Bonding paste, bonded body using same, and method for manufacturing bonded body

Abstract

To provide a paste for joining which has low viscosity, and with which a joined body excellent in coating adaptability, in viscosity stability over time, and in initial and after thermal cycle test joining strength can be formed.SOLUTION: A paste for joining contains metal particles (A) coated with an organic constituent (a), a dispersion medium (B) and a resin (C), and contains 0.015-1.4 mass% of the resin (C). In the metal particles (A), a particle size (d1) corresponding to 1% of cumulative particle diameter distribution is 30-200 nm, a particle size (d50) corresponding to 50% thereof is 100-350 nm, and a particle size (d99) corresponding to 99% thereof is 300-900 nm, an extrapolation ending temperature (Te) of an exothermic peak of the highest temperature side of the metal particles (A) measured by differential thermal analysis is 200-300°C, and when a mass of the metal particles (A) at an extrapolation starting temperature (Ts) of an exothermic peak of the lowest temperature side of the metal particles (A) is set to be 100 mass%, the mass reduction ratio of the metal particles (A) at Te is 0.2-5 mass%.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bonding paste, a bonded body using the same, and a method for producing the same. [Background technology]

[0002] Conventionally, solder has been used as a bonding material for bonding metal members together, between a metal member and a semiconductor element, or between a metal member and an LED element, etc. In the field of next-generation power electronics, there is a demand for alternatives to solder as a bonding material for devices such as SiC that can operate at high temperatures from the viewpoint of high-temperature operation reliability, and for example, the use of bonding pastes using metal particles has been proposed as shown in Patent Documents 1 to 3.

[0003] Patent documents 1 and 2 propose a bonding paste using so-called metal nanoparticles with an average particle size of less than 100 nm, but the organic component (a) contained in the nanoparticles remains in the coating film, causing a decrease in bonding strength and a decrease in bonding strength after environmental testing. In addition, the viscosity is high and the applicability is poor. In order to solve the above problems, Patent document 3 proposes a bonding paste that uses metal nanoparticles with an average particle size of 100 nm or less in combination with metal microparticles with an average particle size of 0.5 μm or more, but the dispersibility of the metal particles cannot be sufficiently ensured, the applicability is poor, and the smoothness / leveling of the bonding film after application cannot be ensured. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2011 / 007402 issue [Patent Document 2] JP 2011-46770 A [Patent Document 3] WO2011 / 155615 Summary of the Invention [Problem to be solved by the invention]

[0005] Bonding pastes that use metal particles are required to satisfy all of the following requirements: (1) sufficient bonding strength must be obtained after sintering, (2) the bonding strength must be maintained after environmental testing such as thermal cycles, and (3) the bonding paste must have optimal flow properties for printing / spraying.

[0006] The problem to be solved by the present invention is to provide a bonding paste which has a low viscosity, is excellent in applicability and viscosity stability over time, and is capable of forming a bonded body having excellent initial bonding strength and after a thermal cycle test. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have arrived at the present invention. That is, the present invention relates to a joining paste comprising metal particles (A) coated with an organic component (a), a dispersion medium (B), and a resin (C), the resin (C) being contained in an amount of 0.015 to 1.4 mass %, the metal particles (A) having a particle diameter (d1) corresponding to 1% of the cumulative particle diameter distribution of 30 to 200 nm, a particle diameter (d50) corresponding to 50% of the cumulative particle diameter distribution of 100 to 350 nm, and a particle diameter (d99) corresponding to 99% of the cumulative particle diameter distribution of 300 to 900 nm, an extrapolated end temperature (Te) of the highest heat generation peak of the metal particles (A) determined by differential thermal analysis of 200 to 300°C, and a mass reduction rate of the metal particles (A) at Te of 0.2 to 5 mass %, when the mass of the metal particles (A) at the extrapolated start temperature (Ts) of the lowest heat generation peak of the metal particles (A) determined by differential thermal analysis is taken as 100 mass %.

[0008] The present invention also relates to the above bonding paste, in which a ratio of metal particles (A) / resin (C) is 99 / 1 to 99.97 / 0.03 (mass ratio).

[0009] The present invention also relates to the above bonding paste, wherein the resin (C) contains a thermosetting resin.

[0010] The present invention also relates to the above bonding paste, in which a ratio of metal particles (A) / dispersion medium (B) is 80 / 20 to 95 / 5 (mass ratio).

[0011] The present invention also relates to the above-mentioned bonding paste, wherein the dispersion medium (B) contains one or more selected from the group consisting of terpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyrolactone, and dipropylene glycol monomethyl ether.

[0012] The present invention also relates to the above bonding paste, which has a viscosity of 1 to 150 Pa·s.

[0013] The present invention also relates to a bonded body in which a first body and a second body are bonded with the bonding paste.

[0014] The present invention also relates to a method for producing a bonded body, comprising applying the bonding paste to a first body to be bonded and placing a second body to be bonded on the applied surface. Effect of the Invention

[0015] The present invention provides a bonding paste that has low viscosity, is excellent in applicability and viscosity stability over time, and is capable of forming a bonded body having excellent initial bonding strength and after a thermal cycle test. [Brief description of the drawings]

[0016] [Figure 1] FIG. 2 is a schematic diagram showing the results of measurement of the metal particles of the present invention using a simultaneous thermogravimetry-differential thermal analyzer (TG-DTA). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The bonding paste of the present invention contains metal particles (A) coated with an organic component (a) (hereinafter may be abbreviated as "metal particles (A)"), a dispersion medium (B), and a resin (C). The metal particles (A), the dispersion medium (B), and the resin (C) will be described below.

