silver ink composition is deposited. By doing so, a metal member joined body with higher joining strength can be obtained.

The cleaning treatment can be performed by a known method, and may be, for example, a chemical treatment of the surface using a drug or a physical treatment using a surface treatment.
Examples of the chemicals include acids such as nitric acid, phosphoric acid, sulfuric acid, and hydrochloric acid; organic solvents such as acetone. Chemical treatment with acids is useful for general impurity removal. When an acid is used, it is preferable to further wash the acid-treated surface of the first member or the second member with water. Chemical treatment with an organic solvent is useful when removing highly fat-soluble impurities.
Examples of the surface treatment include polishing using an abrasive material such as a file.

The reason why a silver ink composition containing the silver carboxylate, an amine compound, and formic acid is used in the preheating step is because it has the following advantages.
That is, the silver ink composition is advantageous in increasing the amount of silver carboxylate among all silver ink compositions containing silver carboxylate. In that case, the silver ink composition has a large content of components derived from the silver carboxylate (for example, silver carboxylate, metallic silver generated from silver carboxylate, etc.) per unit amount of the silver ink composition, and therefore More heated objects can be formed on the surfaces of the two members in one execution. Further, since the silver ink composition has a high viscosity, it is easy to increase the amount of the silver ink composition adhered to the surfaces of the first member and the second member. Therefore, also in this respect, the silver ink composition can form more of the heated material on the surfaces of the first member and the second member in one application.
As described above, the silver ink composition is advantageous in that it is possible to easily increase the amount of the heated material formed on the surfaces of the first member and the second member.

Further, the first member and the second member to which the silver ink composition is attached are made of metal, and metal oxides are likely to be generated on the surfaces thereof by oxidation reaction. When such metal oxides are produced in a film or non-film form, not only the resistivity of the metal member assembly increases, but also the bonding strength of the metal member assembly decreases.
On the other hand, the formic acid contained in the silver ink composition has a reducing effect, and the silver ink composition itself has good reducing properties. Therefore, the silver ink composition is advantageous in that it can reduce the amount of metal oxide on the surfaces of the first member and the second member.

In addition, the reducing action of compounds having a formyl group is more activated under basic conditions. The silver ink composition is basic due to the effect of the blended amine compound, and the reducing action of formic acid having a formyl group is more activated. Therefore, the silver ink composition is advantageous in that the effect of using the above-mentioned formic acid is higher.

The amount of the silver ink composition deposited on the surface of the first member or the second member is not particularly limited, and may be appropriately set in consideration of the intended thickness of the conductive joint.

The thickness of the heated silver ink composition on the surface of the first member or the second member is preferably 100 μm or more, more preferably 200 μm or more, and even more preferably 250 μm or more. When the thickness of the heated object is equal to or greater than the lower limit, a metal member assembly with higher bonding strength can be obtained.

The upper limit of the thickness of the heated material of the silver ink composition on the surface of the first member or the second member is not particularly limited. In order to avoid excessive thickness, the thickness of the heated object is preferably 1000 μm or less.

The thickness of the heated object can be adjusted as appropriate within a range set by arbitrarily combining any of the above lower limit values and upper limit values.
For example, in one embodiment, the thickness of the heated object may be any one of 100 to 1000 μm, 200 to 1000 μm, and 250 to 1000 μm. However, these are examples of the thickness of the heated object.

In the preheating step, the heated material of the silver ink composition may be one layer or two or more layers, and if there are two or more layers, the combination and ratio thereof may be determined depending on the purpose. Can be adjusted arbitrarily.
When the heated material of the silver ink composition has two or more layers, the total thickness of each layer is preferably set to the above-mentioned preferred thickness of the heated material.

For example, depending on the type of silver ink composition and the method of depositing the silver ink composition, the amount of deposited silver ink composition may not reach the desired amount even if the operation of depositing the silver ink composition is performed only once. There are some things that should not be done. In that case, it is necessary to repeat the operation of depositing the silver ink composition two or more times. In this case, the heated object finally obtained may have one layer, but may also have two or more layers.
Furthermore, for example, depending on the purpose, it may be required to form a conductive junction composed of two or more layers having different compositions. In that case, it is necessary to perform the operation of depositing different types of silver ink compositions a total of two or more times. In this case, the heated object finally obtained has two or more layers.
In this embodiment, the heated object having two or more layers can be handled in the same way as the heated object having one layer, regardless of its type.

In the above method, the operation of depositing the silver ink composition on either the first member or the second member is repeated two or more times, but as explained earlier, the silver ink composition is deposited on the surface. Even when using a combination of a first member with a silver ink composition and a second member with a silver ink composition attached to the surface (i.e., the above combination (A3)), the same two A conductive joint made of the above layers can be formed.

In the preheating step, both the first member to which the silver ink composition has adhered and the second member to which the silver ink composition has adhered are heated directly over areas to which the silver ink composition has not adhered. Heating is preferred. By doing so, the effect of suppressing unintended deterioration of the silver ink composition becomes higher.

In the preheating step, the silver ink composition is heated using known methods such as heating with an electric furnace, heating with a thermosensitive thermal head, heating with far-infrared irradiation, heating with spraying of high-temperature gas, heating with high-frequency irradiation, and dielectric heating. Depending on the method, it can be heated.

In the preheating step, in any of the combinations (A1) to (A3), the silver ink composition adhering to the surface of the first member and the silver ink adhering to the surface of the second member The composition is heated to a temperature of 60°C or higher.
However, at this time, the silver ink composition that is heated is not solidified.
In this step, the heated silver ink composition obtained without solidification maintains fluidity.

In the preheating step, the temperature at the start of heating the silver ink composition may be, for example, room temperature.
In this specification, "normal temperature" means a temperature that is not particularly cooled or heated, that is, a normal temperature, and includes, for example, a temperature of 15 to 25°C.

The heating temperature of the silver ink composition in the preheating step may be, for example, 70°C or higher, 80°C or higher, or 90°C or higher.

The upper limit of the heating temperature of the silver ink composition in the preheating step is not particularly limited. For example, the heating temperature is preferably 120° C. or lower in terms of easily avoiding solidification of the silver ink composition.

The heating temperature of the silver ink composition in the preheating step can be adjusted as appropriate within a range set by arbitrarily combining any of the above lower limit values and upper limit values. For example, in one embodiment, the heating temperature may be any one of 60 to 120°C, 70 to 120°C, 80 to 120°C, and 90 to 120°C. However, these are examples of the heating temperatures.

In the preheating step, the temperature increase rate during heating of the silver ink composition is not particularly limited, but is preferably 5 to 50°C/min, more preferably 5 to 30°C/min, More preferably, the rate is ~16°C/min.

In the preheating step, the heating time of the silver ink composition is not particularly limited, but is preferably 1 minute to 12 hours, more preferably 2 minutes to 6 hours, and 4 minutes to 1 hour. It is even more preferable.

The preheating step may be performed under normal pressure, reduced pressure, or increased pressure.
Further, the preheating step may be performed, for example, in an air atmosphere or an inert gas atmosphere. Examples of the inert gas include nitrogen gas, argon gas, helium gas, and the like.
When the preheating step is performed under conditions that can suppress the oxidation reaction of the first member, the second member, the silver ink composition, and the heated material, it is preferably performed under reduced pressure or an inert gas atmosphere. For example, the preheating step is preferably carried out under an inert gas atmosphere in terms of a high oxidation reaction suppression effect, and is preferably carried out under reduced pressure in terms of low cost.

In the preheating step, the temperature of the silver ink composition may be consistently increased (in other words, neither constant nor decreased) until the end of the preheating step. , you may provide a period of time to keep it constant, or you may provide a period of time to decrease it.
In particular, in order to obtain a metal member assembly with higher bonding strength, the temperature of the silver ink composition must be raised or kept constant from the start to the end of the preheating step. (In other words, it should not be lowered at all). For example, after the temperature of the silver ink composition is consistently increased from the beginning of the preheating step, the highest temperature reached is maintained until the end of the preheating step. , may be held for a certain period of time. In that case, the time for maintaining the temperature of the silver ink composition for a certain period of time is preferably 0.5 to 10 minutes, more preferably 0.5 to 6 minutes, and 0.5 to 3 minutes. It is even more preferable.

In the preheating step, foaming is typically observed in the silver ink composition until the heated silver ink composition is obtained. This is because the reactions of the ingredients in the silver ink composition progress, gas is generated, and this gas escapes. Typically, by the end of the process, this bubbling has disappeared and gas evolution has substantially or completely ceased.
Since the silver ink composition foams in this manner, the mass of the heated silver ink composition at the end of this step is smaller than the mass of the silver ink composition at the beginning of this step. That is, in this step, a decrease in the mass of the silver ink composition is observed.

In the present embodiment, (B1) after the preheating step, the first member and the second member may be brought into contact with each other via the heated object (the first member, the heated object, and the second member are laminated). (herein, sometimes referred to as "preheating method (B1)"), and (B2) bringing the first member and the second member into contact via the silver ink composition, and then ( After stacking the first member, the silver ink composition, and the second member), a preheating step may be performed (herein sometimes referred to as "preheating method (B2)"), B3) Even if the first member and the second member are brought into contact with each other through the silver ink composition that is being heated during the preheating step (the first member, the silver ink composition that is being heated, and the second member are (In this specification, it may be referred to as "preheating method (B3)"), and the timing of stacking (stacking) the first member and the second member can be arbitrarily selected.

Among these, it is preferable to adopt the preheating method (B1) or (B3), and it is more preferable to adopt the preheating method (B1) in terms of obtaining a metal member joined body with higher bonding strength. .

In the preheating step, when combination (A1) is selected, the silver ink composition before heating, the silver ink composition during heating, or the silver ink composition after heating adheres to the surface of the first member. (that is, the heated object) is brought into contact with the second member.
In the preheating step, when combination (A2) is selected, the silver ink composition before heating, the silver ink composition during heating, or the silver ink composition after heating adheres to the surface of the second member. (that is, the heated object) is brought into contact with the first member.
In the preheating step, when combination (A3) is selected, the silver ink composition before heating, the silver ink composition during heating, or the silver ink composition after heating adheres to the surface of the first member. (i.e., the heated object) and the silver ink composition before heating, the silver ink composition during heating, or the silver ink composition after heating (i.e., the heated object) attached to the surface of the second member. and bring them into contact.
In either case, the silver ink composition adhering to the first member or the second member forms a conductive joint that joins the first member and the second member in a later step.

In this embodiment, by forming the heating object in the preheating step, the bonding strength of the conductive bonding portion is significantly increased. The reason for this excellent effect is not clear, but by heating the silver ink composition without solidifying it, the heated material obtained has fluidity, unlike when it is solidified. This is presumably because the adhesion between the heating object and the first member and the adhesion between the heating object and the second member are improved. Further, as described above, typically, foaming is observed in the silver ink composition until the heated material is obtained, but this foaming disappears by the end of this process. Furthermore, since the heated object is not solidified, roughness on the surface of the heated object caused by bubbling is reduced, and the contact area between the heated object and the first member and the contact area between the heated object and the second member are reduced. It is speculated that this is due to an increase in the contact area.

The heated material obtained in the preheating step typically does not have the luster characteristic of metallic silver, and is, for example, dark green in color. Due to these external characteristics, the heating material does not primarily consist of high-purity metallic silver.

<Joining process>
After the preheating step, in the bonding step, the heated material of the silver ink composition is interposed and the heated material is baked while pressing the first member and the second member. The first member and the second member are joined using metallic silver.
The silver ink composition is a material for forming metallic silver, and in this step, it is solidified by firing to finally form metallic silver and join the first member and the second member.

In the joining process, a pressure in a direction from the first member toward the second member and a pressure applied to the composite in which the first member, the heated object, and the second member are stacked in this order, and the second member The first member and the second member can be crimped together by applying one or both of the following pressures in the direction toward the first member.

When applying pressure to the composite in a direction from the first member toward the second member, it is preferable to apply the pressure in this direction with the second member fixed.
When applying pressure to the composite in a direction from the second member toward the first member, it is preferable to apply the pressure in this direction with the first member fixed.

The above-mentioned pressure in two directions may be applied by a known method.
For example, when applying pressure in only one of the two directions described above, fix the composite on a horizontal surface with the surface of either the first member or the second member facing downward in the vertical direction, By placing the other surfaces of the first member and the second member vertically upward and placing a weight thereon, pressure can be applied to the composite from only one direction.
Here, a case has been described in which pressure is applied by placing a weight on either the first member or the second member, but pressure may be applied by other pressing means.
In addition, here, a case has been described in which the composite is arranged with the surfaces of the first member and the second member facing in the vertical direction. , the composite may be placed.

In the joining process, the pressure (herein sometimes abbreviated as "crimping pressure") used to press the first member and the second member together using the heated object is not particularly limited. , preferably 0.2 MPa or more, more preferably 0.4 MPa or more, even more preferably 0.6 MPa or more. When the crimp pressure is equal to or higher than the lower limit value, a metal member assembly with higher bonding strength can be obtained.

In the joining process, the upper limit of the pressure bonding pressure is not particularly limited. In terms of making crimping easier, the crimping pressure is preferably 3 MPa or less.

