JP2021098875A - Joining paste, junction body using the same, and method of making junction body - Google Patents

Abstract

To provide a joining paste low in viscosity and excellent in application suitability while containing a metal particle at a high ratio, which is a junction-body forming paste excellent in the junction strength initial and after a hot-cold cycle test.SOLUTION: A joining paste contains a metal particle (A) coated by an organic component (a) and a dispersion medium (B) in a ratio of metal particle (A)/dispersion medium (B)=80/20-95/5 (mass ratio), and the metal particle (A) and the dispersion medium (B) 99-100 mass% in total. The metal particle (A) has a d1 of 30-200 nm, a d50 of 100-350 nm and a d99 of 300-900 nm, and an extrapolation finishing temperature Te of a highest temperature-sided exothermic peak of the metal particle (A) determined by differential thermal analysis of 200°C or higher and 300°C or lower.SELECTED DRAWING: Figure 1

Description

The present invention relates to a bonding paste and a bonded body using the same.

Conventionally, solder has been used as a joining material for joining metal members to each other, a metal member to a semiconductor element, or a metal member to an LED element or the like. In the field of next-generation power electronics, as a bonding material for devices such as SiC capable of operating at high temperature, a substitute material for solder is required from the viewpoint of high temperature drive reliability. As described above, the use of a bonding paste using metal particles has been proposed.

JP-A-2018-172728 Japanese Unexamined Patent Publication No. 2017-137375 WO2011 / 007402 Japanese Unexamined Patent Publication No. 2011-801471 WO2011 / 155615 WO2012 / 169076 WO2013 / 061527 WO2015 / 060173 WO2017 / 169534 W02019 / 026799

What is required of a bonding paste using metal particles is (1) sufficient bonding strength can be obtained after sintering, (2) bonding strength is maintained after environmental tests such as a thermal cycle, and (3). ) Optimal flow characteristics for printing / applying bonding paste, all of which are required to be satisfied.

A bonding paste using so-called metal nanoparticles with an average particle size of less than 100 nm has been proposed, but the coating material contained in the nanoparticles remains in the coating film, resulting in a decrease in bonding strength and bonding strength after an environmental test. Is seen to decrease. In addition, the viscosity is high and the application suitability is poor.
In order to solve the above problem, a bonding paste in which metal nanoparticles having an average particle size of less than 100 nm and metal microparticles having an average particle size of 1 μm or more are used in combination has been proposed, but sufficient dispersibility of the metal particles can be ensured. However, the suitability for application and the smoothness / leveling property of the bonding film after application cannot be ensured.

On the other hand, although it has been proposed to use metal particles in combination with a sintering accelerator or a resin component, there is a decrease in bonding strength and a decrease in bonding strength after environmental tests such as heat resistance.
Further, although the viscosity of the bonding paste can be reduced by increasing the amount of the liquid dispersion medium, the liquid dispersion medium in the bonding paste is volatilized by heating at the time of bonding and disappears when the bonding is completed. Nevertheless, the bonding strength is reduced.

The present invention provides a bonding paste that contains a high proportion of metal particles but has a low viscosity and is excellent in coating suitability, and can form a bonding body having excellent bonding strength after the initial and thermal cycle tests. The purpose is.

As a result of diligent studies, the present inventors have conducted diligent studies on the particle size of the metal particles in the bonding paste, the decomposition temperature and coating amount of the metal particle coating material, and the drying of the solvent in the bonding paste. By controlling the properties, we found a bonding paste with excellent coating suitability and bonding strength.

That is, in the present invention, the metal particles (A) coated with the organic component (a) and the dispersion medium (B) are mixed with the metal particles (A) / dispersion medium (B) = 80/20 to 95/5 (mass ratio). ), And a total of 99 to 100% by mass of the metal particles (A) and the dispersion medium (B).
The metal particles (A) have a 1% integrated particle size distribution particle size (d1) of 30 to 200 nm, a 50% integrated particle size distribution particle size (d50) of 100 to 350 nm, and a 99% integrated particle size distribution particle size (d99). Is 300-900 nm
The extrapolation end temperature Te of the exothermic peak on the hottest side of the metal particles (A) determined by differential thermal analysis is 200 ° C or higher and 300 ° C or lower.
When the mass of the metal particles (A) at the external start temperature Ts of the exothermic peak on the lowest temperature side of the metal particles (A) obtained by differential thermal analysis is 100%.
The mass reduction rate of the metal particles (A) at the extrapolation end temperature Te is 1 to 5% by mass.
The present invention relates to a bonding paste in which the dispersion medium (B) contains an organic solvent (B-1) having a boiling point of 180 ° C. or higher and lower than 230 ° C. in an amount of 80% by mass or more of the entire dispersion medium.

Preferably, the dispersion medium (B-1) is one or more of turpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, and dipropylene glycol monomethyl ether. is there.

The viscosity of the bonding paste is preferably 1 to 150 Pa · s.

The present invention also relates to a bonded body in which a first bonded body and a second bonded body are bonded by the bonding paste.

Further, in the present invention, the above-mentioned bonding paste is applied to the first bonded body, dried, and then the second bonded body is placed on the dried surface, and a pressure of 0.3 to 3 MPa is applied. The present invention relates to a method for producing a bonded body, which comprises applying the pressure and then raising the temperature to 200 to 300 ° C. in a state where the pressure is still applied or in a state where the pressure is further applied.

In the method for manufacturing a bonded body, after the temperature rise is completed, the temperature at the end of the temperature rise or higher than the temperature at the end of the temperature rise can be maintained for 10 minutes to 2 hours while applying the pressure at the end of the temperature rise. preferable.

