JP2018168458A - Silver powder, silver powder manufacturing method, paste-like composition, joined body manufacturing method, and silver film manufacturing method - Google Patents

Abstract

The present invention provides a silver powder and a method for producing silver powder, which can form a dense sintered body by heating at a lower temperature than in the past.
In time-of-flight secondary ion mass spectrometry, the detected amount of C ₃ H ₃ O ₃ ⁻ ions is 0.2 to 1.0 times the detected amount of Ag ⁺ ions, and C ₆ H ₆ O ₈ ^- is in the range detection amount less 0.02 times 0.005 times the ion content of the primary particles is in the number distribution of the primary particle size in the range particle size of 20nm or more 50nm or less The silver powder is characterized in that the content of primary particles having a particle size of 200 nm or more and 500 nm or less is 3 number% or more.
[Selection figure] None

Description

  The present invention relates to, for example, a silver powder used as a bonding material for bonding a circuit board and an electronic component or a raw material for an electrode of a solar cell element, and a method for producing the silver powder. The present invention also relates to a paste-like composition containing the above silver powder, a method for producing a joined body using the paste-like composition, and a method for producing a silver film.

  It is known that a fine metal powder composed of metal nanoparticles having a nano particle size can be sintered at a temperature lower than the original melting point of the metal. In particular, since fine silver powder has high conductivity and heat dissipation, it attracts attention as a raw material for bonding materials for bonding circuit boards and electronic components such as semiconductor chips and LED elements, and electrodes for solar cell elements. .

  In Patent Document 1, as a method for producing metal nanoparticles having a nano particle size, a metal salt aqueous solution (A), a carboxylic acid aqueous solution (B), and a reducing agent aqueous solution (C) are prepared, and carboxylic acids, respectively. A step of mixing the aqueous solution (B) with either the aqueous metal salt solution (A) or the reducing agent aqueous solution (C) to form a mixed solution, and the mixed solution with the aqueous metal salt solution (A) or the reducing agent aqueous solution (C And a step of generating metal nanoparticles by adding the other and mixing them.

  In Patent Document 2, as a bonding material using metal nanoparticles, metal submicron particles having an average primary particle size of 0.5 to 3.0 μm, an average primary particle size of 1 to 200 nm, and a carbon number A bonding material including metal nanoparticles coated with 6 to 8 organic compounds and a dispersion medium for dispersing them is disclosed.

JP 2009-191354 A JP 2011-80147 A

  With the recent miniaturization and higher functionality of electrical equipment, higher integration of semiconductor elements has been promoted, and the amount of heat generated in the semiconductor elements tends to increase. For this reason, in the bonding material using metal nanoparticles, it is desired that a dense sintered body (bonding layer) with few voids can be formed by heating at as low a temperature as possible. By making a dense sintered body, the substrate circuit and the semiconductor element can be bonded with high bonding strength, and since the thermal conductivity is increased, the heat generated in the semiconductor element is easily released to the outside. Furthermore, there is an advantage that breakage due to thermal expansion and contraction hardly occurs.

  The method for producing metal nanoparticles described in Patent Document 1 is useful as a method for producing metal nanoparticles. However, the metal powder containing only metal nanoparticles has a problem that gaps are easily formed between the particles and it is difficult to form a dense sintered body.

  On the other hand, the bonding material including metal nanoparticles and metal submicron particles described in Patent Document 2 is filled with metal nanoparticles in the gaps between the metal submicron particles. Compared to, it becomes possible to form a dense sintered body. However, in the bonding material described in Patent Document 2, the metal nanoparticles are coated with an organic compound having 6 to 8 carbon atoms, and the surface state is different from that of the metal submicron particles. If it remains, the bonding strength may be reduced. Moreover, in order to remove an organic compound completely, it was necessary to heat at high temperature. Furthermore, when manufacturing the bonding material, it is necessary to prepare metal submicron particles and metal nanoparticles having different surface states and mix them with a dispersion medium, which may be complicated. It was.

  The present invention has been made in the background as described above, and an object of the present invention is to provide a silver powder and a method for producing the silver powder, which can generate a dense sintered body by heating at a lower temperature than in the past. It is said. Another object of the present invention is to provide a paste-like composition containing the above silver powder, a method for producing a joined body using the paste-like composition, and a method for producing a silver film.

In order to solve the above problems, silver powder of the present invention, in a time-of-flight secondary ion mass spectrometry, the detection amount of the Ag ⁺ ion, C ₃ H ₃ O ₃ ^- the detection of the ion 0. 2 or more and 1.0 or less, and the detected amount of C ₆ H ₆ O ₈ ⁻ ions is in the range of 0.005 or more and 0.02 or less, and the particle size is 20 nm or more in the number distribution of primary particle diameters. The content of primary particles in the range of 50 nm or less is 65 number% or more, and the content of primary particles in the range of 200 nm or more and 500 nm or less is 3 number% or more.

According to silver powder of this configuration, in a time-of-flight secondary ion mass spectrometry, C ₃ H ₃ O ₃ ^- ions and C ₆ H ₆ O ₈ ^- because it is coated with an organic compound to be detected as an ion, the length Even when stored for a long period of time, the surface does not easily change. The detected amount of C ₃ H ₃ O ₃ ⁻ ions is 0.2 to 1.0 times the detected amount of Ag ⁺ ions, and the detected amount of C ₆ H ₆ O ₈ ⁻ ions is 0.2. Since the amount of the organic compound covering the particle surface is small in the range of 005 times to 0.02 times, the organic compound disappears and the surface of the silver particles is exposed by heating at a low temperature. Sintering between particles is promoted.

Further, the silver powder having the above-described configuration has a primary particle size content of 65% by number or more in the number distribution of primary particle sizes, in which the particle size is in the range of 20 nm to 50 nm, and the particle size is relatively small. Since the content of primary particles having a particle size in the range of 200 nm to 500 nm and having a relatively large particle size is 3% by number or more, the sintered body obtained by heating has a relatively particle size. A large primary particle is packed with primary particles having a relatively small particle size, and the particle becomes dense.
Therefore, according to the silver powder having the above-described configuration, a dense sintered body can be formed by heating at a lower temperature than conventional.

Here, in the silver powder of the present invention, in the primary particle diameter number distribution, the total of primary particles having a particle diameter in the range of 20 nm to 50 nm and primary particles having a particle diameter in the range of 200 nm to 500 nm. The content is preferably 85% by number or more.
In this case, most of the primary particles of the silver powder are primary particles having a relatively small particle size in the range of 20 nm to 50 nm and a relatively large particle size in the range of 200 nm to 500 nm. Since it becomes a primary particle, the sintered compact obtained by heating can be reliably densified.

