JP7852016B2 - W-Pt-Cu alloy for joining - Google Patents

Description

This invention relates to alloy materials. For example, it relates to alloy materials that can be used as a bonding material for joining tungsten members to metal members other than tungsten.

Tungsten components containing tungsten (W) (hereinafter also referred to as "W components") have a high melting point and a low coefficient of thermal expansion, resulting in excellent reliability in high-temperature environments. Therefore, W components are used in ultra-high-temperature parts exposed to high temperatures, such as divertors, accelerators, plasma discharge devices, high-temperature furnaces, and thin-film deposition equipment. On the other hand, tungsten is a rare and expensive metal, and difficult to process, so it is often used in a bonded state with other metal components (hereinafter also referred to as "dissimilar metal components"). For example, copper (Cu) is often used as the dissimilar metal component to be bonded, considering factors such as material cost and heat dissipation (thermal conductivity).

For joining W members and dissimilar metal members, brazing materials containing silver (Ag) or copper are used, for example. Examples of such brazing materials are disclosed in Patent Documents 1 and 2. Specifically, Patent Document 1 discloses a technique for joining cemented carbide alloys, where tungsten carbide (WC) is sintered using cobalt (Co), and uses a brazing material containing silver (Ag), copper (Cu), zinc (Zn), and cobalt (Co). This suppresses the diffusion of Co from the cemented carbide into the brazing material, preventing breakage due to a decrease in the strength of the cemented carbide. On the other hand, Patent Document 2 describes the use of a phosphorus (P)-containing brazing material when joining alumina-dispersed copper to a metal to be joined (e.g., tungsten). The heat treatment temperature during joining is set to a range lower than the melting point of copper and higher than the melting point of copper reduced by the eutectic reaction between phosphorus and copper. This joins the alumina-dispersed copper to the metal to be joined.

Furthermore, as a joining method other than brazing, the NDB method (Non-Defective Bonding) can be mentioned. This NDB method is a technique for directly joining a W member and a dissimilar metal member, and an example of this is disclosed in Non-Patent Documents 1 and 2. For example, in Non-Patent Document 1, the copper member is melted and cooled while in contact with the tungsten member. Non-Patent Document 1 predicts that by implementing this joining method, the molten copper member penetrates the minute irregularities on the surface of the W member, increasing the interatomic attractive forces and forming a pseudo-metallic bond.

Patent No. 5385951 Patent No. 6528257

J. Plasama Fusion Res. Vol. 95, No. 8 (2019) 374-376 Journal of the Japan Society for Smart Processes, Vol. 6, No. 5 (September 2017)

Furthermore, with the recent expansion of applications for W members, there is a need for novel technologies that can more effectively join W members to dissimilar metal members. This invention was made in response to such demands, and its main objective is to provide a novel technology that enables suitable joining of tungsten members to dissimilar metal members.

The inventors conducted various experiments and studies to find a novel technique for joining tungsten members and dissimilar metal members, and as a result, discovered a novel alloy material that functions suitably as a joining material for W members. Specifically, they discovered that when an alloy containing Pt and W (Pt-W alloy) is heated in contact with a Cu source containing copper (Cu), the Pt in the Pt-W alloy surprisingly migrates to Cu. Furthermore, this absorption of Pt by Cu proceeds as Cu penetrates the grain boundaries of the Pt-W alloy, resulting in the formation of a ternary two-phase alloy material (hereinafter also referred to as "W-Pt-Cu alloy") in which a W phase, mainly composed of W, and a Pt-Cu phase containing Pt and Cu are mixed. Generally, it is thought that W and Cu do not mix with each other to form an alloy, and such an alloy has not been reported in the past. The inventors of this invention hypothesized that this W-Pt-Cu alloy could be a novel bonding material capable of effectively joining dissimilar metal components, such as Cu, with W components. Therefore, they analyzed the properties and formation mechanism of this alloy material. As a result, they found that the above-mentioned W-Pt-Cu alloy is formed by the mechanism described below.

First, as mentioned above, the Pt-W alloy, which is the precursor material for the W-Pt-Cu alloy, is an alloy containing Pt and W. Since the Pt-Cu alloy is more stable than this Pt-W alloy, it is thought that when the Pt-W alloy was brought into contact with the Cu source, the migration of Pt to Cu in the Pt-W alloy progressed. Furthermore, the interface between the W phase, which is mainly composed of W, and the Pt-Cu phase, which contains Pt and Cu, is considered to be more stable than the interface between the Pt-W alloy and Cu. Now, looking at the bonding with the tungsten member, the stability of the interface between the W phase and the Pt-Cu phase leads to the stability of the bonding between the tungsten member and the alloy material. This is because, at the bonding surface, the tungsten member mainly bonds with the Pt-Cu phase. In this way, by preparing a Pt-W alloy as a precursor material and migrating Pt to Cu in the Pt-W alloy, it is possible to manufacture an alloy material in which W and Cu, which were previously thought not to form an alloy, are mixed. Furthermore, such alloy materials can serve as novel bonding materials that enable suitable joining of tungsten components and dissimilar metal components.

The manufacturing method disclosed herein is based on the above-mentioned findings and is a method for producing a ternary two-phase alloy material (W-Pt-Cu alloy) in which a W phase and a Pt-Cu phase are mixed. This manufacturing method is characterized by transferring the platinum (Pt) from a Pt-W alloy containing platinum (Pt) and tungsten (W) to a Cu source containing copper (Cu). As described above, a W-Pt-Cu alloy can be produced by this manufacturing method. Furthermore, because the interface between the W phase and the Pt-Cu phase of such a W-Pt-Cu alloy is stable, it exhibits suitable bonding properties with W members, and because it contains a Pt-Cu phase, it exhibits suitable bonding properties with dissimilar metal members (Cu members, Pt members, etc.). In other words, the technology disclosed herein makes it possible to achieve suitable bonding between W members and dissimilar metal members.

In one preferred embodiment of the manufacturing method disclosed herein, the Pt-W alloy is an intermetallic compound. An example of such an intermetallic compound Pt-W alloy is _Pt₂W . By using such _Pt₂W as a precursor, a W-Pt-Cu alloy in which the W phase and the Pt-Cu phase are finely mixed can be produced.

In one preferred embodiment of the manufacturing method disclosed herein, a Pt-W alloy is brought into contact with a Cu source. According to the inventors' research, direct contact between the Pt-W alloy and the Cu source causes the migration of platinum (Pt) from the Pt-W alloy to copper (Cu), thereby producing a W-Pt-Cu alloy.

Furthermore, in a preferred embodiment of the manufacturing method disclosed herein, it is preferable to heat the contacted Pt-W alloy and Cu source. This promotes the migration of platinum (Pt) from the Pt-W alloy to copper (Cu), thereby enabling the efficient production of a W-Pt-Cu alloy.

A preferred embodiment of the manufacturing method disclosed herein comprises a Pt-W alloy production step of producing a Pt-W alloy by heat treatment while a Pt source containing platinum (Pt) and a W source containing tungsten (W) are in contact, and a W-Pt-Cu alloy production step of producing a W-Pt-Cu alloy by heat treatment while the Pt-W alloy and a Cu source are in contact, thereby moving the platinum (Pt) in the Pt-W alloy to Cu.
As described above, in order to produce a W-Pt-Cu alloy, it is necessary to use a Pt-W alloy as a precursor material. Such a Pt-W alloy can be efficiently produced by performing a heat treatment while the Pt source and the W source are in contact. Furthermore, according to the inventors' studies, even by simply bringing the Pt-W alloy into contact with the Cu source, the movement (diffusion) of Pt from the Pt-W alloy to Cu occurs, and a W-Pt-Cu alloy is produced. However, it takes a very long time to produce a sufficient W-Pt-Cu alloy by contacting only the Pt-W alloy and the Cu source. For this reason, in this embodiment, the heat treatment is performed while the Pt-W alloy and the Cu source are in contact, thereby promoting the movement of Pt from the Pt-W alloy to Cu. As described above, the manufacturing method of this embodiment allows for the efficient production of a W-Pt-Cu alloy.

Furthermore, in the embodiment of the Pt-W alloy formation process, the heating temperature in the Pt-W alloy formation process is preferably 800°C to 1200°C. Also, the heating time in the Pt-W alloy formation process is preferably 0.5 hours to 3 hours. By setting the conditions (heating temperature, heating time) of the Pt-W alloy formation process in this way, the Pt-W alloy can be efficiently produced, thereby improving the productivity of W-Pt-Cu alloy.

Furthermore, in the embodiment where the W-Pt-Cu alloy formation process is carried out, the heating temperature in the W-Pt-Cu alloy formation process is preferably 800°C to 1200°C. Also, the heating time in the W-Pt-Cu alloy formation process is preferably 0.5 hours to 3 hours. By setting the conditions (heating temperature, heating time) of the W-Pt-Cu alloy formation process in this way, the transfer of Pt from the Pt-W alloy to Cu can be appropriately induced, thereby improving the productivity of the W-Pt-Cu alloy.

In another preferred embodiment of the manufacturing method disclosed herein, a Pt-W alloy is formed at the boundary between the W source and the Pt source by interposing a platinum (Pt) source between a W source containing tungsten (W) and a Cu source, and by performing a heat treatment, the platinum (Pt) in the Pt-W alloy is moved to Cu to form a W-Pt-Cu alloy.
In the above-described embodiment, a W-Pt-Cu alloy is produced by performing two or more heat treatments, including a Pt-W alloy production step and a W-Pt-Cu alloy production step. However, the manufacturing method disclosed herein is not limited to the above-described embodiment. For example, experiments have confirmed that a W-Pt-Cu alloy can be produced even when a Pt source is interposed between a W source and a Cu source and the heat treatment is performed together. Specifically, as in this embodiment, when a W source, a Pt source, and a Cu source are heated together, a Pt-W alloy is formed at the boundary between the W source and the Pt source. As the heat treatment progresses further, the Pt-W alloy and Cu (including the Pt-Cu alloy) become finely intermingled, and the Pt in the Pt-W alloy moves to Cu. As a result, a W-Pt-Cu alloy is formed between the W source and the Cu source, in which the W phase and the Pt-Cu phase are mixed.

In the embodiment where the W source, Pt source, and Cu source are heated together, the heat treatment temperature is preferably between 800°C and 1200°C. Furthermore, the heat treatment time is preferably between 0.5 hours and 3 hours. By setting the heating conditions in this way, the formation of the Pt-W alloy and the transfer of Pt from the Pt-W alloy to Cu are appropriately generated, enabling the efficient production of the W-Pt-Cu alloy.

Furthermore, in the configuration in which the W source, Pt source, and Cu source are heated together, it is preferable to apply pressure of 0.5 g/ ^mm² to 5 g/ ^mm² during the heat treatment so as to sandwich the W source and the Cu source. This allows each material to be brought into close contact, thereby further improving the production efficiency of the W-Pt-Cu alloy.

Furthermore, in another embodiment of the manufacturing method disclosed herein, an intermediate metal member is interposed between the Pt-W alloy and the Cu source. While the embodiments described above involve direct contact between the Pt-W alloy and the Cu source, the manufacturing method disclosed herein is not limited to such embodiments. Experiments conducted by the inventors have shown that even when another metal member (intermediate metal member) is interposed between the Pt-W alloy and the Cu source, the migration of platinum (Pt) from the Pt-W alloy to copper (Cu) occurs, resulting in the formation of a W-Pt-Cu alloy.

Furthermore, even in the embodiment where the intermediate metal member described above is interposed, it is preferable to heat the Pt-W alloy, the intermediate metal member, and the Cu source that are in contact. This promotes the movement of Pt from the Pt-W alloy to Cu, thereby improving the efficiency of W-Pt-Cu alloy formation.

Furthermore, in the embodiment in which the aforementioned intermediate metal member is interposed, it is preferable that the intermediate metal member contains at least Pt. This further facilitates the migration of Pt from the Pt-W alloy to Cu, thereby further improving the efficiency of W-Pt-Cu alloy formation.

Next, alloy materials are provided as another aspect of the technology disclosed herein. The alloy materials disclosed herein are characterized by having a mixture of a W phase mainly composed of tungsten (W) and a Pt-Cu phase having platinum (Pt) and copper (Cu).
Because the interface between the W phase and the Pt-Cu phase of this alloy material is stable, it can exhibit suitable bonding properties to W members. On the other hand, because the Pt-Cu phase is present in this alloy material, it can also exhibit suitable bonding properties to dissimilar metal members (Cu members, Pt members, etc.). For this reason, the alloy material disclosed herein can be used as a bonding material for joining W members and dissimilar metal members. Furthermore, because this alloy material contains W, a high-melting-point metal, it is expected to exhibit superior heat resistance compared to conventional brazing materials. Moreover, since this alloy material is expected to have a coefficient of thermal expansion close to that of W members, it is also expected to suppress deterioration of the joint due to stress caused by differences in expansion and contraction.

Furthermore, in a preferred embodiment of the alloy material disclosed herein, multiple W phases are present within a matrix consisting of Pt-Cu phases. By adopting a structure in which W phases and Pt-Cu phases are mixed throughout the entire microstructure of the alloy material, more favorable bonding properties can be achieved for both tungsten members and dissimilar metal members.