INDUSTRIAL APPLICABILITY The present invention provides a bonding paste that contains a high proportion of metal particles but has a low viscosity and is excellent in coating suitability, and can form a bonding body having excellent bonding strength after the initial and thermal cycle tests. I was able to do it.

The schematic diagram of the result of having measured the metal particle in this invention using the differential thermal-thermogravimetric simultaneous measuring apparatus (TG-DTA).

As described above, the bonding paste of the present invention is a composition containing metal particles (A) coated with an organic component and a dispersion medium (B).

(Metal particles (A))
Examples thereof include metal powders such as gold, silver, copper, nickel, chromium, palladium, rhodium, ruthenium, indium, silicon, aluminum, tungsten, molybdenum, and platinum, alloys thereof, and composite powders thereof. Further, a nucleolus and fine particles coated with a substance different from the nucleolus substance, specifically, for example, silver-coated copper powder having copper as a nucleolus and its surface coated with silver can be mentioned. Also, for example, 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), and Examples thereof include powders whose surfaces are coated with these metal oxides.
The type of metal used may be one type, or two or more types may be used in combination.

In the present invention, the metal particles (A) in which the 1% integrated particle size distribution particle size (d1), the 50% integrated particle size distribution particle size (d50), and the 99% integrated particle size distribution particle size (d99) are controlled are used. This is very important. The 1% integrated particle size distribution particle size (d1), 50% integrated particle size distribution particle size (d50), and 99% integrated particle size distribution particle size (d99) of the metal particles (A) are organic solvents (IPA:: The metal particles (A) were dispersed in (isopropyl alcohol) with an ultrasonic disperser so as to be 0.5% by mass, and the obtained dispersion was obtained. For the measurement, for example, Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.) can be used.
The 1% integrated particle size distribution particle size (d1), 50% integrated particle size distribution particle size (d50), and 99% integrated particle size distribution particle size (d99) referred to in the present specification are the integrated particle size distributions, respectively. It means the particle size (volume basis) corresponding to 1%, 50%, and 99% of.

The 1% integrated 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% integrated 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% integrated particle size distribution particle size (d99) is 300 to 900 nm, preferably 300 to 750 nm, and more preferably 300 to 600 nm.

Smaller metal particles are coated with a relative amount of coating material, i.e., organic components, than larger metal particles. Therefore, by using metal particles that are large to some extent, the residual organic components derived from the coating material in the bonding material (hereinafter, also referred to as the bonding coating film) are suppressed, and the generation of voids in the bonding coating film is suppressed. , The joint strength can be increased.
On the other hand, larger metal particles have a relatively higher melting point than smaller metal particles. Therefore, by using metal particles that are small to some extent, the metal particles can be sufficiently melted and integrated (hereinafter, also referred to as sintering) without being extremely heated, and a dense bonded coating film can be formed. It is possible to suppress a decrease in joint strength.
That is, it is important that the metal particles are not too small from the viewpoint of suppressing the generation of voids in the bonded coating film, and that the metal particles are not too large from the viewpoint of easiness of sintering.
Further, the size of the 1% integrated particle size distribution particle diameter (d1) is important for suppressing the generation of voids, and the size of the 99% integrated particle size distribution particle diameter (d99) is important for the ease of sintering. .. If the size (particle size) of the metal particles is uniform, the gaps between the metal particles in the coating film being formed in the bonding process cannot be sufficiently filled, and voids in the bonding coating film are formed. It causes the occurrence. By giving a distribution to the size (particle size) of the metal particles, it is possible to effectively fill the gaps between the metal particles, and it is possible to suppress the generation of voids in the bonded coating film. For the above reasons, the above-mentioned ranges of 1% integrated particle size distribution particle size (d1), 50% integrated particle size distribution particle size (d50), and 99% integrated particle size distribution particle size (d99) are required.

As the metal particles (A), those having a specific particle size range may be used alone, or a plurality of metal particles (A) having different particle size ranges may be used in combination, and 1% integration of the metal particles alone or in combination may be used. The particle size of the particle size distribution particle size (d1), the 50% integrated particle size distribution particle size (d50), and the 99% integrated particle size distribution particle size (d99) may be within the above ranges.

Further, the surface of the metal particles (A) is coated with the organic component (a) as described above, and in the bonding paste, the decomposition temperature due to heating of the organic component (a) and the covering organic component (a) are used. ) Is important.

The decomposition temperature (decomposition start temperature, decomposition end temperature) of the coating material of the metal particles (A) and the amount of the coating material are determined by a thermogravimetric-differential thermal analysis (hereinafter, also referred to as TG / DTA analysis) apparatus (for example, EXSTAR TG /). Calculated based on the measurement data when heated with a DTA6200 (manufactured by Seiko Instruments) at a heating rate of 5 ° C./min.
FIG. 1 schematically shows a DTA curve and a TG curve at the time of temperature rise. _{As shown in FIG. 1, the start temperature T s} of the exothermic peak on the lowest temperature side shown by the DTA curve means the supplementary start temperature, and is a straight line extending the baseline on the low temperature side to the high temperature side in the heating measurement. ， The temperature at the intersection with the tangent line drawn at the point where the gradient is maximum on the curve on the low temperature side of the exothermic peak on the coldest side. Similarly, the end temperature T _e of the highest temperature side of the exothermic peak indicated by DTA curve a meaning extrapolated end temperature, and the straight line obtained by extending the baseline on the high temperature side to low temperature side in the heat measurement, highest temperature side It is the temperature at the intersection with the tangent line drawn at the point where the slope is maximum on the curve of the peak.
Then, it is considered that the decomposition of the coating material _{starts from the extrapolation start temperature T s} of the exothermic peak on the lowest temperature side, the mass of the metal particles begins to decrease, and _{the decomposition of the coating material ends at the extrapolation end temperature T e.} because, say T _s the decomposition start temperature, and T _e the decomposition end temperature.
That is, the following mass reduction rate is understood as the amount of coating material.
Mass reduction rate = [(mass at decomposition start temperature-mass at decomposition end temperature) / mass at decomposition start temperature] x 100
A slight decrease in mass of metal particles may be observed even in a region lower than the decomposition start temperature T _s and in a region higher than the decomposition end temperature T _e , but if a clear exothermic peak is not observed, decomposition occurs. It is understood that it is not caused.