[0018] (Metal particles (A)) Examples of the metal in the metal particles (A) include gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, platinum, and alloys thereof. In addition, fine particles coated with a core and a material different from the core material, specifically, for example, silver-coated copper powder, in which the core is copper and the surface is coated with silver, can be mentioned. In addition, powders of metal oxides such as silver oxide, indium oxide, tin oxide, zinc oxide, ruthenium oxide, ITO (tin-doped indium oxide), AZO (aluminum-doped zinc oxide), and GZO (gallium-doped zinc oxide), as well as powders surface-coated with these metal oxides can be mentioned. The type of metal used may be one type, or two or more types may be used in combination.

[0019] In the present invention, it is important to use metal particles (A) whose 1% cumulative particle size distribution particle size (d1), 50% cumulative particle size distribution particle size (d50), and 99% cumulative particle size distribution particle size (d99) are controlled. The 1% cumulative particle size distribution particle size (d1), 50% cumulative particle size distribution particle size (d50), and 99% cumulative particle size distribution particle size (d99) of the metal particles (A) are measured for the dispersion obtained by dispersing the metal particles (A) in an organic solvent (IPA: isopropyl alcohol) to 0.5 mass% using an ultrasonic disperser. For example, Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) can be used for the measurement. In this specification, the 1% cumulative particle size distribution particle size (d1), 50% cumulative particle size distribution particle size (d50), and 99% cumulative particle size distribution particle size (d99) refer to particle sizes (volume basis) corresponding to 1%, 50%, and 99% of the cumulative particle size distribution, respectively.

[0020] The 1% cumulative particle size distribution particle size (d1) is 30 to 200 nm, preferably 30 to 150 nm, and more preferably 30 to 100 nm. The 50% cumulative particle size distribution particle size (d50) is 100 to 350 nm, preferably 100 to 300 nm, and more preferably 100 to 250 nm. The 99% cumulative particle size distribution particle size (d99) is 300 to 900 nm, preferably 300 to 750 nm, and more preferably 300 to 600 nm.

[0021] It is believed that smaller metal particles are covered with relatively more organic component (a) than larger metal particles. Therefore, by using relatively large metal particles, it is possible to suppress the organic component derived from the organic component (a) from remaining in the bonding material (hereinafter also referred to as the bonding coating film), suppress the occurrence of voids in the bonding coating film, and increase the bonding strength. On the other hand, larger metal particles have a relatively higher melting point than smaller metal particles. Therefore, by using relatively small metal particles, it is possible to sufficiently promote the melting and integration (hereinafter also referred to as sintering) between the metal particles without using a significantly high temperature, form a dense bonding coating film, and suppress the decrease in bonding strength after thermal cycles.

[0022] That is, from the viewpoint of preventing the occurrence of voids in the bonded coating, it is important that the metal particles are not too small, and from the viewpoint of ease of sintering, the metal particles are not too large. Furthermore, the 1% cumulative particle size distribution particle size (d1) is important for suppressing the occurrence of voids, and the 99% cumulative particle size distribution particle size (d99) is important for ease of sintering. If the metal particles are uniform in size (particle size), the gaps between the metal particles in the coating film being formed during the bonding process cannot be filled sufficiently, which causes voids in the bonded coating film. By providing a distribution in the size (particle size) of the metal particles, it becomes possible to effectively fill the gaps between the metal particles and suppress the occurrence of voids in the bonded coating film. For the above reasons, the ranges of the 1% cumulative particle size distribution particle size (d1), 50% cumulative particle size distribution particle size (d50), and 99% cumulative particle size distribution particle size (d99) mentioned above are necessary.

[0023] The metal particles (A) may be used alone in a specific particle size range, or a combination of multiple particles in different particle size ranges may be used. The single or combined metal particles may have any particle size within the above-mentioned ranges, namely, 1% cumulative particle size distribution particle size (d1), 50% cumulative particle size distribution particle size (d50), and 99% cumulative particle size distribution particle size (d99).

[0024] FIG. 1 is a schematic diagram showing the DTA curve and the TG curve during the temperature rise. As shown in FIG. 1, the start temperature Ts of the lowest temperature side exothermic peak shown in the DTA curve means the extrapolation start temperature, and is the temperature of the intersection between a straight line extending the baseline on the low temperature side to the high temperature side in the heating measurement and a tangent drawn at the point where the gradient is maximum on the curve of the lowest temperature side of the exothermic peak. Similarly, the end temperature Te of the highest temperature side exothermic peak shown in the DTA curve means the extrapolation end temperature, and is the temperature of the intersection between a straight line extending the baseline on the high temperature side to the low temperature side in the heating measurement and a tangent drawn at the point where the gradient is maximum on the curve of the highest temperature side peak. And, it is considered that the decomposition of the organic component (a) starts from the extrapolation start temperature Ts of the lowest temperature side exothermic peak, the mass of the metal particles starts to decrease, and the decomposition of the organic component (a) ends at the extrapolation end temperature Te, so Ts is also called the decomposition start temperature and Te is also called the decomposition end temperature. That is, the mass reduction rate below is understood to be the amount of the organic component (a). Mass reduction rate = [(mass of metal particles (A) at Ts - mass of metal particles (A) at Te) / mass of metal particles (A) at Ts] x 100 Although some mass loss of metal particles may be observed in the lower temperature range than Ts or higher temperature range than Te, if no clear exothermic peak is observed, it is not considered to be due to decomposition.

[0025] Examples of the organic component (a) include fatty acids, aliphatic amines, and aliphatic alcohols, and are preferably saturated or unsaturated fatty acids, more preferably saturated or unsaturated fatty acids having a carbon number of 3 to 22, and even more preferably saturated or unsaturated fatty acids having a carbon number of 6 to 18. The organic component (a) may contain one or more types.

[0026] It is important that Te in the metal particles (A) is 200° C. or more and 300° C. or less, and preferably 200° C. or more and 280° C. or less. It is important that the amount of the organic component (a) in the metal particles (A) is 0.2 to 5 mass %, preferably 0.2 to 2 mass %, and more preferably 0.4 to 1 mass %.