In the bonding step, the compression pressure can be adjusted as appropriate within a range set by arbitrarily combining any of the above lower limit values and upper limit values.
For example, in one embodiment, the compression pressure may be any one of 0.2 to 3 MPa, 0.4 to 3 MPa, and 0.6 to 3 MPa. However, these are examples of the compression pressure.

In the bonding process, the crimping pressure may or may not be constant from the start of crimping to the end of crimping.
In the case where the crimp pressure is not constant, the crimp pressure may be increased consistently (in other words, it is not necessary to keep it unchanged or decrease it), or set a time period during which it is not changed. Alternatively, a period of time may be provided for the reduction. Among these, it is preferable that the compression pressure be always increased or not changed (in other words, not decreased at all).

In the bonding step, metallic silver is formed by firing the heated material.
Firing the heated object in the bonding step can be performed by further heating the heated object. The heating at this time can be performed in the same manner as the heating performed on the silver ink composition in the preheating step.

In the bonding step, the temperature at the start of firing of the heated object may be lower than the temperature at the end of the preheating step, such as room temperature, but may be higher than the temperature at the end of the preheating step. preferable.

The firing temperature of the heated object in the joining step may be, for example, any one of 170°C or higher, 220°C or higher, or 270°C or higher.

The upper limit of the firing temperature of the heated object in the joining process is not particularly limited. For example, in terms of shortening the process time and avoiding excessively high temperatures, the firing temperature is preferably 350°C or lower, more preferably 320°C or lower. The reason why the firing temperature can be kept relatively low is that the silver ink composition uses ingredients within a relatively limited range.

The firing temperature of the heated object in the joining process can be adjusted as appropriate within a range set by any combination of any of the above lower limit values and any of the upper limit values.
For example, in one embodiment, the firing temperature may be any one of 170 to 350°C, 220 to 350°C, and 270 to 350°C.
In one embodiment, the firing temperature may be any one of 170 to 320°C, 220 to 320°C, and 270 to 320°C.
However, these are examples of the firing temperatures.

In the bonding step, the temperature increase rate during firing of the heated object is not particularly limited, but is preferably 5 to 50°C/min, more preferably 5 to 45°C/min, and 5 to 40°C. It is more preferable that it is /min.

In the joining step, the firing time of the heated object is not particularly limited, but is preferably 1 minute to 24 hours, more preferably 5 minutes to 12 hours, and even more preferably 10 minutes to 2 hours. preferable.

In the bonding step, the firing temperature of the heated material may be consistently increased until the end of the bonding step (in other words, it is not necessary to keep it constant or decrease it), You may provide a period of time to keep it constant or a period of time to decrease it.
In particular, it is preferable that the firing temperature of the heated material is always raised or kept constant (in other words, not lowered at all) from the start to the end of the joining process. After the firing temperature of the heated object is consistently raised from the start, the maximum temperature reached there may be maintained for a certain period of time until the end of the bonding process. In that case, the time for maintaining the firing temperature of the heated material for a certain period of time is preferably 5 to 60 minutes, more preferably 10 to 50 minutes, and even more preferably 15 to 40 minutes.

The joining step may be performed under normal pressure, reduced pressure, or increased pressure.
Further, the bonding step may be performed, for example, either in the air atmosphere or in an inert gas atmosphere. Examples of the inert gas include nitrogen gas, argon gas, helium gas, and the like.
When the bonding step is performed under conditions that can suppress the oxidation reaction of the first member, the second member, and the fired product (i.e., metal silver), it is preferably performed under reduced pressure or an inert gas atmosphere. For example, the bonding step is preferably carried out under an inert gas atmosphere in terms of a high oxidation reaction suppression effect, and is preferably carried out under reduced pressure in terms of low cost.

The thickness of the conductive joint (in other words, metallic silver) formed by firing the heated object is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 25 μm or more. . When the thickness of the conductive joint is equal to or greater than the lower limit, the joint strength of the metal member assembly becomes higher. Furthermore, conductive junctions with a thickness of 20 μm or more are easier to form.
Note that in this specification, "thickness of the conductive joint" means "thickness of the conductive joint in the joining direction of the first member and the second member".

The upper limit of the thickness of the conductive joint is not particularly limited. In order to avoid excessive thickness, the thickness of the conductive joint is preferably 100 μm or less.

The thickness of the conductive joint can be adjusted as appropriate within a range set by arbitrarily combining any of the above lower limit values and upper limit values.
For example, in one embodiment, the thickness of the conductive joint may be any one of 10 to 100 μm, 20 to 100 μm, and 25 to 100 μm. However, these are examples of the thickness of the conductive joint.

The thickness of the conductive joint is determined, for example, by the thickness of the heated object before firing.
Typically, the thickness of the conductive joint is preferably 4 to 16%, more preferably 6 to 14%, and even more preferably 8 to 12% of the thickness of the heated object before firing. It is possible to do so. However, these are examples of the relationship between the thickness of the conductive joint and the thickness of the heated object before firing.

In the present embodiment, (C1) the firing of the heated material may be started after the compression bonding between the first member and the second member is started (in this specification, "pressure bonding firing method (C1) ), and (C2) after starting the firing of the heated object, pressing the first member and the second member may be started (herein, referred to as "pressing firing method"). (C2)") and (C3) crimping the first member and the second member and firing the heated material may be started at the same time (herein, "crimping") may be started at the same time. The timing of the above-mentioned pressing and firing can be arbitrarily selected.

Among these, it is preferable to adopt the compression firing method (C1) or (C3), and it is more preferable to employ the compression firing method (C1) in terms of obtaining a metal member joined body with higher bonding strength. .

In the bonding step, the bonding strength of the conductive bonded portion is significantly increased by crimping the first member and the second member with the heating object interposed therebetween. It can be said that it is completely unexpected that the joint strength increases in this way in a conductive joint that does not contain a resin component such as a binder, unlike in the past. The reason for this excellent effect is not clear, but the laminated structure of the first member, the heated object during firing, and the second member is pressed together in the thickness direction. It is speculated that this is because the volume of the voids in the heated object during firing decreases and the density increases, and as a result, the strength of the fired object (conductive joint) improves.

The strength of the conductive joint of the metal member assembly obtained in this embodiment can be evaluated by, for example, a measured value of die shear strength.
Die shear strength can be measured in accordance with JIS C62137-1-2:2010 (lateral push shear strength test, IEC 62137-1-2:2007). That is, in the metal member assembly, one of the first member and the second member joined by the conductive joint is fixed, and the first member, the conductive joint, and the second member are fixed to the other. A force is applied in a direction perpendicular to the lamination direction (in other words, in a direction parallel to the laminated planes), and the laminated structure of these (first member, conductive joint, and second member) is destroyed. The above-mentioned force applied when the die is applied is adopted as the die shear strength.

In this embodiment, the die shear strength of the metal member assembly is preferably 15 MPa or more, and may be, for example, any one of 22.5 MPa or more, 27.5 MPa or more, or 32.5 MPa or more.

In this embodiment, the upper limit of the die shear strength of the metal member assembly is not particularly limited. For example, in terms of ease of manufacturing the metal member assembly, the die shear strength is preferably 50 MPa or less.

The die shear strength can be adjusted as appropriate within a range set by arbitrarily combining any of the above lower limit values and upper limit values.
For example, in one embodiment, the die shear strength may be any one of 15 to 50 MPa, 22.5 to 50 MPa, 27.5 to 50 MPa, and 32.5 to 50 MPa. However, these are examples of the die shear strength.

<Other processes>
The method for joining metal members according to the present embodiment may include other steps that do not fall under either the preheating step or the joining step, as long as the effects of the present invention are not impaired. .
The other steps described above are not particularly limited and can be arbitrarily selected depending on the purpose.
The timing of performing the other steps can also be arbitrarily selected depending on the purpose, and may be, for example, before the preheating step, between the preheating step and the bonding step, or after the bonding step. .

<Example of joining method for metal members>
FIG. 1 is a sectional view schematically illustrating an example of a method for joining metal members according to an embodiment of the present invention.
Note that the figures used in the following explanation may show important parts enlarged for convenience in order to make the features of the present invention easier to understand, and the dimensional ratio of each component may be the same as the actual one. Not necessarily.

FIG. 1 shows a method for joining metal members (sometimes referred to as "joining method (1-1)" in this specification) when combination (A1) and preheating method (B1) are selected. FIG. 2 is a cross-sectional view for schematic explanation.
That is, in the preheating step of the bonding method (1-1), as shown in FIG. A combination of the second member 12 and the second member 12 to which is not attached is used. The silver ink composition 130 is attached to one surface (sometimes referred to as "first surface" in this specification) 11a of the first member 11.

In the preheating step of the bonding method (1-1), the silver ink composition 130 adhering to the first surface 11a of the first member 11 is heated at a temperature of 60° C. or higher in this way without solidifying it. By doing so, as shown in FIG. 1(b), a heated material 130' of the silver ink composition 130 is obtained.

Next, in the bonding step of the bonding method (1-1), as shown in FIG. The heated object 130' is fired while being compressed. At this time, the force applied to press the laminated structure of the first member 11, the heated object 130', and the second member 12 is one or both of the force _P1 and the force _P2 . be able to. At this time, a surface 12a of the second member 12 on the first member 11 side (in this specification, sometimes referred to as "first surface") comes into contact with the heated object 130'.

By performing the preheating step and the bonding step in this manner, the first member 11 and the second member 12 are bonded via the metal silver (in other words, a conductive bonding portion) 13, as shown in FIG. 1(d). A metal member assembly 1 is obtained.

FIG. 2 is a cross-sectional view for schematically explaining another example of the method for joining metal members according to an embodiment of the present invention.
In the figures after FIG. 2, the same components as those shown in the already explained figures are given the same reference numerals as in the already explained figures, and detailed explanation thereof will be omitted.

FIG. 2 shows a method for joining metal members (sometimes referred to as "joining method (2-1)" in this specification) when combination (A2) and preheating method (B1) are selected. FIG. 2 is a cross-sectional view for schematic explanation.
That is, in the preheating step of the bonding method (2-1), as shown in FIG. A combination of the second member 12 and the second member 12 to which is attached is used. The silver ink composition 130 is attached to the first surface 12a of the second member 12.

In the preheating step of the bonding method (2-1), the silver ink composition 130 adhering to the first surface 12a of the second member 12 is thus heated at a temperature of 60° C. or higher without solidifying. By doing so, a heated material 130' of the silver ink composition 130 is obtained as shown in FIG. 2(b).

Next, in the bonding step of the bonding method (2-1), as shown in FIG. The heated object 130' is fired while being compressed. At this time, the surface of the first member 11 on the second member 12 side, that is, the first surface 11a, comes into contact with the heated object 130'.
In this step, after forming the laminated structure of the first member 11, the heated object 130', and the second member 12, in the case of the joining method (1-1) described with reference to FIG. It can be done in the same way.

By performing the preheating step and the bonding step in this manner, the first member 11 and the second member 12 are bonded via the metal silver (in other words, a conductive bonding portion) 13, as shown in FIG. 2(d). A metal member assembly 1 is obtained.

FIG. 3 is a cross-sectional view schematically illustrating still another example of the method for joining metal members according to an embodiment of the present invention.
FIG. 3 shows a method for joining metal members (sometimes referred to as "joining method (3-1)" in this specification) when combination (A3) and preheating method (B1) are selected. FIG. 2 is a cross-sectional view for schematic explanation.
That is, in the preheating step of the bonding method (3-1), as shown in FIG. 130 is attached to the second member 12. The silver ink composition 130 is attached to both the first surface 11a of the first member 11 and the first surface 12a of the second member 12. These silver ink compositions 130, 130 may be the same or different.

In the preheating step of the joining method (3-1), in this way, the silver ink composition 130 attached to the first surface 11a of the first member 11 and the silver ink composition attached to the first surface 12a of the second member 12 are By heating both the silver ink compositions 130 and 130 without solidifying at a temperature of 60° C. or higher, as shown in FIG. get.

Next, in the bonding step of the bonding method (3-1), as shown in FIG. 3(c), the first member 11 and The heating objects 130', 130' are fired while being pressed together with the second member 12. At this time, the heated object 130' on the first surface 11a of the first member 11 and the heated object 130' on the first surface 12a of the second member 12 come into contact.
In this step, after forming the laminated structure of the first member 11, the two layers of the heating material 130', and the second member 12, the object to be crimped is this laminated structure. Except for this point, the bonding method can be performed in the same manner as the bonding method (1-1) described with reference to FIG.

By performing the preheating step and the bonding step in this way, the first member 11 and the second member 12 form two layers of metal silver (layer) 13, in other words, conductive bonding A metal member assembly 2 joined via the portion 23 is obtained.

Here, for convenience, the conductive joint portion 23 in the metal member assembly 2 is shown as having two layers. In the bonding method (3-1), the silver ink composition 130 initially attached to the first member 11 and the silver ink composition 130 initially attached to the second member 12 are of different types. In this case, the conductive joint 23 is composed of such two layers. On the other hand, if the silver ink composition 130 initially attached to the first member 11 and the silver ink composition 130 initially attached to the second member 12 are of the same type, this The conductive joint 23 may be composed of two layers, or may be a single-layer conductive joint (for example, a conductive joint similar to the conductive joint 13 shown in FIGS. 1 and 2). Sometimes it becomes.