  The method for producing silver powder of the present invention comprises a step of simultaneously dropping a silver salt aqueous solution and a carboxylic acid or carboxylate aqueous solution into water to produce silver carboxylate particles to prepare a silver carboxylate slurry; A step of preparing a silver powder slurry by dropping the aqueous reducing agent solution into the acid silver slurry and then reducing the carboxylate silver particles to produce silver particles by holding at a temperature in the range of 92 ° C. to 95 ° C. And a step of drying the silver powder slurry to obtain silver powder.

According to the method for producing silver powder having this configuration, an aqueous silver salt solution and an aqueous solution of a carboxylic acid or a carboxylic acid salt are simultaneously dropped into water to produce silver carboxylate particles, so that the particle size ranges from 20 nm to 50 nm. And silver carboxylate particles each having a peak in the range of 200 nm to 500 nm. Then, after dropping the reducing agent aqueous solution into the silver carboxylate slurry containing the silver carboxylate particles, the silver carboxylate particles are reduced by holding at a temperature in the range of 92 ° C. or higher and 95 ° C. or lower. _In the number distribution of primary particle diameters covered with ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions, the particle size is in the range of 20 nm to 50 nm and the particle size is in the range of 200 nm to 500 nm. Silver particles each having a peak can be generated.

  Moreover, since the surface of the silver particle obtained by the manufacturing method of the silver powder of said structure is coat | covered with the organic compound derived from carboxylic acid, the surface of a silver particle cannot be oxidized easily and aggregation becomes difficult to occur. Furthermore, the obtained silver powder includes silver particles having a particle size in the range of 20 nm to 50 nm and silver particles having a particle size in the range of 200 nm to 500 nm, and the surfaces of both silver particles are compared. Since it is coated with a carboxylic acid-derived organic compound (protective agent) that decomposes at a low temperature, the protective agent is removed from the silver powder by heating at a low temperature, and sintering of the silver powder proceeds to form a dense sintered body. can do.

Here, in the method for producing silver powder of the present invention, the silver salt in the aqueous silver salt solution is one or more compounds selected from the group consisting of silver nitrate, silver chlorate and silver phosphate. Is preferred.
In this case, since silver salts such as silver nitrate, silver chlorate, and silver phosphate have high solubility in water, an aqueous solution of these silver salts and an aqueous solution of a carboxylic acid or a carboxylate should be dropped simultaneously into water. Thus, silver carboxylate particles can be reliably generated.

In the method for producing silver powder of the present invention, the carboxylic acid in the aqueous solution of the carboxylic acid or carboxylate is selected from glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid, and tartaric acid. It is preferable that it is 1 type or 2 or more types of compounds chosen from the group which consists of.
In this case, glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid and tartaric acid have a high affinity with silver and form a stable chelate (silver carboxylate) with silver. By simultaneously dropping these carboxylic acid or carboxylic acid salt aqueous solution and silver salt aqueous solution into water, silver carboxylate particles can be reliably produced. In addition, since these carboxylic acids are likely to adhere to the surface of silver powder, organic compounds detected as C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions in time-of-flight secondary ion mass spectrometry. Silver powder coated with (an organic compound derived from carboxylic acid) can be obtained.

Furthermore, in the method for producing silver powder of the present invention, the reducing agent in the reducing agent aqueous solution is one or more compounds selected from the group consisting of hydrazine, ascorbic acid, oxalic acid, formic acid and salts thereof. It is preferable that
In this case, hydrazine, ascorbic acid, oxalic acid, formic acid, and salts thereof have an excellent reducing action on silver carboxylate, so that silver particles can be reliably generated. In addition, these compounds have a high affinity with water and do not easily adhere to the surface of the silver particles produced by the reduction, so that they are not easily mixed into the silver powder.

The pasty composition of the present invention is characterized by containing the above-mentioned silver powder and a solvent.
According to the paste-like composition having this configuration, since the above-described silver powder is included, a dense sintered body can be generated by heating at a relatively low temperature.

Here, in the paste-like composition of the present invention, the solvent preferably contains an amine solvent.
In this case, the amine solvent has a high affinity with silver and uniformly protects the surface of the silver particles, so that even after storage for a long period of time, a dense sintered body is reliably generated by heating at a relatively low temperature. Can be made.

The amine solvent is preferably an alkyl amine having 6 to 10 carbon atoms and a molecular weight of 101.19 to 157.30.
In this case, since the alkylamine has a particularly high affinity with the silver powder, a dense sintered body can be more reliably generated by heating at a relatively low temperature even after storage for a long period of time.

  The method for manufacturing a joined body according to the present invention is a method for producing a joined body in which a first member and a second member are joined together via a joining layer, the first member and the second member. And a laminating step for forming a laminated body laminated via the paste-like composition described above, and sintering for heating the laminated body to dry and sinter the paste-like composition to form a bonding layer. And a process.

  According to the method for manufacturing a bonded body having this configuration, since the paste-like composition containing the above-described silver powder is used as a bonding material for generating a bonding layer, a bonded body having a high bonding strength is manufactured by heating at a lower temperature than conventional. be able to.

  The method for producing a silver film of the present invention includes a coating step of applying the paste-like composition described above to a substrate, heating the substrate coated with the paste-like composition, and drying the paste-like composition. And a sintering step of forming a silver film by sintering.

  According to the method for producing a silver film having this configuration, since the paste-like composition containing the above-described silver powder is used as the material for the silver film, a dense silver film can be produced by heating at a lower temperature than conventional.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the manufacturing method of silver powder and silver powder which can produce | generate a dense sintered compact by heating at low temperature than before. Moreover, according to this invention, it becomes possible to provide the paste-like composition containing said silver powder, the manufacturing method of a conjugate | zygote using this paste-like composition, and the manufacturing method of a silver film.

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

  Hereinafter, the silver powder and the manufacturing method of a joined body which are one 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 features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<Silver powder>
The silver powder of the present embodiment is composed of pure silver and a silver alloy containing silver as a main component (silver content is 99% by mass or more).
The silver powder of this embodiment can be used as a bonding material for bonding a circuit board and an electronic component or a raw material for an electrode of a solar cell element. The bonding material using the silver powder of the present embodiment can bond an object to be bonded even when heat treatment is performed at a temperature lower than the conventional heating temperature, so that a material that is weak against heat can be bonded.

The silver powder of this embodiment has a detection amount of C ₃ H ₃ O ₃ ⁻ ions of 0.2 times or more with respect to the detection amount of Ag ⁺ ions in time-of-flight secondary ion mass spectrometry (TOF-SIMS). 1.0 times or less, and _C 6 _H 6 _{O 8} ^- detection of ions is in the range of less than 0.02 times 0.005 times. In addition, the number distribution of primary particles has two peaks, the content of primary particles having a particle size in the range of 20 nm to 50 nm is 65% by number or more, and the particle size is in the range of 200 nm to 500 nm. The content of the primary particles is 3% by number or more. In the number distribution of primary particle diameters, the total content of primary particles having a particle diameter in the range of 20 nm to 50 nm and primary particles having a particle diameter in the range of 200 nm to 500 nm may be 85% by number or more. preferable.