Decomposition end temperature T _e of the coating material in the metal particles (A), 200 ° C. or higher, it is important that at 300 ° C. or less, preferably 200 ° C. or more and 280 ° C. or less.
It is important that the amount of the coating material in the metal particles (A) is 1 to 5% by mass, preferably 2 to 4%.

By decomposition end temperature T _e of the coating material is 200 ° C. or higher, the viscosity of the bonding paste can be maintained and stable when stored. By decomposition end temperature T _e of the coating material is 300 ° C. or less, even without heating significantly high temperature, the metal particles with each other can be sufficiently sintered, demonstrating a good bond strength even after the environmental test but the initial only it can. Incidentally, if it exceeds 300 ° C. decomposition termination temperature T _e is the dressing, in order to express the good bonding strength, thereby giving a thermal damage when sintered at higher temperature to the workpieces.

When the amount of the coating material in the metal particles (A) is 1% by mass or more, it is possible to suppress the increase in viscosity of the bonding paste, exhibit good coating performance, and form a dense bonding coating film, which is good. Can develop bond strength. On the other hand, when the amount of the coating material in the metal particles (A) is 5% by mass or less, the residual coating material after sintering is suppressed, the generation of voids in the bonded coating film is suppressed, which is good. Can develop bond strength.

The coating material 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. ..

The bonding paste of the present invention contains a dispersion medium (B). The dispersion medium (B) has a function of dispersing the metal particles (A).
As the dispersion medium (B), a so-called organic solvent (B-1) having a boiling point of 180 ° C. or higher and lower than 230 ° C. is used as the dispersion medium (B).
80% by mass or more is contained in 100% by mass. By using a dispersion medium (B-1) having a boiling point of 180 ° C. or higher in an amount of 80% by mass or more, the bonding paste does not dry immediately when the bonding paste is applied to the object to be bonded, so that the bonding paste is continuous. Can be applied to many objects to be joined. On the other hand, by using a dispersion medium (B-1) having a boiling point of less than 230 ° C. in an amount of 80% by mass or more, the dispersion medium (B) rapidly volatilizes during heat sintering and is less likely to remain in the coating film after drying. It is less likely to cause voids during heating during bonding, and contributes to the development of good bonding strength.

Specific examples of the dispersion medium (B-1) include tarpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, dipropylene glycol monomethyl ether, and 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 solvent contained in hydrocarbon solvent and the like. .. Of these, tarpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, and dipropylene glycol monomethyl ether are particularly preferably used.
These dispersion media (B-1) may be used alone or in combination as appropriate.

It is important that the bonding paste of the present invention contains the metal particles (A) and the dispersion medium (B) in the form of metal particles (A) / dispersion medium (B) = 80/20 to 95/5 (mass ratio). .. By including the metal particles (A) in the above range, good coating suitability as a bonding paste can be ensured, the residual amount of organic components in the dry coating film is suppressed, and voids during heating during bonding ( The generation of voids) can be suppressed and good bonding strength can be exhibited.

The bonding paste of the present invention contains a total of 99 to 100% by mass of the metal particles (A) and the dispersion medium (B). That is, the bonding paste of the present invention can contain additives such as a sintering accelerator and a resin component, but the total amount thereof is less than 1% by mass in 100% by mass of the bonding paste. Even when the additive is contained, the generation of voids can be suppressed and a dense bonded coating film can be formed by using a very small amount of the additive.

The sintering accelerator is a compound having a functional group having a high affinity for the metal particles (A), and has a function of peeling off the organic substances surrounding the metal particles (A) due to the high affinity thereof. .. Since the metal particles from which the organic matter has been peeled off lose their dispersion stability and aggregate, the contact and fusion of the particles are promoted, and a dense metal film can be formed. The functional group having a high affinity for the metal particle (A) is not particularly limited, and polar groups and the like can be mentioned as an example. In particular, those containing a nitrogen atom have a high affinity for the metal particle (A) and are fired. It is preferably used as a binder.

As the resin component, a resin-type dispersant and a bonding strength after the initial / cooling cycle are used with the aim of preventing agglomeration of the metal particles (A) in the bonding paste and further improving viscosity stability over time and coating suitability. Acrylic, epoxy, urethane, polyester, polyamide-based binder resins and the like can be added for the purpose of further improvement.

The viscosity of the bonding paste of the present invention is preferably 1 to 150 Pa · s at 25 ° C. When the viscosity is in the above range, the coating performance becomes better.

With the bonding paste of the present invention, the first object to be bonded and the second object to be bonded can be bonded to obtain a bonded body.
For example, the bonding paste of the present invention is applied to the first bonded body, dried, and then the second bonded body is placed on the dried surface and then heated to heat the two bonded bodies. It can be joined to produce a joined body.
Alternatively, the bonding paste of the present invention is applied to the first bonded body, the second bonded body is placed on the bonding paste, and then heated to bond the two bonded bodies. Bonds can also be manufactured.

The method of applying the bonding paste is not particularly limited as long as it can be applied uniformly onto the member. Examples thereof include various printing methods such as screen printing, flexographic printing, offset printing, gravure printing, and gravure offset printing, and dispensers.

