JP2018003088A - Joint material, method of manufacturing joint material, and conjugate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a bonding material using copper nanoparticles as a raw material, which has a high bonding force and uses only copper as a raw material. SOLUTION: This is a plate-shaped or sheet-shaped bonding material containing fine particles containing copper as a main component and having an average particle diameter of 300 nm or less, in which the fine particles are in close contact with each other, and the porosity of the bonding material is less than 0.30 and the thickness is high. It is a bonding material with a porosity of 200 μm or less, and as a manufacturing method, fine particles containing copper as a main component having an average particle diameter of 300 nm or less are pressed to 0.5 GPa or more at room temperature in an air atmosphere to form a plate or a sheet. A bonding material with a process of forming in. Preferably, a bonding material having a shear strength of 30 MPa or more. [Selection diagram] None

Description

  The present invention relates to a bonding material, a method for manufacturing a bonding material, and a bonded body.

  Conventionally, solder materials have been widely used as bonding materials for electronic components. However, the solder material has a problem of poor heat resistance. Therefore, for example, in a power device using an SiC element expected to have a high temperature of 150 ° C. or higher (hereinafter referred to as “SiC power device”), it is difficult to use a solder material as a bonding material.

  Therefore, as a bonding material for SiC power devices, a bonding material containing heat-resistant silver or a silver alloy as a main component has been used (Patent Document 1). However, the bonding material containing silver or a silver alloy as a main component has physical properties such as the occurrence of ion migration.

  Therefore, as an alternative to a bonding material containing silver or a silver alloy as a main component, a bonding material containing copper as a main component has been studied. Patent Document 2 discloses a bonding material using paste-like copper nanoparticles as a raw material.

  However, an organic solvent is usually used for the paste-like bonding material in order to adjust the viscosity, and there is a problem that the firing temperature at the time of bonding the bonded materials depends on the decomposition temperature of the organic component. It was. Moreover, since an organic component remains on the surface of the copper nanoparticles or the like, it causes voids and cracks, resulting in a decrease in bonding force. For this reason, in order to utilize a paste-like joining material, there existed a subject that the process of removing organic components, such as preliminary drying, was needed.

  In addition, the paste-like bonding material has a problem that it is difficult to uniformly apply to the bonding surface of the material to be bonded and it is difficult to handle. Furthermore, when the paste-like bonding material is stored for a long period of time, it is difficult to maintain the dispersibility of the copper nanoparticles, and the paste is stored frozen or excessively mixed with a copper nanoparticle dispersant. There was also a problem that it was necessary. These have the subject that all become a factor which causes deterioration of the quality after joining.

  Therefore, in recent years, a sheet-like bonding material using copper nanoparticles as a raw material (hereinafter referred to as “bonding sheet”) has been used (Patent Documents 2 to 5). Here, the joining sheet | seat which uses a copper nanoparticle as a raw material has a strong joining force unlike copper foil and a copper nanoparticle single-piece | unit (aggregate | assembly). Moreover, since it is a sheet form, it has the advantage that it is easy to handle at the time of joining.

JP 2011-073011 A JP 2014-167145 A Japanese Unexamined Patent Publication No. 2013-039580 JP2013-236090A JP-A-2015-104748

  By the way, the joining sheet disclosed in Patent Documents 2 to 4 is formed into a sheet by sintering a paste containing copper nanoparticles. Thus, in the joining sheet manufactured by sintering the paste, stress is applied to the joining sheet due to heating and pressurization when joining the members to be joined, and the copper nanoparticles are sintered in a small portion. As a result, a problem arises in that a sufficient bonding force cannot be realized.

  Further, the bonding sheet disclosed in Patent Document 5 is formed into a sheet by making a bulk alloy foil or the like porous, but is limited to a case where a noble metal such as silver or a mixture thereof is used as a raw material. Therefore, it has been impossible to manufacture a bonding sheet using only copper as a raw material.

  As described above, it has been desired to realize a bonding material having high bonding strength using copper nanoparticles as a raw material.

  This invention is made | formed in view of the said situation, Comprising: It makes it a subject to provide the joining material which uses a copper nanoparticle as a raw material which has high joining power.