[0027] By setting Te to 200°C or higher, the viscosity of the bonding paste can be kept stable even after long-term storage. By setting Te to 300°C or lower, metal particles can be sufficiently sintered without heating to extremely high temperatures, and good bonding strength can be achieved not only initially but also after environmental testing. However, if Te exceeds 300°C, it is not preferable because there is a risk of thermal damage to the bonded components.

[0028] By making the amount of the organic component (a) in the metal particles (A) 0.2% by mass or more, it is possible to prevent the bonding paste from becoming too viscous, to exhibit good coating performance, to form a dense bonding coating film, and to exhibit good bonding strength. On the other hand, by making the amount of the organic component (a) in the metal particles (A) 5% by mass or less, it is possible to prevent the organic component (a) from remaining after sintering, to prevent the occurrence of voids in the bonding coating film, and to exhibit good bonding strength.

[0029] The organic component (a) of the metal particles (A) in the present invention is not particularly limited as long as it satisfies the above-mentioned thermal decomposition conditions, and for example, saturated or unsaturated fatty acids having 3 to 22 carbon atoms can be used.

[0030] The bonding paste of the present invention contains a dispersion medium (B). The dispersion medium (B) contains metal particles (A). It has the function of dispersing. The dispersion medium (B) preferably contains 80 mass% or more of an organic solvent (B-1) having a boiling point of 180°C or more and 235°C or less in 100 mass% of the dispersion medium (B). By containing 80 mass% or more of the dispersion medium (B-1), the bonding paste does not dry immediately when applied to the objects to be bonded, and can be applied continuously to many objects to be bonded. In addition, it volatilizes quickly during heating and sintering, and is unlikely to remain in the coating film after drying, and is unlikely to cause voids during heating during bonding, contributing to the development of good bonding strength.

[0031] Specific examples of the dispersion medium (B-1) include terpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, dipropylene glycol monomethyl ether, dipropylene glycol methyl-n-propyl ether, 3-methoxy-3-methylbutyl acetate, ethylene glycol, hexanoic acid, propylene glycol diacetate, dipropylene glycol methyl ether acetate, 1,3-butylene glycol, isoparaffin-based solvents contained in hydrocarbon solvents, etc. Among them, terpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, and dipropylene glycol monomethyl ether are particularly preferably used. These dispersion media (B-1) can be used alone or in combination.

[0032] The bonding paste of the present invention preferably contains metal particles (A) / dispersion medium (B) in a ratio of 80 / 20 to 95 / 5 (mass ratio). By containing the above range, good application suitability as a bonding paste can be ensured, and the amount of organic components remaining in the dried coating film can be suppressed, and the generation of voids during heating during bonding can be suppressed, resulting in good bonding strength.

[0033] The bonding paste of the present invention preferably contains 97.6 to 99.885 mass% of metal particles (A) and dispersion medium (B) in total. That is, the bonding paste of the present invention may contain additives such as a sintering accelerator, but the total amount of these is 1 mass% or less in 100 mass% of the bonding paste. Even when additives are contained, by keeping the amount thereof to a very small amount, it is possible to suppress the generation of voids and form a dense bonding coating film.

[0034] The sintering accelerator is a compound having a functional group with high affinity to the metal particles (A), and due to this high affinity, it has the function of peeling off the organic matter covering the metal particles (A). The metal particles from which the organic matter has been peeled off lose their dispersion stability and undergo aggregation, which promotes contact and fusion between the particles, making it possible to form a dense metal film. The functional group with high affinity to the metal particles (A) is not particularly limited and examples include polar groups, but in particular those containing nitrogen atoms have high affinity with the metal particles (A) and are preferably used as sintering accelerators.

[0035] As the resin component, a resin-type dispersant or the like can be added for the purpose of preventing aggregation of the metal particles (A) in the bonding paste and further improving viscosity stability over time and applicability.

[0036] The bonding paste of the present invention contains a resin (C). It has been found that the inclusion of the resin (C) imparts flexibility to the bonded body, and prevents the bond strength from deteriorating even when the bonded body is subjected to temperature changes during initial / heat cycle tests. Specifically, the bonded body is prevented from deteriorating due to expansion and contraction of the bonded body according to the linear expansion coefficient, and the bonded body is prevented from weakening in the interface between the bonded body and the bonded body due to poor conformity to the bonded body caused by the difference in linear expansion coefficient between the bonded body and the bonded body.

[0037] The resin (C) is not particularly limited, but examples thereof include acrylic, epoxy, urethane, polyester, and polyamide resins, with thermosetting resins being particularly preferred.

[0038] The resin (C) is preferably contained in the bonding paste at 0.015 to 1.4 mass %. When the resin (C) is contained at 0.015 mass % or more, flexibility is imparted to the bonded body, and the bond strength after thermal cycling is particularly good. When the resin (C) is contained at 1.4 mass % or less, the generation of voids is suppressed, and a dense bonded body can be formed.

[0039] The bonding paste of the present invention preferably contains metal particles (A) / resin (C) in a ratio of 99 / 1 to 99.97 / 0.03 (mass ratio).

[0040] The viscosity of the bonding paste of the present invention is preferably 1 to 150 Pa·s at 25° C. If the viscosity is within the above range, the application performance becomes better.

[0041] The bonding paste of the present invention can be used to bond a first object to be bonded and a second object to be bonded to obtain a bonded body.

[0042] The method for applying the bonding paste to the object to be bonded is not particularly limited as long as it can be applied uniformly to the member, and examples thereof include various printing methods such as screen printing, flexographic printing, offset printing, gravure printing, metal mask printing, and gravure offset printing, and a dispenser.

[0043] The sintering conditions in the bonding step are appropriately changed, and may be, for example, atmospheric pressure, a nitrogen atmosphere, a vacuum, a pressurized or reducing atmosphere, and 200 to 300°C. Examples of the sintering device include a hot air oven, an infrared oven, a reflow oven, a microwave oven, a hot plate, and an optical sintering device. In the case of an optical sintering device, the type of light to be irradiated is not particularly limited, and examples thereof include a mercury lamp, a metal halide lamp, a chemical lamp, a xenon lamp, a carbon arc lamp, and a laser light. These devices may be used alone or in combination as appropriate.