Furthermore, in one preferred embodiment of the alloy material disclosed herein, SEM observation reveals a W-phase-existing region where W-phase particles with an area of 0.001 ^μm² to 1 ^μm² (preferably 0.001 ^μm² to 0.1 ^μm² ) exist at a density of 0.2 locations/ ^μm² or more, and this W-phase-existing region extends for 10 μm or more in a predetermined direction. Thus, an alloy material having a W-phase-existing region with a length of 10 μm or more where W-phase particles exist at a density above a certain level can exhibit more suitable bonding properties to W members.

In one preferred embodiment of the alloy material disclosed herein, when the total number of metallic elements present in the W phase is 100 atm%, the number of tungsten atoms present in the W phase is 75 atm% or more. This makes it possible to obtain an alloy material that exhibits high bonding properties to tungsten members.

Furthermore, as another aspect of the technology disclosed herein, a joint is provided. Such a joint is characterized in that a first member containing tungsten and a second member are joined via the W-Pt-Cu alloy material. As described above, the W-Pt-Cu alloy material can be suitably used as a joining material for metal members containing tungsten (W members).

In one preferred embodiment of the joint disclosed herein, the first member is characterized by comprising at least one material selected from the group consisting of tungsten, tungsten nitride, tungsten carbide, tungsten carbonitride, copper-tungsten composite material, and silver-tungsten composite material. The alloy material disclosed herein can exhibit suitable bonding properties to the first member made of the W-type material described above.

In one preferred embodiment of the joint disclosed herein, the second member is characterized by comprising at least one selected from the group consisting of copper, platinum, platinum-copper alloy, platinum-tungsten alloy, and copper alloy. The alloy material disclosed herein exhibits particularly suitable bonding properties for dissimilar metal members containing at least one of Cu, Pt, and W, as described above. Furthermore, the second member of the joint disclosed herein is not limited to the dissimilar metal members described above, but may be the same tungsten member as the first member. That is, the W-Pt-Cu alloy material disclosed herein can be used not only for bonding tungsten members to dissimilar metal members, but also for bonding tungsten members to each other.

This is a schematic cross-sectional view showing an alloy material according to one embodiment. This is a schematic cross-sectional view showing a joint according to one embodiment. This is a cross-sectional SEM image of sample A-1 used for analysis. (a) is the elemental map of W based on EDX analysis of sample A-1 for analysis, and (b) is the elemental map of Pt. (a) is the EDX spectrum in region α in Figure 3(b), and (b) is the EDX spectrum in region β. This is a graph showing the concentration distribution of W and Pt along the line segment X in Figure 3(b). (a) is an image showing the results of electron diffraction in region α in Figure 3(b), and (b) is an image showing the results of electron diffraction in region β. (a) and (b) are images of the crystal structure of the sample A-1 analyzed using EBSD, and (c) is an image of (b) with the tungsten and _Pt2W components separated and colored. (a) shows the grain size distribution in the W plate of the sample A-1 used for analysis, and (b) shows the grain size distribution in the Pt-W alloy. (a) and (b) are cross-sectional SEM images of sample A-2 used for analysis. (a) is an image of the crystal structure of sample A-2 analyzed using EBSD, and (b) is an image of (a) separated into the W phase and the Pt-Cu phase and colored. (c) is an image showing the crystal orientation of the crystal grains of the Pt-Cu phase in (b), and (d) is an image showing the crystal orientation of the crystal grains of the W phase in (b). (a) shows the particle size distribution in the Pt-Cu phase of the sample A-2 used for analysis, and (b) shows the particle size distribution in the W phase. (a) is a cross-sectional SEM image (250x magnification) of sample 1, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (1000x magnification) of sample 1, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (10,000x magnification) of sample 1, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 1, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. This is an SEM image showing the region where elemental analysis was performed on sample 1. These are SEM images of Sample 1, where (a) shows the boundary between the Cu member and the W member, and (b) and (c) are magnified images of the boundary area. This figure shows the results of the HAADF-STEM image and elemental mapping image for Sample 1. Figure 19 shows the EDX spectrum of the W-Pt-Cu alloy. This is the W-phase EDX spectrum from the HAADF-STEM image of Sample 1. This is the EDX spectrum of the Pt-Cu phase in the HAADF-STEM image of Sample 1. (a) is a cross-sectional SEM image (5000x magnification) of sample 2, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 2, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. This graph shows the concentration distributions of W, Pt, and Cu along line segment X1 in Figure 23(b). In the figure, (a) shows the analysis results for Pt, (b) shows the analysis results for W, and (c) shows the analysis results for Cu. (a) is a cross-sectional SEM image (5000x magnification) of sample 3, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 3, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (200,000x magnification) of sample 3, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of sample 4, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the Pt-Cu layer of sample 4, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the Pt-W layer of sample 4, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the W-Pt-Cu layer of sample 4, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the tungsten component of sample 4, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. This graph shows the concentration distributions of W, Pt, and Cu along line segment X2 in Figure 29(a). In the figure, (a) shows the analysis results for Pt, (b) shows the analysis results for W, and (c) shows the analysis results for Cu. (a) is a backscattered electron image of sample 4 (5000x magnification), (b) is a magnified view of region α in (a) (20000x magnification), and (c) is a magnified view of region β in (a) (20000x magnification). (a) is a cross-sectional SEM image (20,000x magnification) of region α of sample 4, and (b) to (d) are elemental maps of Cu, Pt, and W based on EDX analysis, respectively. (a) is a cross-sectional SEM image (20,000x magnification) of region β of sample 4, and (b) to (d) are elemental maps of Cu, Pt, and W based on EDX analysis, respectively. This figure shows the results of the HAADF-STEM image and elemental mapping image for sample 4. This graph shows the concentration distributions of Pt, Cu, and W along line segment X3 in Figure 38. This figure shows the results of HAADF-STEM images and elemental mapping images at the interface between the W plate of Sample 4, the W phase of the W-Pt-Cu layer, and the Pt-Cu phase of the W-Pt-Cu layer. This graph shows the concentration distributions of Pt, Cu, and W along line segment X4 in Figure 40. This graph shows the concentration distribution of O and Fe along line segment X4 in Figure 40. (a) is an image showing the results of electron diffraction in region α in Figure 38(a), (b) is an image showing the results of electron diffraction in region β, (c) is an image showing the results of electron diffraction in region γ, and (d) is an image showing the results of electron diffraction in region δ. This figure shows the results of the HAADF-STEM image and elemental mapping image on the W plate of sample 4. This figure shows the results of the HAADF-STEM image and elemental mapping image of the Pt-W layer in sample 4. This figure shows the results of the HAADF-STEM image and elemental mapping image of the Pt-Cu layer in sample 4. Figure 44 shows the EDX spectrum in the Pt-Cu region. Figure 40 shows the EDX spectrum in the Pt-Cu region. Figure 45 shows the EDX spectrum in the Pt-Cu region. Figure 46 shows the EDX spectrum in the Pt-Cu region. (a) is a cross-sectional SEM image (5000x magnification) of sample 5, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 5, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of sample 6, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 6, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of sample 7, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the Pt-W layer of sample 7, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the W-Pt-Cu layer of sample 7, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the W plate of sample 7, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the interface between the W plate and the W-Pt-Cu layer of sample 7, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of the uncoated Cu portion of sample 8, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the uncoated Cu portion of sample 8, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of the Cu-coated area of sample 8, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the W-Pt-Cu layer formed on the Cu-coated portion of sample 8, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the W-Pt-Cu layer formed on the Cu-coated portion of sample 8, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of the boundary between the W-Pt-Cu layer formed on the Cu coated portion of sample 8 and the W plate, and (b) to (d) are elemental maps of W, Cu, and Pt based on EDX analysis, respectively. (a) is a cross-sectional SEM image (250x magnification) of sample 9, and (b) to (d) are elemental maps of O, Cu, and W based on EDX analysis, respectively. (a) is a cross-sectional SEM image (1000x magnification) of sample 9, and (b) to (d) are elemental maps of O, Cu, and W based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of sample 9, and (b) to (d) are elemental maps of O, Cu, and W based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 9, and (b) to (d) are elemental maps of O, Cu, and W based on EDX analysis, respectively. (a) is a cross-sectional SEM image (5000x magnification) of sample 10, (c) is an elemental map of W based on EDX analysis, and (d) is an elemental map of Pt. This is a cross-sectional SEM image (5000x magnification) of sample 11. This is a cross-sectional SEM image (50,000x magnification) of sample 11. (a) is a cross-sectional SEM image (5000x magnification) of sample 12, and (b) to (e) are elemental maps of W, Cu, Pt, and Au based on EDX analysis, respectively. (a) is a cross-sectional SEM image (50,000x magnification) of sample 12, and (b) to (e) are elemental maps of W, Cu, Pt, and Au based on EDX analysis, respectively.

The following describes one embodiment of the technology disclosed herein. Matters other than those specifically mentioned herein, but necessary for implementing the technology disclosed herein, can be understood as design matters for those skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed herein and common technical knowledge in the relevant field. In this specification, when "A to B (A and B are numerical values)" is used, it means "A or greater and B or less."

1. Alloy Material Figure 1 is a schematic cross-sectional view showing the alloy material according to this embodiment. As shown in Figure 1, the alloy material (W-Pt-Cu alloy) 10 according to this embodiment is a ternary two-phase alloy material in which the W phase 12 and the Pt-Cu phase 14 are mixed (see Figure 1). The following describes each phase included in the alloy material 10 according to this embodiment.

(1) W phase The W phase 12 is a phase mainly composed of tungsten. In this specification, "mainly composed of tungsten" means that elements other than tungsten are not intentionally included. Therefore, a phase that contains unavoidable impurities (metal elements other than W) derived from raw materials or manufacturing processes as minor components is included in the concept of "W phase" in this specification. For example, if the total number of metal elements in one phase of a two-phase alloy is 100 atm%, and the number of W atoms in that one phase is 75 atm% or more, then it can be said that "a W phase mainly composed of tungsten has been formed." In addition, from the viewpoint of improving the bonding between the alloy material 10 and the W member according to this embodiment, the number of W atoms in the W phase is preferably 77.5 atm% or more, more preferably 80 atm% or more, and particularly preferably 82.5 atm% or more. The upper limit of the number of W atoms in the W phase is not particularly limited and may be 99.5 atm% or less, 97.5 atm% or less, 95 atm% or less, 92.5 atm% or less, or 90 atm% or less. In this specification, "number of atoms" is a numerical value based on elemental analysis obtained by performing energy dispersive X-ray spectroscopy (EDX) on cross-sectional SEM images of the alloy material.

Inevitably, possible impurities in phase W 12 include copper (Cu), platinum (Pt), molybdenum (Mo), iron (Fe), cobalt (Co), nickel (Ni), gold (Au), and thorium (Th). Furthermore, tungsten in phase W 12 may exist as a pure metal, as a compound (oxide, etc.), or as an alloy with other metallic elements.

(2) Pt-Cu phase The Pt-Cu phase 14 is a phase having platinum (Pt) and copper (Cu). The Pt-Cu phase 14 only needs to contain Pt and Cu, and there is no intention to exclude the inclusion of a third metallic element other than Pt and Cu. Furthermore, the Pt-Cu phase 14 does not need to have Pt and Cu as its main components, and the above-mentioned third metallic element may be the main component. As will be described in detail later, depending on the materials and manufacturing method used when manufacturing the alloy material 10, a third metallic element other than Pt and Cu can also be the main component of the Pt-Cu phase 14. Specifically, when the total number of metal atoms in the Pt-Cu phase is set to 100 atm%, the total number of Pt atoms and Cu atoms may be 20 atm% or more, 30 atm% or more, or 40 atm% or more. Furthermore, considering the bonding properties with copper members, the total number of Pt and Cu atoms is preferably 50 atm% or more, more preferably 65 atm% or more, even more preferably 75 atm% or more, and particularly preferably 85 atm% or more. On the other hand, the upper limit of the total number of Pt and Cu atoms in the Pt-Cu phase is not particularly limited and may be 99.5 atm% or less, 99 atm% or less, 97.5 atm% or less, or 95 atm% or less. The third metallic element that may be included in the Pt-Cu phase 14 is W, Mo, Fe, Pd, Ir, Au, Co, Ni, Zn, Al, Sn, Pb, Mn, Ag, Th, etc. Among these third metallic elements, those that form alloys with Cu more readily than W (for example, Au, Co, Ni, Zn, Al, Sn, Pb, Mn, Ag, Th, etc.) can become the main components of the Pt-Cu phase 14.

Furthermore, there are no particular limitations on the number of Pt and Cu atoms present in the Pt-Cu phase. For example, the number of Pt atoms in the Pt-Cu phase may be 0.1 atm% or more, 0.5 atm% or more, or 1 atm% or more. On the other hand, the upper limit of the number of Pt atoms may be 25 atm% or less, 22.5 atm% or less, 20 atm% or less, or 17.5 atm% or less. Also, the number of Cu atoms in the Pt-Cu phase may be 15 atm% or more, 20 atm% or more, 30 atm% or more, or 40 atm% or more. Considering the bonding properties with copper members, the number of Cu atoms is preferably 50 atm% or more, more preferably 65 atm% or more, even more preferably 75 atm% or more, and particularly preferably 80 atm% or more. On the other hand, the upper limit of the number of Cu atoms may be 85 atm% or less, 82.5 atm% or less, or 80 atm% or less. As mentioned above, the number of Pt and Cu atoms present in the Pt-Cu phase is not particularly limited. For example, by contacting the alloy material 10 with a Cu component, Pt can be diffused into the Cu component, thereby reducing the number of Pt atoms in the alloy material 10. Similarly, by contacting the alloy material 10 with a component capable of diffusing Cu (e.g., Au, Ni), the number of Cu atoms in the alloy material 10 can be reduced.