  It is another object of the present invention to provide a method for manufacturing the bonding material and to provide a bonded body in which two or more members are bonded using the bonding material.

In order to solve this problem, the present invention has the following configuration.
(1) A plate-like or sheet-like bonding material containing fine particles mainly composed of copper having an average particle diameter of 300 nm or less and in which the fine particles are in close contact, and the porosity of the bonding material is 0.30. Less than a bonding material.
(2) The bonding material according to item 1, wherein the thickness is 200 μm or less.

(3) a first step of preparing fine particles mainly composed of copper having an average particle size of 300 nm or less, a second step of pressurizing the fine particles to 0.5 GPa or more and forming them into a plate shape or a sheet shape, A method for manufacturing a bonding material comprising:
(4) The manufacturing method of the bonding material according to item 3 above, wherein the second step is performed in an air atmosphere.
(5) The method for manufacturing a bonding material according to item 3 or 4, wherein the second step is performed at room temperature.

(6) The bonding material according to item 1 above, a first bonded member, and a second bonded member, wherein the bonding material is interposed between the first bonded member and the second bonded member. A joined body provided with
(7) The joined body according to item 6 above, wherein the shear strength is 30 MPa or more.

  The bonding material of the present invention includes fine particles mainly composed of copper having an average particle diameter of 300 nm or less, these fine particles are in close contact with each other, and the porosity is less than 0.30. And has a high bonding strength.

  In the method for producing a bonding material of the present invention, a fine particle mainly composed of copper having an average particle diameter of 300 nm or less is prepared, and this is pressed into 0.5 GPa or more without careful classification to form a plate or sheet. By forming, the joining material mentioned above can be manufactured easily.

  The joined body of the present invention provides the joined body in which the first and second joined members are joined with high joining force because the joining material described above is provided between the first and second joined members. can do.

It is a perspective view which shows an example of the structure of the jig for manufacturing the joining material used for the verification test of this invention. It is a photograph which shows an example of a structure of the joining material used for the verification test of this invention. It is a figure which shows the result of the SEM observation of the cross section of the joining material used for the verification test of this invention. It is a figure which shows the relationship between the pressure at the time of pressure-molding the joining material used for the verification test of this invention, and a porosity. It is a perspective view for demonstrating the structure of the conjugate | zygote used for the verification test of this invention.

  Hereinafter, a bonding material as an embodiment to which the present invention is applied and a manufacturing method thereof will be described in detail with reference to the drawings together with a bonded body using the bonding material. In addition, in the drawings used in the following description, in order to make the features easy to understand, there are cases where the portions that become the features are enlarged for the sake of convenience, and the dimensional ratios of the respective components are not always the same as the actual ones. Absent.

<Bonding material>
First, an example of a configuration of a bonding material that is an embodiment to which the present invention is applied will be described.
In the bonding material of this embodiment, fine particles containing copper as a main component (hereinafter, also simply referred to as “copper nanoparticles”) are in close contact so that the porosity is less than 0.30, and are in the form of a plate or a sheet. It is a form.

  The fine particles mainly composed of copper (copper nanoparticles) are not particularly limited as long as they contain copper (Cu) in the component, but 95% by mass or more of the copper element with respect to the whole fine particles, The content is preferably 100% by mass or less, and more preferably 97% by mass or more.

  The average particle diameter of the fine particles is preferably 300 nm or less.

  The particle diameter of the fine particles is preferably in the range of 5 nm or more and 500 nm or less. Moreover, although the particle diameters of the fine particles may be uniform, the particle diameters may be distributed around the average particle diameter.

  The particle diameter of the fine particles refers to the diameter of a sphere in the case of a sphere, but refers to the length in the major axis direction in the case of an elliptic sphere. Moreover, the measuring method of a particle diameter is measured using SEM (scanning electron microscope).

  As will be described later, the bonding material of the present embodiment is formed into a plate shape or a sheet shape by pressurizing the fine particles with a required pressure. Here, the thickness of the bonding material (thickness in the pressing direction) is not particularly limited, and can be appropriately selected according to the mode of the bonding material such as a plate shape or a sheet shape. Specifically, for example, a range of 20 to 200 μm is preferable, and a range of 50 to 100 μm is more preferable.