[0044] Before the firing process, a preliminary drying process may be carried out as appropriate to remove organic components from the bonding coating film. For example, a heating process in the range of 60 to 220°C using a hot air oven, infrared oven, reflow oven, microwave oven, hot plate, etc., or a drying process under reduced pressure may be included.

[0045] In addition, when placing the second object to be joined on the first object to be joined coated with the bonding paste of the present invention, the second object to be joined can be placed under pressure. The pressure is appropriately set depending on the viscosity of the bonding paste and the drying state of the paste, and is preferably 0.1 to 5 MPa, more preferably 0.3 to 3 MPa.

[0046] A preferred method for joining two objects to be joined includes applying the joining paste of the present invention to a first object to be joined, drying it, placing a second object to be joined on the dried surface at a temperature between about room temperature and the temperature at which it was dried, applying a pressure of 0.3 to 3 MPa, and then heating the object to about 200 to 300°C at a heating rate of about 1°C / min to 15°C / min while the pressure is still applied or while further applying pressure, and sintering the object. After the temperature rise is completed, it is preferable to maintain the temperature at the end of the temperature rise or a temperature higher than the temperature at the end of the temperature rise for about 10 minutes to 2 hours.

[0047] The type of the object to be joined is not particularly limited, and examples thereof include metal members, electronic elements, plastic materials, ceramic materials, etc. It is preferable to join metal members together, a metal member and a semiconductor element, or a metal member and an LED element.

[0048] Examples of the metal member include a copper substrate, a gold substrate, an aluminum substrate, etc. Examples of the electronic element include a semiconductor element and an LED element. Semiconductor elements include silicon and germanium, as well as gallium arsenide, gallium phosphide, and cadmium sulfide. LED elements include aluminum, silicon nitride, diamond, graphite, yttrium oxide, and magnesium oxide. In particular, it is possible to use power device elements of silicon carbide, gallium nitride, etc. Examples of plastic materials include polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polyethylene naphthalate, etc. Examples of the ceramic material include glass and silicon. The first and second objects to be joined may be members of different kinds, not just the same kind. The members may be appropriately processed by corona treatment, plating, or the like to increase the joining strength.

[0049] Although the embodiment of the present invention has been described above, the present invention is not limited thereto, and various modifications can be made without departing from the gist of the present invention. EXAMPLES

[0050] The present invention will be described in detail below using examples and comparative examples, but the technical scope of the present invention is not limited thereto. In the examples, unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass", and the numerical values ​​in the tables mean "parts" unless otherwise specified. In addition, "bp" means boiling point.

[0051] (Production example 1) Metal particles A1 Under a nitrogen atmosphere, 200 parts of toluene and 22.3 parts of silver hexanoate were mixed while stirring at 25°C to obtain a 0.5M solution, and then 2.3 parts of diethylaminoethanol (0.2 mol amount per 1 mol of silver) and 0.28 parts of oleic acid (0.01 mol amount per 1 mol of silver) were added as a dispersant and dissolved. Then, 73.1 parts of a 20% concentration aqueous solution of succinic acid dihydrazide (hereinafter, SUDH) (2 mol amount of hydrazide group per 1 mol of silver) were dropped as a reducing agent, and the liquid color changed from light yellow to dark brown. In order to further promote the reaction, the temperature was raised to 40°C, and the reaction was allowed to proceed. After leaving it to stand and separating, the aqueous phase was taken out to remove excess reducing agent and impurities, and distilled water was added to the toluene layer several times, washing and separation were repeated, and then the process of adding toluene, centrifuging, and removing the supernatant was repeated twice. The precipitate was dried to obtain metal particles A1 in which silver particles were coated with hexanoic acid and oleic acid. The particle size of the metal particles A1 was measured by the method described later, and found to be d1 of 45 nm, d50 of 150 nm, and d99 of 450 nm. The Ts, Te, and mass loss rate of the metal particles A1 were measured by the method described later, and found to be Ts of 170° C., Te of 270° C., and mass loss rate of 2.7%.

[0052] (Production example 2) Metal particles A2 Metal particles A2 were obtained in the same manner as in Production Example 1, except that the amount of oleic acid was 0.23 parts (0.008 mol per 1 mol of metal).

[0053] (Production example 3) Metal particles A3 10 parts of silver nitrate were dissolved in 500 parts of ethylene glycol. Then, 5 parts of polyvinylpyrrolidone were dispersed in ethylene glycol. Then, ethylene glycol was heated to 150°C (reaction temperature), and the reaction was carried out for 1 hour while stirring at a rotation speed of 400 rpm while maintaining the reaction temperature at 150°C. At this time, the silver nitrate and ethylene glycol reacted with each other to generate nitrogen oxide gas, and the silver nitrate was reduced to obtain a dispersion of metal particles A3 coated with polyvinylpyrrolidone. The dispersion of metal particles A3 was centrifuged, the supernatant was removed, ethylene glycol was added to the precipitate, and the mixture was stirred, and then centrifuged again to remove the supernatant. The precipitate was dried to obtain metal particles A3 in which silver particles were coated with polyvinylpyrrolidone.

[0054] (Production example 4) Metal particles A4 50 parts of 3-methoxypropylamine, 5 parts of dodecylamine, and 60 parts of diglycolamine were thoroughly stirred while 45 parts of silver oxalate was added to thicken the mixture. The obtained thickening substance was placed in a thermostatic chamber and reacted, and then 100 parts of replic acid was added and further reacted to obtain a suspension. Methanol was added and stirred, and then the silver particles were precipitated and separated by centrifugation, and the supernatant was removed. This operation was repeated once more to obtain metal particles A4 in which the silver particles were coated with replic acid.