Up to this point, we have explained the method for joining metal members when the preheating method (B1) is selected in the preheating process, but in the above manufacturing method, the preheating method (B2) or (B3) is selected. You can also.

FIG. 4 shows a method for joining metal members (sometimes referred to as "joining method (1-2)" in this specification) when combination (A1) and preheating method (B2) are selected. FIG. 2 is a cross-sectional view for schematic illustration.
That is, in the preheating step of bonding method (1-2), as in bonding method (1-1), as shown in FIG. 1(a), the silver ink composition 130 is attached to the surface. A combination of a first member 11 with a silver ink composition and a second member 12 with no silver ink composition attached to the surface is used.

In the preheating step of the bonding method (1-2), next, as shown in FIG. The first member 11 and the second member 12 are brought into contact. Then, after stacking the first member 11, silver ink composition 130, and second member 12 in this way, the silver ink composition 130 is heated at a temperature of 60° C. or higher without solidifying. As shown in c), a heated product 130' of the silver ink composition 130 is obtained. As a result, a laminated structure of the first member 11, the heated object 130', and the second member 12 is obtained in a state similar to that shown in FIG. 1(c).

Next, in the bonding step of the bonding method (1-2), as shown in FIG. Then, the heating object 130' is fired while the first member 11 and the second member 12 are pressed together.

By performing the preheating step and the bonding step in this manner, the first member 11 and the second member 12 are bonded via the metal silver (in other words, a conductive bonding portion) 13, as shown in FIG. 4(d). A metal member assembly 1 is obtained.

FIG. 5 shows a method for joining metal members (sometimes referred to as "joining method (1-3)" in this specification) when combination (A1) and preheating method (B3) are selected. FIG. 2 is a cross-sectional view for schematic illustration.
That is, in the preheating step of bonding method (1-3), as in bonding method (1-1), as shown in FIG. 5(a), the silver ink composition 130 is attached to the surface. A combination of a first member 11 with a silver ink composition and a second member 12 with no silver ink composition attached to the surface is used.

In the preheating step of the bonding method (1-3), in this way, the silver ink composition 130 adhering to the first surface 11a of the first member 11 is heated so as not to solidify at a temperature of 60° C. or higher. Then, as shown in FIG. 5(b), heating is started. Here, a reference numeral 1301 is given to the silver ink composition in the middle of heating before becoming the heated object 130'.

Next, in the preheating step of the bonding method (1-3), as shown in FIG. 5(c), during the main step, the first member 11 and the first member The two members 12 are brought into contact. The temperature of the silver ink composition 1301 during heating during contact in this manner may be lower than 60°C or higher than 60°C.

Next, in the preheating step of the bonding method (1-3), the heated silver ink composition 1301 adhering to the first member 11 and the second member 12 is further heated to a temperature of 60° C. or higher. By heating the silver ink composition 130 without solidifying it at high temperature, a heated material 130' of the silver ink composition 130 is obtained as shown in FIG. 5(d).

Next, in the bonding step of the bonding method (1-3), as shown in FIG. Then, the heating object 130' is fired while the first member 11 and the second member 12 are pressed together.

By performing the preheating step and the bonding step in this manner, the first member 11 and the second member 12 are bonded via the metal silver (in other words, a conductive bonding portion) 13, as shown in FIG. 5(f). A metal member assembly 1 is obtained.

Up to this point, we have explained the method for joining metal members when combination (A1) and preheating methods (B1) to (B3) are selected. B1), (B2) or (B3) can also be selected.

In the bonding method described above with reference to FIGS. 1 to 5, the timing of starting pressure bonding between the first member and the second member with the intervention of a heated silver ink composition in the bonding step and , and the timing of starting firing of the heated material are not specifically explained. In this embodiment, these sequential relationships can be arbitrarily selected as described above for the compression firing methods (C1) to (C3).

Hereinafter, the bonding method (1-1) explained with reference to FIG. 1 will be explained in more detail by taking as an example.
FIG. 6 shows a method for joining metal members (in this specification, "joining method (1)") when combination (A1), preheating method (B1), and compression firing method (C1) are selected. FIG. 2 is a cross-sectional view schematically illustrating the bonding process in the process (sometimes referred to as "-1-1)".

In the joining process of the joining method (1-1-1), as shown in FIG. 6(a), the first member 11, the heated object 130', A laminated structure of the second member 12 is obtained.
Next, as shown in FIG. 6(b), the crimping of this laminated structure is started.

Next, in the joining step of the joining method (1-1-1), firing of the heated object 130' is started, as shown in FIG. 6(c). Here, the heating object in the intermediate stage of firing (including the firing start stage) before becoming the conductive joint 13 is designated by the reference numeral 1301'.

By performing the bonding process in this way, as shown in FIG. 6(d), the first member 11 and the second member 12 are bonded via the conductive bonding portion 13, similar to that shown in FIG. 1(d). A joined metal member assembly 1 is obtained.

FIG. 7 shows a method for joining metal members (in this specification, "joining method (1)") when combination (A1), preheating method (B1), and compression firing method (C2) are selected. FIG. 2 is a cross-sectional view schematically illustrating a bonding process in the process (sometimes referred to as "-1-2)".

In the joining process of the joining method (1-1-2), as shown in FIG. 7(a), the first member 11, the heated object 130', A laminated structure of the second member 12 is obtained.
Next, as shown in FIG. 7(b), firing of the heating object 130' is started. Here again, the reference numeral 1301' is given to the heated object in the intermediate stage of firing (including the starting stage of firing) before becoming the conductive joint 13.

Next, in the joining step of the joining method (1-1-2), as shown in FIG. , the crimping of the laminated structure is started.

By performing the bonding process in this way, as shown in FIG. 7(d), the first member 11 and the second member 12 are bonded via the conductive bonding portion 13, similar to that shown in FIG. 1(d). A joined metal member assembly 1 is obtained.

FIG. 8 shows a method for joining metal members (in this specification, "joining method (1)") when combination (A1), preheating method (B1), and compression firing method (C3) are selected. FIG. 3 is a cross-sectional view schematically illustrating the bonding process in the process (sometimes referred to as "-1-3)".

In the joining process of the joining method (1-1-3), as shown in FIG. 8(a), the first member 11, the heated object 130', A laminated structure of the second member 12 is obtained.
Next, as shown in FIG. 8(b), firing of the heated object 130' and compression of the laminated structure are started simultaneously. Here, the force applied at the start of the compression bonding of the laminated structure is denoted by P ₁₁ and P ₂₁ , and the heated object at the start of firing is denoted by 1302'.

By performing the bonding process in this way, as shown in FIG. 8(c), the first member 11 and the second member 12 are bonded via the conductive bonding portion 13, similar to that shown in FIG. 1(d). A joined metal member assembly 1 is obtained.

Up to this point, we have explained the method for joining metal members when the combination (A1), the preheating method (B1), and the compression firing methods (C1) to (C3) are selected. ) or (A3), the preheating method (B1), (B2) or (B3), and the compression firing method (C1), (C2) or (C3).

Up to this point, we have described the case where one first member and one second member are joined by one metal silver (conductive joint) as the joining method of metal members of this embodiment. In the method for joining metal members according to the embodiment, one first member and one second member may be joined using two or more metal silvers (conductive joints).
Furthermore, in the method for joining metal members of this embodiment, one first member and two or more second members may be joined by one metal silver (conductive joint). In that case, the two or more second members may be all the same, all different, or only partially different.
Further, in the method for joining metal members of the present embodiment, one first member and two or more second members may be joined using two or more metal silvers (conductive joints). In that case, the number of second members and the number of metal silver (conductive joints) may be the same or different. Further, the two or more second members may be all the same, all different, or only some of them may be different.
The number of first members and the number of second members illustrated here may be reversed.
Next, the silver ink composition used in this embodiment will be explained in detail.

<Silver ink composition>
The silver ink composition contains the silver carboxylate, the amine compound, and formic acid.
It is preferable that the silver ink composition does not contain a resin component such as a binder, and it is more preferable that the silver carboxylate is uniformly dispersed at the time of blending.

By using the silver carboxylate, metallic silver is generated from the silver carboxylate, and a conductive joint containing this metallic silver as a main component is formed. In this case, in the conductive joint, the resin component is preferably not used, so that the proportion of metallic silver can be made sufficiently high so that the conductive joint can be considered to consist only of metallic silver. can. In this case, for example, the ratio of the total mass of metallic silver in the conductive joint to the total mass of the conductive joint is, for example, 97% by mass or more, 98% by mass or more, or 99% by mass or more. Is possible. The upper limit of the ratio is, for example, 100% by mass, 99.9% by mass, 99.8% by mass, 99.7% by mass, 99.6% by mass, 99.5% by mass, 99.4% by mass, 99% by mass. .3% by mass, 99.2% by mass, and 99.1% by mass, but these are examples.

[Silver carboxylate]
The silver carboxylate is a silver salt of carboxylic acid and has a group represented by the formula "-COOAg".
The silver carboxylate is not particularly limited as long as it has a group represented by the formula "--COOAg". For example, the number of groups represented by the formula "--COOAg" in one molecule of silver carboxylate may be only one, or two or more. Furthermore, the position of the group represented by the formula "-COOAg" in the silver carboxylate is not particularly limited.

In this embodiment, the silver carboxylates may be used alone or in combination of two or more, and when two or more are used in combination, the combination and ratio thereof may be arbitrarily determined. Can be adjusted.

The silver carboxylate is represented by the following general formula (1) (hereinafter sometimes abbreviated as "β-ketocarboxylic silver (1)") and the following general formula (4). The silver carboxylate is preferably one or more selected from the group consisting of silver carboxylate (hereinafter sometimes abbreviated as "silver carboxylate (4)").
In addition, in this specification, unless otherwise specified, the term "silver carboxylate" refers not only to "silver β-ketocarboxylate (1)" and "silver carboxylate (4)" but also to "silver carboxylate (4)". Inclusive, it means "silver carboxylate having a group represented by the formula "-COOAg"."

（式中、Ｒは１個以上の水素原子が置換基で置換されていてもよい炭素数１～２０の脂肪族炭化水素基若しくはフェニル基、水酸基、アミノ基、又は一般式「Ｒ^１－ＣＹ^１ _２－」、「ＣＹ^１ _３－」、「Ｒ^１－ＣＨＹ^１－」、「Ｒ^２Ｏ－」、「Ｒ^５Ｒ^４Ｎ－」、「（Ｒ^３Ｏ）_２ＣＹ^１－」若しくは「Ｒ^６－Ｃ（＝Ｏ）－ＣＹ^１ _２－」で表される基であり；
Ｙ^１はそれぞれ独立にフッ素原子、塩素原子、臭素原子又は水素原子であり；Ｒ^１は炭素数１～１９の脂肪族炭化水素基又はフェニル基であり；Ｒ^２は炭素数１～２０の脂肪族炭化水素基であり；Ｒ^３は炭素数１～１６の脂肪族炭化水素基であり；Ｒ^４及びＲ^５はそれぞれ独立に炭素数１～１８の脂肪族炭化水素基であり；Ｒ^６は炭素数１～１９の脂肪族炭化水素基、水酸基又は式「ＡｇＯ－」で表される基であり；
Ｘ^１はそれぞれ独立に水素原子、炭素数１～２０の脂肪族炭化水素基、ハロゲン原子、１個以上の水素原子が置換基で置換されていてもよいフェニル基若しくはベンジル基、シアノ基、Ｎ－フタロイル－３－アミノプロピル基、２－エトキシビニル基、又は一般式「Ｒ^７Ｏ－」、「Ｒ^７Ｓ－」、「Ｒ^７－Ｃ（＝Ｏ）－」若しくは「Ｒ^７－Ｃ（＝Ｏ）－Ｏ－」で表される基であり；
Ｒ^７は、炭素数１～１０の脂肪族炭化水素基、チエニル基、又は１個以上の水素原子が置換基で置換されていてもよいフェニル基若しくはジフェニル基である。）

(In the formula, R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group of the general formula "R ¹ -CY ¹ ₂ -", "CY ¹ ₃ -", "R ¹ -CHY ¹ -", "R ² O-", "R ⁵ R ⁴ N-", "(R ³ O) ₂ CY ¹ -" or " A group represented by "R ⁶ -C(=O)-CY ¹ ₂ -";
Y ¹ is each independently a fluorine atom, chlorine atom, bromine atom, or hydrogen atom; R ¹ is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group; R ² is an aliphatic group having 1 to 20 carbon atoms; R ³ is an aliphatic hydrocarbon group having 1 to 16 carbon atoms; R ⁴ and R ⁵ are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms; R ⁶ is an aliphatic hydrocarbon group having 1 to 18 carbon atoms; An aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-";
X ¹ is each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group or benzyl group in which one or more hydrogen atoms may be substituted with a substituent, a cyano group, N -phthaloyl-3-aminopropyl group, 2-ethoxyvinyl group, or general formula "R ⁷ O-", "R ⁷ S-", "R ⁷ -C(=O)-" or "R ⁷ -C( is a group represented by “=O)-O-”;
R ⁷ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group, or a phenyl group or diphenyl group in which one or more hydrogen atoms may be substituted with a substituent. )

（式中、Ｒ^８は炭素数１～１９の脂肪族炭化水素基、カルボキシ基又は式「－Ｃ（＝Ｏ）－ＯＡｇ」で表される基であり、前記脂肪族炭化水素基がメチレン基を有する場合、１個以上の前記メチレン基はカルボニル基で置換されていてもよい。）

(In the formula, R ⁸ is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a carboxy group, or a group represented by the formula "-C(=O)-OAg", and the aliphatic hydrocarbon group is a methylene group. (in which case, one or more of the methylene groups may be substituted with a carbonyl group.)

