JP6668735B2 - Method for manufacturing bonding material and bonded body - Google Patents

Description

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

  As a method for mounting electronic components such as a semiconductor chip and an LED element on a circuit board, a method using a bonding material is known. As a bonding material, a paste-like bonding material in which metal particles such as silver powder are dispersed in a solvent is known. This bonding material is to apply the bonding material to the surface of one component, bring the other component into contact with the applied surface, and heat in this state to sinter the metal particles of the bonding material to form a bonding layer. To join the parts. As a joining material, a material that can be joined with high shear strength (joining strength) is desired.

  For example, Patent Literature 1 discloses that a submicron-sized metal particle having an average primary particle size of 0.5 to 3.0 μm and an average primary particle as a bonding material that can reduce the unevenness of the shear strength while securing the shear strength. A bonding material containing nano-sized metal particles having a particle size of 1 to 200 nm and a dispersion medium is disclosed.

  Patent Literature 2 discloses metal nanoparticles having an average particle diameter of 100 nm or less and having a surface coated with an organic material having 6 to 8 carbon atoms as a bonding material capable of securing a high shear strength even when the nanoparticles are used alone. A bonding material comprising 5 to 20% by mass of a polar solvent with respect to the powder of nanoparticles is disclosed.

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

  By the way, a copper substrate using copper or a copper alloy as a conductive material is widely used as a circuit substrate. Since copper is easily oxidized, an oxide film is usually formed on the surface of the copper substrate. When an oxide film is interposed between the copper substrate and the bonding layer, there is a problem that the shear strength is reduced. However, since copper is more easily oxidized than silver, it is difficult to remove an oxide film formed on the surface of the copper substrate by forming a bonding layer using a conventional bonding material containing silver powder.

  The present invention has been made in view of the above circumstances, and is to stably form a bonding layer having a high shear strength on a copper substrate on which an oxide film is formed, even when stored for a long time. It is an object of the present invention to provide a bonding material that can perform the bonding and a method for manufacturing the bonded body.

  The inventors have found that a silver powder having a primary particle size distribution 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 has a carbon number of 6 to 10 nm. And the use of a bonding material containing an alkylamine having a molecular weight in the range of 101.19 to 157.30 and a reducing organic solvent allows a copper substrate having an oxide film to be formed. It has been found that a bonding layer having high strength can be formed.

  The reason why it is possible to form a bonding layer having a high shear strength by using the above-described bonding material is that the primary particles of the silver powder have a specific particle size distribution, so that the obtained bonding layer (sintered body) It is considered that this is because voids (bubbles) are small and dense. Also, the reason why it is possible to form a bonding layer having a high shear strength even on a copper substrate having an oxide film formed thereon is that the reducing organic solvent in the bonding material reduces the oxide film on the copper substrate. It is thought that it is to remove. Furthermore, the reason that the bonding layer having high shear strength can be stably formed even when stored for a long period of time is that the aggregation of silver powder is suppressed by the adhesion of the alkylamine to the surface of the silver powder. It is thought to be because.

Therefore, in order to solve the above problems, the present invention has adopted the following configurations.
[1] a silver powder having a primary particle size distribution having a first peak in a particle size range of 20 to 70 nm and a second peak in a particle size range of 200 to 500 nm;
An alkylamine having 6 to 10 carbon atoms and a molecular weight in the range of 101.19 to 157.30;
A bonding material comprising a reducing organic solvent (however, excluding dipropylene glycol monomethyl ether, butyl carbitol, methylpentanediol and terpineol ).

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

[3] The bonding material according to the above item 1 or 2, wherein the silver powder includes secondary particles formed by agglomeration of primary particles, and the particle size of the secondary particles is 10 µm or less. .

[4] The mass ratio A / B of the content A of the alkylamine to the content B of the reducing organic solvent is in the range of 0.1 or more and 19 or less, wherein The bonding material according to any one of the above.

[5] A method for manufacturing a joined body in which a copper substrate and an electronic component are joined via a joining layer, wherein the joining layer is formed using the joining material according to any one of the above items 1 to 4. A method for manufacturing a joined body to be formed.

  According to the present invention, for a copper substrate on which an oxide film is formed, a bonding layer having high shear strength, a bonding material that can be stably formed even when stored for a long time, and a bonded body It is possible to provide a manufacturing method.