[0055] (Production example 5) Metal particles A5 Metal particles A5 in which silver particles are coated with propionic acid and oleic acid were obtained in the same manner as in Production Example 1, except that 18.1 parts of silver propionate was used instead of 22.3 parts of silver hexanoate.

[0056] (Production example 6) Metal particles A6 Metal particles A6 in which silver particles are coated with pentanoic acid and oleic acid were obtained in the same manner as in Production Example 1, except that 20.9 parts of silver pentanoate was used instead of 22.3 parts of silver hexanoate.

[0057] (Production example 7) Metal particles A7 Metal particles A7 in which silver particles are coated with myristic acid and oleic acid were obtained in the same manner as in Production Example 1, except that 33.5 parts of silver myristate were used instead of 22.3 parts of silver hexanoate.

[0058] (Production example 8) Metal particles A8 Metal particles A8 in which silver particles are coated with stearic acid and oleic acid were obtained in the same manner as in Production Example 1, except that 39.1 parts of silver stearate was used instead of 22.3 parts of silver hexanoate.

[0059] (Metal particle A9) Silver particles coated with polyvinylpyrrolidone, NCXAGPD200 manufactured by NanoComposix, Inc., were used as is. The particle size, decomposition onset temperature, and the like were determined in the same manner as in Production Example 1.

[0060] (Production example 9) Metal particles A10 Metal particles A10 were obtained in the same manner as in Production Example 1, except that the amount of hexanoic acid was 15.6 parts and the amount of oleic acid was 0.23 parts (0.008 mol amount per 1 mol of metal).

[0061] (Production example 10) Metal particles A11 Metal particles A11 were obtained in the same manner as in Production Example 1, except that the amount of hexanoic acid was 11.2 parts and the amount of oleic acid was 0.23 parts (0.008 mol times the amount per mol of metal). (Production example 11) Metal particles A12 Metal particles A12 were obtained in the same manner as in Production Example 1, except that the amount of hexanoic acid was 19.2 parts and the amount of oleic acid was 0.23 parts (0.008 mol amount per 1 mol of metal).

[0062] (Production example 101) Metal particles A101 Metal particles A101 in which silver particles are coated with hexanoic acid and oleic acid were obtained in the same manner as in Production Example 1, except that the amount of silver hexanoate was changed from 22.3 parts to 23 parts.

[0063] (Production example 102) Metal particles A102 3400 parts of water was placed in the reaction tank, and a nitrogen atmosphere was created, after which the temperature was adjusted to 60°C. 7 parts of ammonia water containing 28% by mass as ammonia was added to the reaction tank, and then stirred for 1 minute. Next, 45 parts of hexanoic acid was added, and stirred for 4 minutes. Then, 24 parts of 50% by mass hydrazine hydrate aqueous solution were added (reducing agent solution). In another container, a silver nitrate aqueous solution was prepared by dissolving 34 parts of silver nitrate crystals in 180 parts of water (silver salt aqueous solution). 0.00008 parts of copper nitrate trihydrate was further added to this silver salt aqueous solution, and the temperature was adjusted to 60°C. Then, the silver salt aqueous solution was added to the reducing agent solution all at once to mix, and the reduction reaction was started. The color of the slurry changed and subsided about 10 seconds after the start of the reduction reaction. After aging for 10 minutes while stirring, the mixture was subjected to solid-liquid separation by suction filtration, washing with pure water, and drying at 40°C for 12 hours, and metal particles A102 in which silver particles were coated with hexanoic acid were obtained.

[0064] (Production example 103) Metal particles A103 135 parts of silver nitrate was dissolved in 720 parts of pure water (raw material solution). 14,000 parts of pure water was charged in a separate container, and the temperature was raised to 40° C. while nitrogen was passed through it for 30 minutes to remove dissolved oxygen. Then, 180 parts of sorbic acid was added, and then 28 parts of 28% ammonia water was added as a stabilizer. The ammonia-added solution was continued to be stirred, and 5 minutes after the start of the preparation of silver particles, 60 parts of hydrous hydrazine (80% purity) was added as a reducing agent to prepare a reduced solution. 10 minutes after the start of the preparation, the raw material solution whose liquid temperature had been adjusted to 40° C. was added all at once to the reduced solution to react, and the stirring was stopped and the mixture was aged for 30 minutes to form a silver particle aggregate coated with sorbic acid. Then, the mixture was filtered and washed with pure water to obtain a silver particle aggregate. The silver particle aggregate was dried in a vacuum dryer under conditions of 80° C. for 12 hours to obtain metal particles A103 in which silver particles are coated with sorbic acid.

[0065] (Production example 104) Metal particles A104 15 parts of hexylamine were added to 200 parts of toluene and stirred. 10 parts of silver nitrate were added while stirring, and when the silver nitrate was dissolved, 5 parts of oleic acid and 10 parts of hexanoic acid were added in sequence to prepare a toluene solution of silver nitrate. 0.02 g / mL sodium borohydride aqueous solution prepared by adding 1 part of sodium borohydride to 50 parts of ion-exchanged water was dropped into this toluene solution of silver nitrate, and stirring was continued for one hour to generate silver particles. Then, 250 parts of methanol was added to precipitate the silver particles, and the silver particles were completely precipitated by centrifugation, and the reaction residue and solvent contained in the supernatant were removed. The sediment containing silver particles (untreated silver particle composition) remaining after removing the supernatant was heated under reduced pressure at 60° C. for 45 minutes using an evaporator to appropriately reduce the amount of organic matter containing hexylamine, oleic acid, and hexanoic acid in the silver particle composition, and finally dried to obtain metal particles A104 in which the silver particles are coated with hexylamine, oleic acid, and hexanoic acid.