(Silver β-ketocarboxylate (1))
Silver β-ketocarboxylate (1) is represented by the above general formula (1).
In the formula, R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group having the general formula "R ¹ -CY ¹ ₂ -", "CY ¹ ₃ -", "R ¹ -CHY ¹ -", "R ² O-", "R ⁵ R ⁴ N-", "(R ³ O) ₂ CY ¹ -" or "R ⁶ -C(=O)-CY ¹ ₂ -".

The aliphatic hydrocarbon group having 1 to 20 carbon atoms in R may be linear, branched, or cyclic (aliphatic cyclic group), and when it is cyclic, it may be monocyclic or polycyclic. It may be either. Further, the aliphatic hydrocarbon group may be either a saturated aliphatic hydrocarbon group or an unsaturated aliphatic hydrocarbon group. The aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Preferred aliphatic hydrocarbon groups for R include, for example, alkyl groups, alkenyl groups, alkynyl groups, and the like.

Examples of the linear or branched alkyl group in R include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, neopentyl group, tert-pentyl group, 1-methylbutyl group, 2-methylbutyl group, n-hexyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4 -Methylpentyl group, 1,1-dimethylbutyl group, 2,2-dimethylbutyl group, 3,3-dimethylbutyl group, 2,3-dimethylbutyl group, 1-ethylbutyl group, 2-ethylbutyl group, 3-ethylbutyl group group, 1-ethyl-1-methylpropyl group, n-heptyl group, 1-methylhexyl group, 2-methylhexyl group, 3-methylhexyl group, 4-methylhexyl group, 5-methylhexyl group, 1,1 -dimethylpentyl group, 2,2-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,3-dimethylpentyl group, 4,4-dimethylpentyl group, 1-ethylpentyl group , 2-ethylpentyl group, 3-ethylpentyl group, 4-ethylpentyl group, 2,2,3-trimethylbutyl group, 1-propylbutyl group, n-octyl group, isooctyl group, 1-methylheptyl group, 2 -Methylheptyl group, 3-methylheptyl group, 4-methylheptyl group, 5-methylheptyl group, 1-ethylhexyl group, 2-ethylhexyl group, 3-ethylhexyl group, 4-ethylhexyl group, 5-ethylhexyl group, 1, 1-dimethylhexyl group, 2,2-dimethylhexyl group, 3,3-dimethylhexyl group, 4,4-dimethylhexyl group, 5,5-dimethylhexyl group, 1,2,3-trimethylpentyl group, 1, 2,4-trimethylpentyl group, 2,3,4-trimethylpentyl group, 2,4,4-trimethylpentyl group, 1,4,4-trimethylpentyl group, 3,4,4-trimethylpentyl group, 1, 1,2-trimethylpentyl group, 1,1,3-trimethylpentyl group, 1,1,4-trimethylpentyl group, 1,2,2-trimethylpentyl group, 2,2,3-trimethylpentyl group, 2, 2,4-trimethylpentyl group, 1,3,3-trimethylpentyl group, 2,3,3-trimethylpentyl group, 3,3,4-trimethylpentyl group, 1-propylpentyl group, 2-propylpentyl group, Examples include nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, hexadecyl group, heptadecyl group, octadecyl group, nonadecyl group, icosyl group, and the like.
Examples of the cyclic alkyl group in R include a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a cyclodecyl group, a norbornyl group, an isobornyl group, a 1-adamantyl group, Examples include 2-adamantyl group and tricyclodecyl group.

Examples of the alkenyl group in R include a group in which one single bond (CC) between carbon atoms of the alkyl group in R is replaced with a double bond (C=C).
Examples of such alkenyl groups include vinyl group (ethenyl group, -CH=CH ₂ ), allyl group (2-propenyl group, -CH ₂ -CH=CH ₂ ), 1-propenyl group (-CH= CH-CH ₃ ), isopropenyl group (-C(CH ₃ )=CH ₂ ), 1-butenyl group (-CH=CH-CH ₂ -CH ₃ ), 2-butenyl group (-CH ₂ -CH=CH -CH ₃ ), 3-butenyl group (-CH ₂ -CH ₂ -CH=CH ₂ ), cyclohexenyl group, cyclopentenyl group, and the like.

Examples of the alkynyl group in R include a group in which one single bond (CC) between carbon atoms of the alkyl group in R is replaced with a triple bond (C≡C).
Examples of such alkynyl groups include ethynyl group (-C≡CH) and propargyl group (-CH ₂ -C≡CH).

In the aliphatic hydrocarbon group having 1 to 20 carbon atoms in R, one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include a fluorine atom, a chlorine atom, a bromine atom, and the like. Further, in the aliphatic hydrocarbon group, the number and position of the substituents are not particularly limited. When the number of substituents is plural, these plural substituents may be the same or different from each other. That is, all substituents may be the same, all substituents may be different, or only some substituents may be different.

In the phenyl group in R, one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include a saturated or unsaturated monovalent aliphatic hydrocarbon group having 1 to 16 carbon atoms, a monovalent group in which the aliphatic hydrocarbon group is bonded to an oxygen atom, and fluorine. Examples include atom, chlorine atom, bromine atom, hydroxyl group (-OH), cyano group (-C≡N), phenoxy group (-O-C ₆ H ₅ ), and the like. In the phenyl group having a substituent, the number and position of the substituent are not particularly limited. When the number of substituents is plural, these plural substituents may be the same or different from each other.
Examples of the aliphatic hydrocarbon group as a substituent include those similar to the aliphatic hydrocarbon group for R except that the number of carbon atoms is 1 to 16.

Y ¹ in R is each independently a fluorine atom, a chlorine atom, a bromine atom or a hydrogen atom. In the general formulas "R ¹ -CY ¹ ₂ -", "CY ¹ ₃ -" and "R ⁶ -C(=O)-CY ¹ ₂ -", a plurality of Y ^1s may be the same or the same. May be different.

R ¹ in R is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group (C ₆ H ₅ -). Examples of the aliphatic hydrocarbon group for R ¹ include those similar to the aliphatic hydrocarbon group for R except that the number of carbon atoms is 1 to 19.
R ² in R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, and examples thereof include the same aliphatic hydrocarbon groups as the above-mentioned aliphatic hydrocarbon group in R.
R ³ in R is an aliphatic hydrocarbon group having 1 to 16 carbon atoms. Examples of the aliphatic hydrocarbon group for R ³ include those similar to the aliphatic hydrocarbon group for R except that the number of carbon atoms is 1 to 16.
R ⁴ and R ⁵ in R are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms. That is, R ⁴ and R ⁵ may be the same or different from each other, and the aliphatic hydrocarbon group in R ⁴ and R ⁵ may be the same as the aliphatic hydrocarbon group in R, for example, except that the number of carbon atoms is 1 to 18. Examples include those similar to aliphatic hydrocarbon groups.
R ⁶ in R is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-". Examples of the aliphatic hydrocarbon group for R ⁶ include those similar to the aliphatic hydrocarbon group for R except that the number of carbon atoms is 1 to 19.

Among the above, R is preferably a linear or branched alkyl group, a group represented by the general formula "R ⁶ -C(=O)-CY ¹ ₂ -", a hydroxyl group, or a phenyl group. . Further, R ⁶ is preferably a linear or branched alkyl group, a hydroxyl group, or a group represented by the formula "AgO-".

In general formula (1), X ¹ is each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group in which one or more hydrogen atoms may be substituted with a substituent, or Benzyl group (C ₆ H ₅ -CH ₂ -), cyano group, N-phthaloyl-3-aminopropyl group, 2-ethoxyvinyl group (C ₂ H ₅ -O-CH=CH-), or the general formula "R ⁷ O-", "R ⁷ S-", "R ⁷ -C(=O)-", or "R ⁷ -C(=O)-O-".
Examples of the aliphatic hydrocarbon group having 1 to 20 carbon atoms for X ¹ include the same aliphatic hydrocarbon groups as for R.

Examples of the halogen atom for X ¹ include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.
In the phenyl group and benzyl group in X ¹ , one or more hydrogen atoms may be substituted with a substituent. Preferred examples of the substituent include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), a nitro group (-NO ₂ ), and the like. In the phenyl group and benzyl group having substituents, the number and position of the substituents are not particularly limited. When the number of substituents is plural, these plural substituents may be the same or different from each other.

R ⁷ in X ¹ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group (C ₄ H ₃ S-), a phenyl group in which one or more hydrogen atoms may be substituted with a substituent, or It is a diphenyl group (biphenyl group, C ₆ H ₅ -C ₆ H ₄ -). Examples of the aliphatic hydrocarbon group for R ⁷ include those similar to the aliphatic hydrocarbon group for R except that the number of carbon atoms is 1 to 10. Furthermore, examples of the substituent that the phenyl group and diphenyl group in R ⁷ have include a halogen atom (fluorine atom, chlorine atom, bromine atom, iodine atom), and the like. In the phenyl group and diphenyl group having substituents, the number and position of the substituents are not particularly limited. When the number of substituents is plural, these plural substituents may be the same or different from each other.
When R ⁷ is a thienyl group or a diphenyl group, the bonding position of these to the adjacent group or atom (oxygen atom, sulfur atom, carbonyl group, carbonyloxy group) in X ¹ is not particularly limited. For example, the thienyl group may be either a 2-thienyl group or a 3-thienyl group.

In general formula (1), two X ¹ 's may be bonded as one group to the carbon atom sandwiched between two carbonyl groups via a double bond. Examples of such X ¹ include a group represented by the formula "=CH-C ₆ H ₄ --NO ₂ ".

Among the above, X ¹ is preferably a hydrogen atom, a linear or branched alkyl group, a benzyl group, or a group represented by the general formula "R ⁷ -C(=O)-", It is preferable that at least one of X ¹ is a hydrogen atom.

Silver β-ketocarboxylate (1) is silver 2-methylacetoacetate (CH ₃ -C(=O)-CH(CH ₃ )-C(=O)-OAg), silver acetoacetate (CH ₃ -C(= O)-CH ₂ -C(=O)-OAg), silver 2-ethylacetoacetate (CH ₃ -C(=O)-CH(CH ₂ CH ₃ )-C(=O)-OAg), silver propionyl acetate (CH ₃ CH ₂ -C(=O)-CH ₂ -C(=O)-OAg), isobutyryl silver acetate ((CH ₃ ) ₂ CH-C(=O)-CH ₂ -C(=O)- OAg), silver pivaloyl acetate ((CH ₃ ) ₃ C-C(=O)-CH ₂ -C(=O)-OAg), silver caproyl acetate (CH ₃ (CH ₂ ) ₃ CH ₂ -C(=O )-CH ₂ -C(=O)-OAg), 2-n-butylacetoacetic silver (CH ₃ -C(=O)-CH(CH ₂ CH ₂ CH ₂ CH ₃ )-C(=O)-OAg ), 2-benzylacetoacetate (CH ₃ -C(=O)-CH(CH ₂ C ₆ H ₅ )-C(=O)-OAg), silver benzoylacetate (C ₆ H ₅ -C(=O )-CH ₂ -C(=O)-OAg), silver pivaloylacetoacetate ((CH ₃ ) ₃ C-C(=O)-CH ₂ -C(=O)-CH ₂ -C(=O)-OAg ), silver isobutyrylacetoacetate ((CH ₃ ) ₂ CH-C(=O)-CH ₂ -C(=O)-CH ₂ -C(=O)-OAg), 2-acetylpivaloyl acetate Silver ((CH ₃ ) ₃ C-C(=O)-CH(-C(=O)-CH ₃ )-C(=O)-OAg), 2-acetylisobutyrylsilver acetate ((CH ₃ ) ₂ CH-C(=O)-CH(-C(=O)-CH ₃ )-C(=O)-OAg), or silver acetone dicarboxylate (AgO-C(=O)-CH ₂ -C( =O)-CH ₂ -C(=O)-OAg) is preferred.

In the conductor (metallic silver) formed by solidification treatment such as drying treatment or heating (calcination) treatment of the silver ink composition using silver β-ketocarboxylate (1), the concentration of remaining raw materials and impurities can be reduced. It can be further reduced. In such a conductor, the less raw materials and impurities there are, the better the contact between the formed metal silvers, the easier the conduction, and the lower the resistivity.

