JP6679909B2 - Bonding material and method for manufacturing bonded body - Google Patents

Description

  The present invention relates to a bonding material and a method for manufacturing a bonded body.

  When joining two or more components in the assembly and mounting of electronic components, a joining material is generally used. As such a bonding material, a paste-shaped bonding material in which metal particles such as silver powder are dispersed in a solvent is known. When joining components using a joining material, the joining material is applied to the surface of one component, the other component is brought into contact with the application surface, and heat treatment is performed in this state. The components can be joined by sintering the metal particles by this heat treatment to form a joining layer. The bonding layer is required to have high shear strength (bonding strength).

  For example, in Patent Document 1, as a bonding material capable of reducing shearing strength unevenness while securing shear strength, metal particles of submicron size having an average primary particle diameter of 0.5 to 3.0 μm, and an average primary particle diameter are used. A bonding material containing nano-sized metal particles having a particle diameter of 1 to 200 nm and a dispersion medium is disclosed.

  Further, in Patent Document 2, as a bonding material capable of ensuring high shear strength even with nanoparticles alone, metal nanoparticles having an average particle size of 100 nm or less and a surface coated with an organic substance having 6 to 8 carbon atoms, and the metal A bonding material comprising 5 to 20% by mass of a polar solvent based on the powder of nanoparticles is disclosed.

JP, 2011-80147, A International Publication No. 2011/007402

  As described above, in the paste-like bonding material in which the metal particles are dispersed in the solvent, nano-sized or submicron-sized metal fine particles are used because of their high sinterability.

  However, in the bonding material disclosed in Patent Document 1, it is necessary to heat at a heating temperature of 200 to 400 ° C. at the time of bonding in order to obtain sufficient shear strength. There was a problem that I could not. In addition, when the nano-sized fine particles are used alone like the bonding material disclosed in Patent Document 2, the bonding stability is low such that the bonding material thickens due to the aggregation of the particles over time. There was a problem. When the viscosity of the bonding material increases, it becomes difficult to uniformly apply the bonding material to the surface of the component.

  The present invention has been made in view of the above circumstances, and it is possible to form a bonding layer having high shear strength even by a heat treatment at a temperature lower than the conventional heating temperature, and store for a long time. Even if it is difficult to increase the viscosity and has a high storage stability, a bonding material and a method for manufacturing a bonded body using the bonding material are provided.

In order to solve the above problems, the present invention adopts the following configurations.
[1] Silver powder having a particle size distribution of primary particles having a first peak within a particle size range of 20 to 70 nm and a second peak within a particle size range of 200 to 500 nm;
An alkylamine having 6 to 10 carbon atoms and having a molecular weight in the range of 101.19 to 157.30;
Butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, viewed contains a non-amine based organic solvent of at least one selected from the group consisting of methyl pentanediol and terpineol,
A bonding material , wherein the silver powder contains secondary particles formed by agglomeration of primary particles, and the particle diameter of the secondary particles is 10 μm or less .

[2] The bonding material according to item 1 above, wherein the content of the silver powder is in the range of 70 to 90 mass%.

[3] The mass ratio A / B between the content A of the alkylamine and the content B of the non-amine organic solvent is in the range of 0.1 to 19, wherein the preceding item 1 or the preceding item 2 The bonding material described in.

[ 4 ] A method for manufacturing a joined body, in which a first member and a second member are joined via a joining layer, wherein the joining material is used to form the joining layer. Manufacturing method.

  In the bonding material of the present invention, the particle size distribution of primary particles has a silver powder having a first peak within a particle size range of 20 to 70 nm and a second peak within a particle size range of 200 to 500 nm, and a carbon number of 6. -10 and an alkylamine having a molecular weight in the range of 101.19 to 157.30, and selected from the group consisting of butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, methyl pentanediol and terpineol. Since it contains at least one non-amine organic solvent, it is possible to form a bonding layer having high shear strength even by heat treatment at a temperature lower than the conventional heating temperature, and thicken even after long-term storage. It is hard to do and has high storage stability.

It is a figure for demonstrating the manufacturing method of the joining material which is embodiment which applied this invention. It is a figure for demonstrating the manufacturing method of the joining material which is embodiment which applied this invention. It is a schematic cross section of the joined body which is an embodiment to which the present invention is applied.

  Hereinafter, a method for manufacturing a bonding material and a bonded body, which is an embodiment to which the present invention is applied, will be described in detail. In addition, in the drawings used in the following description, in order to make the characteristics easy to understand, the characteristic portions may be enlarged for convenience, and the dimensional ratios and the like of the respective components are not necessarily the same as the actual ones. Absent.

