JP6870436B2 - Metal particle agglomerates and methods for producing them, paste-like metal particle compositions and methods for producing conjugates - Google Patents

Description

The present invention relates to metal particle agglomerates and a method for producing the same. The present invention also relates to a paste-like metal particle composition containing the above-mentioned metal particle aggregate and a method for producing a bonded body using the paste-like metal particle composition.

When joining two or more parts in the assembly or mounting of electronic parts, a joining material is generally used. As such a bonding material, a paste-like bonding material in which metal particles having high thermal conductivity such as silver and gold are dispersed in a volatile solvent is known. When joining parts using a joining material, the joining material is applied to the surface of one part, the other part is brought into contact with the coated surface, and heat treatment is performed in this state. Parts can be joined by sintering metal particles to form a bonding layer by this heat treatment.

As the bonding material, those using metal particles having a particle size of submicron size (Patent Documents 1 and 2) and those using agglomerates of metal particles having a particle size of nanometer size (Patent Documents 3 and 2). 4) is known. Patent Document 1 discloses a bonding material using spherical silver particles having an average particle size of 0.1 to 6 μm. Patent Document 2 discloses a bonding material using non-spherical silver particles having an average particle size of 0.1 to 18 μm. Patent Document 3 discloses a bonding material using agglomerates having a particle size of 10 nm or more and 100 μm or less, which are formed by agglomerating metal particles having an average particle size of 1 nm or more and 100 nm or less whose surface is coated with an organic substance. ing. Patent Document 4 discloses a bonding material containing metal nanoparticles having a number average particle size of 50 nm or less and a particle size of 100 to 200 nm, a coagulation aid, and a polymer dispersant.

International Publication No. 2006/126614 International Publication No. 2007/034833 Japanese Unexamined Patent Publication No. 2008-161907 Japanese Unexamined Patent Publication No. 2011-94223

With the recent miniaturization and high integration of electronic devices, the amount of heat generated by electronic components such as semiconductor chips and LED elements tends to increase. Therefore, the bonding material used for bonding electronic components is required to be capable of bonding electronic components with high bonding strength and long-term reliability.
However, a bonding material using submicron-sized metal particles tends to have a lower bonding strength than a bonding material using an aggregate in which nano-sized metal particles are aggregated. The reason for this is that the submicron size metal particles have a larger gap between the metal particles than the nano size metal particles, so that the bonding material formed by firing the bonding material using the submicron size metal particles is formed. It is considered that this is because fine voids (voids) are likely to be generated in the layer. As a method of suppressing the generation of voids, there is a method of pressurizing a member such as an electronic component to be joined at the time of joining, but in this case, a pressurizing facility is required.

On the other hand, a bonding material using nano-sized metal particles may have poor long-term reliability, such as a decrease in bonding strength over time. The reason for this is that in a bonding material using nano-sized metal particles, a protective agent (organic substance) for suppressing aggregation is generally contained on the surface of the nano-sized metal particles, and this protective agent is used as a bonding layer. It is considered that this is because the bonding strength is lowered by generating voids in the bonding layer by remaining in the bonding layer and decomposing with the passage of time.

The present invention has been made in view of the above-mentioned circumstances, and is an agglomerate of metal particles capable of forming a bonding layer capable of bonding members such as electronic parts with high bonding strength and long-term reliability. An object of the present invention is to provide a method for producing the same, a paste-like metal particle composition, and a method for producing a conjugate using the paste-like metal particle composition.

As a result of diligent studies, the inventors have found particles containing at least one metal selected from the group consisting of silver, gold and copper in an amount of 70% by mass or more and having a particle size in the range of 100 nm or more and less than 500 nm. The ratio of particles in the range of 60% by volume or more and 95% by volume or less, particles having a particle size in the range of 50 nm or more and less than 100 nm in the range of 5% by volume or more and 40% by volume or less, and particles having a particle size of less than 50 nm in the range of 5% by volume or less. In the volume-based particle size distribution curve measured by the laser diffraction scattering method, which contains metal particles and organic substances contained in the above, D10 is in the range of 0.05 μm or more and 0.25 μm or less, and D50 is 0.4 μm or more. An aggregate of metal particles having a range of 0.6 μm or less, a D90 of 1.5 μm or more and 2.5 μm or less, and containing the organic substance in an amount of 2% by mass or less with respect to the metal particles. It has been found that it is possible to obtain a bonding layer having high bonding strength by sintering. Furthermore, it has been found that the bonding layer is less likely to generate voids even if it is repeatedly subjected to a cooling and heating cycle, and has high long-term reliability.

The reason why a bonding layer having high bonding strength can be obtained by using the above-mentioned metal particle agglomerates is considered as follows. Since the metal particles (primary particles) have a relatively wide particle size distribution as described above, the metal particle aggregates (secondary particles) are dense with few gaps (voids) between the metal particles. Since the metal particle agglomerates also have a relatively wide particle size distribution as described above, it is possible to form a dense metal particle agglomerate layer with few gaps between the metal particle agglomerates. Further, the content of the organic substance is 2% by mass or less, and the amount of the decomposition gas of the organic substance generated by heating is small. Therefore, the bonding layer formed by sintering the metal particle agglomerate layer has few voids and becomes dense. Therefore, the bonding layer has improved bonding strength and long-term reliability.

