JP2024008530A - Joining method, electronic apparatus production method and electronic apparatus - Google Patents

Abstract

To provide a joining method which can secure joining strength even when a joining area at a plurality of joining parts made of metal is large.SOLUTION: A method for joining a metallic first joining part of a first member having the first joining part and a metallic second joining part of a second member having the second joining part comprises: a first step of applying metallic paste obtained by dispersing metal particles into an organic solvent into a film shape to form a paste film; a second step of heating the paste film to a temperature less than a sintering start temperature of the metal particles and vaporizing the organic solvent to form a dry film of the paste film; a third step of softening a part of the dry film with a softener which can infiltrate into the dry film; and a fourth step of executing heating to the sintering start temperature or higher in a state in which the second joining part is in contact with the softened dry film and sintering the metal particles in the dry film to join the first joining part and the second joining part.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a bonding method, an electronic device manufacturing method, and an electronic device.

BACKGROUND ART Conventionally, for example, as shown in Patent Document 1 (Japanese Patent No. 5301385), a method of joining two members using a joining material mainly containing metal nanoparticles has been known. In such known bonding methods, a bonding material containing metal fine particles with an average diameter of 10 nm to 10 μm as a main component is interposed between the bonded portions of two members and is heated and fired. , the two members are joined.

However, when the bonding area of two members is large, if a bonding material such as that shown in Patent Document 1 is used, the organic protective film of the metal nanoparticles or the organic solvent for making the metal nanoparticles into a paste will evaporate. This is difficult near the center between the joints. As a result, carbide remains between the joints (in the joint layer). Therefore, there is a problem in that the strength, electrical characteristics, thermal characteristics, etc. of the bonded portion deteriorate. That is, the conventional bonding materials as shown in Patent Document 1 are not suitable for bonding with a large bonding area compared to solder bonding, brazing, and the like.

On the other hand, for example, in Patent Document 2 (Japanese Patent No. 5012239), in addition to the usual bonding method, after applying a bonding material to the first bonding portion of the first member, the film of the bonding material is dried by heating. A step of volatilizing the organic solvent contained in the bonding material is performed. After that, a bonding material is further applied on the dried bonding material film (dried film), a second member is placed, and the first member and second member are bonded by heating and firing.

Patent No. 5301385 Patent No. 5012239

In the bonding method described in Patent Document 2, multiple types of bonding layers having different porosity are formed in the bonding portion. As a result of bonding large-area chips together using the method shown in Patent Document 2, the present inventors discovered that the shrinkage rates of the bonding layers with different porosity were different, resulting in delamination between the bonding layers. It has been found that defects are likely to occur.

In view of the above-mentioned problems, an object of the present disclosure is to provide a joining method that can ensure joint strength even when the joint area is large in joining a plurality of joint parts made of metal.

The joining method of the present disclosure joins the first joining part of a first member having a first joining part made of metal and the second joining part of a second member having a second joining part made of metal. It's a method.
The joining method of the present disclosure includes:
a first step of forming a paste film made of the metal paste by applying a metal paste made of metal particles dispersed in an organic solvent on the surface of the first joint part;
a second step of heating the paste film to a temperature lower than the sintering start temperature of the metal particles to volatilize part or all of the organic solvent and drying the paste film to form a dry film; ,
a third step of softening a portion of the dry film including its surface with a softening agent that can permeate the dry film;
Sintering the metal particles in the dry film by heating to a temperature equal to or higher than the sintering start temperature of the metal particles while the second joint portion is in contact with the dry film softened in the third step. and a fourth step of joining the first joint part and the second joint part.
In the fourth step, all of the softening agent is volatilized or decomposed.

According to the present disclosure, it is possible to provide a bonding method that can ensure bonding strength even when the bonding area is large in bonding a plurality of bonding portions made of metal.