<Bonding material>
First, the structure of a bonding material, which is an embodiment to which the present invention is applied, will be described. The bonding material of this embodiment is composed of silver powder and a solvent. Here, the silver powder is assumed to be composed of pure silver and a silver alloy containing silver as a main component (the content of silver is 99% by mass or more).
The joining material of the present embodiment can form a joining layer by heat treatment and join two or more adjacent objects to be joined. The joining material of the present embodiment can join the objects to be joined even by a heat treatment at a temperature lower than the conventional heating temperature, and thus can join materials that are weak against heat.

The shape of the silver powder is not particularly limited, but specific examples thereof include a spherical shape, a rod shape, and a scaly shape.
Regarding the particle size, 1,000 or more primary particles were observed with a scanning electron microscope, and the SEM image was binarized using the image processing software "ImageJ (developed by the National Institutes of Health)", and the boundary between particles and other particles After determining, the area of each particle was calculated from the number of pixels, and this was converted into a true circle to obtain the primary particle diameter of each particle. The upper two values having the largest number of particle sizes were calculated, and the smaller one was defined as the particle size of the first peak, and the larger one was defined as the particle size of the second peak.

  The silver powder has a particle size distribution within a predetermined range. As the particle size distribution of the primary particles of silver powder, specifically, for example, the particle size has a first peak within a range of 20 to 70 nm, preferably 30 to 50 nm, and a particle size of 200 to 500 nm, preferably 300 to 400 nm. Has a second peak within the range.

  When the first peak is 20 nm or more, it is possible to form the bonding layer having a sufficient thickness to maintain the bonding during the heat treatment. When the first peak is 70 nm or less, the filling degree of silver in the bonding layer can be increased.

  Further, when the second peak is 200 nm or more, a bonding layer having a thickness sufficient to maintain bonding can be formed during heat treatment. When the second peak is 500 nm or less, the filling degree of silver in the bonding layer can be increased.

  Further, when the particle size distribution of the primary particles falls within the above range, the filling degree of the silver powder inside the bonding material can be increased after the bonding material is applied to the surface of the material to be bonded. Therefore, when heat-treated, the silver powder can be uniformly and sufficiently sintered inside the bonding layer. As a result, the filling degree of silver in the bonding layer is increased, and the shear strength of the bonding layer is improved.

  The particle size distribution of the primary particles can be measured, for example, by observing silver powder with a commercially available scanning electron microscope (SEM, for example, "S-4300SE" manufactured by Hitachi High-Technologies Corporation), and the particle size of 1000 or more silver particles. Can be measured. Here, the top two values having the largest number of particle sizes were calculated, and the smaller one was defined as the particle size of the first peak, and the larger one was defined as the particle size of the second peak.

  The primary particles of silver powder may form secondary particles (aggregated particles). The particle size of the secondary particles is preferably 10 μm or less. When the particle diameter of the secondary particles is within the above range, generation of voids is suppressed when the bonding layer is formed, and a bonding layer having high strength can be obtained.

  The particle size of the secondary particles can be evaluated using, for example, a grind gauge (JIS K 5600-2-5). Thereby, the upper limit of the particle size of the secondary particles contained in the binder can be obtained.

  It is preferable that the surface of the silver powder is mainly coated with an organic substance such as an organic molecule having 4 or less carbon atoms. Specifically, the organic substance that coats the silver powder is preferably, for example, one that decomposes at 150 ° C. by 50% by mass or more, and more preferably one that decomposes at 150 ° C. by 75% by mass or more.

  When the organic substance coating the silver powder is decomposed by 50% by mass or more at 150 ° C., the silver powder is easily sintered and the shear strength of the bonding layer is improved.

  The decomposition rate of the organic substance coating the silver powder can be measured, for example, by holding the silver powder in the air at a predetermined temperature for a predetermined time, and then measuring the mass reduction amount after heating with respect to before heating. .

  It is preferable that the silver powder generate gas when heated. Specifically, for example, it is preferable that when carbon powder in a powder state is heated at 100 ° C., gaseous carbon dioxide, an evaporated product of acetone, an evaporated product of water, and the like are generated.

  The gas is derived from the organic molecules adsorbed on the surface of the silver powder, and the lower the molecular weight, the easier the gas is to separate and separate from the surface of the silver powder by heating. Therefore, the silver powder that generates the gas is easily sintered, and the shear strength of the bonding layer is improved.

  The gas generated when the silver powder is heated is identified by, for example, a commercially available pyrolysis gas chromatograph mass spectrometer (pyrolysis GC / MS, GC / MS in which a pyrolysis device is installed in a portion to which the silver powder is introduced, for example, This can be performed by analyzing the gas using "PY-3030" manufactured by Frontier Laboratories, "JMS-T100GCV" manufactured by JEOL Ltd.).

