JP2022001666A - Joining method using microsize particle and joined body - Google Patents

Abstract

To provide an inexpensive and simple low temperature joining method capable of obtaining a joined part in which residual organic components and crystal grain boundaries in a joining layer can be reduced, and having high thermal conductivity and electrical conductivity and further having excellent heat resistance, and a joined body obtained by the joining method.SOLUTION: A joining method comprises a process where, using a composition for joining comprising conductive powder provided with a radially extended projection part and a recessed part at the gap of the projecting part and comprising silver including metallic grains or ceramic grains as a nucleus material for crystally growing silver as a conductive material at the inside, in which the average grain size of the nucleus material is 1 to 10 μm and aluminum nitride grains having the average grain size of 10 to 100 nm, after the composition for joining is interposed between the two members to be joined, the member is heated to 150 to 350°C and is further pressurized.SELECTED DRAWING: None

Description

The present invention relates to a joining method using micro-sized silver particles, and more specifically, a joining method capable of obtaining a joining portion having high heat resistance in addition to being excellent in thermal conductivity and electrical conductivity, and the above-mentioned. Regarding the joined body obtained by the joining method.

Conventionally, solders, conductive adhesives, silver pastes, anisotropic conductive films and the like have been used to mechanically and / or electrically and / or thermally bond metal parts to each other. These conductive adhesives, silver pastes, anisotropic conductive films and the like may be used not only for metal parts but also for joining ceramic parts, resin parts and the like. For example, bonding of a light emitting element such as an LED to a substrate, bonding of a semiconductor chip to a substrate, bonding of these substrates to a heat radiating member, and the like can be mentioned.

Among them, adhesives, pastes and films containing conductive fillers made of solder and metal are used for joining parts that require electrical connection. Furthermore, since metals generally have high thermal conductivity, adhesives, pastes and films containing solder and conductive fillers may be used to increase heat dissipation.

On the other hand, for example, when a high-intensity lighting device or a light-emitting device is manufactured using a light-emitting element such as an LED, or a semiconductor device called a power device, which operates at a high temperature and with high efficiency, is manufactured. In some cases, the calorific value tends to increase. Attempts have been made to improve the efficiency of devices and devices to reduce heat generation, but at present, sufficient results have not been achieved, and the actual operating temperature of devices and devices is rising.

Further, from the viewpoint of preventing damage to the device during bonding, a bonding material capable of ensuring sufficient bonding strength at a low bonding temperature (for example, 350 ° C. or lower) is required. Therefore, the bonding material for bonding devices, elements, etc. is required to have heat resistance that can withstand a decrease in the bonding temperature and an increase in the operating temperature due to the operation of the device after bonding to maintain sufficient bonding strength. However, it is often not possible to adequately deal with conventional bonding materials. For example, in solder, members are joined together through a process of heating the metal above its melting point (reflow process), but since the melting point is generally unique to its composition, heating (bonding) is performed when trying to raise the heat resistant temperature. The temperature will also rise.

Furthermore, when several layers of elements and substrates are laminated and joined using solder, it is necessary to go through heating steps for the number of layers to be overlapped, and in order to prevent melting of the already joined parts, the solder used for the next joining It is necessary to lower the melting point (bonding temperature) of the solder, and the number of types of solder composition required for the number of layers to be overlapped is required, which makes the handling complicated.

Under such circumstances, in recent years, as a substitute material for high-temperature solder, a bonding material using metal nanoparticles mainly composed of precious metals such as silver and gold has been developed (for example, Patent Document 1: Japanese Patent Application Laid-Open No. 2012-046779). Issue). However, not only are metal nanoparticles expensive, but organic substances used as dispersants and solvents for metal nanoparticles remain in the bonding layer obtained by sintering the metal nanoparticles. Further, in the bonding layer obtained by sintering metal nanoparticles, the ratio of grain boundaries becomes large, which causes a decrease in thermal conductivity and electrical conductivity. In addition, when metal nanoparticles are used for bonding, there is a problem that the volume change during bonding becomes large due to evaporation of organic substances.

On the other hand, the inventors can reduce the residual organic components and grain boundaries in the bonding layer by using the colloidal-shaped micro-sized silver particles, and the joint portion has excellent thermal conductivity and electrical conductivity. We are proposing an inexpensive joining method that can be obtained. Specifically, in Patent Document 2 (Japanese Unexamined Patent Publication No. 2015-57291), a convex portion extending radially and a concave portion in the gap between the convex portions are provided, and silver as a conductive material is provided inside. It is a nuclear material for growing crystals, and the nuclear material contains silver including metal particles or ceramic particles, and the average particle size of the nuclear material is 1 to 10 μm. A step of using a bonding composition containing a conductive powder, interposing the bonding composition between two members to be bonded, and then heating the member to 150 to 350 ° C. and pressurizing the member is included. The characteristic joining method is disclosed.

In the bonding method described in Patent Document 2, by using micro-sized silver particles having an average particle size of 1 to 10 μm, organic substances for ensuring dispersibility can be reduced, and organic substances in the bonding layer can be reduced. It is possible to significantly reduce the residual organic component and the volume change of the bonding layer during the bonding process. Further, since the ratio of the crystal grain boundaries in the bonding layer can be reduced as compared with the nano-sized metal particles, a bonding portion having excellent thermal conductivity and electrical conductivity can be obtained. Further, since the micro-sized silver particles can be produced at a lower cost as compared with general metal nanoparticles, the cost for bonding can be reduced. Further, since the fine protrusions of the micro-sized silver particles ensure low-temperature sinterability, bonding at a low temperature of 150 to 350 ° C. is possible.

Japanese Unexamined Patent Publication No. 2012-046779 JP-A-2015-57291

In recent years, the use of SiC, GaN, etc. as semiconductor materials inside various power devices has been studied, and some of these materials exhibit high performance under high temperature conditions of 300 ° C. or higher. Therefore, semiconductor chips and substrates High heat resistance is also required for the bonding layer that is responsible for bonding with.

On the other hand, the bonding layer obtained by the bonding method described in Patent Document 2 can reduce the ratio of grain boundaries in the bonding layer as compared with nano-sized metal particles, and has thermal conductivity and electricity. A joint having excellent conductivity can be obtained, but heat resistance is not sufficiently considered. It has also been reported that the bonding layer obtained by sintering metal particles undergoes structural changes due to high temperature exposure.

In view of the above circumstances, an object of the present invention is to reduce residual organic components and grain boundaries in the bonding layer, and to bond with high thermal conductivity and electrical conductivity as well as excellent heat resistance. It is an object of the present invention to provide an inexpensive and simple low-temperature joining method capable of obtaining a portion, and a bonded body obtained by the joining method.

As a result of intensive research on the composition of the bonding composition in order to achieve the above object, the present inventor has obtained aluminum nitride particles for imparting excellent heat resistance to the bonding layer, and micro-sized silver having a chestnut shape. We have found that it is extremely effective to uniformly disperse the particles by utilizing the voids formed by the convex portions and the concave portions of the particles in order to achieve the above object, and have reached the present invention.