The sintering conditions in the joining step are appropriately changed, and examples thereof include conditions such as 200 to 300 ° C. under atmospheric pressure, a nitrogen atmosphere, a vacuum, a pressurized atmosphere, or a reducing atmosphere. Examples of the firing device include a hot air oven, an infrared oven, a reflow oven, a microwave oven, a hot plate, a light firing device, and the like. In the case of the light firing apparatus, the type of light to be irradiated is not particularly limited, and examples thereof include mercury lamps, metal halide lamps, chemical lamps, xenon lamps, carbon arc lamps, and laser lamps. These devices can be used individually or in combination as appropriate.

Prior to the firing step, a pre-drying step may be appropriately added for the purpose of removing organic components in the bonded coating film. For example, a heating step in a range of 60 to 180 ° C. in a hot air oven, an infrared oven, a reflow oven, a microwave oven, a hot plate, etc., a vacuum drying step, and the like can be mentioned.

Further, when the second object to be bonded is placed on the first object to be bonded to which the bonding paste of the present invention is applied, it is preferable to place the second object while applying pressure. The pressure is appropriately set depending on the viscosity of the bonding paste and the dry state of the paste, but is preferably 0.1 to 5 MPa, more preferably 0.3 to 3 MPa.

As a preferable method for joining the two objects to be bonded, the bonding paste of the present invention is applied to the first object to be bonded, dried, and then the second object to be bonded is dried on a dried surface from around room temperature. It was placed at a temperature close to the time of the hour, and after applying a pressure of 0.3 to 3 MPa, it was then kept under the above-mentioned pressure or further pressurized to about 200 to 300 ° C. 1 Examples thereof include a method in which the temperature is raised at a heating rate of about ° C./min to 15 ° C./min for sintering. 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.

The type of the object to be joined is not particularly limited, and examples thereof include metal members, electronic devices, plastic materials, and ceramic materials. It is preferable to join the metal members to each other, the metal member to the semiconductor element, and the metal member to the LED element.

Examples of the metal member include a copper substrate, a gold substrate, an aluminum substrate, and the like.
Examples of the electronic element include a semiconductor element and an LED element.
As the semiconductor element, gallium arsenide, gallium phosphide, cadmium sulfide and the like are used in addition to silicon and germanium. As the LED element, aluminum, silicon nitride, diamond, graphite, yttrium oxide, magnesium oxide and the like are used. In particular, power device devices such as silicon carbide and gallium nitride can be used.
Examples of the plastic material include polyimide, polyethylene, polypropylene, polyethylene terephthalate, polycarbonate, polyethylene naphthalate and the like.
Examples of the ceramic material include glass, silicon and the like.
The first joined body and the second joined body may be not only the same type but also different types of members. The above member may be appropriately processed by corona treatment, plating or the like in order to increase the joint strength.

Although the embodiments of the present invention have been described above, the present invention is not limited, and various modifications can be made without departing from the gist of the present invention.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

(Synthesis Example 1) Metal Particle A1
Under a nitrogen atmosphere, 200 parts of toluene and 22.3 parts of silver hexanoate were added while stirring at room temperature to prepare a 0.5 M solution, and then 2.3 parts of diethylaminoethanol (0.2 mol times as much as 1 mol of metal) as a dispersant. ), 0.28 part of oleic acid (0.01 mol times with respect to 1 mol of metal) was added and dissolved. Then, when 73.1 parts of an aqueous solution of dihydrazide succinate (hereinafter referred to as SUDH) having a concentration of 20% (hereinafter, 2 mol times the hydrazide group was added to 1 mol of the metal) was added dropwise as a reducing agent, the liquid color changed from pale yellow to dark brown. The temperature was raised to 40 ° C. to further promote the reaction, and the reaction was allowed to proceed. After standing and separating, excess reducing agent and impurities are removed by taking out the aqueous phase, distilled water is added to the toluene layer several times, washing and separation are repeated, then toluene is added and the supernatant is centrifuged. The step of removing the above was repeated twice. The precipitate was dried to obtain metal particles A1 coated with caproic acid and oleic acid. 1% integrated particle size distribution particle size (d1) is 30 to 200 nm, 50% integrated particle size distribution particle size (d50) is 100 to 350 nm, 99% integrated particle size distribution particle size (d99).
When the particle size of the metal particle A1 was determined by the method described later, the 1% integrated particle size distribution particle size (d1) was 45 nm, the 50% integrated particle size distribution particle size (d50) was 150 nm, and the 99% integrated particle size distribution particle. The diameter (d99) was 450 nm.
Further, when the decomposition start temperature T _s , the decomposition end temperature T _e , _{and the mass reduction rate between T s} and T _e of the metal particles A1 were determined by the method described later, the decomposition start temperature T _s was 170 ° C. and the decomposition ended. The temperature T _e was 270 ° C., and the mass loss rate between _{T s} and T _{e was 2.7%.}

(Synthesis Example 2) Metal Particle A2
Metal particles A2 coated with caproic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that the amount of oleic acid was 0.23 parts (0.008 mol times with respect to 1 mol of metal), and the particle size and decomposition were started. The temperature and the like were also determined in the same manner as in Synthesis Example 1.

(Synthesis Example 3) Metal Particle A3
10 parts of silver nitrate was dissolved in 500 parts of ethylene glycol. Next, 5 parts of polyvinylpyrrolidone was dispersed in ethylene glycol. Next, after raising the temperature of ethylene glycol to 150 ° C. (reaction temperature), the reaction was carried out for 1 hour while maintaining the reaction temperature of 150 ° C. and stirring at a rotation speed of 400 rpm. At this time, the reaction between silver nitrate and ethylene glycol generated nitrogen oxide gas, and the silver nitrate was reduced to obtain a dispersion of metal particles A3 coated with polyvinylpyrrolidone. The dispersion of the metal particles A3 was centrifuged to remove the supernatant, 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 coated with polyvinylpyrrolidone, and the particle size, decomposition start temperature, and the like were determined in the same manner as in Synthesis Example 1.