  In the bonding material of the present embodiment, as a solvent, an alkylamine and a non-amine organic solvent are used in combination.

The alkylamine has a protective effect of coating the surface of the silver particles and preventing the aggregation of the silver particles. When the carbon number of the alkylamine (the carbon number of the alkyl group of the alkylamine) is less than 6, the protective action becomes low. On the other hand, when the alkylamine has more than 10 carbon atoms, the protective effect of the silver powder becomes too strong, and it becomes difficult for the silver particles to sinter during the heat treatment and the bonding layer of the bonded body may become fragile.
Therefore, the alkylamine used in the bonding material of the present embodiment has a carbon number of 6 to 10 and a molecular weight of 101.19 to 157.30. The alkylamine having 6 to 10 carbon atoms is easily desorbed from the silver powder by heating. For this reason, voids (air bubbles) due to desorption of alkylamine are less likely to occur in the bonding layer of the bonded body manufactured using the bonding material of the present embodiment.

  The alkylamine may be any of primary alkylamine, secondary alkylamine and tertiary alkylamine, but is preferably primary alkylamine or secondary alkylamine, and primary alkylamine is More preferable. The alkyl group of the alkylamine may be linear, branched or cyclic, but is preferably linear or branched. Examples of alkylamines include 2-ethylhexylamine, hexylamine, and decylamine. The alkylamines may be used alone or in combination of two or more.

  The non-amine organic solvent used in the bonding material of the present embodiment is at least one organic solvent selected from the group consisting of butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, methylpentanediol and terpineol. These organic solvents may be used alone or in combination of two or more. These organic solvents have an affinity for the alkyl group of alkylamine. Therefore, the silver particles to which the alkylamine is attached are stably maintained in a state of being dispersed in the non-amine organic solvent.

  The bonding material of the present embodiment is a paste because it is formed by mixing the above-mentioned silver powder and a solvent. Therefore, it can be applied to the surface of the article to be joined.

  The amount of silver powder contained in the bonding material is not particularly limited as long as it is a ratio capable of maintaining the paste state. Specifically, the content of silver powder is preferably in the range of 70 to 90 mass%.

  If the content of silver powder in the bonding material is less than the lower limit value, a film having high strength cannot be obtained, and if it exceeds the upper limit value, film cracking is likely to occur.

The contents of the alkylamine and the non-amine organic solvent which are the solvents are such that the mass ratio A / B of the content A of the alkyl amine and the content B of the non-amine organic solvent is in the range of 0.1 to 19. Is preferred.
When the mass ratio A / B is less than 0.1, the silver particles are likely to aggregate, the silver powder and the solvent are solid-liquid separated, and there is a possibility that the fluctuation in viscosity during storage becomes large. On the other hand, if the mass ratio A / B exceeds 19, the viscosity may increase during storage. It is considered that this is because the alkylamine as a protective agent is excessively present, resulting in overdispersion during paste kneading, producing fine silver particles, and the fine silver particles reaggregating during storage. .

  Since the bonding material of the present embodiment contains the silver powder and the solvent described above, it is possible to form a bonding layer having a high shear strength of 20 MPa or more even by heat treatment at a low temperature of 150 to 200 ° C. Therefore, even materials that are weak against heat can be joined.

  Here, in the conventional bonding material, a bonding layer having a shear strength of about 20 MPa is generally formed by heat treatment at 200 to 400 ° C. On the other hand, in the joining material of the present embodiment, when the heat treatment is performed at 200 ° C., the joining layer having a high shear strength of 40 MPa or more can be formed.

Next, a method for manufacturing the above-mentioned bonding material will be described with reference to FIGS.
First, as shown in FIG. 1, a silver carboxylate aqueous solution 1 and a carboxylate aqueous solution 2 are simultaneously dropped into water 3 to prepare a silver carboxylate slurry 4.

  Here, when preparing the silver carboxylate slurry 4, it is preferable to maintain the temperature of each of the liquids 1 to 4 at a predetermined temperature within the range of 20 to 90 ° C. By maintaining the temperature of each of the liquids 1 to 4 at a predetermined temperature of 20 ° C. or higher, silver carboxylate is easily produced and the particle size of the silver powder can be increased. Further, by keeping the temperature of each of the liquids 1 to 4 at a predetermined temperature of 90 ° C. or lower, it is possible to prevent the silver powder from becoming coarse particles.

  Further, it is preferable that the water 3 is stirred while the silver salt aqueous solution 1 and the carboxylate aqueous solution 2 are simultaneously dropped into the water 3.