(3) Microstructure of the Alloy Material Next, the microstructure of the alloy material 10 according to this embodiment will be described. As shown in Figure 1, the alloy material 10 according to this embodiment is a ternary two-phase alloy in which the W phase 12 and the Pt-Cu phase 14 described above are mixed. That is, in the alloy material 10 according to this embodiment, the W phase 12 and the Pt-Cu phase 14 exist mixed together throughout the entire metallic structure. Typically, in this alloy material 10, a matrix made of the Pt-Cu phase 14 is formed, and a plurality of W phases 12 exist in the matrix of the Pt-Cu phase 14. In this way, in the alloy material 10 according to this embodiment, the interface between the W phase 12 and the Pt-Cu phase 14 is stable, so it can exhibit high bonding properties to W members, while having the Pt-Cu phase 14, it can exhibit suitable bonding properties with dissimilar metal members (Cu members, Pt members, etc.). As an example of the alloy material (W-Pt-Cu alloy) disclosed herein, there is a form in which multiple elongated island-shaped W phases are scattered so as to extend in the thickness direction, and Pt-Cu phases are formed to fill the spaces between these multiple W phases (see, for example, Figures 16(a) and 19). However, the shape of the W phase is not limited to the elongated island shape described above, and may be substantially spherical (see, for example, Figure 52(a)).

The alloy material disclosed herein is not limited to a form in which multiple W phases are scattered throughout the entire alloy material. For example, W phases may be present at a certain density or higher in a specific region of the Pt-Cu phase (see Figure 73(a)). In this specification, the region in which W phases exist at a certain density or higher is referred to as the "W phase presence region." More specifically, the "W phase presence region" in this specification is a region in which W phases with an area of 0.001 ^μm² to 1 ^μm² (preferably 0.001 ^μm² to 0.1 ^μm² ) are present at a density of 0.2 locations/μm² or more in the Pt-Cu phase within the range of ^{1 μm²} , as observed by SEM. By having such a W phase presence region of 10 μm or more in a predetermined direction, suitable bonding properties can be achieved for both the W member and the dissimilar metal member. The "direction in which the W phase presence region exists" is not particularly limited. In other words, if a region where the W phase is densely packed to a certain extent exists for 10 μm or more in at least one direction (for example, the thickness direction, width direction, or depth direction), an alloy material can be obtained that exhibits suitable bonding properties to both tungsten members and dissimilar metal members. As mentioned above, a density of 0.2 locations/ ^μm² in the W phase region is appropriate. However, considering bonding properties with W members, a density of 0.3 locations/ ^μm² or more in the W phase region is more appropriate, and 0.5 locations/ ^μm² or more is even more appropriate. Furthermore, from the viewpoint of further improving bonding properties with W members, a density of 0.5 locations/ ^μm² or more in the W phase region is preferable, 1 location/ ^μm² or more is more preferable, 1.5 locations/μm² or more is even more preferable, and ² locations/ ^μm² or more is particularly preferable. On the other hand, considering the bonding properties with dissimilar metal members (such as Cu members), the density of the W phase in the W phase-present region is suitable to be 100 locations/ ^μm² or less, preferably 50 locations/ ^μm² or less, more preferably 10 locations/ ^μm² or less, even more preferably 7.5 locations/ ^μm² or less, particularly preferably 5 locations/ ^μm² or less, and can be, for example, 4 locations/ ^μm² or less.

Furthermore, the average area of each W phase is preferably ¹ μm² or less, more preferably 0.75 ^μm² or less, even more preferably 0.5 ^μm² or less, and particularly preferably 0.25 ^μm² or less. The presence of such minute W phases in the Pt-Cu phase matrix allows for more favorable bonding properties to both tungsten members and dissimilar metal members. The lower limit of the average area of the W phase is not particularly limited and may be 0.001 ^μm² or more, 0.005 ^μm² or more, 0.01 ^μm² or more, or 0.05 ^μm² or more. The "average area of the W phase" can be obtained by extracting 50 or more (preferably 85) W phases confirmed by SEM observation and calculating the average value of the areas of the extracted W phases.

Furthermore, it is preferable that the crystal grains constituting the W phase be fine. For example, the _D50 particle diameter of the crystal grains constituting the W phase is preferably 1000 nm or less, more preferably 900 nm or less, even more preferably 800 nm or less, and particularly preferably 700 nm or less. On the other hand, the lower limit of the _D50 particle diameter of the crystal grains of the W phase is not particularly limited and may be 100 nm or more, 200 nm or more, 300 nm or more, or 400 nm or more. On the other hand, it is also preferable that the crystal grains constituting the Pt-Cu phase be fine. For example, the _D50 particle diameter of the crystal grains constituting the Pt-Cu phase is preferably 800 nm or less, more preferably 600 nm or less, even more preferably 400 nm or less, and particularly preferably 200 nm or less. On the other hand, the lower limit of the _D50 particle diameter of the crystal grains of the Pt-Cu phase is not particularly limited and may be 20 nm or more, 40 nm or more, 60 nm or more, or 80 nm or more. Because the W phase and Pt-Cu phase are each composed of such fine crystal grains, the W phase and Pt-Cu phase can be suitably mixed, thereby improving the bonding strength between the W member and the dissimilar metal member. When comparing the relative sizes of the crystal grains of the W phase and the Pt-Cu phase, it is preferable that the W phase is composed of relatively large crystal grains and the Pt-Cu phase is composed of relatively minute crystal grains. In this specification, "D ₅₀ particle diameter of crystal grain" refers to the cumulative 50% from the fine particle side in the particle size distribution of crystal grains based on the number of grains. Furthermore, "crystal grain particle diameter" is the "equivalent circular diameter of crystal grain" obtained by performing crystal analysis using electron backscatter diffraction (EBS) on SEM images of the alloy material.

2. Joint Next, a joint formed by joining two types of members using the alloy material 10 described above will be explained. Figure 2 is a schematic cross-sectional view showing the joint according to this embodiment. In such a joint 100, a first member (W member) 20 containing tungsten and a second member 30 are joined via the alloy material 10 described above. As described above, in the alloy material 10 according to this embodiment, the interface between the W phase and the Pt-Cu phase is stable, so it can exhibit suitable bonding properties to the W member 20. On the other hand, since the Pt-Cu phase 14 is present throughout the entire structure of the alloy material 10, it can also bond suitably to dissimilar metal members that are suitably bonded to Pt-Cu alloys. For this reason, the alloy material 10 disclosed herein functions as a bonding material for joining the first member (W member) 20 and the second member 30.

Furthermore, because this alloy material 10 contains W, a high-melting-point metal, it exhibits superior heat resistance compared to conventional brazing materials. Moreover, since this alloy material 10 has a thermal expansion coefficient close to that of the W member 20, it can suppress damage to the joint (alloy material 10) caused by large stresses resulting from differences in expansion and contraction. Therefore, the jointed body 100 joined with this alloy material 10 is particularly promising for use in ultra-high-temperature components such as divertors, accelerators, plasma discharge devices, high-temperature furnaces, and thin-film deposition devices.

The first member (W member) 20 is not particularly limited as long as it is a solid metal member containing W. Examples of materials for such W member 20 include tungsten, tungsten nitride, tungsten carbide, tungsten carbonitride, copper-tungsten alloy, and silver-tungsten alloy. Furthermore, the first member (i.e., W member) in this specification is not limited to a member consisting solely of the above-mentioned tungsten material, but may be a composite material formed by combining tungsten material with other materials. Examples of materials that can be combined with tungsten material include various metallic materials such as copper (Cu), platinum (Pt), molybdenum (Mo), iron (Fe), cobalt (Co), nickel (Ni), gold (Au), and thorium (Th), as well as high-melting-point ceramics such as tria ( _ThO₂ ) and yttria. For the sake of explanation, Figure 2 shows a plate-shaped W member 20, but the shape of the W member is not particularly limited. For example, the shape of the W member can be any common metal member shape, such as cylindrical or columnar, without any particular restrictions.

On the other hand, the second member 30 is not particularly limited as long as it is a member that can be suitably joined with the alloy material (W-Pt-Cu alloy) 10, and various members can be used without particular restriction. A suitable example of such a second member 30 is a dissimilar metal member whose main component is a metal element other than tungsten. An example of such a dissimilar metal member is a metal member containing Cu or Pt. Specific examples of such dissimilar metal members include Cu members, Pt members, and Pt-Cu alloy members. Furthermore, the dissimilar metal member may be a metal member that has good bonding properties to Cu or Pt (such as a Ni member or a Co member). Note that the material of the second member 30 can be appropriately changed according to the main component of the Pt-Cu phase 14 of the alloy material 10, and is not limited to the metal members that have good bonding properties to Cu or Pt as described above. For example, in the manufacturing of alloy materials described later, a Pt-Cu phase 14 containing a third metal element (e.g., Au, Ni, Zn, etc.) other than Pt or Cu can be formed by mixing it into a Cu source. When such a Pt-Cu phase 14 containing a third metal element is formed, metal members with good bonding compatibility with the third metal element can be used for the second member 30. For example, when a Pt-Cu phase 14 containing Au is formed, in addition to the Cu member, Pt member, and Pt-Cu alloy member, Au members, Ag members, etc., can be used as bonding targets. Furthermore, the term "dissimilar metal member" in this specification refers to a metal member whose main component is a metal element other than tungsten, and does not exclude metal members containing W as a minor component. That is, the dissimilar metal member may also be an alloy containing tungsten.

Furthermore, the second member 30 is not limited to dissimilar metal members as described above. For example, the alloy material 10 disclosed herein is not limited to joining a W member to a dissimilar metal member, but can also be used as a joining material to join W members to each other. That is, the second member 30 may be the same type of W member as the first member 20 described above (for example, tungsten, tungsten nitride, tungsten carbide, tungsten carbonitride, etc., and composite materials containing these). Generally, W members are difficult to weld directly because they have a high melting point. However, by using the alloy material disclosed herein, W members can be easily joined to each other. Furthermore, the second member 30 does not have to be a metal member. For example, the second member 30 may be a ceramic such as toria ( _ThO₂ ), yttria, or glass. The alloy material 10 disclosed herein can exhibit suitable bonding properties even to such non-metallic members.

3. Method for Manufacturing Alloy Materials Next, a method for manufacturing the alloy materials disclosed herein will be described. The alloy materials disclosed herein can be manufactured by preparing a Pt-W alloy containing Pt and W and a Cu source containing copper (Cu) as precursor materials, and transferring Pt from the Pt-W alloy to the Cu source. As an example, such transfer of Pt from the Pt-W alloy to the Cu source occurs by bringing the Pt-W alloy and the Cu source into contact. Specifically, when the Pt-W alloy and the Cu source are brought into contact, Pt diffuses (moves) from the Pt-W alloy to the Cu source. At this time, since diffusion of Pt is likely to occur at the grain boundaries between the crystal grains of the Pt-W alloy and Cu, the diffusion of Pt proceeds while the crystal grains of the Pt-W alloy and Cu are finely mixed. As a result, a ternary two-phase alloy material (W-Pt-Cu alloy) is produced, which consists of a Pt-Cu phase containing Pt and Cu, and a W phase remaining after Pt removal from the Pt-W alloy.

Here, to manufacture a W-Pt-Cu alloy, it is sufficient to transfer Pt from a Pt-W alloy to Cu, and the specific procedure is not particularly limited. In other words, the method for manufacturing the alloy material disclosed herein encompasses multiple manufacturing methods with different specific procedures (steps). An example of the manufacturing method disclosed herein (the first embodiment) will be described below.

(1) First Embodiment The manufacturing method according to this embodiment comprises a Pt-W alloy formation step and a W-Pt-Cu alloy formation step. Each of these steps will be described below.

(a) Pt-W alloy formation process In this process, a Pt source containing platinum (Pt) and a W source containing tungsten (W) are brought into contact and subjected to heat treatment. This makes it easy to produce a Pt-W alloy, which is a precursor to a W-Pt-Cu alloy. The Pt-W alloy produced in this process is not particularly limited as long as it contains Pt and W. An example of such a Pt-W alloy is an intermetallic compound containing Pt and W in a predetermined integer ratio (for example, Pt ₂ W). Since the crystal grains of this type of intermetallic compound are very fine, by using it as a precursor to a W-Pt-Cu alloy, an alloy material in which the W phase and Pt-Cu phase are finely mixed can be produced. Specifically, the D ₅₀ particle size of the crystal grains of the Pt-W alloy is suitable to be 2000 nm or less, preferably 1500 nm or less, more preferably 1000 nm or less, even more preferably 500 nm or less, and particularly preferably 200 nm or less. On the other hand, the lower limit of the _D50 particle diameter of the crystal grains of the Pt-W alloy is not particularly limited and may be 40 nm or more, 60 nm or more, 80 nm or more, or 100 nm or more.