C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions detected in time-of-flight secondary ion mass spectrometry are derived from an organic compound (protective agent) covering the surface of the silver particles.
C ₃ H ₃ O ₃ ^- ions and C ₆ H ₆ O ₈ ^- the detection of ions is too small, i.e. the surface activity of the amount is small becomes excessively when silver particles of the organic compound coating the silver particle surface As a result, the silver powder tends to strongly aggregate easily, so that a dense film cannot be obtained.
On the other hand, C ₃ H ₃ O ₃ ^- ions and C ₆ H ₆ O ₈ ^- the detection of the ion is too high, i.e. the amount of the organic compound coating the silver particle surface is too large, sinterability It may be necessary to increase the heating temperature for sintering the silver powder.
For the above reasons, in this embodiment, the detected amount of C ₃ H ₃ O ₃ ⁻ ions is 0.2 to 1.0 times the detected amount of Ag ⁺ ions, and C ₆ H ₆ O _8. ^- detection of ions is in the range of less than 0.02 times 0.005 times. In order to reliably improve the storage stability of silver powder and to surely reduce the sintering temperature, the detected amount of C ₃ H ₃ O ₃ ⁻ ions with respect to the detected amount of Ag + ions is 0.3 times or more and 0.00. It is preferably 5 times or less. Moreover, the organic compound adhering to the surface of the silver particles is preferable because it has a low molecular weight because it is easily lost by heating. Therefore, it is preferable that the detected amount of C ₃ H ₃ O ₃ ⁻ ions is larger than the detected amount of C ₆ H ₆ O ₈ ⁻ ions. C ₃ H ₃ O ₃ ^- detection of _ions, C ₆ H _{6 O 8} ^- is preferably in the range of 30 times 50 times or less with respect to the detection of ions.

Further, the silver powder of the present embodiment has a primary particle size distribution in which the particle size is in the range of 20 nm to 50 nm and the particle size is in the range of 200 nm to 500 nm. Primary particles having a relatively large particle size. For this reason, the sintered body obtained by heating becomes dense by filling the primary particles having a relatively small particle size in the gaps between the primary particles having a relatively large particle size.
If the amount of primary particles having a relatively small particle size becomes too small, the sintering temperature becomes high, and the number of primary particles filled in the gaps between primary particles having relatively large particle sizes becomes small. There is a possibility that it becomes difficult to manufacture the sintered body.
On the other hand, if the amount of primary particles having a relatively large particle size is too small, there are many gaps between primary particles having a relatively small particle size, which may make it difficult to produce a dense sintered body. is there.
For the above reasons, in the present embodiment, the content of primary particles having a relatively small particle size in the range of 20 nm to 50 nm is 65% by number or more, and the particle size is in the range of 200 nm to 500 nm. The content of primary particles having a relatively large particle diameter is 3% by number or more. In order to reliably manufacture a dense sintered body, the content of primary particles having a relatively small particle size is 67% by number or more, and primary particles having a relatively large particle size. The content of is preferably 5% by number or more.

  Further, in the number distribution of primary particle diameters, the total content of primary particles having a particle diameter in the range of 20 nm to 50 nm and primary particles having a particle diameter in the range of 200 nm to 500 nm is 85% by number or more. It is preferably 90% by number or more. In this case, most of the primary particles of the silver powder are primary particles having a relatively small particle size in the range of 20 nm to 50 nm and primary particles having a relatively large particle size in the range of 200 nm to 500 nm. Since it becomes particle | grains, the sintered compact obtained by heating can be ensured precisely.

Silver powder of the present embodiment, more than as flying C ₃ H ₃ O ₃ with time secondary ion mass spectrometry ^- ion and C ₆ H ₆ O ₈ ^- and each of the detected amount of ions, the number of primary particle size Preserved for a long period of time because the primary particle content in the range of 20 nm to 50 nm in particle size and the primary particle content in the range of 200 nm to 500 nm in size are determined by the distribution. Even so, oxidation and aggregation of the silver particles are unlikely to occur, and a dense sintered body can be generated by heating at a lower temperature than in the past.
The shape of the primary particle diameter of the silver powder is not particularly limited, and specific examples include a spherical shape, a rod shape, and a scale shape.

<Method for producing silver powder>
Next, the manufacturing method of the silver powder mentioned above is demonstrated with reference to FIG.
First, as shown in FIG. 1, a silver salt aqueous solution 1 and a carboxylic acid aqueous solution 2 in which a carboxylic acid or a carboxylic acid salt is dissolved are simultaneously dropped into water 3 to produce silver carboxylate particles to produce a carboxylic acid. A silver slurry 4 is prepared. In this embodiment, since the silver salt aqueous solution 1 and the carboxylic acid aqueous solution 2 are simultaneously dropped into the water 3, the silver salt concentration and the carboxylate concentration in the water 3 are lowered. For this reason, the reaction rate between the silver salt concentration and the carboxylate is slowed, and small silver carboxylate particles having a particle size of 20 nm to 50 nm and large carboxylate particles having a particle size of 200 nm to 500 nm are generated.

  The ratio of the amount of the silver salt aqueous solution 1 and the carboxylic acid aqueous solution 2 simultaneously dropped into the water 3 is the equivalent ratio of silver and carboxylic acid [= (valence of silver ions: 1 valence × number of moles) / (valence of carboxylic acid). (Number × number of moles)] is preferably in the range of 1.1 to 2.0. In this case, as the amount of free carboxylic acid increases in the water 3 as the dropping proceeds, the time from dropping the aqueous silver salt solution 1 to the formation of silver carboxylate particles is shortened. It becomes easy to produce silver carboxylate particles having a small particle size. Therefore, the particle diameter of the resulting silver carboxylate particles can be changed by the progress of the dropping, and small silver carboxylate particles having a particle diameter of 20 nm to 50 nm and large silver carboxylate particles having a particle diameter of 200 nm to 500 nm. Can be reliably generated.

  Here, when the silver carboxylate slurry 4 is prepared, it is preferable to maintain the temperatures of the liquids 1 to 4 at a predetermined temperature within a range of 20 to 50 ° C. By maintaining the temperature of each of the liquids 1 to 4 at a predetermined temperature of 20 ° C. or higher, silver carboxylate particles can be easily generated, and the particle size of the silver carboxylate particles can be increased. Moreover, it can prevent that the carboxylate silver particle grows excessively and becomes a coarse particle by hold | maintaining the temperature of each liquid 1-4 at the predetermined temperature of 50 degrees C or less.

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

  Specifically, the silver salt in the silver salt aqueous solution 1 is preferably, for example, one or more compounds selected from the group consisting of silver nitrate, silver chlorate, and silver phosphate.

  The carboxylic acid in the carboxylic acid aqueous solution 2 is preferably one or more compounds selected from the group consisting of glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid and tartaric acid. . Since these carboxylic acids form a stable chelate with silver, they are easily precipitated as silver carboxylate particles. The carboxylate is preferably an ammonium salt or alkali metal salt of these carboxylic acids.