Note that in the conventional bonding method, as shown in FIGS. 1 and 2, after the second member 20 is placed, the paste film 30 (metal paste film) is heated and dried. In this case, since the solvent evaporates along the path shown by the arrow in FIG. 2(d), organic components may remain in the center of the dried film or voids may be generated in the sintered film 32 due to the volatile gas.

In contrast, in the bonding method of the present disclosure, as shown in FIGS. 3 and 4, in the second step, the paste film 30 is dried before the second member 20 is placed, so that the organic solvent is evaporated. The sintering progresses sufficiently even in the center of the paste film 30, and a more uniform sintered film 32 is formed. Thereby, even if the bonding area is large, bonding strength can be ensured. Furthermore, drying time can be shortened.

Also, by sintering, the dry film 31 is partially softened from its surface 301a before placing the second member so that the joint portion 201 of the second member comes into close contact with the dry film 31 dried in the second step. Execute the third step to As a result, a plurality of layers of sintered film having different porosity as described in Patent Document 2 is not formed, so that the strength of the sintered film 32 (joining member) can be improved.

FIG. 2 is a flow diagram showing steps of a conventional bonding method. FIG. 3 is a schematic cross-sectional view showing the structure of members in each step of a conventional joining method. FIG. 3 is a flow diagram showing the steps of the joining method according to the first embodiment. 3 is a schematic cross-sectional view showing the configuration of members in each step of the joining method of the first embodiment. FIG. FIG. 3 is a schematic diagram showing the configuration of a conductive metal paste material in the bonding method of Embodiment 1. FIG. FIG. 3 is an explanatory diagram of a mechanism for softening the surface of a dried film in the bonding method of Embodiment 1. FIG. 3 is a diagram showing the softener concentration and the hardness distribution of the dried film after surface softening of the dried film in the bonding method of Embodiment 1. 3 is a diagram showing a porosity profile of a joined body (sintered body) in Embodiment 1. FIG. 7 is a flow diagram showing steps of a joining method according to a second embodiment. FIG. FIG. 7 is a schematic cross-sectional view showing the structure of members in each step of the joining method according to the second embodiment. FIG. 3 is an explanatory diagram of a mechanism for softening a dry film in the bonding method of the embodiment.

Embodiments of the present disclosure will be described below. In the drawings, dimensional relationships such as length, width, thickness, depth, etc. have been appropriately changed for clarity and simplification of the drawings, and do not represent actual dimensional relationships.

The joining method of the present disclosure joins the first joining part of a first member having a first joining part made of metal and the second joining part of a second member having a second joining part made of metal. It's a method.
The joining method of the present disclosure includes:
Forming a paste film made of the metal paste by applying a metal paste made of metal particles (metal nanoparticles, metal microparticles, etc.) dispersed in an organic solvent to the surface of the first bonding part. The first step is to
Heating the paste film to a temperature (first temperature) lower than the sintering start temperature of the metal particles to volatilize part or all of the organic solvent and drying the paste film to form a dry film. , a second step, and
a third step of softening a portion of the dry film including its surface with a softening agent that can permeate the dry film;
With the second joint portion in contact with the dry film softened in the third step, the metal particles in the dry film are heated to a temperature (second temperature) equal to or higher than the sintering start temperature of the metal particles. and a fourth step of joining the first joint part and the second joint part (using the dry film as a joining member (sintered film)) by sintering.
In the fourth step, all of the softening agent is volatilized or decomposed.

Here, as shown in FIG. 2, the conventional joining method shown in FIG.
A step of applying a metal paste made by dispersing metal particles (metal powder) in an organic solvent to the first joint portion 101 made of metal in the first member 10 to form a paste film 30 (metal paste film). coating) and
arranging the second member 20 so that the second joint portion 201 made of metal in the second member 20 comes into contact with the surface 30a of the paste film 30 to form an assembly 401 (second member arrangement);
The assembled product 401 is heated, the organic solvent of the paste film 30 is volatilized or decomposed, the metal particles are sintered, a sintered film 32 is formed, and the first joint part 101 and the second joint part 201 are joined. A step (heating and sintering) of obtaining a body (sintered product) 402 is included.