(Synthesis Example 4) Metal Particle A4
While sufficiently stirring 50 parts of 3-methoxypropylamine, 5 parts of dodecylamine and 60 parts of diglycolamine, 45 parts of silver oxalate was added to thicken the viscosity. The obtained thickening substance was placed in a constant temperature bath and reacted, and then 100 parts of repuric acid was added and further reacted to obtain a suspension. After adding methanol and stirring, silver particles were precipitated and separated by centrifugation, and the supernatant was removed. This operation was repeated once more to obtain metal particles A4 coated with repuric acid, and the particle size, decomposition start temperature, and the like were determined in the same manner as in Synthesis Example 1.

(Synthesis Example 5) Metal Particle A5
Metal particles A5 coated with propionic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that 18.1 parts of silver propionate was used instead of 22.3 parts of silver hexanoate, and the particle size and decomposition start temperature were obtained. Etc. were also obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 6) Metal Particle A6
Metal particles A6 coated with pentanic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that 20.9 parts of silver pentanate was used instead of 22.3 parts of silver hexanoate, and the particle size and decomposition start temperature were obtained. Etc. were also obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 7) Metal Particle A7
Metal particles A7 coated with myristic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that 33.5 parts of silver myristic acid was used instead of 22.3 parts of silver hexanoate, and the particle size and decomposition start temperature were obtained. Etc. were also obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 8) Metal Particle A8
Metal particles A8 coated with stearic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that 39.1 parts of silver stearate was used instead of 22.3 parts of silver hexanoate, and the particle size and decomposition start temperature were obtained. Etc. were also obtained in the same manner as in Synthesis Example 1.

(Metal particles A9)
NCXAGPD200 manufactured by nanoComposix, which is silver particles coated with polyvinylpyrrolidone, was determined in the same manner as in Synthesis Example 1 in terms of particle size, decomposition start temperature, and the like.

(Synthesis Example 101) Metal Particle A101
Metal particles A5 coated with caproic acid and oleic acid were obtained in the same manner as in Synthesis Example 1 except that the amount of silver hexanoate was changed from 22.3 parts to 23 parts, and the particle size, decomposition start temperature, etc. were also synthesized. It was obtained in the same manner as in Example 1.

(Synthesis Example 102) Metal Particle A102
After putting 3400 parts of water into the reaction vessel to create a nitrogen atmosphere, the temperature was adjusted so that the temperature became 60 ° C. Further, 7 parts of aqueous ammonia containing 28% by mass of ammonia was put into the reaction vessel, and then the mixture was stirred for 1 minute. Next, 45 parts of caproic acid was added, and the mixture was stirred for 4 minutes. Then, 24 parts of a 50% by mass hydrazine hydrate aqueous solution was added (reducing agent solution). An aqueous silver nitrate solution prepared by dissolving 34 parts of silver nitrate crystals in 180 parts of water was prepared in another container (silver salt aqueous solution). 0.00008 parts of copper nitrate trihydrate was further added to the 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 them, and the reduction reaction was started. The change in the color of the slurry subsided in about 10 seconds from the start of the reduction reaction. After aging for 10 minutes with stirring, solid-liquid separation by suction filtration, washing with pure water, and drying at 40 ° C. for 12 hours were performed to obtain metal particles A102 coated with hexanoic acid, and the particle size and decomposition start temperature were obtained. Etc. were obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 103) Metal Particle A103
135 parts of silver nitrate was dissolved in 720 parts of pure water (raw material liquid). 14,000 parts of pure water was charged in another container, and nitrogen was aerated there for 30 minutes to remove dissolved oxygen, and the temperature was raised to 40 ° C. Then, 180 parts of sorbic acid was added, and then 28 parts of 28% aqueous ammonia was added as a stabilizer. Stirring of the ammonia-added solution was continued, and 60 parts of hydrous hydrazine (purity 80%) was added as a reducing agent 5 minutes after the start of preparation of the silver particles to prepare a reducing solution. After 10 minutes from the start of preparation, the raw material solution whose temperature was adjusted to 40 ° C. was added to the reducing solution at once to react, stirring was completed, and the mixture was aged for 30 minutes and coated with sorbic acid. Was formed. Then, it was filtered and washed with pure water to obtain a silver particle agglomerate. The silver particle agglomerates were dried in a vacuum dryer at 80 ° C. for 12 hours to obtain metal particles A103 coated with sorbic acid, and the particle size, decomposition start temperature, etc. were determined in the same manner as in Synthesis Example 1. It was.

(Synthesis Example 104) Metal Particle A104
15 parts of hexylamine was added to 200 parts of toluene, and the mixture was stirred. While stirring, 10 parts of silver nitrate was added, and when silver nitrate was dissolved, 5 parts of oleic acid and 10 parts of caproic acid were sequentially added to prepare a toluene solution of silver nitrate. To this toluene solution of silver nitrate, a 0.02 g / mL aqueous sodium hydride prepared by adding 1 part of sodium hydride to 50 parts of ion-exchanged water was added dropwise, and stirring was continued for 1 hour to obtain silver particles. Was generated. Then, 250 parts of methanol was added to precipitate the silver particles, and the silver particles were completely precipitated by centrifugation, and then the reaction residue and the solvent contained in the supernatant were removed. The precipitate containing silver particles remaining after the supernatant was removed (untreated silver particle composition) was heat-treated at 60 ° C. for 45 minutes under reduced pressure using an evaporator, and in the silver particle composition, hexylamine, The amount of organic substances containing oleic acid and caproic acid is reduced to an appropriate amount, and finally dried to obtain metal particles A104 coated with hexylamine, oleic acid and caproic acid. It was calculated in the same way.