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

  Next, as shown in FIG. 2, after the reducing agent aqueous solution 5 is dropped into the silver carboxylate slurry 4, a heat treatment is performed to hold the obtained mixed slurry at a temperature in the range of 92 ° C. to 95 ° C. The silver carboxylate particles are reduced to produce silver particles to prepare a silver powder slurry.

By setting the holding temperature of the mixed slurry to 92 ° C. or higher, silver carboxylate is easily reduced, and silver particles can be generated quickly. Moreover, by setting the holding temperature of the mixed slurry to 95 ° C. or lower, the carboxylic acid can be attached as C ₃ H ₃ O ₃ ⁻ ions or C ₆ H ₆ O ₈ ⁻ ions to the surface of the generated silver particles. Therefore, silver particles can be prevented from becoming coarse particles.

  The time for holding the mixed slurry at the above temperature is preferably in the range of 0.25 to 0.5 hours. By setting the holding time to 0.25 hours or longer, silver carboxylate can be reliably reduced, and silver particles can be generated stably. Moreover, it can prevent that the produced | generated silver particle turns into a coarse particle by making holding time into 0.5 hour or less.

  As one method for bringing the mixed slurry to the above-mentioned temperature, a method of preparing the mixed slurry at a temperature of less than 92 ° C. and then heating can be mentioned. In this method, it is preferable to set the temperature rising rate of the mixed slurry in the range of 15 to 20 ° C./hour. By setting the temperature rising rate to 15 ° C./hour or more, the silver particles can be prevented from becoming coarse particles. By setting it to 20 ° C./hour or less, the liquid temperature inside the mixed slurry is less likely to be uneven.

As another method for adjusting the mixed slurry to the above temperature, the silver carboxylate slurry 4 and the reducing agent aqueous solution 5 are heated to maintain the liquid temperature within the range of 92 to 95 ° C. The method of dripping the reducing agent aqueous solution 5 to the acid silver slurry 4 can be mentioned. In this method, the liquid temperature inside the mixed slurry is less likely to be uneven.
be able to.

  As the reducing agent in the reducing agent aqueous solution 5, one or two or more compounds selected from the group consisting of hydrazine, ascorbic acid, oxalic acid, formic acid, and salts thereof are preferable.

  The prepared silver powder slurry is preferably cooled quickly in order to prevent the silver particles from becoming coarse particles. The cooling of the silver powder slurry is preferably performed at a temperature lowering rate at which the time for lowering the temperature to 30 ° C. is 15 minutes or less.

  Next, the silver powder slurry is dried to obtain silver powder. Here, before the silver powder slurry is dried, it is preferable that the liquid layer in the silver powder slurry is removed from the silver powder slurry by a centrifugal separator, and the silver powder slurry is dehydrated and desalted.

  Although it does not specifically limit as a drying method of a silver powder slurry, Specifically, a freeze-drying method, a reduced pressure drying method, a heat drying method etc. are mentioned, for example. The freeze-drying method is a method in which a silver powder slurry is put in a sealed container and frozen, the inside of the sealed container is depressurized with a vacuum pump to lower the boiling point of the material to be dried, and the moisture of the material to be dried is sublimated at a low temperature and dried. is there. The reduced-pressure drying method is a method of drying an object to be dried by reducing the pressure. The heat drying method is a method of drying an object to be dried by heating.

As described above, the silver powder production method of the present embodiment drops silver salt aqueous solution and carboxylic acid aqueous solution simultaneously into water to produce silver carboxylate particles, so that the particle size ranges from 20 nm to 50 nm and the particle size. Can produce silver carboxylate particles in the range of 200 nm to 500 nm. Then, after dropping the reducing agent aqueous solution into the silver carboxylate slurry containing the silver carboxylate particles, the silver carboxylate particles are reduced by holding at a temperature in the range of 92 ° C. or higher and 95 ° C. or lower. _In the number distribution of primary particle diameters covered with ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions, the particle size is in the range of 20 nm to 50 nm and the particle size is in the range of 200 nm to 500 nm. Silver particles each having a peak can be produced.

<Paste-like composition>
The paste-like composition of this embodiment contains the above-mentioned silver powder and a solvent.
The solvent has a predetermined range of vapor pressure. Specifically, the vapor pressure of the solvent is preferably 5 to 866 Pa at 20 ° C., for example. When the vapor pressure of the solvent is 5 Pa or higher at 20 ° C., the solvent easily escapes from the inside of the bonding layer when the heat treatment is performed, so that the silver powder is easily sintered and the shear strength of the bonding layer is improved. In addition, since the vapor pressure of the solvent is 866 Pa or less at 20 ° C., drying after application is suppressed, so that the solvent is uniformly and sufficiently adhered to the object to be bonded, and the shear strength of the bonding layer is improved.

Specific examples of the solvent include alcohol solvents, glycol solvents, acetate solvents, hydrocarbon solvents, amine solvents, and the like.
Specific examples of the alcohol solvent include α-terpineol and isopropyl alcohol. Specific examples of the glycol solvent include ethylene glycol, diethylene glycol, polyethylene glycol, and the like. Specific examples of the acetate solvent include butyltolcarbate and the like. Specific examples of the hydrocarbon solvent include decane, dodecane, and tetradecane. The amine solvent is preferably an alkylamine having 6 to 10 carbon atoms and a molecular weight of 101.19 to 157.30. Specific examples of the alkylamine include hexylamine, octylamine, and dodecylamine.
As the solvent, the above solvents may be used alone, or two or more kinds may be mixed and used.

  The solvent preferably contains an amine solvent. The amine solvent may be used alone or in combination with a solvent other than an amine such as an alcohol solvent, a glycol solvent, an acetate solvent, or a hydrocarbon solvent. Since amine has a high affinity with silver and uniformly protects the surface of silver particles, a dense sintered body can be reliably formed by heating at a relatively low temperature even after storage for a long period of time.

  The mass ratio of the silver powder and the solvent contained in the paste-like composition is not particularly limited as long as it is a ratio that can maintain the paste shape. Specifically, for example, the mass ratio (silver powder: solvent) is preferably in the range of 75:25 to 95: 5. A paste-like composition having a mass ratio of silver powder to solvent in the above range can be uniformly applied to the surface of an object to be coated. Further, even if the applied paste-like composition is heated to evaporate the solvent, the coating film is hardly cracked, and a dense and high-strength sintered body can be generated.

  The paste-like composition of this embodiment can be manufactured by mixing the above-described silver powder and solvent at the above mass ratio.

  As described above, since the paste-like composition of the present embodiment includes the above-described silver powder and solvent, a sintered body (bonding) having a high shear strength of 20 MPa or more even in a low-temperature heat treatment of 150 to 200 ° C. Layer) can be formed. Therefore, even a material that is weak against heat can be bonded.

