JP2016193449A - Powder brazing material, joined body and vacuum vessel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder brazing material which does not need an atmosphere such as high vacuum, low oxygen concentration, low dew point, a low generated gas and the like and which is excellent in oxidation resistance.SOLUTION: A powder brazing material 100 containing one or more kinds of active metals selected from among titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V) and chromium (Cr), silver (Ag) and copper (Cu) and having a layer structure of two or more layers including an active metal core 11 localized with the active metal and an outer shell layer 13, a joined body where a metal member and a member are joined by the powder brazing material and a vacuum vessel are provided.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a powder brazing material containing an active metal, and a joined body and a vacuum vessel using the same.

  The active metal method is a paste state in which an active metal brazing material obtained by adding an active metal such as titanium (Ti), zirconium (Zr), vanadium (V) to a metal brazing material such as an Ag-Cu alloy is mixed with an organic binder, Alternatively, it is used as a foil-like brazing material, and the active metal brazing material is placed in the state of an alloy, foil, laminate, etc. between the metal member and the ceramic member, and heated in an inert atmosphere such as vacuum or argon gas. In this method, the active metal is segregated on the surface of the ceramic substrate, and a reaction layer such as an active metal oxide or nitride is formed and bonded.

  In addition, a Mo-Mn metallization method is known as a method for metallizing the joining surface of oxide ceramics, particularly alumina containing a large amount of silica. Although such a method enables high-strength metallization, it requires many processing steps and the process is relatively complicated.

  Since the melting point of the active metal brazing material is generally as low as about 730 ° C. to 850 ° C., it can be joined at a lower temperature than the metallization method. In addition, since bonding can be performed by a single heating / cooling process, the process can be simplified overwhelmingly compared to a metallization method that requires many processing steps.

  Active metal powder brazing materials containing 1 to 50% by weight of an active metal in silver (Ag) and copper (Cu) and in which these components are present in a uniform state are generally widely known. As described above, the active metal method using this brazing material is one in which the active metal forms a wet reaction by forming a reaction layer with the ceramics to be joined. Therefore, the active metal plays a central role as a brazing material. However, the active metal reacts very sensitively to the atmosphere, forming oxides, nitrides, etc., and has the disadvantage of easily losing its function as a brazing material. Oxidation proceeds only by storing in the air, and undissolved parts and segregated parts of components are generated during use, resulting in poor bonding.

  A technique for solving such a problem of oxidation of metal powder is known (for example, Patent Document 1). Patent Document 1 discloses a method in which metal powder (soft solder powder) is coated with a polymer capsule wall to protect it from oxidation. Such methods include: a) preparing a suspension from the powder and a hydrophobic liquid, b) adding a cationic surfactant to form a hydrophobic surface layer on the surface of each metal particle, and c) step a) And stirring the mixture from step b) until a viscous homogeneous material is formed, d) incorporating free radical polymerizable monomers into the material of step c), and e) starting the organic system to initiate the interfacial polymerization reaction. Adding the material, f) introducing the material of step e) into the aqueous material under constant stirring and controlling the polymerization reaction by adjusting the temperature to 50-90 ° C. and holding this temperature for at least 120 minutes, and The encapsulated soft wax powder is subjected to a process of cooling, washing and separating. However, this method requires a complicated process as described above, and uses a substance other than metal powder, such as an organic polymer or monomer, so depending on the type of the metal core, the oxidation or alteration of the metal core, There are drawbacks such as adverse effects on the bondability. Therefore, the technique of Patent Document 1 has not been put to practical use in joining using an active metal powder brazing material.

Special Table 2002-518182

  The present invention has been made in view of such problems of the prior art, and the object of the present invention is a strict atmosphere that has been conventionally required, for example, high vacuum, low oxygen concentration, low dew point, It is to provide a powder brazing material that does not require an atmosphere such as a low gas generation.

  As a result of intensive studies, the present inventors will pay attention to the oxide free energy of the elements constituting the active metal powder brazing material, and will have a structural feature in which an element having a low oxide free energy is arranged in the core portion of the powder. By using a material, the above-mentioned problems were solved and the present invention was completed.