(Synthesis Example 105) Metal Particle A105
After putting 3400 parts of water into the reaction vessel to create a nitrogen atmosphere, the temperature was adjusted so that the temperature became 60 ° C. Further, 7 parts of aqueous ammonia containing 28% by mass of ammonia was put into the reaction vessel, and then the mixture was stirred for 1 minute. Next, 45 parts of sorbic acid was added, and the mixture was stirred for 4 minutes. Then, 24 parts of a 50% by mass hydrazine hydrate aqueous solution was added (reducing agent solution). An aqueous silver nitrate solution prepared by dissolving 34 parts of silver nitrate crystals in 180 parts of water was prepared in another container (silver salt aqueous solution). Then, the silver salt aqueous solution was added to the reducing agent solution all at once to mix them, and the reduction reaction was started. The change in the color of the slurry subsided in about 10 seconds from the start of the reduction reaction. After aging for 10 minutes with stirring, solid-liquid separation by suction filtration, washing with pure water, and drying at 40 ° C. for 12 hours were performed to obtain metal particles A105 coated with sorbic acid, and the particle size and decomposition start temperature were obtained. Etc. were obtained in the same manner as in Synthesis Example 1.

(Synthesis Example 106) Metal Particle A106
Add 3 parts of ricinoleic acid, 260 parts of N, N-dimethyl-1,3-diaminopropane, and 480 parts of butanol and stir for about 1 minute, then add 320 parts of silver oxalate and stir 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 at 90 ° C. for 30 minutes. After allowing to cool, 1500 parts of methanol was added and stirred, and then a centrifuge operation was performed to remove the supernatant. The steps of adding 1500 parts of methanol, stirring, centrifuging, and removing the supernatant were repeated twice, and then dried to obtain metal particles A106 coated with ricinoleic acid. It was calculated in the same way.

(Synthetic Example 107) Metal Particle 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 for 1 minute. After stirring to some extent, 320 parts of silver oxalate was 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 at 90 ° C. for 30 minutes. After allowing to cool, 1500 parts of methanol was added and stirred, and then a centrifuge operation was carried out for 1 minute to remove the supernatant. The steps of adding 1500 parts of methanol, stirring, centrifuging, and removing the supernatant were repeated twice, and then dried to obtain metal particles A107 coated with oxalic acid. It was calculated in the same way.

(Synthesis Example 301)
<Metal particle A201>
While sufficiently stirring 20 parts of 3-methoxypropylamine, 30 parts of silver oxalate was added to thicken the mixture. The obtained thickening substance was placed in a constant temperature bath and reacted, and then 100 parts of repuric acid was added and further reacted to obtain a suspension. After adding methanol and stirring, silver particles were precipitated and separated by centrifugation, and the supernatant was removed. After repeating this operation once more, it was dried to obtain metal particles A201 coated with repuric acid. When the particle size, decomposition start temperature, etc. were obtained in the same manner as in Synthesis Example 1, the 1% integrated particle size distribution particle size (d1) was 15 nm, and the 50% integrated particle size distribution particle size (d50) was 45 nm, 99% integrated. Particle size distribution The particle size (d99) was 95 nm, the decomposition start temperature T _s was 150 ° C., the decomposition end temperature T _e was 230 ° C., and the mass reduction rate between _{T s} and T _{e was 4.9%.}

<Metal particle A301>
The metal particles A5: 58.5 parts obtained in Synthesis Example 5 and the metal particles A201: 31.5 parts were mixed to obtain metal particles A301, and the particle size, decomposition start temperature, etc. were the same as in Synthesis Example 1. I asked.

(Synthesis Example 302)
The metal particles A5: 72 parts obtained in Synthesis Example 5 and the metal particles A201: 18 parts were mixed to obtain metal particles A302, and the particle size, decomposition start temperature, and the like were determined in the same manner as in Synthesis Example 1.

(Synthesis Example 303)
81 parts of metal particles A105 obtained in Synthesis Example 105, 1% integrated particle size distribution particle size (d1) is 0.1 μm, 50% integrated particle size distribution particle size (d50) is 0.6 μm, 99% integrated particles. Diameter distribution Particle size (d99) is 1.2 μm, silver particles “D2-1-C” manufactured by DOWA Electronics Co., Ltd .: 9 parts are mixed to obtain metal particles A303, and the particle size, decomposition start temperature, etc. are synthesized. It was obtained in the same manner as in Example 1.
When the particle size and decomposition start temperature of the silver particles "D2-1-C" alone were to be obtained in the same manner as in Synthesis Example 1, the particle size could be obtained, but the decomposition start temperature was obtained. However, no clear mass loss was observed, and the mass loss rate at 300 ° C. was less than 0.2% based on the mass at 23 ° C.

(Synthesis Example 304)
Metal particles A304 were obtained in the same manner as in Synthesis Example 303 except that the metal particles A 105: 45 parts and the above-mentioned “D2-1-C”: 45 parts were obtained, and the particle size, decomposition start temperature, etc. were the same as in Synthesis Example 1. I asked.