[0066] (Production example 105) Metal particles A105 3400 parts of water was placed in the reaction tank, and a nitrogen atmosphere was created, after which the temperature was adjusted to 60°C. 7 parts of ammonia water containing 28% by mass as ammonia was then added to the reaction tank, and stirred for 1 minute. Next, 45 parts of sorbic acid were added, and the mixture was stirred for 4 minutes. Then, 24 parts of a 50% by mass aqueous solution of hydrazine hydrate were added (reducing agent solution). In a separate container, an aqueous solution of silver nitrate was prepared by dissolving 34 parts of silver nitrate crystals in 180 parts of water (aqueous silver salt solution). Then, the aqueous silver salt solution was added all at once to the reducing agent solution, and the reduction reaction was started. The color of the slurry changed and subsided about 10 seconds after the start of the reduction reaction. After aging for 10 minutes while stirring, the mixture was subjected to solid-liquid separation by suction filtration, washing with pure water, and drying at 40°C for 12 hours, and metal particles A105 in which silver particles were coated with sorbic acid were obtained.

[0067] (Production example 106) Metal particles A106 3 parts of ricinoleic acid, 260 parts of N,N-dimethyl-1,3-diaminopropane, and 480 parts of butanol were added and stirred for about 1 minute, and then 320 parts of silver oxalate were added and stirred for about 10 minutes to obtain a composition for preparing silver particles. Then, the mixture was stirred at 40°C for 30 minutes, and further stirred at 90°C for 30 minutes. After cooling, 1500 parts of methanol was added and stirred, and then a centrifuge was used to perform a centrifuge operation and remove the supernatant. The steps of adding 1500 parts of methanol, stirring, centrifugation, and removing the supernatant were repeated twice, and then dried to obtain metal particles A106 in which silver particles are coated with ricinoleic acid.

[0068] (Production example 107) Metal particles A107 6 parts of oleic acid, 140 parts of n-octylamine, 43 parts of N,N-dimethyl-1,3-diaminopropane, 16 parts of n-dodecylamine, 12 parts of cyclohexylamine, and 64 parts of n-butylamine were added and stirred for about 1 minute, and then 320 parts of silver oxalate were added and stirred for about 10 minutes to obtain a composition for preparing silver particles. Then, the mixture was stirred at 40°C for 30 minutes, and further stirred at 90°C for 30 minutes. After cooling, 1500 parts of methanol was added and stirred, and then a centrifugation operation was performed for 1 minute in a centrifuge to remove the supernatant. The steps of adding 1500 parts of methanol, stirring, centrifugation, and removing the supernatant were repeated twice, and then dried to obtain metal particles A107 in which silver particles are coated with oxalic acid.

[0069] (Production example 201) Metal particles A201 20 parts of 3-methoxypropylamine was thoroughly stirred while adding 30 parts of silver oxalate to thicken the mixture. The obtained thickening substance was placed in a thermostatic chamber and reacted, and then 100 parts of replic acid was added and further reacted to obtain a suspension. Methanol was added and stirred, and the silver particles were precipitated and separated by centrifugation, and the supernatant was removed. This operation was repeated once more, and then dried to obtain metal particles A201 in which the silver particles were coated with replic acid. The particle size and decomposition start temperature were determined in the same manner as in Production Example 1, and the results were d1 was 15 nm, d50 was 45 nm, d99 was 95 nm, Ts was 150°C, Te was 230°C, and the mass reduction rate between Ts and Te was 4.9%.

[0070] (Production example 301) Metal particles A301 Metal particles A301 were obtained by mixing 58.5 parts of metal particles A5 obtained in Production Example 5 and 31.5 parts of metal particles A201.

[0071] (Production example 302) Metal particles A302 Metal particles A302 were obtained by mixing 72 parts of the metal particles A5 obtained in Production Example 5 and 18 parts of the metal particles A201.

[0072] (Production example 303) Metal particles A303 Metal particles A303 was obtained by mixing 81 parts of metal particles A105 obtained in Production Example 105 with 9 parts of silver particles "D2-1-C" manufactured by DOWA Electronics Co., Ltd., having a minimum particle diameter of 0.1 μm, an average particle diameter of 0.6 μm, and a maximum particle diameter of 1.2 μm. The particle diameter, decomposition start temperature, and the like were determined in the same manner as in Production Example 1. In addition, when the particle diameter and decomposition start temperature of the silver particles "D2-1-C" alone were determined in the same manner as in Production Example 1, the particle diameter could be determined, but as for the decomposition start temperature, etc., no clear mass reduction was observed even when the temperature was raised to 300° C., and the mass reduction rate at 300° C. was less than 0.2% based on the mass at 23° C.

[0073] (Production example 304) Metal particles A304 Metal particles A304 were obtained in the same manner as in Production Example 303, except that the amount of metal particles A105 was 45 parts and the amount of "D2-1-C" was 45 parts.

[0074] (Production example 305) Metal particles A305 67.5 parts of silver particles "LM1" manufactured by Tokusen Kogyo Co., Ltd., with a minimum particle size of 0.1 μm, an average particle size of 1.0 μm, and a maximum particle size of 3.2 μm, and 22.5 parts of silver particles "AgC239" manufactured by Fukuda Metal Foil Co., Ltd., with a minimum particle size of 2.1 μm, an average particle size of 6.0 μm, and a maximum particle size of 10.1 μm, were mixed to obtain metal particles A305. The particle size and decomposition start temperature were determined in the same manner as in Production Example 1. In addition, when the particle size and decomposition start temperature of each of the silver particles "LM1" and "AgC239" were determined in the same manner as in Production Example 1, the particle size could be determined, but the decomposition start temperature was not clearly observed even though the temperature was raised to 300 ° C., and the mass loss rate at 300 ° C. was less than 0.2% based on the mass at 23 ° C.

[0075] (Production example 306) Metal particles A306 Metal particles A306 were obtained by mixing 9 parts of the metal particles A106 obtained in Production Example 106 and 81 parts of the metal particles A107 obtained in Production Example 107.