That is, the metal particle agglomerate of the present invention is composed of any one of silver, gold and copper, does not contain particles having a particle size of 500 nm or more in an amount of more than 1% by volume, and has a particle size of 100 nm or more and less than 500 nm. Particles in the range of 60% by volume or more and 95% by volume or less, particles in the range of 50 nm or more and less than 100 nm in the range of 5% by volume or more and 40% by volume or less, and particles having a particle size of less than 50 nm. In the volume-based particle size distribution curve containing metal particles and organic substances contained in a proportion of 5% by volume or less and measured by the laser diffraction scattering method, D10 is in the range of 0.05 μm or more and 0.25 μm or less. D50 is in the range of 0.4 μm or more and 0.6 μm or less, and D90 is in the range of 1.5 μm or more and 2.5 μm or less, and the organic substance is added in an amount of 2% by mass or less with respect to the metal particles. It is characterized by including.

In the metal particle aggregate of the present invention, the content of the organic substance is preferably 0.05% by mass or more with respect to the metal particles.
In this case, since the metal particle agglomerates are coated with 0.05% by mass or more of organic substances with respect to the metal particles, the surface state becomes stable. Therefore, even when this metal particle agglomerate is mixed with a volatile solvent to form a paste, it does not cause grain growth such as further agglomeration, so that the members are joined with high bonding strength and long-term reliability. It becomes possible.

In the metal particle aggregate of the present invention, the specific surface area is preferably in the range of ^{2 to 8 m 2 / g.}
In this case, since the reaction area of the metal particle aggregate is large, the reactivity by heating becomes high. Therefore, this metal particle agglomerate can be sintered at a relatively low temperature.

The method for producing a metal particle agglomerate of the present invention comprises any one of silver, gold and copper, does not contain 1% by volume or more of particles having a particle size of 500 nm or more, and has a particle size of 100 nm or more and less than 500 nm. Particles in the range are in the range of 65% by volume or more and 95% by volume, particles in the range of 50 nm or more and less than 100 nm are in the range of 5% by volume or more and 30% by volume, and particles with a particle size of less than 50 nm are in the range of 5% by volume. A step of preparing a slurry containing metal particles contained in the following proportions, an organic reducing agent, and water, reducing the metal particles to agglomerate the metal particles, and taking out the agglomerated metal particles from the slurry to obtain the above-mentioned It is characterized by comprising a step of obtaining a hydrous metal particle agglomerate containing an organic reducing agent in an amount of 2% by mass or less with respect to the metal particles, and a step of drying the hydrous metal particle agglomerate.

According to the method for producing a metal particle agglomerate of the present invention, the metal particles having a specific particle size distribution are reduced in a slurry containing an organic reducing agent to agglomerate the metal particles. It is possible to stably generate metal particle agglomerates having high agglomeration strength. Further, the metal particle agglomerates taken out from the slurry are made into hydrous metal particle agglomerates containing an organic reducing agent in an amount of 2% by mass or less with respect to the metal particles, and then dried, so that the obtained metal particle agglomerates are obtained. The content of organic matter in the above can be 2% by mass or less.

The paste-like metal particle composition of the present invention is characterized by containing a volatile solvent and the above-mentioned metal particle aggregate of the present invention.
According to the paste-like metal particle composition of the present invention, since the metal particle aggregate of the present invention is contained, it is possible to join the members to be joined with high bonding strength and long-term reliability.

The method for producing a bonded body is a method for producing a bonded body in which a first member and a second member are bonded via a bonding layer, and the above-mentioned paste-like metal particle composition of the present invention is used. It is characterized by forming a bonding layer.
According to the method for producing a bonded body of the present invention, since the bonded layer is formed by using the paste-like metal particle composition of the present invention, the first member and the second member have high bonding strength and long-term reliability. It is possible to join the members of the above.

According to the present invention, a metal particle agglomerate capable of bonding members such as electronic parts with high bonding strength and long-term reliability, a method for producing the same, a paste-like metal particle composition, and the paste-like metal particles thereof. A bonded body using the composition can be provided.

It is sectional drawing of an example of the bonded body produced using the paste-like metal particle composition of this embodiment.

<Metal particle agglomerates>
The metal particle agglomerate according to the embodiment of the present invention will be described.
The metal particle aggregate in the present embodiment can be used as a material for a paste-like metal particle composition (bonding material) for bonding a circuit board and an electronic component such as a semiconductor chip or an LED element.

The metal particle agglomerates of the present embodiment include metal particles and organic substances.
The metal particles (primary particles) contain at least one metal selected from the group consisting of silver, gold and copper in an amount of 70% by mass or more.
The metal content of the metal particles is preferably 90% by mass or more, particularly preferably 99% by mass or more. The higher the purity of the metal particles, the easier it is to melt, so that the metal particles can be sintered at a relatively low temperature.