That is, according to one embodiment, the present invention is a powder brazing material, which is one or more selected from titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), and chromium (Cr). Two or more kinds of active metals, silver (Ag), and copper (Cu) are included, and the powder brazing material includes two layers including an active metal core in which the active metal is localized and an outer shell layer. The above layer structure is provided.
In the powder brazing material, the silver (Ag) is preferably present as a main component in the outer shell layer.

In the powder brazing material, the active metal core is one in which the active metal existing as a pure metal is localized, and the active metal is contained in an amount of 1 to 5% by mass with respect to the total mass of the powder brazing material. It is preferable that
Alternatively, the active metal core is a localized hydride of the active metal or an alloy of the active metal and palladium (Pd), and the active metal is based on the total mass of the powder brazing material, It is preferable that 1-5 mass% is contained.

  Preferably, the powder brazing material further includes an intermediate layer between the active metal core and the outer shell layer, and the copper (Cu) is present as a main component in the intermediate layer.

  In the powder brazing material, the active metal core is a solid solution of the active metal and copper (Cu) or a compound of the active metal and copper (Cu) localized, and the active metal is It is preferable that 1-5 mass% is contained with respect to the total mass of the said powder brazing material.

  In the powder brazing material, it is preferable that the active metal core is spherical, foil-shaped or piece-shaped, and the maximum diameter of the active metal core is 0.1 μm to 150 μm.

  According to another embodiment of the present invention, there is provided a joined body obtained by joining a metal member and a ceramic member with the powder brazing material according to any one of the above.

  According to another embodiment of the present invention, there is provided a vacuum container formed by joining with any of the powder brazing materials described above.

  According to the present invention, resistance to active metal oxidation, which has been regarded as a problem in the past, exhibits extremely excellent resistance, ensures wettability even in an air atmosphere, and provides a strong connection between the ceramic member and the metal member. It is possible to provide a powder brazing material capable of realizing bonding, a bonded body bonded thereby, and a vacuum vessel.

FIG. 1 is a schematic view showing a cross section of a powder brazing material according to an embodiment of the present invention. FIG. 2 is a schematic view showing a cross-section of a powder brazing material according to another embodiment of the present invention. FIG. 3 is a conceptual diagram showing a vacuum vessel formed by joining with the powder brazing material of the present invention. FIG. 4 is a view showing a heating profile in the joining using the powder brazing material according to the first embodiment. FIG. 5 is a diagram schematically showing changes in the state of the metal in heat bonding using the powder brazing material of Example 1 and the comparative example.

  Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the embodiments described below.

[First embodiment: Powder brazing material]
According to the first embodiment, the present invention is a powder brazing material comprising a three-layer structure comprising one or more active metals, Ag, and Cu, and including an active metal core and an outer shell layer. It is. In the powder brazing material according to the first embodiment, the active metal is localized in the active metal core.

  FIG. 1 is a schematic cross-sectional view showing the powder brazing material according to the present embodiment. The powder brazing material 100 is formed of three layers of an active metal core 11, an intermediate layer 12, and an outer shell layer 13. In the illustrated embodiment, the active metal core 11 is mainly composed of active metal, a compound thereof, or an alloy, the intermediate layer 12 is mainly composed of Cu, and the outer shell layer 13 is mainly composed of Ag.

In the present invention, the active metal core 11 is a core part present in the innermost shell in the powder brazing material 100. The active metal core 11 is not exposed on the surface of the powder brazing material 100 and is completely covered with the intermediate layer 12 and the outer shell layer 13. Further, most of the active metal component contained in the powder brazing material 100, for example, 95% or more, preferably 98% or more is present in the active metal core 11. That is, the active metal is localized in the active metal core 11. In the present invention, the active metal is a metal element having a low oxide formation standard free energy ΔG ₀ , and is one or more selected from Ti, Zr, Hf, V, and Cr. In particular, it is preferable to contain at least Ti. These elements form a reaction layer on the ceramic surface with heating, and the reaction layer enables bonding with the ceramic.