The W source used in this process can be any material containing the element W, and its detailed composition and form are not particularly limited. Examples of such W sources include powder materials containing tungsten particles, solid or solution compounds containing tungsten, and solid metal members containing tungsten. Since the material of such a W source is the same type as that of the first member (W member) 20 described above, a redundant explanation will be omitted. Furthermore, as will be described in more detail later, the manufacturing method disclosed herein allows for the production of the alloy material 10 (see Figure 1) alone, or for the production of the alloy material 10 attached to the W member 20 (see Figure 2). Although not intended to limit the manufacturing method disclosed herein, when producing the alloy material 10 alone, it is preferable to use a tungsten thin film with a thickness of 50 μm or less as the W source. This ensures that the entire W source is used to form the alloy material 10, thus allowing for the formation of a standalone alloy material 10 without any attached tungsten members. Such a tungsten thin film can be formed, for example, by chemical vapor deposition or physical vapor deposition. Furthermore, from the viewpoint of more reliably forming the single alloy material 10, the thickness of the tungsten thin film is more preferably 20 μm or less, even more preferably 10 μm or less, and particularly preferably 5 μm or less. Also, from the viewpoint of preventing poor formation of the Pt-W alloy due to a deficiency of W, the lower limit of the tungsten thin film thickness is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.5 μm or more, and particularly preferably 1 μm or more.

On the other hand, the Pt source can be any material containing the element Pt, and its detailed composition and form are not particularly limited. An example of such a Pt source is a Pt paste obtained by dispersing Pt powder in a predetermined solvent. A Pt-W alloy can be easily produced by applying such a Pt paste to the surface of a W source and then performing a heat treatment. Such a Pt paste is not particularly limited except that it contains Pt particles, and conventionally known Pt pastes can be used as long as they do not hinder the effects of the technology disclosed herein. As an example, the average particle diameter of the Pt particles in the paste is preferably 0.01 μm to 10 μm, more preferably 0.05 μm to 5 μm, particularly preferably 0.1 μm to 1.0 μm, and for example, 0.5 μm. In this specification, "average particle diameter" is the average value of the particle diameters of a plurality (e.g., 100) of particles measured based on SEM observation. Furthermore, when the total volume of the Pt paste is 100 vol%, the Pt particle content (volume ratio) is preferably 1 vol% or more, more preferably 2.5 vol% or more, even more preferably 5 vol% or more, and particularly preferably 7.5 vol% or more. This prevents poor formation of Pt-W alloy due to insufficient Pt. On the other hand, from the viewpoint of suppressing the increase in viscosity of the Pt paste and improving workability, the upper limit of the Pt particle content (volume ratio) is preferably 20 vol% or less, more preferably 17.5 vol% or less, even more preferably 15 vol% or less, and particularly preferably 12.5 vol% or less. When the total weight of the Pt paste is 100 wt%, the Pt particle content (weight ratio) is preferably 50 wt% or more, more preferably 55 wt% or more, even more preferably 60 wt% or more, and particularly preferably 65 wt% or more. On the other hand, the upper limit of the Pt particle content (by weight) is preferably 90 wt% or less, more preferably 85 wt% or less, even more preferably 80 wt% or less, and particularly preferably 75 wt% or less. Note that the components of the Pt paste other than the Pt particles (solvent, binder, dispersant, etc.) can be conventionally known components without particular limitation, as long as they do not hinder the effects of the disclosed technology, and therefore, detailed explanations are omitted as they do not characterize the disclosed technology.

Furthermore, from the viewpoint of preventing poor formation of the Pt-W alloy due to a lack of Pt, the coating thickness of the Pt paste in this process is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 40 μm or more. On the other hand, the upper limit of the coating thickness of the Pt paste is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 70 μm or less, and particularly preferably 60 μm or less. This prevents unreacted Pt from forming on the surface of the Pt-W alloy and hindering the reaction between the Pt-W alloy and the Cu source in the W-Pt-Cu alloy formation process described later. The coating thickness of the Pt paste can be easily controlled to the desired thickness by adjusting the thickness of the metal mask used during paste application.

Furthermore, the heating temperature in this process is preferably 750°C or higher, more preferably 800°C or higher, even more preferably 850°C or higher, and particularly preferably 900°C or higher. This improves the efficiency of Pt-W alloy formation. On the other hand, the upper limit of the heating temperature in this process is preferably 1250°C or lower, more preferably 1200°C or lower, even more preferably 1150°C or lower, and particularly preferably 1100°C or lower. Furthermore, the heating time in this process is preferably 0.5 hours or more, more preferably 1 hour or more. This allows for the proper formation of Pt-W alloy. On the other hand, from the viewpoint of manufacturing efficiency, the upper limit of the heating time in this process is preferably 5 hours or less, more preferably 4 hours or less, and particularly preferably 3 hours or less. In this specification, "heating temperature" refers to the maximum temperature during the heat treatment, and "heating time" refers to the time during which the maximum temperature is maintained. Furthermore, it is preferable to set the atmosphere during the heat treatment to a non-oxidizing atmosphere (neutral atmosphere, reducing atmosphere). Examples of reducing gases include hydrogen ( _H₂ ) gas and hydrocarbon gases (such as _CH₄ and _C₃H₄ ). An example of a neutral gas _is nitrogen ( _N₂ ) gas. Furthermore, mixtures of these reducing and neutral gases can also be used. For example, a mixed gas obtained by combining hydrogen ( _H₂ ) gas with nitrogen ( _N₂ ) gas at a concentration of 1% to 5% (e.g., 3%) can be used.

Furthermore, from the viewpoint of preventing damage (such as cracks) due to rapid volume changes during heat treatment, it is preferable to perform a drying treatment to dry the Pt paste before the heat treatment for forming the Pt-W alloy. The heating temperature in this drying treatment is preferably 60°C or higher, more preferably 80°C or higher, and particularly preferably 100°C or higher. On the other hand, from the viewpoint of preventing the cracks mentioned above, the upper limit of the heating temperature in the drying treatment is preferably 140°C or lower, more preferably 130°C or lower. The drying time is preferably 10 minutes to 60 minutes (for example, about 30 minutes).

Furthermore, if organic components such as binders are added to the Pt paste, a preheating treatment (binder removal treatment) may be performed to remove the organic components before the heat treatment for forming the Pt-W alloy. However, if the W source oxidizes and tungsten oxide is produced during this binder removal treatment, the formation of the Pt-W alloy may be inhibited. Therefore, the organic components (binders, etc.) added to the Pt paste are preferably resin materials (e.g., acrylic resin) that can be sufficiently decomposed by heating in a non-oxidizing atmosphere. From the viewpoint of reliably removing organic components, the heating temperature in the binder removal treatment is preferably 145°C or higher, more preferably 150°C or higher, even more preferably 155°C or higher, and particularly preferably 160°C or higher. On the other hand, to prevent the formation of the Pt-W alloy from progressing during the binder removal treatment, the upper limit of the heating temperature in the binder removal treatment is preferably 500°C or lower, more preferably 450°C or lower, even more preferably 400°C or lower, and particularly preferably 350°C or lower. Furthermore, the heating time in the binder removal process is preferably 0.5 hours or more, and more preferably 1 hour or more. This ensures reliable removal of organic components. On the other hand, from the viewpoint of manufacturing efficiency, the upper limit of the heating time in the binder removal process is preferably 5 hours or less, more preferably 4 hours or less, even more preferably 3 hours or less, and particularly preferably 2 hours or less.

(b) W-Pt-Cu alloy formation process In this process, a heat treatment is performed while the Cu source, which is a material mainly containing Cu, and the Pt-W alloy are in contact. This causes the movement of Pt from the Pt-W alloy to Cu (typically by diffusion) to proceed rapidly. At this time, the diffusion of Pt proceeds while the crystal grains of the Pt-W alloy and Cu become finely intermingled. On the other hand, W in the Pt-W alloy hardly dissolves with Cu. Therefore, de-Pt from the Pt-W alloy to Cu proceeds, and a W phase, in which W is the main component, is formed. Meanwhile, as Pt is supplied to Cu, a Pt-Cu phase is formed so as to fill the area around the W phase. Thus, according to the manufacturing method of this embodiment, a ternary two-phase alloy material (W-Pt-Cu alloy) in which W and Cu, which would not normally form an alloy, are mixed can be manufactured.

As mentioned above, when a Cu source and a Pt-W alloy are brought into contact, Pt moves (diffuses) from the Pt-W alloy to Cu, so a W-Pt-Cu alloy can be produced without heat treatment. However, when a W-Pt-Cu alloy production process involving heat treatment is carried out as in this embodiment, the diffusion of Pt to Cu proceeds rapidly, significantly improving the production efficiency of the W-Pt-Cu alloy. The maximum temperature in such heat treatment is preferably 750°C or higher, more preferably 800°C or higher, even more preferably 850°C or higher, and particularly preferably 900°C or higher. This more effectively promotes the diffusion of Pt, allowing for the efficient formation of the W-Pt-Cu alloy. On the other hand, the upper limit of the maximum firing temperature is preferably 1500°C or lower, more preferably 1400°C or lower, even more preferably 1300°C or lower, and particularly preferably 1200°C or lower. The firing time in this process is preferably 1 hour or more, and more preferably 1.5 hours or more. This allows for the formation of a W-Pt-Cu alloy in which the W phase and Pt-Cu phase are sufficiently mixed. On the other hand, from the viewpoint of manufacturing efficiency, the upper limit of the firing time in this process is preferably 3 hours or less, and more preferably 2.5 hours or less.

Furthermore, it is preferable to set the firing atmosphere in this process to a non-oxidizing atmosphere (e.g., a neutral atmosphere, an inert atmosphere, or a reducing atmosphere). Examples of reducing gases include hydrogen ( _H₂ ) gas and hydrocarbon gases ( _CH₄ , _C₃H₄ , _etc. ). Examples of inert gases include argon (Ar) gas, and examples of neutral gases include nitrogen ( _N₂ ) gas and ammonia. It is also possible to use a mixture of a reducing gas and an inert gas (or neutral gas). For example, a mixed gas obtained by mixing hydrogen gas with nitrogen gas at a concentration of 1% to 5% (e.g., 3%) can be used.

Furthermore, in this process, it is preferable to perform the firing process while applying a load of 0.5 g/ ^mm² or more (more preferably 1 g/ ^mm² or more, and particularly preferably 1.5 g/ ^mm² or more) so as to sandwich the Pt-W alloy and the Cu source. This prevents gaps from forming between the Cu source and the Pt-W alloy, and allows for more efficient formation of the W-Pt-Cu alloy. The upper limit of the load applied to the Pt-W alloy and the Cu source is not particularly limited and may be 10 g/ ^mm² or less, 8 g/ ^mm² or less, 6 g/ ^mm² or less, or 5 g/ ^mm² or less.

The Cu source used in this process can be any material containing Cu, and its composition is not particularly limited. Specifically, the Cu source is not limited to Cu and may contain other metallic elements. In this case, by mixing a third metallic element other than Pt or Cu into the Cu source, the Pt-Cu phase of the W-Pt-Cu alloy after production can be made to contain this third metallic element. This improves the bonding properties to dissimilar metal components whose main components are metallic elements other than Cu or Pt. Examples of third metallic elements that can be mixed into the Cu source include gold (Au), nickel (Ni), aluminum (Al), tin (Sn), zinc (Zn), silica (Si), iron (Fe), manganese (Mn), cobalt (Co), and beryllium (Be).

On the other hand, the shape of the Cu source is not particularly limited; it may be a solid metal component containing Cu (Cu component), or a Cu paste obtained by dispersing Cu powder in a solvent. For example, when manufacturing only the alloy material, it is preferable to use a copper paste applied to a certain thickness or less as the Cu source. This ensures that all of the Cu source is used for forming the alloy material, thus enabling the formation of a standalone alloy material without any attached copper components. Alternatively, instead of copper paste, a thin copper film may be formed, for example, by chemical vapor deposition. From the viewpoint of reliably forming a standalone alloy material, the thickness of the Cu source is preferably 100 μm or less, more preferably 80 μm or less, even more preferably 70 μm or less, and particularly preferably 60 μm or less. On the other hand, from the viewpoint of preventing poor formation of the W-Pt-Cu alloy due to insufficient Cu, the lower limit of the Cu source thickness is preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and particularly preferably 40 μm or more.