The metal particles do not contain 1% by volume or more of particles having a particle size of 500 nm or more, and particles having a particle size of 100 nm or more and less than 500 nm are included in the range of 65% by volume or more and 95% by volume, and the particle size is 50 nm or more and 100 nm. Particles in the range of less than 5% by volume and 30% by volume are included, and particles having a particle size of less than 50 nm are included in a proportion of 5% by volume or less. Since the metal particles have a relatively wide particle size distribution as described above, it is possible to form a dense metal particle agglomerate having a small gap between the metal particles. Since the gap between the metal particles constituting the metal particle aggregate is small, it is possible to form a bonding layer having few voids. For the particle size of the metal particles, for example, the projected area of the metal particles is measured using an SEM (scanning electron microscope), and the diameter equivalent to a circle (a circle having the same area as the projected area of the silver particles) is obtained from the obtained projected area. It can be obtained by calculating (diameter) and converting the calculated particle size into a volume-based particle size.

The content of the metal particles having a particle size in the range of 100 nm or more and less than 500 nm is preferably in the range of 70% by volume or more and 90% by volume. The content of the metal particles having a particle size in the range of 50 nm or more and less than 100 nm is preferably in the range of 10% by volume or more and 30% by volume. The content of the metal particles having a particle size of less than 50 nm is preferably 1% by volume or less. When the particle size distribution of the metal particles is within the above range, the effect of forming aggregates with small gaps between the particles is enhanced, and it is possible to form a bonding layer having few voids.

The organic substance contained in the metal particle aggregate of the present embodiment is preferably an organic reducing agent or a decomposition product thereof. Further, the organic substance is preferably one that decomposes or volatilizes at a temperature of 150 ° C. Examples of organic reducing agents include ascorbic acid, formic acid and tartaric acid.
The organic reducing agent or an organic substance which is a decomposition product thereof has an effect of suppressing oxidation of the surface of the metal particles and suppressing diffusion of metal atoms during storage of the metal particle aggregates. Further, the above-mentioned organic substance is easily decomposed or volatilized when the metal particle agglomerate is printed on the surface to be bonded of the member to be bonded and heated, thereby exposing the highly active surface of the metal particles to the metal. It has the effect of facilitating the sintering reaction between particles. Further, the above-mentioned decomposition products or volatile substances of the organic substance have a reducing ability to reduce the oxide film on the surface to be bonded of the member to be bonded.
If the organic matter contained in the metal particle aggregate remains in the bonding layer, it may be decomposed with the passage of time to generate voids in the bonding layer. Therefore, in the metal particle agglomerate of the present embodiment, the content of organic matter is limited to an amount of 2% by mass or less with respect to the metal particles.
However, in order to obtain the above effect of the organic substance, the content of the organic substance is preferably 0.05% by mass or more with respect to the metal particles.

The metal particle agglomerate of the present embodiment is an agglomerate of the above metal particles (primary particles), and D10 is 0.05 μm or more and 0.25 μm or less in the volume-based particle size distribution curve measured by the laser diffraction scattering method. In the range of, D50 is in the range of 0.4 μm or more and 0.6 μm or less, and D90 is in the range of 1.5 μm or more and 2.5 μm or less. Since the metal particle agglomerates have a relatively wide particle size distribution as described above, a dense metal particle agglomerate layer with few gaps between the metal particle agglomerates can be formed, and a bonding layer with few voids can be formed. Can be done.

The metal particle agglomerates of the present embodiment preferably have a specific surface area in the range of ^{2 to 8 m 2 / g.}
A metal particle agglomerate having a specific surface area in the above range has a large reaction area of the metal particles and a high reactivity by heating. Therefore, this metal particle agglomerate can be sintered at a relatively low temperature.

Next, a method for producing the metal particle aggregate of the present embodiment will be described.
The method for producing a metal particle aggregate of the present embodiment contains at least one metal selected from the group consisting of silver, gold and copper in an amount of 70% by mass or more, and one volume of particles having a particle size of 500 nm or more. % Or more, particles having a particle size in the range of 100 nm or more and less than 500 nm are in the range of 65% by volume or more and 95% by volume, and particles having a particle size in the range of 50 nm or more and less than 100 nm are in the range of 5% by volume or more and 30% by volume. A slurry containing metal particles containing particles having a particle size of less than 50 nm at a ratio of 5% by volume or less, an organic reducing agent, and water is prepared, and the metal particles are reduced to agglomerate the metal particles. A step of taking out agglomerated metal particles from the slurry to obtain a hydrous metal particle agglomerate containing the organic reducing agent in an amount of 2% by mass or less with respect to the metal particles, and a step of coagulating the hydrous metal particles. It includes a step of drying the aggregate.

The components of the metal particles used as the raw material are the same as the preferable components of the metal particles contained in the above-mentioned metal particle agglomerates. Further, the preferable particle size distribution of the metal particles is the same as the particle size distribution of the metal particles contained in the above-mentioned metal particle aggregate.

The metal particles having the above-mentioned particle size distribution include, for example, metal particles having a particle size in the range of 100 nm or more and less than 500 nm, metal particles having a particle size in the range of 50 nm or more and less than 100 nm, and metal particles having a particle size of less than 50 nm. Each can be prepared and manufactured by a mixing method.
Further, the metal particles having the above-mentioned particle size distribution are obtained by mixing an aqueous solution of an organic acid metal salt (salt of silver, gold, copper) and an organic substance having a reducing action on silver, gold, and copper to form a metal salt. Can also be produced by a method of reducing and precipitating as metal particles to obtain a slurry of metal particles. Examples of organic acid metal salts include oxalic acid metal salts, citrate metal salts and maleic acid metal salts. Examples of reducing organic substances include ascorbic acid, formic acid, tartaric acid and salts thereof. The particle size distribution of the metal particles obtained by this production method can be appropriately adjusted depending on the blending amount of the organic acid metal salt and the organic substance, and the temperature and time at the time of reduction.