<Method for producing joined body>
Next, the manufacturing method of the joined body of this embodiment is demonstrated with reference to FIG.
FIG. 3 shows the joined body 11 of the present embodiment. As shown in FIG. 3, the joined body 11 of the present embodiment includes a substrate 12, a first metal layer 13, a joining layer 14, a second metal layer 15, and an article to be joined 16. It is roughly structured.

  In the present embodiment, as an example, the bonded body 11 in which the substrate 12 (first member) and the workpiece 16 (second member) are bonded using the above-described paste-like composition will be described. It does not specifically limit as what joins using a composition.

  Although it does not specifically limit as the board | substrate 12, Specifically, the insulating board etc. with which the aluminum plate and the aluminum plate were joined are mentioned, for example.

  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. Specifically, as the material of the first metal layer 13, for example, one or more 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. The bonding layer 14 is in contact with the second metal layer 15 to form an interface 18. The bonding layer 14 is obtained by applying the paste-like composition described above onto the first metal layer 13, placing the object to be bonded 16 so that the applied surface and the second metal layer 15 face each other, and performing a heat treatment. Is formed.

  The thickness of the bonding layer 14 is not particularly limited as long as the thickness can bond the substrate 12 and the workpiece 16 to each other. Specifically, for example, 1-100 micrometers may be sufficient.

The second metal layer 15 is a bonding layer 14 and is laminated adjacent to the opposite side of the first metal layer 13. The bonding layer 14 and the workpiece 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 workpiece 16 is the second metal layer 15 and is laminated adjacent to the opposite side of the bonding layer 14. Although it does not specifically limit as the to-be-joined object 16, Specifically, silicon (Si), silicon carbide (SiC) etc. are mentioned, for example. Moreover, since the joined body 11 of this embodiment uses the paste-like composition mentioned above, a material weak to heat can also be used as the article to be joined 16.

  In the bonded body 11 of this embodiment, the substrate 12 and the object to be bonded 16 are bonded by the bonding layer 14. Since the bonding layer 14 is formed using the above-described paste-like composition, the shear strength of the bonding layer 14 is high. Specifically, the shear strength of the joined body 11 of the present embodiment is preferably, for example, 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-described joined body 11 will be described.
The manufacturing method of the joined body 11 of this embodiment has a lamination process and a sintering process.

(Lamination process)
First, the laminated body which laminated | stacked the board | substrate 12 (1st member) and the to-be-joined object 16 (2nd member) through the above-mentioned paste-form composition is formed.
Specifically, the first metal layer 13 is formed by laminating metal on the surface of the substrate 12 by a known method. Similarly, the second metal layer 15 is formed on the surface of the workpiece 16. A method for forming a metal on the surfaces of the substrate 12 and the object to be bonded 16 is not particularly limited, and specific examples include a vacuum deposition method, a sputtering method, a plating method, and a printing method.

Next, the aforementioned paste-like composition is applied to the surface of the first metal layer 13 by a known method. The method for applying the paste-like composition to the surface of the first metal layer 13 is not particularly limited, but specifically, for example, spin coating method, metal mask method, spray coating method, dispenser coating method, knife coating. Method, slit coating method, inkjet coating method, screen printing method, offset printing method, die coating method and the like.
Next, an object to be bonded 16 is placed on the paste-like composition applied to the surface of the first metal layer 13 so that the second metal layer 15 side is opposed to produce a laminate.

(Sintering process)
Next, the laminate formed as described above is heated to dry and sinter the paste-like composition, thereby generating the bonding layer 14. The first metal layer 13 and the second metal layer 15 are bonded via the bonding layer 14.

  Although it does not specifically limit as heating temperature in the case of heat processing, Specifically, 150 degreeC or more is preferable, for example. When the heating temperature is 150 ° C. or higher, the shear strength of the bonding layer 14 can be increased.

Although it does not specifically limit as heating time in the case of heat processing, Specifically, 30 minutes or more are preferable, for example. When the heating time is 30 minutes or more, the shear strength of the bonding layer 14 can be increased.
The joined body 11 is manufactured by the above process.

  Since the manufacturing method of the joined body of this embodiment uses the paste-like composition containing the above-mentioned silver powder as a joining material which produces | generates a joining layer as mentioned above, it is a joined body with high joint strength by heating at low temperature than before. Can be manufactured.

<Silver film production method>
Next, the manufacturing method of the silver film of this embodiment is demonstrated.
The silver film obtained by the manufacturing method of this embodiment is used as an electrode of a solar cell element, for example.
The manufacturing method of the silver film of this embodiment includes the following application | coating processes and a sintering process.

(Coating process)
First, the above paste-like composition is applied to a substrate.
The substrate is selected from the group consisting of silicon, glass, ceramics including a transparent conductive material, a substrate made of a polymer material or a metal, or silicon, glass, ceramics including a transparent conductive material, a polymer material and a metal. It can be a laminate of two or more types. Moreover, it is preferable that a base material is either a solar cell element or a solar cell element with a transparent metal film. As the transparent metal film, indium tin oxide (ITO), antimony-doped tin oxide (ATO), nesa (tin oxide SnO ₂ ), IZO (Indium Zinc Oxide), AZO (aluminum-doped ZnO) ) And the like. It is preferable that the said paste-form composition is apply | coated to the surface of the photoelectric conversion semiconductor layer of a solar cell element, or the surface of the transparent metal film of a solar cell element with a transparent metal film.

(Sintering process)
Next, the base material coated with the paste composition is heated to dry and sinter the paste composition to form a silver film. The heating temperature is generally in the range of 130 ° C. to 250 ° C., preferably in the range of 150 ° C. to 200 ° C. By heating in the above temperature range, a dense silver film having high strength can be formed. The heating time is generally in the range of 10 minutes to 1 hour, preferably in the range of 15 to 40 minutes. There is no restriction | limiting in particular in a heating atmosphere, It can set arbitrarily in air | atmosphere atmosphere, a vacuum atmosphere, a reducing gas atmosphere, etc. The thickness of the silver film produced by the production method of the present embodiment is generally in the range of 0.1 μm to 2.0 μm, preferably in the range of 0.3 μm to 1.5 μm. If the film thickness becomes too thin, for example, when used as an electrode of a solar cell element, the surface resistance value may be insufficient. On the other hand, if the film thickness becomes too thick, the amount of silver powder used increases and the cost increases.

  According to the method for producing a silver film of the present embodiment, as described above, since the paste-like composition containing the above-described silver powder is used as the material for the silver film, a dense silver film is produced by heating at a lower temperature than conventional. be able to.

  Hereinafter, although the effect of the present invention is explained in detail using an example, the present invention is not limited to the following example.

