JP2011175871A - Joining material, and joining method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a jointing material capable of obtaining a high jointing strength even under non-pressure or self-weight pressure. <P>SOLUTION: The jointing material contains two or more silver-based powder with different average particle sizes, and contains (1) as a first powder, the silver-based powder which consists of silver-based particles containing an organic component and silver and has an average particle size less than 10 nm, and (2) as a second powder, the silver-based powder which consists of silver-based particles containing silver and has an average particle size of 40 nm or more. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a novel bonding material and bonding method.

  In general, metal nanoparticles are ultrafine particles with a particle size of 1 to several hundred nanometers. Unlike bulk metals, they exhibit unique physical properties such as low melting point and low temperature sintering. It is used as a conductive paste for bonding and bonding.

The synthesis method of metal nanoparticles is a physical method of pulverizing bulk metal to obtain particles, and generating zero-valent metal atoms from precursors such as metal salts and metal complexes, and aggregating them to obtain nanoparticles There are two major categories: chemical methods. The pulverization method, which is one of the physical methods, is a method of obtaining metal nanoparticles by grinding a metal using an apparatus such as a ball mill. However, particles obtained by this method have a wide particle size distribution, and it is difficult to obtain particles having a size of several hundred nm or less. On the other hand, as chemical methods, 1) a method of synthesizing metal nanoparticles by heating a reaction gas with a CO ₂ laser called a laser synthesis method, and 2) a metal salt solution called a spray pyrolysis method is sprayed in a high temperature atmosphere. There are a method for obtaining metal nanoparticles by instantaneous evaporation and thermal decomposition of the solution, and 3) a method for obtaining metal nanoparticles by a reduction reaction from a metal salt solution called a reduction method. There are drawbacks.

  On the other hand, in order to solve the problems of the existing method for synthesizing metal nanoparticles, the present inventors have been able to synthesize metal nanoparticles simply by heating the metal complex as a metal source without solvent. The method has been developed first (Patent Document 1, Patent Document 2, etc.). The greatest feature of this thermal decomposition control method is the simplicity of heating without solvent, and therefore, mass synthesis is possible. Furthermore, it has been found that by adding an organic compound or the like having a mild reducing property to the reaction system, the reaction conditions become mild, and the particle diameter and shape, the design of the surface protective layer, and the like can be made.

  In general, it is known that metal nanoparticles are coarsened by spontaneously causing fusion between particles because atoms existing on the surface are very unstable. On the other hand, the metal nanoparticles obtained by the thermal decomposition control method as described above can be stabilized by taking measures such as covering the surface with an organic protective group. Such composite metal nanoparticles covered with an organic protective group or the like are expected to be used in a wide range of applications because they are more dispersible than ordinary metal nanoparticles.

  In particular, metal nanoparticles are expected as an alternative material such as high-temperature solder containing a large amount of lead, and joining techniques using metal nanoparticles are actively studied. For example, it is a bonding material for bonding members to be bonded to each other, with an oxidant that releases active oxygen in contact with or in proximity to composite nanoparticles in which the periphery of fine particles made of an inorganic material is coated with an organic material. A bonding material characterized by this has been proposed (Patent Document 3). It is said that high bonding strength can be obtained by using such metal nanoparticles. For example, in joining copper plates using silver nanoparticles, it is possible to obtain a high strength with a shear strength of 30 MPa or more.

JP 2007-63579 A JP 2007-63580 A JP2007-204778

  As described above, by using metal nanoparticles (powder) in metal bonding, it is possible to obtain higher bonding strength than before, but for that purpose, pressurization of materials to be bonded in the bonding process (up to 15 MPa). Is indispensable.

  On the other hand, particularly in the field of mounting electronic components, a predetermined bonding strength must be obtained even without external pressure due to the manufacturing process (or manufacturing apparatus).

  However, in general, in the joining of metals using metal nanoparticles as a joining material, the shear strength obtained with no pressure (or self-weight) is at most about 5 MPa, but in order to achieve higher joining strength. Further improvements are needed.

  Accordingly, a main object of the present invention is to provide a bonding material capable of obtaining higher bonding strength even under no pressure or under its own pressure.

  As a result of intensive studies in view of the problems of the prior art, the present inventor has found that the above object can be achieved by controlling to a specific composition using a powder composed of metal nanoparticles, and completes the present invention. It came to.