  As the silver salt in the silver salt aqueous solution 1, specifically, for example, one kind or two or more kinds of compounds selected from the group consisting of silver nitrate, silver chlorate, silver phosphate, and salts thereof are preferable.

  The carboxylic acid in the carboxylic acid salt aqueous solution 2 is one or two selected from the group consisting of glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid, tartaric acid, and salts thereof. One or more compounds are preferred.

  Examples of the water 3 include ion exchanged water and distilled water. It is particularly preferable to use ion-exchanged water because it does not contain ions that may adversely affect the synthesis and the production cost is lower than that of distilled water.

  Next, as shown in FIG. 2, a reducing agent aqueous solution 5 is dropped on the silver carboxylate slurry 4 and a predetermined heat treatment is performed to prepare a silver powder slurry.

  Here, as the predetermined heat treatment, specifically, for example, in water, the temperature is raised to a predetermined temperature (maximum temperature) within the range of 20 to 90 ° C. at a heating rate of 15 ° C./hour or less, and the maximum It may be a heat treatment in which the temperature is maintained for 1 to 5 hours and then the temperature is lowered to 30 ° C. or lower over 30 minutes or less.

  In the above predetermined heat treatment, by setting the temperature rising rate to 15 ° C./hour or less, it is possible to prevent the silver powder from becoming coarse particles.

  Further, in the above predetermined heat treatment, by setting the maximum temperature to 20 ° C. or higher, silver carboxylate is easily reduced, and the particle size of silver powder can be increased. Moreover, by setting the maximum temperature to 90 ° C. or lower, it is possible to prevent the silver powder from becoming coarse particles.

  Further, in the above predetermined heat treatment, by setting the holding time at the maximum temperature to 1 hour or more, silver carboxylate is easily reduced, and the particle size of silver powder can be increased. Further, by setting the holding time to 5 hours or less, it is possible to prevent the silver powder from becoming coarse particles.

  Further, in the above-mentioned predetermined heat treatment, by setting the temperature to 30 ° C. for 30 minutes or less, it is possible to prevent the silver powder from becoming coarse particles.

  When preparing the silver powder slurry, it is preferable to maintain the temperature of each of the liquids 4 and 5 at a predetermined temperature within the range of 20 to 90 ° C. By maintaining the temperature of each of the liquids 4 and 5 at a predetermined temperature of 20 ° C. or higher, the silver carboxylate is easily reduced and the particle size of the silver powder can be increased. Further, by keeping the temperature of each of the liquids 4 and 5 at a predetermined temperature of 90 ° C. or lower, it is possible to prevent the silver powder from becoming coarse particles.

  The reducing agent in the reducing agent aqueous solution 5 is preferably one or more compounds selected from the group consisting of hydrazine, ascorbic acid, oxalic acid, formic acid, and salts thereof.

  Next, the silver powder slurry is dried to obtain silver powder. Here, before drying the silver powder slurry, it is preferable to remove the liquid phase in the silver powder slurry with a centrifuge to dehydrate and desalt the silver powder slurry.

  The method for drying the silver powder slurry is not particularly limited, and specific examples thereof include a freeze drying method, a reduced pressure drying method, and a heat drying method. The freeze-drying method is a method in which a silver powder slurry is put in a closed container to be frozen, and the inside of the closed container is decompressed by a vacuum pump to lower the boiling point of the dried object, and the water of the dried object is sublimated at a low temperature to dry. is there. The reduced pressure drying method is a method in which the material to be dried is dried under reduced pressure. The heat drying method is a method of heating to dry the material to be dried.

  Next, the bonding material is manufactured by mixing the generated silver powder, an alkylamine, and a non-amine-based organic solvent. The mixing method is not particularly limited, a method of simultaneously mixing silver powder, an alkylamine and a non-amine organic solvent, a method of mixing a mixture containing silver powder and an alkylamine and a non-amine organic solvent, a silver powder and a non-amine organic solvent. Either a method of mixing a mixture containing a solvent with an alkylamine or a method of mixing a mixture containing an alkylamine and a non-amine organic solvent with silver powder may be used.

<Jointed body>
Next, a method for manufacturing a joined body, which is an embodiment to which the present invention is applied, will be described with reference to FIG. FIG. 3 shows the joined body 11 of the present embodiment. As shown in FIG. 3, the bonded body 11 of the present embodiment includes a substrate 12, a first metal layer 13, a bonding layer 14, a second metal layer 15, and an article 16 to be bonded. It is roughly configured.

  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 bonding material described above will be described. There is no particular limitation on what is joined by joining.