When using Cu paste as the Cu source, the average particle size of the Cu particles in the paste is preferably 0.01 μm to 10 μm, more preferably 0.1 μm to 5 μm, and particularly preferably 0.5 μm to 2 μm, for example, 1 μm. Furthermore, the Cu particle content (volume ratio) when the total volume of the Cu paste is 100 vol% is preferably 5 vol% or more, more preferably 10 vol% or more, even more preferably 15 vol% or more, and particularly preferably 20 vol% or more. This prevents poor formation of the Pt-W alloy due to a lack of Cu. On the other hand, from the viewpoint of suppressing the increase in viscosity of the copper paste and improving workability, the upper limit of the Cu particle content (volume ratio) is preferably 55 vol% or less, more preferably 50 vol% or less, even more preferably 45 vol% or less, and particularly preferably 40 vol% or less. Furthermore, when the total weight of the Cu paste is 100 wt%, the Cu particle content (by weight) is preferably 60 wt% or more, more preferably 65 wt% or more, even more preferably 70 wt% or more, and particularly preferably 75 wt% or more. On the other hand, the upper limit of the Cu particle content (by weight) is preferably 95 wt% or less, more preferably 90 wt% or less, and particularly preferably 85 wt% or less. Regarding the components of the Cu paste other than the Cu particles (solvent, binder, dispersant, etc.), conventionally known components can be used without particular limitation as long as they do not hinder the effects of the disclosed technology, and since they do not characterize the disclosed technology, a detailed explanation is omitted. Also, as mentioned above, when adding a third metal element to the Cu source, it is preferable to add the powder form of the third metal element to the Cu paste. This allows for easy addition of the third metal element to the Cu source.

(2) Second Embodiment Next, another example (second embodiment) of the method for manufacturing the alloy material disclosed herein will be described.

In the first embodiment described above, a W-Pt-Cu alloy is produced by performing two or more heat treatments, including a Pt-W alloy formation step and a W-Pt-Cu alloy formation step. However, the manufacturing method disclosed herein is not limited to the above embodiment. For example, experiments have confirmed that a W-Pt-Cu alloy can be produced even when a Pt source is interposed between a W source and a Cu source and the heat treatment is performed together. Specifically, as in this embodiment, when a W source, a Pt source, and a Cu source are heated together, a Pt-W alloy is formed at the boundary between the W source and the Pt source. As the heat treatment progresses further, the Pt-W alloy and Cu (including the Pt-Cu alloy) become finely intermingled, and the Pt in the Pt-W alloy moves to Cu. As a result, a W-Pt-Cu alloy is formed between the W source and the Cu source, in which the W phase and the Pt-Cu phase are mixed. Furthermore, from the viewpoint of reliably manufacturing the W-Pt-Cu alloy, it is preferable to perform the Pt-W alloy production process beforehand to reliably produce the precursor material (Pt-W alloy), as in the first embodiment described above, before producing the W-Pt-Cu alloy. On the other hand, considering manufacturing efficiency and cost, it is preferable to produce the Pt-W alloy and the W-Pt-Cu alloy simultaneously, as in this embodiment.

Furthermore, the heat treatment temperature in this embodiment is preferably 750°C or higher, more preferably 800°C or higher, even more preferably 850°C or higher, and particularly preferably 900°C or higher. This more effectively promotes the diffusion of Pt, allowing for efficient formation of the W-Pt-Cu alloy. On the other hand, the upper limit of the maximum firing temperature is preferably 1500°C or lower, more preferably 1400°C or lower, even more preferably 1300°C or lower, and particularly preferably 1200°C or lower. The firing time in this step is preferably 1 hour or more, and more preferably 1.5 hours or more. This allows for the formation of a W-Pt-Cu alloy in which the W phase and Pt-Cu phase are sufficiently mixed. On the other hand, from the viewpoint of manufacturing efficiency, the upper limit of the firing time in this step is preferably 3 hours or less, and more preferably 2.5 hours or less.

Furthermore, in this embodiment, it is preferable to perform the firing process while applying a load of 0.5 g/ ^mm² or more (more preferably 1 g/ ^mm² or more, and particularly preferably 1.5 g/ ^mm² or more) to sandwich the W source and Cu source during the heat treatment described above. This prevents gaps from forming between each of the Cu source, Pt source, and W source components, and allows for more efficient formation of the W-Pt-Cu alloy. The upper limit of the load applied when sandwiching each component is not particularly limited and may be 10 g/ ^mm² or less, 8 g/ ^mm² or less, 6 g/ ^mm² or less, or 5 g/ ^mm² or less.

4. Other Embodiments An embodiment of the technology disclosed herein has been described above. However, the above-described embodiment is not intended to limit the technology disclosed herein, and various modifications can be made.

For example, the various conditions described in each of the embodiments above are examples of conditions for manufacturing alloy materials alone and are not intended to limit the technology disclosed herein. Depending on the shape and state of the target alloy material, various conditions such as the W source, Cu source, Pt source, firing temperature, and firing time can be appropriately adjusted. As a specific example, in the embodiments described above, W paste or a W thin film is used as the W source and Cu paste or a Cu thin film is used as the Cu source to manufacture the alloy material alone. However, by using a tungsten member having a predetermined thickness as the W source, it is possible to manufacture an alloy material joined to the tungsten member. This configuration is preferable from the viewpoint of work efficiency, as the manufacturing of the alloy material and the joining process between the alloy material and the tungsten member can be carried out simultaneously. Furthermore, if the thickness of the tungsten member is 0.1 mm or more (preferably 0.2 mm or more, more preferably 0.3 mm or more), the tungsten member remains even after the W-Pt-Cu alloy is formed, thus allowing for the acquisition of an alloy material joined to the tungsten member.

Similarly, when the dissimilar metal members to be joined are copper (Cu) members, using a copper member with a predetermined thickness as the Cu source allows for the production of an alloy material joined to the copper member (dissimilar metal member), which is preferable from the viewpoint of work efficiency, etc. Furthermore, if the thickness of the copper member is 0.1 mm or more (preferably 0.2 mm or more, more preferably 0.3 mm or more), the copper member remains even after the W-Pt-Cu alloy is formed, allowing for the production of an alloy material joined to the copper member.

Furthermore, by using a tungsten member of a predetermined thickness as the W source and a copper member of a predetermined thickness as the Cu source, a joint can be manufactured in which the W member and the Cu member are joined via a W-Pt-Cu alloy. This manufacturing method allows for the efficient production of the desired joint. It should be noted that the joint manufactured in this way does not necessarily have to be composed entirely of the W-Pt-Cu alloy formed between the W member and the Cu member. For example, a Pt-W alloy may be formed in the region of the alloy material on the W member side, or a Pt-Cu alloy may be formed in the region on the Cu member side.

Furthermore, in each of the embodiments described above, the Pt-W alloy and the Cu source are in direct contact. However, the manufacturing method disclosed herein is not limited to these embodiments, and the Pt-W alloy and the Cu source may be brought into contact with other metal members (intermediate metal members) interposed between them. The inventors have experimentally confirmed that even in such cases, the movement of Pt from the Pt-W alloy to Cu occurs, and a W-Pt-Cu alloy is formed. An example of such an intermediate metal member is a metal member containing Pt. Preferably, the intermediate metal member is a metal member that diffuses the Cu component. For example, metals or alloys other than Pt that can alloy (especially solid solution) with Cu can be used. Specific examples of intermediate metal members include metal members containing Ni, Au, Sn, Zn, etc., and copper alloys. Among these, Ni, Au, and Pt, which can form a complete solid solution with Cu, are particularly suitable as intermediate metal members. Also, as with the embodiments described above, it is preferable to perform heat treatment even when an intermediate metal member is interposed. This promotes the migration of Pt from the Pt-W alloy to Cu. The heat treatment conditions can be set to the same extent as in the embodiment described above, so a redundant explanation is omitted.

Furthermore, in the embodiments described above, the alloy material disclosed herein is used as a bonding material between a tungsten member and a dissimilar metal member. However, the alloy material disclosed herein is not limited to bonding materials and is expected to have applications in various fields. Other examples of applications of the alloy material disclosed herein include barrier films that protect the surface of metal members (e.g., W members) and catalysts. Also, of the W phase and Pt-Cu phase constituting the alloy material disclosed herein, the Pt-Cu phase is more easily soluble in acid. Therefore, by manufacturing an alloy material in which a very fine W phase exists in the matrix of the Pt-Cu phase, and dissolving the Pt-Cu phase of this alloy material in acid, very fine tungsten particles can be produced. In other words, the alloy material disclosed herein can also be used for the production of tungsten particles.

[Example Test]
The following describes test examples relating to the present invention, but these test examples are not intended to limit the present invention.

A. First Test In this test, as in the first embodiment described above, a W-Pt-Cu alloy was manufactured by performing a Pt-W alloy production process and a W-Pt-Cu alloy production process. Various analyses were then performed in each process to investigate the formation mechanism of the W-Pt-Cu alloy.

1. Pt-W Alloy Formation Process First, a Pt paste was prepared by mixing Pt powder with an average particle size of 0.5 μm, a binder (acrylic resin), and a solvent (IBA: isobutyl alcohol). The Pt powder content relative to the total weight of the Pt paste was set to 70 wt% (10 vol%) by volume. Next, this Pt paste was applied to the surface of a tungsten plate (W plate) using a metal mask (thickness 50 μm × 20 mm × 20 mm). Next, a drying treatment (drying temperature: 120°C, drying time: 30 minutes) was performed to dry the Pt paste on the surface of the W plate. Then, the W plate with the dried Pt paste attached was subjected to a heat treatment to obtain sample A-1 for analysis. The atmosphere during the heat treatment was set to a reducing atmosphere ( _N2 - _H2 (3%) gas). Furthermore, in this process, the heat treatment was carried out under the conditions of heating to 400°C at a heating rate of 4°C/min and holding for 1 hour, followed by heating to 1000°C at a heating rate of 4°C/min and holding for 2 hours.

The heat-treated sample A-1 was thinned using a focused ion beam scanning electron microscope (FIB-SEM), and cross-sectional SEM images of the cut surfaces were acquired (see Figure 3). In this study, EDX analysis was performed on the acquired cross-sectional SEM images (Figure 3(b)) to obtain elemental mapping images of W and Pt (see Figure 4). Figure 4(a) shows the elemental map of W, and (b) shows the elemental map of Pt. From these analyses, it was found that the heat-treated sample A-1 comprises a W plate and a Pt-W alloy formed on the surface of the W plate.

Furthermore, in this test, EDX spectra were obtained for region α (W plate portion) and region β (Pt-W alloy portion) in Figure 3(b). The EDX spectrum of region α is shown in Figure 5(a), and the EDX spectrum of region β is shown in Figure 5(b). Based on these EDX spectra, the elemental abundance ratios in each region were analyzed. As a result, in region α (W plate portion), the results were confirmed to be Pt: 0 atm%, W: 99.05 atm%, and Fe: 0.95 atm%. On the other hand, in region β (Pt-W alloy portion), the results were confirmed to be Pt: 64.52 atm%, W: 34.30 atm%, and Fe: 1.18 atm%. Furthermore, in this test, EDX line analysis was performed on the 7000 nm long line segment X drawn in Figure 3(b) to investigate the changes in the elemental concentrations (atm%) of W and Pt. The results are shown in Figure 6. As shown in Figure 6, the amount of W element, which was approximately 100 atm% in region α (W plate portion), decreased to approximately 33 atm% in region β (Pt-W alloy portion). On the other hand, in region β, the amount of Pt element increased to 66 atm%. In this test, electron diffraction was performed in both region α (W plate portion) and region β (Pt-W alloy portion) in Figure 3(b). The results are shown in Figure 7. In Figure 7, (a) is an image showing the results of electron diffraction in region α (W plate portion), and (b) is an image showing the results of electron diffraction in region β (Pt-W alloy portion). In this electron diffraction, a diffraction pattern for W was obtained in region α, and in region β, a diffraction pattern at least on the 011 plane of Pt ₂ W was obtained. From these analysis results, it was found that the Pt-W alloy produced in this process is an intermetallic compound (Pt ₂ W) in which Pt and W are mixed in an integer ratio of 2:1.

Next, the crystal structure of the sample A-1 was analyzed using EBSD on the SEM image. The SEM/EBSD image of the analysis results is shown in Figure 8. Also, (c) in Figure 8 shows the tungsten and _Pt2W in the SEM/EBSD image of Figure 8(b) colored. Furthermore, based on the results of this EBSD analysis, the particle size of the crystal grains in each region of the W plate and the Pt-W alloy was measured. Specifically, the equivalent circle diameter of the crystal grains in the image was measured in each region of the W plate and the Pt-W alloy, and a number-based particle size distribution was created. The results are shown in Figure 9. Note that (a) in Figure 9 is the particle size distribution of the crystal grains in the W plate, and (b) is the particle size distribution of the crystal grains in the Pt-W alloy. From these analysis results, it was found that the Pt-W alloy ( _Pt2W ) formed on the W plate is composed of extremely fine crystal grains of several hundred nanometers.

2. W-Pt-Cu Alloy Formation Process In this process, Cu paste was prepared by mixing Cu powder with an average particle size of 1 μm, a binder (acrylic resin), and a solvent (IBA: isobutyl alcohol). The Cu powder content of this Cu paste was set to 80 wt% (30 vol%) by volume relative to the total weight. The Cu paste was then applied to the Pt-W alloy side surface of the analysis sample A-1 using a metal mask (thickness 50 μm × 20 mm × 20 mm). Next, a drying treatment (drying temperature: 120°C, drying time: 30 minutes) was performed to dry the Cu paste on the surface of analysis sample A-1, and then a heat treatment was performed to prepare analysis sample A-2. The atmosphere for the heat treatment was set to a reducing atmosphere ( _N2 - _H2 (3%) gas). Furthermore, in this process, the heat treatment was carried out under the conditions of heating to 400°C at a heating rate of 4°C/min and holding for 1 hour, followed by heating to 1000°C at a heating rate of 4°C/min and holding for 2 hours.