That is, the present invention relates to the following bonding material and bonding method.
1. A joining material containing two or more kinds of silver-based powders having different average particle diameters,
(1) The first powder is composed of silver-based particles containing an organic component and silver, and the average particle diameter is less than 10 nm, and (2) the second powder is composed of silver-based particles containing silver, and the average A bonding material comprising a silver-based powder having a particle size of 40 nm or more.
2. Item 2. The bonding material according to Item 1, wherein the second powder has an average particle size of 100 to 300 nm.
3. Item 3. The bonding material according to Item 1 or 2, further comprising a silver-based powder having silver-containing particles and an average particle diameter of 15 to 45 nm as the third powder.
4). Item 4. The bonding according to any one of Items 1 to 3, wherein the average particle size of the first powder is 6 to 9 nm, the average particle size of the second powder is 150 to 250 nm, and the average particle size of the third powder is 25 to 30 nm. Materials.
5. Item 5. The bonding material according to any one of Items 1 to 4, further comprising at least one of a solvent and a viscosity adjusting resin.
6). Item 6. The bonding material according to any one of Items 1 to 5, which is used for bonding under no pressure or under its own pressure.
7). 7. A joining method including a step of heating at 150 to 400 ° C. after interposing the joining material according to any one of Items 1 to 6 between two members to be joined.
8). Item 8. The joining method according to Item 7, wherein the step is performed under no pressure or under its own pressure.

  According to the present invention, since a mixed powder of two or more kinds of silver-based powders having a specific average particle diameter is included, higher filling properties and sintering properties are set, resulting in higher bonding. Strength can be obtained. In particular, even under no pressure or under its own pressure, it is possible to develop a higher bonding strength than in the prior art. Moreover, by further blending the third powders having different average particle diameters, it is possible to achieve higher bonding strength.

  The bonding material of the present invention having such characteristics can be suitably used not only for general bonding but also for bonding electronic parts or wirings that are required to be bonded under no pressure or under its own pressure. That is, it is particularly useful as a bonding material used for forming an electrical bonding region.

It is a figure which shows the shape and arrangement | positioning method of the sample piece (member) used for the joining test. Fig.1 (a) shows the shape and size of each member, and the joining method of both members. FIG.1 (b) is a figure which shows a state when performing a shear test to a conjugate | zygote. It is a graph which shows the relationship between the joining temperature and joining strength of the joined sample. The SEM photograph of the torn surface after the shear test of the sample by a comparison paste (joining temperature of 300 degreeC) is shown. The SEM photograph of the torn surface after the shear test of the sample by the paste 2 (joining temperature of 300 degreeC) is shown. The SEM photograph of the torn surface after the shear test of the sample by the paste 1 (joining temperature of 300 degreeC) is shown. The SEM photograph of the torn surface after the shear test of the sample by the paste 1 (joining temperature 350 degreeC) is shown. In Test Example 2, it is a graph showing the shear strength of each sample joined at 200 ° C. The SEM photograph of the torn surface after the shear test of the sample 1 (FIG. 8 (a)) and the sample 4 (joining temperature 200 degreeC) (FIG.8 (b)) by the paste 1 (joining temperature 200 degreeC) is shown.

1. Bonding material The bonding material of the present invention (the material of the present invention) is a bonding material containing two or more kinds of silver-based powders having different average particle sizes,
(1) The first powder is composed of silver-based particles containing an organic component and silver, and the average particle diameter is less than 10 nm, and (2) the second powder is composed of silver-based particles containing silver, and the average It contains a silver-based powder having a particle size of 40 nm or more.

The 1st powder 1st powder uses the powder which consists of an organic component and silver type particle | grains containing silver. Although the kind of organic component is not particularly limited, it is usually preferable that the organic component is composed of an organic compound used as a starting material or a thermal decomposition product thereof. In this case, the content of the organic component is not limited, but it is preferably adjusted so that the metal content of the silver-based fine particles is usually 60 to 98% by weight, particularly 75 to 98% by weight.

  The average particle size of the first powder (silver-based powder) is usually 10 nm or less, and particularly preferably 8 nm or less. By setting within this range, high bonding strength can be obtained even under no pressure or under its own pressure. The lower limit value of the average particle diameter is not limited, but generally it may be about 1 nm or more.