<Manufacture of silver powder>
(Classification I)
First, a silver nitrate aqueous solution (silver nitrate concentration: 66 mass%) as the silver salt aqueous solution 1, an ammonium citrate aqueous solution (citric acid concentration: 56 mass%) as the carboxylic acid aqueous solution 2, and a sodium oxalate aqueous solution (as the reducing agent aqueous solution 5) Oxalic acid concentration: 58% by mass) was prepared.

  First, as shown in FIG. 1, a 900 g silver nitrate aqueous solution (silver salt aqueous solution) held in a glass container containing 1200 g of ion-exchanged water (water 3) held at 50 ° C. in a hot water bath and held at 50 ° C. in a hot water bath. 1) and 600 g of an aqueous ammonium citrate solution (carboxylic acid aqueous solution 2) maintained at 50 ° C. in a hot water bath are simultaneously added dropwise over 5 minutes using a tube pump to produce silver citrate particles, and An acid silver slurry (silver carboxylate slurry 4) was prepared. The prepared silver citrate slurry was air-cooled to 20 ° C.

  Next, as shown in FIG. 2, while maintaining the silver citrate slurry (silver carboxylate slurry 4) at 20 ° C., 300 g of sodium oxalate aqueous solution (reducing agent) maintained at 20 ° C. was added to the silver citrate slurry. Aqueous solution 5) was added dropwise over 30 minutes to prepare a mixed slurry.

  Next, the mixed slurry is heated to a temperature of 92 ° C. at a rate of temperature increase of 15 ° C./hour and heat-treated at a temperature of 92 ° C. (maximum temperature) for 0.33 hours to reduce silver citrate particles. Thus, silver particles were generated to obtain a silver powder slurry. A silver powder slurry was obtained. The resulting silver powder slurry was cooled to 30 ° C. over 15 minutes. Next, the silver powder slurry was put in a centrifuge and centrifuged at a rotational speed of 1000 rpm for 10 minutes. The supernatant liquid (liquid layer) was removed, and the remaining solid content (silver powder) was washed with water, and then dried by freeze-drying for 30 hours to recover the silver powder. The recovered silver powder was classified as Class I silver powder.

(Category II)
Prepare a mixed slurry by dropping the sodium oxalate aqueous solution into the silver citrate slurry while maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 30 ° C. Then, the prepared mixed slurry was heated to 95 ° C. and maintained at 95 ° C. for 0.5 hour to obtain a silver powder of class II in the same manner as in class I.

(Category III)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 50 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated to 92 ° C. and kept at 92 ° C. for 0.25 hour to obtain a silver powder of class III in the same manner as in class I.

(Category IV)
A glycolic acid aqueous solution (glycolic acid concentration: 56 mass%) was used as the carboxylic acid aqueous solution 2, and a hydrazine aqueous solution (hydrazine concentration: 58 mass%) was used as the reducing agent aqueous solution 5, a silver glycolate slurry (silver carboxylate slurry) 4) and a hydrazine aqueous solution (reducing agent aqueous solution 5) at 30 ° C., respectively, except that a mixed slurry was prepared by dropping the hydrazine aqueous solution into a silver glycolate slurry. Obtained silver powder.

(Classification V)
A glycolic acid aqueous solution (glycolic acid concentration: 56% by mass) was used as the carboxylic acid aqueous solution 2, and a formic acid aqueous solution (formic acid concentration: 58% by mass) as the reducing agent aqueous solution 5, silver glycolate slurry (silver carboxylate slurry) 4) and a formic acid aqueous solution (reducing agent aqueous solution 5), respectively, maintained at 30 ° C., except that a mixed slurry was prepared by dropping a formic acid aqueous solution into a silver glycolate slurry. Obtained silver powder.

(Classification VI)
A silver powder of classification VI was obtained in the same manner as in classification I, except that an aqueous ammonium formate solution (formic acid concentration: 58% by mass) was used as the reducing agent aqueous solution 5.

(Category VII)
Except for using an ammonium malate aqueous solution (malic acid concentration: 56 mass%) as the carboxylic acid aqueous solution 2 and a formic acid aqueous solution (formic acid concentration: 58 mass%) as the reducing agent aqueous solution 5, the same manner as in Class I A silver powder of classification VII was obtained.

(Classification VIII)
A silver powder of class VIII was obtained in the same manner as class I, except that a disodium maleate aqueous solution (maleic acid concentration: 56 mass%) was used as the carboxylic acid aqueous solution 2.

(Classification IX)
A malonic acid aqueous solution (concentration of malonic acid: 56% by mass) was used as the carboxylic acid aqueous solution 2, and a sodium ascorbate aqueous solution (concentration of ascorbic acid: 58% by mass) was used as the reducing agent aqueous solution 5. A mixed slurry was prepared by dropping the sodium ascorbate aqueous solution into the silver malonate slurry while maintaining the silver acid slurry 4) and the sodium ascorbate aqueous solution (reducing agent aqueous solution 5) at 40 ° C., respectively. A silver powder of class IX was obtained in the same manner as class I except that the slurry was heated to a temperature of 92 ° C. at a rate of temperature rise of 20 ° C./hour.

(Category X)
Carboxylic acid aqueous solution (fumaric acid concentration: 28 mass%, succinic acid concentration: 28 mass%) containing fumaric acid and succinic acid as carboxylic acid aqueous solution 2 and formic acid aqueous solution (formic acid concentration: 58 as reducing agent aqueous solution 5). A silver powder of class X was obtained in the same manner as class I except that (mass%) was used.

(Classification XI)
Classification was carried out in the same manner as in Class I except that a succinic acid aqueous solution (succinic acid concentration: 56 mass%) was used as the carboxylic acid aqueous solution 2 and a formic acid aqueous solution (formic acid concentration: 58 mass%) was used as the reducing agent aqueous solution 5. XI silver powder was obtained.

(Classification XII)
Except for using an aqueous solution of ammonium tartrate (tartaric acid concentration: 56 mass%) as the carboxylic acid aqueous solution 2 and an aqueous formic acid solution (concentration of formic acid: 58 mass%) as the reducing agent aqueous solution 5, classification XII Obtained silver powder.

(Classification XIII)
A silver chlorate aqueous solution (silver chlorate concentration: 66% by mass) as the silver salt aqueous solution 1, a glycolic acid aqueous solution (glycolic acid concentration: 56% by mass) as the carboxylic acid aqueous solution 2, and a hydrazine aqueous solution (as the reducing agent aqueous solution 5). A silver powder of class XIII was obtained in the same manner as class I except that hydrazine concentration: 58% by mass) was used.

(Classification XIV)
Silver salt aqueous solution containing silver nitrate and silver phosphate (silver nitrate concentration: 33% by mass, silver phosphate concentration: 33% by mass) as silver salt aqueous solution 1 and glycolic acid aqueous solution (concentration of glycolic acid) as carboxylic acid aqueous solution 2 : 56 mass%), except that an aqueous hydrazine solution (hydrazine concentration: 58 mass%) was used as the reducing agent aqueous solution 5, a silver powder of classification XIV was obtained in the same manner as in classification I.

