JP2020087765A - Composition for joint - Google Patents

Abstract

To provide a composition for joint excellent in dispersibility even with suppressing used amount of a dispersant, and excellent in joint strength.SOLUTION: There is provided a composition for joint containing a metal powder, a coated metal particle with one or more kinds of molecule selected from a plurality of aliphatic carboxylic acid and aliphatic aldehyde coated on a surface of a metal nuclear particle smaller in particle diameter than the metal powder at density of 2.5 to 5.2 molecules/nm, and liquid paraffin.SELECTED DRAWING: None

Description

The present invention relates to a bonding composition.

Printable electronics, which do not require patterning by exposure by directly printing a dispersion containing metal particles on a wiring pattern by various printing methods such as inkjet, are drawing attention.
It is known that metal particles of several tens of nm or less exhibit various physical and chemical characteristics different from those of bulk metal as the particle diameter becomes smaller. For example, it is known that the melting point of metal particles becomes lower than the melting point of bulk metal when the particle size becomes smaller. Therefore, from the viewpoint of lowering the temperature during sintering, it has been considered to use metal particles having a small particle size. Examples of the printing method include an inkjet printing method, a screen printing method, a flexo printing method, and a dispense printing method.

The present inventors include, in Patent Document 1, a silver nucleus particle and a plurality of aliphatic carboxylic acid molecules arranged on the surface of the silver nucleus particle at a density of 2.5 to 5.2 molecules per 1 nm ^2. , Coated silver particles are disclosed. The coated silver particles are said to have excellent oxidation resistance and sinterability.

On the other hand, Patent Document 2 discloses a copper paste for pressureless bonding containing copper particles and a dispersion medium containing a solvent having a boiling point of 300° C. or higher. It is said that the copper paste for pressureless bonding can achieve sufficient bonding strength even when members having different thermal expansion coefficients are bonded to each other without pressure.

JP, 2017-179403, A JP, 2017-103180, A

Generally, a dispersant is used in a dispersion liquid of metal nanoparticles in order to impart dispersibility to the metal nanoparticles. However, the dispersant may remain during the sintering of the metal nanoparticles, resulting in a decrease in the bonding strength.

The present invention has been made in view of such circumstances, and an object thereof is to provide a bonding composition that is excellent in dispersibility while suppressing the amount of the dispersant used, and is also excellent in bonding strength. ..

One embodiment of the bonding composition according to the present invention is a metal powder and one or more kinds selected from a plurality of aliphatic carboxylic acids and aliphatic aldehydes on the surface of metal core particles having a smaller particle size than the metal powder. Containing coated metal particles having a density of 2.5 to 5.2 molecules/nm ² and liquid paraffin.

One embodiment of the bonding composition according to the present invention further contains an aldehyde solvent.

In one embodiment of the bonding composition according to the present invention, the aldehyde solvent contains decanal.

One embodiment of the bonding composition according to the present invention further contains tocopherol.

According to the present invention, it is possible to provide a bonding composition having excellent dispersibility and bonding strength while suppressing the amount of the dispersant used.

[Composition for bonding]
The bonding composition of the present embodiment contains metal powder and two or more molecules selected from a plurality of aliphatic carboxylic acids and aliphatic aldehydes on the surface of metal core particles having a particle size smaller than that of the metal powder. It contains coated metal particles coated at a density of 0.5 to 5.2 molecules/nm ² and liquid paraffin.
In the bonding composition of the present embodiment, the coated metal particles are sufficiently dispersed by the liquid paraffin as described later. Therefore, the bonding composition of the above embodiment is excellent in dispersibility and bonding strength while suppressing the amount of the dispersant used.

<Metal powder>
As the metal powder used in the present embodiment, a known metal powder used in a bonding composition can be used. The kind of metal in the metal powder is not particularly limited, and one or more kinds can be appropriately selected and used from the metals that can be used for the metal core particles described later. Above all, it is preferable to use copper or silver from the viewpoint of conductivity. The mass ratio of the metal powder and the coated metal particles is not particularly limited, but from the viewpoint of increasing the bonding strength, 20:80 to 80:20 is preferable, 30:70 to 70:30 is more preferable, and 40:60 to 60. : 40 is even more preferable.

The particle size of the metal powder used in this embodiment is not particularly limited, but the average primary particle size of the metal powder is preferably 0.3 or more and 10 μm or less, more preferably 0.4 or more and 5 μm or less, and even more preferably 0. It can be 0.5 or more and 1.0 μm or less. By using the metal powder having an average primary particle diameter of 10 μm or less, the density of the metal powder in the bonding composition can be made more uniform and the bonding strength can be improved. Further, in the present embodiment, plural kinds of metal powders having different average primary particle sizes may be mixed and used. When a mixture of multiple types of metal powders with different average primary particle sizes is used, the metal powder with relatively small average primary particle size enters between the metal powders with relatively large average primary particle size, and the packing density as a whole Can be improved.

<Coated metal particles>
The coated metal particles used in the present embodiment has a plurality of aliphatic carboxylic acids and aliphatic aldehydes (hereinafter, referred to as “aliphatic carboxylic acid or the like”) on the surface of the metal core particles having a smaller particle size than the above-mentioned metal powder. There is one or more kinds of molecules selected from the group) particles having a density of 2.5 to 5.2 molecules/nm ² . The carboxylic group side of the aliphatic carboxylic acid or the like is adsorbed on the surface of the metal core particle to form a monomolecular film. Therefore, it is presumed that the surface of the metal core particle is protected by the aliphatic carboxylic acid or the like and the oxidation is suppressed, and that the metal core particle has high oxidation resistance. For example, in the coated silver particles using silver core particles as the metal core particles, the content ratio of silver oxide and silver hydroxide after 2 months from production is 100% by mass of the silver core particles in the coated silver particles. It is also possible to suppress it to 5 mass% or less. The generation of the metal oxide in the coated metal particles can be confirmed by the X-ray diffraction (XRD) measurement of the coated metal particles.

Further, since the aliphatic carboxylic acid or the like is weakly bonded to the metal core particles by physical adsorption or the like, it is considered that the aliphatic carboxylic acid or the like diffuses and desorbs at a relatively low temperature. Therefore, the surface of each metal core particle is easily exposed by heating and the surfaces of the metal core particles can be brought into contact with each other, so that the coated metal particles have excellent sinterability at low temperature.

