JP6716809B2 - Method for producing copper paste composition - Google Patents

Description

The present invention relates to composite particles containing copper core particles, a copper paste composition and a method for producing the same, and a conductor produced using the copper paste composition.

In recent years, as a method of forming a pattern of a conductor such as wiring and a conductor layer, a printing method of directly pattern-printing a conductive paste composition containing a metal powder, a sintering agent and a medium instead of the photolithography method, which has many steps. Is attracting attention. Examples of the printing method include an inkjet printing method, a screen printing method, a flexo printing method, and a dispense printing method.

As the sintering agent for the conductive paste composition, metal particles having a smaller particle size than the metal powder are preferably used. The particle size of the metal particles for the sintering agent is preferably about 0.02 μm (20 nm) to 5.0 μm.
In the present specification, “particle size” means the primary particle size unless otherwise specified.

Conventionally, gold particles or silver particles are generally used as the metal particles for the sintering agent. However, gold particles are expensive. The silver particles have a problem of migration (“migration” here includes ion migration and electromigration), and corrosion by a sulfide gas or the like.

In recent years, copper particles have been studied as metal particles for a sintering agent because they have high conductivity, are less likely to cause migration problems, and have excellent corrosion resistance.
However, compared with gold and silver which are noble metals, copper is originally relatively easily oxidized and an oxide film tends to be easily formed on the surface.
Copper particles having a small particle size for the sintering agent have a large specific surface area per unit mass, and the proportion of the oxide film in each particle tends to increase.
In particular, when copper particles having a particle size of 200 nm or less are used, the activity of the particle surface is very high, and even when heated in an inert gas atmosphere such as nitrogen gas or in a vacuum atmosphere, a small amount of oxygen existing in the atmosphere Oxidation may progress, and sintering of the conductive paste composition may be hindered.
It is conceivable to perform reduction firing using hydrogen gas or the like at the final stage of heating and firing the conductive paste composition. However, when the ratio of the oxide film to each particle is large, the volume shrinkage at the time of reduction is large and the density is lowered after sintering.

The present inventors disclose, in Patent Document 1, a coated copper particle including a copper core particle and a coating layer containing a long-chain aliphatic amine as a main component, and a method for producing the same (claim 1, claim 1). 4 etc.). The coated copper particles have an excellent balance between oxidation resistance and sinterability (the effect of the invention, etc.).
The present inventors have also disclosed in Japanese Patent Application No. 2014-112794 (unpublished at the time of the present application) and Japanese Patent Application No. 2014-203242 (not published at the time of the present application) coated copper particles having excellent oxidation resistance and their production. I have applied for an invention relating to a method.

JP, 2014-001443, A

It is important that the conductive paste composition used in the printing method has good printing characteristics. Specifically, regardless of the coating conditions such as coating speed, the conductive paste composition should be coated with a uniform thickness in a state in which the metal powder and the metal particles as the sintering agent are uniformly dispersed. Is preferred. As a result, a uniform layer in which the metal powder and the metal particles as a sintering agent are most closely packed is formed after the medium is dried, and by sintering this, a high-density conductor can be formed.

Since the dispersibility of the metal particles as the metal powder and the sintering agent and the leveling property of the paste composition are improved, the conductive paste composition preferably has both viscosity and elasticity, that is, it is preferable that it has viscoelasticity. ..

The viscoelastic property can be evaluated by rheological measurement using a dynamic viscoelasticity measuring device. For example, a rheological measurement is performed to measure the change in complex viscosity, storage modulus, loss modulus, and loss coefficient (tan Δ, tan(delta)) with frequency. can do.
Of the above measurement items, the data of storage modulus shows the elastic characteristic with respect to frequency, and the loss modulus shows the viscous characteristic with respect to frequency.
Changes in frequency correspond to changes in temperature.The characteristics of the lower frequency side correspond to the characteristics of the higher temperature side, and the characteristics of the higher frequency side correspond to the characteristics of the lower temperature side. ing.

Since the dispersibility of the metal powder and the metal particles as the sintering agent and the leveling property of the paste composition are improved, the conductive paste composition has a storage modulus and a loss modulus with respect to frequency. (Loss modulus) behaves similarly, and it is preferable that the loss coefficients (tan Δ, tan(delta)) are substantially constant even if the frequency is changed. Further, it is preferable that the storage modulus always exceeds the loss modulus even if the frequency is changed.

Further, from the viewpoint of preventing liquid dripping during coating and uniform coating, the conductive paste composition has a relatively high viscosity in the state where shear stress is not applied, and the viscosity is relatively lowered by applying shear stress. It is preferable to have a property.
In the present specification, the term "dripping" means that when the conductive paste composition is printed in a predetermined pattern, the liquid on the shoulder of the printed portion drips to the outside of the original printing area. It means that the liquid spreads.

For example, by adding a high molecular polymer dispersant to the paste composition, the interparticle interaction between the metal powder and the metal particles can be enhanced, and the uniform dispersibility and leveling property can be improved.
For example, by adding a high-molecular polymer thickener to the paste composition, the viscosity of the paste composition can be increased in the state where no shear stress is applied, and thixotropy can be exhibited.

However, in manufacturing a device or the like that forms a conductor such as wiring or a conductor layer, the process temperature may be limited. In this case, the conductive paste composition needs to be sintered at a relatively low temperature, for example, 450°C or lower or 350°C or lower. Under such low temperature sintering conditions, the high molecular polymer added as the dispersant or the thickener may not be completely decomposed by heat and may remain in the conductor.

When the high molecular polymer remains in the conductor, the adhesion between the conductor and various base materials, various members, various layers, and the like may decrease. In addition, since the conductor may be cracked due to a volume change due to temperature change or water swelling, it is preferable that the total amount of the polymer added to the conductive paste composition is small, and the polymer is not added. Is more preferable.

The present invention has been made in view of the above problems, can be added as a sintering agent to the conductive paste composition, good oxidation resistance, printing characteristics and sinterability of the conductive paste composition. It is an object of the present invention to provide a composite particle containing copper core particles that can be improved.
Another object of the present invention is to provide a copper paste composition having good printing characteristics and sinterability and capable of forming a highly conductive conductor even at low temperature sintering, and a method for producing the same. Is.
In addition, in the present specification, the sintering temperature of “low temperature sintering” is defined as 450° C. or lower unless otherwise specified.

The composite particles of the present invention,
Copper nucleus particles,
A plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ² ,
It has a hydrophilic group and a hydrophobic group, and contains a plurality of polar organic low-molecular molecules that interact with the plurality of aliphatic carboxylic acid molecules.

The copper paste composition of the present invention,
Copper powder,
Copper core particles having a smaller particle size than the copper powder, and coated copper particles containing a plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ^2. When,
Having a hydrophilic group and a hydrophobic group, a plurality of polar organic small molecules that interact with the plurality of aliphatic carboxylic acid molecules of the coated copper particles,
The medium is included.

The method for producing the copper paste composition of the present invention,
A method for producing the copper paste composition of the present invention described above,
The copper core particles having a smaller particle size than the copper powder, and the plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ² A step (1) of preparing coated copper particles,
The copper powder, the coated copper particles, having a hydrophilic group and a hydrophobic group, the plurality of polar organic low molecules that interact with the plurality of aliphatic carboxylic acid molecules of the coated copper particles, and the medium. A step (2) of mixing a plurality of types of raw materials including
Step (1) includes a step of thermally decomposing the aliphatic carboxylic acid copper complex in a medium.

The conductor of the present invention is obtained by sintering the above copper paste composition of the present invention.
Examples of the conductor of the present invention include wiring and a conductor layer.

In the present specification, unless otherwise specified, “polar organic small molecule” is defined as a polar organic molecule having a hydrophobic group having 20 or less carbon atoms.

"Copper formate"
In the present specification, unless otherwise specified, "copper formate" is meant to include a hydrate and an anhydride.
In the present specification, "copper formate anhydrous" is defined as copper formate having a water content of 5% by mass or less.

"Water content and copper content of copper formate"
In the present specification, unless otherwise specified, the “water content and copper content of copper formate” shall be measured by thermogravimetric/differential thermal analysis (TG-DTA) analysis.
The measurement conditions are as follows.
Temperature rising rate: 10°C/min,
Measurement temperature range: 25-600°C
Measurement atmosphere: nitrogen (100 ml/min).

"Average primary particle diameter and particle diameter fluctuation rate of particles (copper core particles, coated copper particles, or composite particles)"
In the present specification, unless otherwise specified, the “average primary particle diameter of particles” is any 20 particles (copper core particles, coated copper particles, or composite particles) determined by scanning electron microscope (SEM) observation. ) Is the arithmetic mean value (DSEM) of the primary particle diameter.
The average primary particle diameter of the copper core particles and the average primary particle diameter of the coated copper particles or the composite particles containing the copper core particles can be regarded as substantially the same.
“Particle size variation rate” is the standard deviation (SD)/average primary particle size (DSEM) of the primary particle size of any 20 particles (copper core particles, coated copper particles, or composite particles) determined by SEM observation. ) Value.

"Amount of organic components in coated copper particles"
In the present specification, unless otherwise specified, the “amount of organic component of coated copper particles” is measured by thermogravimetric/differential thermal analysis (TG-DTA) analysis.
The measurement conditions are as follows.
Temperature rising rate: 10°C/min,
Measurement temperature range: 25-600°C
Measurement atmosphere: nitrogen (100 ml/min).
In the TG-DTA analysis, the weight loss due to heating is determined as the amount of organic components.

"Cover density of aliphatic carboxylic acid molecules"
In the present specification, unless otherwise stated, the “coating density of aliphatic carboxylic acid molecules” on the surface of copper core particles is calculated by the following method.

According to the method described in JP 2012-88242 A, liquid chromatography (LC) is used to extract the organic components adhering to the surfaces of the coated copper particles, and the components are analyzed.
As the measuring device, "ACQUITY UPLC H-Class System" manufactured by Waters is used. The measurement conditions are as follows.
Column: ACQUITY UPLC(R) BEH C18 1.7 μm 2.1×50 mm,
Measurement temperature: 50 ℃,
Measuring medium: water/acetonitrile,
Flow rate: 0.8 mL/min.

A sample for LC measurement is prepared as follows.
In a sample bottle, 1 g of coated copper particles and 9 mL of acetonitrile are placed. To this, 1 mL of 0.36 mass% hydrochloric acid aqueous solution is added. The contents are irradiated with ultrasonic waves for 30 minutes and mixed with stirring. Next, the resulting slurry liquid is allowed to stand to perform solid-liquid separation, and then the supernatant liquid is collected. The supernatant is filtered with a filter having a diameter of 0.2 μm to prepare a sample for LC measurement.

Thermogravimetric/differential heat (TG-DTA) is performed by the above method to measure the amount of organic components contained in the coated copper particles.
The molecular weight of the aliphatic carboxylic acid contained in the coated copper particles is calculated by combining the LC analysis result and the TG-DTA analysis result.

The average primary particle diameter of the copper nucleus particles is measured by the above method.