(Classification XV)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 15 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated up to 70 ° C. and kept at 70 ° C. for 0.5 hours to obtain a silver powder of classification XV in the same manner as in classification I.

(Classification XVI)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 60 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated to 97 ° C. and maintained at 97 ° C. for 1 hour, and a silver powder of classification XVI was obtained in the same manner as in classification I.

(Classification XVII)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 50 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated to 91 ° C. and maintained at 91 ° C. for 0.75 hour to obtain a silver powder of class XVIII in the same manner as in class I.

(Classification XVIII)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 60 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated to 91 ° C. and kept at 91 ° C. for 0.5 hours to obtain a silver powder of class XVIII in the same manner as in class I.

(Classification XIX)
While maintaining the silver citrate slurry (silver carboxylate slurry 4) and the sodium oxalate aqueous solution (reducing agent aqueous solution 5) at 50 ° C., the sodium oxalate aqueous solution was dropped into the silver citrate slurry to prepare a mixed slurry. Then, the prepared mixed slurry was heated to 98 ° C. and maintained at 98 ° C. for 0.25 hour to obtain a silver powder of class XIX in the same manner as class I.

(Classification XX)
A commercially available silver powder ("SPQ03S" manufactured by Mitsui Kinzoku Kogyo Co., Ltd.) was prepared as a silver powder of classification XX.

<Evaluation of silver powder>
For the silver powders of classifications I to XVII, the number distribution of primary particle diameters and the detected amounts of C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions with respect to Ag ⁺ ions were measured by the following methods.

(Measurement method of primary particle size number distribution)
The primary particle diameter of silver powder was measured as follows. That is, silver powder was mixed with an epoxy resin, and the resulting mixture was cured to produce a silver particle diameter measurement sample. The central part of this silver particle diameter measurement sample was cut, and the cut surface was polished with an argon ion beam. The polished processed surface is observed with an SEM (scanning electron microscope), 1000 or more primary particles are randomly selected, and the diameter of the selected primary particles in the direction along the irradiation direction of the argon ion beam is determined. The primary particle size was measured. The number distribution of primary particle diameters was created by classifying the measured primary particle diameters every 10 nm.

(Ag _C 3 _H 3 against ⁺ ions _{O 3} ^- ions and _C 6 _H 6 _{O 8} ^- method of measuring the detected amount of ions)
The detected amounts of C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions with respect to Ag ⁺ ions were measured by time-of-flight secondary ion mass spectrometry (TOF-SIMS). A sample in which silver powder was buried in the surface of the In foil was used as a measurement sample. The measuring device used was nanoTOFII manufactured by ULVAC PHI. The measurement range was 100 μm square, the primary ion was Bi ₃ ⁺⁺ (30 kV), the measurement time was 5 minutes, and a TOF-SIMS spectrum was obtained. From the obtained TOF-SIMS spectrum, the detected amount of Ag ⁺ ion, C ₃ H ₃ O ₃ ⁻ ion, C ₆ H ₆ O ₈ ⁻ ion was determined, and C ₃ H ₃ O ₃ ⁻ ion and C ₆ H ₆ O were obtained. ₈ ^- a detectable amount of ions, each divided by the detected amount of Ag ⁺ ions, _C 3 _H 3 for Ag ⁺ ions _{O 3} ^- ions and _C 6 _H 6 _{O 8} ^- to calculate the detected amount of ions.

  The results of each measurement are shown in Table 1 below. In Table 1, the silver salt, carboxylic acid or carboxylate salt used for the production of the silver powder, the kind of the reducing agent, the temperature of the silver carboxylate slurry and the reducing agent solution, the heat treatment conditions of the mixed slurry (heating rate, maximum (Temperature, holding time) are also listed.

<Preparation of paste-like composition>
(Invention Example 1-1)
Class I silver powder and α-terpineol (vapour pressure at 20 ° C .: 24 Pa) are put in a container so that the mass ratio is 85:15, and 2000 rpm with a kneading machine (manufactured by THINKY, “Awatori Kentaro”). A paste-like composition was obtained by performing kneading for 5 minutes at a rotational speed of 3 times.

(Invention Examples 1-2 to 1-18 and Comparative Examples 1-1 to 1-6)
A paste-like composition was obtained in the same manner as in Example 1-1 of the present invention except that the silver powder of the classification described in Table 2 below was used and the solvent described in Table 2 below was used. Table 2 also shows data on the number distribution of primary particles of silver powder, the total content of primary particles of 20 to 50 nm and the primary particles of 200 to 500 nm, and the amount of organic compounds.

<Preparation of joined body>
(Invention Example 2-1)
A plate in which an aluminum plate is coated with silver is prepared as a substrate, and the paste-like composition of Example 1-1 of the present invention is printed on the silver using a metal mask (hole size: length 3 mm × width 3 mm × thickness 50 μm). And then molded. Next, a silicon chip (size: length 2.5 mm × width 2.5 mm × thickness 200 μm) whose surface is coated with silver is placed on the paste-like composition, and is placed in an air atmosphere at a temperature of 150 ° C. for 30 minutes. Firing was performed by holding. As a result, a bonding layer was formed between the substrate and the silicon chip to obtain a bonded body.

(Invention Examples 2-2 to 2-18 and Comparative Examples 2-1 to 2-6)
A joined body was obtained in the same manner as in Example 2-1 except that the pasty composition described in Table 3 below was used as the pasty composition. However, in Comparative Example 2-6, the substrate and the silicon chip were not bonded.

(Invention Example 2-19)
A joined body was obtained in the same manner as in Example 2-1 except that a gold plate was used as the substrate and that the surface of the silicon chip was coated with gold.

(Invention Example 2-20)
A joined body was obtained in the same manner as in Example 2-1 except that a copper plate was used as the substrate and that the surface of the silicon chip was coated with copper.

<Evaluation of bonding layer>
For the bonding layers formed between the substrates of the inventive examples 2-1 to 2-20 and comparative examples 2-1 to 2-5 and the silicon chip, the shear strength was measured. The shear strength was determined by measuring the force required to break the bonding layer formed between the substrate and the silicon chip with a bonding tester (manufactured by RHESCA) and dividing this measured value by the bonding area to obtain the shear strength. . In addition, the evaluation of denseness was performed as follows. That is, after the cross section of the bonding layer is buffed and ion beam polished, the cross section of the bonding layer is observed with an SEM, divided into a silver portion and a void portion in the field of view, and binarized by image processing software. When the ratio of the silver portion in the area was expressed in area%, 85 area% or more was marked with ◎, area 75 wt% or more and less than 85 area% was marked with ○, and less than 75 area% was marked with x.

  Table 3 below shows the evaluation results of the paste-like composition, the bonding surface (metal species coated on the surface of the substrate and the silicon chip), the denseness, and the shear strength of the bonded bodies of the present invention examples and the comparative examples.