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

<Joining materials>
First, a configuration of a bonding material according to an embodiment to which the present invention is applied will be described. The bonding material according to the present embodiment includes silver powder and a solvent. As the solvent, an alkylamine and a reducing organic solvent are used. The bonding material of this embodiment can form a bonding layer by performing a heat treatment, and can bond two or more objects to be bonded to each other. The joining material of the present embodiment can join an object 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 to heat.

The silver powder is made of pure silver and a silver alloy containing silver as a main component (the content of silver is 99% by mass or more).
The shape of the silver powder is not particularly limited, but specific examples include a sphere, a rod, and a scale.
The particle size is determined by observing 1,000 or more primary particles with a scanning electron microscope, binarizing the SEM image using image processing software “ImageJ (developed by the National Institutes of Health),” and comparing the boundaries between particles and non-particles. Was determined, the area of each particle was calculated from the number of pixels, and this was converted to a perfect circle to obtain the primary particle size of each particle. 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.

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

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

  When the second peak is at least 200 nm, a bonding layer having a thickness sufficient to maintain bonding can be formed during heat treatment. When the second peak is at most 500 nm, the degree of filling of silver in the bonding layer can be increased.

  Further, when the particle size distribution of the primary particles is included in the above range, the filling degree of the silver powder inside the joining material can be increased after the joining material is applied to the surface of the article to be joined. Therefore, when the heat treatment is performed, 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 is 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 measuring the particle size of 1,000 or more silver particles. Can be measured. Here, the upper two values having the largest number of particle diameters were calculated, and the smaller one was defined as the particle diameter of the first peak, and the larger one was defined as the particle diameter of the second peak.

  The primary particles of silver powder may form secondary particles (agglomerated particles). The particle size of the secondary particles is preferably 10 μm or less. When the particle diameter of the secondary particles is in the above range, the filling degree of the silver powder inside the bonding material can be further increased. As a result, the filling degree of silver in the bonding layer is increased, and when the bonding layer is formed, generation of voids (bubbles) is suppressed, and the shear strength of the bonding layer is further improved.

  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 determined.

  It is preferable that the surface of the silver powder is mainly covered with an organic substance such as an organic molecule having 4 or less carbon atoms. Specifically, as the organic substance that coats the silver powder, for example, those that decompose at 50 ° C. or more at 150 ° C. are preferable, and those that decompose at 75 ° C. or more at 150 ° C. are more preferable.

  When the organic substance covering 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.

  In addition, the measurement of the decomposition rate of the organic substance covering the silver powder can be performed, for example, by holding the silver powder in the atmosphere at a predetermined temperature for a predetermined time, and then measuring the mass loss after heating compared to before heating. .

  The silver powder preferably generates gas when heated. Specifically, for example, when the powdered silver powder is heated at 100 ° C., it is preferable that gaseous carbon dioxide, evaporate of acetone, and evaporate of water are generated.

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

  The gas generated when the silver powder is heated is specified 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 where silver powder is introduced, for example, The analysis can be performed by using a gas such as "PY-3030" manufactured by Frontier Laboratories, "JMS-T100GCV" manufactured by JEOL Ltd.).

  In the bonding material of this embodiment, an alkylamine and a reducing organic solvent are used in combination as a solvent.

The alkylamine has a protective effect of coating the surface of the silver particles and preventing the silver particles from being excessively reduced by the reducing organic solvent. When the number of carbon atoms of the alkylamine (the number of carbon atoms of the alkyl group of the alkylamine) is less than 6, the protective effect is low. On the other hand, when the alkylamine has more than 10 carbon atoms, the protective effect of the silver powder becomes too strong, so that sintering of the silver particles hardly proceeds during the heat treatment, and the bonding layer of the bonded body may become weak.
For this reason, the alkylamine used in the bonding material of the present embodiment has 6 to 10 carbon atoms and a molecular weight of 101.19 to 157.30. Alkylamines having 6 to 10 carbon atoms are easily released from silver powder by heating. Therefore, voids (bubbles) due to desorption of the alkylamine are less likely to be generated in the bonding layer of the bonded body manufactured using the bonding material of the present embodiment.