  As the first powder itself, a known or commercially available product can be used. Moreover, the silver type powder obtained by a well-known manufacturing method can also be used. The production method may be any of a liquid phase method, a solid phase method, and a gas phase method. For example, a silver-based powder obtained by the following method can be suitably used. That is, in the present invention, for example, a silver-based powder obtained by heat-treating a starting material containing a metal salt in the presence of an amine compound can be preferably used. Hereinafter, this method (the production method of the present invention) will be described as a representative example.

  Examples of metal salts (Ag salts) include inorganic acid salts such as nitrates, chlorides, carbonates and sulfates; organic acid salts such as stearates and myristates, and metal complexes (complex salts). Can do. In particular, in the present invention, at least one metal salt (Ag salt) of (1) metal carbonate, (2) fatty acid salt and (3) metal complex can be preferably used.

As the fatty acid salt, R ¹ —COOH or HOOC—R ¹ —COOH (where R ¹ represents a hydrocarbon group having 7 or more carbon atoms (particularly 7 to 17) which may have a substituent. ) Or HOOC-R ² —COOH (wherein R ² represents a hydrocarbon group having 3 or more carbon atoms and optionally having a substituent), a metal salt of a fatty acid is preferred. The hydrocarbon groups R ¹ and R ² may be either saturated or unsaturated.

Moreover, as a metal complex, the metal complex containing a carboxylate ligand is preferable. As such a metal complex, a monodentate ligand or OOC represented by R ¹ COO (where R ¹ represents a hydrocarbon group having 7 or more carbon atoms and optionally having a substituent). Any of bidentate ligands (including chelate ligands) represented by —R ² —COO (where R ² represents a hydrocarbon group) may be used. In the case of a monodentate ligand, a linear alkyl group is preferred. In the case of a bidentate ligand, a linear methylene group is preferred. The hydrocarbon group R ¹ preferably has 7 to 30 carbon atoms, and more preferably has 7 to 17 carbon atoms. The hydrocarbon group R ² may be any of a saturated hydrocarbon group such as a methylene group; and an unsaturated hydrocarbon group such as a phenyl group, a propylene group, and a vinylene group. The number of carbon atoms of the hydrocarbon group R ² is not limited, but is preferably about 6 to 12.

  As long as the metal complex has a carboxylate ligand, the metal complex may have another ligand such as a phosphine ligand.

Examples of the metal complex in the present invention include, for example, the general formula M (R ¹ R ² R ³ P) (O ₂ CR ′) (M represents Ag. R ^{1 to} R ³ and R ′ may be the same or different from each other). It is different and represents a cyclohexyl group, a phenyl group or an alkyl group having 1 to 30 carbon atoms which may have a substituent. Examples of the substituent in a) include a methyl group, an ethyl group, a propyl group, a sulfone group, an OH group, a nitro group, an amino group, a halogen group (Cl, Br, etc.), a methoxy group, and an ethoxy group. . The position and number of substituents are not particularly limited. Specific examples thereof include, for example, a metal represented by M (PPh ₃ ) (O ₂ CC _n H _{2n + 1} ) (where M represents Ag, Ph represents a phenyl group, and n represents 7 to 17). Complexes can also be used.

  Moreover, in this invention, another component can also be made to contain in a starting material as needed. For example, a fatty acid or a salt thereof can be added. Preferably, as the fatty acid, the same fatty acid as that in the fatty acid salt can be used. The content and the like can be appropriately set according to the type of starting material used.

  In the production method of the present invention, the starting material containing the metal component as described above is heat-treated in the presence of an amine compound. In particular, in the present invention, a starting material containing a metal component and an amine may be charged into a reaction vessel and heat-treated without using an organic solvent. When the amine is solid, the starting material containing the metal component and the amine may be heat-treated while being solid.

  The kind of the amine compound is not particularly limited even if it is any of primary amine, secondary amine, and tertiary amine.

As the primary amine, those represented by the general formula RNH ₂ (where R represents a hydrocarbon group having 8 or more carbon atoms) are particularly preferred. For example, octylamine _C 8 _H 17 NH _2, laurylamine _C 12 _H 25 NH _2, stearylamine _C 18 _H 37 NH ₂ and the like.