That is, the present invention
It is provided with a convex portion extending radially and a concave portion in the gap between the convex portions, and is a nuclear material for growing silver as a conductive material inside, and is a metal-based material as the nuclear material. A conductive powder containing silver containing particles or ceramic particles and having an average particle size of the nuclear material of 1 to 10 μm.
Using a bonding composition containing aluminum nitride particles having an average particle size of 10 to 100 nm, the bonding composition is interposed between two members to be bonded, and then the member is brought to 150 to 350 ° C. Including the process of heating and pressurizing,
A joining method, which is characterized by the above.

In the bonding method of the present invention, aluminum nitride particles having an average particle size of 10 to 100 nm are uniformly dispersed in the bonding layer to impart good high-temperature stability to the bonding layer formed by sintering conductive powder. Can be done. Further, aluminum nitride has good compatibility with the silver sintered layer from the viewpoint of thermal conductivity and linear expansion coefficient, and can reduce the adverse effect of dispersing different materials in the silver sintered layer.

By setting the average particle size of the aluminum nitride particles to 10 nm or more, it is possible to effectively suppress the structural change when the bonded layer is kept at a high temperature. Further, by setting the average particle size of the aluminum nitride particles to 100 nm or less, it is possible to suppress a decrease in the denseness and strength of the bonding layer due to the dispersion of the aluminum nitride particles. Here, the average particle size of the aluminum nitride particles is preferably 15 to 80 nm, more preferably 20 to 60 nm.

Normally, it is extremely difficult to uniformly disperse fine ceramic particles in a bonding composition, but in the bonding method of the present invention, a concave portion is provided in the gap between the radially extending convex portion and the convex portion. By using so-called ceramic-shaped microparticles as metal particles, uniform dispersion of aluminum nitride particles is achieved. Specifically, the convex portions and the concave portions sufficiently and uniformly form an appropriate space for dispersing the aluminum nitride particles. Further, the conductive powder having convex portions and concave portions has a micro size (1 to 10 μm), and unlike general metal nanoparticles, it is suppressed that the dispersion state becomes inhomogeneous due to aggregation or the like.

Further, by using micro-sized silver particles having an average particle size of 1 to 10 μm, it is possible to reduce organic substances for ensuring dispersibility, etc., and the residual organic components in the bonding layer and the bonding layer in the bonding process. The volume change of can be significantly reduced. Further, since the ratio of the crystal grain boundaries in the bonding layer can be reduced as compared with the nano-sized metal particles, a bonding portion having excellent thermal conductivity and electrical conductivity can be obtained. Further, since the micro-sized silver particles can be produced at a lower cost as compared with general metal nanoparticles, the cost for bonding can be reduced. Here, since the fine protrusions of the micro-sized silver particles ensure low-temperature sinterability, bonding at a low temperature of 150 to 350 ° C. is possible.

Further, in the joining method of the present invention, the pressurization in the step can be as low as about 10 MPa, and the pressurization can be performed under the own weight of the member.

In the bonding method of the present invention, it is preferable that the content of the aluminum nitride particles in the bonding composition is 0.4 to 1.8% by mass. By setting the content of the aluminum nitride particles to 0.4% by mass or more, a sufficient number of aluminum nitride particles can be dispersed to impart high temperature stability to the bonding layer. Further, by setting the content of the aluminum nitride particles to 1.8% by mass or less, it is possible to suppress a decrease in the density and strength of the bonding layer due to the dispersion of the aluminum nitride particles, and in addition, it is practically used in a bonding composition. It is possible to impart coating characteristics that do not cause any problems. Here, the content of the aluminum nitride particles is preferably 0.7 to 1.3% by mass, more preferably 0.9 to 1.1% by mass.

In the joining method of the present invention, it is preferable that the shape of the convex portion is at least one shape selected from the group consisting of a needle shape, a rod shape, or a petal shape. Further, the bonding composition including all of the conductive powder having a needle-like shape of the convex portion, the conductive powder having a rod-like shape of the convex portion, and the conductive powder having a petal-like shape of the convex portion. It is preferable to use a thing. Since the convex portion has these shapes, a minute space in which the aluminum nitride particles can penetrate (disperse) is efficiently and uniformly formed, and the aluminum nitride particles are uniformly dispersed in the finally obtained bonding layer. Can be made to.

Further, in the bonding method of the present invention, it is preferable that the bonding composition contains 0.001 to 0.1% by mass of spherical ceramic particles having an average particle size of 10 to 100 μm. Spherical ceramic particles having an average particle size of 10 to 100 μm function as spacers, and if a small amount of spherical ceramic particles are present in the thickness direction of the bonding layer, the bonding layer having an arbitrary thickness can be formed with good reproducibility. can. The average particle size of the spherical ceramic particles is preferably 20 to 90 μm, more preferably 30 to 80 μm. Further, the content of the spherical ceramic particles is more preferably 0.002 to 0.01% by mass. For the spherical ceramic particles, for example, silica particles or the like can be used.

Further, the present invention
A bonded body in which one member to be joined and the other member to be joined are joined.
The one member to be joined and the other member to be joined are metallurgically joined via a joining layer.
The bonding layer contains metal particles and aluminum nitride particles.
The metal particles are nuclear materials for growing silver as a conductive material inside, and are silver particles containing metal particles or ceramic particles as the nuclear material.
The average particle size of the aluminum nitride particles is 10 to 100 nm, and the average particle size is 10 to 100 nm.
The content of the aluminum nitride particles in the bonding layer is 0.4 to 1.8% by mass.
Also provided are conjugates, characterized by.

In the bonded body of the present invention, aluminum nitride particles having an average particle size of 10 to 100 nm are dispersed in a bonded layer mainly formed by sintering silver particles, and the content of the aluminum nitride particles is 0.4. Since uniform dispersion is achieved even at ~ 1.8% by mass, the bonded layer has excellent thermal stability.

The average particle size of the aluminum nitride particles is preferably 15 to 80 nm, more preferably 20 to 60 nm. The content of the aluminum nitride particles is preferably 0.7 to 1.3% by mass, more preferably 0.9 to 1.1% by mass.

Further, in the bonded body of the present invention, metal-based particles or ceramic-based particles are mainly contained inside the silver particles forming the bonding layer, and these particles also contribute to the improvement of the thermal stability of the bonding layer. .. In particular, when ceramic particles are contained inside the silver particles, the effect is remarkable.

^{Further, in the bonded body of the present invention, the ratio of the number of voids having an area of 0.2 μm 2} or less with respect to the size of the voids measured by observing the cross section of the bonded layer is 90% or more with respect to the total number of voids. Is preferable. By suppressing the formation of coarse voids in the bonding layer, good mechanical properties and thermal stability are realized.

Further, in the bonded body of the present invention, it is preferable that the bonded layer contains 0.001 to 0.1% by mass of spherical ceramic particles having an average particle size of 10 to 100 μm. Spherical ceramic particles having an average particle size of 10 to 100 μm function as spacers and can homogenize the thickness of the bonding layer. The average particle size of the spherical ceramic particles is preferably 20 to 90 μm, more preferably 30 to 80 μm. Further, the content of the spherical ceramic particles is more preferably 0.002 to 0.01% by mass. The spherical ceramic particles can be, for example, silica particles or the like.