(Metal core particles)
The average primary particle diameter of the metal core particles used in the present embodiment is not particularly limited as long as it is smaller than the average primary particle diameter of the metal powder, but from the viewpoint of low temperature sinterability and dispersibility, it is less than 300 nm. The thickness is preferably 250 nm or less, more preferably 200 nm or less. The average primary particle diameter of the metal core particles is usually 1 nm or more, preferably 5 nm or more, and more preferably 20 nm or more. The average primary particle diameter of the metal core particles is an arithmetic average value of the primary particle diameters of any 20 metal core particles observed by a scanning electron microscope (SEM).

The material of the metal core particles may be any metal that exhibits sufficient bonding strength after sintering, for example, gold, silver, copper, platinum, aluminum, iron, chromium, tin, nickel, zinc, lead, indium, bismuth, Examples thereof include germanium, antimony, cobalt, palladium, rhodium, molybdenum, tungsten, titanium, zirconium, gallium, arsenic, boron, silicon, and alloys thereof. Further, the material of the metal core particles is preferably a metal exhibiting conductivity after sintering, of which gold, silver, or copper is more preferable, and silver or copper is still more preferable. By using these metals, the bonding composition of this embodiment can be applied to, for example, printing of electronic circuits. Moreover, since the coated metal particles used in the present embodiment have excellent oxidation resistance, copper can be preferably used as the metal core particles. When there are a plurality of coated metal particles, the contained metal core particles may be the same as or different from each other.

The metal core particles may contain metal oxides, metal hydroxides, and other impurities as long as the effects of the present invention are not impaired. From the viewpoint of conductivity, the content ratio of the metal oxide and the metal hydroxide is preferably 5% by mass or less, more preferably 3% by mass or less, and 1% by mass or less with respect to the metal core particles. Is even more preferable. From the viewpoint of conductivity, the content ratio of the metal in the metal core particles is preferably 95% by mass or more, more preferably 97% by mass or more, and even more preferably 99% by mass or more. preferable.

The shape of the metal core particles can be appropriately selected depending on the application and the like. Examples of the shape include a substantially spherical shape including a true spherical shape, a plate shape, and a rod shape. Among them, the substantially spherical shape is preferable. In addition, according to the method for producing coated metal particles described below, substantially spherical metal core particles that can approximate a spherical shape can be obtained. The particle size of the coated metal particles can be determined by SEM observation.

(Aliphatic carboxylic acid)
In the present embodiment, the aliphatic carboxylic acid is used alone or in combination with an aliphatic aldehyde described below to coat the surface of the metal core particles with a density of 2.5 to 5.2 molecules per 1 nm ² , It has the dispersibility of particles and the effect of suppressing oxidation. Further, during sintering, the aliphatic carboxylic acid is easily removed from the surface of the metal core particles, or decomposed or volatilized, so that the residue in the sintered body is suppressed. Thereby, a conductor having excellent electric conductivity can be obtained.

The aliphatic carboxylic acid is a compound having a structure in which one or two or more carboxy groups are substituted in the aliphatic compound, and in the present embodiment, the carboxylic acid of the aliphatic carboxylic acid is usually present on the surface of the metal core particles. The group is placed. In the present embodiment, a structure in which one carboxy group is substituted in the aliphatic compound, that is, a compound having an aliphatic hydrocarbon group and one carboxy group is preferable.

The aliphatic hydrocarbon group that constitutes the aliphatic carboxylic acid is a hydrocarbon group having a linear, branched, or cyclic structure, and may have an unsaturated bond. In the present embodiment, it is preferable to use a linear aliphatic hydrocarbon group having no branched or cyclic structure from the viewpoint of easily forming a monomolecular film on the surface of the metal core particles with a predetermined density. The unsaturated bond may be a double bond or a triple bond, but is preferably a double bond. When the aliphatic hydrocarbon group has an unsaturated bond, the number thereof is preferably 1 to 3 in one molecule, more preferably 1 to 2, and even more preferably 1. preferable.

In the present embodiment, the aliphatic carboxylic acid preferably has a carboxy group at the end of the linear aliphatic hydrocarbon group, among others. By making the aliphatic hydrocarbon group have a linear structure, the affinity between the coated metal particles and the liquid paraffin can be increased, and the dispersibility of the coated metal particles can be improved. In the aliphatic carboxylic acid, the number of carbon atoms in the aliphatic group is preferably 3 or more, more preferably 5 or more, and even more preferably 7 or more. When the number of carbon atoms is 3 or more, the dispersibility and oxidation resistance of the coated metal particles can be improved. On the other hand, the aliphatic group preferably has 17 or less carbon atoms, more preferably 16 or less carbon atoms, and even more preferably 11 or less carbon atoms. When the number of carbon atoms is 17 or less, the coated metal particles are easily removed during sintering, and a conductor having excellent electric conductivity can be obtained. In addition, in this embodiment, the number of carbon atoms of the aliphatic group does not include the carbon atoms constituting the carboxy group.

Specific examples of preferable aliphatic carboxylic acids include butyric acid, caproic acid, caprylic acid, pelargonic acid, stearic acid, palmitoleic acid, oleic acid, vaccenic acid, linoleic acid, and linolenic acid. The aliphatic carboxylic acids may be used alone or in combination of two or more.

(Aliphatic aldehyde)
In the present embodiment, an aliphatic aldehyde can be arranged on the surface of the metal core particles instead of the aliphatic carboxylic acid or in combination with the aliphatic carboxylic acid. Even in this case, as with the aliphatic carboxylic acid, coated metal particles capable of forming a conductor having excellent electric conductivity can be obtained.

The aliphatic aldehyde is a compound having a structure in which one or two or more aldehyde groups are substituted in the aliphatic compound. The aliphatic aldehyde used in the present embodiment is preferably a compound having a structure in which one aldehyde group is substituted in the aliphatic compound, that is, a compound having an aliphatic hydrocarbon group and one aldehyde group. In this embodiment, the aldehyde group of the aliphatic aldehyde is usually arranged on the surface of the metal core particle. By arranging the aldehyde group on the surface of the metal core particle, the reduction effect of the aliphatic aldehyde suppresses the oxidation of the surface of the metal core particle and the cleaning effect of contaminants can be obtained. Moreover, it is presumed that the aldehyde group is arranged on the surface of the metal core particles to have an effect of removing foreign matters and oxides on the surface of the base material.

As the aliphatic hydrocarbon group constituting the aliphatic aldehyde, the same ones as the above aliphatic carboxylic acid can be selected.
Specific examples of preferable aliphatic aldehydes include butyraldehyde, hexyl aldehyde, octyl aldehyde, nonyl aldehyde, octadecyl aldehyde and hexadecenyl aldehyde. The aliphatic aldehydes may be used alone or in combination of two or more.