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

  The first metal layer 13 is laminated adjacent to the substrate 12. The substrate 12 and the bonding layer 14 are bonded to each other via the first metal layer 13. As a material for the first metal layer 13, specifically, 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 adjacently laminated 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 and forms the interface 17. The bonding layer 14 is in contact with the second metal layer 15 to form the interface 18. The bonding layer 14 is formed by applying the above-described bonding material on the first metal layer 13, placing the object 16 to be bonded so that the applied surface faces the second metal layer 15, and performing heat treatment. It is something.

  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, it may be, for example, 1 to 100 μm.

The second metal layer 15 is the bonding layer 14 and is laminated adjacent to the opposite side of the first metal layer 13. The bonding layer 14 and the article 16 to be bonded are bonded to each other 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 article to be joined 16 is the second metal layer 15 and is laminated adjacent to the opposite side of the joining layer 14. The object to be bonded 16 is not particularly limited, but specific examples thereof include silicon (Si) and silicon carbide (SiC). In addition, since the joined body 11 of the present embodiment uses the above-described joining material, a material that is weak against heat can be used as the article 16 to be joined.

  In the joined body 11 of this embodiment, the substrate 12 and the article 16 are joined by the joining layer 14. Since the bonding layer 14 is formed using the above-mentioned bonding material, the shear strength of the bonding layer 14 is high. Specifically, the shear strength of the bonded body 11 of the present embodiment is, for example, preferably 20 MPa or more, and more preferably 30 MPa or more.

  The shear strength can be measured using, for example, a commercially available bonding tester (for example, manufactured by RHESCA).

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

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

  Next, the bonding material described above is applied to the surface of the first metal layer 13 by a known method. The method of applying the bonding material on 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 article 16 to be joined is placed on the joining material applied to the surface of the first metal layer 13 such that the second metal layer 15 sides face each other. After that, by performing heat treatment, the 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 in the heat treatment is not particularly limited, but specifically, for example, 150 ° C. or higher is preferable. When the heating temperature is 150 ° C. or higher, the shear strength of the bonding layer 14 can be increased.

The heating time in 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 shear strength of the bonding layer 14 can be increased.
The bonded body 11 is manufactured through the above steps.

  As described above, according to the bonding material of the present embodiment, the particle size distribution of the primary particles has the first peak in the range of particle size 20 to 70 nm and the second peak in the range of particle size 200 to 500 nm. A silver powder having, an alkylamine having a carbon number of 6 to 10 and a molecular weight of 101.19 to 157.30, and butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, methyl. It contains at least one non-amine organic solvent selected from the group consisting of pentanediol and terpineol. Therefore, the bonding layer having high shear strength can be formed even by the heat treatment at a temperature lower than the conventional heating temperature. Further, the bonding material of the present embodiment does not easily increase in viscosity even when stored for a long period of time, and has high storage stability.

  Furthermore, according to the joining material of the present embodiment, when the heat treatment at 200 ° C. is performed, it is possible to form the joining layer having a high shear strength of 40 MPa or more.

  Further, according to the joined body 11 of the present embodiment, since it is formed using the joining material described above, it has a joining layer having a shear strength of 20 MPa or more.

  Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and includes a design and the like within a range not departing from the gist of the present invention. For example, although the bonded body 11 described above has been described with respect to the example including the first metal layer 13 and the second metal layer 15, the invention is not limited to this. For example, one or both of the first metal layer 13 and the second metal layer 15 may be omitted.

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

<Synthesis of silver powder>
(Category I)
First, as shown in FIG. 1, 1200 g of ion-exchanged water (water 3) kept at 50 ° C., 900 g of silver nitrate aqueous solution (silver salt aqueous solution 1) kept at 50 ° C., and 600 g of quench solution kept at 50 ° C. A sodium citrate aqueous solution (carboxylate aqueous solution 2) was simultaneously added dropwise over 5 minutes to prepare a silver citrate slurry (silver carboxylate slurry 4).

  Note that while the silver nitrate aqueous solution (silver salt aqueous solution 1) and the sodium citrate aqueous solution (carboxylate aqueous solution 2) were simultaneously dropped into the ion-exchanged water (water 3), the ion-exchanged water (water 3) was continuously stirred. It was The concentration of silver nitrate in the silver nitrate aqueous solution (silver salt aqueous solution 1) was 66% by mass, and the concentration of citric acid in the sodium citrate aqueous solution (carboxylic acid salt aqueous solution 2) was 56% by mass.

  Then, as shown in FIG. 2, 300 g of the sodium oxalate aqueous solution (reducing agent aqueous solution 5) held at 50 ° C. was added to the silver citrate slurry (silver carboxylate slurry 4) held at 50 ° C. over 30 minutes. The mixture was dropped to obtain a mixed slurry. The concentration of oxalic acid in this sodium oxalate (reducing agent aqueous solution 5) was 58% by mass.