The number of aliphatic carboxylic acid molecules contained in 1 g of the coated copper core particles is represented by the following formula (a).
[Number of molecules of aliphatic carboxylic acid molecule]=Macid/(Mw/NA) (a)
Here, Macid is the molecular weight (g) of the aliphatic carboxylic acid contained in 1 g of the coated copper particles, Mw is the molecular weight (g/mol) of the aliphatic carboxylic acid molecule, and NA is the Avogadro constant.

The shape of the copper core particles is approximated to a spherical shape, and the amount of the organic component is subtracted from the mass of the coated copper particles to obtain the copper core particle amount MCu(g).
From the copper nucleus particle amount MCu (g), the number of copper nucleus particles in 1 g of the coated copper particles is represented by the following formula (b).
[Number of copper core particles in 1 g of coated copper particles]=MCu/[(4πr3/3)×d×10 ⁻²¹ ] (b)
Here, MCu is the amount (g) of copper core particles contained in 1 g of coated copper particles, r is the radius (nm) of the primary particle diameter of the copper core particles calculated by SEM image observation, and d is the density of copper. (D=8.94 (g/cm ³ )).

The surface area of the copper core particles contained in 1 g of the coated copper particles is expressed by the following expression (c) from the expression (b).
[Surface area (nm ² ) of copper core particles contained in 1 g of coated copper particles]=[number of copper core particles]×4πr ² (c)

The coating density (molecules/nm ² ) of the copper core particles with the aliphatic carboxylic acid molecule is calculated by the following formula (d) using the formulas (a) and (c).
[Coating density (molecule/nm ² )]=[number of molecules of aliphatic carboxylic acid molecule]/[copper core particle surface area] (d)

According to the present invention, copper can be added as a sintering agent to the conductive paste composition, has good oxidation resistance, and can improve the printing characteristics and sinterability of the conductive paste composition. Composite particles including core particles can be provided.
Further, according to the present invention, it is possible to provide a copper paste composition having good printing characteristics and sinterability and capable of forming a highly conductive conductor even at low temperature sintering, and a method for producing the same. ..

The schematic diagram of the copper paste composition of one embodiment which concerns on this invention is shown. The schematic diagram of the coated copper particle of one Embodiment which concerns on this invention is shown. 2 is a TG curve of the copper formate anhydride obtained in Production Example 1. 3 is an XRD pattern of the copper formate anhydride obtained in Production Example 1. It is a SEM photograph of the coated copper particles (CuP1) obtained in Production Example 2. It is a TG curve of the coated copper particles (CuP1) obtained in Production Example 2. 3 is a graph showing the measurement results of rheology of the copper paste composition obtained in Example 1. 5 is a graph showing the measurement results of rheology of the copper paste composition obtained in Comparative Example 1. 3 is a laser microscope surface photograph of the conductor layer obtained in Example 1. 7 is a graph showing the measurement results of rheology of the copper paste composition obtained in Comparative Example 2. It is a graph which shows the measurement result of the rheology of the copper paste composition obtained in Example 2-1. It is a graph which shows the measurement result of the rheology of the copper paste composition obtained in Example 2-2. FIG. 8 is a process chart showing the method for manufacturing the laminate according to the third embodiment. FIG. 8 is a process chart showing the method for manufacturing the laminate according to the third embodiment. 7 is a SEM cross-sectional photograph of the laminate obtained in Example 3.

Hereinafter, the present invention will be described in detail.

"Composite particles"
The composite particles of the present invention,
Copper nucleus particles,
A plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ² ,
It has a hydrophilic group and a hydrophobic group, and contains a plurality of polar organic low-molecular molecules that interact with the above-mentioned plurality of aliphatic carboxylic acid molecules.

The composite particles of the present invention can be used alone or in combination with other copper particles (copper powder) as copper particles in applications where copper particles are used.

The composite particles of the present invention can be used, for example, in combination with a copper powder having a particle size larger than that of the copper core particles. In this case, the composite particles of the present invention can be used as a sintering agent for copper powder.
When using the composite particles of the present invention as a sintering agent for copper powder having a larger particle size than the copper core particles, the mass ratio of the composite particles of the present invention and copper powder (composite particles of the present invention: copper powder) is particularly It is not limited and is preferably 20:80 to 80:20, more preferably 30:70 to 70:30, and particularly preferably 40:60 to 60:40.

"Copper paste composition"
The copper paste composition of the present invention,
Copper powder,
Copper core particles having a smaller particle size than the copper powder, and coated copper particles containing a plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ^2. When,
Having a hydrophilic group and a hydrophobic group, a plurality of polar organic small molecules that interact with a plurality of aliphatic carboxylic acid molecules of the coated copper particles,
The medium is included.

In the copper paste composition of the present invention, coated copper particles, and a plurality of polar organic small molecules that interact with a plurality of aliphatic carboxylic acid molecules of the coated copper particles form the above-described composite particles of the present invention. be able to.

FIG. 1A shows a schematic diagram of a copper paste composition according to an embodiment of the present invention.
FIG. 1B shows a schematic view of the composite particles of one embodiment according to the present invention.
In FIG. 1B, as shown in the lower right diagram, the “hydrophilic group” is schematically shown by a circle, and the hydrophobic group is schematically shown by a bar.

As shown in FIG. 1A, the copper paste composition 1 of the present embodiment includes copper powder 10, composite particles 20, and a medium (not shown).
In the figure, the shape, particle diameter, distribution and the like of each particle of the copper powder 10 and each particle of the composite particle 20 are schematic.

As the copper powder 10, a known copper powder for a conductive paste composition can be used.
As the copper powder 10, it is preferable to use a plurality of types of copper powder having different average primary particle diameters. By using multiple types of copper powder with different average primary particle diameters, copper powder with a relatively small average primary particle diameter enters the gap between copper powders with a relatively large average primary particle diameter, improving the packing density of the copper powder. Can be made.

In FIG. 1A, the copper powder 10 is illustrated as including a first copper powder 11 having a relatively large average primary particle diameter and a second copper powder 12 having a relatively small average primary particle diameter.
The average primary particle diameter of the first copper powder 11 having a relatively large average primary particle diameter is not particularly limited and is preferably 1 to 100 μm, more preferably 1 to 50 μm.
The average primary particle diameter of the second copper powder 12 having a relatively small average primary particle diameter is not particularly limited and is preferably 0.2 to 10 μm, more preferably 0.2 to 5 μm.

The copper paste composition 1 of the present embodiment includes composite particles 20 that act as a sintering agent.
As shown in FIG. 1B,
The composite particles 20 are
Copper core particles 21 having a smaller particle size than the copper powder 10,
A plurality of aliphatic carboxylic acid molecules 22 coating the surface of the copper core particles 21,
A plurality of polar organic small molecules 23 having a hydrophilic group and a hydrophobic group and interacting with a plurality of aliphatic carboxylic acid molecules 22.
In the figure, the size, number, distribution, and the like of the aliphatic carboxylic acid molecule 22 and the polar organic low molecule 23 are schematic.

In the figure, reference numeral 30 schematically shows the main chain and side chains of the high molecular polymer dispersant added as necessary.
As shown, the side chains of the polymer dispersant 30 may include hydrophilic groups and hydrophobic groups.
The high molecular polymer dispersant 30 is not particularly limited, and examples thereof include a polyester dispersant and a polyacrylic acid dispersant.

In the present embodiment, the plurality of aliphatic carboxylic acid molecules 22 are adsorbed on the surface of the copper core particles 21.
The mode of adsorption is not particularly limited, and examples thereof include physical adsorption and ion adsorption.
In one embodiment, the plurality of aliphatic carboxylic acid molecules 22 physically adsorb to the surface of the copper core particles 21 with a carboxyl group, which is a hydrophilic group, on the copper core particle 21 side to form an LB film (Langmuir-Blodgett film). Such a monolayer can be formed.

The physical adsorption of the aliphatic carboxylic acid molecule 22 on the surface of the copper core particle 21 can be confirmed by the surface composition analysis of the coated copper particle 20X.

For example, Tof-SIMS analysis (time-of-flight secondary ion mass spectrometry) can be performed on the coated copper particles 20X.
The physical adsorption of the aliphatic carboxylic acid molecule 22 on the surface of the copper core particle 21 means that in the Tof-SIMS spectrum, only the substantially free aliphatic carboxylic acid molecule is detected as the aliphatic carboxylic acid molecule, and 63Cu Alternatively, it can be confirmed by the fact that the aliphatic carboxylic acid molecule bonded to 65Cu is not substantially detected.

Here, "the aliphatic carboxylic acid molecule bound to 63Cu or 65Cu is not substantially detected" means that the detected amount of these is 5% or less with respect to the detected amount of the free aliphatic carboxylic acid molecule. Means there is. These detected amounts are preferably 1% or less based on the detected amounts of free aliphatic carboxylic acid molecules.

Infrared absorption analysis (IR analysis) can be performed on the coated copper particles 20X.
Physical adsorption of the aliphatic carboxylic acid molecule 22 on the surface of the copper core particle 21 means that substantially only the stretching vibration peak derived from the carboxylic acid-metal salt is observed in the infrared absorption spectrum (IR spectrum). This can be confirmed by the fact that the stretching vibration peak derived from the free carboxylic acid is not substantially observed.

The coated copper particles 20X in which the copper core particles 21 are coated with a plurality of aliphatic carboxylic acid molecules 22 have the aliphatic group (hydrophobic group) of the aliphatic carboxylic acid molecules 22 on the outermost surface.
The coated copper particles 20X having the above structure have excellent oxidation resistance.
In the medium, the hydrophobic groups of the coated copper particles 20X interact with each other to suppress the aggregation of the coated copper particles 20X. Therefore, the coated copper particles 20X having the above structure can exhibit good dispersibility.
As a result of studies by the present inventor, it was found that the copper paste composition including the copper powder 10, the coated copper particles 20X, and the medium is a viscous fluid having viscosity but low elasticity.

Since the composite particles 20 of the present embodiment have the basic structure of the coated copper particles 20X having the above structure, they are excellent in oxidation resistance.
In the composite particle 20 of the present embodiment, a plurality of polar organic low molecules 23 having a hydrophilic group and a hydrophobic group and interacting with the coated copper particles 20X are arranged around the coated copper particles 20X having the above structure. ..
As shown in the figure, it is considered that the aliphatic group which is the hydrophobic group of the aliphatic carboxylic acid molecule 22 and the hydrophobic group of the polar organic low molecule 23 interact with each other. In this case, the hydrophilic group of the polar organic low molecule 23 exists on the outermost surface of the composite particle 20 of the present embodiment. The hydrophilic group of the polar organic low molecule 23 and the hydrophilic group of the side chain of the polymer dispersant 30 can interact (hydrogen bond). Due to the interaction (hydrogen bond) between the polar organic low molecule 23 and the polymer dispersant 30, even if the amount of the polymer dispersant 30 added is reduced, the copper paste composition 1 exhibits good viscoelastic properties. It is thought that it can be done.
Further, the hydrophilic groups of the polar organic low molecule 23 can interact (hydrogen bond) with each other. It is considered that due to the interaction between the composite particles 20, the copper paste composition 1 can exhibit good viscoelastic properties without the addition of the polymer dispersant 30.
That is, in the copper paste composition 1 of the present embodiment, the addition amount of the high molecular polymer dispersant 30 can be set to 0 (zero) or an amount close thereto.