[0076] (Production example 307) Metal particles A307 Metal particles A307 were obtained by mixing 45 parts of metal particles A5 obtained in Production Example 5 and 45 parts of metal particles A201.

[0077] The d1, d50, d99, Ts, Te, and mass reduction rate were determined for the metal particles coated with the organic component produced above, D2-1-C, LM1, and AgC239 by the methods described below. Among these, metal particles A1 to A9 are metal particles (A), and metal particles A101 to 107, 201, D2-1-C, LM1, and AgC239 are particles that are not metal particles (A) (sometimes abbreviated as "metal particles (A')" in this specification).

[0078] (Example 401) In a four-neck flask equipped with a cooling tube, a stirrer, a thermometer, and a nitrogen inlet tube, 18 parts of methyl methacrylate, 78 parts of n-butyl methacrylate, 2 parts of 2-hydroxyethyl methacrylate, 2 parts of glycidyl methacrylate, and 100 parts of toluene were charged, and the mixture was heated to 100°C while stirring under a nitrogen atmosphere, and 0.40 parts of azobisisobutyronitrile were added to carry out a polymerization reaction for 2 hours, and then 0.05 parts of azobisisobutyronitrile were added to carry out a polymerization reaction for another 2 hours, and 0.05 parts of azobisisobutyronitrile were added to carry out a polymerization reaction for another 2 hours. After that, 0.03 parts of hydroquinone, 0.8 parts of dimethylbenzylamine, and 1 part of acrylic acid (the amount required for the modification of the glycidyl methacrylate: 2 parts) were added, and the mixture was heated and stirred at 100°C for 15 hours. It was confirmed that the acid value was 2 mgKOH / g or less, and a resin c3-1 solution having a number average molecular weight of 16,000, a hydroxyl value of 16.9 mgKOH / g, and a solids content of 50% was obtained.

[0079] <Resin C1> jER828 (epoxy resin, manufactured by Mitsubishi Chemical Corporation) and jER YH306 (acid anhydride, manufactured by Mitsubishi Chemical Corporation) were mixed in a mass ratio of 1:1.2 to obtain resin C1. <Resin C2> EP001K base resin (epoxy resin, manufactured by Cemedine) and EP001K curing agent (special silicone modified resin, manufactured by Cemedine) were mixed in a mass ratio of 1:1 to obtain resin C2. <Resin C3> Resin c3-1 and VESTANAT T1890 (isocyanate, manufactured by Evonik) were mixed in a mass ratio of 1:0.1 to obtain Resin C3. <Resin C4> jER828 (epoxy resin, manufactured by Mitsubishi Chemical Corporation) was used as is. <Resin C5> Resin c3-1 was used as is.

[0080] [Particle size measurement] Isopropyl alcohol was added to each metal particle (A) and dispersed using an ultrasonic disperser to obtain a 0.5% by mass dispersion. The particle diameters of the metal particles (A) in the dispersion were measured using Nanotrac UPA-EX150 (manufactured by Nikkiso Co., Ltd.) to determine d1, d50, and d99.

[0081] [Ts, Te, mass reduction rate] For each metal particle (A), a differential thermal-thermogravimetric simultaneous measurement device (TG-DTA, EXSTAR TG / DTA6200, manufactured by Seiko Instruments Inc.) was used to raise the temperature from 25°C at a heating rate of 5°C / min, and the mass reduction rate of the metal particle (A) at Ts, Te, and Te, where the mass of the metal particle (A) at Ts was taken as 100 mass%, was determined. As shown in Figure 1, the extrapolated start temperature of the exothermic peak on the lowest temperature side shown in the DTA curve was taken as Ts, and the extrapolated end temperature of the exothermic peak on the highest temperature side shown in the DTA curve was taken as Te. Mass reduction rate = [(mass of metal particle (A) at Ts - mass of metal particle (A) at Te) / mass of metal particle (A) at Ts] x 100

[0082] [Example 1] 90 parts by mass of metal particles A1, 9.87 parts by mass of terpineol, and 0.13 parts by mass of resin C1 were mixed using a planetary stirrer to prepare a bonding paste, which was evaluated by the method described below.

[0083] [Examples 2 to 42], [Comparative Examples 1 to 14] A bonding paste was obtained in the same manner as in Example 1, except that the types and amounts of materials were changed according to the compositions in Tables 1 to 5, and then evaluated. Note that dihydroterpineol is a mixture of 1-hydroxy-p-menthane and 8-hydroxy-p-menthane, and therefore has a boiling point in the range of 200 to 220°C. The abbreviations in the tables are as follows. (D1) Curing accelerator: Dicyandiamide, jER Cure DICY7 manufactured by Mitsubishi Chemical Corporation (D2) Resin-type dispersant: Acrylic copolymer resin-type dispersant, BYK DISPER-BYK-2020

[0084] [Initial viscosity measurement] The viscosity of the bonding paste was measured at 25°C immediately after preparation using an E-type viscometer with a rotor of 3° and R=7.7mm at a rotation speed of 5min-1.

[0085] [Viscosity stability over time] After storing each bonding paste in an environment of 23°C for 30 days, the viscosity was measured in the same manner as the initial viscosity measurement. The rate of change in viscosity after 30 days of storage relative to the initial viscosity was determined and evaluated according to the following criteria. For example, if the initial viscosity is 100 Pa s and the viscosity after 30 days of storage is 200 Pa s, the rate of viscosity change is +100%. Good: Viscosity change rate is greater than -20% and less than +20% (very good) △: Viscosity change rate is greater than -50% and less than -20%, or greater than +20% and less than +50% (good). ×: Viscosity change rate is -50% or less or +50% or more (defective)

[0086] [Coating suitability] Each bonding paste was applied to the substrate 1 under the following conditions, and the suitability of the first application and the 100th application was judged according to the following criteria. Note that a new substrate 1 that had not been applied was used for each application. <Base material 1> Gold-plated copper substrate: 20 x 20 x 3 mm <Coating conditions> Metal mask: 4mm square opening, 50μm thickness (manufactured by Celia Corporation) Metal squeegee: 40mm x 250mm, thickness 1mm (manufactured by Celia Corporation) <Evaluation criteria> ○: The bonding paste is evenly applied to the entire opening (4 mm square). (Very good) △: The bonding paste is applied to a part of the opening (within a 2-3 mm square area) (good). ×: The bonding paste was applied only to an area of ​​less than 2 mm square in the opening, and the applied area was cracked (poor).