In this analysis process, first, the analysis sample A-2, after heat treatment, was thinned using a FIB-SEM. Cross-sectional SEM images of the cut surface were then captured. The results are shown in Figure 10. Next, the crystal structure of analysis sample A-2 was analyzed using EBSD. The results are shown in Figure 11. As shown in Figure 11(b), it was found that analysis sample A-2 contained a W-Pt-Cu alloy with a mixture of W phase and Pt-Cu phase. It was also found that both the W phase and Pt-Cu phase were composed of minute crystal grains. Furthermore, as shown in Figure 11(c), the Pt-Cu phase had a random crystal orientation and was composed of particularly minute crystal grains. On the other hand, as shown in Figure 11(d), the W phase was composed of larger crystal grains than the Pt-Cu phase, and the crystal orientation of these grains was found to be oriented in the [101] direction.

Furthermore, in this test, the particle size of the crystal grains in the W-Pt-Cu alloy was measured based on the EBSD analysis results described above. Here, the equivalent circular diameter of the crystal grains constituting each phase, the W phase and the Pt-Cu phase, was measured within the observation field, and the particle size distribution in each phase was determined. The results are shown in Figure 12. Figure 12(a) shows the particle size distribution of the Pt-Cu phase, and (b) shows the particle size distribution of the W phase. As shown in Figure 12, the _D50 particle size of the W phase is 621 nm, and the _D50 particle size of the Pt-Cu phase is 102 nm, indicating that both the W phase and the Pt-Cu phase are composed of very fine crystal grains. From the particle size distribution shown in Figure 12 and the SEM/EBSD image shown in Figure 11, it is inferred that the W-Pt-Cu alloy formed in the analysis sample A-2 has a morphology in which very minute crystal grains of the Pt-Cu phase are filled between relatively large crystal grains of the W phase. In other words, from this analysis, it is understood that the W-Pt-Cu alloy is formed by the migration (diffusion) of Pt in the Pt- _2W alloy to Cu while the Pt- _2W alloy and Cu are mixed together.

B. Second Test In this test, as in the second embodiment described above, a heat treatment was performed on the W source and the Cu source with a Pt source interposed between them. Various analyses were then performed on the resulting alloy material.

1. Sample Preparation First, a plate-shaped tungsten material (thickness 0.3 mm, length 7.5 mm, width 7.5 mm) was prepared as the W source. Then, a Pt paste was prepared as the Pt source, and the Pt paste was applied to the entire surface of one side of the tungsten material. The Pt paste used in this test was prepared by mixing 21 vol% Pt powder (average particle size: 0.5 μm), a binder (ethylcellulose resin), a dispersant, and a solvent. The solvent used for the Pt paste was 2,2,4-Trimethyl-1,3-pentanediol 1-Monoisobutyrate. In this test, the Pt paste was dried by drying at 120°C for 30 minutes, and then debindered in air (200°C for 3 hours).

Next, a plate-shaped copper member (0.3 mm thick, 20 mm long, 20 mm wide) was prepared as the Cu source. The paste-coated surface of the tungsten member and the copper member were brought into surface contact, and a 50 g alumina block was placed on top of the tungsten member, thereby applying a pressure of 0.89 kPa to the contact area between the tungsten member and the copper member. In this state, a firing process was carried out with a heating rate of 4 °C/min, a maximum firing temperature of 1000 °C, and a firing time of 2 hours to obtain a jointed body (Sample 1) in which the tungsten member and the copper member were joined. _N2 gas containing 3% hydrogen ( _H2 ) was used as the atmospheric gas during firing.

2. Sample Analysis (1) SEM Observation and EDX Analysis After cutting the assembled sample 1 along the stacking direction, the cut surface was polished using ion milling, and a cross-sectional SEM image of the cut surface was captured. EDX analysis was also performed on the captured cross-sectional SEM image to obtain elemental mapping images of tungsten (W), copper (Cu), and platinum (Pt). The analysis results at a magnification of 250x are shown in Figure 13, the analysis results at a magnification of 1000x are shown in Figure 14, the analysis results at a magnification of 10000x are shown in Figure 15, and the analysis results at a magnification of 50000x are shown in Figure 16. In Figures 13 to 16, (a) is the cross-sectional SEM image, (b) is the elemental map of W, (c) is the elemental map of Cu, and (d) is the elemental map of Pt.

First, as shown in Figure 13, observation at a low magnification of 250x revealed an alloy layer (Pt-Cu layer) mainly composed of a Pt-Cu alloy between the tungsten member and the copper member. Although such a Pt-Cu alloy usually has poor bonding properties to tungsten members, in the joint of Sample 1, the Pt-Cu layer and the tungsten member appeared to be strongly bonded. Therefore, as shown in Figure 14, observation of the boundary between the Pt-Cu layer and the tungsten member at a higher magnification (1000x) revealed that a layer containing a mixture of W, Pt, and Cu (W-Pt-Cu layer) was formed at the boundary between the tungsten member and the Pt-Cu alloy layer. Further magnification of this W-Pt-Cu layer revealed a W-Pt-Cu alloy in which the W phase was mixed within the Pt-Cu phase matrix, as shown in Figures 15 and 16. From the above analysis results, it was found that a W-Pt-Cu alloy can be produced even when a Pt source is interposed between the W source and the Cu source and the heat treatment is performed together. Furthermore, it was found that this W-Pt-Cu alloy allows for a strong bond between tungsten and copper components, which was previously difficult to join.

(2) Measurement of Atomic Numbers Next, in this test, five cross-sectional SEM images at a magnification of 50,000x, as shown in Figure 16(a), were acquired in the region where the above-mentioned W-Pt-Cu alloy was formed. The number of W, Pt, and Cu atoms in each field of view was then measured by EDX compositional analysis, and the average value was calculated. As a result, the average number of W atoms in the W-Pt-Cu alloy formed in Sample 1 was 34 atm%, and the average number of Pt-Cu atoms was 66 atm%. The ratio of Pt to Cu in the Pt-Cu alloy was 14.6:85.4.

(3) Elemental analysis by region In addition, in this test, EDX analysis was performed at each point from point 1 to point 6 in the SEM image of sample 1 at a magnification of 1000x (see Figure 17), and the ratio of the number of atoms of W, Pt, and Cu (atm%) was measured. The measurement results are shown in Table 1 below.

As shown in Figure 17 and Table 1, point 1 in Sample 1 is a tungsten component, point 2 is a W-Pt-Cu layer, points 3-5 are Pt-Cu layers, and point 6 is a copper component. Table 1 shows that the Pt/Cu ratio decreases from point 1 to point 6 (the Pt/Cu ratio is higher closer to point 1). From this, it can be inferred that in the initial stages of firing, a Pt-W alloy was formed in the region near the tungsten component (near point 2), and as a result of Pt diffusion from this Pt-W alloy toward the copper component (point 6), a W-Pt-Cu layer was formed at point 2 adjacent to the tungsten component. Furthermore, in the region further from the tungsten component (points 3-4), since no Pt-W alloy was formed, it can be inferred that a Pt-Cu alloy, a mixture of Pt and Cu, was formed. It should be noted that in metal joint components where the number of Cu atoms changes sequentially in this manner, the effect of easing thermal stress at the joint can be expected.

(4) Measurement of W-phase area In this test, the area of the W-phase was measured by analyzing the cross-sectional SEM image of Sample 1. For image analysis, the image analysis software (ImageJ 1.52a) from the National Institutes of Health (NIH) was used. Specifically, Figure 15(a) (SEM image at a magnification of 10,000x) was binarized and the colors were inverted so that the W-phase was displayed in black and the Pt-Cu phase in white. The area of the W-phase was then measured by counting the black dots present in a 5 μm × 7.5 μm field of view. As a result, 85 W-phase areas ranging from 0.007 ^μm² to 1.02 ^μm² were identified in the matrix of the Pt-Cu phase displayed in white. The area of each of the 85 identified W-layers is shown in Table 2 below. In other words, in the W-Pt-Cu alloy of Sample 1, it was found that W phases with an area ranging from 0.007 ^μm² to 1.02 ^μm² were present at a density of approximately 2.3 locations/ ^μm² . Furthermore, the average area of the W phase in the above field of view was 0.113 ^μm² . The maximum area of the W phase was 1.02 ^μm² , and the minimum was 0.007 ^μm² .

(5) Observation of the crystal structure Sample 1 was thinned using a FIB-SEM and SEM/EBSD images were acquired. The results are shown in Figure 18. As shown in Figure 18, in Sample 1, a Pt-Cu alloy is formed between the tungsten member and the copper member, and a W-Pt-Cu alloy is formed at the boundary between the Pt-Cu alloy and the tungsten member. Furthermore, it was confirmed that the crystal grains of W are smaller in the region of the tungsten member that is in contact with the W-Pt-Cu alloy than in other regions. This is presumed to be because W was supplied from that region for the formation of the W-Pt-Cu alloy. And in the region where the crystal structure of W is smaller, an improvement in strength can be expected.

(6) Elemental Mapping In this test, HAADF-STEM (High Angle Annular Dark-Field Scanning Transaction Electron Microscope) images (magnification 50,000x) were obtained from the specimens thinned using FIB-SEM. Elemental mapping images were then obtained from these HAADF-STEM images, along with EDX spectra. The results of the HAADF-STEM images and elemental mapping images are shown in Figure 19. Figure 20 shows the EDX spectrum of the entire W-Pt-Cu layer in the obtained HAADF-STEM image. Figure 21 shows the EDX spectrum of the W phase in W-Pt-Cu, and Figure 22 shows the EDX spectrum of the Pt-Cu phase.

First, as shown in Figure 20, the entire W-Pt-Cu layer mainly contained W, Cu, Pt, Mo, Fe, and O elements. Then, as shown in Figures 20 and 21, the W phase mainly contained W, Mo, Fe, and O elements. Of these, the Mo and Fe elements are thought to originate from impurities contained in the W plate. The Mo element may have been detected from the sample folder. On the other hand, as shown in Figures 19 and 22, the Pt-Cu phase mainly contained Cu, Pt, and O elements. The O element, detected in both the W and Pt-Cu phases, is thought to originate from oxygen deposited in the measurement environment or surface oxidation of the test piece. Finally, the image in Figure 19 clearly confirms that the W-Pt-Cu layer is a W-Pt-Cu alloy, a mixture of a W phase (mainly composed of W) and a Pt-Cu phase containing a Pt-Cu alloy.

Analysis of Figure 21 revealed that the W phase contained 84.57 atm% of W atoms, 2.56 atm% of Cu atoms, and 0.06 atm% of Pt atoms. The W phase also contained 12.81 atm% of molybdenum (Mo), an impurity, which is thought to be a detection of molybdenum present in the sample folder. On the other hand, analysis of Figure 22 revealed that the Pt-Cu phase contained 2.31 atm% of W atoms, 78.13 atm% of Cu atoms, and 15.59 atm% of Pt atoms. The Pt-Cu phase also contained 3.97 atm% of molybdenum (Mo), an impurity. This Mo is also thought to be a detection of molybdenum present in the sample folder.

C. Third Test In this test, ten types of composites (samples 2 to 11) were prepared under different conditions from the second test described above. The preparation conditions for each sample and the analysis performed on each sample are described below.

(1) Sample 2
In Sample 2, a composite body was prepared by joining a tungsten member and a copper member under the same conditions as Sample 1, except that the Pt powder content in the Pt paste was reduced to 10 vol%. SEM observation and EDX analysis were performed on Sample 2 under the same conditions as the second test. The analysis results at a magnification of 5000x for Sample 2 are shown in Figure 23, and the analysis results at a magnification of 50000x are shown in Figure 24. In Figures 23 and 24, (a) is a cross-sectional SEM image, (b) is an elemental map of W, (c) is an elemental map of Cu, and (d) is an elemental map of Pt. Furthermore, SEM images (magnification of 50000x) of the W-Pt-Cu alloy formed in Sample 2 were acquired for five fields, and EDX analysis was performed on each field to measure the ratio (at%) of the number of atoms of W, Pt, and Cu. The measurement results are shown in Table 3 below.

As shown in Figures 23 and 24, in Sample 2, similar to Sample 1, a ternary diphase W-Pt-Cu alloy was formed at the joint between the tungsten and copper members. Furthermore, calculated from the measurement results in each field of view shown in Table 2, the average ratio of W phase to Pt-Cu phase in the W-Pt-Cu layer of Sample 2 was 23.37:76.63. The ratio of Pt and Cu elements in the Pt-Cu phase was 7.07:92.93. From these results, it was found that the ratio of Pt to Cu in Sample 2 was smaller than in Sample 1. This is understood to be because a Pt paste with a lower Pt content was used compared to Sample 1.