As described above, the amount of the high molecular polymer dispersant 30 added can be smaller than the amount of the high molecular polymer dispersant in a general conductive paste composition.
The content of the high molecular polymer dispersant 30 in the copper paste composition 1 of the present embodiment can be 1% by mass or less, and can also be 0% by mass.
The total content of the high molecular polymer including the high molecular polymer dispersant and the high molecular polymer thickener in the copper paste composition 1 of the present embodiment can be 1% by mass or less, and is 0% by mass. Is also possible.

Since the aliphatic carboxylic acid molecule 22 is simply adsorbed (physical adsorption, ion adsorption, etc.) to the copper core particle 21, it can be easily desorbed from the copper core particle 21 during sintering. Since the aliphatic carboxylic acid molecule 22 is an organic low molecule having a smaller number of carbon atoms than the high molecular weight polymer, it has a relatively low boiling point and is easily thermally decomposed even under low temperature sintering conditions of 450° C. or lower or 350° C. or lower. obtain.

Similarly, the polar organic small molecule 23 simply interacts with the aliphatic carboxylic acid molecule 22, and therefore can be easily desorbed from the aliphatic carboxylic acid molecule 22 during sintering. Since the polar organic low molecule 23 is an organic low molecule having a smaller number of carbon atoms than the high molecular weight polymer, it has a relatively low boiling point and can be easily thermally decomposed even under low temperature sintering conditions of, for example, 450° C. or lower or 350° C. or lower. ..

As described above, in the composite particle 20 of the present embodiment, the coating layer composed of the plurality of aliphatic carboxylic acid molecules 22 is formed on the surface of the copper core particle 21, and further, around the plurality of aliphatic carboxylic acid molecules 22. A plurality of polar organic low molecules 23 are arranged. In this embodiment, by adopting such a double coating structure, the particle dispersibility in the medium and the rheological properties of the paste composition are optimized without affecting the sinterability.

The copper paste composition 1 of the present embodiment including the composite particles 20 having the above structure has good particle dispersibility of the copper powder 10 and the composite particles 20 acting as a sintering agent. Moreover, since the copper paste composition 1 of the present embodiment has good viscoelastic properties, it also has good leveling properties.
When printing is performed using the copper paste composition 1 of the present embodiment, the copper paste composition 1 is dispersed in a state in which the copper powder 10 and the composite particles 20 are uniformly dispersed regardless of the coating conditions such as the coating speed. It can be applied with a uniform thickness. As a result, after the medium is dried, a uniform layer in which the copper powder 10 and the composite particles 20 are closest packed or close to that is formed, and by sintering this, a high-density conductor can be formed. ..

The above-described effects can be exhibited even when the addition amount of the polymer dispersant 30 is small, and can be exhibited without adding the polymer dispersant 30.
Generally, a high-molecular polymer may remain in the conductor without being completely thermally decomposed under low-temperature sintering conditions of, for example, 450° C. or lower or 350° C. or lower.
When the high molecular polymer remains in the conductor, the adhesion between the conductor and various base materials, various members, various layers, and the like may decrease. In addition, cracks may occur in the conductor due to changes in volume due to temperature changes or water swelling.
Therefore, it is preferable that the amount of the polymer added to the conductive paste composition is small, and it is more preferable not to add the polymer.
In the present embodiment, an organic residue is reduced, adhesion with various base materials, various members, various layers, and the like is good, and there is no crack, and a highly conductive conductor can be formed.

The copper paste composition 1 of the present embodiment can have a thixotropic property in which the viscosity is relatively high when no shear stress is applied, and the viscosity is relatively decreased when a shear stress is applied. Therefore, the copper paste composition 1 of the present embodiment has good uniform coatability, and when the copper paste composition is printed in a predetermined pattern, the liquid on the shoulders of the edges of the printed portion is It is also unlikely that the liquid will drip and spread outside the original printing area.

As described above, according to the present embodiment, it can be added as a sintering agent to a conductive paste composition such as a copper paste composition, has good oxidation resistance, and has printing characteristics of the conductive paste composition. With this, it is possible to provide the composite particles 20 including the copper nucleus particles, which can improve the sinterability.
In addition, according to the present embodiment, printing characteristics such as particle dispersibility, uniform coating property, leveling property, and liquid drop prevention property are good, sinterability is good, and low temperature of 450° C. or lower or 350° C. or lower. It is possible to provide the copper paste composition 1 capable of forming a highly conductive conductor even in sintering.

Hereinafter, each component of the copper paste composition excluding the copper powder will be described in detail.

(Copper core particles)
The average primary particle diameter of the copper nucleus particles is not particularly limited and may be in the range suitable as a sintering agent.
The average primary particle diameter of the copper nucleus particles is preferably 0.02 μm (20 nm) to 5.0 μm, more preferably 0.02 μm (20 nm) to 1.0 μm, and further preferably 0.02 μm (20 nm) to 0.5 μm. , Particularly preferably 0.02 μm (20 nm) to 0.2 μm.
If the average primary particle size is less than 0.02 μm (20 nm), it is difficult to produce particles, and if it exceeds 5.0 μm, the filling effect may be insufficient.

The purity of the copper core particles is not particularly limited, and a high conductivity is obtained, and thus a higher purity is preferable. The purity of the copper nucleus particles is preferably 95% by mass or more, more preferably 97% by mass or more.
The total content of copper oxides and copper hydroxides contained in the copper core particles is not particularly limited and is preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less.
In the present specification, unless otherwise specified, the “copper oxide” includes copper(II) oxide and cuprous oxide.

(Aliphatic carboxylic acid molecule)
The type of aliphatic carboxylic acid molecule that coats the surface of the copper core particles is not particularly limited.
The number of carboxy groups contained in the aliphatic carboxylic acid molecule is not particularly limited and is preferably 1 to 2, more preferably 1.
The aliphatic carboxylic acid molecule may be a saturated aliphatic carboxylic acid molecule or an unsaturated aliphatic carboxylic acid molecule.
When the aliphatic carboxylic acid molecule is an unsaturated aliphatic carboxylic acid molecule, the number of unsaturated bonds contained in the unsaturated aliphatic group is preferably 1 to 3, more preferably 1 to 2.
The aliphatic group contained in the aliphatic carboxylic acid molecule may be linear or branched, and is preferably linear.

The number of carbon atoms in the aliphatic group of the aliphatic carboxylic acid molecule can be increased by efficiently producing coated copper particles having a uniform particle size, and effectively exhibiting the effect of improving the oxidation resistance and particle dispersibility of the coated copper particles. , Preferably 5 or more.
Hereinafter, the aliphatic carboxylic acid having 5 or more carbon atoms in the aliphatic group is also referred to as “long-chain carboxylic acid”.

When the number of carbon atoms in the aliphatic group is 5 or more, the particle size variation rate of the coated copper particles tends to be small. Generally, the length of the carbon chain is highly correlated with the magnitude of the Van der Waals force that influences the association force. A carboxylic acid having a long carbon chain has a strong association force and can contribute to phase stabilization similar to Water-in-oil Emulsion which is a microreaction field in the production method described later. It is considered that this makes it possible to efficiently produce coated copper particles having a uniform particle size.

As the carbon number of the aliphatic group increases, the boiling point tends to increase, and the thermal decomposability during sintering tends to decrease.
Since the coated copper particles having a uniform particle size can be efficiently produced, the effect of improving the oxidation resistance and particle dispersibility of the coated copper particles is effectively expressed, and the thermal decomposability during sintering becomes good. The carbon number of the aliphatic group is more preferably 5 to 20, still more preferably 5 to 17, particularly preferably 7 to 17, and most preferably 9 to 17.

The boiling point of the aliphatic carboxylic acid molecule is preferably higher than the thermal decomposition temperature of the aliphatic carboxylic acid copper complex in the production method described later.
Specifically, the boiling point of the aliphatic carboxylic acid molecule is preferably 120°C or higher, more preferably 130°C or higher.
The boiling point of the aliphatic carboxylic acid molecule is preferably 400° C. or lower, because the thermal decomposability of the aliphatic carboxylic acid molecule during sintering becomes good.

As the aliphatic carboxylic acid molecule,
Unsaturated aliphatic carboxylic acid molecules such as oleic acid and linoleic acid;
and,
Included are saturated aliphatic carboxylic acid molecules such as stearic acid, heptadecanoic acid, lauric acid, and octanoic acid.
The aliphatic carboxylic acid molecule may be used alone or in combination of two or more.

Since the effect of improving the oxidation resistance and particle dispersibility of the coated copper particles is effectively exhibited, the coating density of the plurality of aliphatic carboxylic acid molecules on the surface of the copper core particles is 2.5 to 5.2 molecules/ nm ² , preferably 3.0 to 5.2 molecules/nm ² , and more preferably 3.5 to 5.2 molecules/nm ² .

(Polar organic small molecule)
The polar organic low molecule has a hydrophilic group and a hydrophobic group, and is not particularly limited as long as the aliphatic group of the aliphatic carboxylic acid molecule and the hydrophobic group of the polar organic low molecule interact well.

The hydrophilic group of the polar organic low molecule is one or more selected from the group consisting of amide group, hydroxyl group, carboxyl group, carbonyl group, thiol group, thiocarbonyl group, thioamide group, ether group, and amino group. It is preferable to include the group
As the hydrophilic group of the polar organic low molecule, one kind or two or more kinds can be used.
The polar organic small molecule may be the same or different aliphatic carboxylic acid molecule as the aliphatic carboxylic acid molecule in the coated copper particles.

The number of carbon atoms of the hydrophobic group of the polar organic low molecular weight molecule is preferably the same as or close to the number of carbon atoms of the aliphatic group of the aliphatic carboxylic acid molecule, since it can interact well with the aliphatic carboxylic acid molecule.
Specifically, the number of carbon atoms of the hydrophobic group of the polar organic low molecule is preferably 5 or more.
Similar to the number of carbon atoms in the aliphatic group of the aliphatic carboxylic acid molecule, the higher the number of carbon atoms in the hydrophobic group of the polar organic low molecule, the higher the boiling point and the lower the thermal decomposability during sintering.
The number of carbon atoms in the hydrophobic group of the polar organic low molecule is more preferably 5 to 20, and even more preferably, because it can interact well with the aliphatic carboxylic acid molecule and has good thermal decomposability during sintering. 5 to 17, particularly preferably 7 to 17, and most preferably 9 to 17.

Examples of polar organic small molecules are shown in [Chemical formula 1], [Chemical formula 2], and [Table 4].
[Chemical formula 1] and [Chemical formula 2] show the name, chemical structural formula, molecular weight, and chemical formula for each polar organic low molecule.
[Table 4] shows the name, molecular weight, decomposition vaporization temperature, and carbon number of the aliphatic group for each polar organic low molecule.
The polar organic low molecule can be used alone or in combination of two or more.