Further, in the bonded body of the present invention, it is preferable that the porosity of the bonding layer is 10% or less, and the porosity does not increase to 10% or more by leaving at a high temperature of 300 ° C. for 500 hours. With a semiconductor chip that uses a semiconductor material that exhibits high performance under high temperature conditions of 300 ° C or higher, for example, because the bonding layer is dense and the porosity does not increase to 10% or more due to long-term holding at high temperatures. It can be suitably used as a bonded body bonded to and from a substrate.

Further, in the bonded body of the present invention, it is preferable that the shear strength of the bonded layer is 40 MPa or more, and the shear strength of the bonded layer after being left at a high temperature of 300 ° C. for 500 hours is 30 MPa or more. A semiconductor chip in which a semiconductor material that exhibits high performance under high temperature conditions of, for example, 300 ° C. or higher is used because the bonding layer has these shear strengths and maintains high shear strength even after being held at high temperature for a long time. It can be suitably used as a bonded body in which the substrate is bonded to the substrate.

According to the present invention, residual organic components and grain boundaries in the joint layer can be reduced, and a joint portion having high thermal conductivity and electrical conductivity and excellent heat resistance can be obtained at low cost. It is possible to provide a simple low temperature bonding method and a bonded body obtained by the bonding method.

It is a schematic diagram which shows the mechanism which the aluminum nitride particles are uniformly dispersed in this invention. 6 is an SEM photograph of micro-sized silver particles used in the examples. It is an SEM photograph of the aluminum nitride particles used in the Example. It is an optical micrograph of the silica particle used in the Example. It is a schematic diagram of the joining test piece used in an Example. It is an SEM photograph of the junction layer cross section of the junction obtained in Example. It is an SEM photograph of the junction layer cross section of the junction obtained in the comparative example. It is a histogram which shows the area distribution of the void formed in the junction layer of the implementation junction. It is a histogram which shows the area distribution of the void formed in the junction layer of a comparative junction. It is an SEM observation image and Al element mapping of the cross section of the junction layer of the embodiment junction obtained in Example 1. It is a TEM observation image and element mapping of the junction layer of the embodiment junction obtained in Example 1. It is a graph which shows the relationship between the shear strength and the aluminum nitride particle content of each embodiment obtained in Example 2. FIG. It is a graph which shows the bonding strength of the bonded body obtained in Comparative Example 2 and the bonded body after high temperature exposure.

Hereinafter, the joining method of the present invention and a preferred embodiment of the joined body will be described in detail. It should be noted that the following description merely shows one embodiment of the present invention, and the present invention is not limited thereto, and duplicate description may be omitted.

1. 1. Bonding method (1) Bonding composition The bonding composition of the present embodiment contains metal particles having an average particle size of 1 to 10 μm and a chestnut-shaped conductive powder (micro-sized silver particles) having an average particle size of 10 to 10. It is characterized by being a mixture of 100 nm aluminum nitride particles and an organic solvent or the like, and contains a dispersant or the like as necessary. Each of these components will be described below.

(1-1) Conductive powder (micro-sized silver particles)
As the metal particles of the bonding composition of the present embodiment, it is preferable to use a sardine-shaped conductive powder having an average particle size of 1 to 10 μm. By setting the average particle size to micro size, dispersibility and stability are improved compared to nano-sized particles, so that the amount of organic matter required to ensure dispersibility and stability is significantly reduced. be able to. In addition, by setting the average particle size to less than 10 μm, a sufficient surface area can be obtained to secure contacts between metal particles and the like. The average particle size of the conductive powder can be measured by a laser particle counter, or can be actually measured from an electron micrograph, and further, it can be calculated from the electron micrograph using an image processing device. You can also.

Further, the metal particles of the bonding composition of the present embodiment are preferably (a) unevenness {that is, a convex portion (sometimes referred to as a protrusion) extending radially from the center of the particle, and the convex portion. It is provided with recesses (sometimes referred to as depressions) in the gaps between the parts, and}, and is a nuclear material for growing silver as a conductive material inside (b), and as the nuclear material, It is a conductive powder containing silver including metal particles or ceramic particles, and the average particle size of the nuclear material is 1 to 10 μm. The convex portions extending radially and the concave portions in the gap between the convex portions extending radially and the convex portions are in good contact with each other, and the contact portion is kept at a low temperature (150 to 350 ° C.). Sintering proceeds effectively.

As described above, the shape of the convex portion of the conductive powder is preferably at least one shape selected from the group consisting of needle-like (or fibrous), rod-like, and petal-like. Further, it is preferable that the bonding composition contains all of the conductive powder having a needle-shaped convex portion, the conductive powder having a rod-shaped convex portion, and the petal-shaped convex portion. ..

By combining a silver powder having a needle-shaped convex portion, a silver powder having a rod-shaped convex portion, and a silver powder having a petal-shaped convex portion, contact formation becomes easy and low-temperature sinterability is further improved. do. More specifically, when the total amount of the conductive powder is 100% by weight, the silver powder having needle-shaped protrusions is 10 to 50% by weight, the silver powder having rod-shaped protrusions is 15 to 50% by weight, and It is preferable to appropriately mix and use silver powder having petal-shaped protrusions within the range of 20 to 50% by weight.

The length of the convex portion is preferably more than 40% of the average radius of the sphere formed by the closed curved surface that is in contact with and surrounds the tip of the convex portion. The reason for this is that such a convex portion has an appropriate size, the fitting connection with the concave portion becomes more reliable, and the mechanical stability of the fitting portion is also improved. ..

The concave portion has a concave shape provided in the gap between the convex portions, and has a shape in which the convex portion can enter when viewed from the side in the cross-sectional direction (more ideally, the convex portion can be fitted and connected to the concave portion). Shape) is fine. The reason for this is that, with such a configuration, the convex portion and the concave portion can be easily fitted and connected between the adjacent conductive powders. Further, the depth (size) of the recess can be expressed by the volume of the recess in the conductive powder, that is, the porosity of the recess. Specifically, when the volume of the sphere having a closed curve surrounding the tip of the convex portion is 100% by volume, the porosity of the concave portion is preferably set to a value of 40% by volume or more. The reason for this is that if the porosity of the concave portion is less than 40% by volume, the fitting connection between the convex portion and the concave portion may be insufficient. On the other hand, if the porosity of the recesses becomes excessively large, the mechanical strength of the conductive powder may be significantly reduced, and an aggregated region of the aluminum nitride particles may be formed. Therefore, the porosity of the recesses is more preferably set to a value in the range of 42 to 70% by volume, and further preferably set to a value in the range of 45 to 60% by volume.

The nuclear material is preferably metal particles or ceramic particles (inorganic particles). The reason for this is that by using metallic particles, not only the specific gravity and the particle size can be easily adjusted, but also the shape retention and the electrical resistivity can be easily adjusted. Further, by using the ceramic particles, not only the specific gravity and the particle size can be easily adjusted, but also the characteristics such as shape retention and heat resistance can be further improved.