There are few particles of 200 nm or more and 500 nm or less, the detection amount of C ₃ H ₃ O ₃ ⁻ ions exceeds 1.0 times the detection amount of Ag ⁺ ions, and the detection amount of C ₆ H ₆ O ₈ ⁻ ions The joined body of Comparative Example 2-1 using silver powder exceeding 0.02 times had low denseness and strength. This is because the amount of primary particles having a relatively large particle size is small and gaps are easily formed between the primary particles, and the amount of the organic compound covering the surface of the silver particles is large and the sinterability is reduced. Is presumed to be the cause.

There are few particles of 20 nm or more and 50 nm or less, the detection amount of C ₃ H ₃ O ₃ ⁻ ions is less than 0.2 times the detection amount of Ag ⁺ ions, and the detection amount of C ₆ H ₆ O ₈ ⁻ ions is The joined body of Comparative Example 2-2 using silver powder less than 0.005 times had low denseness and strength. This is because the amount of primary particles having a relatively small particle size was small and gaps were easily formed between the primary particles, the amount of the organic compound covering the surface of the silver particles was small, and the silver powders were strongly agglomerated. Therefore, it is presumed that the dense bonding layer was not obtained.

The detection amount of C ₃ H ₃ O ₃ ⁻ ion and C ₆ H ₆ O ₈ ⁻ ion is within the range of the present invention with respect to the detection amount of Ag ⁺ ion, but silver powder with less particles of 20 nm to 50 nm is used. The joined body of Comparative Example 2-3 had high strength but low density. Since C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions are within the scope of the present invention, the sintering of the interface between the workpiece and the bonding layer and the inside of the bonding layer progressed. This is probably because the amount of primary particles having a small particle size is small and gaps are easily formed between the primary particles.

The detection amount of C ₃ H ₃ O ₃ ⁻ ion and C ₆ H ₆ O ₈ ⁻ ion is within the range of the present invention relative to the detection amount of Ag ⁺ ion, but silver powder with few particles of 200 nm to 500 nm is used. The joined body of Comparative Example 2-4 was high in strength but low in density. Since C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions are within the scope of the present invention, the sintering of the interface between the workpiece and the bonding layer and the inside of the bonding layer progressed. This is presumed to be because the amount of primary particles having a large particle size is small, so that the primary particles having a relatively small particle size remain and the gap between the bonding layers is easily formed.

The detection amount of C ₃ H ₃ O ₃ ⁻ ion and C ₆ H ₆ O ₈ ⁻ ion is within the range of the present invention with respect to the detection amount of Ag ⁺ ion, but silver powder with less particles of 20 nm to 50 nm is used. The joined body of Comparative Example 2-5 had high strength but low density. Since C ₃ H ₃ O ₃ ⁻ ions and C ₆ H ₆ O ₈ ⁻ ions are within the scope of the present invention, the sintering of the interface between the workpiece and the bonding layer and the inside of the bonding layer progressed. This is presumably because the primary particles having a large particle size have a large amount of primary particles, and the primary particles having a relatively small particle size cannot fill the gaps, and the gaps in the bonding layer are easily formed.

In contrast, in the time-of-flight secondary ion mass spectrometry, the detected amount of C ₃ H ₃ O ₃ ⁻ ions is 0.2 to 1.0 times the detected amount of Ag ⁺ ions, and C ₆ H ₆ O ₈ ^- is in the range detection amount less 0.02 times 0.005 times the ions, containing the primary particles in the number distribution of the primary particle size in the range particle size of 20nm or more 50nm or less The joined body of Examples 2-1 to 2-20 of the present invention using silver powder having an amount of 65% by number or more and a content of primary particles having a particle size in the range of 200 nm to 500 nm of 3% by number or more Was strong and dense. In particular, Invention Example 2 using silver powder having a total content of primary particles having a particle size in the range of 20 nm to 50 nm and primary particles having a particle size in the range of 200 nm to 500 nm of 85% by number or more. The joined body of -9 was remarkably improved in strength and denseness.

DESCRIPTION OF SYMBOLS 1 ... Silver salt aqueous solution 2 ... Carboxylate aqueous solution 3 ... Water 4 ... Silver carboxylate slurry 5 ... Reducing agent aqueous solution 11 ... Bonding body 12 ... Board | substrate 13 ... 1st metal layer 14 ... Bonding layer 15 ... 2nd metal layer 16 ... Objects to be joined 17, 18 ... Interface

Claims (9)

In time-of-flight secondary ion mass spectrometry, the detected amount of C ₃ H ₃ O ₃ ⁻ ions is 0.2 to 1.0 times the detected amount of Ag ⁺ ions, and C ₆ H ₆ O ₈ ^- is in the range detection amount less 0.02 times 0.005 times the ions in the number distribution of the primary particle size, the content of the primary particles in the range particle size of 20nm or 50nm or less 65% by number Silver powder characterized in that the content of primary particles having a particle size of 200 nm or more and 500 nm or less is 3% by number or more.   In the primary particle size distribution, the total content of primary particles having a particle size in the range of 20 nm to 50 nm and primary particles having a particle size in the range of 200 nm to 500 nm is 85% by number or more. The silver powder according to claim 1. A step of simultaneously dropping an aqueous silver salt solution and an aqueous solution of a carboxylic acid or a carboxylate salt into water to produce silver carboxylate particles to prepare a silver carboxylate slurry;
After dropping the reducing agent aqueous solution into the silver carboxylate slurry, the silver carboxylate particles are reduced by holding at a temperature in the range of 92 ° C. or higher and 95 ° C. or lower to produce silver particles, thereby preparing a silver powder slurry. Process,
Drying the silver powder slurry to obtain silver powder;
A method for producing silver powder, comprising:   The silver salt in the silver salt aqueous solution is one or more compounds selected from the group consisting of silver nitrate, silver chlorate, and silver phosphate. Method.   The carboxylic acid in the carboxylic acid or carboxylate aqueous solution is one or more selected from the group consisting of glycolic acid, citric acid, malic acid, maleic acid, malonic acid, fumaric acid, succinic acid and tartaric acid The method for producing silver powder according to claim 3, wherein the compound is a compound of   The reducing agent in the reducing agent aqueous solution is one or two or more compounds selected from the group consisting of hydrazine, ascorbic acid, oxalic acid, formic acid and salts thereof. Silver powder production method.   A paste-like composition comprising the silver powder according to claim 1 and a solvent. A method for manufacturing a joined body in which a first member and a second member are joined via a joining layer,
A laminating step of forming a laminate in which the first member and the second member are laminated via the paste-like composition according to claim 7;
A sintering step in which the laminate is heated to dry and sinter the paste-like composition to form a bonding layer;
A method for producing a joined body, comprising: An application step of applying the paste-like composition according to claim 7 to a substrate;
Heating the substrate coated with the paste-like composition, drying and sintering the paste-like composition to produce a silver film; and
A method for producing a silver film, comprising:

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