  The active metal core 11 may be composed of pure metal of only active metal in some embodiments. Even in this case, Cu, Ag, and inevitable impurities constituting the brazing material may be mixed.

Alternatively, the active metal core 11 may be composed of an active metal and another metal or non-metallic element. In this case, the other metal or nonmetallic element is an element other than the active metal, Cu, and Ag, and does not oxidize the active metal. As an alloy of an active metal and another metal, for example, an alloy containing 0.01 to 1% by mass of palladium (Pd) is included in the active metal. From the viewpoint of oxidation resistance, Ti / Pd is preferable. Alloys can be used, but are not limited to these. The active metal core 11 may also be a compound of an active metal and a nonmetallic element and / or a metallic element. Examples of the compound of the active metal and the nonmetallic element include hydride, and TiH ₂ can be used, but is not limited thereto. It is preferable that no oxide of an active metal is contained.

  The outer shape of the active metal core 11 may be an arbitrary shape such as a foil shape or a piece shape in addition to a spherical shape. From the viewpoint of uniformity, it is preferably spherical. Moreover, the internal form may be a bulk form or a porous form. The active metal core 11 has a maximum diameter of preferably from 0.1 to 100 μm, more preferably from 1 to 50 μm, and even more preferably from 2 to 30 μm. A person skilled in the art can determine the optimum maximum diameter according to the purpose in consideration of the chemical conversion (surface area). The maximum diameter of the fine particles in the present invention is a value measured by a laser diffraction method.

  The content of the active metal is preferably 1 to 30% by mass and more preferably 1.25 to 5% by mass when the mass of the powder brazing material 100 is 100%. When a plurality of types of active metals are included, the mass ratio of the plurality of active metals is not particularly limited, and the total mass is preferably in the above range. The mass% of the active metal in this case is a value based on the active metal element alone even when the active metal forms an alloy or a compound.

  Next, the outer shell layer 13 forms a surface layer of the powder brazing material. In the present embodiment, the outer shell layer 13 is mainly composed of Ag (including Ag as a main component). It is preferable that the active metal is not substantially contained in the outer shell layer 13, but when the total mass of the active metal contained in the brazing material is 100%, for example, 5% by mass or less, preferably 2% by mass. The following active metals may be present in the outer shell layer 13. The outer shell layer 13 may contain inevitable impurities. At the bonding temperature of 800 to 900 ° C., which will be described later, Ag melts without being subjected to surface oxidation, and forms an eutectic system with Cu to be bonded to the metal, thereby protecting the active metal from oxidation. As preferred.

  The intermediate layer 12 directly covers the active metal core 11 and is covered by the outer shell layer 13. In the present embodiment, the intermediate layer 12 is mainly composed of Cu (including Cu as a main component), and inevitable impurities may be mixed.

  The outer shell layer 13 and the intermediate layer 12 are useful in that the active metal core 11 is shielded from the oxygen atmosphere and the active metal joining function is maintained while preventing the active metal from being oxidized. Each of the outer shell layer 13 and the intermediate layer 12 is a layer having a substantially uniform thickness as illustrated, and it is preferable that the intermediate layer 12 is not exposed to the outside. This is from the viewpoint of tissue uniformity and oxidation resistance. However, some variation in layer thickness and partial exposure of the intermediate layer 12 are allowed as long as the oxidation resistance function of the active metal by both the outer shell layer 13 and the intermediate layer 12 is maintained.

  In the present embodiment, among the components of the powder brazing material 100, the remainder of the content of the active metal, or the compound or alloy of the active metal is Cu and Ag. Therefore, for example, when the active metal is contained in a pure metal state in an amount of 1 to 5% by mass, Cu and Ag may be contained in an amount of 99 to 55% by mass. The mass ratio of Cu and Ag is not particularly limited, but may be any mass ratio known in the known active metal powder brazing filler metal containing Cu and Ag. For example, the mass ratio of Cu: Ag can be 1:25 to 1: 1 and is preferably 1:20 to 1: 2, but is not limited thereto. And the thickness of each layer of the outer shell layer 13 and the intermediate | middle layer 12 can be determined with the mass ratio of Cu and Ag, and the formation method of each layer mentioned later.