The secondary amine is particularly represented by the general formula R ¹ R ² NH (wherein R ¹ and R ² are the same or different from each other and represent a hydrocarbon group having 2 to 8 carbon atoms). Is preferred. For example, diethylamine _{(C 2 H 5) 2 NH} , dihexylamine _{(C 6 H 13) 2 NH} , dioctylamine _{(C 8 H 17)} 2 NH, and the like.

The tertiary amine is particularly represented by the general formula R ¹ R ² R ³ N (wherein R ^{1 to} R ³ are the same or different from each other and represent a hydrocarbon group having 2 to 8 carbon atoms). Are preferred. Examples thereof include triethylamine (C ₂ H ₅ ) ₃ N, tripropylamine (C ₃ H ₇ ) ₃ N, trioctylamine (C ₈ H ₁₇ ) ₃ N, and the like.

  The usage-amount of an amine compound will not be specifically limited if it is equimolar or more with the starting material containing a metal component. Therefore, an excessive amount may be used as necessary. The amine compound can also be used after being dissolved or dispersed in a suitable organic solvent in advance.

  The heat treatment temperature is not particularly limited as long as the metal salt reacts with the amine compound to obtain predetermined metal nanoparticles, and can be appropriately determined according to the type of metal salt and amine compound used. In general, the temperature may be set in a range of 50 ° C. or higher, and in particular, the temperature may be set to a temperature range above the temperature at which the mixture of the starting material and the amine compound finally becomes liquid and below the boiling point of the amine compound. preferable. That is, the formation of metal nanoparticles composed of a substance containing at least one of P, N, and O can be more effectively advanced by heat treatment at a temperature equal to or higher than the temperature at which the mixture finally becomes a molten state. it can.

  The heat treatment time may be appropriately set according to the type of starting material to be used, the heat treatment temperature, etc., but is usually about 1 to 10 hours, preferably 3 to 8 hours.

  The heat treatment atmosphere may be any of an oxidizing atmosphere, air, reducing atmosphere, inert gas, and the like, and can be appropriately set according to, for example, the metal species of the metal salt. Moreover, as said inert gas, what is necessary is just to use inert gas, such as nitrogen, a carbon dioxide, argon, helium, for example.

  After the heat treatment is completed, purification is performed as necessary. As a purification method, a known purification method can be applied, and for example, washing, centrifugation, membrane purification, solvent extraction and the like may be performed.

Second powder The second powder is composed of silver-based particles containing silver. The second powder forms a skeleton including voids filled with the first powder, and a desired high strength can be achieved by the combined use with the first powder. The second powder is not limited as long as it contains silver, and in addition to powder made of silver particles (particles of silver alone), powder made of silver-based particles containing organic components and silver like the first powder. It may be. When using the powder which consists of an organic component and silver type particle | grains containing silver, the thing similar to a 1st powder can be used, and it can also manufacture by the said this invention manufacturing method.

  The average particle diameter of the second powder is usually 40 nm or more, particularly preferably 100 nm or more, and more preferably 150 nm or more. The upper limit of the average particle diameter of the second powder is not particularly limited, but is generally 400 nm or less, preferably 300 nm or less, more preferably 250 nm or less.

Third Powder In the present invention, it is preferable that a silver-based powder having an average particle diameter between the first powder and the second powder is further included as the third powder. By including the third powder, it is possible to achieve higher bonding strength.

  As the third powder, a powder made of silver-based particles containing silver can be used. That is, similar to the second powder, in addition to the powder made of silver particles (particles of silver alone), the powder made of silver-based particles containing an organic component and silver like the first powder may be used. When using the powder which consists of an organic component and silver type particle | grains containing silver, the thing similar to a 1st powder can be used, and it can also manufacture by the said this invention manufacturing method.

  The average particle diameter of the third powder is not limited as long as it has an average particle diameter between the first powder and the second powder used as described above. For example, when the average particle size of the second powder is about 100 to 300 nm, a silver-based powder having an average particle size of about 15 to 45 nm can be suitably used as the third powder.

  In the present invention, the third powder may be one type or two or more types (that is, two or more types having different average particle diameters).