As described below, silver β-ketocarboxylate (1) decomposes at a low temperature of preferably 60 to 210°C, more preferably 60 to 200°C, without using a reducing agent or the like known in the art. Can form metallic silver. When β-ketocarboxylic acid silver (1) is used in combination with a reducing agent, it decomposes at a lower temperature to form metallic silver.

In the present invention, β-ketocarboxylic acid silver (1) may be used alone or in combination of two or more types, and when two or more types are used in combination, the combination and ratio thereof are , can be adjusted arbitrarily.

(Silver carboxylate (4))
Silver carboxylate (4) is represented by the general formula (4).
In the formula, R ⁸ is an aliphatic hydrocarbon group having 1 to 19 carbon atoms, a carboxy group (-COOH), or a group represented by the formula "-C(=O)-OAg".
Examples of the aliphatic hydrocarbon group for R ⁸ include those similar to the aliphatic hydrocarbon group for R, except that the number of carbon atoms is 1 to 19. However, the aliphatic hydrocarbon group in R ⁸ preferably has 1 to 15 carbon atoms, more preferably 1 to 10 carbon atoms.

When the aliphatic hydrocarbon group in R ⁸ has a methylene group (-CH ₂ -), one or more of the methylene groups may be substituted with a carbonyl group. The number and position of methylene groups which may be substituted with carbonyl groups are not particularly limited, and all methylene groups may be substituted with carbonyl groups. Here, the term "methylene group" refers not only to a single group represented by the formula "-CH ₂ --" but also to one of the alkylene groups in which multiple groups represented by the formula "-CH ₂ --" are connected. It also includes a group represented by the formula "-CH ₂ --".

Silver carboxylate (4) is silver pyruvate (CH ₃ -C(=O)-C(=O)-OAg), silver acetate (CH ₃ -C(=O)-OAg), silver butyrate (CH ₃ -(CH ₂ ) ₂ -C(=O)-OAg), silver isobutyrate ((CH ₃ ) ₂ CH-C(=O)-OAg), silver 2-ethylhexanoate (CH ₃ -(CH ₂ ) ₃ -CH(CH ₂ CH ₃ )-C(=O)-OAg), silver neodecanoate, silver oxalate (AgO-C(=O)-C(=O)-OAg), or silver malonate ( AgO—C(=O)—CH ₂ —C(=O)—OAg) is preferred. In addition, 2 of the above silver oxalate (AgO-C(=O)-C(=O)-OAg) and silver malonate (AgO-C(=O)-CH ₂ -C(=O)-OAg) Groups represented by the formula "-COOAg", one of which becomes a group represented by the formula "-COOH" (HO-C(=O)-C(=O)-OAg, HO -C(=O)-CH ₂ -C(=O)-OAg) is also preferred.

In the case of using silver carboxylate (4), as in the case of using silver β-ketocarboxylate (1), the ink composition is formed by solidification treatment such as drying treatment or heating (baking) treatment of the silver ink composition. In the conductor (metallic silver), the concentration of remaining raw materials and impurities can be further reduced. When silver carboxylate (4) is used in combination with a reducing agent, it decomposes at a lower temperature to form metallic silver.

In the present invention, carboxylic acid silver (4) may be used alone or in combination of two or more types. When two or more types are used in combination, the combination and ratio thereof are arbitrary. It can be adjusted to

The silver carboxylate is preferably silver β-ketocarboxylate (1).
Among these silver β-ketocarboxylate (1), silver 2-methylacetoacetate, silver acetoacetate, silver isobutyryl acetate, and silver pivaloyl acetate have excellent compatibility with nitrogen-containing compounds (among them amine compounds), which will be described later. , is particularly suitable for increasing the concentration of silver ink compositions.

The ratio of the total mass of silver derived from the silver carboxylate in the silver ink composition to the total mass of the silver ink composition is preferably 5% by mass or more, more preferably 8% by mass or more. . When the ratio is within this range, the formed conductive layer (silver layer) has better quality. The upper limit of the ratio is not particularly limited as long as it does not impair the effects of the present invention, but in consideration of the ease of handling the silver ink composition, etc., it is preferably 25% by mass.
In this specification, unless otherwise specified, "silver derived from silver carboxylate" has the same meaning as silver in silver carboxylate blended at the time of manufacturing a silver ink composition, and continues to be used even after blending. Contains all of the silver that makes up the silver carboxylate, the silver in the decomposition products generated by the decomposition of the silver carboxylate after blending, and the silver itself (metallic silver) generated by the decomposition of the silver carboxylate after blending. Concept.

[Amine compound]
The amine compound preferably has 1 to 25 carbon atoms, and may be any of primary amines, secondary amines, and tertiary amines.
The amine compound may be linear, branched, or cyclic.
In addition, in this specification, a "linear amine compound" means "an amine compound whose main chain is linear", and a "branched amine compound" means "an amine compound whose main chain is branched". The term "cyclic amine compound" means "an amine compound whose main chain is cyclic". The "main chain" means a chain structure to which an amine moiety (for example, an amino group (-NH ₂ ) of a primary amine), which will be described later, is directly bonded.

In the amine compound, the number of nitrogen atoms constituting the amine moiety (for example, the nitrogen atoms constituting the amino group (-NH ₂ ) of the primary amine) may be one or two or more. You can.

Examples of the primary amine include monoalkylamines, monoarylamines, mono(heteroaryl)amines, and diamines in which one or more hydrogen atoms may be substituted with a substituent.

The alkyl group constituting the monoalkylamine may be linear, branched, or cyclic, and examples of such alkyl groups include those similar to the alkyl group in R. . The alkyl group is preferably a linear or branched alkyl group having 1 to 19 carbon atoms, or a cyclic alkyl group having 3 to 7 carbon atoms.
Preferred monoalkylamines include, for example, n-butylamine, n-hexylamine, n-octylamine, n-dodecylamine, n-octadecylamine, isobutylamine, sec-butylamine, tert-butylamine, 3 -aminopentane, 3-methylbutylamine, 2-heptylamine (2-aminoheptane), 2-aminooctane, 2-ethylhexylamine, 1,2-dimethyl-n-propylamine, and the like.

Examples of the aryl group constituting the monoarylamine include phenyl group, 1-naphthyl group, and 2-naphthyl group. The number of carbon atoms in the aryl group is preferably 6 to 10.

The heteroaryl group constituting the mono(heteroaryl)amine has a hetero atom as an atom constituting the aromatic ring skeleton, and the hetero atom includes, for example, a nitrogen atom, a sulfur atom, an oxygen atom, a boron atom. etc. Further, the number of the heteroatoms constituting the aromatic ring skeleton is not particularly limited, and may be one or two or more. When there are two or more heteroatoms, these heteroatoms may be the same or different. That is, these heteroatoms may be all the same, all different, or only some of them may be different.
The heteroaryl group may be either monocyclic or polycyclic, and the number of ring members (number of atoms constituting the ring skeleton) is not particularly limited, but is preferably a 3- to 12-membered ring.

Examples of the monocyclic heteroaryl group having 1 to 4 nitrogen atoms include pyrrolyl group, pyrrolinyl group, imidazolyl group, pyrazolyl group, pyridyl group, pyrimidyl group, pyrazinyl group, pyridazinyl group, triazolyl group, Examples include a tetrazolyl group, a pyrrolidinyl group, an imidazolidinyl group, a piperidinyl group, a pyrazolidinyl group, a piperazinyl group, and such a heteroaryl group is preferably a 3- to 8-membered ring, more preferably a 5- to 6-membered ring. More preferred.
Examples of the monocyclic heteroaryl group having one oxygen atom include a furanyl group, and such a heteroaryl group is preferably a 3- to 8-membered ring, and a 5- to 6-membered ring. A membered ring is more preferable.
Examples of the monocyclic heteroaryl group having one sulfur atom include a thienyl group, and such a heteroaryl group is preferably a 3- to 8-membered ring, and a 5- to 6-membered ring. A membered ring is more preferable.
Examples of the monocyclic heteroaryl group having 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms include oxazolyl group, isoxazolyl group, oxadiazolyl group, morpholinyl group, etc. The heteroaryl group is preferably a 3- to 8-membered ring, more preferably a 5- to 6-membered ring.
Examples of the monocyclic heteroaryl group having 1 to 2 sulfur atoms and 1 to 3 nitrogen atoms include thiazolyl group, thiadiazolyl group, thiazolidinyl group, etc. is preferably a 3- to 8-membered ring, more preferably a 5- to 6-membered ring.
Examples of the polycyclic heteroaryl group having 1 to 5 nitrogen atoms include an indolyl group, an isoindolyl group, an indolizinyl group, a benzimidazolyl group, a quinolyl group, an isoquinolyl group, an indazolyl group, and a benzotriazolyl group. , tetrazolopyridyl group, tetrazolopyridazinyl group, dihydrotriazolopyridazinyl group, etc. Such heteroaryl group is preferably a 7- to 12-membered ring, and preferably a 9- to 10-membered ring. A ring is more preferable.
Examples of the heteroaryl group having 1 to 3 sulfur atoms include a dithianaphthalenyl group and a benzothiophenyl group, and such heteroaryl groups have 7 to 12 members. It is preferably a ring, more preferably a 9- to 10-membered ring.
Examples of the polycyclic heteroaryl group having 1 to 2 oxygen atoms and 1 to 3 nitrogen atoms include benzoxazolyl group, benzoxadiazolyl group, etc. The heteroaryl group is preferably a 7- to 12-membered ring, more preferably a 9- to 10-membered ring.
Examples of the polycyclic heteroaryl group having 1 to 2 sulfur atoms and 1 to 3 nitrogen atoms include benzothiazolyl group, benzothiadiazolyl group, etc. is preferably a 7- to 12-membered ring, more preferably a 9- to 10-membered ring.

The diamine only needs to have two amino groups, and the positional relationship between the two amino groups is not particularly limited. Preferred examples of the diamine include, for example, in the monoalkylamine, monoarylamine, or mono(heteroaryl)amine, one hydrogen atom other than the hydrogen atom constituting the amino group (-NH ₂ ) is substituted with an amino group. Examples include those that have been made.
The diamine preferably has 1 to 10 carbon atoms. More preferred examples of the diamine include ethylenediamine, 1,3-diaminopropane, and 1,4-diaminobutane.

Examples of the secondary amine include dialkylamines, diarylamines, di(heteroaryl)amines, and the like, in which one or more hydrogen atoms may be substituted with a substituent.

The alkyl group constituting the dialkylamine is the same as the alkyl group constituting the monoalkylamine, and is a linear or branched alkyl group having 1 to 9 carbon atoms, or a linear or branched alkyl group having 3 to 7 carbon atoms. A cyclic alkyl group is preferred. Moreover, two alkyl groups in one molecule of dialkylamine may be the same or different from each other.
Specific examples of the preferable dialkylamine include N-methyl-n-hexylamine, diisobutylamine, di(2-ethylhexyl)amine, and the like.

The aryl group constituting the diarylamine is similar to the aryl group constituting the monoarylamine, and preferably has 6 to 10 carbon atoms. Furthermore, two aryl groups in one molecule of diarylamine may be the same or different.

The heteroaryl group constituting the di(heteroaryl)amine is the same as the heteroaryl group constituting the mono(heteroaryl)amine, and is preferably a 6- to 12-membered ring. Further, two heteroaryl groups in one molecule of di(heteroaryl)amine may be the same or different from each other.

Examples of the tertiary amine include trialkylamines and dialkylmonoarylamines in which one or more hydrogen atoms may be substituted with a substituent.

The alkyl group constituting the trialkylamine is the same as the alkyl group constituting the monoalkylamine, and is a linear or branched alkyl group having 1 to 19 carbon atoms, or a linear or branched alkyl group having 3 to 7 carbon atoms. is preferably a cyclic alkyl group. Further, the three alkyl groups in one molecule of trialkylamine may be the same or different from each other. That is, all three alkyl groups may be the same, all different, or only some of them may be different.
Preferred examples of the trialkylamine include, for example, N,N-dimethyl-n-octadecylamine, N,N-dimethylcyclohexylamine, and the like.

The alkyl group constituting the dialkyl monoarylamine is the same as the alkyl group constituting the monoalkylamine, and is a linear or branched alkyl group having 1 to 6 carbon atoms, or a linear or branched alkyl group having 3 to 6 carbon atoms. 7 is preferably a cyclic alkyl group. Furthermore, two alkyl groups in one molecule of dialkylmonoarylamine may be the same or different.
The aryl group constituting the dialkyl monoarylamine is the same as the aryl group constituting the monoarylamine, and preferably has 6 to 10 carbon atoms.

Up to this point, we have mainly explained chain-like amine compounds, but the amine compounds are heterocyclic compounds in which the nitrogen atom constituting the amine moiety is part of a ring skeleton structure (heterocyclic skeleton structure). You can. That is, the amine compound may be a cyclic amine. The ring (ring containing the nitrogen atom constituting the amine moiety) structure at this time may be either monocyclic or polycyclic, and the number of ring members (the number of atoms constituting the ring skeleton) is not particularly limited. , either an aliphatic ring or an aromatic ring.
Preferred cyclic amines include, for example, pyridine.