  The powder brazing material 100 having the above configuration preferably has an outer diameter of 3 to 200 μm, and more preferably 5 to 60 μm, in order to obtain a uniform joined body. However, the outer diameter can be appropriately determined depending on the purpose of joining and the object, and is not limited to the above range. The shape of the powder brazing material 100 depends on the shape of the active metal core 11 described above, and may be spherical, foil-shaped, or piece-shaped, but is preferably spherical.

  The powder brazing material 100 shown in FIG. 1 has a three-layer structure including the intermediate layer 12 and the outer shell layer 13 as separate layers, but as a modification, the intermediate layer is not included and an alloy of Cu and Ag. A powder brazing material 100 having a two-layer structure provided in contact with the active metal core may be used. Alternatively, it may be a four-layer structure in which an additional layer, for example, a layer mainly composed of an alloy of Cu and Ag is provided between the intermediate layer 12 and the outer shell layer 13.

  Next, the powder brazing material 100 according to the present embodiment will be described from the viewpoint of its manufacturing method. The method for manufacturing the powder brazing material 100 includes a first step of manufacturing the active metal core 11, a second step of covering the active metal core 11 with Cu, and forming the intermediate layer 12 on the active metal core 11, and an intermediate layer. 12 is covered with Ag, and the outer shell layer 13 is formed.

  In the first step, an active metal core 11 having a predetermined shape and a maximum diameter is manufactured from desired active metal particles or a plurality of types of active metal particles. An oxide film is usually formed on the surface of the active metal core 11, but the oxide film is preferably as thin and dense as possible. This is because when the dense and thick oxide film is uniformly formed on the outer periphery of the core, the electrical conductivity of the surface of the active metal core 11 is lowered, the adhesion of the intermediate layer 12 to the oxide film is poor, etc. This is because there is a concern that the covering of the intermediate layer 12 becomes insufficient, or an unformed portion of the intermediate layer 12 is generated. If such a phenomenon is a concern, it is preferable to carry out a treatment for making the surface of the active metal core 11 conductive or a treatment for cleaning it. Examples of these treatments include removal of an oxide film with an acidic solution and application of a catalyst, and are not limited to specific treatments.

  In the subsequent second step, a Cu intermediate layer 12 is provided on the surface of the active metal core 11, and the active metal core 11 is covered with Cu. Various methods can be used to coat the active metal core 11 with Cu. For example, Cu plating, sputtering, physical vapor deposition (PVD), chemical vapor deposition (CVD), or atomic volume device (ALD) is used. It can be by any method such as a method. It is most preferable to use electroless plating from the viewpoint of the uniformity, workability, and quantitativeness of the metal film. In particular, Cu plating on a metal that easily forms an oxide film such as titanium can also be performed by, for example, the method disclosed in Japanese Patent Application Laid-Open No. 07-90595. Furthermore, Cu plating on titanium can also be manufactured using contract manufacturing by a plating company. In this case, a Cu coating (intermediate layer) with a desired thickness is provided without oxidizing the metal with respect to titanium and / or other active metals and with the shape of the active metal core as a desired shape. This can be confirmed by performing energy dispersive X-ray analysis (EDS) on the powder cross section.

  In the subsequent third step, an Ag outer shell layer 13 is provided on the surface of the Cu intermediate layer 12 by an ordinary method, and Cu is coated with Ag. Various methods described in the second step can be used for covering Cu with Ag, and in particular, an electroless plating method is preferably used. In this case, electroless plating may be performed using a Pd catalyst. It can be similarly confirmed by the analysis method described in the second step that an Ag film having a desired thickness is provided.

  Even when the active metal core is not a pure metal but a compound or alloy, a powder brazing material can be produced by performing the first to third steps in the same manner as described above.