Preparation of mixed powder In the present invention, the material of the present invention can be obtained by uniformly mixing these silver-based powders. That is, it can be provided as a bonding material including a mixed powder obtained by mixing at least the first powder and the second powder.

  The mixing method may be dry mixing or wet mixing using a solvent or the like. The mixing ratio of each powder is not limited, and can be appropriately set according to desired bonding strength, average particle diameter of powder, and the like. For example, the second powder can be 100 to 800 parts by weight, preferably 150 to 600 parts by weight, and more preferably 150 to 550 parts by weight with respect to 100 parts by weight of the first powder. The third component can be 100 to 300 parts by weight, preferably 150 to 250 parts by weight, and more preferably 150 to 200 parts by weight with respect to 100 parts by weight of the first powder.

  The material of the present invention may be a mixed powder (solid content) or a liquid (paste). When it is made liquid, it can be provided as a paste containing the mixed powder and at least one of a solvent and a viscosity adjusting resin.

  The solvent is not particularly limited. Examples include terpene solvents, ketone solvents, alcohol solvents, ester solvents, ether solvents, aliphatic hydrocarbon solvents, aromatic hydrocarbon solvents, cellosolve solvents, carbitol solvents, and the like. More specifically, organic solvents such as terpineol, methyl ethyl ketone, acetone, isopropanol, butyl carbitol, decane, undecane, tetradecane, benzene, toluene, hexane, diethyl ether, and kerosene can be used.

  The viscosity adjusting resin is not particularly limited. For example, a thermosetting resin such as a phenol resin, a melamine resin, or an alkyd resin, a thermoplastic resin such as a phenoxy resin or an acrylic resin, a curing agent curable resin such as an epoxy resin, or the like can be used.

  In addition, when preparing paste, solid content of mixed powder can be suitably set in the range of about 20 to 90% by weight.

  The material of the present invention can be suitably used particularly for bonding. For example, it can be suitably used for joining metals (for example, copper-based metal-copper-based metal, silver-based metal-copper-based metal, etc.). More specifically, an electrical junction region can be suitably formed using the material of the present invention. Thereby, two circuits can be joined. The joining method is, for example, 2. It can carry out according to the method of.

2. Joining Method The present invention includes a joining method including a step of heating at 150 to 400 ° C. after interposing the material of the present invention between two members to be joined.

  Examples of members to be joined include metals (including alloys and intermetallic compounds), ceramics, plastics, composite materials of these, and the like. In the present invention, metals (joining of metals) are particularly preferable. Further, the shape of the member is not particularly limited as long as the material of the present invention can be appropriately disposed between the members.

  In the joining method of the present invention, the material of the present invention (powder, paste, etc.) is interposed between the members to be joined.

  The amount of the material of the present invention is not particularly limited, and may be set as appropriate so that the amount can be uniformly interposed over the entire bonding surface. In addition, when using the paste containing a solvent, after interposing a paste between members, it is preferable to implement the pre-processing for evaporating one part or all part of the solvent prior to heat processing. Examples of the pretreatment method include a method of heating at about 100 to 150 ° C.

  Next, heat treatment is performed at 150 to 400 ° C. The heat treatment temperature can be appropriately set according to, for example, the type of mixed powder to be used, the desired bonding strength, the material of the member, and the like. The heat treatment atmosphere is not particularly limited, and for example, the heat treatment atmosphere can be performed in any of an oxidizing atmosphere, air, reducing atmosphere, and inert gas.

  Moreover, when heat-treating, the members to be joined may be heat-treated while being pressed, or may be heat-treated under no pressure or under its own pressure. In particular, the present invention is characterized in that a relatively high bonding strength can be obtained even under no pressure or under its own pressure. In the case of pressurization, the pressure can be appropriately set within a range of, for example, about 1 to 20 MPa.

  The heat treatment time can be appropriately set according to the heat treatment temperature and the like, but is usually about 1 second to 60 minutes. In this way, it is possible to obtain a joined body in which a fired body (sintered body) of the material of the present invention is interposed as an adhesive between members.

  The features of the present invention will be described more specifically with reference to examples. However, the scope of the present invention is not limited to the examples. In addition, the measurement of the physical property etc. in an Example was implemented in accordance with the following method.