In the bonding method of the present disclosure, the conventional bonding method described above is changed to, for example, the bonding method of Embodiment 1 shown in FIG. 3 or the bonding method of Embodiment 2 shown in FIG. 4.

Embodiment 1.
Embodiment 1 of the present disclosure will be described below with reference to the drawings.

FIG. 3 is a flowchart showing the steps of the joining method according to the first embodiment. FIG. 4 is a schematic cross-sectional view showing the configuration of members in each step of the joining method according to the first embodiment.

In the first embodiment, in the third step, a softening agent is applied to the surface of the dry film to soften a portion including the surface of the dry film. Each step will be explained below.

The bonding method of the first embodiment is a method of bonding the first bonding portion 101 of the first member 10 and the second bonding portion 201 of the second member 20 via a bonding member containing a conductive medium such as metal. be.

The material of (the main body portion of) the first member 10 is not particularly limited. The first member 10 (the main body thereof) may be, for example, a substrate made of a single metal such as copper or aluminum, or may be a substrate made of ceramic, resin, or the like as a base.

The first joint portion 101 of the first member 10 is made of metal. The material of the first joint portion 101 may be the same material of (the main body portion of) the first member 10. The first bonding portion 101 may be a portion made of metal such as copper, aluminum, silver, or gold formed on a substrate such as ceramic by a method such as plating or bonding.

The second member 20 may be a conductive element made of a single metal such as copper or aluminum, or a semiconductor element.

The second joint portion 201 of the second member 20 is made of metal. The material of the second joint portion 201 may be the same as the material of the second member 20. The second joint portion 201 may be a portion made of metal such as copper, aluminum, silver, or gold formed by plating on the ceramic element.

For example, as shown in FIGS. 3 and 4, the joining method of this embodiment
A first step of applying a metal paste made of metal particles dispersed in an organic solvent to the first joint 101 of the first member 10 to form a paste film 30 to form an intermediate assembly 411;
a second step of heating the intermediate assembly 411 to volatilize or decompose some or all of the organic solvent of the paste film 30 into a dry film 31;
A third step of applying a liquid softener 50 to the surface 301a of the dry film 31 to partially soften the dry film 31 from the surface 301a;
arranging the second member 20 so that the second joint portion 201 made of metal in the second member 20 comes into contact with the surface 301a of the dry film 31 to form an assembly 412;
The assembly 412 is heated to volatilize or decompose the organic solvent of the dry film 31 and the softener 50 applied in the third step, and sinter the metal particles to form the sintered film 32. The method includes a fourth step of joining the first joint part 101 and the second joint part 201 to form a joined body 402.

In the first step, the metal paste applied to the first joint portion of the first member 10 is a low-temperature sintering type conductive paste that utilizes a low-temperature sintering phenomenon caused by the quantum size effect of metal particles and high surface activity.

In this embodiment, the metal paste includes metal particles 331 and a volatile organic solvent 332, as shown in FIG.

The metal particles 331 include, for example, metal nanoparticles 3311 (for example, metal particles having a diameter (particle size) of 500 nm or less) and metal micron particles 3312 having a larger diameter (particle size) than the metal nanoparticles 3311. included. Metal nanoparticles include, for example, silver nanoparticles.

The metal particles preferably have a particle size within the range of 0.01 μm to 10 μm and contain gold, silver, copper, or nickel. The metal particles may have a mode diameter (particle diameter mode) within a range of 0.1 μm to 1 μm.

The metal particles preferably have a particle size within the range of 0.01 μm to 10 μm and contain a metal compound (silver oxide, copper oxide, etc.) that decomposes upon heating. The metal compound may include, for example, silver oxide or a metal compound that can be chemically decomposed by heating to produce nanosilver particles. The metal compound may also include silver(I) 2-ethylhexanoate (CAS RN: 26077-31-6) or a metal organic compound that can be decomposed by heating to produce nanosilver particles. The metal particles may have a mode diameter (particle diameter mode) within a range of 0.1 μm to 1 μm.