  Next, a method for using the powder brazing material according to the first embodiment will be described. The powder brazing material is preferably used for joining metal and ceramics. The materials to be joined are mainly metal members and ceramic members. Examples of the metal include, but are not limited to, stainless steel, Cu, and Invar alloy (low expansion alloy). The ceramic is not particularly limited as long as it forms a reaction layer with the active metal in the brazing material. For example, aluminum oxide having a purity of 90 to 100% (when the purity is not 100%, the remaining components are sintering aids, etc. ), Aluminum nitride, silicon carbide, silicon nitride, and the like, but are not limited thereto.

  A joining method of a metal member using a powder brazing material and a ceramic member includes a first step of applying the powder brazing material on the ceramic member with a predetermined thickness, and a second step of installing the metal member on the powder brazing material. And a third step of heat bonding with a predetermined heating profile.

In the first step, the powder brazing material is a mixture of an organic binder or a brazing material alone with a predetermined film thickness on the ceramic member in order to keep the molding on construction. The organic binder in this case may be a binder that is usually used in joining using a brazing material, and examples thereof include, but are not limited to, a mixture of a hydrogenated product, paraffin, cellulose, and various solvents. . Further, the coating film thickness can be appropriately determined by those skilled in the art depending on the intended bonding strength and airtightness, and can be, for example, 10 to 1000 μm. Next, in the second step, a metal member is placed on the powder brazing material. In the third step, the powder brazing material on the ceramic member is fired according to a predetermined heating profile. The heating profile in this case may be appropriately provided with a heating rate and a holding time so that the heating profile sufficiently follows the object to be joined. Moreover, it is preferable that the atmosphere at the time of joining shall be about 10 < ^-3 > Pa or less, for example. This is to prevent oxidation of the active metal. However, since the powder brazing material of the present invention has improved oxidation resistance as compared with the powder brazing material according to the prior art, strict conditions are not required. For example, a high vacuum atmosphere has been conventionally required, but a low vacuum condition of about 1 × 10 ^{−2 to} 5 × 10 ⁻² Pa can be allowed.

  In the powder brazing filler metal according to the first embodiment, since the active metal core is present alone, the diffusion of the active metal to the outer surface during heating is suppressed, so that the active metal is oxidized before reaching the joining temperature. The suppressed state can be maintained for a long time.

[Second Embodiment: Powder Brazing Material (Solid Solution, Compound Active Metal Core)]
FIG. 2 is a schematic cross-sectional view showing a powder brazing material according to the second embodiment. The powder brazing material 200 according to the second embodiment is formed of two layers of an active metal core 21 and an outer shell layer 23. In the present embodiment, the active metal core 21 is mainly composed of an active metal dissolved in Cu or a compound of Cu and an active metal. The outer shell layer 23 is mainly composed of Ag.

In the present embodiment, in the powder brazing material 200, the active metal, Cu, and Ag may be present in the same mass ratio as exemplified in the first embodiment. However, in the active metal core 21, the active metal is substantially uniformly dissolved in Cu or forms a compound with Cu, and the active metal core 21 is directly covered by the outer shell layer 23. This is different from the first embodiment. Specific Cu and active metal solid solutions include, but are not limited to, Cu-0.001% Ti. Specific compounds of Cu and active metals include, but are not limited to, CuTi, CuTi ₂ , Cu ₄ Ti ₃ , Cu ₃ Ti ₂ , Cu ₄ Ti, and the like. In this case, the maximum diameter of the active metal core 21 is larger than that of the first embodiment, and the active metal core 21 and the intermediate layer in the first embodiment are combined. Therefore, the maximum diameter of the active metal core 21 in the second embodiment is preferably 2 to 150 μm, and more preferably 3 to 50 μm. The shape and internal form of the active metal core may be the same as in the first embodiment. The outer diameter of the powder brazing material 200 according to the present embodiment may be in the same range as in the first embodiment.