  Next, a predetermined heat treatment was performed on the mixed slurry. Specifically, the temperature of the mixed slurry was raised to a maximum temperature of 70 ° C. at a heating rate of 10 ° C./hour, held at 70 ° C. (maximum temperature) for 2 hours, and then lowered to 30 ° 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 phase in the silver powder slurry was removed, and a dehydrated and desalted silver powder slurry was obtained.

  The dehydrated and desalted silver powder slurry was dried for 30 hours by a freeze-drying method to obtain a silver powder of Class I.

(Category II)
A silver powder of Class II was obtained in the same manner as Class I except that a mixed slurry was prepared while maintaining the temperature of each liquid at 80 ° C., and the maximum temperature during heat treatment was 80 ° C.

(Category III)
Classification was made except that a mixed slurry was prepared while maintaining the temperature of each liquid at 30 ° C., and the temperature rising rate during heat treatment was 0 ° C./hour, the maximum temperature was 30 ° C., and the holding time was 5 hours. Silver powder of Class III was obtained in the same manner as in I.

(Category IV)
Classification was made except that a mixed slurry was prepared while maintaining the temperature of each liquid at 15 ° C, and the temperature rising rate during heat treatment was 0 ° C / hour, the maximum temperature was 15 ° C, and the holding time was 5 hours. In the same manner as in I, silver powder of Class IV was obtained.

(Category V)
A silver powder of Class V was obtained in the same manner as in Class I except that the holding time during the heat treatment was 8 hours.

(Classification VI)
As the silver powder of classification VI, commercially available silver powder (“SPQ03S” manufactured by Mitsui Metal Industry Co., Ltd.) was prepared.

<Evaluation of silver powder>
The particle size distribution of primary particles of the silver powders of classifications I to IV, the decomposition rate of the organic material coating the silver powder at a predetermined temperature (decomposition rate of organic matter), and the organic material coating the silver powder is generated when the silver powder in the powder state is heated. The type of gas (heat generated gas type) was measured.

  The particle size distribution of primary particles of the silver powder was measured by observing the silver powder with an SEM (“S-4300SE” manufactured by Hitachi High-Technologies Corporation) and measuring the particle size of 1000 silver particles. Here, the top two values having the largest number of particle sizes were calculated, and the smaller one was defined as the particle size of the first peak, and the larger one was defined as the particle size of the second peak. Table 1 shows the particle sizes of the first peak and the second peak.

  The decomposition rate of the organic substance was obtained by holding the silver powder in the atmosphere at 150 ° C. for 30 minutes and then measuring the amount of mass reduction after heating with respect to before heating.

  The heat-generated gas species was identified by analyzing the gas generated using pyrolysis GC / MS (“PY-3030” manufactured by Frontier Lab, “JMS-T100GCV” manufactured by JEOL Ltd.).

The results of each measurement are shown in Table 1 below. In Table 1, the time for simultaneously dropping the aqueous solution of silver nitrate and the aqueous solution of ammonium citrate, the heating rate and maximum temperature of the silver powder slurry obtained by dropping the aqueous solution of ammonium formate on the silver citrate slurry, and the holding temperature of each solution The type of reducing agent aqueous solution is also described. Further, among the heat-generated gas species in Table 1, CO ₂ is gaseous carbon dioxide, and acetone, water, ethanediol, acetic acid, and pyrrole are evaporation products of these.

<Preparation of bonding material>
(Example 1)
Class I silver powder, 2-ethylhexylamine (molecular weight: 129.24), and butyl carbitol acetate were put in a container in a compounding amount of 85: 5: 15 by mass ratio, and kneader (made by THINKY, "Awawa" The joining material was obtained by performing kneading for 3 minutes by rotating at a rotation speed of 2000 rpm for 5 minutes.

(Example 2)
A bonding material was obtained in the same manner as in Example 1 except that the silver powder of Class II was used.

(Example 3)
A bonding material was obtained in the same manner as in Example 1 except that the silver powder of Class III was used.

(Example 4)
A bonding material was obtained in the same manner as in Example 1 except that dipropylene glycol monomethyl ether was used as the non-amine organic solvent.

(Example 5)
A bonding material was obtained in the same manner as in Example 1 except that butyl carbitol was used as the non-amine organic solvent.

(Example 6)
A bonding material was obtained in the same manner as in Example 1 except that methylpentanediol was used as the non-amine organic solvent.

(Example 7)
A bonding material was obtained in the same manner as in Example 1 except that terpineol was used as the non-amine organic solvent.