In the method for producing a metal particle agglomerate of the present embodiment, a slurry containing the metal particles, an organic reducing agent, and water is prepared, the metal particles are reduced, and the metal particles are agglomerated. By reducing the surface of the metal particles, removing the oxide film, and activating the surface of the metal particles, it is possible to stably generate metal particle agglomerates having high aggregation strength between the metal particles. The metal particles are reduced with an organic reducing agent to form aggregates of the metal particles. The surface of the generated metal particle agglomerates is coated with an organic reducing agent. As a result, an aggregate having high shape stability can be obtained.

When preparing the slurry, the mixing order of the metal particles, the organic substance and the water is not particularly limited. Metal particles, organic matter and water may be mixed at the same time, a mixture containing metal particles and organic matter and water may be mixed, or a mixture containing metal particles and water and organic matter may be mixed. , A mixture containing organic matter and water and metal particles may be mixed.

When the metal particles are reduced, it is preferable to heat the slurry. The heating temperature of the slurry is usually 90 ° C. or lower, preferably 50 ° C. or higher and 80 ° C. or lower. If the heating temperature is higher than the above temperature, the metal particles may be excessively reduced and the particle size of the agglomerates may become too large. On the other hand, if the heating temperature is lower than the above temperature, the metal particles may not be reduced and aggregates may not be formed.

In the method for producing agglomerates of metal particles of the present embodiment, the agglomerated metal particles are taken out from the slurry and washed with water or the like to contain an organic reducing agent in an amount of 2% by mass or less with respect to the metal particles. Get an aggregate. As a method for extracting metal particles from the slurry, a method such as centrifugation, filtration, or decantation can be used.

<Paste-like metal particle composition>
Next, the paste-like metal particle composition (bonding material) of the present embodiment will be described.
The paste-like metal particle composition of the present embodiment contains a volatile solvent and the above-mentioned metal particle agglomerates. Examples of volatile solvents include alcohol solvents, glycol solvents, acetate solvents, hydrocarbon solvents and amine solvents. Specific examples of the alcohol solvent include α-terpineol and isopropyl alcohol. Specific examples of the glycol-based solvent include ethylene glycol, diethylene glycol, and polyethylene glycol. Specific examples of the acetate-based solvent include butyl butyl toll carbitate acetate. Specific examples of the hydrocarbon solvent include decane, dodecane, and tetradecane. Specific examples of amine-based solvents include hexylamine, octylamine, and dodecylamine.

The content of the metal particle agglomerates in the paste-like metal particle composition is preferably 50% by mass or more, and is in the range of 70% by mass or more and 95% by mass or less with respect to the total amount of the paste-like metal particle composition. Is particularly preferred. When the content of the metal particle agglomerates is in the above range, the viscosity of the paste-like metal particle composition does not become too low, and the paste-like metal particle composition can be stably applied to the surface of the member. Further, by firing the paste-like metal particle composition, a sintered body (bonded layer) having a high density and a small amount of voids generated can be obtained.

The paste-like metal particle composition of the present embodiment may further contain additives such as an antioxidant and a viscosity modifier. The content of these additives is preferably in the range of 1% by mass or more and 5% by mass or less in terms of the total amount of the paste-like metal particle composition.

The paste-like metal particle composition of the present embodiment can be produced, for example, by kneading a mixture obtained by mixing a volatile solvent and a metal particle agglomerate using a kneading device. As the kneading device, a three-roll mill can be used.

<Joined body>
Next, a method for producing a bonded body using the paste-like metal particle composition of the present embodiment will be described with reference to FIG. FIG. 1 shows a cross-sectional view of a bonded body produced by using the paste-like metal particle composition of the present embodiment. As shown in FIG. 1, the joint body 11 is roughly configured by including a substrate 12, a first metal layer 13, a joint layer 14, a second metal layer 15, and an object to be joined 16. There is.

In the present embodiment, as an example, the bonded body 11 in which the substrate 12 (first member) and the object to be bonded 16 (second member) are bonded using the above-mentioned paste-like metal particle composition (bonding material). As described above, the bonding using the paste-like metal particle composition is not particularly limited.

The substrate 12 is not particularly limited, and specific examples thereof include an aluminum plate, an insulating substrate to which an aluminum plate is joined, and a circuit board.

The first metal layer 13 is laminated adjacent to the substrate 12. The substrate 12 and the bonding layer 14 are bonded via the first metal layer 13. As the material of the first metal layer 13, for example, one kind or two or more kinds of metals selected from the group consisting of gold, silver, copper and the like can be used.

The bonding layer 14 is laminated adjacently between the first metal layer 13 and the second metal layer 15.
The bonding layer 14 is in contact with the first metal layer 13 to form an interface 17. Further, the bonding layer 14 is in contact with the second metal layer 15 to form an interface 18. The bonding layer 14 is formed by applying the above-mentioned bonding material on the first metal layer 13, placing the object to be bonded 16 so that the coated surface and the second metal layer 15 face each other, and heat-treating. It is a thing.