Here, examples of the metal-based particles include one type alone or a combination of two or more types such as silver particles, gold particles, copper particles, aluminum particles, zinc particles, solder particles, tin particles, and nickel particles. It is preferable to use it. Further, examples of the ceramic particles include one type alone or a combination of two or more types such as silica particles (white carbon), titanium oxide particles, zirconium oxide particles, aluminum oxide particles, zinc oxide particles, tin oxide particles, and niobium oxide particles. Be done. In particular, among these particles, by using silica particles (white carbon) or titanium oxide particles, it is not only easy to adjust the specific gravity, particle size, or electrical resistivity, but also the characteristics such as shape retention. It is a preferable nuclear material because it can be significantly improved.

Further, regarding the type of nuclear material, it is preferable that it is porous or agglomerated particles. The reason for this is that it is possible to uniformly extend the convex portions radially around the nuclear material of the porous or aggregated particles, and it is possible to obtain a conductive powder having a narrower particle size distribution and excellent shape retention. Because. Therefore, it is preferable that the BET surface area is set to a value in the range of ^{0.01 to 500 m 2} / g for the nuclear material composed of porous or aggregated particles. Whether or not the nuclear material is porous or aggregated particles can be easily confirmed by observing with an electron microscope.

The amount of the nuclear material added is preferably in the range of 0.01 to 30% by weight with respect to the total amount. The reason for this is that if the amount of the nuclear material added is less than 0.01% by weight, it may be difficult to uniformly extend the convex portions radially around the nuclear material. On the other hand, if the amount of the nuclear substance added exceeds 30% by weight, the electrical resistivity of the conductive powder may increase significantly. Therefore, the amount of the nuclear material added is more preferably set to a value in the range of 0.1 to 20% by weight, and preferably set to a value in the range of 0.5 to 10% by weight with respect to the total amount. More preferred. If the amount of the nuclear substance added is a predetermined amount or more, for example, 1% by weight or more, it can be measured using an electron probe microanalyzer (EPMA) as an example.

The metal particles of the bonding composition of the present embodiment are not particularly limited as long as they are conductive powders (micro-sized silver particles) having the above-mentioned characteristics, but for example, conductive powder manufactured by Kaken Tech Co., Ltd. is preferably used. Can be done.

(1-2) Aluminum Nitride Particles The bonding composition of the present embodiment contains aluminum nitride particles having an average particle size of 10 to 100 nm. By uniformly dispersing the aluminum nitride particles having an average particle size of 10 to 100 nm in the bonding layer, good high temperature stability can be imparted to the bonding layer formed by sintering the conductive powder. Further, aluminum nitride has good compatibility with the silver sintered layer from the viewpoint of thermal conductivity and linear expansion coefficient, and can reduce the adverse effect of being dispersed in the silver sintered layer. The method for measuring the average particle size of the aluminum nitride particles is not particularly limited, and various conventionally known measuring methods can be used. For example, it may be obtained from an observation image using a scanning electron microscope or a transmission electron microscope, or an X-ray small-angle scattering method or the like may be used.

By setting the average particle size of the aluminum nitride particles to 10 nm or more, it is possible to effectively suppress the structural change when the bonded layer is kept at a high temperature. Further, by setting the average particle size of the aluminum nitride particles to 100 nm or less, it is possible to suppress a decrease in the denseness and strength of the bonding layer due to the dispersion of the aluminum nitride particles. Here, the average particle size of the aluminum nitride particles is preferably 15 to 80 nm, more preferably 20 to 60 nm.

Further, it is preferable that the content of the aluminum nitride particles is 0.4 to 1.8% by mass. By setting the content of the aluminum nitride particles to 0.4% by mass or more, a sufficient number of aluminum nitride particles can be dispersed to impart high temperature stability to the bonding layer. Further, by setting the content of the aluminum nitride particles to 1.8% by mass or less, it is possible to suppress a decrease in the denseness and strength of the bonding layer due to the dispersion of the aluminum nitride particles. Here, the content of the aluminum nitride particles is preferably 0.7 to 1.3% by mass, more preferably 0.9 to 1.1% by mass.

(1-3) Spherical ceramic particles (spacer particles)
If necessary, the thickness of the bonding layer can be easily controlled by containing spherical ceramic particles. The average particle size of the spherical ceramic particles is preferably 10 to 100 μm, more preferably 20 to 90 μm, and most preferably 30 to 80 μm. The content of the spherical ceramic particles is preferably 0.001 to 0.1% by mass, more preferably 0.002 to 0.01% by mass. For the spherical ceramic particles, for example, silica particles or the like can be used.

(1-4) Others As the organic solvent used in the bonding composition of the present embodiment, various organic solvents can be used as long as the effects of the present invention are not impaired. Examples of the organic solvent include terpene-based solvent, ketone-based solvent, alcohol-based solvent, ester-based solvent, ether-based solvent, aliphatic hydrocarbon-based solvent, aromatic hydrocarbon-based solvent, cellosolve-based solvent, carbitol-based solvent and the like. Can be mentioned. More specifically, organic solvents such as tarpineol, methyl ethyl ketone, acetone, isopropanol, butyl carbitol, decane, undecane, tetradecane, benzene, toluene, hexane, diethyl ether, and kerosine can be used.

In addition to the above-mentioned components, the bonding composition of the present embodiment is provided with functions such as appropriate viscosity, adhesion, drying property, and printability according to the purpose of use, as long as the effects of the present invention are not impaired. A dispersion medium, for example, an oligomer component that acts as a binder, a resin component, an organic solvent (a part of the solid content may be dissolved or dispersed), a surfactant, a thickener, or a surface tension. Arbitrary components such as a modifier may be added. The optional component is not particularly limited.

As the dispersion medium among the optional components, various ones can be used as long as the effects of the present invention are not impaired, and examples thereof include hydrocarbons and alcohols.

Examples of the hydrocarbon include an aliphatic hydrocarbon, a cyclic hydrocarbon, an alicyclic hydrocarbon and the like, and each of them may be used alone or in combination of two or more.

Examples of the aliphatic hydrocarbons include saturated or unsaturated aliphatic hydrocarbons such as tetradecane, octadecane, heptamethylnonane, tetramethylpentadecane, hexane, heptane, octane, nonane, decane, tridecane, methylpentane, normal paraffin, and isoparaffin. Can be mentioned.

Examples of the cyclic hydrocarbon include toluene, xylene and the like.

Further, examples of the alicyclic hydrocarbons include limonene, dipentene, terpinene, tarpinene (also referred to as terpinene), nesole, sinen, orange flavor, terpinene, tarpinolene (also referred to as terpinene), phellandrene, menthadiene, and teleben. Examples thereof include dihydrocymen, moslen, isotelpinene, isotarpinene (also referred to as isotelpinene), critomen, kautsin, kajeptene, oilimen, pinene, televisionn, menthane, pinane, terpene, cyclohexane and the like.