(Synthesis Example 305)
1% integrated particle size distribution particle size (d1) is 0.1 μm, 50% integrated particle size distribution particle size (d50) is 1.0 μm, 99% integrated particle size distribution particle size (d99) is 3.2 μm, Toxen Industries Silver particles "LM1" manufactured by Co., Ltd .: 67.5 parts, 1% integrated particle size distribution particle size (d1) is 2.1 μm, 50% integrated particle size distribution particle size (d50) is 6.0 μm, 99% Integrated particle size distribution Particle size (d99) is 10.1 μm, silver particles “AgC239” manufactured by Fukuda Metal Foil Co., Ltd .: 22.5 parts are mixed to obtain metal particles A305, and the particle size, decomposition start temperature, etc. It was obtained in the same manner as in Synthesis Example 1.
When the particle size and decomposition start temperature of each of the silver particles "LM1" and "AgC239" were tried to be obtained in the same manner as in Synthesis Example 1, the particle size could be obtained, but the decomposition start temperature was obtained. However, no clear mass loss was observed, and the mass loss rate at 300 ° C. was less than 0.2% based on the mass at 23 ° C.

(Synthesis Example 306)
The metal particles A106: 9 parts obtained in Synthesis Example 106 and the metal particles A107: 81 parts obtained in Synthesis Example 107 were mixed to obtain metal particles A306, and the particle size, decomposition start temperature, etc. were the same as in Synthesis Example 1. I asked for it.

(Synthesis Example 307)
The metal particles A5: 45 parts obtained in Synthesis Example 5 and the metal particles A201: 45 parts were mixed to obtain metal particles A307, and the particle size, decomposition start temperature, and the like were determined in the same manner as in Synthesis Example 1.

[Measurement of particle size]
Isopropyl alcohol was added to each metal particle and dispersed by a sonic disperser to obtain a dispersion liquid of 0.5% by mass, and the particle size of the dispersion liquid was measured using Nanotrack UPA-EX150 (manufactured by Nikkiso Co., Ltd.). , 1% integrated particle size distribution particle size (d1), 50% integrated particle size distribution particle size (d50), and 99% integrated particle size distribution particle size (d99) of each metal particle were determined.

[Decomposition start temperature, decomposition end temperature, mass reduction rate]
For each metal particle, the temperature was raised at a heating rate of 5 ° C./min using a differential thermal-thermogravimetric simultaneous measuring device (TG-DTA), and the decomposition start temperature, decomposition end temperature, and mass reduction rate were determined. ..
_{As shown in FIG. 1, let T s be} the extrapolation start temperature of the heat generation peak on the lowest temperature side shown by the DTA curve, and let _{T e} be the extrapolation end temperature of the heat generation peak on the hottest side shown by the DTA curve. .. It is considered that the decomposition of the coating material starts from the extrapolation start temperature T _s , the mass of the metal particles begins to decrease, and _{the decomposition of the coating material ends at the extrapolation end temperature T e.} Is called the decomposition end temperature.
Mass reduction rate = [(mass at decomposition start temperature-mass at decomposition end temperature) / mass at decomposition start temperature] x 100
A slight decrease in mass of metal particles may be observed even in a region lower than the decomposition start temperature T _s and in a region higher than the decomposition end temperature T _e , but if a clear exothermic peak is not observed, decomposition occurs. It is understood that it is not caused.

[Example 1]
Metal particles A: 1:85 parts by mass and tarpineol: 15 parts by mass were mixed using a self-revolving stirrer to prepare a bonding paste, which was evaluated by the method described later.

[Examples 2 to 11], [Comparative Examples 1 to 6]
According to the composition of Tables 1 and 2, the type of metal particles and the amount of tarpineol were changed, and a bonding paste was obtained and evaluated in the same manner as in Example 1.

[Comparative Examples 7 to 10]
According to the composition of Table 2, the type of metal particles and the amount of tarpineol were changed, the following additives were further added, and a bonding paste was obtained and evaluated in the same manner as in Example 1.
(C1) Curing accelerator: dicyandiamide jER Cure DICY7 manufactured by Mitsubishi Chemical Corporation
(C2) Resin-type dispersant: Acrylic copolymer-based resin-type dispersant DISPER-BYK-2020

[Examples 12 to 20], [Comparative Examples 11 to 17]
According to the compositions of Tables 3 to 4, a bonding paste was obtained and evaluated in the same manner as in Example 1 using 1:85 parts by mass of metal particles A and 15 parts by mass of various dispersion media. In addition, Table 3 also shows Example 1. Since dihydroterpineol in Table 3 contains an isomer, it exhibits a wide boiling point of 200 to 220 ° C.

[Examples 21 to 22], [Comparative Examples 18 to 22]
According to the composition of Table 5, using metal particles A301 to A307: 90 parts by mass and tarpineol: 10 parts by mass, a bonding paste was obtained and evaluated in the same manner as in Example 1.

[Initial viscosity measurement]
Immediately after preparing the bonding paste, the viscosity was measured in an environment of 25 ° C. using an E-type viscometer with a jig of 3 ° and a rotor of R = 7.7 mm at a rotation speed of 5 min ^-1.

[Viscosity stability over time]
After each bonding paste was left in an environment of 23 ° C. for 30 days, it was measured in the same manner as the initial viscosity measurement.
〇: Viscosity change rate is greater than -20% and less than + 20% Δ: Viscosity change rate is greater than -50% and -20% or less, or + 20% or more and less than + 50% ×: Viscosity change rate is -50% or less , Or + 50% or more When the viscosity, which was initially 100 Pa · s, changes to 200 Pa · s, it is defined as + 100% change.