(Example 8)
A bonding material was obtained in the same manner as in Example 1 except that hexylamine (molecular weight: 101.19) was used as the alkylamine.

(Example 9)
A bonding material was obtained in the same manner as in Example 1 except that decylamine (molecular weight: 157.30) was used as the alkylamine.

(Example 10)
A bonding material was obtained in the same manner as in Example 1 except that the amounts of silver powder, 2-ethylhexylamine, and butyl carbitol acetate mixed were 70:10:20.

(Example 11)
A bonding material was obtained in the same manner as in Example 1 except that the compounding amounts of silver powder, 2-ethylhexylamine, and butyl carbitol acetate were 90: 2: 8.

(Example 12)
A bonding material was obtained in the same manner as in Example 1 except that the compounding amounts of silver powder, 2-ethylhexylamine and butyl carbitol acetate were 80: 19: 1.

(Example 13)
A bonding material was obtained in the same manner as in Example 1 except that the compounding amounts of silver powder, 2-ethylhexylamine, and butyl carbitol acetate were 80: 2: 18.

(Comparative Example 1)
A bonding material was obtained in the same manner as in Example 1 except that the silver powder of Class IV was used.

(Comparative example 2)
A bonding material was obtained in the same manner as in Example 1 except that the silver powder of Class V was used.

(Comparative Example 3)
A bonding material was obtained in the same manner as in Example 1 except that silver powder of Class VI was used.

(Comparative example 4)
A bonding material was obtained in the same manner as in Example 1 except that water was used instead of the non-amine organic solvent.

(Comparative example 5)
A bonding material was obtained in the same manner as in Example 1 except that ethanol was used as the non-amine organic solvent.

(Comparative example 6)
A bonding material was obtained in the same manner as in Example 1 except that butylamine (molecular weight: 73.14) was used as the alkylamine.

(Comparative Example 7)
A bonding material was obtained in the same manner as in Example 1 except that dodecylamine (molecular weight: 185.35) was used as the alkylamine.

(Comparative Example 8)
A bonding material was obtained in the same manner as in Example 1 except that 2-ethylhexylamine was not added and the compounding amounts of silver powder and butyl carbitol acetate were 80:20.

  Table 2 below shows the silver powder, the alkylamine, and the non-amine organic solvent used for the preparation of the bonding materials of Examples and Comparative Examples, and the compounding amounts thereof. Regarding the silver powder, the particle sizes of the first peak and the second peak are also shown together.

  Moreover, the upper limit of the particle size of the secondary particles of the silver powder was measured for the bonding materials obtained in each of the examples and each of the comparative examples using a grind gauge (grindometer manufactured by TQC). The measurement is performed according to the method specified in JIS K 5600-2-5, the gauge value when three or more streaks derived from the secondary particles are generated on the gauge, and the value of the gauge is read. Was set as the upper limit value of the particle size. Table 2 shows the results.

<Evaluation of bonding material>
Regarding the bonding materials of Examples 1 to 13 and Comparative Examples 1 to 8, the presence or absence of solid-liquid separation and the change in viscosity were evaluated. However, the bonding material of Comparative Example 4 could not be evaluated because it was not made into a paste.

  The presence or absence of solid-liquid separation was determined by visually observing the bonding material immediately after preparation. The bonding material in which solid-liquid separation did not occur was designated as “OK”, and the bonding material in which solid-liquid separation occurred was designated as “impossible”. The results are shown in Table 3.

  The viscosity change was measured by measuring the viscosity X of the bonding material immediately after preparation and the viscosity Y of the bonding material after being stored in a temperature environment of 10 ° C. for 7 days, and calculating the change rate (Y / X × 100) of the viscosity. Evaluated by asking. A bonding material having a viscosity change rate of 5% or less was designated as "OK" and a bonding material having a viscosity change rate of more than 5% was designated as "NG". The viscosity was measured using a rheometer, and the shear rate at the time of viscosity measurement was 10 [1 / s]. The results are shown in Table 3.

<Production and evaluation of bonded body>
Using the joining materials of Examples 1 to 13 and Comparative Examples 1 to 3 and 5 to 8, joined bodies were produced by the following method.
A plate in which an aluminum plate was covered with silver was prepared as a substrate, and a bonding material was printed and formed on the silver using a metal mask (hole size: vertical 3 mm × horizontal 3 mm × thickness 50 μm). Next, a silicon chip whose surface is coated with silver (size: 2.5 mm length × 2.5 mm width × 200 μm thickness) is placed on the bonding material, and the temperature is maintained at 150 ° C. for 30 minutes in the air atmosphere. By doing so, firing was performed. As a result, a bonding layer was formed between the substrate and the silicon chip, and a bonded body was obtained.