Note that the metal nanoparticles 3311 preferably have a protective group 3311a on their surfaces. The protective group 3311a suppresses the integration of the metal nanoparticles and surrounding metal particles by sintering. That is, the protective group 3311a is decomposed by heating, exposes the surface of the metal nanoparticle 3311, and prevents the metal nanoparticle 3311 and surrounding metal particles from being integrated by sintering.

The protective group 3311a of the metal nanoparticle 3311 is preferably decomposed by heating at a temperature within the range of 100°C to 200°C. Protecting group 3311a may be decomposed by heating at a temperature within the range of 80°C to 250°C.

Preferably, the metal micron particles 3312 are sintered by heating at a temperature within the range of 250°C to 300°C. The metal micron particles 3312 may be sinterable by heating at a temperature within the range of 200°C to 400°C.

Note that the material of the metal particles 331 may be, for example, any pure metal such as gold, silver, copper, or nickel. Moreover, as the material of the metal particles 331, a metal compound that can obtain the same effect may be used instead of the above-mentioned pure metal.

The volatile organic solvent 332 has the function of maintaining the metal particles 331 in an independently dispersed state and adjusting the viscosity of the metal paste at room temperature (fluidity during application). Note that, in order to adjust the solvent volatility, sinterability, etc. of the metal paste, the organic solvent 332 may use a plurality of types of organic solvents, and may also contain a sintering accelerator.

In this embodiment, the thickness of the metal paste film 30 formed in the first step is preferably 100 μm to 200 μm, and may be, for example, 10 μm to 300 μm.

In order to form the surface 30a of the paste film 30 more flatly, it is preferable to use a method of printing with a squeegee through a metal mask or a scream mask as a method of applying the metal paste in the first step. Note that other methods that can form the flat surface 30a, such as a method using a dispenser or the like, may be used. The flatness of the surface 30a is preferably ±10% of the average thickness of the paste film 30.

In the second step, the paste film 30 applied to the first joint portion of the first member 10 in the first step is dried by heating to form a dry film 31. The drying temperature is below the decomposition temperature of the protective group 3311a of the metal nanoparticles 3311 of the paste 3, and at this drying temperature, part or all of the organic solvent 332 is volatilized. By drying the organic solvent 332, the dried film 31 hardens.

Note that the drying heating method may be heat transfer from a heat plate or hot air. Other heating methods that can dry the paste film 30 uniformly may also be used. Further, the atmospheric environment for heating may be normally atmospheric. Further, in order to dry the organic solvent 332 of the paste film 30 more quickly, a reduced pressure or vacuum environment may be used. Further, in order to prevent the surface of the first joint portion 101 of the first member 10 from oxidizing, an inert gas atmosphere such as nitrogen gas may be used.

In the dry film 31 that has been dried in the second step, a softener 50 is used to arrange the second joint part of the second member on the surface 301a of the dry film 31 with good adhesion. Part of the film 31 is softened starting from the surface 301a.

The softener 50 may be made of one type of organic liquid or may contain multiple types of organic substances.

The softener 50 contains, for example, 70% by mass or more of a volatile organic solvent and less than 30% by mass of at least one of metal nanoparticles, metal compounds, and sintering accelerators (as a reinforcing agent). Note that as long as the softener 50 is liquid, the content of the organic solvent in the softener 50 may be less than 70% by mass, and the content of the reinforcing agent may be 30% by mass or more and 95% by mass or less. You can.

The reinforcing agent of the softener 50 will be explained in detail.

When adding metal nanoparticles as a reinforcing agent, the same metal nanoparticles as the metal nanoparticles 3311 contained in the metal paste are preferably used.

