JP2010227963A - Joining method using metal nanoparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joining method by which the thickness of a joint layer including metal nanoparticles is made constant and uniform. <P>SOLUTION: A material 12 to be joined is pressed until the lower surface of the material 12 to be joined is brought into contact with spacers 13. By this pressing step, a paste layer 25 is compressed, and the thickness of the paste layer 25 is made A. Since the spacers 13 are longitudinally and laterally arranged, there is no possibility that the material 12 to be joined is inclined. As a result, a paste layer 25 of which the thickness is constant and uniform is obtained. By using the spacers 13, the thickness of a joint layer including metal nanoparticles is made constant and uniform. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a bonding method using metal nanoparticles as a bonding element.

  Joining two materials to be joined with a brazing material is widely used in practice. In recent years, a technique using nano-sized metal ultrafine particles (referred to as metal nanoparticles) instead of a brazing material has been proposed (see, for example, Patent Document 1 (FIG. 1)).

Patent document 1 is demonstrated based on the following figure.
FIG. 9 is a diagram for explaining a conventional bonding method. In FIG. 9A, a bonding material 103 containing metal nanoparticles is interposed between a lower bonded member 101 and an upper bonded member 102. . Then, in (b), the bonding structure is completed by heating while applying pressure.

However, Patent Document 1 includes the following problems.
First, it is known that an organic gas is generated from the bonding material 103 containing metal nanoparticles when heated. When the area of the bonding material 103 is large, the outgassing from the center portion is worsened. In the part where the gas does not escape, the organic film is not sufficiently removed, and the sinter bond is insufficient. As a result, a desired bonding strength cannot be obtained.
Secondly, when pressed as indicated by arrows P and P, the upper member 102 to be joined is slightly inclined due to mechanical errors and backlash of the equipment. Then, a thick part and a thin part are generated in the bonding material 103. In addition, since the pressing force varies in size, it is difficult to make the bonding material 103 constant in thickness.

A joining method that can solve the first problem described above has been proposed (see, for example, Patent Document 2 (FIG. 3)).
FIG. 3 of Patent Document 2 will be described below.
FIG. 10 is a diagram for explaining another conventional joining method, in which metal fine particles 112 are applied to the lower metal plate 111 in a striped manner, the upper metal plate 113 is stacked, and the upper pressure is high enough to prevent the tunnel 114 from disappearing. The metal plate 113 is heated while being pressed down. Bonding is performed at a certain time by increasing the pressure and increasing the temperature.

Since the gas is released through the tunnel 114, the first problem described above is solved.
However, the second problem (film thickness instability) remains unsolved.
In order to stabilize the bonding strength, the thickness of the bonding member is required to be constant and uniform.

JP 2008-202084 A JP 2007-330980 A

  An object of the present invention is to provide a bonding method capable of making the thickness of a bonding layer containing metal nanoparticles constant and uniform.

The invention according to claim 1 is a joining method of joining a plurality of materials to be joined with metal nanoparticles,
A plurality of materials to be joined, a linear spacer having a constant diameter, a coating mask provided with a coating pattern including a shielding portion having a width equal to the diameter of the spacer, and a metal nanometer coated with an organic coating Preparing a metal nanoparticle paste obtained by dispersing particles in a dispersion medium;
Using the metal nanoparticle paste and the coating mask, an application step of applying a coating film having a thickness larger than the diameter of the spacer to one of the bonded materials;
A spacer arrangement step of arranging the spacer in the groove formed in the coating film by the shielding portion;
A step of superimposing the other material to be joined;
A step of pressing the materials to be joined until the distance between the materials to be joined matches the diameter of the spacer;
Maintaining the distance between the materials to be bonded in a state where the distance between the materials to be bonded matches the diameter of the spacer, and removing the spacer;
And a step of firing the resultant combined product.
Bonding method using metal nanoparticles.