  Next, the powder brazing material 200 according to the present embodiment will be described from the viewpoint of its manufacturing method. The method of manufacturing the powder brazing material 200 includes a first step of manufacturing an active metal core 21 by dissolving an active metal in Cu or preparing a compound of Cu and an active metal, and a solid solution active metal core. 21 is covered with Ag, and the outer shell layer 23 is formed. The first step of dissolving an active metal in Cu or preparing a compound of Cu and an active metal can be performed based on techniques known to those skilled in the art. The second step can be performed in the same manner as the second step and the third step of the first embodiment. Moreover, about the usage method of the powder brazing material 200 by this embodiment, it can be made the same as that of 1st Embodiment.

  The powder brazing filler metal 200 according to the second embodiment has an active metal core that can be stably obtained without generating an oxide by an easier manufacturing method, and has an oxidation resistance of the active metal, and has good bonding. This is advantageous in that it becomes possible.

[Third embodiment: joined body]
The present invention is a joined body according to the third embodiment, and is formed by joining a metal member and a ceramic member with the powder brazing material according to the first embodiment or the second embodiment.

  The metal member and the ceramic member according to the present embodiment may be various metals, alloys, and ceramics that can be joined as described in the first embodiment. The joined body may be, for example, various products and parts of products that require high heat resistance and joining strength, and is not particularly limited. Below, the member which comprises a vacuum vessel is mentioned and demonstrated as an example of a conjugate | zygote.

  FIG. 3 is a conceptual cross-sectional view showing a vacuum vessel including the joined body according to the present embodiment as a constituent element. In the vacuum vessel 300, the upper and lower ends of the vacuum vessels 301A and 301B and the metal flanges 311A and 311B are joined by the powder brazing material 100 according to the first embodiment.

  The vacuum vessel 300 shown in FIG. 3 will be briefly described. The vacuum vessels 301A and 301B made of insulating cylinders are hermetically joined through ring-shaped attachment portions 316, and the upper and lower ends thereof are hermetically sealed by metal flanges 311A and 311B, respectively. It is sealed. The cylindrical arc shield 304 is supported by a support fitting 305 that is integral with the mounting portion 316, and a fixed contact 302 </ b> A and a movable contact 302 </ b> B are disposed inside the arc shield 304 so as to be able to contact and separate. The upper surface of the fixed contact 302A is joined to the fixed rod 303A, and the upper end of the fixed rod 303A penetrates the metal flange 311A in an airtight manner and is drawn to the outside. On the other hand, the lower surface of the movable contact 302B is joined to the movable rod 303B, and the lower end of the movable rod 303B is pulled out to the outside airtightly through a bellows 306 that is airtightly joined to the metal flange 311B. A cup-shaped bellows cover 307 is attached to the lower surface of the movable contact 302B so as to cover the bellows 306. The vacuum vessel shown in FIG. 3 and its application and operation are described in detail in Japanese Patent Application Laid-Open No. 2000-294089 by the present applicants.

The joining of the upper and lower ends of the vacuum vessels 301A and 301B and the metal flanges 311A and 311B with the powder brazing material 100 is performed in a joining process by heating under a low vacuum condition, for example, 1 × 10 ^{− It} can be carried out in the same manner as in the prior art except that it can be carried out at ^{2 to} 5 × 10 ⁻² Pa. In addition, in joining the vacuum vessels 301A and 301B shown in FIG. 3 and the metal flanges 311A and 311B, the powder brazing material 200 according to the second embodiment may be used instead of the powder brazing material 100 according to the first embodiment. it can.

  The joined body according to the present embodiment uses the powder brazing material 100, 200 according to the first embodiment or the second embodiment, so that the joining process in the production of the joined body is performed under a low vacuum condition as compared with the conventional case. This is advantageous in that it can prevent bonding failure and the like.

  Hereinafter, the present invention will be described in detail with reference to examples. The following examples do not limit the invention.