The surface of the metal core particle is coated with one or more kinds of molecules (eg, aliphatic carboxylic acid) selected from a plurality of aliphatic carboxylic acids and aliphatic aldehydes at a density of 2.5 to 5.2 molecules/nm ^2. ing. That is, the surface of the metal core particle is coated with a coating layer containing an aliphatic carboxylic acid or the like, and the coating density is 2.5 to 5.2 molecule/nm ² . From the viewpoint of dispersibility and oxidation resistance, it is preferred that the coating density is from 3.0 to 5.2 molecular / nm ^2, and more preferably from 3.5 to 5.2 molecular / nm ^2.

The coating density of aliphatic carvone or the like on the surface of the metal core particles can be calculated as follows. With respect to the coated metal particles, the organic component adhering to the surface is extracted by liquid chromatography (LC) according to the method described in JP 2012-88242 A, and the component analysis is performed. In addition, TG-DTA measurement (thermogravimetric measurement/differential thermal analysis) is performed to measure the amount of organic components contained in the coated metal particles. Next, the amount of the aliphatic carboxylic acid or the like contained in the coated metal particles is calculated together with the LC analysis result. Further, the average primary particle diameter of the metal core particles is measured by SEM image observation.
From the above analysis results, the number of molecules of the aliphatic carboxylic acid or the like contained in 1 g of the coated metal particles is represented by the following formula (a).
[The number of molecules, such as aliphatic carboxylic _{acids] = M A / (M w} / N A) ··· (a)
Here, M _A is the mass (g) of the aliphatic carboxylic acid or the like contained in 1 g of the coated metal particles, M _w is the molecular weight of the aliphatic carboxylic acid or the like, and N _A is the Avogadro constant. When two or more kinds of aliphatic carboxylic acids are contained, the number of molecules of each component is calculated and totaled.
The shape of the metal core particles is approximated to a sphere, and the mass of the metal core particles M _B (g) is obtained by subtracting the amount of the organic component from the mass of the coated metal particles. The number of metal core particles in 1 g of coated metal particles is represented by the following formula (b).
[Metal Number core _{particles] = M B / [(4πr} 3/3) × d × 10 -21] ··· (b)
Here, M _B is the mass (g) of the metal particles contained in 1 g of the coated metal particles, r is the radius (nm) of the primary particle diameter calculated by SEM image observation, and d is the metal density (g/ cm ³ ) (d=8.94 for copper). The surface area of the metal core particles contained in 1 g of the coated metal particles is expressed by the following expression (c) from the expression (b).
[Surface area of metal core particles (nm ² )]=[number of metal core particles]×4πr ² (c)
From the above, the coating density (molecules/nm ² ) of metal particles with an aliphatic carboxylic acid or the like is calculated by the following formula (d) using the formulas (a) and (c).
[Cover density]=[number of molecules of aliphatic carboxylic acid]/[surface area of metal core particles] (d)

The bonding state between the aliphatic carboxylic acid and the like and the metal core particles in the coated metal particles may be ionic bond or physical adsorption. The aliphatic carboxylic acid or the like is preferably physically adsorbed on the surface of the metal core particle from the viewpoint of the sinterability of the coated metal particle, and is physically adsorbed by a carboxy group or an aldehyde group on the surface of the metal core particle. Is preferred.

Physical adsorption of the aliphatic carboxylic acid or the like to the metal core particles can be confirmed by analyzing the surface composition of the coated metal particles. Specifically, the time-of-flight secondary ion mass spectrometry (ToF-SIMS) surface analysis is performed on the coated metal particles, and only substantially free aliphatic carboxylic acid or the like is detected and bound to the metal atom. This can be confirmed by the fact that aliphatic carboxylic acid and the like are not substantially detected. Here, when the aliphatic carboxylic acid or the like bonded to the metal atom is not substantially detected, the signal amount of the aliphatic carboxylic acid or the like attached to the metal core particles is It means 5% or less with respect to the signal amount, and preferably 1% or less.

In addition, the fact that the aliphatic carboxylic acid or the like is physically adsorbed on the surface of the metal particle with a carboxy group or an aldehyde group means that the infrared absorption spectrum of the coated metal particle is measured and the C-O-metal It can be confirmed that only the stretching vibration peak derived from the salt is observed, and the stretching vibration peak derived from the free carboxylic acid or the like is not substantially observed.

The particle size of the coated metal particles can be appropriately selected according to the application and the like. The average primary particle diameter of the coated metal particles is preferably 0.02 μm or more and 5 μm or less, more preferably 0.05 μm or more and 5 μm or less, from the viewpoint of dispersibility, conductivity, and crack suppression, It is even more preferable that it is from 07 μm to 2.5 μm.
The average primary particle diameter of the coated metal particles is calculated as an arithmetic mean value D _SEM of the primary particle diameters of arbitrary 20 coated metal particles obtained by SEM observation.
The value of the variation coefficient (standard deviation SD/average primary particle diameter D _SEM ) of the particle size distribution of the coated metal particles is, for example, 0.01 to 0.5, preferably 0.05 to 0.3. In particular, since the coated metal particles are manufactured by the method for manufacturing coated metal particles described below, the coefficient of variation of the particle size distribution is small and the particle diameters can be made uniform. Since the coefficient of variation of the particle size distribution of the coated metal particles is small, it is possible to obtain a highly concentrated dispersion having excellent dispersibility.

The coated metal particles used in this embodiment are excellent in oxidation resistance and sinterability, and the obtained sintered body exhibits high bonding strength and electrical conductivity. Therefore, it can be suitably used for a bonding composition that is printed on a base material to form a wiring pattern or the like.

The proportion of the coated metal particles contained in the bonding composition of the present embodiment is not particularly limited, but can be appropriately changed depending on the application. For example, in the case of screen printing, the ratio of the coated metal particles to the total amount of the bonding composition can be 5 to 95% by mass, and in the case of inkjet printing, the ratio of the coated metal particles to the total amount is 40 to 40%. It can be 90 mass %.