The reducing organic solvent has an action of reducing and removing the oxide film on the copper substrate. Examples of reducing organic solvent, ethylene glycol, hexylene glycol, Oh Kutanjio Le and the like.

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

  The amount of silver powder contained in the joining material is not particularly limited as long as the ratio can maintain the paste state. Specifically, the content of the silver powder is preferably in the range of 70 to 90% by mass based on the whole bonding material. If the content of silver powder in the bonding material is less than the lower limit, it may be difficult to obtain a film having high strength. On the other hand, if it exceeds the upper limit, cracks tend to occur in the coating film when applied to the surface of the article.

It is preferable that the content of the alkylamine as the solvent and the content of the reducing organic solvent be in the range of 10 to 30% by mass based on the whole bonding material. The mass ratio A / B of the content A of the alkylamine and the content B of the reducing organic solvent is preferably in the range of 0.1 or more and 19 or less.
If the mass ratio A / B is less than 0.1, the content of the alkylamine becomes too small, and the silver particles may be excessively reduced and activated, which may easily cause aggregation. On the other hand, when the mass ratio A / B exceeds 19, the content of the reducing organic solvent decreases, the reducing ability of the copper substrate to the oxide film decreases, and a bonding layer having high shear strength is formed on the surface of the copper substrate. May be difficult to do.

Next, a method for manufacturing the above-described bonding material will be described with reference to FIGS.
First, as shown in FIG. 1, a silver salt 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 in 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 generated, and the particle size of the silver powder can be increased. Further, by maintaining the temperature of each of the liquids 1 to 4 at a predetermined temperature of 90 ° C. or less, it is possible to prevent the silver powder from becoming coarse particles.

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

  The carboxylic acid in the carboxylate 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. More than one compound is 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 has a lower production cost than distilled water.

  Next, as shown in FIG. 2, a reducing agent aqueous solution 5 is dropped on the silver carboxylate slurry 4 and then subjected to a predetermined heat treatment 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 a range of 20 to 90 ° C. at a temperature rising rate of 15 ° C./hour or less. A heat treatment in which the temperature is maintained for 1 to 5 hours, and then the temperature is reduced to 30 ° C. or less over 30 minutes or less may be used.

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

  In the above-mentioned 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. Further, by setting the maximum temperature to 90 ° C. or less, it is possible to prevent silver powder from becoming coarse particles.

  In the above-mentioned 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.

  In addition, in the above-mentioned predetermined heat treatment, by setting the time for lowering the temperature to 30 ° C. to 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 in 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 more, silver carboxylate is easily reduced, and the particle size of silver powder can be increased. Further, by maintaining the temperature of each of the liquids 4 and 5 at a predetermined temperature of 90 ° C. or less, it is possible to prevent the silver powder from becoming coarse particles.

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

  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 by a centrifugal separator and dehydrate and desalinate the silver powder slurry.

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

  Next, a bonding material is manufactured by mixing the generated silver powder, the alkylamine, and the reducing organic solvent. There is no particular limitation on a mixing method, a method of simultaneously mixing silver powder, an alkylamine and a non-amid reducing organic solvent, a method of mixing a mixture containing silver powder and an alkylamine and a reducing organic solvent, a method of mixing silver powder and a reducing organic solvent, And a method of mixing a mixture containing an alkylamine and a reducing organic solvent with silver powder, and a method of mixing a silver powder with a mixture containing an alkylamine and a reducing organic solvent.

<Joint body>
Next, a method for manufacturing a joined body according to an embodiment of the present invention will be described with reference to FIG. FIG. 3 is a cross-sectional view of an example of the joined body 11 manufactured using the joining material of the present embodiment. As shown in FIG. 3, the bonded body 11 includes a copper substrate 12, a bonding layer 13 formed on the copper substrate 12, and an electronic component 14 bonded to the bonding layer 13.

  As an example of the copper substrate 12, a circuit board having a conductive layer made of copper or a copper alloy on the surface is exemplified. Specific examples of the circuit board include a printed circuit board such as a rigid wiring circuit board and a flexible wiring circuit board. Examples of the electronic component 14 include a semiconductor chip and an LED element.

  The bonding layer 13 is a layer formed by heating the above-described bonding material and sintering the silver particles. The thickness of the bonding layer 13 is preferably in the range of 1 to 100 μm. When the thickness of the bonding layer 13 is in the above range, the copper substrate 12 and the electronic component 14 can be bonded with high shear strength. The shear strength is preferably at least 20 MPa, more preferably at least 30 MPa.