The thickness of the bonding layer 14 is not particularly limited as long as it can bond the substrate 12 and the object 16 to be bonded. Specifically, for example, it may be 1 to 100 μm.

The second metal layer 15 is laminated adjacent to the opposite side of the first metal layer 13 via the bonding layer 14. The bonding layer 14 and the object to be bonded 16 are bonded via the second metal layer 15.
As the material of the second metal layer 15, the same material as that used for the first metal layer 13 can be used.

The object 16 to be bonded is laminated adjacent to the opposite side of the bonding layer 14 via the second metal layer 15. The object to be joined 16 is not particularly limited, and specific examples thereof include electronic components such as silicon (Si), silicon carbide (SiC), semiconductor chips, and LED elements. Further, since the bonded body 11 of the present embodiment uses the above-mentioned bonding material, a heat-sensitive material can also be used as the object to be bonded 16.

In the bonded body 11 of the present embodiment, the substrate 12 and the object to be joined 16 are bonded by the bonding layer 14. Since the bonding layer 14 is formed by using the above-mentioned bonding material, the bonding strength and long-term reliability of the bonding layer 14 are improved. Specifically, as the bonding strength (share strength) of the bonded body 11 of the present embodiment, for example, 20 MPa or more is preferable, and 30 MPa or more is more preferable.

The bonding strength can be measured using, for example, a commercially available bonding tester (for example, manufactured by RHESCA). The effect of improving the long-term reliability can be confirmed, for example, by the amount of increase in the void area ratio of the bonding layer 14 when the bonding body 11 is repeatedly subjected to the cooling and heating cycle. If the increase in the void area ratio is small, the long-term reliability is high.

Next, the method for manufacturing the bonded body 11 described above will be described with reference to FIG.
First, the first metal layer 13 is laminated by laminating a metal on the surface of the substrate 12 by a well-known method. Similarly, the second metal layer 15 is laminated on the surface of the object to be joined 16.

The method of laminating the metal on the surfaces of the substrate 12 and the object 16 is not particularly limited, and specific examples thereof include a vacuum vapor deposition method, a sputtering method, a plating method, and a printing method.

Next, the above-mentioned bonding material is applied to the surface of the first metal layer 13 by a well-known method. The method of applying the bonding material to the surface of the first metal layer 13 is not particularly limited, and specific examples thereof include a spin coating method, a metal mask method, and a screen printing method.

Next, the object to be joined 16 is placed on the bonding material applied to the surface of the first metal layer 13 so that the second metal layer 15 side faces each other. After that, by heat treatment, a bonding layer 14 is formed from the bonding material, and the first metal layer 13 and the second metal layer 15 are bonded via the bonding layer 14.

The heating temperature during the heat treatment is not particularly limited, but is preferably in the range of, for example, 120 ° C. or higher, more specifically 120 ° C. or higher and 400 ° C. or lower. When the heating temperature is in the above range, the bonding strength and long-term reliability of the bonding layer 14 can be increased. Further, at the time of heat treatment, either the substrate 12 or the object to be joined 16 may be pressurized at a pressure of 10 MPa or less. By pressurizing, the bonding layer 14 becomes dense, and the bonding strength and long-term reliability can be increased.

The heating time during the heat treatment is not particularly limited, but specifically, for example, 30 minutes or more is preferable. When the heating time is 30 minutes or more, the bonding strength and long-term reliability of the bonding layer 14 can be increased.
The bonded body 11 is manufactured by the above steps.

Hereinafter, the effects of the present invention will be described in detail with reference to Examples, but the present invention is not limited to the following Examples.

[Example 1 of the present invention]
(1) Silver particle agglomerates Silver particles having a D10 of 20 nm, a D50 of 50 nm and a D90 of 100 nm, and silver particles having a D10 of 150 nm, a D50 of 300 nm and a D90 of 500 nm were prepared. D10, D50, and D90 of the silver particles were obtained from the particle size distribution curve of the silver particles. The particle size distribution curve of silver particles was measured by the following method using a dynamic light scattering method.
The prepared silver particles having a D50 of 50 nm and silver particles having a D50 of 300 nm were mixed at a mass ratio of 1: 3 to obtain a silver particle mixture.

(Measurement method of particle size distribution curve by dynamic light scattering method)
First, 0.1 g of silver powder was put into 20 g of ion-exchanged water, and ultrasonic waves of 25 kHz were irradiated for 5 minutes to disperse silver particles in the ion-exchanged water. Next, the obtained silver particle agglomerate dispersion was poured into an observation cell for a dynamic light scattering type particle size distribution measuring device (manufactured by HORIBA, Ltd .: LB-550), and the particle size distribution was measured according to the procedure of this device.

The silver particle mixture obtained above, sodium ascorbate (organic reducing agent), and water were mixed at a mass ratio of 10: 1: 89 to prepare a silver particle slurry. The prepared silver particle slurry was heated at a temperature of 90 ° C. for 3 hours to reduce the silver particles. Then, after allowing the silver particle slurry to cool to room temperature, the solid matter was separated and recovered using a centrifuge. The recovered solid matter (mercury-containing particle agglomerates) was washed with water several times and dried to obtain silver particle agglomerates.