  In addition, the shape of the bonding material when viewed in plan is not particularly limited, and can be appropriately selected according to the shape of the bonding surface of the members to be bonded. Further, as will be described later, the above-described fine particles may be pressed at a required pressure to form a pressure surface when forming a plate or sheet. Specifically, a rectangle, a circle, etc. are mentioned, for example.

  Further, as will be described later, the bonding material of the present embodiment is formed by pressing the above-described fine particles at a required pressure to form a plate shape or a sheet shape, and the porosity is less than 0.30. Since the above-mentioned copper nanoparticles are in close contact with each other so as to have a porosity of less than 0.30, the bonding material is formed into a plate shape or a sheet shape, so that a high bonding force can be realized.

  In this specification, the porosity is defined as a ratio obtained by deleting the volume of the fine particles from the volume of the manufactured joining sheet. The porosity is calculated by measuring the average film thickness and area of the bonding sheet, and calculating the volume occupied from the average density of the fine particles by measuring the weight of the fine particles. Can be calculated.

<Manufacturing method of bonding material>
Next, an example of the manufacturing method of the bonding material described above will be described.
The manufacturing method of the bonding material of this embodiment includes a step of preparing the above-described fine particles (copper nanoparticles) (first step) and a step of pressurizing the fine particles to 0.5 GPa or more to form a plate shape or a sheet shape. (Second process).

(First step)
First, fine particles (copper nanoparticles) having a required average particle diameter and containing copper as a main component are prepared as raw materials. Here, as the copper nanoparticles used as a raw material, it is desirable to use those which do not require a protective agent, a dispersing agent or the like. As such a copper nanoparticle, what is obtained by the manufacturing method described in the patent document (patent 4304221 gazette) is mentioned, for example.

In addition, it is desirable not to use an organic solvent for the copper nanoparticles used as a raw material. However, in order to make the particles uniform and to adjust the shape, a highly volatile alcohol (for example, ethanol, 2-propanol, etc.) may be used in such an amount that the copper nanoparticles are dispersed. Moreover, it is preferable to volatilize the used alcohol etc. by the 2nd process.
In this way, copper nanoparticles having a required average particle diameter are prepared.

(Second step)
Next, the copper nanoparticles prepared in the first step are pressurized to a required pressure or higher to mold (press molding) a plate-shaped or sheet-shaped bonding material. Here, the apparatus used for pressure molding is not particularly limited, and for example, a metal jig, a compression molding machine, or the like can be used.

  Although the pressure in the case of pressure molding will not be specifically limited if it is 0.5 GPa or more, It is preferable to set it as the range of 0.5-1.40 GPa. By setting the pressure at the time of pressure molding within the above range, a bonding material having a porosity of less than 0.30 can be molded.

  In addition, in the manufacturing method of the bonding material of the present embodiment, the pressure at the time of pressure molding is used in order to prevent deterioration and deformation of the bonding material when bonding two or more members to be bonded when manufacturing a bonded body described later. Is preferably set to a pressure higher than that at the time of joining the joined body.

  The temperature during the pressure molding is preferably 5 ° C. or higher and 150 ° C. or lower. In particular, the bonding material can be molded without oxidizing the surface of the copper nanoparticles by performing pressure molding at a room temperature of 5 ° C. or more and 35 ° C. or less.

  The pressurization time at the time of pressure molding is preferably 5 seconds or more and 30 seconds or less, and more preferably 10 seconds or more and 20 seconds or less.

The pressure molding can be performed in an air atmosphere, but is not particularly limited, and may be performed in an inert gas atmosphere such as nitrogen gas. Further, for the purpose of improving the bonding force, pressure molding may be performed in a reducing gas atmosphere. In addition, although it does not specifically limit as reducing gas, For example, what contains hydrogen, formic acid, etc. as a reducing substance in nitrogen gas is mentioned.
From the above, the bonding material of the present embodiment having a sufficient bonding force can be molded.

<Joint>
Next, an example of the structure of the joined body joined using the joining material described above will be described.
The joined body of the present embodiment includes the above-described joining material, the first joined member, and the second joined member, and the joining material provided between the first and second joined members. A 1st to-be-joined member and a 2nd to-be-joined member are joined.