[Example 1]
The powder brazing material according to the first embodiment is manufactured. The active metal core is made of titanium metal alone, and the mass ratio of Ti: Cu: Ag is 3:30:70. A 0.8 μm Cu coating layer is provided on a spherical active metal core with a diameter of 2 μm made of a single titanium metal by an electroless plating method to form an intermediate layer. Further, a 0.7 μm Ag coating layer is provided on the Cu intermediate layer, and an outer shell layer is formed to produce a powder brazing material. When the outer diameter (maximum diameter) of this powder brazing material is measured by a laser diffraction method, it can be seen that a powder brazing material having a diameter of 5 μm is obtained. In addition, by analyzing each powder by energy dispersive X-ray analysis (EDS), almost no oxide film (TiO ₂ ) is generated on the active metal core of a spherical titanium metal having a diameter of about 2 μm. It can be observed that a coating layer of Cu is provided, and an outer shell layer of Ag is further provided, resulting in the form shown in FIG.

[Comparative example]
A powder brazing material according to a comparative example is produced. The powder brazing material according to the comparative example has the same mass ratio and diameter of Ti: Cu: Ag as in Example 1, but does not have a layer structure, and these constituent elements are present uniformly in the powder. Shall.

The powder brazing materials of Example 1 and Comparative Example are heated on an alumina (Al ₂ O ₃ ) substrate at a predetermined temperature and time profile, and wetting spread is evaluated. The heating temperature profile is shown in Table 1 below and FIG. The atmosphere during heating is 1 × 10 ⁻² (Pa).

  The phenomenon that occurs during joining using the powder brazing material according to Example 1 and the powder brazing material according to the comparative example will be described along a time series. A schematic conceptual diagram in this case is shown in FIG.

  Fig.5 (a) is a conceptual diagram which shows the change along a time series at the time of heating the active metal powder brazing material of Example 1 by the heating temperature profile shown in the said Table 1 and FIG. (1) is the active metal powder brazing material 100 of Example 1 in the initial state before heating on the alumina substrate 400. The active metal powder brazing material 100 of Example 1 is hardly affected by oxidation due to the atmosphere by using the active metal core 11 sensitive to oxidation as the core of a sphere. In the temperature raising process at 400 to 600 ° C. (corresponding to Steps 1 to 4) shown in (2), a CuTi solid solution 15 is formed inside the brazing material, or a compound of Cu and Ti is formed, and Cu and Ag and In the vicinity of the interface, Ag—Cu eutectic 14 is formed. In the state immediately above the solid phase line shown in (3) (corresponding to Steps 6 to 7), the Ag phase still maintains the solid phase, but the Ag-Cu eutectic 14 and Ti partially melt to produce the L phase 17. . In the solid phase line to the liquid phase line (corresponding to Steps 6 to 7) shown in (4), when the temperature rises and becomes higher than the solid phase line, Ag, Cu and Ti are partially formed in the L layer 17 (liquid phase). Thus, the formation of the Ag—Cu eutectic 14 is brought into an equilibrium state, and the Ti reaction layer 16 is formed on the alumina substrate 400. The formation of the Ti reaction layer 16 improves the wettability. In any of (2) to (4), Ag in the outer shell layer 13 stably exists as a metal rather than an oxide in the heated state, so that no oxidation occurs in the brazing material outer shell layer 13. On the liquid phase line shown in (5) (corresponding to Steps 7 to 8), the Ti reaction layer 16 is formed on the entire surface of the alumina substrate 400 as the temperature further increases. Then, wetting of the Ag phase + Ag—Cu eutectic 18 onto the formed Ti reaction layer 16 occurs.