<Method for producing coated metal particles>
The coated metal particles used in the present embodiment use a metal carboxylate containing a metal to be the specific metal core particles and one or more kinds of molecules selected from the specific aliphatic carboxylic acid and aliphatic aldehyde. Manufactured. For example, it can be manufactured with reference to the descriptions of paragraphs 0052 to 0101 and paragraphs 0110 to 0114 of Patent Document 1 above. Alternatively, it can be produced by referring to paragraphs 0031 to 0066 and paragraph 0085 of JP-A-2016-069716.
In a preferred method for producing coated metal particles, a reaction solution containing a metal carboxylic acid salt, an aliphatic carboxylic acid, etc., and a medium is prepared, and a complex compound produced in the reaction solution is subjected to thermal decomposition treatment to obtain a metal nucleus. It is possible to obtain coated metal particles in which the surface of the particles is coated with an aliphatic carboxylic acid at a density of 2.5 to 5.2 molecules per 1 nm ² .

The carboxylic acid in the metal carboxylate can be appropriately selected from the viewpoint of the type of metal and the ease of manufacturing the metal carboxylate. Examples of the carboxylic acid used include formic acid, oxalic acid, citric acid and the like. Carbonic acid may be used instead of carboxylic acid depending on the type of metal. When copper is used as the metal, it is preferable to use copper formate as the metal carboxylate. When silver is used as the metal, silver formate, silver oxalate, silver carbonate, silver citrate, and the like can be used as the metal carboxylate. Among them, silver oxalate is used because of its high thermal decomposition temperature. It is preferable to use. The metal constituting the metal carboxylate can be the same as that of the metal core particles.

It is preferable that the reaction liquid contains an amino alcohol capable of forming a complex with a metal carboxylate. By forming a complex between the metal carboxylate and the amino alcohol, the solubility in the medium described later is improved.
The amino alcohol may be an alcohol compound having at least one amino group. The amino alcohol is preferably a monoamino monoalcohol compound, and more preferably an amino group-unsubstituted monoamino monoalcohol compound. It is also preferable that the amino alcohol is a monodentate monoamino monoalcohol compound. Specific examples of preferable amino alcohols include 2-aminoethanol, 3-amino-1-propanol, 5-amino-1-pentanol, DL-1-amino-2-propanol and N-methyldiethanolamine.

The medium constituting the reaction solution can be appropriately selected and used from those which do not inhibit the metal reduction of the metal carboxylate. The medium is usually an organic solvent. The medium has at least a main medium having low compatibility with amino alcohol, and may optionally have an auxiliary medium compatible with amino alcohol.

Examples of preferred main media include ethylcyclohexane, C9-based cyclohexane [manufactured by Maruzen Sekiyu, trade name: Swaclean #150], n-octane and the like. The medium may be used alone or in combination of two or more.
Examples of preferable auxiliary media include glycol ethers such as EO (ethylene oxide) type glycol ether, PO (propylene oxide) type glycol ether, and dialkyl glycol ether.
Each of the main medium and the auxiliary medium can be independently used alone or in combination of two or more.

The complex compound formed in the reaction solution preferably contains a metal ion and carboxylic acid and amino alcohol as ligands. The inclusion of amino alcohol as a ligand lowers the thermal decomposition temperature of the complex compound.
The complex compound produced in the reaction solution produces a metal reduced by the thermal decomposition treatment. The temperature of the thermal decomposition treatment may be appropriately adjusted in consideration of the thermal decomposition temperature of the complex compound coordinated with the amino alcohol as described above. By setting the temperature of the thermal decomposition treatment to be low, the formation of acid amide due to the dehydration reaction between the aliphatic carboxylic acid and the amino alcohol is suppressed, and the washability of the obtained coated metal particles tends to be improved.

A metal reduced by the thermal decomposition treatment of the complex compound grows and grows, and the aliphatic carboxylic acid or the like present in the reaction solution is adsorbed on the surface of the obtained metal core particles, so that A coated metal particle having a coated surface is obtained. The adsorption of the aliphatic carboxylic acid or the like on the surface of the metal core particles is preferably physical adsorption. This improves the sinterability of the coated metal particles. By suppressing the generation of metal oxides in the thermal decomposition treatment of the complex compound, physical adsorption of aliphatic carboxylic acid or the like is promoted.

In the method for producing coated metal particles, factors that control the particle size distribution of the produced coated metal particles include, for example, the type and addition amount of an aliphatic carboxylic acid, the concentration of metal carboxylate and the ratio of medium (main medium/ Auxiliary medium) etc. The factor controlling the size of the coated metal particles can be adjusted by appropriately maintaining the heating rate that controls the number of metal nuclei generated, that is, the stirring rate related to the amount of heat input to the reaction system and the size of the microreaction field. it can.

<Liquid paraffin>
The liquid paraffin used in this embodiment is a mixture of aliphatic hydrocarbons having a linear, branched, or cyclic structure, and is a liquid at room temperature. Since the surface of the coated metal particles is covered with a hydrophobic group, it has excellent compatibility with liquid paraffin. Therefore, the coated metal particles can be dispersed in the liquid paraffin in a stable state for a long time. In addition, since liquid paraffin is chemically stable, it is difficult to react with coated metal particles and metal powder. Therefore, the oxidation of the coated metal particles and the metal powder in the bonding composition is suppressed.
Liquid paraffin also exhibits good dispersibility in the metal powder.

Liquid paraffin is a mixture of aliphatic hydrocarbons having different molecular weights, and has a wide range of vaporization temperatures. That is, when the liquid paraffin in the present embodiment is heated, it begins to volatilize gradually after exceeding a certain temperature, and by further raising the temperature, almost all can be volatilized. The temperature at which the liquid paraffin begins to volatilize is preferably higher than room temperature and lower than the sintering temperature of the coated metal particles. The temperature at which all the liquid paraffin is volatilized is preferably higher than the sintering temperature of the coated metal particles. For example, liquid paraffin having a vaporizing temperature in the range of 50°C to 350°C can be used.
Under such conditions, when the bonding composition according to the present invention is heated, the liquid paraffin gradually vaporizes, so that the concentrations of the coated metal particles and the metal powder gradually increase. Therefore, it is possible to sinter the coated metal particles in a high density state and form a stronger joined body.

The density of the liquid paraffin is not particularly limited, but it is preferably 0.80 g/cm ³ or more at 15° C., more preferably 0.82 g/cm ³ or more, and 0.83 g/cm ³ or more. It is even more preferable. Liquid paraffin having the above density has a large molecular weight and tends to be hard to volatilize. Such liquid paraffin can remain without being dried even if it is left for a long time in a state of being coated on a substrate. Therefore, it is easy to handle in processes such as screen printing and can be suitably used as a material for conductive ink. The density of the liquid paraffin is preferably at 15 ℃ is 0.90 g / cm ³ or less, more preferably 0.88 g / cm ³ or less, further not less 0.87 g / cm ³ or less Is more preferable. Since the liquid paraffin having the above density tends to volatilize at a relatively low temperature, it tends to hardly remain in the sintered body. Therefore, the bonding composition using the liquid paraffin has a high bonding strength and can form a sintered body having high thermal conductivity and high electrical conductivity.