(1) Qualitative analysis The metal component was identified by powder X-ray diffraction analysis using a powerful X-ray diffractometer "RINT 2500V" (manufactured by Rigaku Corporation).
(2) Average particle diameter Measured with a transmission electron microscope (TEM) “JEM-2100” (manufactured by JEOL Ltd.), an arithmetic average value of the diameters of 100 arbitrarily selected particles was obtained, and the average particle diameter was obtained from the value. It was.
(3) Content of metal component The content was determined by TG / DTA analysis using a thermal analyzer “SSC / 5200” (Seiko Electronics Co., Ltd.).
(4) Analysis of organic component etc. Confirmation of P (phosphorus component), N (nitrogen component) and O (oxygen component) in metal nanoparticles is performed by X-ray photoelectron spectrum apparatus “ESCA-700” (manufactured by ULVAC-PHI), FT-IR apparatus “GX I-RO” (manufactured by PerkinElmer) was used. The organic component was confirmed using an FT-NMR apparatus “JNM-EX270” (manufactured by JEOL Ltd.) and a GC / MS (gas chromatograph mass spectrometer) apparatus “5973 Network MSD” (manufactured by Hewlett-Packard Company).

Example 1
(1) Preparation of first powder, etc. (1-1) Preparation of first powder Silver carbonate (41.4 g) and octylamine (40.7 g) are placed in a solid state in a Pyrex (registered trademark) three-necked flask. And gradually heated to 100 ° C. in the atmosphere. After maintaining at 100 ° C. for 4 hours, the mixture was allowed to cool to 70 ° C., washed with methanol several times, and the produced powder was filtered off with a Kiriyama funnel and dried under reduced pressure to obtain a silver-based powder. The obtained powder had an average particle size of 7.9 nm and a metal content of 72% by weight.
(1-2) Preparation of Second Powder A silver-based powder was obtained according to the method (1-1). The average particle size of the obtained powder was 200 nm, and the metal content was 97% by weight.
(1-3) Preparation of Third Powder A silver-based powder was obtained according to the method (1-1). The obtained powder had an average particle size of 28 nm and a metal content of 94% by weight.

(2) Preparation of mixed powder (2-1) Preparation of paste 1 The above-mentioned first powder, second powder and third powder are mixed at 12.25 wt%, 65 wt% and 22.75 wt%, respectively. A mixed powder was prepared. The obtained mixed powder was dispersed in terpineol to prepare paste 1 having a solid concentration of about 70% by weight.
(2-2) Preparation of Paste 2 A mixed powder was prepared by mixing the first powder and the second powder at 35 wt% and 65 wt%, respectively. The obtained mixed powder was dispersed in terpineol to prepare paste 2 having a solid concentration of about 70% by weight.

Test example 1
The joining test was implemented using the paste obtained in the Example. For comparison, a similar joining test was performed using a comparative paste prepared in the same manner using only the first powder.

  The shape of a joining test piece made of oxygen-free copper used in the joining test is shown in FIG. The joint surface of each test piece was finished by lathe processing so that Rmax = 3.2S, and after ultrasonic cleaning in acetone and pickling in hydrochloric acid, it was subjected to water washing and drying, and then subjected to the test. . A fixed amount of paste was applied to the joining surface of the larger disc test piece, and the joining test piece was adjusted so that the paste spread over the entire joining surface while overlapping and lightly pressing the smaller test piece. The test piece was heated to a predetermined holding temperature over 5 minutes, and then a bonding test in the atmosphere was performed at a bonding temperature (heat treatment temperature) of 250 to 350 ° C. When joining, no external pressure is applied and only the self-weight pressure is used. 1) Sample with holding temperature 250 ° C. × holding time 5 minutes, 2) Sample with holding temperature 300 ° C. × holding time 5 minutes, 3) Holding temperature Samples were prepared at 350 ° C. and holding time of 5 minutes.

  About the sample obtained by the joining test, the shear test was performed as shown in FIG.1 (b) using the Instron universal material testing machine, and each joining strength was calculated | required. The result is shown in FIG. FIG. 2 shows the results in FIG. 2 where “▲” uses the paste 1, “■” uses the paste 2, and “●” denotes the comparison paste.