Regarding the obtained silver particle agglomerates, the particle size distribution of the silver particles (primary particles) constituting the silver particle agglomerates, the particle size distribution curve of the silver particle agglomerates (secondary particles) by the laser diffraction scattering method, and the silver particle coagulation. The content of organic matter contained in the aggregate and the specific surface area of the silver particle aggregate were measured by the following methods. The results are shown in Table 1.

(Measurement method of particle size distribution of silver particles)
Images of 500 silver particle aggregates were acquired using SEM, and the particle size of the silver particles contained in each silver particle aggregate was measured. At this time, the device magnification of the SEM was set to 100,000 times. From the SEM image of 500 silver particle aggregates, silver particles in which the entire outline of the silver particles (primary particles) can be visually recognized were extracted. Next, the projected area of the extracted silver particles was measured using image processing software (Image-J), the equivalent circle diameter was calculated from the obtained projected area, and this was used as the particle size of the silver particles. The diameter equivalent to the circle was not measured for silver particles whose contours could not be visually recognized. The particle size of the obtained silver particles was converted into a volume-based particle size, and the particle size distribution of the volume-based particle size was obtained. The results are shown in the column of "particle size distribution of metal particles" in Table 1.

(Measurement method of particle size distribution curve by laser diffraction scattering method of silver particle aggregate)
First, 0.1 g of silver particle aggregates was put into 20 g of ion-exchanged water, and ultrasonic waves of 25 kHz were irradiated for 5 minutes to disperse the silver particle aggregates in the ion-exchanged water. Next, an appropriate amount of the obtained silver particle agglomerate dispersion was dropped onto an observation cell of a laser diffraction / scattering type particle size distribution measuring device (manufactured by HORIBA, Ltd .: LA-960), and the particle size distribution was measured according to the procedure of this device. The particle size distribution measured by this laser diffraction / scattering method is a particle size distribution of silver particle aggregates (secondary particles) that treats aggregates of silver particles (primary particles) as one particle. The results are shown in the column of "Particle size distribution of metal particle aggregates" in Table 1.

(Measuring method of organic matter content)
The silver particle agglomerates were weighed and heated in the air at a temperature of 150 ° C. for 30 minutes. After heating, the mixture was allowed to cool to room temperature, and the mass of silver particle aggregates was measured. The content of organic matter was calculated from the following formula. The results are shown in the "Organic matter content" column of Table 1.
Organic matter content (% by mass) = (AB) / A × 100
(However, A is the mass of the silver particle agglomerates before heating, and B is the mass of the silver particle agglomerates after heating.)

(Method of measuring specific surface area)
As the measuring apparatus, using a QUANTACHROME AUTOSORB-1 (manufactured by Quantachrome Instruments), was determined from the amount of adsorbed _{N 2} gas to chilled silver particles agglomerate. The results are shown in the "Specific surface area" column of Table 1.

(2) Paste-like silver particle composition The silver particle aggregate obtained in (1) above and ethylene glycol were mixed at a mass ratio of 70:30. The obtained mixture was kneaded using a three-roll mill to prepare a paste-like silver particle composition.

(3) Joined body A 20 mm square Cu plate (thickness: 1 mm) with gold plating on the outermost surface is used as the first member, and a 2.5 mm square Si wafer (thickness: 1 mm) with gold plating on the outermost surface as the second member. Thickness: 200 μm) was prepared. The paste-like silver particle composition prepared in (2) above was applied to the surface of the first member by a metal mask method to form a paste layer. Next, the second member is placed on the paste layer and heated at a temperature of 200 ° C. for 30 minutes to prepare a bonded body in which the first member and the second member are bonded via the bonding layer. did. The joint strength (share strength) of the obtained joint was measured by the following method. Further, the bonded body was loaded with a cold cycle of 200 ° C.⇔-40 ° C. for 1000 cycles by the liquid phase method, and the void area ratio in the joint layer before and after the cold heat cycle was measured by the following method. The results are shown in Table 1 below.

(Measuring method of joint strength of joint body)
The joint strength was measured using a shear strength evaluation tester. For measurement, the first member (Cu plate) of the bonded body is fixed horizontally, and the second member (Si wafer) is pushed horizontally from the side using a shear tool at a position 50 μm above the surface of the bonded layer. , The strength when the second member was broken was measured. The moving speed of the share tool was 0.1 mm / sec. Intensity tests were performed three times under one condition, and their arithmetic mean values were used as measured values. A bonding tester (Model: PTR-1101) manufactured by Resca Co., Ltd. was used as a shear strength evaluation tester.

(Measurement method of void area ratio in the joint layer)
Using an ultrasonic flaw detector, the void area ratio in the joint layer was calculated from the following formula. Here, the area of the bonding layer is defined as the area to be bonded by the bonding layer, that is, the area of the second member. Further, in the ultrasonic flaw detection image, the portion where the first member and the second member are separated is indicated by a white portion, and therefore the area of this white portion is defined as the void area.
Void area ratio (%) = void area / bonding layer area x 100

[Example 2 of the present invention]
Example 1 of the present invention except that the mixing ratio of the silver particles having a D50 of 50 nm and the silver particles having a D50 of 300 nm was 1: 1 in the (1) silver particle aggregate of the present invention example 1. A silver particle aggregate, a paste-like silver particle composition, and a bonded body were produced in the same manner as in Example 1 of the present invention, and the same evaluation as in Example 1 of the present invention was performed. The results are shown in Table 1.