(Medium)
As the medium, a known medium used for general conductive paste compositions can be used.
Examples of the medium include hydrocarbon solvents, higher alcohol solvents, cellosolve, and cellosolve acetate solvents.
The medium may be used alone or in combination of two or more.
The solid content concentration of the copper paste composition is not particularly limited and is selected according to the printing method and is, for example, 10 to 99% by mass, preferably 40 to 95% by mass.

(Arbitrary ingredient)
The copper paste composition of the present invention may contain one or more optional components as required.

<Dispersant>
As described above, in the copper paste composition of the present invention, even without adding a dispersant, the particle dispersibility in the medium of the copper powder and the composite particles is good, the rheological properties of the copper paste composition is good. Good printing characteristics.
However, it is possible to add a dispersant. When the dispersant is added, the amount of the dispersant added can be reduced as compared with the conventional conductive paste composition.
As the dispersant, a known polymer dispersant such as a polyester dispersant and a polyacrylic acid dispersant can be used.
The dispersant may be used alone or in combination of two or more.

<Thickener>
The copper paste composition of the present invention may contain one or more thickeners, if necessary.
As the thickener, a known polymer thickener such as polymethacrylic acid thickener can be used.
The thickener may be used alone or in combination of two or more.

<Other optional ingredients>
Other optional components include coupling agents such as silane coupling agents and titanate coupling agents.

[Method for producing copper paste composition]
The copper paste composition of the present invention can be preferably produced by the following method for producing a copper paste composition of the present invention.

The method for producing the copper paste composition of the present invention,
Copper core particles (21) having a smaller particle size than the copper powder (10), and a plurality of aliphatic carboxylic acids adsorbed on the surface of the copper core particles (21) at a density of 2.5 to 5.2 molecules per 1 nm ^2. A step (1) of preparing coated copper particles (20X) containing molecules (22);
Copper powder (10), coated copper particles (20X), and a plurality of polar organic compounds having hydrophilic groups and hydrophobic groups and interacting with a plurality of aliphatic carboxylic acid molecules (22) of the coated copper particles (20X). It has a step (2) of mixing a plurality of kinds of raw materials including a molecule (23) and a medium (see FIGS. 1A and 1B for the reference numerals of the respective components).

(Process (1))
Step (1) preferably includes a step of thermally decomposing the aliphatic carboxylic acid copper complex in a medium.
By thermally decomposing an aliphatic carboxylic acid copper complex, copper nucleus particles and an aliphatic carboxylic acid are produced, and a plurality of aliphatic carboxylic acid molecules are adsorbed on the surface of one produced copper nucleus particle. (Physical adsorption or ion adsorption). Thereby, the coated copper particles (20X) in which a plurality of aliphatic carboxylic acid molecules are adsorbed (physical adsorption, ion adsorption, or the like) at a predetermined coating density on the surface of the copper core particles are formed.
Depending on the type of the aliphatic carboxylic acid in the aliphatic carboxylic acid copper complex and the like, in the thermal decomposition step of the aliphatic carboxylic acid copper complex, copper ions are reduced and reduced copper core particles are produced.

In one aspect,
Step (1) is
A step of preparing a reaction liquid containing copper carboxylate, an aliphatic carboxylic acid, and a medium,
The process of heating and reacting the said reaction liquid can be included.
In this method, formation and thermal decomposition of the aliphatic carboxylic acid copper complex occur in the heating reaction process of the reaction solution.

In the above aspect, the reaction liquid preferably further contains a complexing agent.

In the above aspect, it is preferable to heat and react the reaction solution under conditions without dehydration treatment.

That is,
Step (1) is
A step of preparing a reaction solution containing copper carboxylate, an aliphatic carboxylic acid, a complexing agent, and a medium,
It is preferable to include a step of heating and reacting the above reaction liquid under conditions without dehydration treatment .

Hereinafter, each component of the reaction liquid will be described.

<Copper carboxylate>
The raw material copper carboxylate is not particularly limited, and copper formate, copper oxalate, and the like are preferable from the viewpoints of copper ion reducibility, raw material availability, raw material production easiness, and the like.

Copper formate is composed of 1 mol of divalent copper ion and 2 mol of formate ion.
Copper formate may be anhydrous or hydrated, preferably anhydrous.

Copper formate may be a commercially available product or may be produced by a known method before use.
Since formic acid has a reducing property, when copper formate is thermally decomposed, divalent copper ions are reduced to produce reduced copper particles (see Japanese Patent Publication No. 61-19682).

The content of copper formate in the reaction solution is not particularly limited, and is preferably 1.0 to 2.5 mol/L, more preferably 1.5 to 2.5 mol/L, particularly preferably from the viewpoint of production efficiency and the like. It is 2.0 to 2.5 mol/L.

<Aliphatic carboxylic acid>
The raw material aliphatic carboxylic acid is not particularly limited and is selected according to the structure of the aliphatic carboxylic acid molecule in the desired coated copper particles.
The carbon number of the aliphatic carboxylic acid as a raw material is the same as the carbon number of the aliphatic group of the aliphatic carboxylic acid molecule in the desired coated copper particles.
The coated copper particles having a uniform particle diameter can be efficiently produced, and the effect of improving the oxidation resistance and the particle dispersibility of the coated copper particles is effectively expressed. Therefore, the carbon number of the aliphatic carboxylic acid as a raw material is preferably It is 5 or more.
Since the coated copper particles having a uniform particle size can be efficiently produced, the effect of improving the oxidation resistance and particle dispersibility of the coated copper particles is effectively expressed, and the thermal decomposability during sintering becomes good. The carbon number of the aliphatic carboxylic acid as a raw material is more preferably 5 to 20, still more preferably 5 to 17, particularly preferably 7 to 17, and most preferably 9 to 17.

The boiling point of the raw material aliphatic carboxylic acid is preferably higher than the heating temperature of the reaction liquid. Specifically, the boiling point of the aliphatic carboxylic acid molecule is preferably 120°C or higher, more preferably 130°C or higher.
Since the aliphatic carboxylic acid molecules in the coated copper particles have good thermal decomposability during sintering, the boiling point of the raw material aliphatic carboxylic acid molecules is preferably 400° C. or lower.

As the raw material aliphatic carboxylic acid,
Unsaturated aliphatic carboxylic acids such as oleic acid and linoleic acid;
and,
Included are saturated aliphatic carboxylic acids such as stearic acid, heptadecanoic acid, lauric acid, and octanoic acid.
The raw material aliphatic carboxylic acid may be used alone or in combination of two or more.

The content of the aliphatic carboxylic acid in the reaction solution is not particularly limited and is preferably 2.5 to 25 mol%, more preferably 5.0 to 15 mol%.
When the content of the aliphatic carboxylic acid in the reaction solution is 2.5 mol% or more, a sufficient reaction rate can be obtained and the productivity tends to be improved, and the particle diameter variation rate of the coated copper particles tends to be small. is there.
When the content of the aliphatic carboxylic acid in the reaction solution is 25 mol% or less, the increase in the viscosity of the reaction system is suppressed, and good stirring properties can be obtained.

<Complexing agent>
The complexing agent is not particularly limited, and amino alcohol or the like is preferable.
The presence of a complexing agent such as amino alcohol in the reaction solution effectively produces a complex compound from copper formate.
The complex compound is easily solubilized in the medium.

Amino alcohol is an alcohol compound having at least one amino group.
The number of amino groups is not particularly limited, and one is preferable.
That is, monoaminomonoalcohol is preferable as the aminoalcohol.
Among these, monoamino monoalcohols having an unsubstituted amino group and monodentate monoamino monoalcohols are preferable.

The boiling point of the amino alcohol is not particularly limited and is preferably higher than the heating temperature of the reaction liquid. Specifically, the boiling point of amino alcohol is preferably 120° C. or higher, more preferably 130° C. or higher.
The boiling point of the amino alcohol is preferably 400°C or lower, more preferably 300°C or lower.

Since the solubility in a medium and the boiling point are suitable for the reaction, the SP value of amino alcohol is preferably 11.0 or more, more preferably 12.0 or more, and particularly preferably 13.0 or more.
The SP value of amino alcohol is preferably 18.0 or less, more preferably 17.0 or less.

In the present specification, unless otherwise specified, the “SP value” is a solubility parameter according to Hildebrand's definition and is a square root of intermolecular binding energy E1 per 1 mL of a sample at 25° C.

In the present specification, the "SP value" is obtained according to the method described on the following website, unless otherwise specified.
Homepage of Japan Petroleum Institute
(http://sekiyu-gakkai.or.jp/jp/dictionary/petdicsolvent.html#solubility2)

The SP value is specifically calculated as follows.

The intermolecular bond energy E1 is a value obtained by subtracting gas energy from the latent heat of vaporization Hb.

From the boiling point Tb of the sample, the latent heat of vaporization Hb is calculated by the following formula.
Hb=21×(273+Tb)

From the latent heat of vaporization Hb, the molar latent heat of vaporization H25 at 25° C. is calculated by the following equation.
H25 = Hb x [1 + 0.175 x (Tb-25)/100]

From the molar heat of vaporization H25, the intermolecular bond energy E of the total amount of the sample is obtained by the following equation.
E = H25-596

From the intermolecular bond energy E of the total amount of the sample, the intermolecular bond energy E1 per 1 mL of the sample is obtained by the following formula.
E1=E×D/Mw
(In the above formula, D is the density of the sample, and Mw is the molecular weight of the sample.)

From the intermolecular binding energy E1 per 1 mL of the sample, the SP value is calculated by the following formula.
SP = (E1) ^1/2

For a sample containing an OH group, a correction of +1 is required for each OH group (see Mitsubishi Petroleum Engineering Co., No. 42, p3, p11 (1989)).

As amino alcohol,
2-aminoethanol (boiling point: 170° C., SP value: 14.54),
3-amino-1-propanol (boiling point: 187° C., SP value: 13.45),
5-amino-1-pentanol (boiling point: 245° C., SP value: 12.78),
DL-1-amino-2-propanol (boiling point: 160° C., SP value: 12.74),
and,
N-methyldiethanolamine (boiling point: 247° C., SP value: 13.26) and the like can be mentioned.
These may be used alone or in combination of two or more.

The content of amino alcohol in the reaction solution is not particularly limited, and is preferably 1.5 to 4.0 times mol, more preferably 1.5 to 3.0 times mol with respect to the copper ion in the reaction solution. is there.
When the content of the amino alcohol is 1.5 times or more the mole of copper ion, the solubility of copper formate becomes good and the reaction time can be shortened.
When the content of amino alcohol is 4.0 times or less mol of copper ions, unnecessary adhesion of amino alcohol to the generated coated copper particles can be suppressed.

<Medium>
The medium may be used alone or in combination of two or more.
As the medium, one kind or two or more kinds can be selected from the organic media generally used in the chemical reaction.

The medium is preferably a medium which does not inhibit the copper ion reduction reaction by formic acid and which satisfies a ΔSP value of 4.2 or more, which is the difference between the SP value of amino alcohol and the SP value of the medium.
When the ΔSP value is 4.2 or more, the width of the particle size distribution of the generated coated copper particles becomes narrow, and the coated copper particles having a uniform particle diameter tend to be obtained.