Further, when adding a metal compound as a reinforcing agent, it is desirable to use a compound of the same metal as the metal particles contained in the metal paste, and it is preferable that the metal compound is decomposed by heating to produce nanoparticles of the metal. For example, if the metal is silver, silver oxide may be added to the softener 50, silver nitrate may be added, or silver (I) 2-ethylhexanoate (CAS RN: 26077-31-6) may be added. May be added.

In addition, when adding a sintering accelerator as a reinforcing agent in addition to metals and metal compounds, the sintering accelerator may be oxalic acid or an amine type that combines with silver ions of silver or silver compounds to form a metal complex. It may contain an organic compound or an acidic organic compound. That is, the sintering accelerator may be an organic compound that reacts with the protective group 3311a of the metal nanoparticles 3311 contained in the metal paste to expose the surface of the metal nanoparticles when heated; It may be an amine-based or acid-based organic compound that combines with silver ions to form a metal complex.

The softener 50 includes, for example, an organic solvent and a sintering accelerator,
The content of the sintering accelerator in the softener is 30% by mass or more and 95% by mass or less.

In the third step, a softening agent 50 is applied to the surface 301a of the dry film 31 to soften a part of the surface of the dry film 31. In this embodiment, the liquid softener 50 may be sprayed or spin coated over the entire surface 301a of the dry film 31. Alternatively, a method may be employed in which the softener is applied uniformly and in a small amount to the dry film 31.

The amount of softener 50 applied is preferably 2% to 4% by mass of the amount of paste film 30 applied in the first step, and 1% by mass to 4% by mass of the amount of paste film 30 applied in the first step. It may be 5% by mass.

FIG. 6 is an explanatory diagram of the mechanism of partially softening the dry film 31 by applying the softener 50, and is a cross-sectional view of the central part of the dry film 31 in which the organic solvent 332 has been partially dried.

Since the dried film 31 was dried in the second step at a temperature lower than the temperature at which the protective group of the metal nanoparticles 3311 decomposes the organic solvent 332, the metal particles are not sintered. When the softener 50 is applied to the dry film 31 in this state, the softener permeates into the dry film 31 from the surface 301a. As a result, a concentration gradient of the softening agent is generated from the surface 301a of the dry film 31 shown in FIG. 7, and a portion of the dry film 31 including the surface 301a is softened.

Next, the second member 20 is placed on the surface 301a of the dry film 31a softened in the third step to form an assembly 412.

Next, if necessary, pressure is applied to the assembly 412 from the upper surface 202 side of the second member 20 so that the second joint 201 of the second member 20 and the surface 301a of the dry film 31a are brought into close contact. . The pressure is preferably in the range of 2 MPa to 5 MPa, and may be in the range of 0.1 MPa to 10 MPa.

Note that during pressurization, the temperature of the assembly 412 may be room temperature, or the assembly 412 may be heated at a temperature lower than the temperature at which the protective group 3311a of the metal nanoparticle 3311 decomposes.

After arranging the second member, the assembly 412 is heated in a fourth step to sinter the metal particles 331, thereby forming a sintered film 32 and connecting the first joint 101 and the second joint 201. A joined body 402 is formed by joining.

In the fourth step, the assembly 412 is heated at a temperature below 100° C. for 2 to 5 minutes, thereby removing the undried organic solvent 332 (if any remains) and the It is preferable to dry the organic components contained in the softener 50 applied in the three steps. Alternatively, similar drying may be performed by uniformly raising the temperature from room temperature to a temperature at which the protective group 3311a of the metal nanoparticles 3311 (eg, silver nanoparticles) decomposes over a period of 5 to 15 minutes.

Further, after the drying step of the undried organic solvent 332 and the organic components of the softener 50 is completed, the temperature is raised to within the range of 250° C. to 300° C. and held for 5 to 25 minutes to sinter the metal particles 331. It is preferable to let Further, the sintering temperature may be 200° C. to 400° C., and the sintering time may be 1 to 120 min.