  The bonded body 11 is formed by, for example, applying a bonding material to the surface of the copper substrate 12, and then arranging the bonding material on the bonding material to which the electronic component 14 is applied, and then heating the bonding material to form the bonding layer 13. Can be manufactured. The heating temperature is preferably set to 150 ° C. or higher, and particularly preferably in the range of 180 ° C. to 250 ° C. The heating time is not particularly limited, but is preferably 30 minutes or more. The bonded body 11 obtained by the above method has the bonding layer 13 which usually has a shear strength of 20 MPa or more. Further, when heating is performed at 200 ° C. or higher, the bonding layer 13 having a shear strength of 40 MPa or higher can be formed.

  As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, the specific configuration is not limited to the embodiments and includes a design and the like within a range not departing from the gist of the present invention. For example, in the above-described bonded body 11, an example in which the copper substrate 12 and the electronic component 14 are bonded via the bonding layer 13 has been described, but the present invention is not limited to this. The joining material of the present invention may be used, for example, for joining a copper plate and a copper plate.

  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, 900 g of silver nitrate aqueous solution (silver salt aqueous solution 1) kept at 50 ° C., 1200 g of ion-exchanged water (water 3) kept at 50 ° C., and 600 g of citric acid solution kept at 50 ° C. An aqueous solution of sodium citrate (aqueous carboxylate 2) was simultaneously added dropwise over 5 minutes to prepare a silver citrate slurry (silver carboxylate slurry 4).

  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 ion exchange water (water 3), the ion exchange water (water 3) was continuously stirred. 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 (carboxylate aqueous solution 2) was 56% by mass.

  Then, as shown in FIG. 2, 300 g of an aqueous solution of sodium oxalate (aqueous reducing agent 5) at 50 ° C. was added to the silver citrate slurry (silver carboxylate slurry 4) maintained at 50 ° C. over 30 minutes. The mixture was dropped to obtain a mixed slurry. The concentration of oxalic acid in this sodium oxalate (aqueous reducing agent 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 temperature rising rate of 10 ° C./hour, maintained at 70 ° C. (maximum temperature) for 2 hours, and then lowered to 30 ° C. over 60 minutes. . Thus, 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. Thus, 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 by a freeze-drying method for 30 hours to obtain Class I silver powder.

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

(Class III)
Except that the mixed slurry was prepared while maintaining the temperature of each liquid at 30 ° C., and the rate of temperature rise during the heat treatment was 0 ° C./hour, the maximum temperature was 30 ° C., and the holding time was 5 hours. A silver powder of category III was obtained in the same manner as I.

(Class IV)
Except that the mixed slurry was prepared while maintaining the temperature of each liquid at 15 ° C., and the rate of temperature rise during heat treatment was 0 ° C./hour, the maximum temperature was 15 ° C., and the holding time was 5 hours. Silver powder of Class IV was obtained in the same manner as I.

(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)
Commercially available silver powder ("SPQ03S", manufactured by Mitsui Kinzoku Kogyo KK) was prepared as the silver powder of Class VI.

<Evaluation of silver powder>
Particle size distribution of primary particles of silver powders of Class I to IV, decomposition rate of organic substance covering silver powder at a predetermined temperature (decomposition rate of organic substance), generation of organic substance covering silver powder when heated in powder state The type of gas to be heated (the type of gas generated by heating) was measured.

  The measurement of the particle size distribution of the primary particles of the silver powder was performed by observing the silver powder with an SEM (“S-4300SE” manufactured by Hitachi High-Technologies Corporation) and measuring the particle size of 1,000 silver particles. Here, the upper two values having the largest number of particle diameters were calculated, and the smaller one was defined as the particle diameter of the first peak, and the larger one was defined as the particle diameter of the second peak. Table 1 shows the particle diameters of the first peak and the second peak.

  The decomposition rate of the organic matter was obtained by measuring the amount of mass loss after heating after heating the silver powder at 150 ° C. for 30 minutes in the atmosphere.