From the viewpoint of the reaction field formability and the quality of the coated copper particles, the ΔSP value is preferably 4.5 or more, more preferably 5.0 or more, and particularly preferably 7.0 or more.
The ΔSP value is preferably 11.0 or less, more preferably 10.0 or less.
The SP value of the medium is preferably smaller than that of amino alcohol.

When two or more types of media are used, the SP value of the media is defined by the average SP value in consideration of the SP value and the mole fraction of each medium contained in the media.
For example, when two types of media, medium 1 and medium 2, are used, the average SP value is calculated by the following formula.
δ3=(V1×δ1+V2×δ2)/(V1+V2)
(In the above formula, each symbol has the following meaning.
δ3: average SP value of mixed medium,
δ1: SP value of medium 1,
V1: molar volume of medium 1,
δ2: SP value of medium 2,
V2: molar volume of medium 2. )

The medium preferably includes at least a medium that is incompatible with amino alcohol (hereinafter, referred to as “main medium”).
As the medium, it is preferable to use a medium that is incompatible with amino alcohol (main medium) and a medium that is compatible with amino alcohol (hereinafter referred to as “auxiliary medium”) in combination.

Hereinafter, preferred embodiments of the main medium will be described.
The boiling point of the main medium is preferably higher than the heating temperature of the reaction liquid. Specifically, the boiling point of the main medium is preferably 120°C or higher, more preferably 130°C or higher.
The boiling point of the main medium is preferably 400°C or lower, more preferably 300°C or lower.

As the main medium, those capable of forming an azeotropic mixture with water are preferable. If an azeotropic mixture can be formed with water, water produced in the reaction system can be easily removed in the step of heating the reaction solution.

As the main medium, a mixture of ethylcyclohexane (boiling point: 132° C., SP value: 8.18) and C9 alkylcyclohexane [for example, “Swaclean 150” manufactured by Gordo Co. (boiling point: 149° C., SP value: 7.99)) , And n-octane (boiling point: 125° C., SP value: 7.54) and the like.
As the main medium, one type or two or more types can be used.

Hereinafter, preferred embodiments of the auxiliary medium used as necessary will be described.
The preferable boiling point of the auxiliary medium is the same as that of the main medium.
The SP value of the auxiliary medium is preferably larger than that of the main medium, and more preferably large enough to be compatible with the amino alcohol.

Examples of the auxiliary medium include ethylene glycol (EO) type glycol ether, propylene glycol (PO) type glycol ether, and dialkyl glycol ether.
Examples of the EO glycol ether include methyldiglycol, isopropyl glycol, butyl glycol and the like.
Examples of PO-based glycol ethers include methyl propylene diglycol, methyl propylene triglycol, propyl propylene glycol, and butyl propylene glycol.
Examples of the dialkyl glycol ether include dimethyldiglycol and the like.
All of these auxiliary media are available from Nippon Emulsifier Co., Ltd., etc.
The auxiliary medium may be used alone or in combination of two or more.

The amount of medium in the reaction solution is adjusted so that the copper ion concentration is preferably 1.0 to 2.5 mol/L, more preferably 1.5 to 2.5 mol/L.
When the copper ion concentration in the reaction solution is 1.0 mol/L or more, productivity is improved.
When the copper ion concentration in the reaction solution is 2.5 mol/L or less, increase in the viscosity of the reaction solution is suppressed, and good stirring property is obtained.

<Arbitrary ingredients>
The reaction liquid may contain one or more optional components other than those described above, if necessary.

<Complex compound>
In the reaction solution containing copper formate, an aliphatic carboxylic acid (preferably a long-chain carboxylic acid), and a medium, one or more complex compounds derived from copper formate (aliphatic carboxylic acid copper complex) are formed. To be done.
The structure of the complex compound is not particularly limited.
The structure of the complex compound in the reaction solution may change as the reaction progresses.

The complex compound can include copper ion and formate ion as a ligand.
When amino alcohol is used as the complexing agent, the complex compound can include copper ion, formate ion as a ligand, and amino alcohol as a ligand.
When the complex compound contains amino alcohol as a ligand, the thermal decomposition temperature of the complex compound tends to decrease.

As a complex compound,
Complex compound in which two formate ions and two molecules of amino alcohol are coordinated with one copper ion;
A complex compound in which one formate ion, one molecule of an aliphatic carboxylic acid, and two molecules of amino alcohol are coordinated with one copper ion,
A complex compound in which two formate ions and one molecule of amino alcohol are coordinated to one copper ion,
A complex compound in which one formate ion, one molecule of an aliphatic carboxylic acid and one molecule of an amino alcohol are each bidentate coordinated to one copper ion,
and,
A complex compound in which one molecule of amino alcohol is monodentately coordinated with respect to each of the above complex compounds may be mentioned.

The complex compound generated in the reaction solution can generate copper nucleus particles by thermal decomposition treatment. The temperature of the thermal decomposition treatment is appropriately selected according to the structure of the complex compound and the like.
Generally, the thermal decomposition temperature of copper formate is about 210 to 250°C.
However, by forming a complex compound with copper formate together with amino alcohol, the thermal decomposition temperature of copper formate can be lowered to about 110 to 120° C. (see JP 2008-013466 A).
Therefore, the heating temperature (thermal decomposition treatment temperature) of the reaction liquid using amino alcohol as the complexing agent is preferably 100 to 130°C, more preferably 110 to 130°C, and particularly preferably 115 to 125°C.

Amino alcohol is used as a complexing agent, and the thermal decomposition treatment temperature is preferably 100 to 130° C., more preferably 110 to 130° C., and particularly preferably 115 to 125° C. Further, the production of acid amide compound due to the dehydration reaction of aliphatic carboxylic acid and amino alcohol is suppressed, and coated copper particles having a low content of acid amide compound can be obtained. The acid amide content of the coated copper particles obtained by this method is, for example, 0.5% by mass or less, and usually 0% by mass.
The acid amide compound is one kind of polar organic low molecule.
By using the coated copper particles having a low content of the acid amide compound, or substantially not containing the acid amide compound, the amount of the polar organic low molecule in the finally produced copper paste composition is adjusted to a suitable range. Easy to control.

Copper core particles are generated by the thermal decomposition treatment of the complex compound, and the aliphatic carboxylic acid is adsorbed (physical adsorption or ion adsorption etc.) on the surface of the generated copper core particles, so that the surface of the copper core particles becomes Coated copper particles coated with a group carboxylic acid molecule can be obtained.

The time of the thermal decomposition treatment can be appropriately selected according to the temperature of the thermal decomposition treatment, and is preferably 30 to 180 minutes, for example.
From the viewpoint of preventing the oxidation of the copper core particles, the atmosphere for the thermal decomposition treatment is preferably an inert atmosphere such as a nitrogen atmosphere.

In the method for producing coated copper particles, the particle size distribution of the coated copper particles can be adjusted by adjusting the type and addition amount of the aliphatic carboxylic acid, the concentration of the copper formate complex, and the ratio of the mixed medium (main medium/auxiliary medium). , Can be adjusted to a narrow range.
The size of the coated copper particles can be made uniform by appropriately maintaining the temperature rising rate that governs 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 micro reaction field.

In the method for producing coated copper particles, coated copper particles having a narrow particle size distribution can be obtained. This can be considered as follows, for example.

The ΔSP value, which is the difference in SP value between the amino alcohol as a complexing agent for solubilizing copper formate in the reaction medium and the medium, is preferably 4.2 or more. In this case, the complex (copper formic acid amino alcohol complex or formic acid copper amino alcohol complex in which one molecule of formic acid is replaced with an aliphatic carboxylic acid) can be dissolved in the reaction solution, but the complex is thermally decomposed. When the complexing agent aminoalcohol is liberated, the liberated aminoalcohol is incompatible with the medium and begins to form two phases.
The liberated amino alcohol has a high affinity for copper formate and copper formate amino alcohol complex and can act as a new complexing agent or medium for copper formate. As a result, the released aminoalcohol forms a highly polar inner core (droplet), and the outside thereof is surrounded by a medium having a low polarity, so that a two-phase structure similar to Water in oil Emulsion is formed. It is presumed that this functions as a micro reaction field.

Water in the reaction system and formic acid desorbed by the substitution of the aliphatic carboxylic acid are also present in the micro reaction field.

In the micro reaction field,
Metal nuclei and their growing particles;
A copper formate amino alcohol complex which is a source of metal nuclei, or a formate copper amino alcohol complex in which one molecule of formic acid is substituted with an aliphatic carboxylic acid;
water;
And formic acid
It is considered that the reaction proceeds by being separated from the medium by the amino alcohol layer.

Hereinafter, the reaction mechanism will be described while showing the reaction formula by taking the case where the amino alcohol is propanolamine and the aliphatic carboxylic acid is lauric acid as an example.

In the initial stage of the reaction, it is considered that the thermal decomposition of the copper formate complex proceeds according to the following reaction formulas 1 to 4.

(Reaction formula 1)
(HCOO ⁻ )(HCOO ⁻ )Cu ²⁺ · (H ₂ NC ₃ H ₆ OH) ₂ +C ₁₁ H ₂₃ COOH
→(C ₁₁ H ₂₃ COO ⁻ )(HCOO ⁻ )Cu ²⁺ ·(H ₂ NC ₃ H ₆ OH) ₂ +HCOOH,

(Reaction formula 2)
_{^{(C 11 H 23 COO -)}} (HCOO -) Cu 2+ +2 (H 2 NC 3 H 6 OH) → (C 11 H 23 COO -) (HCOO -) Cu 2+ · (H 2 NC 3 H 6 OH) 2

(Reaction formula 3)
_{^{(C 11 H 23 COO -)}} (HCOO -) Cu 2+ · (H 2 NC 3 H 6 OH) 2 → Cu: C 11 H 23 COOH + 2H 2 NC 3 H 6 OH + CO 2

(Reaction formula 4)
Cu: C ₁₁ H ₂₃ COOH
↑↓
Cu+C ₁₁ H ₂₃ COOH

As the reaction progresses, the aliphatic carboxylic acid becomes a coating material for the copper core particles, and as the amount of the aliphatic carboxylic acid in the reaction solution decreases, the reaction of the following reaction formula 5 progresses and the generated gas component changes. it is conceivable that.

(Reaction formula 5)
(HCOO ⁻ )(HCOO ⁻ )Cu ²⁺ ·(H ₂ NC ₃ H ₆ OH) ₂
→ Cu+2H ₂ NC ₃ H ₆ OH+H ₂ +2CO ₂

In the micro reaction field, as shown in the following reaction formula 6, CuO is generated by hydrolysis of the copper formate aminoalcohol complex with water, but CuO is reduced via the reaction of reaction formula 7 or reaction formula 8. .. It is considered that this produces reduced copper particles that do not contain cuprous oxide and copper oxide. Moreover, since the number of copper atoms contained in the micro reaction field is limited, it is considered that the particle size of the copper core particles is controlled to be constant.