Note that by heating in the fourth step (baking step), all of the organic components (and organic solvent 332) in the softener 50 contained in the paste film 30 are volatilized or decomposed. This heating is preferably performed by heat transfer using a heat plate or by hot air. Other methods that can uniformly heat the paste film 30 may also be used. Further, the atmospheric environment for heating may normally be an atmospheric environment. Further, in order to more quickly dry the organic solvent 332 contained in the paste film 30 and the organic components in the softener 50, a reduced pressure or vacuum environment may be used. Further, in order to prevent oxidation of the surface of the first joint portion 101 of the first member 10 and the surface of the second joint portion 201 of the second member 20, an inert gas atmosphere such as nitrogen gas may be used.

By the above joining method, the joined body 402 according to this embodiment can be manufactured. FIG. 8 shows a porosity profile in the cross-sectional direction of the sintered film 32 (joint member) of the joined body 402, depending on the composition of the softener 50 applied in the third step. Since the softener 50 contains a volatile organic solvent, the organic solvent evaporates during heating in the fourth step (firing step), and gas is generated near the second joint of the second member. The porosity near the second joint of the two members is greater than the porosity near the first joint of the first member through which the softener 50 cannot completely penetrate. On the other hand, by adding a reinforcing agent to the softener, the porosity near the second joint of the second member can be reduced.

Embodiment 2.
Embodiment 2 of the present disclosure will be described below with reference to the drawings.

FIG. 9 is a flowchart showing the steps of the joining method according to the second embodiment. FIG. 10 is a schematic cross-sectional view showing the configuration of members in each step of the joining method according to the second embodiment.

In the bonding method of the second embodiment, the steps up to the second step and the steps after the fourth step are the same as the bonding method of the first embodiment, so a duplicate explanation will be omitted here.

In the second embodiment, in the third step, the second member 20 with the softener 50 applied to the second joint part 201 is arranged so that the dry film 31 and the second joint part 201 are in contact with each other. , a portion including the surface of the dry film 31 is softened.

In this embodiment, in order to arrange the second joint part of the second member with good adhesion on the surface 301a of the dry film 31, which is the paste film 30 dried in the second step, the second joint part of the second member 20 is A softening agent 50 is applied to the portion 201 (FIG. 10(d)). The softener 50 is similar to the softener 50 described in Embodiment 1.

In the third step of this embodiment, the second member coated with a softener is arranged so that the second joint 201 of the second member 20 is in contact with the surface 301a of the dry film 31 (FIG. 10(e) )).

Here, since the dried film 31 is dried in the second step at a temperature lower than the temperature at which the protective groups of the metal nanoparticles 3311 decompose the organic solvent 332, the metal particles 331 are not sintered. In this state, as shown in FIG. 11, the softener 50 applied to the second bonded portion permeates into the dry film 31 from the surface 301a, and a portion of the dry film 31 including the surface 301a is softened.

Note that the holding time before the next pressurization is preferably 0.5 to 1.0 seconds so that the surface 301a of the dry film 31 is sufficiently softened. When the composition of the softener 50 changes its permeability into the dry film 31, the holding time may be 0.01 to 5.0 seconds, or may be 5 seconds or more.

Next, pressure is applied to the assembly 412 from the upper surface 202 side of the second member 20 in order to bring the second joint portion 201 of the second member into close contact with the surface 301a of the dry film 31a. The pressurization is preferably in the range of 2 MPa to 5 MPa, and may be in the range of 0.1 MPa to 10 MPa. Furthermore, when pressurizing, the temperature of the assembly 412 may be room temperature. Assembly 412 may be heated at a temperature below the temperature at which protective groups 3311a of metal nanoparticles 3311 decompose.

Furthermore, in this embodiment, compared to Embodiment 1, the softening agent 50 is applied to the second joint portion of the second member 20, and the holding time before pressurization is controlled in the third step. The degree of softening of the surface 301a of the dry film 31 can be controlled with higher accuracy.

By the joining method of this embodiment, the joined body 402 can be produced with the same effect as in the first embodiment described above.