The kinematic viscosity of liquid paraffin is not particularly limited, but is preferably 4 mm ² /s or more at 37.8° C., more preferably 5 mm ² /s or more, and further preferably 10 mm ² /s or more. Is more preferable. In the liquid paraffin having the above-mentioned kinematic viscosity, the coated metal particles and the metal powder are hard to precipitate, so that the dispersibility tends to be good. The kinematic viscosity of the liquid paraffin at 37.8° C. is preferably 100 mm ² /s or less, more preferably 90 mm ² /s or less, and even more preferably 40 mm ² /s or less. Since the liquid paraffin having the above kinematic viscosity tends to volatilize at a relatively low temperature, it tends to hardly remain in the sintered body. Therefore, the bonding composition using the liquid paraffin has a high bonding strength and can form a sintered body having high thermal conductivity and high electrical conductivity.

Examples of liquid paraffin satisfying the above conditions include High Coal K (Kaneda Co., Ltd.) series liquid paraffin. Among them, it is preferable to use High Call K-160, High Call K-230, High Call K-290, High Call K-350 (all manufactured by Kaneda Corporation), and High Call K-230, High Call K-290 (all Kaneda Corporation). Is particularly preferable.

The type of liquid paraffin can be appropriately selected depending on the combination with the coated metal particles to be dispersed. For example, if the coated metal particles have a relatively long aliphatic hydrocarbon group and the coated metal particles have a relatively high sintering temperature, it is preferable to use liquid paraffin having a relatively high kinematic viscosity. When such liquid paraffin is used, the coated metal particles are sintered while being dispersed in the liquid paraffin, so that a more uniform and high-strength sintered body can be formed. On the other hand, when the coated metal particles have a relatively short aliphatic hydrocarbon group and the coated metal particles have a relatively short sintering temperature, liquid paraffin having a relatively short kinematic viscosity is preferably used. When such liquid paraffin is used, the liquid paraffin can be volatilized at a relatively low temperature, so that a sintered body can be formed more efficiently.

The content ratio of liquid paraffin with respect to the coated metal particles is not particularly limited, but is preferably 0.1% by mass or more, and more preferably 1% by mass or more. Under such conditions, the coated metal particles are well dispersed by the liquid paraffin. The content ratio of liquid paraffin to the coated metal particles is preferably 50% by mass or less, more preferably 30% by mass or less. Under such conditions, the concentration of the coated metal particles is sufficiently maintained, so that high bonding strength can be realized.

<Other ingredients>
The bonding composition according to the present invention contains the above-mentioned metal powder, coated metal particles, and liquid paraffin, and, if necessary, further other components as long as the effects of the present invention are not impaired. May be included. Examples of other components include a solvent, an antioxidant, a dispersant, a thickener, and a gelling agent. By combining a solvent, a dispersant, and a thickener, for example, the rheological properties of the bonding composition can be adjusted.

The viscosity of a mixture of liquid paraffin, a solvent, an antioxidant, a dispersant, a thickener, and a gelling agent may be appropriately adjusted according to the printing means. For example, the viscosity at 25° C. and 10 rpm can be appropriately adjusted within the range of 0.01 Pa·s or more and 500 Pa·s or less, and preferably 0.01 Pa·s or more and 50 Pa·s or less.

(solvent)
As the solvent that can be contained in the bonding composition according to the present embodiment, a solvent having high compatibility with the liquid paraffin is used. Examples of the solvent include hydrocarbon solvents, halogenated hydrocarbon solvents, aldehyde solvents, alcohol solvents, ether solvents, ester solvents, ketone solvents, amide solvents, carboxylic acid solvents, sulfonic acids. Examples thereof include organic solvents such as system solvents, and one or a mixture of two or more selected from these can be used.

In particular, among the above-mentioned solvents, it is preferable to use an aldehyde solvent having an aldehyde group. By including a reducing aldehyde solvent in the bonding composition, it is possible to suppress the oxidation of the coated metal particles due to oxygen and the like in the air and to further enhance the chemical stability of the coated metal particles. Among them, from the viewpoint of compatibility with liquid paraffin, it is more preferable to use a linear saturated aldehyde represented by the general formula of C _n H _2n+1 CHO (0≦n≦12), and decanal (C ₉ H ₁₉ CHO). Is more preferably used.

The proportion of the solvent contained in the bonding composition of the present embodiment is not particularly limited, but can be, for example, 1 to 95 mass %. When the solvent further contains an aldehyde solvent, the ratio of the aldehyde solvent is preferably 1% by mass or more, and more preferably 3% by mass or more, relative to 100% by mass of the solvent.

(Antioxidant)
The bonding composition according to the present embodiment may contain an antioxidant for the purpose of suppressing the oxidation of liquid paraffin. Examples of the antioxidant include phenolic antioxidants such as tocopherol and hydroquinones, phosphorus antioxidants, sulfur antioxidants, amine antioxidants, and the like, and are selected from these. It is preferable to use one kind or a mixture of two or more kinds thereof. Among them, from the viewpoint of compatibility with liquid paraffin, it is more preferable to use a phenolic antioxidant, and it is even more preferable to use tocopherol.

The proportion of the antioxidant contained in the bonding composition of the present embodiment is not particularly limited, but for example, it is preferably 0.0001 mass% to 20 mass% with respect to 100 mass% of liquid paraffin, The amount is more preferably 0005% by mass to 20% by mass, and even more preferably 0.0005% by mass to 10% by mass.

(Dispersant)
The bonding composition according to the present embodiment may contain a known dispersant such as a polyester dispersant or a polyacrylic acid dispersant. However, from the viewpoint of maintaining the bonding strength, the content of the dispersant contained in the bonding composition is preferably 0.3% by mass or less of the total amount, and more preferably 0.1% by mass or less of the total amount. Even more preferably, the dispersant is not substantially contained. The term "substantially free of dispersant" means, for example, that the dispersant content is 0.01% by mass or less based on the total amount, and preferably that it is below the detection limit in gel permeation chromatography measurement.