[Example 3 of the present invention]
In the (1) silver particle agglomerate of the present invention example 1, the mixing ratio of the silver particles having a D50 of 50 nm and the silver particles having a D50 of 300 nm was set to 1: 5 in terms of mass ratio. In the same manner, a silver particle agglomerate, a paste-like silver particle composition, and a bonded body were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

[Example 4 of the present invention]
In the silver particle agglomerate of the present invention example 1, the silver particle agglomerate and the paste-like silver are the same as those of the present invention example 1 except that the silver powder prepared by the following method is used instead of the silver particle mixture. A particle composition and a conjugate were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

(How to make silver powder)
First, 900 g of a silver nitrate aqueous solution held at 50 ° C. and 600 g of a sodium citrate aqueous solution held at 50 ° C. were simultaneously added dropwise to 1200 g of ion-exchanged water held at 50 ° C. over 5 minutes, and silver citrate was added. A slurry was prepared. The ion-exchanged water was continuously stirred while the silver nitrate aqueous solution and the sodium citrate aqueous solution were simultaneously added dropwise to the ion-exchanged water. The concentration of silver nitrate in the silver nitrate aqueous solution was 66% by mass, and the concentration of citric acid in the sodium citrate aqueous solution was 56% by mass.
Next, a 300 g aqueous sodium formate solution kept at 50 ° C. was added dropwise to the silver citrate slurry held at 50 ° C. over 30 minutes to obtain a mixed slurry. The concentration of formic acid in this sodium formate aqueous solution was 58% by mass.
Next, the mixed slurry was subjected to a predetermined heat treatment. Specifically, the mixed slurry was raised to a maximum temperature of 60 ° C. at a heating rate of 10 ° C./hour, held at 60 ° C. (maximum temperature) for 30 minutes, and then lowered to 20 ° C. over 60 minutes. .. As a result, a silver powder slurry was obtained. The silver powder slurry was placed in a centrifuge and rotated at a rotation speed of 1000 rpm for 10 minutes. As a result, the liquid layer in the silver powder slurry was removed to obtain a dehydrated and desalted silver powder slurry.
The dehydrated and desalted silver powder slurry was dried by a freeze-drying method for 30 hours to obtain silver powder.

[Example 5 of the present invention]
In the silver particle agglomerate of Example 1 of the present invention, the number of times of washing the mercury-containing particle agglomerate recovered from the silver particle slurry with water was increased to reduce the amount of ascorbic acid remaining in the mercury-containing particle agglomerate. A silver particle aggregate, a paste-like silver particle composition, and a conjugate were produced in the same manner as in Example 1 of the present invention except for the above, and the same evaluation as in Example 1 of the present invention was performed. The results are shown in Table 1.

[Example 6 of the present invention]
In (1) silver particle agglomerates of Example 1 of the present invention, the number of times of washing the mercury-containing particle agglomerates recovered from the silver particle slurry with water was reduced, and the amount of ascorbic acid remaining in the mercury-containing particle agglomerates was increased. A silver particle aggregate, a paste-like silver particle composition, and a conjugate were produced in the same manner as in Example 1 of the present invention except for the above, and the same evaluation as in Example 1 of the present invention was performed. The results are shown in Table 1.

[Example 7 of the present invention]
Instead of silver particles, gold particles having a D10 of 35 nm, a D50 of 50 nm, and a D90 of 70 nm were used, and the gold particles, sodium ascorbate (organic reducing agent), and water were mixed in a mass ratio of 10: 5: 85. A gold particle agglomerate, a paste-like gold particle composition, and a bonded body were produced in the same manner as in Example 1 of the present invention except that they were mixed in the same proportion as in Example 1 of the present invention. The results are shown in Table 1. The gold particles D10, D50, and D90 were measured by a dynamic light scattering method.

[Example 8 of the present invention]
A copper particle agglomerate, a paste-like copper particle composition, and a bonded body were produced in the same manner as in Example 1 of the present invention except that copper particles having the particle size distribution shown in Table 1 were used instead of the silver particles. The same evaluation as in Invention Example 1 was performed. The results are shown in Table 1.

[Example 9 of the present invention]
In the silver particle agglomerate of Example 1 of the present invention (1), the mixing ratio of the silver particles having a D50 of 50 nm and the silver particles having a D50 of 300 nm was set to 2: 1 in terms of mass ratio. A silver particle aggregate, a paste-like silver particle composition, and a bonded body were produced in the same manner as in Example 1 of the present invention, and the same evaluation as in Example 1 of the present invention was performed. The results are shown in Table 1.