Further, the alcohol is a compound containing one or more OH groups in the molecular structure, and examples thereof include aliphatic alcohols, cyclic alcohols and alicyclic alcohols, which may be used alone or in combination of two or more. May be good. Further, a part of the OH group may be derived to an acetoxy group or the like as long as the effect of the present invention is not impaired.

Examples of the fatty alcohol include heptanol, octanol (1-octanol, 2-octanol, 3-octanol, etc.), decanol (1-decanol, etc.), lauryl alcohol, tetradecyl alcohol, cetyl alcohol, 2-ethyl-1-. _{Saturated or unsaturated C 6-30} fatty alcohols such as hexanol, octadecyl alcohol, hexadecenol and oleyl alcohol can be mentioned.

Examples of the cyclic alcohol include cresol, eugenol and the like.

Further, examples of the alicyclic alcohol include cycloalkanol such as cyclohexanol, terpineol (including α, β, γ isomers, or any mixture thereof), terpene alcohol such as dihydroterpineol (monoterpene alcohol and the like). ), Dihydroterpineol, Miltenol, Sobrelol, Menthol, Calveol, Perylyl alcohol, Pinocarbol, Sobrelol, Belbenol and the like.

When the dispersion medium is contained in the bonding composition of the present embodiment, the content may be adjusted according to desired characteristics such as viscosity, and the content of the dispersion medium in the bonding composition is 1 to 30 mass by mass. % Is preferable. When the content of the dispersion medium is 1 to 30% by mass, the effect of adjusting the viscosity can be obtained within a range that is easy to use as a bonding composition. The more preferable content of the dispersion medium is 1 to 20% by mass, and the more preferable content is 1 to 15% by mass.

Examples of the resin component include polyester-based resins, polyurethane-based resins such as blocked isocyanate, polyacrylate-based resins, polyacrylamide-based resins, polyether-based resins, melamine-based resins, terpene-based resins, and the like. May be used alone or in combination of two or more.

Examples of the organic solvent include those listed as the above-mentioned dispersion mediums, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, 2-propyl alcohol, 1,3-propanediol, 1,2-propanediol, and 1 , 4-Butanediol, 1,2,6-hexanetriol, 1-ethoxy-2-propanol, 2-butoxyethanol, ethylene glycol, diethylene glycol, triethylene glycol, weight average molecular weight in the range of 200 or more and 1,000 or less Polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol having a weight average molecular weight in the range of 300 or more and 1,000 or less, N, N-dimethylformamide, dimethylsulfoxide, N-methyl-2- Examples thereof include pyrrolidone, N, N-dimethylacetamide, glycerin, acetone and the like, and these may be used alone or in combination of two or more.

Examples of the thickener include clay minerals such as clay, bentonite or hectrite, for example, emulsions such as polyester emulsion resin, acrylic emulsion resin, polyurethane emulsion resin or blocked isocyanate, methyl cellulose, carboxymethyl cellulose and hydroxyethyl cellulose. , Hydroxypropyl cellulose, cellulose derivatives such as hydroxypropylmethyl cellulose, polysaccharides such as xanthan gum or guar gum, etc., and these may be used alone or in combination of two or more.

Further, a surfactant different from the above organic component may be added. In a multi-component solvent-based metal colloidal dispersion, the surface of the coating film is likely to be roughened and the solid content is uneven due to the difference in the volatilization rate during drying. By adding a surfactant to the bonding composition of the present embodiment, these disadvantages can be suppressed, and a bonding composition capable of forming a uniform conductive film can be obtained.

The surfactant that can be used in the present embodiment is not particularly limited, and any of anionic surfactant, cationic surfactant, and nonionic surfactant can be used, for example, an alkylbenzene sulfonate. Quaternary ammonium salt and the like can be mentioned. A fluorosurfactant is preferable because the effect can be obtained with a small amount of addition.

As a method for adjusting the amount of the organic component within a predetermined range, it is convenient to adjust by heating. Further, it may be carried out by adjusting the amount of the organic component added when producing the conductive powder. Heating can be performed in an oven, an evaporator, or the like, and may be performed under reduced pressure. When it is carried out under normal pressure, it can be carried out in the atmosphere or in an inert atmosphere. In addition, amines (and carboxylic acids) can be added later for fine-tuning the amount of organic constituents.

The viscosity of the bonding composition of the present embodiment may be appropriately adjusted as long as the solid content concentration does not impair the effect of the present invention, but may be, for example, a viscosity range of 0.01 to 5000 Pa · S, and is 0. A viscosity range of 1 to 1000 Pa · S is more preferable, and a viscosity range of 1 to 100 Pa · S is particularly preferable. Within the viscosity range, a wide range of methods can be applied as a method for applying the bonding composition to the material to be bonded.

The viscosity can be adjusted by adjusting the particle size of the conductive powder, adjusting the content of organic substances, adjusting the amount of dispersion medium and other components added, adjusting the blending ratio of each component, adding a thickener, and the like. .. The viscosity of the composition for metal bonding can be measured, for example, with a cone plate type viscometer (for example, a rheometer MCR301 manufactured by Anton Pearl Co., Ltd.).

The bonding composition used in the bonding method of the present invention can be obtained by uniformly mixing the above-mentioned conductive powder, aluminum nitride particles, organic solvent and the like by various conventionally known methods. The mixing method may be dry mixing or wet mixing using a solvent or the like.

(2) Bonding Method By using the bonding composition of the present embodiment, high bonding strength can be obtained in bonding members that are heated. That is, the bonding composition application step of applying the bonding composition between the first bonded member and the second bonded member, and the first bonded member and the second bonded member. By a joining step of firing and joining the bonding composition applied between them at a desired temperature (for example, 350 ° C. or lower, preferably 150 to 300 ° C.), the first bonded member and the second bonded member are bonded. It can be joined to a member. Further, when firing, the temperature can be raised or lowered step by step. It is also possible to apply a surfactant, a surface activator, or the like to the surface of the member to be joined in advance.

As a result of repeated diligent studies, the present inventor can use the above-mentioned bonding composition of the present embodiment as the bonding composition in the bonding composition coating step to obtain the first member to be bonded and the second member. It has been found that, in addition to being able to more reliably join the members to be joined with high bonding strength (a bonded body can be obtained), it is possible to impart high thermal stability to the bonded layer obtained after bonding.

Here, the "coating" of the bonding composition of the present embodiment is a concept including both the case where the bonding composition is applied in a planar shape and the case where the bonding composition is applied (drawn) in a linear shape. The shape of the coating film made of the bonding composition in a state before being applied and fired by heating can be a desired shape. Therefore, in the bonded body of the present embodiment after firing by heating, the bonding composition is a concept including both a planar bonding layer and a linear bonding layer, and these planar bonding layers and linear bonding layers are included. The bonding layer may be continuous or discontinuous, and may include continuous portions and discontinuous portions.

The first member to be joined and the second member to be joined that can be used in the present embodiment are particularly limited as long as they can be joined by applying a bonding composition and firing by heating. However, it is preferable that the member has heat resistance to the extent that it is not damaged by the temperature at the time of joining.