  Examples of the material of the first and second members to be joined include copper, silicon, aluminum, copper oxide, silicon oxide, alumina, silicon nitride, aluminum nitride, boron nitride, silicon carbide, or alloys thereof. , Mixtures and the like. Note that the first and second members to be joined may be made of the same material or different materials.

  In the joined body of the present embodiment, the shear strength between the first joined member and the second joined member joined by the joining material is 30 MPa or more. In other words, the bonding material described above exhibits a bonding strength at which the shear strength between the bonded members bonded using the bonding material is 30 MPa or more.

  The shear strength of the joined body of the present embodiment can be measured by a commercially available bond tester device (for example, “400 Plus” manufactured by Daisy Corporation).

  The method for manufacturing the joined body (joining conditions) of the present embodiment is not particularly limited, and can be appropriately selected depending on the material and combination of the members to be joined. Specifically, for example, in a nitrogen gas atmosphere to which 3% by volume of hydrogen gas is added, the pressure can be 10 MPa, the temperature can be 300 ° C., and the time can be 10 minutes.

  As described above, according to the bonding material of this embodiment, the fine particles mainly containing copper having an average particle diameter of 300 nm or less are included, and these fine particles are in close contact with each other, and the porosity is less than 0.30. Therefore, when this is used to join a plurality of members, a high joining force is achieved.

  According to the manufacturing method of the bonding material of the present embodiment, fine particles mainly composed of copper having an average particle diameter of 300 nm or less are pressed to 0.5 GPa or more to form a plate shape or a sheet shape. The material can be easily manufactured.

  According to the joined body of the present embodiment, the joining material is provided between the first and second members to be joined, and the first and second joined members are joined by the joining material. It becomes a joined body joined with a high joining force of 30 MPa or more.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

  Hereinafter, the effect of the present invention will be described in detail by a verification test. In addition, this invention is not limited to the content of the following verification tests.

<Verification test 1>
A sheet-like bonding material (bonding sheet) was manufactured using the jig shown in FIG.
Specifically, first, copper nanoparticles obtained by a production method described in a patent document (Japanese Patent No. 4304221) were prepared as raw materials. As a result of calculating the average particle diameter of the copper nanoparticles, it was 300 nm or less.

  Next, as shown in FIG. 1, powdered copper nanoparticles prepared as a raw material were added to a central hole of a cylindrical jig made of tungsten carbide having a length of 6 mm with a hole having a diameter of 6 mm in the center. Next, a tungsten carbide cylinder having a diameter of 6 mm was inserted perpendicularly to the center hole from both ends of the center hole of the jig, and pressure molding was performed.

  The pressure molding was performed in a normal temperature (20 ° C.) atmosphere at a pressure of 0.5 GPa for 10 seconds. As a result, a bonding sheet having a diameter of 6 mm, a thickness of 50 μm, and a porosity of 0.25 as shown in FIG. 2 was obtained. The porosity is calculated by measuring the average film thickness and area of the bonding sheet, and calculating the volume occupied by the fine particles by measuring the weight from the average density of the fine particles. Calculated.

  In FIG. 3, the SEM (scanning electron microscope) image of the cross section of the obtained sheet | seat for joining is shown. As shown in FIG. 3, when the cross section of the bonding sheet was confirmed, the copper nanoparticles in the bonding sheet had a particle diameter of about 5 nm to 300 nm, the average particle diameter was 300 nm or less, and the copper nanoparticles were It was confirmed that was kept in close contact.

<Verification test 2>
Next, the pressure at the time of pressure molding in the verification test 1 described above is changed to 0.05 to 1.4 GPa to produce a joining sheet, and the porosity of the obtained joining sheet is measured and pressurized. The relationship with molding pressure was verified. Further, the strength of the obtained bonding sheet was confirmed.

  In FIG. 4, the relationship between the pressure at the time of pressure-molding a joining material and the porosity of the obtained joining material is shown. As shown in FIG. 4, when the pressure during pressure molding is 0.5 GPa or more, the porosity of the bonding sheet is stable at about 0.24 (less than 0.30), whereas 0.5 GPa It was confirmed that the porosity tends to decrease as the pressure increases.