(Reaction formula 6)
(HCOO ⁻ )(HCOO ⁻ )Cu ²⁺ ·(H ₂ NC ₃ H ₆ OH) ₂ +H ₂ O
→CuO+2H ₂ NC ₃ H ₆ OH+2HCOOH

(Reaction formula 7)
2CuO+2HCOOH→Cu ₂ O+HCOOH+H ₂ O+CO ₂
→ 2Cu+2H ₂ O+2CO ₂

(Reaction formula 8)
CuO+2HCOOH→(HCOO ⁻ )(HCOO ⁻ )Cu ²⁺ +H ₂ O

Reaction formulas 1 to 8 are merely examples as described above, and change depending on the combination of amino alcohol and aliphatic carboxylic acid.

Since reduced copper particles having no copper oxide formed on the surface are generated in the micro reaction field, the aliphatic carboxylic acid existing in the micro reaction field is easily adsorbed. As a result, it is considered that the coated copper particles having a uniform particle size and excellent in oxidation resistance and sinterability can be efficiently obtained.

The method for producing the coated copper particles may further include post-processes such as a washing process, a separation process, and a drying process for the coated copper particles after the thermal decomposition treatment process.
Known methods can be applied to these subsequent steps.
The washing step can be performed using, for example, an organic medium. The organic medium used in the washing step is not particularly limited, and examples thereof include alcohol medium such as methanol and ketone medium such as acetone. These may be used alone or in combination of two or more.

[conductor]
The conductor of the present invention is obtained by sintering the above copper paste composition of the present invention.
The conductor is not particularly limited, and examples thereof include wiring and a conductor layer.
Examples of the conductor layer include an electrode layer and a bonding layer.
Examples of the bonding layer include a bonding layer that bonds a base material to a semiconductor element such as an IC (Integrated Circuit) chip.
Since the conductor of the present invention contains copper as a main component, it has high conductivity, is less likely to cause a migration problem, and is excellent in corrosion resistance.
The thickness of the conductor of the present invention is not particularly limited, and is preferably about 1 to 100 μm, for example.

The conductor of the present invention is
A step of applying the copper paste composition of the present invention on a substrate,
By a manufacturing method having a step of sintering the coated copper paste composition,
It can be manufactured.

The conductors of the present invention such as wiring and conductor layers can be formed on various base materials.
Since the copper paste composition of the present invention can be sintered at a relatively low temperature, it has a high degree of freedom in selecting a substrate.

The substrate includes at least the substrate body, and can optionally include one or more elements such as layers and members formed on the substrate body.
The base material body is, for example,
Resin such as polyimide;
Glass;
Ceramics such as silica and alumina;
Metals such as stainless steel, copper, and titanium;
Includes semiconductors such as silicon.
The base body may be made of a composite material.
In applications such as semiconductor components and electronic devices, a lead frame, a substrate and the like are preferably used as the base material main body. The thickness of the substrate is preferably about 0.01 to 5 mm.

The coating method is not particularly limited, and known printing methods such as an inkjet printing method, a screen printing method, a flexographic printing method, and a dispense printing method can be adopted.
The copper paste composition of the present invention can be pattern-printed by the above printing method.
Since the copper paste composition of the present invention has good printing characteristics, it is possible to perform pattern printing with a desired thickness and pattern with high accuracy.
The coating thickness is determined from the amount of medium and the desired thickness of the conductor finally manufactured.

The sintering temperature of the copper paste composition is, for example, 200 to 600°C, preferably 200 to 450°C.
The copper paste composition of the present invention can be sintered at a low temperature of 450°C or lower or 350°C or lower.

The sintering time is selected according to the sintering temperature and is, for example, 1 to 120 minutes, preferably 1 to 60 minutes.

In the sintering step, pressure sintering may be performed as necessary.
The applied pressure is not particularly limited and is preferably 0.1 to 100 MPa, more preferably 0.1 to 50 MPa.

From the viewpoint of preventing copper oxidation, the sintering atmosphere is preferably an inert atmosphere having a low oxygen concentration. Examples of the inert atmosphere having a low oxygen concentration include an inert gas atmosphere such as nitrogen and argon, and a reduced pressure atmosphere. The oxygen concentration in the atmosphere is preferably 1,000 ppm or less, more preferably 100 ppm or less, and particularly preferably 10 ppm or less.

Hereinafter, production examples, examples and comparative examples according to the present invention will be described.

[Production Example 1] "Production Example of Copper Formate Anhydride"
A 1000 mL four-neck glass flask was charged with 83 g of formic acid and 123 g of ion-exchanged water. While uniformly stirring the contents of the flask, 100 g of basic copper carbonate was added little by little. At this time, the generated carbon dioxide was guided to a water trap to confirm the state of carbon dioxide production.
After confirming that the outflow of carbon dioxide gas had almost disappeared, 160 g of ion-exchanged water was added and the reaction was continued at 43° C. for 4 hours.
After confirming that the reaction liquid became a deep blue transparent liquid and the outflow of carbon dioxide gas was completely stopped, the reaction was terminated.
120 g of water was distilled off by concentrating the contents of the flask under reduced pressure using an evaporator. As a result, a slurry containing precipitated crystals was obtained.
The slurry was naturally cooled to room temperature (20 to 25°C), filtered, and washed with 200 mL of acetone. As a result, greenish blue crystals were obtained.
Then, the obtained crystals were dried under reduced pressure (vacuum drying). The drying conditions under reduced pressure were a powder temperature of 50° C. or lower and a pressure of 7 kPa or lower.
As described above, 110 g of pale blue crystalline copper formate anhydride was obtained.

(analysis)
The obtained copper formate anhydride was analyzed as follows.

<Thermogravimetric/differential thermal analysis (TG-DTA) analysis>
Thermogravimetric/differential thermal analysis (TG-DTA) analysis was performed using "TG8120" manufactured by Rigaku Corporation as a measuring device.
The measurement conditions were as follows.
Temperature rising rate: 10°C/min,
Measurement temperature range: 25-600°C
Measurement atmosphere: nitrogen (100 ml/min).
The TG curve is shown in FIG.
The horizontal axis represents temperature (° C.), and the vertical axis represents the rate of increase or decrease in weight (% by weight) when the initial weight is 0% by weight.
A gradual weight loss was observed from room temperature to around 190°C. This gradual weight loss corresponds to the amount of evaporated water. The gradual weight loss rate was calculated as the water content of the anhydrous copper formate and found to be 0.9% by mass.
A large weight loss was observed between around 190°C and around 230°C. This large weight loss corresponds to formic acid evaporation. The weight loss rate after the measurement was 58.0% by weight.
It was 41.1 mass% when the copper content rate of the copper formate anhydride was calculated|required by the following formula.
[Copper content of anhydrous formate (mass %)]=100−[weight reduction rate (weight %) at the end of measurement]+[water content (mass %)]

<Powder X-ray diffraction (PXRD) analysis>
Powder X-ray diffraction (PXRD) analysis was carried out using "XRD-6100" manufactured by Shimadzu Corporation as a measuring device to identify the crystal structure.
The measurement conditions were as follows.
Target: Cu,
Tube voltage: 40KV,
Tube current: 30.0 mA.
The XRD pattern of anhydrous copper formate is shown in FIG.

[Production Example 2] "Production of coated copper particles (CuP1)"
A 3000 mL glass four-necked flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen inlet tube was placed in an oil bath at 150°C.
In the flask,
484 g (3.1 mol) of copper formate anhydride having a water content of 0.9 mass% obtained in Production Example 1,
Lauric acid (manufactured by Kanto Chemical Co., Inc.) 77.5 g (0.12 equivalent/copper formic acid anhydride),
Tripropylene glycol monomethyl ether (manufactured by Tokyo Kasei Co., boiling point: 242° C., SP value: 9.20) 188 g (0.29 equivalents/copper formate anhydride) as a medium (auxiliary medium),
Petroleum hydrocarbons (C9 alkylcyclohexane mixture) as a medium (main medium) (“Swaclean 150” manufactured by Gordo Co., boiling point: 149° C., SP value: 7.99) 702 g (1.78 equivalents/copper formate anhydride) ) And.
Under a nitrogen atmosphere, the contents in the flask were heated while being heated in an oil bath, and mixed while stirring at 200 rpm until the liquid temperature reached 50°C.

To the above mixture, 712 g (3.02 equivalent/copper formic anhydride) of 3-amino-1-propanol (manufactured by Tokyo Kasei) as a complexing agent was slowly added dropwise.
After completion of the dropping, the contents of the flask were heated in an oil bath and mixed at 340 rpm with stirring at a temperature rising rate of about 3.7° C./min until the liquid temperature reached around 120° C.
As the temperature of the liquid 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.

To the above reaction liquid cooled to room temperature, 550 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 liquid was decanted to obtain a precipitate.
To the above-mentioned precipitate, 550 g of methanol (manufactured by Kanto Chemical Co., Inc.) and 300 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 liquid 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 while co-washing with 550 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, 77 g of methylcyclohexane and 15 g of 3-hydroxy-2,2,4-trimethylpentyl isobutyrate were added and mixed. Then, the eggplant flask was placed in a rotary evaporator, and the contents were dried under reduced pressure (vacuum drying) under the conditions of 40° C. and 1 kPa or less.
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, 204 g of brown-colored coated copper particles (CuP1) were obtained.

The obtained coated copper particles (CuP1) were used for producing the copper paste compositions of Example 1 and Comparative Example 1 described below.
For the sample for evaluating the physical properties of the coated copper particles (CuP1), the operation of adding methylcyclohexane and 3-hydroxy-2,2,4-trimethylpentyl isobutyrate was omitted.

(analysis)
The following analysis was performed on the obtained coated copper particles (CuP1).

<SEM observation>
Scanning electron microscope (SEM) observation was performed on the obtained coated copper particles (CuP1).
As the SEM, “FE-EPMA JXA-8510F” manufactured by JEOL Ltd. was used.
The measurement conditions were as follows.
Accelerating voltage: 6KV or 15KV,
Observation magnification: 10,000 to 75,000 times.
The obtained SEM photograph is shown in FIG.
The average primary particle diameter was determined from SEM observation and found to be 90.4 nm.
The particle diameter variation rate was measured to be 9.6%, and coated copper particles (CuP1) having a uniform particle diameter were obtained.

<Powder X-ray diffraction (PXRD) analysis>
Powder X-ray diffraction (PXRD) analysis was performed on the coated copper particles (CuP1) obtained in Production Example 1.
As the measuring device, "XRD-6100" manufactured by Shimadzu Corporation was used.
The measurement conditions were as follows.
Target: Cu,
Tube voltage 40KV,
Tube current 30.0 mA.
In the obtained XRD pattern, a peak derived from reduced copper (2θ=43.3° or around) was detected, a peak derived from copper oxide (2θ=35.5° and 38.7°), and a cuprous oxide derived Peak (near 2θ=37.0°) was not detected. From this result, it was found that the coated copper particles (CuP1) obtained in Production Example 2 had the reduced copper particles as a nucleus and did not substantially contain an oxide.
Moreover, even if the coated copper particles (CuP1) were stored at room temperature (20 to 25° C.) for 12 months, a peak derived from copper oxide and a peak derived from cuprous oxide were not detected in the XRD pattern, and the coated copper particles ( CuP1) had good oxidation resistance.