<Manufacturing method of electronic equipment>
The present disclosure provides the first joint portion of a first member having a first joint portion made of metal and the second joint portion of a second member having a second joint portion made of metal using the above-described joining method. It also relates to a method of manufacturing an electronic device, which includes bonding.

<Electronic equipment>
The present disclosure includes a first member having a first joint made of metal, and a second member having a second joint made of metal,
The first joint part and the second joint part are joined via a joining member (sintered member) containing metal particles,
The present invention also relates to an electronic device in which the proportion of holes in the bonding member gradually changes in the stacking direction of the first bonding portion and the second bonding portion.

The embodiments disclosed this time should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and it is intended that all changes within the meaning and range equivalent to the claims are included.

Hereinafter, various aspects of the present disclosure will be collectively described as supplementary notes.

(1) A joining method of joining the first joining part of a first member having a first joining part made of metal and the second joining part of a second member having a second joining part made of metal. There it is,
a first step of forming a paste film made of the metal paste by applying a metal paste made of metal particles dispersed in an organic solvent on the surface of the first joint part;
a second step of heating the paste film at a temperature lower than the sintering start temperature of the metal particles to volatilize part or all of the organic solvent and drying the paste film to form a dry film; ,
a third step of softening a portion of the dry film including its surface with a softening agent that can permeate the dry film;
Sintering the metal particles in the dry film by heating to a temperature equal to or higher than the sintering start temperature of the metal particles while the second joint portion is in contact with the dry film softened in the third step. a fourth step of joining the first joint part and the second joint part,
In the fourth step, all of the softening agent is volatilized or decomposed.

(2) The joining method according to (1), wherein in the third step, a part of the dry film including the surface is softened by applying the softening agent to the surface of the dry film.

(3) In the third step, the second member having the softener applied to the second joint part is arranged so that the dry film and the second joint part are in contact with each other, so that the dry film is The joining method according to (1), wherein a part including the surface of the bonding method is softened.

(4) The joining method according to any one of (1) to (3), wherein the metal particles have a particle size within a range of 0.01 μm to 10 μm and include gold, silver, copper, or nickel. .

(5) The joining method according to any one of (1) to (3), wherein the metal particles have a particle size within a range of 0.01 μm to 10 μm and include a metal compound that decomposes upon heating.

(6) The joining method according to any one of (1) to (4), wherein the softener is made of one type of organic liquid.

(7) The joining method according to any one of (1) to (4), wherein the softener contains multiple types of organic substances.

(8) The joining method according to (7), wherein the softener contains 70% by mass or more of an organic solvent and less than 30% by mass of at least one of metal nanoparticles, metal compounds, and sintering accelerators.

(9) The joining method according to (8), wherein the metal nanoparticles include silver nanoparticles.

(10) The joining method according to (8), wherein the metal compound includes silver oxide or a metal compound that can be chemically decomposed by heating to produce nanosilver particles.

(11) The joining method according to (8), wherein the metal compound includes silver (I) 2-ethylhexanoate or a metal organic compound that can be decomposed by heating to produce nanosilver particles.

(12) The bonding according to (8), wherein the sintering accelerator includes oxalic acid, or an amine-based organic compound or acid-based organic compound that combines with silver or silver ions of a silver compound to form a metal complex. Method.

(13) The softener includes an organic solvent and a sintering accelerator,
The joining method according to (7), wherein the content of the sintering accelerator in the softener is 30% by mass or more and 95% by mass or less.

(14) The bonding according to (13), wherein the sintering accelerator includes oxalic acid, or an amine-based organic compound or acid-based organic compound that combines with silver or silver ions of a silver compound to form a metal complex. Method.

(15) The first joint part of the first member having the first joint part made of metal and the second joint part made of metal are bonded using the joining method according to any one of (1) to (14). and the second joint portion of a second member having the second member.