[Example 10 of the present invention]
In the (1) silver particle aggregate of the present invention example 1, the mixing ratio of the silver particles having a D50 of 50 nm and the silver particles having a D50 of 300 nm was set to 1: 6 in terms of mass ratio. In the same manner, a silver particle agglomerate, a paste-like silver particle composition, and a bonded body were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

[Example 11 of the present invention]
In Example 5 of the present invention, except that the number of times of washing the mercury-containing particle agglomerates recovered from the silver particle slurry with water was further increased to reduce the amount of ascorbic acid remaining in the mercury-containing particle agglomerates. In the same manner as in Example 1, a silver particle aggregate, a paste-like silver particle composition, and a bonded body were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

[Comparative Example 1]
In the silver particle agglomerate of the present invention example 1 (1), the silver particle agglomerate was similar to that of the present invention example 1 except that only silver particles having a D50 of 300 nm were used and sodium ascorbate was not added. A paste-like silver particle composition and a conjugate were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

[Comparative Example 2]
In the same manner as in Example 1 of the present invention except that only silver particles having a D50 of 50 nm were used in the (1) silver particle aggregate of Example 1 of the present invention, the silver particle aggregate, the paste-like silver particle composition, and the conjugate. Was produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

[Comparative Example 3]
In the silver particle agglomerate of the present invention example 1 (1), the silver particle agglomerate and the paste-like silver particle are the same as those of the present invention example 1 except that the mercury-containing particle agglomerate recovered from the particle slurry was not washed with water. The composition and the bonded product were produced and evaluated in the same manner as in Example 1 of the present invention. The results are shown in Table 1.

In Comparative Example 1 in which the maximum particle size of the silver particle agglomerates exceeds the range of the present invention, it is considered that the void area ratio is high and the bonding strength is low because a large number of voids are generated due to the gaps between the silver particle agglomerates. Be done.
In Comparative Example 2 in which the proportion of fine silver particles (primary particles) having a size of less than 50 nm contained in the silver particle agglomerates exceeds the range of the present invention, the fine silver particles are non-uniformly agglomerated and partially formed into the silver particle agglomerates. It is considered that the voids are formed and the voids formed in the agglomerates of silver particles appear as voids, the void area ratio is increased, and the bonding strength is decreased.
In Comparative Example 3 in which the content of the organic substance in the silver particle aggregate exceeds the range of the present invention, the organic substance is volatilized by heating during the production of the bonded body, a large amount of voids are formed in the bonded layer, and the void area ratio is increased. It is probable that the joint strength became higher and the joint strength became lower.

On the other hand, in Example 1-11 of the present invention in which the particle size distribution of the metal particles (primary particles) and the content of organic substances were within the range of the present invention, the bonding strength of the bonded body was high and the bonding layer was contained. The void area ratio has decreased. In particular, in Example 1-8 of the present invention in which the content of organic matter is 0.05% by mass or more with respect to the metal particles and the specific surface area is in ^{the range of 2} to 8 m 2 / g, the bonding strength of the bonded body is high. It became higher. In addition, the void area ratio in the bonding layer before the cold cycle became lower, and at the same time, the increase in the void area ratio after the cold cycle was suppressed. It was confirmed that the long-term reliability of the conjugate was improved by suppressing this increase in the void area ratio.

The silver particle agglomerate of the present invention can be applied to the bonding of semiconductor chips of power modules and the bonding of LED elements that require bonding without pressurization.

11 ... Bonded body 12 ... Substrate 13 ... First metal layer 14 ... Bonded layer 15 ... Second metal layer 16 ... Jointed object 17, 18 ... Interface

Claims (6)

It is composed of any one of silver, gold and copper , and does not contain more than 1% by volume of particles having a particle size of 500 nm or more, and 60% by volume or more of particles having a particle size in the range of 100 nm or more and less than 500 nm 95. Metal particles containing particles having a volume of 50 nm or more and less than 100 nm in a range of 5% by volume or more and 40% by volume or less, and particles having a particle size of less than 50 nm in a proportion of 5% by volume or less. When,
Including organic matter
In the volume-based particle size distribution curve measured by the laser diffraction / scattering method, D10 is in the range of 0.05 μm or more and 0.25 μm or less, D50 is in the range of 0.4 μm or more and 0.6 μm or less, and D90 is. A metal particle agglomerate in a range of 1.5 μm or more and 2.5 μm or less, which contains the organic substance in an amount of 2% by mass or less with respect to the metal particles. The metal particle agglomerate according to claim 1, wherein the content of the organic substance is 0.05% by mass or more with respect to the metal particles. The metal particle agglomerate according to claim 1 or ^{2, wherein the} specific surface area is in the range of 2 to 8 m 2 / g. It is composed of any one of silver, gold and copper, and does not contain 1% by volume or more of particles having a particle size of 500 nm or more, and 65% by volume or more and 95% by volume of particles having a particle size in the range of 100 nm or more and less than 500 nm. Metal particles and organic reducing agent containing particles having a particle size of 50 nm or more and less than 100 nm in a range of 5% by volume or more and 30% by volume, and particles having a particle size of less than 50 nm in a proportion of 5% by volume or less. A step of preparing a slurry containing water and water and reducing the metal particles to agglomerate the metal particles, and taking out the agglomerated metal particles from the slurry and applying the organic reducing agent to the metal particles 2 The metal according to any one of claims 1 to 3, further comprising a step of obtaining a hydrous metal particle agglomerate contained in an amount of mass% or less and a step of drying the hydrous metal particle agglomerate. Method for producing particle agglomerates. A paste-like metal particle composition comprising a volatile solvent and the metal particle aggregate according to any one of claims 1 to 3. A method for manufacturing a bonded body in which a first member and a second member are joined via a bonding layer.
A method for producing a bonded body, which comprises forming the bonded layer using the paste-like metal particle composition according to claim 5.

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