  As is clear from the results of FIG. 2, the comparative paste shows a relatively high strength at a bonding temperature of 250 ° C., but decreases with an increase in the bonding temperature. On the other hand, with paste 2, the strength increases as the bonding temperature increases, and with paste 1, it reaches about 250 N at a bonding temperature of 350 ° C., indicating that high strength of 100 N (particularly 200 N) or more can be achieved. . That is, like paste 1, the average particle diameter of the first powder is 6 to 9 nm, the average particle diameter of the second powder is 150 to 250 nm, and the average particle diameter of the third powder is 25 to 30 nm. It can be seen that by controlling within the range, higher bonding strength can be obtained even under the self-weight.

  In FIGS. 3-6, the SEM photograph of the torn surface after a shear test is shown about the sample joined using various metal nanoparticle paste. 3 is a sample by comparison paste (joining temperature: 300 ° C.), FIG. 4 is a sample by paste 2 (joining temperature: 300 ° C.), FIG. 5 is a sample by paste 1 (joining temperature: 300 ° C.), and FIG. Samples with a bonding temperature of 350 ° C. are shown. In the sample using the comparative paste, cracks were conspicuous, whereas in the samples using pastes 1 and 2, there was no such defect, but a clear elongated dimple was observed.

Test example 2
A sample (sample 1) made of paste 1 was prepared in the same manner as in Test Example 1 except that the bonding temperature was 200 ° C. (holding time 30 minutes), and the bonding strength was measured. For comparison, the bonding strength of the following three samples was measured. The result is shown in FIG.

  Sample 2: A paste having a solid content concentration of about 70% by weight was prepared by dispersing 65% by weight of a commercially available silver powder (average particle size: 5 μm) containing no organic component and 35% by weight of the first powder in terpineol. A sample was prepared in the same manner as in Test Example 1 except that the obtained paste was used and the bonding temperature was set to 200 ° C.

  Sample 3: A commercially available silver powder (average particle size: 300 nm) containing 65% by weight and organic powder containing 35% by weight of the first powder was dispersed in terpineol to prepare a paste having a solid content of about 70% by weight. A sample was prepared in the same manner as in Test Example 1 except that the obtained paste was used and the bonding temperature was set to 200 ° C.

  Sample 4: A paste having a solid content of about 70% by weight was prepared by dispersing only the first powder in terpineol. A sample was prepared in the same manner as in Test Example 1 except that the obtained paste was used and the bonding temperature was set to 200 ° C.

  As is clear from the results of FIG. 7, the sample 4 (comparative product) using silver-based nanoparticles alone has a bonding strength of about 80 N, while the samples 1 to 3 (product of the present invention) are more than the sample 4. As can be seen from FIG. Moreover, it turns out that desired intensity | strength can be achieved even if it is the silver type powder which does not contain an organic component as a 2nd powder like the samples 2-3.

  Moreover, about the sample 1 and the sample 4, the SEM photograph of the torn surface after a shear test is shown to Fig.8 (a) and (b). As is clear from the results of FIG. 8, in Sample 4, many voids were observed on the fracture surface (FIG. 8B), while in Sample 1, a relatively dense fracture surface was maintained. (FIG. 8A). That is, it can be seen that the bonding material of the present invention can form a high-strength bonding layer because it is dense.

Claims (8)

A joining material containing two or more kinds of silver-based powders having different average particle diameters,
(1) The first powder is composed of silver-based particles containing an organic component and silver, and the average particle diameter is less than 10 nm, and (2) the second powder is composed of silver-based particles containing silver, and the average A bonding material comprising a silver-based powder having a particle size of 40 nm or more. The bonding material according to claim 1, wherein the second powder has an average particle size of 100 to 300 nm. The bonding material according to claim 1 or 2, further comprising a silver-based powder having silver-containing particles and an average particle diameter of 15 to 45 nm as the third powder. The bonding material according to claim 3, wherein the average particle diameter of the first powder is 6 to 9 nm, the average particle diameter of the second powder is 150 to 250 nm, and the average particle diameter of the third powder is 25 to 30 nm. The bonding material according to claim 1, further comprising at least one of a solvent and a viscosity adjusting resin. The bonding material according to claim 1, which is used for bonding under no pressure or under its own pressure. The joining method including the process of heating at 150-400 degreeC, after interposing the joining material in any one of Claims 1-6 between the two members which should be joined. The joining method according to claim 7, wherein the step is performed under no pressure or under its own pressure.