<Tof-SIMS analysis (time-of-flight secondary ion mass spectrometry)>
The coated copper particles (CuP1) obtained in Production Example 2 were subjected to Tof-SIMS analysis (time-of-flight secondary ion mass spectrometry).
As the measuring device, "PHI TRIFT IV type" manufactured by ULVAC-PHI was used.
The measurement conditions were as follows.
Primary ion species: Au,
Accelerating voltage: 30 KV.
In the obtained Tof-SIMS spectrum, only free lauric acid was detected as the aliphatic carboxylic acid, and lauric acid bound to 63Cu or 65Cu was not detected. From this, it was confirmed that the physically adsorbed lauric acid was present on the surface of the coated copper particles (CuP1).

<Infrared absorption analysis (IR analysis)>
Infrared absorption analysis (IR analysis) was performed on the coated copper particles (CuP1) obtained in Production Example 2.
As the measuring device, “AutoIMAGE FT-IR Microscope” manufactured by Perkin Elmer was used.
In the obtained infrared absorption spectrum (IR spectrum), substantially only the stretching vibration peak derived from the carboxylic acid-metal salt was observed, and the stretching vibration peak derived from the free carboxylic acid was substantially not observed. .. From this, it was confirmed that the aliphatic carboxylic acid molecule (lauric acid molecule in this example) was physically adsorbed by the carboxy group on the surface of the copper core particle.

<Thermogravimetric/differential thermal analysis (TG-DTA) analysis>
The coated copper particles (CuP1) obtained in Production Example 2 were subjected to thermogravimetric/differential thermal analysis (TG-DTA) analysis to measure the amount of organic components.
As the measuring device, "TG8120" manufactured by Rigaku Corporation was used.
The measurement conditions were as follows.
Temperature rising rate: 10°C/min,
Measuring temperature range: 25°C to 600°C,
Measurement atmosphere: nitrogen (100 ml/min).

The TG curve is shown in FIG.
The horizontal axis represents temperature (° C.), and the vertical axis represents the rate of increase or decrease in weight (% by weight) when the initial weight is 0% by weight.
Since the measurement was performed in a slurry state, the weight loss rate up to about 150° C. corresponds to the solvent evaporation amount.
The weight reduction rate in the range of about 150° C. to 350° C. (near the boiling point of lauric acid) corresponds to the evaporation amount of the coating layer. The weight loss rate in this temperature range was 0.9% by mass. That is, the organic component amount of the coated copper particles (CuP1) obtained in Production Example 2 was 0.9% by mass.
In Production Example 2, the temperature of the thermal decomposition treatment of the reaction liquid was set to around 120° C. at which the acid amide dehydration condensation reaction was less likely to occur. No dehydration treatment was carried out during the thermal decomposition treatment of the reaction liquid. In this case, it is considered that the production of the acid amide compound by the dehydration condensation reaction between the aliphatic carboxylic acid and the amino alcohol was suppressed, and the coated copper particles (CuP1) substantially free of the acid amide compound were obtained.
From the TG-DTA measurement results and the production conditions, it is considered that the amount of the organic component of the coated copper particles (CuP1) obtained in Production Example 2 substantially corresponds to the amount of lauric acid.
Further, the TG-DTA measurement result also showed that lauric acid was physically adsorbed.

<Liquid chromatography (LC) analysis>
Liquid chromatography (LC) analysis was performed on the organic components contained in the coated copper particles (CuP1) obtained in Production Example 2.
As the measuring device, "ACQUITY UPLC H-Class System" manufactured by Waters was used.
The measurement conditions were as follows.
Column: ACQUITY UPLC(R) BEH C18 1.7 μm 2.1×50 mm,
Measurement temperature: 50 ℃,
Measuring medium: water/acetonitrile,
Flow rate: 0.8 mL/min.

Samples for LC analysis were prepared as follows.
1 g of coated copper particles and 9 mL of acetonitrile were placed in a sample bottle. 1 mL of 0.36 mass% hydrochloric acid aqueous solution was added there. Ultrasonic waves were applied to the obtained solution for 30 minutes with stirring and mixing. Next, the resulting slurry liquid was allowed to stand to perform solid-liquid separation, and then the supernatant liquid was collected. The supernatant was filtered with a 0.2 μm filter to prepare a sample for LC analysis.
In the LC analysis, lauric acid was mainly detected as an organic component.

<Measurement of coating density of aliphatic carboxylic acid>
The coating density of the aliphatic carboxylic acid coating the surface of the copper core particles was determined by the method described in the [Means for Solving the Problems] section and found to be 3.68 molecule/nm ² . ..
In "Chemistry and Education Vol. 40, No. 2 (1992) Obtaining Cross-sectional Area of Stearic Acid Molecule-Experimental Value and Calculated Value-", the minimum area is calculated from the van der waals radius of the stearic acid molecule, and the calculated value. The theoretical value of the saturated coating area calculated from is about 5.00 molecule/nm ² . From this theoretical value, it is estimated that the coated copper particles (CuP1) adsorb lauric acid on the surface of the copper core particles in a relatively high density. Due to this dense coating effect, the coated copper particles (CuP1) are considered to effectively exhibit oxidation resistance.

(Evaluation results)
Table 1 shows main manufacturing conditions and evaluation results in Manufacturing Example 2.

[Example 1]
A copper paste composition was produced using the coated copper particles (CuP1) obtained in Production Example 2.

As the first copper powder having a relatively large average particle diameter, a wet copper powder having an average particle diameter of 2.0 μm (“1200N” manufactured by Mitsui Kinzoku Co., Ltd.) was prepared.
As the second copper powder having a relatively small average particle diameter, a wet copper powder having an average particle diameter of 0.8 μm (“1050Y” manufactured by Mitsui Kinzoku Co., Ltd.) was prepared.
A polyacrylic acid-based dispersant (“Marialim” manufactured by NOF CORPORATION) was prepared as a high-molecular polymer dispersant.
A polymethacrylic acid-based thickener (“KC1100” manufactured by NOF CORPORATION) was prepared as a high-polymer thickener.
Lauric acid 3 propanolamide (C ₁₅ H ₃₁ NO ₂ ) which is an acid amide compound was prepared as a polar organic low molecule.
For the chemical structural formula and molecular weight of lauric acid 3-propanolamide, refer to [Chemical Formula 1] and [Table 4].
As a medium, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (“Kyowanol M” manufactured by NH Neochem) was prepared.

Coated copper particles (CuP1) obtained in Production Example 2, the first copper powder, the second copper powder, the polymer dispersant, and the polymer thickener. The above-mentioned polar organic low molecule and the above medium were blended in the composition shown in Table 2.
These were dispersed and kneaded using an automatic liquor device to obtain a copper paste composition.
The total amount of the high molecular weight polymer including the dispersant and the thickener was 0.5% by mass.
The amount of the high molecular polymer dispersant used was about 1/4 of the amount of the dispersant used in the general conductive paste composition.

[Comparative Example 1]
A copper paste composition having the composition shown in Table 2 was obtained in the same manner as in Example 1 except that the polar organic low molecule was not added.

(Evaluation)
<Rheology measurement>
Rheology measurements were performed on the copper paste compositions obtained in each of Example 1 and Comparative Example 1. Changes in complex viscosity, storage modulus G′, loss modulus G″, and loss coefficient (tan Δ, tan(delta)) with respect to frequency were measured.
Among the above measurement items, the data of storage modulus G′ shows the elastic characteristic with respect to frequency, and the loss modulus G″ shows the viscous characteristic with respect to frequency.
Changes in frequency correspond to changes in temperature.The characteristics of the lower frequency side correspond to the characteristics of the higher temperature side, and the characteristics of the higher frequency side correspond to the characteristics of the lower temperature side. ing.

As a measuring device, a dynamic viscoelasticity measuring device “ARES-G2” manufactured by TA Instruments Inc. was used.
The measurement conditions were as follows.
Measurement temperature: normal temperature (20-25°C),
Frequency: 1.0×10 ^{−1 to} 1.0×10 ² [rad/s].

<Laser microscope observation>
With respect to the copper paste composition obtained in Example 1, a conductor layer was formed using the obtained copper paste composition.
A 50 μm thick metal mask having square openings of 9 mm square was placed on a stainless (SUS) substrate, and then the copper paste composition was screen-printed.
Thus, a 50 μm-thick copper paste composition coating film having a square pattern of 9 mm square was formed in the opening of the metal mask.
Next, the coating film was dried under reduced pressure (vacuum heating drying) under the conditions of 150° C. and 1.0 Pa to obtain a conductor layer.
The surface of the obtained conductor layer was observed using a laser microscope.
As the laser microscope, "LEXT" manufactured by OLYMPUS was used.

(Evaluation results)
<Rheology evaluation results>
The measurement results of rheology of the copper paste compositions obtained in each of Example 1 and Comparative Example 1 are shown in FIGS. 6A and 6B.

In Example 1, an acid amide compound which is a polar organic low molecule was added to the copper paste composition.
As shown in FIG. 6A, in the copper paste composition obtained in Example 1, the storage modulus G′ and the loss modulus G″ behave similarly with respect to frequency. The loss coefficient (tan Δ, tan(delta)) was almost constant even when the frequency was changed. Moreover, even if the frequency was changed, the storage modulus G′ was always higher than the loss modulus G″.

In the copper paste composition obtained in Example 1, a plurality of aliphatic carboxylic acid molecules interact with each other around the coated copper particles (CuP1) in which the surfaces of the copper core particles are coated with the plurality of aliphatic carboxylic acid molecules. It is considered that composite particles in which a plurality of acid amide compound molecules (polar organic low molecule) are arranged were generated.
Hydrophilic groups of acid amide compound molecules (polar organic low molecule) are present on the outermost surface of the composite particles. It is considered that the hydrophilic group of the acid amide compound molecule (polar organic low molecule) and the hydrophilic group of the side chain of the polymer as a dispersant can interact (hydrogen bond). Due to the interaction (hydrogen bond) between the acid amide compound molecules (polar organic low molecule) and the high molecular polymer as the dispersant, the copper paste composition is good even if the addition amount of the high molecular polymer as the dispersant is reduced. It is considered that various viscoelastic properties can be exhibited.
It should be noted that the interaction (hydrogen bond) between the hydrophilic groups of the acid amide compound molecule (polar organic low molecule) also strengthens the interaction between the composite particles, so it is not necessary to add a polymer as a dispersant. However, it is considered that the copper paste composition can exhibit good viscoelastic properties.

In Comparative Example 1, no polar organic low molecule was added to the copper paste composition.
As shown in FIG. 6B, in the copper paste composition obtained in Comparative Example 1, the storage modulus G′ and the loss modulus G″ behave similarly with respect to frequency. The loss coefficient (tan Δ, tan(delta)) was almost constant even when the frequency was changed. However, unlike Example 1, when the frequency was changed, the storage modulus G′ was always lower than the loss modulus G″. With such viscoelastic properties, dripping is likely to occur during coating, and the leveling property tends to be poor.