Next, a line segment X1 with a length of 20 μm was drawn from the upper side (Pt-Cu alloy side) to the lower side (tungsten member side) of Figure 24(a), and line analysis was performed to examine the changes in the elemental concentrations of W, Pt, and Cu along this line segment X1. The results are shown in Figure 25. In Figure 25, the 0 μm position on the horizontal axis corresponds to the upper end of line segment X1, and the 20 μm position corresponds to the lower end of line segment X1. The vertical axis shows the characteristic X-ray intensity of each element. In Figure 25, graph (a) shows the analysis results for Pt, graph (b) shows the analysis results for W, and graph (c) shows the analysis results for Cu. As shown in Figure 25, in the region where the Pt-Cu alloy exists (upper side in Figure 23(a)), Pt and Cu are the main components, and W was hardly detected. Furthermore, in the region where the W-Pt-Cu alloy exists (the central part in Figure 23(a)), the elements W, Pt, and Cu were individually detected. The tungsten component (the lower part in Figure 23(a)) was composed almost entirely of W, with a small amount of Pt present.

(2) Sample 3
In Sample 3, the tungsten and copper members were joined under the same conditions as in Sample 2, except that the firing temperature for the tungsten and copper members was changed to 800°C. SEM observation and EDX analysis were performed on Sample 3 under the same conditions as in the second test. The analysis results at a magnification of 5000x for Sample 3 are shown in Figure 26, the analysis results at a magnification of 50000x are shown in Figure 27, and the analysis results at a magnification of 200000x are shown in Figure 28. In Figures 26 to 28, (a) is a cross-sectional SEM image, (b) is an elemental map of W, (c) is an elemental map of Cu, and (d) is an elemental map of Pt. From these analysis results, it was confirmed that in Sample 3, the region where the W-Pt-Cu alloy exists is thin, and the structure in which the W phase and Pt-Cu phase are mixed is finer.

Furthermore, in Sample 3, quantitative analysis of the elemental counts of W, Pt, Cu, and O was performed based on EDX analysis of cross-sectional SEM images at a magnification of 200,000x (Figure 28). This quantitative analysis revealed that the W atom count in the W-Pt-Cu layer was 20.73%, the Pt atom count was 5.37 atm%, the Cu atom count was 69.11 atm%, and the O atom count was 4.79 atm%. The elemental analysis results showed no significant difference in the abundance ratios of W, Pt, and Cu elements between Sample 2 and Sample 3 in the W-Pt-Cu alloy.

(3) Sample 4
In Sample 4, the tungsten and copper members were bonded under the same conditions as in Sample 2, except that the debinder treatment conditions after applying the Pt paste were changed to 160°C for 30 minutes. SEM observation and EDX analysis were performed on Sample 4 under the same conditions as in the second test. The analysis results at a magnification of 5000x for Sample 4 are shown in Figure 29, the analysis results at a magnification of 50000x for the Pt-Cu layer are shown in Figure 30, the analysis results at a magnification of 50000x for the Pt-W layer are shown in Figure 31, the analysis results at a magnification of 50000x for the W-Pt-Cu layer are shown in Figure 32, and the analysis results at a magnification of 50000x for the tungsten member are shown in Figure 33. In Figures 29 to 33, (a) is a cross-sectional SEM image, (b) is an elemental map of W, (c) is an elemental map of Cu, and (d) is an elemental map of Pt. Furthermore, in Sample 4, quantitative analysis of the number of W, Pt, and Cu elements was performed based on EDX analysis of the cross-sectional SEM images in Figures 29 to 33. The analysis results are shown in Table 4. In addition, for Sample 4, a line segment X2 with a length of 20 μm was drawn from the upper side (Pt-Cu alloy side) to the lower side (tungsten member side) of Figure 29(a), and the change in the concentration distribution of W, Pt, and Cu along this line was investigated. The results are shown in Figure 34. In Figure 34, the 0 μm position on the horizontal axis corresponds to the upper end of line segment X2, and the 20 μm position corresponds to the lower end of line segment X2. The vertical axis shows the characteristic X-ray intensity of each element. In Figure 34, (a) shows the analysis results for Pt, (b) shows the analysis results for W, and (c) shows the analysis results for Cu. As shown in Figure 34, in the region where the Pt-Cu alloy is present, the presence of Pt and Cu elements was confirmed, but the presence of W element was not confirmed. Furthermore, in the region where the W-Pt-Cu alloy was present, the elements W, Pt, and Cu were each detected. In the tungsten region, most of the material consisted of W, but a small amount of Pt was also present.

In Sample 4, the W-Pt-Cu layer was thicker than in the other examples, and a layer mainly composed of Pt-W was present on top of it. It is presumed that the formation of such a thick W-Pt-Cu layer was due to a reduction in the debindering temperature, resulting in less tungsten oxide formation. This allowed for the formation of a thick Pt-W alloy, a precursor to W-Pt-Cu, without inhibition. Furthermore, as shown in Figure 29, it was found that in Sample 4, a Pt-W layer containing Pt and W was formed at the boundary between the W-Pt-Cu layer and the Pt-Cu layer. This Pt-W layer was partially interrupted, and a W-Pt-Cu layer was present in the interrupted portion. Therefore, it is inferred that in this sample, during the formation of the W-Pt-Cu alloy, the Pt-W alloy and Cu mixed through the interrupted portion of the Pt-W layer.

Furthermore, in sample 4, sample 1 was thinned using FIB-SEM, and backscattered electron images were obtained in a different field of view than that shown in Figure 29(a) above, and various analyses were performed. First, Figure 35(a) is a backscattered electron image of sample 4 (5000x magnification), (b) is a magnified view of region α in (a) (20000x magnification), and (c) is a magnified view of region β in (a) (20000x magnification). As shown in Figure 35, in sample 4, a W-Pt-Cu layer was formed on a W plate, a Pt-W layer was formed on top of that, and a Pt-Cu layer was formed on top of that. Then, in sample 4, elemental mapping images based on EDX analysis were obtained in each of regions α and β in Figure 35(a). The results of the elemental mapping image in region α are shown in Figure 36, and the results of the elemental mapping image in region β are shown in Figure 37. First, as shown in Figure 36, it was confirmed that in the Pt-W layer within region α, trace amounts of Pt-Cu crystal particles were present between Pt-W crystal particles with a particle diameter of approximately 100-500 nm. The area ratio of Pt-W crystal particles to Pt-Cu crystal particles in this Pt-W layer was 98.5:1.5. Furthermore, the W phase present at the interface between the W-Pt-Cu layer and the Pt-W layer was formed almost entirely of tungsten. Also, as shown in Figure 37, the area ratio of the Pt-Cu phase to the W phase in the W-Pt-Cu layer was 52.9:47.1.

Next, in Sample 4, HAADF-STEM images and elemental mapping images of the HAADF-STEM images were also acquired. Figure 38 shows the results of the HAADF-STEM image and elemental mapping image of Sample 4. Figure 39 is a graph showing the concentration distribution of Pt, Cu, and W along line segment X3 in Figure 38. As shown in Figures 38 and 39, Sample 4 consisted of a W plate mainly composed of W, a W-Pt-Cu layer having a W phase and a Pt-Cu phase, a Pt-W layer formed of a Pt-W alloy, and a Pt-Cu layer formed of a Pt-Cu alloy. The relative abundance of the metal elements in each layer was as shown in Table 5.

Furthermore, Figure 40 shows the results of the HAADF-STEM image and elemental mapping image at the interface between the W plate of sample 4, the W phase of the W-Pt-Cu layer, and the Pt-Cu phase of the W-Pt-Cu layer. Figure 41 is a graph showing the concentration distribution of Pt, Cu, and W along line segment X4 in Figure 40, and Figure 42 is a graph showing the concentration distribution of O and Fe along line segment X4. First, as shown in Figures 40 and 41, there were almost no Pt or Cu elements in the W plate, and almost no W elements in the Pt-Cu phase of the W-Pt-Cu layer. From this, it can be concluded that there was almost no diffusion of metal elements at the interface between the Pt-Cu phase of the W-Pt-Cu layer and the W plate. Also, as shown in Figures 40 and 42, the presence of a small amount of iron (Fe) was confirmed in the W plate. The presence of oxygen (O) is presumed to be due to measurement noise. Furthermore, these Fe and O elements were present in all regions, and no clear segregation was observed at the interface between the Pt-Cu phase of the W-Pt-Cu layer and the W plate.

Furthermore, in Sample 4, electron diffraction was performed in each region from region α to region δ in Figure 38. The results are shown in Figure 43. Figure 43(a) is an image showing the results of electron diffraction in region α (W plate). From these electron diffraction results, it was identified that the element present in region α (W plate) is W. Next, Figure 43(b) is an image showing the results of electron diffraction in region β (W-Pt-Cu layer). From these electron diffraction results, the W phase and Pt-Cu phase were confirmed in region β (W-Pt-Cu layer). Furthermore, it was found that at least _Cu3Pt is present in the Pt-Cu phase in the W-Pt-Cu layer. Finally, Figure 43(c) is an image showing the results of electron diffraction in region γ (Pt-W layer). In this Pt-W layer, in addition to the Pt-W alloy, a Pt-Cu alloy was also confirmed. Furthermore, the Pt-W layer contained at least _Pt2W as a Pt-W alloy and at least _Cu3Pt as a Pt-Cu alloy. Figure 43(d) is an image showing the results of electron diffraction in region δ (Pt-Cu layer). This Pt-Cu layer contained at least _Cu3Pt as a Pt-Cu alloy.

Next, as shown in Figure 40 above, in Sample 4, HAADF-STEM images and elemental mapping images were obtained at the interface between the W plate and the W-Pt-Cu layer. In addition, in Sample 4, HAADF-STEM images and elemental mapping images were obtained for each layer: the W plate, the Pt-W layer, and the Pt-Cu layer. The results are shown in Figures 44 to 46. As shown in Figures 40 and 44 to 46, in Sample 4, a Pt-Cu phase containing Pt and Cu was confirmed in each region of the W plate, the W-Pt-Cu layer, the Pt-W layer, and the Pt-Cu layer. The EDX spectra of the Pt-Cu phase in each of these regions are shown in Figures 47 to 50, and the elemental ratios calculated based on these EDX spectra are shown in Table 6. As shown in Figures 47 to 50 and Table 6, there were no significant differences in the elemental ratios of the Pt-Cu phase present in each layer.

Based on the above analysis, a W-Pt-Cu alloy was formed between the Pt-W layer and the W plate in sample 4. This suggests that a Pt-W alloy was initially formed by applying Pt paste to the W plate and heat treatment. Subsequently, a Cu-containing component entered the Pt-W alloy, and the Pt in the Pt-W alloy migrated (diffused) to the Cu, resulting in the formation of a W-Pt-Cu alloy. Furthermore, as shown in Figure 44, Cu was also present in the W plate in sample 4. This also suggests a formation process in which Cu entered the Pt-W alloy.

(4) Sample 5
In Sample 5, the tungsten and copper members were joined under the same conditions as in Sample 2, except that the debinder treatment conditions after applying the Pt paste were changed to 450°C for 30 minutes. SEM observation and EDX analysis were performed on Sample 5 under the same conditions as in the second test. The analysis results at a magnification of 5000x for Sample 5 are shown in Figure 51, and the analysis results at a magnification of 50000x for the W-Pt-Cu alloy are shown in Figure 52. In Figures 51 and 52, (a) is a cross-sectional SEM image, (b) is an elemental map of W, (c) is an elemental map of Cu, and (d) is an elemental map of Pt. As a result of this analysis, it was confirmed that in Sample 5, the W-Pt-Cu layer was thinner than in Samples 1, 2, and 4, and the distribution of the W-Pt-Cu alloy on the W plate was mottled. This is presumed to be because the high temperature of the binder removal process caused tungsten oxide to form on the surface of the W plate, and this tungsten oxide inhibited the reaction between the W material and Pt, thereby inhibiting the formation of the Pt-W alloy. Furthermore, in sample 5, quantitative analysis of the number of W, Pt, and Cu elements in the W-Pt-Cu alloy was performed based on the EDX analysis in Figure 52. As a result of this quantitative analysis, the number of W atoms in the W-Pt-Cu layer was 31.06%, the number of Pt atoms was 2.03 atm%, and the number of Cu atoms was 66.91 atm%. As a result of this elemental analysis, it was found that the abundance of Pt elements in the W-Pt-Cu alloy of sample 5 was lower than that of samples 2 to 4.

(5) Sample 6
In Sample 6, Cu paste was used as the Cu source instead of a plate-shaped copper member. Specifically, Pt paste with the same composition as Sample 2 was applied to the surface of a tungsten member of the same dimensions as Sample 1. Then, drying and binder removal treatments were performed under the same conditions as Sample 4. After that, Cu paste was applied to the Pt paste surface, followed by drying (120°C, 30 minutes) and heat treatment. The heat treatment was set to the same conditions as Sample 1. The Cu paste used in this sample was a mixture of Cu powder with an average particle size of 0.5 μm, glass powder, ethyl cellulose resin, a dispersant, and a solvent. SEM observation and EDX analysis were performed on Sample 6 under the same conditions as the second test. The analysis results of Sample 6 at a magnification of 5000x are shown in Figure 53, and the analysis results of the W-Pt-Cu alloy at a magnification of 50000x are shown in Figure 54. In Figures 53 and 54, (a) is a cross-sectional SEM image, (b) is an elemental map of W, (c) is an elemental map of Cu, and (d) is an elemental map of Pt. As a result of this analysis, the formation of a W-Pt-Cu alloy was confirmed in sample 6, just as in the other samples. From this, it was found that Cu paste can be used as the Cu source even in the embodiment in which the W source, Pt source, and Cu source are heat-treated simultaneously. Furthermore, in sample 6, quantitative analysis of the number of W, Pt, and Cu elements in the W-Pt-Cu alloy was performed based on the EDX analysis in Figure 54. As a result of this quantitative analysis, the number of W atoms in the W-Pt-Cu layer of sample 6 was 40.16%, the number of Pt atoms was 2.27 atm%, and the number of Cu atoms was 57.57 atm%.