In the above-mentioned primary amine, secondary amine, and tertiary amine, "a hydrogen atom that may be substituted with a substituent" refers to a hydrogen atom other than the hydrogen atom bonded to the nitrogen atom constituting the amine moiety. It is an atom. The number of substituents at this time is not particularly limited, and may be one, two or more, and all of the hydrogen atoms may be substituted with substituents. When the number of substituents is plural, these plural substituents may be the same or different from each other. That is, the plurality of substituents may all be the same, all different, or only some of them may be different. Moreover, the position of the substituent is not particularly limited either.

Examples of the substituent in the amine compound include an alkyl group, an aryl group, a halogen atom, a cyano group, a nitro group, a hydroxyl group, and a trifluoromethyl group (-CF ₃ ). Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.

When the alkyl group constituting the monoalkylamine has a substituent, the alkyl group is a linear or branched alkyl group having 1 to 9 carbon atoms, or a substituent having an aryl group as a substituent. It is preferably a cyclic alkyl group having 3 to 7 carbon atoms, which preferably has an alkyl group having 1 to 5 carbon atoms. Specific examples of monoalkylamines having such substituents include 2-phenylethylamine, benzylamine, and 2,3-dimethylcyclohexylamine.
Further, in the aryl group and alkyl group which are substituents, one or more hydrogen atoms may be further substituted with a halogen atom. Examples of such monoalkylamines having a substituent substituted with a halogen atom include 2-bromobenzylamine. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.

When the aryl group constituting the monoarylamine has a substituent, the aryl group is preferably an aryl group having 6 to 10 carbon atoms and having a halogen atom as a substituent. Specific examples of monoarylamines having such substituents include bromophenylamine and the like. Here, examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like.

When the alkyl group constituting the dialkylamine has a substituent, the alkyl group is preferably a linear or branched alkyl group having 1 to 9 carbon atoms and having a hydroxyl group or an aryl group as a substituent. Specific examples of dialkylamines having such substituents include diethanolamine, N-methylbenzylamine, and the like.

The amine compounds include n-propylamine, n-butylamine, n-hexylamine, n-octylamine, n-dodecylamine, n-octadecylamine, isobutylamine, sec-butylamine, tert-butylamine, 3-aminopentane, 3-methylbutylamine, 2-heptylamine, 2-aminooctane, 2-ethylhexylamine, 2-phenylethylamine, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, N-methyl-n-hexylamine, diisobutylamine, N-methylbenzylamine, di(2-ethylhexyl)amine, 1,2-dimethyl-n-propylamine, N,N-dimethyl-n-octadecylamine or N,N-dimethylcyclohexylamine It is preferable.
Among these amine compounds, 2-ethylhexylamine has excellent compatibility with the silver carboxylate and is particularly suitable for increasing the concentration of silver ink compositions, and is particularly useful for reducing the surface roughness of metallic silver. listed as suitable.

In this embodiment, the amine compound is preferably linear or branched.

In this embodiment, the amine compound may be used alone or in combination of two or more, and when two or more are used in combination, the combination and ratio thereof can be adjusted as desired. can.

In the silver ink composition, the amount of the amine compound blended is preferably 0.3 to 15 mol, more preferably 0.3 to 12 mol, and more preferably 0.3 to 12 mol, per 1 mol of the silver carboxylate. The amount is particularly preferably 3 to 8 mol, and may be, for example, 0.3 to 5 mol, 0.3 to 3 mol, or 0.3 to 1.5 mol. When the amount of the amine compound is within this range, the stability of the silver ink composition is further improved, and the quality of the metallic silver is further improved.

[Formic acid]
In the silver ink composition, the amount of formic acid (H-C(=O)-OH) is preferably 0.04 to 3.5 mol per 1 mol of the silver carboxylate, and 0.06 mol. More preferably, the amount is between 0.08 and 1.5 mol, and between 0.1 and 1 mol. When the amount of formic acid is within this range, the silver ink composition can more easily and stably form metallic silver.

[Other ingredients]
The silver ink composition may contain other components that do not correspond to any of the silver carboxylate, the amine compound, and formic acid.
The other components are not particularly limited and can be arbitrarily selected depending on the purpose.
Examples of the other components include alcohol, solvents other than alcohol (herein sometimes simply referred to as "solvent"), and the like.

In this embodiment, when using the other components, the other components may be used alone or in combination of two or more, and when two or more are used in combination, Their combination and ratio can be adjusted as desired.

(alcohol)
The alcohol is preferably an acetylene alcohol represented by the following general formula (2) (hereinafter sometimes abbreviated as "acetylene alcohol (2)").

（式中、Ｒ’及びＲ’’は、それぞれ独立に水素原子、炭素数１～２０のアルキル基、又は１個以上の水素原子が置換基で置換されていてもよいフェニル基である。）

(In the formula, R' and R'' are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a phenyl group in which one or more hydrogen atoms may be substituted with a substituent.)

・Acetylene alcohol (2)
Acetylene alcohol (2) is represented by the above general formula (2).
In the formula, R' and R'' are each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a phenyl group in which one or more hydrogen atoms may be substituted with a substituent.
The alkyl group having 1 to 20 carbon atoms in R' and R'' may be linear, branched, or cyclic, and if cyclic, it may be monocyclic or polycyclic. Examples of the alkyl group in R' and R'' include the same alkyl groups as in R.

Examples of the substituent in which the hydrogen atom of the phenyl group in R' and R'' may be substituted include a saturated or unsaturated monovalent aliphatic hydrocarbon group having 1 to 16 carbon atoms, the aliphatic Examples thereof include a monovalent group formed by bonding a group hydrocarbon group to an oxygen atom, a fluorine atom, a chlorine atom, a bromine atom, a hydroxyl group, a cyano group, a phenoxy group, and the like. These substituents are the same as the substituents in which the hydrogen atom of the phenyl group in R may be substituted. In the phenyl group having a substituent, the number and position of the substituent are not particularly limited, and when there is a plurality of substituents, the plurality of substituents may be the same or different from each other.

R' and R'' are preferably a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and preferably a hydrogen atom or a linear or branched alkyl group having 1 to 10 carbon atoms. More preferred.

Preferred acetylene alcohols (2) include, for example, 3,5-dimethyl-1-hexyn-3-ol, 3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol, 2 -propyn-1-ol, 4-ethyl-1-octyn-3-ol, 3-ethyl-1-heptyn-3-ol and the like.

The alcohols may be used alone or in combination of two or more types, and when two or more types are used in combination, the combination and ratio thereof can be adjusted as desired.

(solvent)
The solvent is not particularly limited as long as it is other than alcohol (does not have a hydroxyl group).
However, the solvent is preferably liquid at room temperature.
Examples of the solvent include aromatic hydrocarbons such as toluene, o-xylene, m-xylene, and p-xylene; pentane, hexane, cyclohexane, heptane, octane, cyclooctane, nonane, decane, undecane, dodecane, tridecane, Aliphatic hydrocarbons such as tetradecane, pentadecane, decahydronaphthalene; halogenated hydrocarbons such as dichloromethane, chloroform; esters such as ethyl acetate, monomethyl glutarate, dimethyl glutarate; diethyl ether, tetrahydrofuran (THF), 1,2- Examples include ethers such as dimethoxyethane (dimethyl cellosolve); ketones such as acetone, methyl ethyl ketone (MEK), and cyclohexanone; nitrites such as acetonitrile; amides such as N,N-dimethylformamide (DMF) and N,N-dimethylacetamide. .

The blending amount of the other components in the silver ink composition may be appropriately selected depending on the type of the other components.

For example, when acetylene alcohol (2) is used as the other component, the amount of acetylene alcohol (2) in the silver ink composition ranges from 0.01 to 1 mole of silver β-ketocarboxylate (1). The amount is preferably 0.7 mol, more preferably 0.02 to 0.5 mol, and particularly preferably 0.02 to 0.3 mol. When the amount of acetylene alcohol (2) is within this range, the stability of the silver ink composition is further improved.

For example, when the solvent is used as the other component, the amount of the solvent may be selected depending on the purpose, such as the viscosity of the silver ink composition. However, normally, in the silver ink composition, the proportion of the solvent to the total amount of the ingredients is preferably 30% by mass or less, more preferably 20% by mass or less, and 10% by mass or less. It is particularly preferable that there be.

For example, when using a component that does not fall under either acetylene alcohol (2) or the solvent as the other component, the ratio of the amount of the other component to the total amount of the components in the silver ink composition is preferably 10% by mass or less, more preferably 5% by mass or less.

Even if the ratio of the amount of the other components to the total amount of the other components is 0 mass, that is, no other components are blended, the silver ink composition sufficiently exhibits its effects.

In the silver ink composition, all of the ingredients may be dissolved, or some or all of the ingredients may be in a dispersed state without being dissolved, but it is important that all of the ingredients are dissolved. Preferably, undissolved components are uniformly dispersed.

<Method for producing silver ink composition>
The silver ink composition is obtained by blending the silver carboxylate, the amine compound, formic acid, and, if necessary, the other components. After blending each component, the resulting blend may be used as it is as a silver ink composition, or if necessary, a purified product obtained by subsequently performing a known purification operation may be used as a silver ink composition. In this embodiment, when the above-mentioned components are mixed, it is possible to suppress the generation of impurities that reduce the conductivity of metal silver. This tendency is particularly remarkable when silver β-ketocarboxylate (1) is used as the silver carboxylate. Therefore, even if the silver ink composition that has not been subjected to a purification operation is used, metallic silver having sufficient conductivity can be obtained.

The order of blending each component is not particularly limited. An example of a preferred blending method for each component is a blending method in which the silver carboxylate is added to the amine compound, and formic acid is added to the resulting mixture.

When blending each component, all the components may be added and then mixed, some of the components may be sequentially added and mixed, or all components may be sequentially added and mixed.
The mixing method is not particularly limited, and includes methods of mixing by rotating a stirring bar or stirring blades; methods of mixing using a mixer, triple roll, kneader, bead mill, etc.; methods of mixing by applying ultrasonic waves, etc. An appropriate method may be selected from known methods.
In the case of uniformly dispersing undissolved components in the silver ink composition, it is preferable to apply a dispersion method using, for example, the above-mentioned three-roll, kneader, or bead mill.

The temperature during blending is not particularly limited as long as each blended component does not deteriorate, but it is preferably -5 to 60°C. The temperature during blending may be appropriately adjusted depending on the types and amounts of the ingredients to be blended so that the resulting mixture has a viscosity that is easy to stir.
Further, the blending time is not particularly limited as long as each blended component does not deteriorate, but it is preferably 10 minutes to 36 hours.

<<Metal member assembly>>
A metal member joined body according to an embodiment of the present invention (metal member joined body of the first aspect) is a metal member joined body obtained by the above-mentioned method for joining metal members, The die shear strength of the manufactured member assembly is 15 MPa or more.
The metal member assembly of this embodiment and its die shear strength are as described above.

The conductive joint in the metal member assembly of the first aspect (in other words, the metallic silver formed from the silver ink composition) is composed of the silver carboxylate, which is a component of the silver ink composition, and the silver carboxylate, which is a component of the silver ink composition. A decomposition product produced by decomposition of any of the amine compound, formic acid, and the other component; any of the silver carboxylate, the amine compound, the formic acid, and the other component; A compound produced by reacting with the decomposition product; a compound produced by any of the silver carboxylate, the amine compound, formic acid, and the other component reacting with each other; may contain very small amounts of impurities. It can be confirmed that the composition of this impurity is clearly different from that of metallic silver formed from other silver ink compositions, which were manufactured by a different combination of essential components than in the case of the silver ink composition.
On the other hand, the firing temperature of the heated silver ink composition in the bonding step can be set to a relatively low temperature. This is because the silver ink composition uses ingredients within the above-mentioned limited range (silver carboxylate, amine compound, formic acid).
That is, the impurities in the metallic silver in the first embodiment reflect the use of the silver ink composition, which has the advantage of being able to form (ie, sinter) metallic silver at relatively low temperatures.

In the metal member assembly according to an embodiment of the present invention (metal member assembly of the second aspect), a first metal member and a second metal member are joined via metal silver. and one or both of the first member and the second member is made of copper, and when the first member is made of copper, the metal member assembly is configured such that the first member and the second member are made of copper. Between the first member and the metal silver, from the first member side toward the metal silver side, a layer containing silver as a main constituent element and a layer containing copper and oxygen as main constituent elements are arranged in this order. and when the second member is made of copper, the metal member assembly is arranged between the second member and the metal silver, from the second member side to the metal silver side. , a layer containing silver as a main constituent element, and a layer containing copper and oxygen as main constituent elements in this order, and the die shear strength of the metal member assembly is 15 MPa or more.
The metal member joined body of the second aspect is also obtained by the above-described metal member joining method.

When the first member is made of copper, the metal member assembly of the second aspect includes the first member made of copper, a layer containing silver as a main constituent element, a layer containing copper and oxygen as main constituent elements, and a metal member. It has a layered structure in which silver exists in this order.
When the second member is made of copper, the metal member assembly of the second aspect includes a second member made of copper, a layer containing silver as a main constituent element, a layer containing copper and oxygen as main constituent elements, and a metal member. It has a layered structure in which silver exists in this order.
These laminated structures are completely unexpected in that silver elements and copper elements are arranged alternately.