(Thickener/gelling agent)
The bonding composition according to the present embodiment may contain a known thickener such as a polymethacrylic acid thickener.
In addition, the bonding composition according to the present embodiment gels liquid paraffin for the purpose of improving the performance of retaining the pattern shape of the coating film before sintering (hereinafter, sometimes referred to as “pattern retention”). It may contain a gelling agent. Examples of the gelling agent include polyolefins such as polyethylene, polypropylene, polybutylene, polyisobutylene, and polymethylpentene, and it is preferable to use one kind or a mixture of two or more kinds selected from these, among which polyethylene is used. It is more preferable to use. The weight average molecular weight of the polyolefin is not particularly limited, but can be appropriately selected from, for example, 10,000 or more, and is preferably 10,000 to 5,000,000, and preferably 20,000 to 3,000. 1,000 is more preferable.

When the bonding composition contains a gelling agent, the mixture of liquid paraffin and the gelling agent preferably has thixotropy from the viewpoint of enhancing the pattern retention. The thixo ratio at 25° C. of the mixture of liquid paraffin and gelling agent is preferably 1.2 or more, more preferably 1.5 or more, and further preferably 2.0 or more.
The thixotropic ratio of the mixture of liquid paraffin and gelling agent is a ratio of viscosities measured at different rotation speeds by an E-type viscometer, and is calculated as (viscosity at 10 rpm)/(viscosity at 100 rpm).
Further, the mixing ratio of the liquid paraffin and the gelling agent may be appropriately adjusted within the range where desired physical properties are obtained. In the case where the bonding composition contains a gelling agent, from the viewpoint of improving the pattern retention, the gelling agent is 0.1% by weight based on 100% by mass of the liquid paraffin and the gelling agent contained in the bonding composition. It is preferably 5% by mass or more and 20% by mass or less, more preferably 1% by mass or more and 15% by mass or less, and even more preferably 1.5% by mass or more and 12% by mass or less.

[Use of the bonding composition]
Since the bonding composition of the present invention has the coated metal particles excellent in dispersibility and bonding strength, it can be used for bonding a plurality of objects to be bonded. Further, since the sintered body of the bonding composition of the present invention has excellent conductivity, it can be used, for example, for the purpose of electrically bonding a base material and an element. Furthermore, since the bonding composition of the present invention is non-volatile at room temperature, drying is suppressed even if it is left in a state of being coated on a substrate, for example. That is, the bonding composition of the present invention is easy to handle in a process such as screen printing and can be suitably used as a conductive ink.

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

<SEM image observation>
Measuring device: JEOL FE-EPMA JXA-8500F
Measurement conditions: acceleration voltage 15 to 20 kV
Observation magnification ×1,500 to ×30,000

<Calculation of average primary particle size and fluctuation rate>
Measuring device: JEOL FE-EPMA JXA-8500F
Average primary particle size: average value of 20 samples Variability: standard deviation of 20 samples/value calculated by average value

<Thermogravimetric/differential heat (TG-DTA) analysis>
Measuring device: Rigaku TG8120
Temperature rising rate: 10°C/min
Measurement temperature range: 25-500°C
Measurement atmosphere: Nitrogen (250 ml/min)

<Powder X-ray diffraction (XRD) analysis>
Measuring device: Rigaku Smartlab
Tube voltage: 45kV
Tube current: 200mA

[Production of Coated Copper Particles and Bonding Composition]
(Production Example 1) Production of coated metal particles Cu1 A 3000 mL glass four-necked flask equipped with a stirrer, a thermometer, a reflux cooling tube, and a nitrogen introduction tube was placed in an oil bath at 150°C.
In the flask, 484 g (3.1 mol) of copper formate anhydride, 98 g of caprylic acid (manufactured by Kanto Chemical Co., Inc.) (0.2 equivalent/copper formate anhydride), and tripropylene as a medium (auxiliary medium) 150 g (0.2 equivalents/copper anhydride) of glycol monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) and petroleum-based hydrocarbon (C9 alkylcyclohexane mixture) as a medium (main medium) (“Swaclean 150” manufactured by Gordo). )) 562 g (1.4 eq/copper formate anhydride) was charged. Under a nitrogen atmosphere, the contents in the flask were heated with an oil bath and mixed until the liquid temperature reached 50° C. with stirring.
712 g (3.0 equivalents/copper formic anhydride) of 3-amino-1-propanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was slowly added dropwise to the above mixture as a complexing agent. After the dropping was completed, the contents of the flask were heated in an oil bath and mixed while stirring until the liquid temperature reached around 120°C. As the liquid temperature increased, the reaction liquid changed from dark blue to dark brown, and carbon dioxide gas foamed. The reaction was terminated when the bubbling of carbon dioxide gas stopped, the oil bath temperature control was stopped, and the mixture was naturally cooled to room temperature.
1200 g of methanol (manufactured by Kanto Chemical Co., Inc.) was added to and mixed with the above reaction liquid cooled to room temperature. After leaving the obtained mixed liquid for 30 minutes or more, the supernatant was decanted to obtain a precipitate. To the precipitate, 1200 g of methanol (manufactured by Kanto Chemical Co., Inc.) and 390 g of acetone (manufactured by Kanto Chemical Co., Ltd.) were added and mixed. After leaving the obtained mixed liquid for 30 minutes or more, the supernatant was decanted to obtain a precipitate. These operations (addition of methanol and acetone and decantation) were repeated once more.
The obtained precipitate was transferred to a 500 mL eggplant flask using 400 g of methanol (manufactured by Kanto Chemical Co., Inc.). After allowing this to stand for 30 minutes or more, the supernatant was decanted.
To the obtained precipitate, 18 g of 3-hydroxy-2,2,4-trimethylpentyl isobutyrate was added and mixed. Then, the eggplant flask was placed in a rotary evaporator, and the contents were dried under reduced pressure (vacuum drying). After drying under reduced pressure (vacuum drying), the mixture was naturally cooled to room temperature, and then the inside of the eggplant flask was purged with nitrogen to release the reduced pressure. As described above, 200 g of brownish brown viscous coated copper particles Cu1 were obtained.

(Production Example 2) Production of coated metal particles Cu2 In Production Example 1, except that caprylic acid was changed to 68 g of lauric acid (manufactured by Kanto Chemical Co., Inc.) (0.1 equivalent to copper formate anhydride) In the same manner as in 1., 200 g of brownish brown viscous coated copper particles Cu2 were obtained.