  FIG. 5B is a conceptual diagram showing changes in time series when the active metal powder brazing material of the comparative example is heated by the heating temperature profile shown in Table 1 and FIG. (1) is the active metal powder brazing material 50 of the comparative example in the initial state before heating. In the active metal powder brazing material 50 of the comparative example, Ag, Cu, and Ti are present substantially uniformly in the spherical powder. In the temperature raising process at 400 to 600 ° C. (corresponding to Steps 1 to 4) shown in (2), since Ti is uniformly dispersed in the brazing material, dissolved in the atmosphere or in the brazing material Ti oxide film 51 is densely formed on the surface of the brazing material by diffusion of oxygen or the like, and the oxide film 51 becomes thicker as the temperature rises. In the state immediately above the solid phase line shown in (3) (corresponding to Steps 6 to 7), it becomes the AgCu eutectic L phase 52, and the Ti oxide film is formed even at the temperature at which the AgCu phase becomes liquefied. Without mixing with the surrounding brazing material, the spherical shape is maintained, and Ti necessary for forming the reaction layer with the alumina substrate 400, which is the key to joining, is consumed. In the state of solid phase line to liquid phase line shown in (4) (corresponding to Steps 6 to 7), the state shown in (3) is maintained and no reaction layer is formed, so that the brazing material gets wet on the alumina substrate 400. The brazing material remains spherical. As a result, there is no change even when the state is just above the liquidus line shown in (5) (corresponding to Steps 7 to 8), resulting in poor bonding.

[Example 2]
The powder brazing material according to the second embodiment is manufactured. The active metal core is a compound of Ti and Cu (chemical formula: Cu ₄ Ti, Cu ₃ Ti ₂ ), and the mass ratio of Ti: Cu: Ag is 3:30:70. The active metal core can be prepared using an electron beam melting furnace or the like.

An approximately spherical active metal core mainly composed of a compound of Ti and Cu is provided with a 0.7 μm Ag coating layer by an electroless plating method, and an outer shell layer is formed to produce a powder brazing material. When the outer diameter (maximum diameter) of this powder brazing material is measured by a laser diffraction method, it can be seen that a 5 μm powder brazing material is obtained. Further, by analyzing individual powders by energy dispersive X-ray analysis (EDS), an oxide film (TiO ₂ ) is not formed on the active metal core of a spherical CuTi compound having a diameter of about 3.6 μm. It can be observed that a layer of Ag is provided and the configuration shown in FIG.

The powder brazing material thus obtained is heated on an alumina (Al ₂ O ₃ ) substrate with the same temperature profile as in Example 1 to evaluate the wetting and bonding interface. The powder brazing material according to Example 2 also changes substantially in the same manner as in FIG. 5A, the Ti reaction layer is formed on the entire surface of the ceramic, and the brazing material and the alumina substrate are joined.

  The powder brazing material according to the present invention can be preferably used for joining members such as a vacuum vessel, a vacuum valve, and an HC contactor that require characteristics of high joining strength and high airtightness.

Powder brazing material 100, 200
Active metal core 11, 21
Middle layer 12
Outer shell layer 13, 23
Vacuum container 300

Claims (9)

One or more active metals selected from titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), and chromium (Cr), silver (Ag), and copper (Cu) A powder brazing material comprising:
The powder brazing material is a powder brazing material having a layer structure of two or more layers including an active metal core in which the active metal is localized and an outer shell layer.   The powder brazing material according to claim 1, wherein the silver (Ag) is present as a main component in the outer shell layer.   The active metal core is one in which the active metal existing as a pure metal is localized, and the active metal is contained in an amount of 1 to 5% by mass with respect to the total mass of the powder brazing material. The powder brazing material according to 2.   The active metal core is obtained by localizing a hydride of the active metal or an alloy of the active metal and palladium (Pd), and the active metal is 1 to 1 based on the total mass of the powder brazing material. The powder brazing material according to claim 1 or 2, comprising 5% by mass. Further comprising an intermediate layer between the active metal core and the outer shell layer;
The powder brazing material according to any one of claims 1 to 4, wherein the copper (Cu) is present as a main component in the intermediate layer.   The active metal core is a solid solution of the active metal and copper (Cu) or a compound of the active metal and copper (Cu) localized, and the active metal is the entire powder brazing material. The powder brazing material according to claim 1 or 2, which is contained in an amount of 1 to 5 mass% based on the mass.   The powder brazing material according to any one of claims 1 to 6, wherein the active metal core has a spherical shape, a foil shape, or a piece shape, and a maximum diameter of the active metal core is 0.1 µm to 150 µm.   A joined body formed by joining a metal member and a ceramic member with the powder brazing material according to claim 1.   A vacuum vessel formed by bonding with the powder brazing material according to claim 1.

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