  In the invention which concerns on Claim 2, the process of baking the obtained unification thing is the 1st heating process which heats the obtained union thing so that a dispersion medium scatters, and then an organic film gasifies, A second heating step of heating the metal nanoparticles while applying pressure so that the metal nanoparticles are diffusion bonded to the material to be bonded.

  In the invention which concerns on Claim 1, in the process of pressing to-be-joined materials, to-be-joined materials are pressed until the space | interval of to-be-joined materials corresponds to the diameter of a spacer. Thereby, the thickness of the metal nanoparticle paste becomes the same as the diameter of the spacer, and the thickness of the bonding layer containing the metal nanoparticles can be made constant and uniform. Furthermore, the metal nanoparticles divided into a small area by the spacer have a variation range that relaxes the stress due to the difference in thermal expansion coefficient between the bonding material and the bonded material in the bonding surface direction compared to the metal nanoparticles applied on one surface. There is an effect to prevent cracks.

In the invention which concerns on Claim 2, the process to bake consists of a 1st heating process and a 2nd heating process.
In the first heating step, the dispersion medium is scattered from the combined product. Next, in the second heating step, the organic coating is gasified and the metal nanoparticles are diffusion bonded to the material to be bonded.
Since a space is formed in the spacer arrangement portion, and this space becomes a desorption route of the dispersion medium / organic solvent, a void in the central portion can be prevented and strong bonding can be achieved.

It is a figure explaining the preparatory process which concerns on this invention. It is a figure explaining the application | coating process which concerns on this invention. It is a figure explaining the superposition process concerning the present invention. FIG. 4 is a view taken in the direction of arrow 4 in FIG. 3. It is a figure explaining the press process which concerns on this invention. It is a figure explaining the 1st heating process concerning the present invention. It is a figure explaining the 2nd heating process concerning the present invention. It is explanatory drawing of the shear strength test given to a conjugate | zygote. It is a figure explaining the conventional joining method. It is a figure explaining another conventional joining method.

  Embodiments of the present invention will be described below with reference to the accompanying drawings.

Embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1A, materials to be joined 11 and 12 are prepared. Although the to-be-joined materials 11 and 12 are demonstrated by 2 sheets, 3 or more sheets may be sufficient.
The material of the materials to be joined 11 and 12 is arbitrary as long as it is a sinterable metal material (including a metal-based composite material). For example, steel, stainless steel, copper, aluminum, titanium, Al—SiC composite Material or carbon-metal composite.

These to-be-joined materials 11 and 12 are wash | cleaned. Washing is carried out by one of the following procedures.
The first procedure is washing with acetone, washing with pure water and drying.
The second procedure is washing with isopropyl alcohol (IPA), washing with pure water and drying.
The third procedure is washing with acetone or IPA, washing with acid, washing with pure water and drying.
In the fourth procedure, cleaning is performed by a plasma cleaning method.

  A spacer 13 shown in FIG. 1B is prepared. As the spacer 13, a linear rod, rod, or wire represented by a round bar or a square bar having a constant diameter A (polygonal cross-section bars such as a triangular cross section, a square cross section, and a pentagon cross section) can be used.

A coating mask 14 shown in FIG. 1C is prepared. The coating mask 14 includes a frame 15 and a screen 16 stretched on the frame 15, and the screen 16 includes shielding portions 17 and 18 and transmission portions 19 and 19.
As shown in (d), which is an arrow view of (c), the screen 16 is provided with a coating pattern including shielding portions 17 and 18 and transmission portions 19 and 19. The shielding width B of the shielding portion 17 between the transmission portions 19 and 19 is set to a size corresponding to the diameter A of the spacer 13. Specifically, A ≦ B.

  A metal nanoparticle paste 20 shown in FIG. 1 (e) is prepared. This metal nanoparticle paste 20 is obtained by dispersing metal nanoparticles 22 coated with an organic coating 21 containing C, H, and O in a dispersion medium 23. The metal of the metal nanoparticles 22 is preferably silver. The dispersion medium 23 includes one or more of ethylene glycol, toluene, tetradecane, butanediol, and lower alcohol.