Examples of the material constituting such a member to be joined include polyamide (PA), polyimide (PI), polyamideimide (PAI), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN). Examples thereof include polyester, polycarbonate (PC), polyether sulfone (PES), vinyl resin, fluororesin, liquid crystal polymer, ceramics, glass, metal and the like, and among them, a metal bonded member is preferable. The metal to be joined member is preferable because it has excellent heat resistance and has an excellent affinity with the bonding composition of the present invention in which the inorganic particles are metal.

Further, the member to be joined may have various shapes such as a plate shape or a strip shape, and may be rigid or flexible. The thickness of the base material can also be appropriately selected. For the purpose of improving adhesiveness or adhesion, or for other purposes, a member having a surface layer formed therein or a member having undergone a surface treatment such as a hydrophilization treatment may be used.

Various methods can be used in the step of applying the bonding composition to the member to be bonded. As described above, for example, dipping, screen printing, spraying, bar coating, spin coating, and inkjet. It can be appropriately selected and used from a type, a dispenser type, a pin transfer method, a brush coating method, a casting type, a flexographic type, a gravure type, a syringe type and the like.

The coating film after being applied as described above can be fired by heating to a temperature of, for example, 350 ° C. or lower within a range that does not damage the member to be joined, to obtain the bonded body of the present embodiment. In the present embodiment, as described above, since the bonding composition of the present embodiment is used, a bonding layer having excellent adhesion to the member to be bonded can be obtained, and strong bonding strength can be more reliably obtained. can get.

In the present embodiment, when the bonding composition contains a binder component, the binder component is also sintered from the viewpoint of improving the strength of the bonding layer and the bonding strength between the members to be bonded, but in some cases, the binder component is also sintered. May remove all the binder components by controlling the firing conditions, with the main purpose of adjusting the viscosity of the bonding composition for application to various printing methods.

The method for performing the firing is not particularly limited, and the temperature of the bonding composition coated or drawn on the member to be bonded using, for example, a conventionally known oven is, for example, 350 ° C. or lower. It can be joined by firing. The lower limit of the firing temperature is not always limited, and it is preferable that the temperature is such that the members to be bonded can be bonded to each other and the effect of the present invention is not impaired. Here, in the bonding composition after firing, it is preferable that the residual amount of the organic substance is small in terms of obtaining the bonding strength as high as possible, but a part of the organic substance remains as long as the effect of the present invention is not impaired. It doesn't matter if you do.

The bonding composition used in the bonding method of the present invention contains an organic substance, but unlike the conventional one using thermosetting such as an epoxy resin, the bonding strength after firing is increased by the action of the organic substance. Sufficient bonding strength can be obtained by fusing the fused conductive powder as described above. Therefore, even if the organic matter that remains after being placed in a usage environment higher than the joining temperature deteriorates, decomposes, or disappears after joining, there is no risk of the joining strength decreasing, and therefore the heat resistance is excellent. There is.

According to the bonding composition used in the bonding method of the present invention, it is possible to realize a bonding having a bonding layer that exhibits high conductivity even by firing by heating at a low temperature of, for example, about 150 to 250 ° C. Weak members to be joined can be joined to each other. Further, the firing time is not particularly limited, and any firing time may be used as long as it can be bonded according to the firing temperature.

In the present embodiment, in order to further enhance the adhesion between the bonded member and the bonded layer, the surface treatment of the bonded member may be performed. Examples of the surface treatment method include a method of performing a dry treatment such as corona treatment, plasma treatment, UV treatment, and electron beam treatment, and a method of providing a primer layer and a conductive paste receiving layer on a substrate in advance.

The atmosphere of the joining step is not particularly limited, and the bonding process can be performed in the atmosphere, under an inert gas atmosphere, under reduced pressure, or the like.

2. 2. Joined body The joined body of the present invention is a joined body in which one joined member and the other joined member are joined, and one joined member and the other joined member are metallized via a joining layer. The bonded layer contains metal particles and aluminum nitride particles, and the metal particles are a nuclear material for crystal-growing silver as a conductive material inside, and the metal particles are used as the nuclear material. Silver particles containing metal-based particles or ceramic-based particles, the average particle size of the aluminum nitride particles is 10 to 100 nm, and the content of the aluminum nitride particles in the bonding layer is 0.4 to 1.8% by mass. It is characterized by being.

Aluminum nitride particles having an average particle size of 10 to 100 nm are dispersed in the bonding layer formed mainly by sintering silver particles, and the content of the aluminum nitride particles is 0.4 to 1.8% by mass. Even if there is, the bonded layer has excellent thermal stability because uniform dispersion is achieved. Here, it is difficult to directly and quantitatively define the state in which the "aluminum nitride particles are uniformly dispersed", but for example, the porosity in the bonding layer is 10 after being left at a high temperature of 300 ° C. for 500 hours. It can be confirmed by not increasing more than%.

The average particle size of the aluminum nitride particles is preferably 15 to 80 nm, more preferably 20 to 60 nm. The content of the aluminum nitride particles is preferably 0.7 to 1.3% by mass, more preferably 0.9 to 1.1% by mass.

FIG. 1 schematically shows a mechanism in which aluminum nitride particles are uniformly dispersed and the bonding layer exhibits excellent thermal stability in the bonding composition and bonded body of the present invention. The conductive powder that occupies most of the bonding composition is microparticles having convex portions and concave portions on the surface, and fine aluminum nitride particles having a diameter of 10 to 100 nm are trapped in the concave portions of the conductive powder, so that uniform dispersion is extremely high. Achieved efficiently. In addition, while sintering (densification) proceeds mainly by contact between the convex portions of the conductive powder, contact between the main bodies of the conductive powder is suppressed by the dispersion of the aluminum nitride particles, so that mass transfer at high temperatures is suppressed. And good thermal stability can be obtained.

Further, metal-based particles or ceramic-based particles are mainly contained inside the silver particles forming the bonding layer, and these particles also contribute to the improvement of the thermal stability of the bonding layer. In particular, when ceramic particles are contained inside the silver particles, the effect is remarkable.

^{Further, in the bonded body, the ratio of the number of voids having an area of 0.2 μm 2} or less to the total number of voids is 90% or more with respect to the size of the voids measured by observing the cross section of the bonded layer. Is preferable. By suppressing the formation of coarse voids in the bonded layer, good mechanical properties and thermal stability are realized. Here, the ratio of the voids having each area can be easily obtained by, for example, image analysis of the cross-sectional SEM observation image.

Further, it is preferable that the bonding layer contains 0.001 to 0.1% by mass of spherical ceramic particles having an average particle size of 10 to 100 μm. Spherical ceramic particles having an average particle size of 10 to 100 μm function as spacers and can homogenize the thickness of the bonding layer. The average particle size of the spherical ceramic particles is preferably 20 to 90 μm, more preferably 30 to 80 μm. Further, the content of the spherical ceramic particles is more preferably 0.002 to 0.01% by mass. The spherical ceramic particles can be, for example, silica particles or the like.