In the above-mentioned layer containing copper and oxygen as main constituent elements, oxygen may exist as a product of reaction with copper, such as copper oxide, or may exist alone without reacting with copper. You can leave it there.

The above-mentioned "layer containing silver as a main constituent element" means a layer containing silver as a constituent element to such an extent that the properties due to the inclusion of silver are clearly shown, for example, in the target layer. , a layer in which the ratio of the mass of silver element to the total mass of all elements is 50% by mass or more.
The above-mentioned "layer containing copper and oxygen as main constituent elements" means a layer containing copper and oxygen as constituent elements to the extent that the properties due to the presence of copper and oxygen are clearly shown, for example. In the target layer, the ratio of the total mass of copper element and oxygen element to the total mass of all elements is 50% by mass or more.

In this way, in the metal member assembly of the second aspect, the structure is not such that the first member made of copper and the metal silver or the second member made of copper and the metal silver are simply in contact with each other. Although the reason for having the laminated structure as described above is not clear, it is presumed as follows.
That is, according to the manufacturing method of the present embodiment, by using the silver ink composition having a composition within a specific range and performing the preheating step and the bonding step, the first member made of copper or the second member made of copper and the silver The ink composition or its heated material reacts, and the metallic silver diffuses into the first copper member or the second copper member, and the copper in the first copper member or the second copper member reacts. It is presumed that this is because one or both of the following: diffusion into metallic silver occurs. Such diffusion may be related to the reducing action of formic acid, which is a component of the silver ink composition.
Therefore, regardless of whether the first member or the second member is made of copper, it is assumed that the silver in the layer whose main constituent element is silver is derived from the silver ink composition or its heated material. Ru.
Regardless of whether the first member or the second member is made of copper, the copper in the layer whose main constituent elements are copper and oxygen is the first member or the second member which is made of copper. It is assumed that it originates from

The fact that the metal member assembly of the second aspect has the above laminated structure is consistent with the fact that the metal member assembly has a sufficiently high die shear strength.

The die shear strength of the metal member assembly of the second embodiment is 15 MPa or more, and is similar to the die shear strength of the metal member assembly of the first embodiment.

The laminated structure in the metal member assembly of the second aspect is obtained by, for example, producing a cross section in a direction parallel to the joining direction of the first member, metal silver, and second member in the metal member assembly. This cross section can be observed using a transmission electron microscope (TEM) or by energy dispersive X-ray spectroscopy (EDS or EDX). You can check by doing

The use of the metal member assembly of this embodiment (first aspect, second aspect) is not particularly limited. For example, the metal member assembly is useful as an assembly between electrodes in a circuit board. That is, a preferable example of the metal members constituting the metal member assembly, that is, the first member and the second member, is a metal electrode.

<<Circuit board>>
A circuit board according to an embodiment of the present invention includes the metal member assembly on an organic substrate, and the metal member serves as a metal electrode.
As described above, the firing temperature of the heated silver ink composition in the bonding step can be set to a relatively low temperature. This is due to the use of a relatively limited range of ingredients in the silver ink composition.
Therefore, even if an organic substrate containing an organic component such as resin, which has relatively low heat resistance, is used as the constituent material of the substrate and the above-mentioned joining method for metal members is applied to the metal electrode on the organic substrate, the quality will be poor. A circuit board that does not have the above problems can be manufactured. On the other hand, if extremely high heating temperatures are required when joining metal members, such a circuit board cannot be manufactured.

The circuit board of this embodiment can have the same configuration as a known circuit board, except that it includes the above-mentioned metal member assembly having a die shear strength of 15 MPa or more. The circuit board can be manufactured in the same manner as in the case of known circuit boards, except for using the above-mentioned metal member assembly.

Hereinafter, the present invention will be explained in more detail with reference to specific examples. However, the present invention is not limited to the examples shown below.

[Example 1]
<<Manufacture of metal member assembly>>
<Manufacture of silver ink composition>
Silver 2-methylacetoacetate (19.0 g) was added to 2-ethylhexylamine (0.4 times the molar amount relative to silver 2-methylacetoacetate, which will be described later) in a beaker so that the liquid temperature was 50°C or less. A liquid product was obtained by stirring for 15 minutes using a mechanical stirrer. Formic acid (0.7 times the molar amount relative to silver 2-methylacetoacetate) was added dropwise to this liquid over 30 minutes so that the temperature of the reaction solution was 50° C. or lower. After the dropwise addition of formic acid was completed, the reaction solution was further stirred at 25° C. for 1.5 hours to obtain a silver ink composition.

Table 1 shows the types and blending ratios of each compounded component. In Table 1, "amine compound (molar ratio)" refers to the amount of amine compound (number of moles) per mol of silver carboxylate ([number of moles of amine compound]/[number of moles of silver carboxylate]) ]) means. "Mole ratio of formic acid" similarly means the amount (number of moles) of formic acid blended per 1 mole of silver carboxylate ([number of moles of formic acid]/[number of moles of silver carboxylate]).

<Manufacture of metal member assembly>
A copper plate with a size of 12 mm x 8 mm x 0.8 mm and a copper chip with a size of 4 mm x 4 mm x 0.8 mm were prepared as the first member or the second member. Then, these (ie, the copper plate and the copper chip) were polished using water-resistant abrasive paper (grain size 2000) (manufactured by Sankyo Rikagaku Co., Ltd.) moistened with water to clean their surfaces.
Next, a metal mask with a thickness of 0.3 mm, in which two rectangular regions with a size of 4 mm x 4 mm were cut out in parallel, was placed on the cleaned copper plate, and by screen printing, The silver ink composition obtained above was printed all over the copper plate covered with this mask.
As described above, two rectangular parallelepiped printed layers of silver ink compositions each measuring approximately 4 mm x 4 mm x 0.3 mm were formed in parallel on the surface of the copper plate.

Next, under normal pressure and atmosphere, the copper plate with the printed layer is heated from the side without the printed layer using a hot plate, and the temperature of the copper plate and the printed layer is increased to 100°C over 5 minutes. The temperature was raised to 100° C. and further maintained at 100° C. for 1 minute (preheating step). During this time, the printing layer (that is, the silver ink composition) did not solidify and maintained fluidity, and bubbling was observed after the temperature reached 100°C. This bubbling disappeared before the temperature of the copper plate and printed layer was maintained at 100° C. for 1 minute. Through the above steps, a heated silver ink composition was obtained.
The obtained heated product did not have the luster characteristic of metallic silver and was dark green in color.

A total of two such first laminates each having a heated silver ink composition on a copper plate were produced.
These two first laminates were arranged in parallel with their longitudinal directions aligned.

Next, under normal pressure and atmospheric atmosphere, the copper chip is immediately placed on the surface of the heated silver ink composition (printing layer) in the first laminate, and further, a mass is placed on the surface of the copper chip. A 5 kg weight was placed on it. At this time, one copper chip was placed on one heating object, so that when looking down from above, the positions of the heating object and the outer periphery of the copper chip were aligned. Further, one of the weights was placed so as to span all four copper chips, and the placement position of the weights was adjusted so that pressure was evenly applied to these four copper chips.
As described above, a second laminate was produced in which the heated object, the copper chip, and the weight were laminated on the surface of the copper plate while being aligned with each other. The second laminate was composed of two copper plates, four heating objects, four copper chips, and one weight.
At this time, the pressure applied to one copper chip by the weight was 0.8 MPa.

Next, the temperature of the second laminate in this state was raised to 300° C. over 5 minutes under normal pressure and an atmospheric atmosphere, and the temperature was further maintained at 300° C. for 30 minutes (bonding step). In other words, in this step, the copper plate and the copper chip were bonded by metallic silver by firing the heating material while pressing the copper plate and the copper chip with the heating material interposed.
Next, by removing the weight, two metal member joined bodies were obtained in which a copper plate and a copper chip were joined by metal silver. In these bonded bodies, the fired product of the heated material, that is, the conductive bonded portion made of metallic silver had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm.
As described above, in this example, the combination (A1), the preheating method (B1), and the compression firing method (C1) were adopted.

<<Evaluation of silver ink composition>>
<Measurement of viscosity of silver ink composition>
The viscosity of the silver ink composition obtained above was measured at a shear rate of 1000/s at 25° C. using a rheometer (“MCR301” manufactured by Anton Paar). The results are shown in Table 1.

<Calculation of crystallite diameter of metallic silver particles in silver ink composition>
Using an X-ray diffraction device (Bruker AXS, D8 DISCOVER with GADDS), the silver ink composition obtained above was filled into the sample holder, and the metallic silver particles in the silver ink composition were measured under the following measurement conditions. X-ray diffraction measurements were performed.
Next, among the obtained X-ray diffraction profiles, the crystallite diameter was calculated based on the above-mentioned Scherrer equation using the peak of the crystal plane with the highest intensity (2θ=38.1°). The results are shown in Table 1.
(Measurement condition)
・Incidence side optical system X-ray source: CuK (wavelength 1.542 Å)
Output: 50kV, 100mA
Monochromator: Multilayer mirror Beam size: 10mm (H) x 1.0mm (W)
・Receiving side optical system Parallel solar slit resolution: 0.12°
Detector: Scintillation counter Camera distance: 15cm
・Scanning conditions Scanning method: -2 (Locked Coupled)
Scanning speed: 3dig/min
Increment: 0.02°

<<Evaluation of metal member assembly>>
<Measurement of die shear strength>
The two metal member joined bodies obtained above were tested according to JIS C62137-1-2:2010 (lateral push shear strength test, IEC 62137-1-) using a testing machine (Dage "Bond Tester 4000"). 2:2007), the die shear strength was measured.
This measurement was performed for each of the four copper chips, and the average value of the four measured values was finally adopted as the die shear strength of the metal member assembly. The results are shown in Table 2.

<Analysis of bonding state>
Using a focused ion beam (abbreviation: FIB) device, one of the two metal member assembly obtained above was cut to expose the cross section.
The cross section was observed using a transmission electron microscope (TEM). The imaging data acquired at this time is shown in FIG.
At this time, the cross section was further observed by energy dispersive X-ray spectroscopy (EDS, EDX). Among the imaging data acquired at this time, the imaging data when silver element was detected is shown in FIG. 10, the imaging data when copper element was detected is shown in FIG. 11, and the imaging data when oxygen element was detected is shown in FIG. 12. .

[Example 2]
<<Manufacture of metal member assembly>>
<Manufacture of silver ink composition>
A silver ink composition was prepared in the same manner as in Example 1.

<Manufacture of metal member assembly>
Using the same copper plate and copper chip as in Example 1, and using the same method as in Example 1, a rectangular parallelepiped-shaped silver ink composition approximately 4 mm x 4 mm x 0.3 mm in size was applied to the surface of the copper plate. Two printed layers were formed in parallel.

Next, the copper chip is placed on the surface of the printing layer (silver ink composition) under normal pressure and in an atmospheric atmosphere, and when looking down from above, the positions of the printing layer and the outer periphery of the copper chip are aligned. I decided to do so.
Next, under normal pressure and an atmospheric atmosphere, the copper plate with the printed layer is heated from the side without the printed layer using a hot plate, and the copper plate, the printed layer, and the copper chip are heated for 5 minutes. The temperature was raised to 100°C, and the temperature was further maintained at 100°C for 1 minute (preheating step). During this time, the printing layer (that is, the silver ink composition) did not solidify and maintained fluidity, and bubbling was observed after the temperature reached 100°C. This bubbling disappeared before the temperature of the copper plate and printed layer was maintained at 100° C. for 1 minute. Through the above steps, a heated silver ink composition was obtained.
The obtained heated product did not have the luster characteristic of metallic silver and was dark green in color.

Next, a weight of 5 kg was immediately placed on the surface of the copper chip under normal pressure and an atmospheric atmosphere. At this time, one weight was placed on one copper chip so that the center positions of the copper chip and the weight were aligned when looking down from above.
As described above, two laminates were formed on the surface of the copper plate, in which the heated object, the copper chip, and the weight were aligned and laminated.
At this time, the pressure applied to one copper chip by the weight was 0.8 MPa.

Next, a bonding step is performed in the same manner as in Example 1, and the heating material is used to press the copper plate and the copper chip together while firing the heating material, thereby bonding the copper plate and the copper chip with metallic silver. Joined.
Through the above steps, a metal member assembly was obtained in which a copper plate and a copper chip were joined by metal silver. In this bonded body, the fired product of the heated material, that is, the bonded portion made of metallic silver had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm.
Furthermore, another identical metal member assembly was manufactured using the same method, resulting in a total of two metal member assembly.
As mentioned above, in this example, the combination (A1), the preheating method (B2), and the compression firing method (C1) were adopted.

<<Evaluation of silver ink composition>>
The viscosity of the silver ink composition was measured in the same manner as in Example 1, and the crystallite diameter of the metallic silver particles in the silver ink composition was calculated. The results are shown in Table 1.

<<Evaluation of metal member assembly>>
<Measurement of die shear strength>
The die shear strength of the metal member assembly was measured in the same manner as in Example 1 except that the two metal member assembly obtained above were used. The results are shown in Table 2.