(Production Example 3) Production of coated metal particles Ag1 A 300 mL glass eggplant flask equipped with a stirrer bar, a thermometer, and a reflux condenser was placed in an oil bath at 100°C.
In the flask, 30 g (0.1 mol) of silver oxalate anhydride, 6 g of undecanoic acid (manufactured by Kanto Chemical Co., Inc.) (0.3 equivalent/silver oxalate anhydride), and as a medium (auxiliary medium) Tripropylene glycol monomethyl ether (manufactured by Tokyo Chemical Industry Co., Ltd.) 10 g (0.5 equivalent/silver oxalate anhydride) and petroleum hydrocarbon (C9 alkylcyclohexane mixture) as a medium (main medium) (manufactured by Gordo Co., Ltd. (Swaclean 150") 54 g (4.3 equivalents/anhydrous silver oxalate) were charged. Under a nitrogen atmosphere, the contents in the flask were heated with an oil bath and mixed with stirring until the liquid temperature reached 50°C.
To the above mixture, 52 g (7.0 equivalents/silver oxalate anhydrous) of 3-amino-1-propanol (manufactured by Tokyo Chemical Industry Co., Ltd.) was slowly added dropwise as a complexing agent. After the completion of the dropping, the contents of the flask were heated in an oil bath and mixed while stirring until the liquid temperature reached around 85° C., and further heating and stirring at this temperature were continued. After 3 hours from the end of the dropping, the heating of the oil bath was stopped to end the reaction, and the reaction solution was naturally cooled to room temperature.
To the above reaction liquid cooled to room temperature, 160 g of methanol (manufactured by Kanto Chemical Co., Inc.) was added and mixed. After leaving the obtained mixed liquid for 30 minutes or more, the supernatant was decanted to obtain a precipitate. 80 g of methanol (manufactured by Kanto Chemical Co., Inc.) and 80 g of acetone (manufactured by Kanto Chemical Co., Ltd.) were added to and mixed with the above precipitate. After leaving the obtained mixed liquid for 30 minutes or more, the supernatant was decanted to obtain a precipitate. These operations (addition of methanol and acetone and decantation) were repeated once more.
To the obtained precipitate, 80 g of methanol (manufactured by Kanto Chemical Co., Inc.) and 1.7 g of 3-hydroxy-2,2,4-trimethylpentyl isobutyrate were added and mixed. This was placed in an eggplant-shaped flask, placed in a rotary evaporator, and the contents were dried under reduced pressure (vacuum drying). After drying under reduced pressure (vacuum drying), the mixture was naturally cooled to room temperature, and then the inside of the eggplant flask was purged with nitrogen to release the reduced pressure. As described above, 18 g of silver-colored coated silver particles Ag1 were obtained.

(Evaluation of coated metal particles)
The physical properties of the coated metal particles were evaluated by TG-DTA analysis, XRD analysis and SEM image observation.

(Example 1)
First, 0.8 parts by mass of liquid paraffin (High Coal K-230: manufactured by Kaneda Co., Ltd.) and 0.05 parts by mass of n-decanal (manufactured by Tokyo Kasei Co., Ltd.) were mixed, and a stirrer (Awatori Kentaro) was blended. (ARE-310): manufactured by Shinky Co., Ltd.) and stirred for 30 seconds at a rotation speed of 2000 rpm.
Next, 3 parts by mass of a metal powder (copper powder, 1050Y: manufactured by Mitsui Mining & Smelting Co., Ltd.) having an average particle diameter of 0.5 μm was mixed, and stirring was performed twice at a rotation speed of 2000 rpm for 30 seconds using the above stirrer. went.
Then, 5.4 parts by mass of the coated metal particles (the coated metal particles Cu1 obtained in Production Example 1) and 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (Kyowanol M:KH). 0.6 parts by mass (Neochem Co., Ltd.) was mixed, and stirring was performed three times at a rotation speed of 2000 rpm for 30 seconds using the above stirrer.
Then, a nylon mesh having a spread of 15 μm was placed on a container (160 ml of Nanko Black: manufactured by Kinki Kako Co., Ltd.), the stirred mixture was placed on the mesh, and then the mixture was stirred at a rotation speed of 2000 rpm for 15 minutes using the above stirrer. It was stirred for 2 seconds, and mesh filtration was performed. As described above, the bonding composition of Example 1 was obtained. The obtained bonding composition was excellent in dispersibility.

(Examples 2 to 6)
The bonding compositions of Examples 2 to 6 were obtained in the same manner as in Example 1 except that the components and blending amounts were changed as shown in Table 1 below. The obtained bonding composition was excellent in dispersibility.
In addition, the high coal K-160, the high coal K-230, the high coal K-290, and the high coal K-350 (all manufactured by Kaneda Co., Ltd.) in Table 1 are respectively 99.99995 mass% of liquid paraffin and 0.0005 of tocopherol. Mass% is included.
The density of High Coal K-160 is 0.832 to 0.845 g/cm ³ at 15°C, and the kinematic viscosity is 5.80 to 8.90 mm ² /s at 37.8°C. Further, the density of High Coal K-230 is 0.835 to 0.855 g/cm ³ at 15°C, and the kinematic viscosity is 11.7 to 15.7 mm ² /s at 37.8°C. Further, the density of High Coal K-290 is 0.850 to 0.865 g/cm ³ at 15°C, and the kinematic viscosity is 159.2 to 175 mm ² /s at 37.8°C. Further, the density of High Coal K-350 is 0.862 to 0.880 g/cm ³ at 15°C, and the kinematic viscosity is 340 to 410 mm ² /s at 37.8°C.

(Example 7)
In the same manner as in Example 1 except that 0.05 part by mass of tocopherol ( _DL -α-tocopherol: manufactured by Tokyo Kasei Co., Ltd.) was blended with 0.8 part by mass of liquid paraffin instead of 0.05 part by mass of n-decanal. Thus, the bonding composition of Example 7 was obtained. The obtained bonding composition was excellent in dispersibility.

(Example 8)
A bonding composition of Example 8 was obtained in the same manner as in Example 1 except that 0.05 part by mass of n-decanal was added and the mixture was not stirred. The obtained bonding composition was excellent in dispersibility.

(Example 9)
Example 1 was repeated except that 0.25 parts by mass of n-decyl alcohol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was mixed with 0.8 parts by mass of liquid paraffin instead of 0.05 parts by mass of n-decanar. Thus, the bonding composition of Example 8 was obtained. The obtained bonding composition was excellent in dispersibility.
The metal powder used in Example 9 is silver powder having an average particle diameter of 1 μm (SL01: manufactured by Mitsui Mining & Smelting Co., Ltd.).