Further, the porosity of the bonding layer is 10% or less, and it is preferable that the porosity does not increase to 10% or more by leaving at a high temperature of 300 ° C. for 500 hours. With a semiconductor chip that uses a semiconductor material that exhibits high performance under high temperature conditions of 300 ° C or higher, for example, because the bonding layer is dense and the porosity does not increase to 10% or more due to long-term holding at high temperatures. It can be suitably used as a bonded body bonded to and from a substrate.

Further, in the bonded body of the present invention, it is preferable that the shear strength of the bonded layer is 40 MPa or more, and the shear strength of the bonded layer after being left at a high temperature of 300 ° C. for 500 hours is 30 MPa or more. A semiconductor chip in which a semiconductor material that exhibits high performance under high temperature conditions of, for example, 300 ° C. or higher is used because the bonding layer has these shear strengths and maintains high shear strength even after being held at high temperature for a long time. It can be suitably used as a bonded body in which the substrate is bonded to the substrate.

Although the typical embodiments of the present invention have been described above, the present invention is not limited to these. For example, in the above embodiment, the case where only micro-sized silver particles are used as the conductive powder has been described, but for example, nanoparticles and the like can be appropriately added to the bonding composition for use.

Hereinafter, the joining method and the joined body of the present invention will be further described in Examples, but the present invention is not limited to these Examples.

<< Example 1 >>
Kaken Tech Co., Ltd. mixed 5.94 g of silver particle paste with 80% by mass of silver particles with fine protrusions, 0.06 g of aluminum nitride particles and an organic solvent, and 1 mass of aluminum nitride particles. A silver paste containing% was prepared in an amount of 6.0 g. Further, silica particles having a particle size of about 50 μm (High Presica TS manufactured by Ube Exsymo Co., Ltd.) were added to the silver paste so as to have a content of about 0.05% by mass to prepare a bonding composition.

FIG. 2 shows an SEM photograph of micro-sized silver particles, FIG. 3 shows an SEM photograph of aluminum nitride particles, and FIG. 4 shows an optical micrograph of silica particles. The average particle size of the silver particles is about 3 μm, and it can be confirmed that the silver particles have a unique shape including fine protrusions extending radially and a nuclear material for crystal growth in the central portion. The particle size of the aluminum nitride particles is 1 μm or less, and the average particle size is 60 nm. Further, the silica particles are spherical particles having a relatively uniform size.

FIG. 5 shows the shape of the bonding test piece made of oxygen-free copper used in the bonding test. The joining test piece has a disk shape, the smaller joining test piece has a diameter of 3 mm × a height of 2 mm, and the larger joining test piece has a diameter of 10 mm × a height of 5 mm. An Au layer of about 0.6 μm and a Ni layer of about 3 μm are formed on the surface of the bonding test piece in this order. Apply a certain amount of the bonding composition to the bonding surface of the larger disk test piece, and adjust the bonding test piece so that the bonding composition spreads over the entire bonding surface while stacking the smaller test pieces and lightly pressing them. did. Here, a metal mask having a thickness of 100 μm and a pore diameter of 5 mm was used to apply the bonding composition so that the thickness of the applied paste was uniform.

After that, a graphite sheet with a thickness of 1 mm (manufactured by Toyo Tanso Co., Ltd., PF-100) cut into a size of 5 mm × 5 mm was allowed to stand on the bonding test piece, and then a large-area pressure heating device (Ayumi Kogyo Co., Ltd.) was placed. Four joints were simultaneously produced using RB-100D) manufactured by the company. Here, the temperature rise was set to 1 ° C./sec, and all the steps involving heating were performed in a nitrogen atmosphere. Pressurization was started after reaching the maximum ultimate temperature (joining temperature) of 300 ° C., and the pressing force was 30 MPa. Then, it was held at 300 ° C. for 10 minutes, and the silver particles were sintered to obtain an implemented bonded body. After the completion of pressurization and heating, the bonded body was left in a nitrogen atmosphere for 30 minutes in the bonding device and cooled to room temperature.

The obtained bonded body was subjected to a high temperature standing test at 300 ° C. in the atmosphere using a precision thermostat (FH-360, manufactured by Toyo Engineering Works, Ltd.). The time of leaving at high temperature was 72 hours, 168 hours, 504 hours, and 1008 hours.

After leaving at high temperature, the resin-embedded bonded body is cut and polished, and a sample for cross-section observation is prepared by applying ion milling and coating treatment. Scanning electron microscope (SEM: Hitachi High-Technologies Corporation, SU-70) ) Was used to observe the cross section near the center of the joint layer.

In addition, the observation image was analyzed using image analysis software (ImageJ), and the porosity, average void size, number of voids, and void distribution of the bonding layer were calculated. Here, the void ratio is the area ratio of the voids existing in the bonding layer in the observation image, the average void size is the average area of the voids detected in the observation image, and the number of voids is the voids confirmed in the observation image. The number was taken. The observation image used for the image analysis had a width in the range of about 120 μm, and the joint layers of three different joints obtained under the same conditions were observed, and the most average one was taken as the observation result.

Further, in order to evaluate the joint strength of the joint body, a shear test was performed using a joint strength tester (manufactured by Reska Co., Ltd., STR-1001). The joints before and after the high temperature standing test were installed on the stage, a shear load was applied to the upper part of the joint at a shear rate of 1.0 mm / min and a shear height of 200 μm, and the maximum load at the time of fracture was divided by the area of the joint. The one was used as the joint strength. The joint strengths of the four joints were measured for each treatment condition, and the average thereof was taken as the joint strength under the treatment conditions.

<< Example 2 >>
Except that the content of the aluminum nitride particles in the bonding composition was changed in the range of 0.4 to 2.0% by mass in order to confirm the effect of the aluminum nitride particle content on the characteristics of the bonding composition. Obtained a bonding composition in the same manner as in Example 1. Further, a bonded body was prepared in the same manner as in Example 1, and the bonded strength was evaluated by a shear test.

<< Comparative Example 1 >>
A comparative bonded body was obtained in the same manner as in Example 1 except that aluminum nitride particles were not added to the bonding composition. In addition, a high temperature standing test and various evaluations were performed in the same manner as in Example 1.

<< Comparative Example 2 >>
A composition for comparative bonding was obtained in the same manner as in Example 1 except that silver nanoparticles were used instead of micro-sized silver particles having fine protrusions. In addition, a composition for comparative bonding to which aluminum nitride particles were not added was also produced.

Next, a joint was prepared in the same manner as in Example 1, and the joint strength of the obtained joint and the joint after high temperature exposure was evaluated by a shear test in the same manner as in Example 1. The high temperature exposure was carried out in the atmosphere at 300 ° C., and the exposure time was 168 h, 504 h and 100 8 h.

The cross-sectional SEM observation images of the embodiment joint obtained in Example 1 and the comparative joint obtained in Comparative Example 1 are shown in FIGS. 6 and 7, respectively. Table 1 shows the porosity, the average void size, and the number of voids in the joint layer of the implemented joint and the comparative joint.