  The shear strength of the bonding layer formed between the substrate of the manufactured bonded body and the silicon chip was measured. The shear strength is measured by a bonding tester (manufactured by RHESCA) for the force required to break the bonding layer formed between the substrate and the silicon chip, and this measured value is divided by the bonding area to obtain shear strength. . The results are shown in Table 3.

  In addition, in the evaluation of the bonding material, the presence or absence of solid-liquid separation and the viscosity suppression are both “OK”, and the shear strength of the bonded body exceeds 20 MPa is judged as “◯”, and one or more of them are evaluated. Those that did not satisfy were judged as "x". The determination result is shown in Table 3.

  The viscosity of the bonding material of Comparative Example 1 in which the first and second peaks of the particle size distribution of the primary particles were smaller than the lower limit of the present invention was incapable of changing the viscosity. It is considered that this is because the primary particles of the silver powder were small and thus the aggregation of the silver powder proceeded during storage.

  The bonding material of Comparative Example 2 containing silver powder in which the first peak and the second peak of the particle size distribution of the primary particles exceeded the upper limit of the present invention, solid-liquid separation was not possible and viscosity change was impossible. It is considered that this is because the primary particles of the silver powder were large and the particles settled to the bottom due to their own weight.

  The joint strength of the joint layer was low in the joint body prepared by using the joint material of Comparative Example 3 containing the silver powder having one particle size distribution peak of the primary particles. It is considered that this is because the packing density of the bonding layer was low and the bonding layer was fragile because the silver powder whose primary particles did not have two peaks was used.

  The bonding material of Comparative Example 4 containing water instead of the non-amine organic solvent was not made into a paste. It is considered that this is because the compatibility between water and silver powder is low. In addition, the bonding material of Comparative Example 5 containing ethanol as the non-amine organic solvent was incapable of solid-liquid separation and viscosity change. It is considered that this is because the compatibility between ethanol and silver powder is low.

  The bonding material of Comparative Example 6 containing butylamine as the alkylamine was incapable of solid-liquid separation and viscosity change. It is considered that this is because butylamine has a weak protective effect on the silver powder. On the other hand, in the joined body produced using Comparative Example 7 containing dodecylamine as the alkylamine, the shear strength of the joining layer was low. It is considered that this is because dodecylamine has a too strong silver powder protecting effect, so that sintering does not proceed and the bonding layer is fragile.

  Furthermore, the bonding material of Comparative Example 8 containing no alkylamine was incapable of solid-liquid separation and viscosity change. It is considered that this is because the dispersibility of the silver powder was reduced.

  On the other hand, the particle size distribution of the primary particles is a silver powder having a first peak in the range of 20 to 70 nm and a second peak in the range of 200 to 500 nm, and a carbon number of 6 to 10. And an alkylamine having a molecular weight of 101.19 to 157.30 and at least one non-amine selected from the group consisting of butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, methyl pentanediol and terpineol. In the bonding materials of Examples 1 to 13 containing the organic solvent, solid-liquid separation does not occur and the viscosity change is suppressed. Further, the bonded body produced using this bonding material had excellent shear strength.

  INDUSTRIAL APPLICABILITY The bonding material of the present invention may be used as a bonding material when bonding an electronic component or the like on a substrate.

1 ... Silver salt aqueous solution 2 ... Carboxylate aqueous solution 3 ... Water 4 ... Silver carboxylate slurry 5 ... Reducing agent aqueous solution 11 ... Bonding body 12 ... Substrate 13 ... First metal layer 14 ... Bonding layer 15 ... Second metal layer 16 ... Object to be bonded 17, 18 ... Interface

Claims (4)

A silver powder having a particle size distribution of primary particles having a first peak within a particle size range of 20 to 70 nm and a second peak within a particle size range of 200 to 500 nm;
An alkylamine having 6 to 10 carbon atoms and having a molecular weight in the range of 101.19 to 157.30;
Butyl carbitol acetate, dipropylene glycol monomethyl ether, butyl carbitol, viewed contains a non-amine based organic solvent of at least one selected from the group consisting of methyl pentanediol and terpineol,
A bonding material , wherein the silver powder contains secondary particles formed by agglomeration of primary particles, and the particle diameter of the secondary particles is 10 μm or less .   The bonding material according to claim 1, wherein the content of the silver powder is in the range of 70 to 90% by mass. The mass ratio A / B of the content A of the alkylamine and the content B of the non-amine-based organic solvent is in the range of 0.1 to 19, 3. Bonding material.   A method for manufacturing a bonded body, in which a first member and a second member are bonded together via a bonding layer, wherein the bonded material is formed using the bonding material according to claim 1. Method.

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