(16) A first member having a first joint made of metal; and a second member having a second joint made of metal;
The first joint part and the second joint part are joined via a joining member containing metal particles,
An electronic device, wherein in the bonding member, a proportion of pores gradually changes in a stacking direction of the first bonding portion and the second bonding portion.

DESCRIPTION OF SYMBOLS 10 1st member, 101 1st joint part, 20 2nd member, 201 2nd joint part, 202 upper surface of 2nd member, 30 paste film (metal paste film), 30a surface, 31 dry film, 31a softened dry Film, 301a Surface, 32 Sintered film, 331 Metal particles, 3311 Metal nanoparticles, 3311a Protective group, 3312 Metal micron particles, 332 Organic solvent, 401 Assembly (before sintering), 402 Joined body, 411 Intermediate assembly, 412 Assembly (before sintering), 50 Softener.

Claims (16)

A joining method of joining the first joining part of a first member having a first joining part made of metal and the second joining part of a second member having a second joining part made of metal,
a first step of forming a paste film made of the metal paste by applying a metal paste made of metal particles dispersed in an organic solvent on the surface of the first joint part;
a second step of heating the paste film at a temperature lower than the sintering start temperature of the metal particles to volatilize part or all of the organic solvent and drying the paste film to form a dry film; ,
a third step of softening a portion of the dry film including its surface with a softening agent that can permeate the dry film;
Sintering the metal particles in the dry film by heating to a temperature equal to or higher than the sintering start temperature of the metal particles while the second joint portion is in contact with the dry film softened in the third step. a fourth step of joining the first joint part and the second joint part,
In the fourth step, all of the softening agent is volatilized or decomposed. 2. The bonding method according to claim 1, wherein in the third step, a part of the dry film including the surface is softened by applying the softening agent to the surface of the dry film. In the third step, the surface of the dry film is softened by arranging the second member with the softener applied to the second joint so that the dry film and the second joint are in contact with each other. The joining method according to claim 1, further comprising softening a portion thereof. The joining method according to claim 1, wherein the metal particles have a particle size within a range of 0.01 μm to 10 μm and include gold, silver, copper, or nickel. The joining method according to claim 1, wherein the metal particles have a particle size within a range of 0.01 μm to 10 μm and include a metal compound that is decomposed by heating. 2. The bonding method according to claim 1, wherein the softener comprises one type of organic liquid. The joining method according to claim 1, wherein the softener contains multiple types of organic substances. The joining method according to claim 6 or 7, wherein the softener contains 70% by mass or more of an organic solvent and less than 30% by mass of at least one of metal nanoparticles, a metal compound, and a sintering accelerator. The joining method according to claim 8, wherein the metal nanoparticles include silver nanoparticles. 9. The bonding method according to claim 8, wherein the metal compound includes silver oxide or a metal compound that can be chemically decomposed by heating to produce nanosilver particles. 9. The bonding method according to claim 8, wherein the metal compound includes silver (I) 2-ethylhexanoate or a metal organic compound that can be decomposed by heating to produce nanosilver particles. 9. The joining method according to claim 8, wherein the sintering accelerator contains oxalic acid, or an amine-based organic compound or acid-based organic compound that combines with silver or silver ions of a silver compound to form a metal complex. The softener includes an organic solvent and a sintering accelerator,
The joining method according to claim 7, wherein the content of the sintering accelerator in the softener is 30% by mass or more and 95% by mass or less. 14. The joining method according to claim 13, wherein the sintering accelerator includes oxalic acid, or an amine-based organic compound or acid-based organic compound that combines with silver or silver ions of a silver compound to form a metal complex. Using the joining method according to claim 1, the first joining part of the first member having the first joining part made of metal and the second joining part of the second member having the second joining part made of metal. A method of manufacturing an electronic device, the method comprising joining. A first member having a first joint made of metal, and a second member having a second joint made of metal,
The first joint part and the second joint part are joined via a joining member containing metal particles,
An electronic device, wherein in the bonding member, a proportion of pores gradually changes in a stacking direction of the first bonding portion and the second bonding portion.

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