In FIGS. 6, 7 and 1, the bonding layer of the implemented bonded body shows excellent thermal stability in addition to being dense, and both the porosity and the average void size are shown up to the high temperature standing time of 504 hours. Not increasing. On the other hand, in the comparative bonded body, a dense bonded layer is formed, but the porosity and the average void size are remarkably increased as the high temperature standing time is increased.

Histograms showing the area distribution of the voids formed in the junction layer of the embodiment junction obtained in Example 1 and the comparative junction obtained in Comparative Example 1 are shown in FIGS. 8 and 9, respectively. Each element of FIGS. 8 and 9 shows the ratio of the number of target voids to the total number of voids by size for each ^{void area of 0.2 μm 2.} Regarding the bonding layer of the implemented bonded body, ^{the ratio of the number of voids having an area of 0.2 μm 2} or less is 95% with respect to the total number of voids, which is 90% or more. On the other hand, regarding the bonding layer of the comparative bonded body, the ratio is 89%. Further, in the bonding layer of the implemented bonded body, ^{the ratio of the number of voids having an area of 0.2 μm 2} or less is maintained at 90% or more until the high temperature standing time is 504 hours, whereas the bonding of the comparative bonded body is maintained. In the layer, the ratio was significantly reduced by holding at high temperature, and it was less than 80% in 504 hours.

In FIG. 6, the dark-colored region confirmed at the upper and lower ends is the bonding test piece (copper), the white region in the center is the bonding layer, and the dark gray region shown in the bonding layer is aluminum nitride. Corresponds to the dispersed region of particles. The region shown in dark gray is subjected to SEM-EDS analysis, and it is confirmed that the aluminum nitride particles are present in the region. The aluminum nitride particles are uniformly dispersed in the bonding layer without agglomerating in a specific region, and as a result, the structural change of the bonding layer in the high temperature standing test is effectively suppressed.

Table 2 shows the joint strength (shear strength) of the embodiment joint obtained in Example 1 and the comparative joint obtained in Comparative Example 1. The unit of bonding strength is MPa. The implemented bonded body has a shear strength of 40 MPa or more, and maintains a shear strength of 30 MPa or more even after being left at a high temperature of 300 ° C. for 504 hours. On the other hand, the comparative bonded body also has a shear strength of 40 MPa or more, but the shear strength sharply decreases by being left at a high temperature, and becomes a value of about 10 MPa after being left at a high temperature for 504 hours.

FIG. 10 shows an SEM observation image of a cross section of the bonding layer of the embodiment bonded body obtained in Example 1 and an Al element mapping obtained by SEM-EDS. It can be seen that Al caused by the aluminum nitride particles is uniformly present in the entire area of the bonding layer and is mainly distributed among the particles of the micro silver particles.

Using FIB, an observation sample having a thickness of about 100 nm was prepared from the central portion of the junction layer of the embodiment junction obtained in Example 1, and TEM and STEM-EDS observations were performed. The TEM observation image and the element mapping corresponding to the TEM observation image are shown in FIG. The aluminum nitride particles can be confirmed by the distribution of the Al element, and it can be seen that the aluminum nitride particles enter between the micro silver particles and suppress the contact between the micro silver particles.

FIG. 12 shows the relationship between the shear strength of each of the embodiments obtained in Example 2 and the aluminum nitride particle content. FIG. 12 also shows the shear strength of the bonded body when the aluminum nitride particles are not added. When the amount of the aluminum nitride particles added is 1.8% by mass or less, a high shear strength of 25 MPa or more is obtained in all the bonded bodies. On the other hand, when the amount of the aluminum nitride particles added increases to 2.0% by mass, the shear strength decreases. Further, each bonding composition having an aluminum nitride particle content of 1.8% by mass or less had good coating performance. From these results, it can be seen that by setting the addition amount of the aluminum nitride particles to 1.8% by mass or less, high shear strength of the bonded body and good coating performance of the bonding composition can be ensured.

FIG. 13 shows the bonding strength of the bonded body obtained in Comparative Example 2 and the bonded body after high temperature exposure. When silver nanoparticles are used as the conductive material, the bonding strength is lowered by adding the aluminum nitride particles, and the shear strength is lower than that when the aluminum nitride particles are added even after high temperature exposure. There is. Further, as shown in Table 2, in the embodiment bonded body obtained in Example 1, the decrease in the average shear strength due to leaving at a high temperature of 300 ° C. for 504 hours was only about 30%, whereas in Comparative Example 2. In the bonded body obtained in 1), the shear strength is reduced by about 65%. From the above results, high bonding strength and high temperature stability cannot be obtained only by adding aluminum nitride particles, and it is necessary to use microparticles having an appropriate shape as a conductive material and uniformly disperse the aluminum nitride particles. It turns out that there is.

Claims (9)

It is provided with a convex portion extending radially and a concave portion in the gap between the convex portions, and is a nuclear material for growing silver as a conductive material inside, and is a metal-based material as the nuclear material. A conductive powder containing silver containing particles or ceramic particles and having an average particle size of the nuclear material of 1 to 10 μm.
Using a bonding composition containing aluminum nitride particles having an average particle size of 10 to 100 nm,
Including a step of interposing the bonding composition between two members to be joined, and then heating and pressurizing the members to 150 to 350 ° C.
A joining method characterized by. The content of the aluminum nitride particles in the bonding composition shall be 0.4 to 1.8% by mass.
The joining method according to claim 1. The shape of the convex portion is at least one shape selected from the group consisting of needle-shaped, rod-shaped, and petal-shaped.
The joining method according to claim 1 or 2. The bonding composition contains 0.001 to 0.1% by mass of spherical ceramic particles having an average particle size of 10 to 100 μm.
The joining method according to any one of claims 1 to 3. A bonded body in which one member to be joined and the other member to be joined are joined.
The one member to be joined and the other member to be joined are metallurgically joined via a joining layer.
The bonding layer contains metal particles and aluminum nitride particles.
The metal particles are nuclear materials for growing silver as a conductive material inside, and are silver particles containing metal particles or ceramic particles as the nuclear material.
The average particle size of the aluminum nitride particles is 10 to 100 nm, and the average particle size is 10 to 100 nm.
The content of the aluminum nitride particles in the bonding layer is 0.4 to 1.8% by mass.
A joint characterized by. With respect to the size of the voids measured by cross-sectional observation of the junction layer
The ratio of the number of voids whose area is 0.2 μm ² or less is 90% or more with respect to all the number of voids.
5. The joined body according to claim 5. The bonding layer contains 0.001 to 0.1% by mass of spherical ceramic particles having an average particle size of 10 to 100 μm.
The joined body according to claim 5 or 6. The porosity of the bonding layer is 10% or less, and the porosity does not increase to 10% or more by being left at a high temperature of 300 ° C. for 500 hours.
The bonded body according to any one of claims 5 to 7. The shear strength of the bonded layer is 40 MPa or more, and the shear strength of the bonded layer after being left at a high temperature of 300 ° C. for 500 hours is 30 MPa or more.
The bonded body according to any one of claims 5 to 8.

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