  Next, as shown in FIG. 2, a coating mask 14 is placed on one of the materials to be joined 11, and a metal nanoparticle paste 20 indicated by an imaginary line is placed on a screen 16, and the metal nanoparticle paste 20 is scraped. Scratch with 24. Then, the metal nanoparticle paste 20 reaches the material to be bonded 11 through the transmission parts 19 and 19. The coating thickness C of the metal nanoparticle paste 20 is set to be larger than the spacer diameter A (FIG. 1, reference numeral 13).

  When the coating mask 14 is carefully removed, paste layers 25 and 25 having a thickness of C are laminated on the upper surface of the material to be joined 11 as shown in FIG. A groove 26 is formed between the adjacent paste layers 25. The groove portion 26 is formed by a screen shielding portion (reference numeral 17 in FIG. 2).

  Next, as shown in FIG. 4A (viewed in the direction of arrow 4 in FIG. 3), the long and short spacers 13 are housed vertically and horizontally in the groove 26. The application pattern in this figure is a rhombus base. However, if the application pattern is a rectangular base, the shape is as shown in FIG. 4B. Therefore, the groove 26 between the adjacent paste layers 25 is short and long. The spacers 13 are accommodated vertically and horizontally. That is, the shape of the coating pattern is arbitrary, and the spacers 13 are accommodated vertically and horizontally in the grooves 26 provided there.

  Returning to FIG. 3, the other material to be bonded 12 is covered. Subsequently, as shown in FIG. 5, the bonded material 12 is pressed until the lower surface of the bonded material 12 hits the spacer 13. By this pressing step, the paste layer 25 is compressed to a thickness A. As described with reference to FIG. 4, since the spacers 13 are arranged vertically and horizontally, there is no concern that the material to be joined 12 is inclined when pressed in FIG. As a result, a uniform paste layer 25 having a uniform thickness is obtained.

  The spacer 13 shown in FIG. 5 is pulled out before the next first heating step. That is, with the configuration shown in FIG. 5, only the spacer 13 is pulled out to the front side. The obtained combined product 28 is heated in the following manner.

As shown in FIG. 6, the combined product 28 is charged into a first heating furnace 30 provided with a heater 29.
And in this 1st heating furnace 30, 1st heating is implemented for 5 to 120 minutes at the temperature of 60-120 degreeC in air | atmosphere atmosphere. By this first heating step, the dispersion medium (FIG. 1, reference numeral 23) is removed.

  Next, the combined product 28 is charged into a second heating furnace 33 including the heater 31 and the press punch 32 shown in FIG. Then, in the second heating furnace 33, the second heating is performed in the air atmosphere at a temperature of 150 to 300 ° C. for 5 to 120 minutes while being suppressed by the press punch 32. By this second heating step, the organic coating is gasified and removed. Since the generated gas passes through the groove 26 between the paste layers 25, 25, it is discharged smoothly and in a short time.

  The paste layer 25 undergoes a sintering reaction by heat treatment. That is, since the organic coating has disappeared, the metal nanoparticles (FIG. 1, reference numeral 22) directly contact the bonded materials 11 and 12 and are bonded by a sintering reaction.

As a result, as shown in FIG. 8, a laminated body 36 composed of the materials to be joined 11 and 12 joined by the joining layers 35 and 35 made of metal nanoparticles is obtained.
The shear strength can be obtained by applying an external force F to the laminate 36. The shear strength is a value obtained by dividing by the area S of the bonding layer 35 (the total area when there are a plurality of bonding layers 35). That is, it is obtained by calculation of shear strength = F / S.

  Although detailed conditions are omitted, according to the present invention, as shown in the Examples column of the following table, the thickness of the bonding layer was uniform 40 μm and the shear strength was 20 MPa.

In a comparative example in which application was performed using an ordinary screen and the other conditions were the same as in the example, the thickness of the bonding layer varied from 30 to 100 μm, and the shear strength remained at 9 MPa.
In the comparative example, the compressibility in the paste layer varies, and as a result, the strength of the bonding layer varies, and the shear strength is considered to be low.