<<Manufacture and evaluation of metal member assembly>>
[Example 3]
In the bonding step, instead of raising the temperature of the copper plate and the laminate to 300°C over 5 minutes and holding the temperature at 300°C for 30 minutes, the temperature of the copper plate and the laminate is A metal member assembly was manufactured and evaluated in the same manner as in Example 1, except that the temperature was raised to 250° C. over 5 minutes and then held at 250° C. for 30 minutes.
In Example 3, in the obtained metal member joined body, the fired product of the heated material, that is, the joint made of metallic silver, had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm. Ta. The results are shown in Table 2.

[Example 4]
In the bonding step, instead of raising the temperature of the copper plate and the laminate to 300°C over 5 minutes and holding the temperature at 300°C for 30 minutes, the temperature of the copper plate and the laminate is A metal member assembly was manufactured and evaluated in the same manner as in Example 1, except that the temperature was raised to 200° C. over 5 minutes and then held at 200° C. for 30 minutes.
In Example 4, in the obtained metal member assembly, the fired product of the heated material, that is, the joint made of metallic silver, had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm. Ta. The results are shown in Table 2.

[Comparative example 1]
In the preheating step, after raising the temperature of the copper plate and the printed layer to 100°C, the time for holding the temperature at 100°C was changed to 5 minutes instead of 1 minute (hereinafter, this process will be referred to as "comparison"). (Hereinafter, this process may be referred to as "comparison") and that after the preheating step, the heated object was fired without placing a weight of 5 kg on the surface of the copper chip (hereinafter, this step may be referred to as "comparison"). An attempt was made to manufacture and evaluate a metal member assembly using the same method as in Example 1, except for the following points: That is, in Comparative Example 1, the copper chip is placed on the surface of the heated material of the silver ink composition (printing layer) immediately after the preheating step for comparison, so that the heated material is placed on the surface of the copper plate. Two comparative laminates were formed by aligning and stacking the copper plate and the comparative laminate, and then the temperature of the copper plate in this state and the comparative laminate was increased to 300°C over 5 minutes, and the temperature was further increased. The temperature was maintained at 300° C. for 30 minutes, and thereafter, in the same manner as in Example 1, an attempt was made to bond the copper plate and the copper chip using metallic silver.
However, in Comparative Example 1, the copper plate and the copper chip could not be joined with metallic silver, and the desired metal member joined body could not be obtained.
In Comparative Example 1, the printing layer (ie, the silver ink composition) had solidified and lost fluidity at the end of the comparative preheating step. This solidified product did not have the luster characteristic of metallic silver and was dark green in color. After the temperature of the printed layer reached 100° C., bubbling was observed. In the final product obtained, the fired product of the heated material, that is, the portion composed of metallic silver, had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm. The results are shown in Table 2.

[Comparative example 2]
In the preheating step, after raising the temperature of the copper plate and the printed layer to 100°C, the time for which the temperature was maintained at 100°C was changed to 5 minutes instead of 1 minute (i.e., in the preheating process for comparison). A metal member assembly was manufactured and evaluated in the same manner as in Example 1, except that the following steps were performed.
In Comparative Example 2, the printing layer (ie, the silver ink composition) had solidified and lost fluidity at the end of the comparative preheating step. This solidified product did not have the luster characteristic of metallic silver and was dark green in color. After the temperature of the printed layer reached 100° C., bubbling was observed. In the obtained metal member assembly, the fired product of the heated material, that is, the joint portion made of metallic silver had a rectangular parallelepiped shape with a size of approximately 4 mm x 4 mm x 0.03 mm. The results are shown in Table 2.

As is clear from the above results, in Examples 1 to 4, by performing the preheating step and the bonding step, the die shear strength of the metal member assembly was 17.5 MPa or more (17.5 to 35 MPa), The bonding strength was sufficiently high. In particular, from the results of Examples 1 and 2, it was confirmed that the bonding strength was increased by placing the copper chip after the preheating step (that is, by adopting the preheating method (B1)).

In Examples 1 to 4, the silver ink compositions did not solidify during the preheating step and maintained fluidity. This was evident from the fact that the silver ink composition was bubbling. In Example 2, during the preheating process, the main surface of the silver ink composition (printing layer) was covered with copper chips and was not exposed, and the bubbling of the silver ink composition could not be directly confirmed. However, since slight fluctuations were observed in the copper chip, it was indirectly confirmed that foaming occurred in the silver ink composition.
In addition, in all of Examples 1 to 4, the bubbling of the silver ink composition disappeared by the end of the preheating process, and at this stage, the generation of gas from the silver ink composition was almost complete. It was assumed that it had completely ended.

On the other hand, in Comparative Example 1, a metal member assembly could not be obtained. This is due to the fact that the silver ink composition had solidified at the end of the comparative preheating process, and that the copper plate and copper chip were not pressure bonded during the firing of the heated material in the comparative bonding process. Met.
In Comparative Example 1, after the temperature of the silver ink composition reached 100°C, foaming was initially observed, but before the foaming disappeared, the silver ink composition solidified and the silver ink composition The surface of the heated object was rougher than in Examples 1 to 4 due to the effect of foaming.

In Comparative Example 2, the die shear strength of the metal member assembly was 3 MPa, and the bonding strength was low. This was because the silver ink composition had solidified at the end of the comparative preheating step.
In Comparative Example 2, as in Comparative Example 1, foaming was initially observed after the temperature of the silver ink composition reached 100°C, but before the foaming disappeared, the silver ink composition was solidified, and the surface of the heated silver ink composition was rougher than in Examples 1 to 4 due to the effect of bubbling.
However, in Comparative Example 2, unlike in Comparative Example 1, a metal member joined body was obtained because the copper plate and the copper chip were crimped during the firing of the heated material in the joining process.

FIG. 9 shows TEM imaging data of the boundary between the copper chip and metal silver (conductive junction) and the area in the vicinity thereof.
In FIG. 9, the area on the left side of the image is a copper chip, and the area on the right side of the image is metallic silver.
In FIG. 9, the discolored portions including those indicated by arrows are minute voids (sometimes referred to as "micro voids" in this specification and drawings).
As is clear from FIG. 9, two areas, ie, area 9-1 and area 9-2, which can be distinguished from other areas, were observed between the copper chip and the metal silver, extending over the top and bottom of the image.

FIG. 10 shows imaging data when silver element was detected by EDS (EDX) in the same area as FIG. 9.
In FIG. 10, as in the case of FIG. 9, there are two areas between the copper chip and the metal silver that extend above and below the image and are distinguishable from other areas, namely, area 10-1 and area 10-. 2 was recognized. The shape of region 10-1 was similar to that of region 9-1, and the shape of region 10-2 was similar to that of region 9-2.
The acquired imaging data shows that fluorescence is generated in the metallic silver region and region 10-1, and silver element was detected in these regions. On the other hand, this imaging data did not show that fluorescence was significantly generated in other regions including region 10-2, and no silver element was significantly detected in these regions.

FIG. 11 shows imaging data when copper element was detected by EDS (EDX) in the same area as FIG. 9.
In FIG. 11, as in the case of FIG. 9, there are two areas between the copper chip and the metal silver that extend above and below the image and are distinguishable from other areas, namely, area 11-1 and area 11-. 2 was recognized. The shape of region 11-1 was similar to that of region 9-1, and the shape of region 11-2 was similar to that of region 9-2.
The acquired imaging data shows that fluorescence is generated in the copper chip area and area 11-2, and copper element was detected in these areas. On the other hand, this imaging data did not show that fluorescence was significantly generated in other regions including region 11-1, and copper element was not significantly detected in these regions.

FIG. 12 shows imaging data of the same region as FIG. 9 when oxygen element was detected by EDS (EDX).
In FIG. 12, unlike in the case of FIG. 9, there is one region between the copper chip and the metallic silver that extends above and below the image and is distinguishable from other regions, namely region 12-1. . The shape of region 12-1 was similar to the shape of region 9-2.
The acquired imaging data shows that fluorescence is generated in region 12-1, and oxygen element was detected in this region. On the other hand, this imaging data suggested the generation of weak fluorescence in other regions, but the fluorescence intensity was weak compared to the fluorescence intensity in region 12-1, and the detected amount of oxygen element was was a very small amount.

From the above results, it was found that region 9-1, region 10-1, and region 11-1 represent the same region, and that this region is a layer containing silver as the main constituent element.
In addition, region 9-2, region 10-2, region 11-2, and region 12-1 indicate the same region, and it was found that this region is a layer whose main constituent elements are copper and oxygen. did.
That is, the metal member assembly obtained above includes a layer containing silver as the main constituent element and a layer containing copper and oxygen as the main constituent element between the copper chip and the metal silver, from the copper chip side to the metal silver side. It has been found that the material has layers containing constituent elements in this order. In this way, the metal member assembly has a laminated structure in which a copper chip, a layer containing silver as a main constituent element, a layer containing copper and oxygen as main constituent elements, and metallic silver are present in this order. and the copper element were arranged alternately.

The above results were obtained by analyzing the boundary between the copper chip and metal silver (conductive joint) and the area near it, but the results were obtained by analyzing the boundary between the copper chip and metal silver (conductive joint) and the area near it. Similar results were obtained when analyzing the boundary with silver (conductive junction) and its neighboring regions.
That is, the metal member assembly includes, between the copper plate and metal silver, from the copper plate side to the metal silver side, a layer containing silver as a main constituent element, a layer containing copper and oxygen as main constituent elements, It turns out that they have the following in this order: In this way, the metal member assembly has a laminated structure in which a copper plate, a layer containing silver as a main constituent element, a layer containing copper and oxygen as main constituent elements, and metallic silver exist in this order. Copper elements were arranged alternately.

In the layers containing copper and oxygen as the main constituent elements on both the copper chip side and the copper plate side mentioned above, oxygen may exist as a product of reaction with copper such as copper oxide. There was also a possibility that it existed alone without any reaction.

The fact that the metal member assembly had the above laminated structure was consistent with the fact that the metal member assembly had a sufficiently high die shear strength.

INDUSTRIAL APPLICATION This invention can be utilized for the manufacture of various apparatuses equipped with a metal member assembly including a circuit board.

DESCRIPTION OF SYMBOLS 1, 2...Metal member assembly, 11...Metal first member, 11a...First surface of metal first member, 12...Metal second member, 12a ...First surface of second metal member, 13,23...Metal silver (conductive joint), 130...Silver ink composition, 130'...Heated product of silver ink composition

Claims (3)

A method of joining metal members together,
By heating the silver ink composition attached to the surface of either or both of the first metal member and the second metal member at a temperature of 60° C. or higher without solidifying, a step of obtaining a heated silver ink composition;
By firing the heated material while pressing the first member and the second member together with the unsolidified heated material of the silver ink composition interposed therebetween, the first member and the second member are heated. and a step of joining the two members with metallic silver,
The silver ink composition contains a silver carboxylate having a group represented by the formula "-COOAg", an amine compound, and formic acid, and the silver ink composition converts metallic silver by firing. A method for joining metal members, which are materials for forming. The silver ink composition before being heated without solidifying at a temperature of 60° C. or higher contains particles of metallic silver produced from the silver carboxylate,
The method for joining metal members according to claim 1, wherein the crystallite diameter of the metallic silver particles is less than 20 nm. The method for joining metal members according to claim 1 or 2, wherein the silver carboxylate is silver β-ketocarboxylate represented by the following general formula (1).

(In the formula, R is an aliphatic hydrocarbon group having 1 to 20 carbon atoms, in which one or more hydrogen atoms may be substituted with a substituent, a phenyl group, a hydroxyl group, an amino group, or a group of the general formula "R ¹ -CY ¹ ₂ -", "CY ¹ ₃ -", "R ¹ -CHY ¹ -", "R ² O-", "R ⁵ R ⁴ N-", "(R ³ O) ₂ CY ¹ -" or " A group represented by "R ⁶ -C(=O)-CY ¹ ₂ -";
Y ¹ is each independently a fluorine atom, chlorine atom, bromine atom, or hydrogen atom; R ¹ is an aliphatic hydrocarbon group having 1 to 19 carbon atoms or a phenyl group; R ² is an aliphatic group having 1 to 20 carbon atoms; R ³ is an aliphatic hydrocarbon group having 1 to 16 carbon atoms; R ⁴ and R ⁵ are each independently an aliphatic hydrocarbon group having 1 to 18 carbon atoms; R ⁶ is an aliphatic hydrocarbon group having 1 to 18 carbon atoms; An aliphatic hydrocarbon group having 1 to 19 carbon atoms, a hydroxyl group, or a group represented by the formula "AgO-";
X ¹ is each independently a hydrogen atom, an aliphatic hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a phenyl group or benzyl group in which one or more hydrogen atoms may be substituted with a substituent, a cyano group, N -phthaloyl-3-aminopropyl group, 2-ethoxyvinyl group, or general formula "R ⁷ O-", "R ⁷ S-", "R ⁷ -C(=O)-" or "R ⁷ -C( is a group represented by “=O)-O-”;
R ⁷ is an aliphatic hydrocarbon group having 1 to 10 carbon atoms, a thienyl group, or a phenyl group or diphenyl group in which one or more hydrogen atoms may be substituted with a substituent. )

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