  From this, when the pressure at the time of pressure molding is 0.5 GPa or more, the copper nanoparticles are strongly joined in a state (close contact state) almost close to the limit, whereas the sheet is strong in strength, It confirmed that joining of copper nanoparticles became inadequate if it was less than 0.5 GPa. Actually, the bonding material pressure-molded at a pressure of less than 0.5 GPa is fragile and it is difficult to maintain the shape of the sheet.

<Verification test 3>
Next, the copper plate and the copper cylinder were joined using a joining material (joining sheet) to produce a joined body, and the shear strength of the joined body (that is, the joining strength of the joining material) was compared and verified.

(Joining material)
In the verification test 1 described above, pressure molding is performed under the conditions of 0.50, 0.71, 1.40 GPa and 10 seconds in the atmosphere of normal temperature (20 ° C.), the diameter is 6 mm, the thickness is 50 μm bonding materials 1 to 3 were manufactured. The porosity of the bonding materials 1 to 3 is shown in Table 1 below.
In addition, in the case where pressure molding was performed under a condition where the pressure was less than 0.50 GPa, it was difficult to maintain the shape of the sheet, and thus it could not be used for joining described later.
Further, a copper foil having a thickness of 50 μm (produced by Fukuda Metal Foil Industry Co., Ltd., oxygen-free copper foil) was prepared and used as the bonding material 4.
Furthermore, the copper nanoparticles themselves having an average particle diameter of 300 nm or less, which were used as raw materials for the bonding materials 1 to 3, were used as the bonding material 5.

(Joint)
As shown in FIG. 5, a 6 mm diameter copper cylinder (first member to be joined) and a 18 mm square copper plate (second member to be joined) are joined using the joining materials 1 to 5 prepared as described above. Then, a joined body was formed (manufactured). The joining conditions of the joined body were as follows: pressure: 10 MPa, temperature: 300 ° C., time: 10 minutes in a nitrogen gas atmosphere with 3% by volume of hydrogen gas added.

(Shear strength)
The shear strength of the joined body joined using the joining materials 1 to 5 was measured using a bond tester (manufactured by Daisy, “4000 Plus”). The results are shown in Table 1 below.

  As shown in Table 1, it was confirmed that all of the joined bodies formed by using the bonding materials 1 to 3 of the present invention formed using a pressure of 0.50 GPa or more had a shear strength of 20 MPa or more. did. That is, it was confirmed that the bonding materials 1 to 3 of the present invention have a high bonding force.

  On the other hand, it was confirmed that all the joined bodies joined using the joining materials 4 and 5 had a shear strength of less than 20 MPa. That is, it was confirmed that the bonding materials 4 and 5 could not obtain a high bonding force.

  In addition, in the joining material which pressure-molded with the pressure of less than 0.50 GPa, the shape was very unstable and it was difficult to maintain a sheet form. For this reason, a joined body could not be formed.

  The bonding material, the manufacturing method of the bonding material, and the bonded body of the present invention are difficult to use in bonding materials such as solder, such as in applications for bonding electronic components, more specifically in electronic devices called power devices. It can be used for joining parts such as substrates and devices in high-temperature environments.

Claims (7)

A plate-like or sheet-like bonding material comprising fine particles mainly composed of copper having an average particle size of 300 nm or less, wherein the fine particles are in close contact with each other,
The joining material whose porosity of the said joining material is less than 0.30.   The bonding material according to claim 1, wherein the thickness is 200 μm or less. A first step of preparing fine particles mainly composed of copper having an average particle size of 300 nm or less;
A second step of pressurizing the fine particles to 0.5 GPa or more to form a plate shape or a sheet shape.   The method for manufacturing a bonding material according to claim 3, wherein the second step is performed in an air atmosphere.   The manufacturing method of the bonding | jointing material of Claim 3 or 4 which performs the said 2nd process at normal temperature. The bonding material according to claim 1, a first bonded member, and a second bonded member,
A joined body in which the joining material is provided between the first joined member and the second joined member.   The joined body according to claim 6, wherein the shear strength is 30 MPa or more.