(6) Sample 7
In Sample 7, we investigated whether a W-Pt-Cu alloy could be formed when an intermediate metal component (Pt film) was interposed between the W-Pt alloy and the Cu source. Specifically, a thick layer of Pt paste with the same composition as Sample 2 was applied to the surface of a tungsten component of the same dimensions as Sample 1. After drying at 120°C for 30 minutes, a binder removal treatment was performed by heating in air (heating rate: 10°C/min, maximum temperature: 160°C, heating time: 0.5 hours). Subsequently, a firing treatment was carried out in an _N2 - _H2 (3%) atmosphere (heating rate: 4°C/min, maximum temperature: 1000°C, firing time: 2 hours). The sample was then cooled to room temperature, and it was confirmed that a Pt firing film had been formed on the surface of the W plate. Next, the same Cu paste as in Sample 6 was applied to the surface of this Pt firing film and dried at 120°C for 30 minutes. Then, the samples were subjected to a firing process in an _N2 - _H2 (3%) atmosphere (heating rate: 4°C/min, maximum temperature: 1000°C, firing time: 2 hours). After the samples were cooled to room temperature, the cross-sections were polished by ion milling, and then observed by SEM and analyzed by EDX.

The analysis results for sample 7 at a magnification of 5000x are shown in Figure 55. Furthermore, the analysis results for each portion of sample 7—the Pt-W layer, W-Pt-Cu layer, W plate, and the interface between the W plate and the W-Pt-Cu layer—at a magnification of 50000x are shown in Figures 56 to 59. In Figures 55 to 59, (a) is a cross-sectional SEM image, (b) is the elemental map of W, (c) is the elemental map of Cu, and (d) is the elemental map of Pt. As shown in Figures 55 to 59, it was confirmed that a W-Pt-Cu alloy was formed in sample 7, similar to samples 2 to 6. From this, it was found that direct contact between the W-Pt alloy and the Cu source is not necessary to form a W-Pt-Cu alloy; an intermediate metal component (Pt film) can be interposed between the W-Pt alloy and the Cu source.

Furthermore, in Sample 7, quantitative analysis of the number of W, Pt, and Cu elements in the W-Pt-Cu alloy was performed based on the EDX analysis of Figures 55 to 59. Table 7 shows the results of the analysis at a magnification of 5000x (Figure 55) and the quantitative analysis of the number of elements in each of the following areas: the Pt-W layer (Figure 56), the W-Pt-Cu layer (Figure 57), the W plate (Figure 58), and the interface between the W plate and the W-Pt-Cu layer (Figure 59).

(7) Sample 8
In Sample 8, the shapes of the Pt-W alloy produced in the Pt-W alloy production process and the W-Pt-Cu alloy produced in the W-Pt-Cu alloy production process were compared. Specifically, a thin layer of Pt paste with the same composition as Sample 2 was applied to the surface of a W plate of the same dimensions as Sample 1. After drying at 120°C for 30 minutes, a binder removal treatment was performed by heat treatment in air (heating rate: 10°C/min, maximum temperature: 160°C, heating time: 0.5 h). Subsequently, a firing treatment was carried out in an _N2 - _H2 (3%) atmosphere (heating rate: 4°C/min, maximum temperature: 1000°C, firing time: 2 hours). The sample was then cooled to room temperature, and it was confirmed that a W-Pt alloy had been formed on the surface of the W plate. The surface of the W-Pt alloy produced in this sample was rough with fine irregularities. Next, in this sample, a coated area was created on the surface of the W-Pt alloy with Cu paste (Cu source) applied, and an uncoated area was created without Cu paste. The same Cu paste as in Sample 6 was used. The Cu paste in the coated area was dried at 120°C for 30 minutes, and then fired in an _N2 - _H2 (3%) atmosphere (heating temperature: 4°C/min, maximum temperature: 1000°C, firing time: 2 hours). After the sample was cooled to room temperature, the cross-section was polished by ion milling, and SEM observation and EDX analysis were performed.

The analysis results for the uncoated region of Sample 8 are shown in Figures 60 and 61. On the other hand, the analysis results for the coated region are shown in Figures 62 to 65. First, as shown in Figure 60, a W-Pt alloy with fine surface irregularities was formed on the surface of the W plate in the uncoated region. Meanwhile, as shown in Figures 62 to 65, a W-Pt-Cu alloy was formed between the W plate and the Pt-Cu layer in the coated region. Furthermore, the W-Pt-Cu alloy in Sample 8, like the W-Pt alloy in the uncoated region, had fine surface irregularities formed on its surface (the interface on the Pt-Cu layer side). From this, it was found that the shape of the Pt-W alloy produced in the Pt-W alloy production process is reflected in the shape of the W-Pt-Cu alloy after the W-Pt-Cu alloy production process.

(8) Sample 9
In Sample 9, Cu paste was applied to the surface of a plate-shaped tungsten member and then dried and fired. Specifically, Cu paste with the same composition as Sample 6 was applied to the surface of a tungsten member of the same dimensions as Sample 1. After drying the Cu paste by drying at 120°C for 30 minutes, it was heated in air at 400°C for 1 hour. Subsequently, a firing process was performed with a firing rate of 5°C/min, a maximum firing temperature of 1000°C, and a firing time of 30 minutes. SEM observation and EDX analysis were performed on Sample 9 under the same conditions as the second test. The analysis results for Sample 9 at a magnification of 250x are shown in Figure 66, the analysis results at a magnification of 1000x are shown in Figure 67, the analysis results at a magnification of 5000x are shown in Figure 68, and the analysis results at a magnification of 50000x are shown in Figure 69. In Figures 66 to 69, (a) is a cross-sectional SEM image, (b) is an elemental map of O (oxygen), (c) is an elemental map of Cu, and (d) is an elemental map of W. These analyses also showed that no alloy material containing both W and Cu was formed. In other words, it was found that even when Cu and W are brought into contact and heat-treated in the absence of Pt (a state in which no W-Pt alloy is formed), an alloy material containing both W and Cu is not produced.

(9) Sample 10
In Sample 10, Pt paste was applied to the surface of a plate-shaped tungsten member and then dried and fired. Specifically, Pt paste with the same composition as Sample 1 was applied to the surface of a tungsten member of the same dimensions as Sample 1. The Pt paste was then dried by a drying treatment at 120°C for 30 minutes, followed by a heat treatment in air at 160°C for 0.5 hours. After that, a firing treatment was performed with a firing rate of 3°C/min, a maximum firing temperature of 1300°C, and a firing time of 10 minutes. SEM observation and EDX analysis were performed on Sample 10 under the same conditions as the second test. The analysis results of Sample 10 at a magnification of 5000x are shown in Figure 70. In Figure 70, (a) is a cross-sectional SEM image, (c) is the elemental map of W, and (d) is the elemental map of Pt. These analyses confirmed that heating a Pt source and a W source in contact, as in this sample, generates an alloy containing Pt and W (Pt-W alloy). However, this sample did not generate a two-phase alloy like samples 1-8.

(10) Sample 11
In Sample 11, a Pt-Cu paste was applied to the surface of a plate-shaped tungsten member and then dried and fired. Specifically, a Pt-Cu paste, in which Pt particles and Cu particles were uniformly dispersed, was applied to the surface of a tungsten member of the same dimensions as Sample 1. After drying the paste by drying it at 120°C for 30 minutes, a first heat treatment was performed in air at 160°C for 0.5 hours, followed by a second heat treatment in _N2 gas containing 3% _H2 gas, with a heating rate of 10°C/min, a maximum heating temperature of 400°C, and a heating time of 1 hour. Then, a heat treatment was performed with a heating rate of 5°C/min, a maximum firing temperature of 1000°C, and a firing time of 30 minutes. SEM observation was performed on Sample 11 under the same conditions as the second test. The analysis results of Sample 11 at a magnification of 5000x are shown in Figure 71, and the analysis results at a magnification of 50000x are shown in Figure 72. These analyses revealed that when a Pt source and a Cu source were mixed, as in this sample, a W-Pt-Cu alloy was not formed despite the presence of a W source, a Pt source, and a Cu source. Only unreacted W material and a Pt-Cu alloy formed on the surface of the W material were observed. Furthermore, the W material and the Pt-Cu alloy were not properly bonded. The reason for this result is presumed to be as follows: In this sample, the reaction between the mixed Pt source and Cu source occurred preferentially, and a Pt-W alloy was not formed. The Pt-Cu alloy formed by the reaction of the Pt source and Cu source had low reactivity with the W material, so a W-Pt-Cu alloy like that in samples 1-6 was not formed. From this, it was found that in order to produce a W-Pt-Cu alloy, it is necessary to produce a Pt-W alloy as a precursor and then transfer Pt from the Pt-W alloy to Cu.

D. Fourth Test In this test, a W-Pt-Cu alloy having a Pt-Cu phase containing a metal element other than Cu and Pt (a third metal element) was manufactured. The specific manufacturing procedure is described below.

First, a Pt paste was applied to a W plate measuring 0.3 mm thick x 7.5 mm x 7.5 mm. The Pt paste was prepared by kneading Pt powder with an average particle size of 0.5 μm, a binder (ethyl cellulose resin), a dispersant, and a solvent (2,2,4-Trimethyl-1,3-pentanediol 1-Monoisobutyrate). The W plate coated with the Pt paste was then subjected to a drying treatment (120°C, 30 minutes), followed by a binder removal treatment (in air, 160°C, 0.5 hours). Finally, the plate was heat-treated in a reducing atmosphere ( _N2 - _H2 (3%) atmosphere) to form a Pt-W alloy ( _Pt2W ) on its surface. During the heat treatment, the heating rate was set to 4°C/min, and the temperature was held for 2 hours after reaching the maximum temperature (1000°C).

Next, Au paste was applied to the Pt-W alloy surface of the W plate, followed by a drying treatment (120°C, 30 minutes). The Au paste was prepared by kneading Au powder with an average particle size of 0.5 μm, a binder (ethylcellulose), a dispersant, and a solvent (terpineol). Then, Cu paste was applied on top of the dried Au paste, followed by a drying treatment (120°C, 30 minutes). The same Cu paste used was the same as the paste used to prepare sample A-2 for analysis in the first test. Sample 12 was then prepared by heat treatment in a reducing atmosphere ( _N2 - _H2 (3%) atmosphere). During the heat treatment, the heating rate was set to 4°C/min, and the temperature was held for 2 hours after reaching the maximum temperature (1000°C).

The cross-section of the prepared sample 12 was CP polished and SEM-EDX analysis was performed. The results are shown in Figures 73 and 74. The magnification in Figure 73 is 5000x, and the magnification in Figure 74 is 50000x. In Figures 73 and 74, (a) is the cross-sectional SEM image, (b) is the elemental map of W, (c) is the elemental map of Cu, (d) is the elemental map of Pt, and (e) is the elemental map of Au. The atomic concentration of Cu measured by SEM-EDX analysis was 65.64%, the atomic concentration of W was 24.50%, the atomic concentration of Pt was 1.23%, and the atomic concentration of Au was 8.62%.

Analysis revealed that a W-Pt-Cu alloy, a mixture of W phase and Pt-Cu phase, was formed in sample 12. However, it was found that the Pt-Cu phase of the W-Pt-Cu alloy produced in this sample contained Au in addition to Pt and Cu (see Figures 73(e) and 74(e)). This result indicates that, as in this experiment, when a third element is added to the Cu source, that third element diffuses into the Pt-Cu phase along with Cu and Pt.

The above describes specific examples of the present invention in detail, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above.

10 Alloy material 12 W phase 14 Pt-Cu phase 20 First member 30 Second member 100 Joint

Claims (2)

A W-Pt-Cu alloy for bonding, consisting of three elements: tungsten (W), platinum (Pt), and copper (Cu), and unavoidable impurities.
The W phase, which mainly consists of tungsten (W), and the Pt-Cu phase, which has platinum (Pt) and copper (Cu), are mixed together.
Based on SEM-EDX, the number of tungsten atoms in the W phase is 75 atm% or more.
Based on the aforementioned SEM-EDX, the number of platinum atoms in the Pt-Cu phase is 0.1 atm% or more and 25 atm% or less.
SEM observation revealed a W-phase region with an area of 0.001 ^μm² to 1 ^μm² , where W-phase particles exist at a density of 0.2 locations/ ^μm² or more.
The W-phase region exists in a width and depth direction of 10 μm or more in a plan view.
A W-Pt-Cu alloy for joining, characterized by the following features. The W phase contains, as the unavoidable impurity, at least one selected from the group consisting of Mo, Fe, Co, Ni, Au, and Th.
The W-Pt-Cu alloy for joining according to claim 1, wherein the Pt-Cu phase contains at least one selected from the group consisting of Mo, Fe, Pd, Ir, Au, Co, Ni, Zn, Al, Sn, Pb, Mn, Ag, and Th as the unavoidable impurity.