[Applicability]
Each bonding paste was applied to the following base material 1 under the following conditions, and the application suitability after the first and 100 consecutive times was judged according to the following criteria. In addition, 100 times of continuous coating was applied to a new base material 1 each time.
<Base material 1>
-Gold-plated copper base material: 20 x 20 x 3 mm
<Application conditions>
-Metal mask: Opening 4 mm square, plate thickness 50 μm (manufactured by Celia Corporation)
-Metal squeegee: 40 mm x 250 mm, thickness 1 mm (manufactured by Celia Corporation)
<Evaluation criteria>
◯: A state in which the bonding material is uniformly adhered to the entire opening (4 mm square).
Δ: A state in which the bonding material is attached to a part of the opening (range of 2 to 3 mm square).
X: A state in which the bonding material adheres only to the 2 mm square range or less of the opening, and the adhered portion is cracked.

[Preparation of joint]
Each bonding paste is applied to the base material 1 once under the above conditions, dried at 75 ° C. for 5 minutes, and then the following base material 2 (chip) is placed on the dried surface to form the base material 2. Pressurization was performed from above under the following mounting conditions, and the base material 2 was temporarily bonded to the base material 1. Next, the temporary bonded body was heated under the following sintering conditions to obtain a bonded body.
<Base material 2>
-Gold-plated Si chip: 5 x 5 x 0.3 mm
<Implementation conditions>
・ Pressurize at 25 ° C, 0.5 MPa for 10 seconds <Sintering conditions>
-The temporary joint was placed in a hot air oven, and the temperature was raised from room temperature to 250 ° C. under the condition of 2.5 ° C./min, and when it reached 250 ° C., the temperature was maintained at the same temperature for 1 hour.

[Joint strength (initial, after thermal cycle test]
The joint strength (die shear strength) of the obtained joint was measured with the following measuring device and test conditions.
Measuring device: Universal bond tester (4000 series manufactured by Daiji Japan Co., Ltd.)
<Test conditions>
・ Measurement height: 100 μm
・ Measurement speed: 500 μm / s
Specifically, the base material 1 is fixed, and the position of 100 μm in height is pushed toward the base material 2 from the interface between the base material 1 and the bonding material at a speed of 500 μm / s at an initial stage where the bonding is broken. The strength and the strength after the following cycle test were determined.
<Cold heat cycle test>
After holding the bonded product under a temperature condition of −40 ° C. for 30 minutes, the treatment step of holding the bonded body under a temperature condition of 150 ° C. for 30 minutes was defined as one cycle, and this treatment was performed for 300 cycles.

⊚: 30 MPa or more ◯: 25 MPa or more and less than 30 MPa.
X: less than 25 MPa

As shown in Tables 1, 3 and 5, the bonding paste of the present invention of Examples 1 to 22 is excellent in storage (viscosity) stability over time and coating suitability, and when this bonding paste is used, the initial and environmental (cold heat cycle) ) It has become possible to obtain a bonded body with high bonding strength after the test.

On the other hand, as shown in Tables 2, 4 and 5,
Comparative Examples 1 to 4 and 18 to 22 using metal particles whose 1% integrated particle size distribution particle size (d1), 50% integrated particle size distribution particle size (d50), and 99% integrated particle size distribution particle size are not in the optimum range. ,
Comparative Examples 5 to 6 in which the ratio of the metal particles to the dispersion medium is not in the optimum range,
Comparative Examples 7 to 10 in which the total ratio of the metal particles and the dispersion medium in the bonding paste is not in the optimum range,
Comparative Examples 11 to 17 using a dispersion medium whose boiling point is not in the optimum range,
Each of the bonding pastes in No. 1 has insufficient storage stability over time (viscosity) and coating suitability, resulting in inferior bonding strength in the initial stage and after the environmental (cold heat cycle) test of the bonded body obtained by using this bonding paste. It was.

Claims (6)

The metal particles (A) and the dispersion medium (B) coated with the organic component (a) are mixed with the metal particles (A) / dispersion medium (B) at a ratio of 80/20 to 95/5 (mass ratio). A total of 99 to 100% by mass of the metal particles (A) and the dispersion medium (B) is contained.
The metal particles (A) have a 1% integrated particle size distribution particle size (d1) of 30 to 200 nm, a 50% integrated particle size distribution particle size (d50) of 100 to 350 nm, and a 99% integrated particle size distribution particle size (d99). Is 300-900 nm
The determined by differential thermal analysis metal particles (A) hottest side of the exothermic peak extrapolated end temperature T _e is 200 ° C. or more, and at 300 ° C. or less,
When the mass of the metal particles (A) _{at the external starting temperature T s} of the exothermic peak on the lowest temperature side of the metal particles (A) determined by differential thermal analysis is 100% by mass.
The mass reduction rate of the metal particles (A) at the extrapolation end temperature Te is 1 to 5% by mass.
The dispersion medium (B) contains an organic solvent (B-1) having a boiling point of 180 ° C. or higher and lower than 230 ° C. in an amount of 80% by mass or more of the entire dispersion medium.
Bonding paste. Claim that the organic solvent (B-1) comprises one or more of tarpineol, dihydroterpineol, carbitol, carbitol acetate, butyl carbitol, isophorone, γ-butyl lactone, and dipropylene glycol monomethyl ether. Item 1. The bonding paste according to item 1. The bonding paste according to claim 1 or 2, which has a viscosity of 1 to 150 Pa · s. A bonded body in which a first bonded body and a second bonded body are bonded by the bonding paste according to any one of claims 1 to 3. The bonding paste according to claims 1 to 3 is applied to the first object to be bonded, dried, and then the second object to be bonded is placed on the dried surface, and a pressure of 0.3 to 3 MPa is applied. A method for producing a bonded body, wherein the temperature is raised to 200 to 300 ° C. in a state where the pressure is still applied or in a state where the pressure is further applied. The bonded body according to claim 5, wherein after the temperature rise is completed, the temperature at the end of the temperature rise is maintained for 10 minutes to 2 hours while applying the pressure at the end of the temperature rise. Production method.

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