(Comparative Examples 1-2)
The bonding compositions of Comparative Examples 1 and 2 were obtained in the same manner as in Example 1 except that the components and blending amounts in Example 1 were changed as shown in Table 1 below. Note that SC-0708A in Table 1 is a dispersant manufactured by NOF CORPORATION.

<Dispersibility evaluation>
The dispersibility of the bonding compositions of Examples 1 to 9 and Comparative Examples 1 and 2 was evaluated. The results are shown in Table 2. In Table 2, “○” indicates that the coated metal particles and the metal powder were dispersed even after standing for 30 minutes from the production, and “X” indicates that the coated metal particles and the metal powder precipitated after standing for 30 minutes from the production. Is shown as.

<Left stability evaluation>
A syringe (using a clear syringe of 3 cc and a plunger of 3 cc (yellow): all manufactured by Musashi Engineering Co., Ltd.) was filled with the bonding composition of each of Examples 1 to 9 and Comparative Example 1, and the needle (20 22G: manufactured by Musashi Engineering Co., Ltd., and an air dispenser (ML5000XII: manufactured by Musashi Engineering Co., Ltd.) on the Au-plated surface of a 5 mm×5 mm×500 μm silicon substrate (Ti/Ni/Au plating). 4 mg was applied.
Then, it was left at room temperature (temperature 22 to 25° C.), humidity 40 to 60%, and the atmosphere for 5 hours. Then, a 2 mm×2 mm×500 μm silicon chip (Ti/Ni/Au plating) was placed on the bonding composition that had been left for 5 hours so that the Au plating surface was in contact.
Table 2 shows the stability of the bonding composition at this time. When the silicon chip adhered to the bonding composition after being left for 5 hours, it was shown as “◯”, and when the bonding composition was dry and the silicon chip did not adhere, it is shown as “X”.

<Evaluation of bonding strength>
The bonding compositions of Examples 1 to 9 and Comparative Example 1 were each subjected to Au plating on a 5 mm×5 mm×500 μm silicon substrate (Ti/Ni/Au plating) using the syringe, needle, and air dispenser described above. 2-4 mg was applied on top. Then, a 2 mm×2 mm×500 μm silicon chip (Ti/Ni/Au plating) is placed on the bonding composition so that the Au plating surface is in contact, and the distance between the silicon substrate and the silicon chip is 50 μm. Crimped to.
After that, the silicon substrate and the silicon chip were heated at 100° C. for 60 minutes by using an electric furnace (KDF900GL: manufactured by Denken High Dental Co., Ltd.). Then, the temperature was further raised at a rate of 10° C./minute until the temperature reached a predetermined sintering temperature, and heating was performed at the sintering temperature for 60 minutes to obtain a sintered body.
The sintering temperature was 250° C. for the bonding compositions of Examples 1, 8, 9 and Comparative Example 1, and 350° C. for the bonding compositions of Examples 2-7. Note that nitrogen gas was continuously supplied at a flow rate of 5 L/min from the time when the heating of the coating film was started until the time when the inside of the electric furnace was cooled to 50°C.
Further, with respect to the bonding compositions of Examples 1 and 8, the coating films that had been left to stand at room temperature for 5 hours were fired in the same procedure to obtain sintered bodies.

The sintered bodies formed using the bonding compositions of Examples 1, 4, 6 to 8 and Comparative Example 1 were each subjected to a die shear test using a bond tester (Condor Sigma: manufactured by XYZTEC of the Netherlands) to perform bonding. The strength was measured. The results are shown in Table 3. In Table 3, when the bonding strength is sufficiently high, it is indicated as “◯”, when the bonding strength is sufficient, it is indicated as “Δ”, and when two substrates are not bonded and peeled, it is indicated as “x”. There is.

[Summary of results]
As shown in Table 2, from the results of the dispersibility evaluation, it was found that the bonding compositions of Examples 1 to 9 contained liquid paraffin and thus were excellent in dispersibility. On the other hand, it was found that the bonding composition of Comparative Example 2 containing neither liquid paraffin nor dispersant had dispersibility.

In addition, as shown in Table 2, it was found from the results of the above-described leaving stability evaluation that the bonding composition according to the present invention maintained fluidity even after being left for 5 hours and could be bonded to other members. It is considered that this is because the bonding composition according to the present invention contains non-volatile liquid paraffin.

Moreover, as shown in Table 3, it was found from the results of the bonding strength evaluation that the bonding compositions according to the present invention each exhibit sufficient bonding strength. This shows that the bonding composition according to the present invention was excellent in bonding strength while suppressing the amount of the dispersant used.
Among them, the joined bodies using the joining compositions (Examples 1 to 6) containing n-decanal which is an aldehyde solvent showed particularly high joining strength. It is considered that this is because the aldehyde solvent increased the chemical stability of the coated metal particles.

Further, among Examples 1 to 6, Examples (Examples 1, 3, 4, and 6) in which Hicor K-230 and Hicor K-290 were used as liquid paraffin were used (Examples 1, 3, 4, and 6). The joint strength was particularly high as compared with Examples 2 and 5). This is because the kinematic viscosities of High Coal K-230 and High Coal K-290 are both 10 mm ² /s or more and 40 mm ² /s or less at 37.8° C., and the coated metal particles and the metal powder can be well dispersed. It is considered that this is because it was formed, and it was difficult to remain in the sintered body by sintering at a relatively low temperature.

Further, as shown in Table 3, it was found that the bonding composition according to the present invention can form a bonded body excellent in bonding strength even after the coating film is left standing for 5 hours.

From the above results, one or more kinds of molecules selected from a plurality of aliphatic carboxylic acids and aliphatic aldehydes on the surface of the metal powder and the metal core particles having a particle diameter smaller than that of the metal powder are 2.5 to 5. The bonding composition of the present embodiment containing the coated metal particles coated at a density of 2 molecules/nm ² and the liquid paraffin has excellent dispersibility while suppressing the amount of the dispersant used, and also has good bonding strength. It was shown to be excellent.

Claims (4)

Metal powder,
The surface of metal core particles having a smaller particle size than the metal powder is coated with one or more kinds of molecules selected from a plurality of aliphatic carboxylic acids and aliphatic aldehydes at a density of 2.5 to 5.2 molecules/nm ^2. Coated metal particles,
Containing liquid paraffin,
Composition for bonding. Further contains an aldehyde solvent,
The bonding composition according to claim 1. The aldehyde solvent includes decanal,
The bonding composition according to claim 2. Further containing tocopherol,
The bonding composition according to claim 1.