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

The results of each measurement are shown in Table 1 below. Table 1 shows the time during which the aqueous silver nitrate solution and the aqueous ammonium citrate solution were simultaneously dropped, the rate of temperature rise and the maximum temperature of the silver powder slurry obtained by dropping the aqueous ammonium formate solution into the silver citrate slurry, and the holding temperature of each liquid. The type of the reducing agent aqueous solution is also described. Further, among the heat-generating gas species in Table 1, CO ₂ is gaseous carbon dioxide, and acetone, water, ethanediol, acetic acid, and pyrrole are evaporates thereof.

<Preparation of joining material>
(Example 1)
A silver powder of Class I, octylamine (molecular weight: 129.24) as an alkylamine, and hexylene glycol as a reducing organic solvent are put into a container in a blending ratio of 85: 5: 15 by mass ratio, and the mixture is kneaded (THINKY). A kneading material was obtained by performing kneading three times by rotating at a rotation speed of 2000 rpm for 5 minutes at a speed of 2000 rpm (manufactured by Awatori Neritaro).

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

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

(Example 4)
A bonding material was obtained in the same manner as in Example 1 except that ethylene glycol was used as the reducing organic solvent.

(Example 5)
A bonding material was obtained in the same manner as in Example 1, except that terpineol was used as the reducing organic solvent. However, Example 5 is not an example of the present invention but a reference example.

(Example 6)
A bonding material was obtained in the same manner as in Example 1, except that octanediol was used as the reducing organic solvent.

(Example 7)
A bonding material was obtained in the same manner as in Example 1, except that butyl carbitol was used as the reducing organic solvent. However, Example 7 is not an example of the present invention but a reference example.

(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 blending amounts of silver powder, octylamine, and hexylene glycol were 70:10:20.

(Example 11)
A bonding material was obtained in the same manner as in Example 1 except that the mixing amounts of silver powder, octylamine, and hexylene glycol were set to 90: 2: 8.

(Example 12)
A bonding material was obtained in the same manner as in Example 1 except that the blending amounts of silver powder, octylamine, and hexylene glycol were set to 80: 19: 1.

(Example 13)
A bonding material was obtained in the same manner as in Example 1 except that the blending amounts of silver powder, octylamine, and hexylene glycol were set to 80: 2: 18.

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

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

(Comparative Example 3)
A joining 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 dodecane was used as the reducing organic solvent.

(Comparative Example 5)
A bonding material was obtained in the same manner as in Example 1 except that polyethylene glycol (# 200) was used as the reducing 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 octylamine was not added and the mixing ratio of silver powder and hexylene glycol was set to 80:20.

  Table 2 below shows silver powder, alkylamine and reducing organic solvent used in the preparation of the bonding material of each example and each comparative example, and the amounts thereof. For silver powder, the particle diameters of the first peak and the second peak are also shown.

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

<Evaluation of bonding material>
For 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.

  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 evaluated as “OK”, and the bonding material in which solid-liquid separation occurred occurred was evaluated as “impossible”. Table 3 shows the results.

The viscosity change is measured by measuring the viscosity X of the bonding material immediately after preparation and the viscosity Y of the bonding material after being stored for 7 days in a temperature environment of 10 ° C., and the rate of change of the viscosity ( (1− Y / X )) × 100). A joining material having a rate of change of viscosity of 5% or less was evaluated as “OK”, and a bonding material exceeding 5% was evaluated as “impossible”. The viscosity was measured using a rheometer, and the shear rate at the time of measuring the viscosity was 10 [1 / s]. Table 3 shows the results.

<Preparation and evaluation of joined body>
A flexible wiring circuit board having a copper wiring layer as a copper substrate and a semiconductor chip as an electronic component were prepared.
Each bonding material obtained in the above Examples and Comparative Examples was applied to a copper wiring layer of a flexible circuit board, and a semiconductor chip (size: 2.5 mm × 2 mm) having a surface coated with silver was applied on the bonding material. (0.5 mm × thickness: 200 μm) and heated in an air atmosphere at a temperature of 150 ° C. for 30 minutes. As a result, a bonding layer was formed between the flexible circuit board and the semiconductor chip, and a bonded body was obtained.

  The shear strength of the bonding layer formed between the flexible circuit board and the semiconductor chip of the manufactured bonded body was measured. The shear strength is measured by using a bonding tester (manufactured by RHESCA) to measure the force required to break the bonding layer formed between the flexible circuit board and the semiconductor chip, and dividing the measured value by the bonding area. And Table 3 shows the results.