<Results of laser microscope observation>
A laser microscope surface photograph of a conductor layer using the copper paste composition obtained in Example 1 is shown in FIG. 7.
As shown in FIG. 7, the copper paste composition obtained in Example 1 has good printing characteristics, good particle dispersibility of copper powder and composite particles, and good quality with no cracks or the like over the entire surface. It was possible to form a different conductor layer.

[Comparative example 2]
A copper paste composition was obtained in the same manner as in Example 1 except that the compounding composition was changed to that shown in Table 3. In this example, the addition of low polar organic molecules was not performed.

[Example 2-1]
A copper paste composition was obtained in the same manner as in Example 1 except that the compounding composition was changed to that shown in Table 3.

[Example 2-2]
A copper paste composition was obtained in the same manner as in Example 1 except that the compounding composition was changed to that shown in Table 3. In this example, lauric acid, which is an aliphatic carboxylic acid, was added as the polar organic low molecule instead of the acid amide compound.

(Evaluation)
<Rheology measurement>
With respect to the copper paste compositions obtained in Comparative Example 2 and Examples 2-1 and 2-2, rheology measurement was performed in the same manner as in Example 1. Changes in complex viscosity, storage modulus G′, loss modulus G″, and loss coefficient (tan Δ, tan(delta)) with respect to frequency were measured.

<Evaluation of presence or absence of dripping and leveling property>
In each of Comparative Example 2 and Examples 2-1 and 2-2, a conductor layer was formed using the obtained copper paste composition.
A 50 μm-thick metal mask having square openings of 9 mm square was placed on a stainless (SUS) substrate, and then the copper paste composition was screen-printed.
Thus, a 50 μm-thick copper paste composition coating film having a square pattern of 9 mm square was formed in the opening of the metal mask.
Next, the coating film was dried under reduced pressure (vacuum heating drying) under the conditions of 150° C. and 1.0 Pa to obtain a conductor layer.
Using a laser microscope "LEXT" manufactured by OLYMPUS, the luminance distribution on the surface of the obtained laminate (conductor layer/SUS substrate) was measured. In this measurement, the distribution of height and brightness is displayed as a color distribution. Therefore, when liquid drop of the copper paste composition occurs around the original conductive layer formation region (mask opening region), the exposed surface of the substrate, the liquid drop portion, and the conductive layer have different colors. It is displayed and the presence or absence of dripping can be evaluated.
In each of Examples 2-1 and 2-2, as the evaluation of the leveling property, a surface roughness (arithmetic mean roughness Ra) of the obtained conductor layer was obtained by using a laser microscope “LEXT” manufactured by OLYMPUS. Was measured.

(Evaluation results)
<Rheology evaluation results>
The measurement results of rheology of the copper paste compositions obtained in Comparative Example 2 and Examples 2-1 and 2-2 are shown in FIGS. 8A to 8C.

In Comparative Example 2, no polar organic low molecule was added to the copper paste composition.
As shown in FIG. 8A, in the copper paste composition obtained in Comparative Example 2, the storage modulus G′ and the loss modulus G″ behave similarly to frequency. The loss coefficient (tan Δ, tan(delta)) was almost constant even when the frequency was changed. However, when the frequency was changed, the storage modulus G′ was always lower than the loss modulus G″.
The copper paste composition obtained in Comparative Example 2 had poor printing characteristics as in Comparative Example 1.

In Example 2-1, the acid amide compound which is a polar organic low molecule was added to the copper paste composition.
As shown in FIG. 8B, in the copper paste composition obtained in Example 2-1, the storage modulus G′ and the loss modulus G″ are similar with respect to frequency. The loss coefficient (tan Δ, tan(delta)) did not change significantly even when the frequency was changed. Moreover, even if the frequency was changed, the storage modulus G′ was always higher than the loss modulus G″.
The copper paste composition obtained in Example 2-1 had good printing characteristics as in Example 1.

In Example 2-2, an aliphatic carboxylic acid, which is a copper paste composition polar organic low molecule, was added.
As shown in FIG. 8C, in the copper paste composition obtained in Example 2-2, the storage modulus G′ and the loss modulus G″ are similar with respect to frequency. The loss coefficient (tan Δ, tan(delta)) did not change significantly even when the frequency was changed. Moreover, even if the frequency was changed, the storage modulus G′ was always higher than the loss modulus G″.
The copper paste composition obtained in Example 2-2 had good printing characteristics as in Example 1.

<Evaluation result of presence or absence of dripping and leveling property>
The copper paste composition obtained in Comparative Example 2 in which the polar organic low molecule was not added had poor printability. Therefore, when applied on the SUS substrate, liquid dripping was observed.

The copper paste composition obtained in Example 2-1 to which the acid amide compound having a low polar organic molecule was added had good printability. Therefore, no liquid dripping was observed when it was coated on the SUS substrate.
Moreover, since the copper paste composition had good leveling properties, the obtained conductor layer had a surface roughness (arithmetic mean roughness Ra) of 2.5 μm and a good surface smoothness.

The printability of the copper paste composition obtained in Example 2-2 to which an aliphatic carboxylic acid having a low polar organic molecule was added was good. Therefore, no liquid dripping was observed when it was coated on the SUS substrate.
Moreover, since the copper paste composition had good leveling properties, the obtained conductor layer had a surface roughness (arithmetic mean roughness Ra) of 3.0 μm and a good surface smoothness.

[Example 3] "Formation of bonding layer"
As a base material, a copper lead frame (silver plated lead frame) having a silver plated surface was prepared.
By a screen printing method using a mask, the copper paste composition obtained in Example 1 was applied in a thickness of 50 μm in a square pattern of 9 mm square on the chip mounting portion (square shape of 9 mm square in plan view) of the lead frame. I worked.
Separately, an IC (Integrated Circuit) chip having a silicon wafer as a substrate and silver-plated as a barrier layer on the surface was prepared.

Chip bonding was carried out using a chip bonding apparatus equipped with a hot stage and a bonding head that is arranged opposite to this hot stage and that holds an IC chip by suction.

As shown in FIG. 9A, in a state where the hot stage and the bonding head are sufficiently separated from each other, the above-mentioned silver-plated lead frame coated with the copper paste composition is placed on the hot stage, and the lower surface of the bonding head is mounted. The silver-plated IC chip was adsorbed and held.

Next, as shown in FIG. 9B, the bonding head was lowered, and the coating film of the copper paste composition was pressure-sintered to form a copper bonding layer (bonding conductor layer).
The pressure sintering conditions were as follows.
Sintering temperature: 350°C,
Pressure: 30MPa,
Heating and pressurizing time: 10 minutes.
As described above, a laminate composed of IC chip/barrier layer (silver plating layer)/copper bonding layer/silver plating layer/lead frame was obtained.

9A and 9B are schematic cross-sectional views.
Each symbol in these figures indicates the following components.
100: Chip bonding device,
101: Hot stage,
102: bonding head,
201: lead frame,
202: silver-plated layer,
203X: coating film,
203: copper bonding layer,
204: barrier layer (silver plating layer),
205: IC chip,
200: laminated body.

The SEM cross-section of the obtained laminate was observed.
A SEM cross-sectional photograph is shown in FIG.
As shown in FIG. 10, the copper bonding layer of the obtained laminated body was a dense and highly uniform conductor layer.

[Example 4] "Formation of conductor layer"
The copper paste composition obtained in Example 1 was applied in a square pattern of 9 mm square to a thickness of 10 μm on a polyimide film having a thickness of 40 μm having a copper foil of 12 μm laminated on the back side.
Next, the coating film was heated in a nitrogen atmosphere at 350° C. for 1 hour to obtain a conductor layer.
When the volume resistivity value of the obtained conductor layer was measured, it was 5 μΩ·cm, and the conductor layer had the same high conductivity as the Cu bulk body.

1: Copper paste composition 10: Copper powder 11: First copper powder 12: Second copper powder 20: Composite particle 20X: Coated copper particle 21: Copper core particle 22: Aliphatic carboxylic acid molecule 23: Polar organic low Molecule 30: Polymer dispersant 100: Chip bonding device 101: Hot stage 102: Bonding head 201: Lead frame 202: Silver plating layer 203X: Coating film 203: Copper bonding layer (conductor layer)
204: Barrier layer (silver plating layer)
205: IC chip 200: laminated body

Claims (7)

Including copper powder, a sintering agent, and a medium,
The sintering agent is copper core particles having a smaller particle size than the copper powder, and a plurality of aliphatic carboxylic acids adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ^2. Copper paste composition which is a composite particle containing a coated copper particle containing a molecule, a hydrophilic group and a hydrophobic group, and a plurality of polar organic low-molecular molecules that interact with the plurality of aliphatic carboxylic acid molecules of the coated copper particle. A method of manufacturing a product,
The copper core particles having a smaller particle size than the copper powder, and the plurality of aliphatic carboxylic acid molecules adsorbed on the surface of the copper core particles at a density of 2.5 to 5.2 molecules per 1 nm ² A step (1) of preparing coated copper particles,
The copper powder, the coated copper particles, having a hydrophilic group and a hydrophobic group, the plurality of polar organic low molecules that interact with the plurality of aliphatic carboxylic acid molecules of the coated copper particles, and the medium. A step (2) of mixing a plurality of types of raw materials including
Step (1) includes a step of thermally decomposing the aliphatic carboxylic acid copper complex in a medium,
A method for producing a copper paste composition. Step (1) is
A step of preparing a reaction liquid containing copper carboxylate, a fatty acid, and a medium,
A step of heating the reaction solution to react.
The method for producing the copper paste composition according to claim 1 . The average primary particle diameter of the copper nucleus particles is in the range of 0.02 to 5.0 μm,
The copper powder includes a first copper powder having a relatively large average primary particle diameter and a second copper powder having a relatively small average primary particle diameter,
The average primary particle diameter of the first copper powder is in the range of 1 to 100 μm,
The average primary particle diameter of the second copper powder is in the range of 0.2 to 10 μm, and smaller than the average primary particle diameter of the first copper powder,
A method for producing the copper paste composition according to claim 1 . The total content of the high molecular weight polymer in the copper paste composition is 1 mass% or less,
The manufacturing method of the copper paste composition in any one of Claims 1-3 . The aliphatic group of the aliphatic carboxylic acid molecule has 5 to 20 carbon atoms,
The hydrophobic group of the polar organic small molecule has 5 to 20 carbon atoms,
The manufacturing method of the copper paste composition in any one of Claims 1-4 . The hydrophilic group of the polar organic low molecule is one or two selected from the group consisting of an amide group, a hydroxyl group, a carboxyl group, a carbonyl group, a thiol group, a thiocarbonyl group, a thioamide group, an ether group, and an amino group. Containing more than one group,
A method for producing the copper paste composition according to claim 1 . The total content of copper oxides and copper hydroxides in the copper paste composition is 5% by mass or less,
The manufacturing method of the copper paste composition in any one of Claims 1-6 .