[0087] [Preparation of junction] Each bonding paste was applied once to the base material 1 under the same conditions as the above-mentioned application suitability, and then dried at 75°C for 5 minutes. The base material 2 (chip) described below was placed on the dried surface, and pressure was applied from above the base material 2 under the below-mentioned mounting conditions to temporarily bond the bonded body. Next, the temporarily bonded bonded body (temporary bonded body) was heated under the below-mentioned sintering conditions to obtain a bonded body. <Base material 2> Gold-plated SiC chip: 5×5×0.3mm <Implementation conditions> 25℃, 0.5MPa, pressurized for 10 seconds <Sintering conditions> The temporarily bonded body was placed in a hot air oven, and the temperature was increased from 25° C. to 250° C. at a rate of 2.5° C. / min., and when it reached 250° C., it was maintained at that temperature for 1 hour.

[0088] [Bonding strength (initial, after thermal cycle test) The bond strength (die shear strength) of the resulting bonded body was measured using the following measuring device and test conditions. Measurement equipment: Universal bond tester (Daisi Japan Co., Ltd., 4000 series) <Test conditions> Measurement height: 100μm Measurement speed: 500μm / s Specifically, the substrate 1 was fixed, and the interface between the substrate 1 and the bonding paste was pushed toward the substrate 2 at a height of 100 μm at a speed of 500 μm / s, and the bonding strength at which the bond was broken was determined. The bonding strength immediately after the bond was produced (initial strength) and the bonding strength after the following cycle test were measured and evaluated based on the following evaluation criteria. The higher the adhesive strength value, the better, and a value of 15 MPa or more is within the practical range.

[0089] <Cold-heat cycle test> The bonded body was kept at -40°C for 30 minutes, then kept at 25°C for 15 minutes, and then kept at 200°C for 30 minutes, and this cycle was repeated 300 times.

[0090] ◎:30MPa or more ○: 25MPa or more and less than 30MPa ○△: 22MPa or more and less than 30MPa △+: 18MPa or more and less than 22MPa △: 15MPa or more and less than 18MPa ×: Less than 15MPa

[0091] [Table 1]

[0092] [Table 1]

[0093] [Table 2]

[0094] [Table 3]

[0095] [Table 4]

[0096] [Table 5]

[0097] As shown in Tables 1 to 3, the bonding pastes of the present invention in Examples 1 to 42 have excellent storage (viscosity) stability and application suitability over time, and by using this bonding paste, it is possible to obtain bonded bodies with high bonding strength both initially and after environmental (cold-heat cycle) tests.

[0098] On the other hand, as shown in Tables 4 and 5, the bonding pastes of Comparative Examples 1 to 5 and 10 to 14, which used metal particles with d1, d50, or d99 that were not within the optimal range, and Comparative Examples 6 to 9, which did not contain an appropriate amount of resin (C), had insufficient storage (viscosity) stability and application suitability over time, and the bonding strength of the bonds obtained using these bonding pastes was poor both initially and after environmental (cold-heat cycle) tests. [Explanation of symbols]

[0099] Ts: Extrapolated onset temperature of exothermic peak Te: Extrapolated end temperature of exothermic peak Ms: mass at Ts Mass in Me:Te

Claims

1. The present invention comprises metal particles (A) coated with an organic component (a), a dispersion medium (B), and a resin (C), and contains 0.02 to 1.2 mass % of the resin (C), the metal particles (A) have a particle diameter (d1) corresponding to 1% of an integrated particle diameter distribution of 30 to 200 nm, a particle diameter (d50) corresponding to 50% of the integrated particle diameter distribution of 100 to 350 nm, and a particle diameter (d99) corresponding to 99% of the integrated particle diameter distribution of 300 to 900 nm, an extrapolated end temperature (Te) of an exothermic peak on the highest temperature side of the metal particles (A) as determined by differential thermal analysis is 200 to 300° C., and when the mass of the metal particles (A) at an extrapolated start temperature (Ts) of an exothermic peak on the lowest temperature side of the metal particles (A) as determined by differential thermal analysis is taken as 100 mass %, the Te The mass reduction rate of the metal particles (A) in the bonding paste is 0.2 to 5 mass %, the metal particles (A) are silver particles, and the resin (C) is a bonding paste made of a mixture of an epoxy resin and an acid anhydride, a mixture of an epoxy resin and a special silicone-modified resin, or a mixture of an acrylic resin and an isocyanate.

2. The bonding paste according to claim 1, wherein the ratio of metal particles (A) to resin (C) is 99 / 1 to 99.97 / 0.03 (mass ratio).

3. 3. The bonding paste according to claim 1, wherein the ratio of the metal particles (A) to the dispersion medium (B) is 80 / 20 to 95 / 5 (mass ratio).

4. The bonding paste according to any one of claims 1 to 3, wherein the dispersion medium (B) contains one or more selected from the group consisting of terpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, and dipropylene glycol monomethyl ether.

5. The bonding paste according to any one of claims 1 to 4, having a viscosity of 1 to 150 Pa·s.

6. A bonded body in which a first body to be bonded and a second body to be bonded are bonded with the bonding paste according to any one of claims 1 to 5.

7. A method for producing a bonded body, comprising applying the bonding paste according to any one of claims 1 to 5 to a first body to be bonded, and placing a second body to be bonded on the applied surface.

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