  On the other hand, according to the present invention, it is considered that the thickness of the paste layer becomes uniform, and as a result, the strength of the bonding layer is stabilized and the shear strength is increased.

Although described in detail above, the present invention can be summarized as follows.
As shown in FIG. 1, the present invention includes a plurality of materials to be joined 11, 12, a linear spacer 13 having a constant diameter A, and a shielding portion 17 having a width equivalent to the diameter A of the spacer 13. Preparing a coating mask 14 provided with a pattern, and a metal nanoparticle paste 20 in which metal nanoparticles 22 coated with an organic coating 21 are dispersed in a dispersion medium 23;
As shown in FIG. 2, using the metal nanoparticle paste 20 and the coating mask 14, a coating step of coating a coating film having a thickness B larger than the diameter A of the spacer 13 on one bonded material 11,
As shown in FIG. 4, a spacer arrangement step of arranging the spacer 13 in the groove portion 26 formed in the coating film by the shielding portion 17,
As shown in FIG. 3, a step of superimposing the other material to be joined 12;
As shown in FIG. 5, the step of pressing the members to be bonded 11 and 12 until the distance between the members to be bonded 11 and 12 matches the diameter A of the spacer 13;
Maintaining the distance between the materials to be bonded in a state where the distance between the materials to be bonded matches the diameter of the spacer, and removing the spacer 13;
As shown in FIG. 6, a first heating step of heating the obtained combined product 28 so that the dispersion medium is scattered,
As shown in FIG. 7, the method includes a second heating step of heating while applying pressure so that the organic coating is gasified and the metal nanoparticles are diffusion bonded to the material to be bonded.

The first heating process and the second heating process can be combined into a firing process. By combining the firing steps, the treatment of the dispersion medium and the treatment of the organic coating are performed in parallel. Two processes can be made into one process, and productivity can be improved However, it is desirable to implement a baking process in two processes, a 1st heating process and a 2nd heating process. Since the dispersion medium treatment, the organic film treatment, and the diffusion bonding treatment are performed in this order, the dispersion medium and the organic solvent are better separated from the gaps in the spacer arrangement portion, and voids during sintering are removed. This is because a strong high-quality bonding layer is obtained to prevent this.

  The present invention is suitable for a technique for joining metal plates together.

  DESCRIPTION OF SYMBOLS 11 ... One to-be-joined material, 12 ... Other to-be-joined material, 13 ... Spacer, 14 ... Application mask, 20 ... Metal nanoparticle paste, 21 ... Organic coating, 22 ... Metal nanoparticle, 23 ... Dispersion medium, 26 ... Groove part, 28 ... union, 30 ... first heating furnace, 33 ... second heating furnace.

Claims (2)

In a joining method for joining a plurality of materials to be joined with metal nanoparticles,
A plurality of materials to be joined, a linear spacer having a constant diameter, a coating mask provided with a coating pattern including a shielding portion having a width equal to the diameter of the spacer, and a metal nanometer coated with an organic coating Preparing a metal nanoparticle paste obtained by dispersing particles in a dispersion medium;
Using the metal nanoparticle paste and the coating mask, an application step of applying a coating film having a thickness larger than the diameter of the spacer to one of the bonded materials;
A spacer arrangement step of arranging the spacer in the groove formed in the coating film by the shielding portion;
A step of superimposing the other material to be joined;
A step of pressing the materials to be joined until the distance between the materials to be joined matches the diameter of the spacer;
Maintaining the distance between the materials to be bonded in a state where the distance between the materials to be bonded matches the diameter of the spacer, and removing the spacer;
A bonding method using metal nanoparticles, characterized by comprising a step of firing the resultant union. The step of firing the obtained combined product,
A first heating step of heating the obtained combined product so that the dispersion medium scatters;
The metal nanoparticle according to claim 1, further comprising a second heating step in which the organic coating is gasified and heated while applying pressure so that the metal nanoparticle is diffusion bonded to the material to be bonded. Bonding method using.

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