Further, in the evaluation of the joining material, both the presence or absence of solid-liquid separation and the change in viscosity are regarded as “OK”, and the shear strength of the joined body exceeding 20 MPa is judged as “判定”, and at least one of them is judged as Those that did not satisfy were judged as "x". Table 3 shows the results of the determination.

  The bonding material of Comparative Example 1 containing silver powder in which the first peak and the second peak of the particle size distribution of the primary particles were lower than the lower limit of the present invention could not change the viscosity. It is considered that this is because the aggregation of the silver powder progressed during storage because the primary particles of the silver powder were small.

  The bonding material of Comparative Example 2 including 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 did not show the presence or absence of solid-liquid separation and no change in viscosity. This is considered to be because the primary particles of the silver powder were large, and the particles settled down under their own weight.

  The joined body made using the joining material of Comparative Example 3 in which the peak of the particle size distribution of the primary particles contained one silver powder had low joining strength. This is considered to be because the primary particles used silver powder having no two peaks, so that the filling degree of the bonding layer was low and the bonding layer was brittle.

  The bonding material of Comparative Example 4 using dodecane as the reducing organic solvent had low bonding strength. This is considered to be because the oxide film on the copper surface could not be removed because dodecane had a low reducing action, and good sintering did not occur at the interface. The bonding material of Comparative Example 5 using polyethylene glycol as the reducing organic solvent had low bonding strength. It is presumed that many pores were formed inside the bonding layer due to the use of the polymer solvent, and the bonding layer was embrittled.

  The bonding material of Comparative Example 6 using butylamine as the alkylamine showed no solid-liquid separation and no change in viscosity. This is presumably because butylamine has a weak protective effect on silver powder. On the other hand, the joined body produced using Comparative Example 7 containing dodecylamine as the alkylamine had low joining strength of the joining layer. This is considered to be because dodecylamine has too strong a protective effect of silver powder, so that sintering does not proceed and the bonding layer is fragile.

  Furthermore, the bonding material of Comparative Example 8 containing no alkylamine was not capable of solid-liquid separation and had no change in viscosity. This is considered to be because the dispersibility of the silver powder was reduced because no amine was contained.

  On the other hand, the particle size distribution of the primary particles is as follows: 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 an alkylamine having a molecular weight of 101.19 to 157.30, and at least one reducing organic solvent selected from the group consisting of ethylene glycol, terpineol, hexylene glycol, butyl carbitol, and octanediol. In the bonding materials of Examples 1 to 13, solid-liquid separation did not occur, and the change in viscosity was suppressed. Moreover, the joined body manufactured using this joining material had excellent shear strength when the copper substrate was joined.

  The bonding material of the present invention may be used, for example, as a bonding material when bonding electronic components and the like on a copper substrate.

DESCRIPTION OF SYMBOLS 1 ... Silver salt aqueous solution 2 ... Carboxylate aqueous solution 3 ... Water 4 ... Silver carboxylate slurry 5 ... Reducing agent aqueous solution 11 ... Bonded body 12 ... Copper substrate 13 ... Bonding layer 14 ... Electronic components

Claims (5)

Silver powder having a primary particle size distribution having a first peak in a particle size range of 20 to 70 nm and a second peak in a particle size range of 200 to 500 nm;
An alkylamine having 6 to 10 carbon atoms and a molecular weight in the range of 101.19 to 157.30;
A bonding material comprising a reducing organic solvent (however, excluding dipropylene glycol monomethyl ether, butyl carbitol, methylpentanediol and terpineol ).   The joining material according to claim 1, wherein the content of the silver powder is in a range of 70 to 90% by mass.   The bonding material according to claim 1, wherein the silver powder includes secondary particles formed by agglomeration of primary particles, and the secondary particles have a particle size of 10 μm or less. 4.   4. The mass ratio A / B of the content A of the alkylamine to the content B of the reducing organic solvent is in the range of 0.1 or more and 19 or less. The bonding material according to claim 1.   A method of manufacturing a joined body in which a copper substrate and an electronic component are joined via a joining layer, wherein the joining layer is formed using the joining material according to any one of claims 1 to 4. Manufacturing method of the joined body.

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