Metal / ceramic joined body, brazing material, method for producing metal / ceramic joined body, and method for producing brazing material

Abstract

Disclosed is a metal / ceramic joined body which has a metal member, a ceramic member that is joined to the metal member, and a bonding layer that is formed on the joined surface between the metal member and the ceramic member, the bonding layer containing Cu and Mg, and additionally containing at least one active metal element that is selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er. The bonding layer has a non-layered MgO phase that contains MgO.

Description

Metal / ceramic bonded body, brazing filler metal, method for manufacturing metal / ceramic bonded body, and method for manufacturing brazing filler metal

[0001] The present disclosure relates to a metal / ceramic bonded body, a brazing filler metal, a method for manufacturing a metal / ceramic bonded body, and a method for manufacturing a brazing filler metal.

[0002] Demand for bonded structures (metal / ceramic bonded structures) formed by bonding metal and ceramic members is increasing as insulating circuit boards for power electronics semiconductor devices, such as inverters and converters, and the trend toward higher current densities and smaller sizes is advancing. This increases the thermal stress that generates, necessitating long-life, high-strength circuit boards, and ultimately high-strength metal / ceramic joints.

[0003] For joining metals and ceramics, particularly insulated circuit boards used in semiconductor devices, a joining method known as DCB (Direct Copper Bonding) is used, in which a eutectic of copper (Cu) and copper oxide (CuO) is used to directly heat-bond Cu to oxide ceramics, and a joining method known as AMB (Active Metal Brazing) is used, in which an active metal brazing material is used.

[0004] Among these, the AMB method has attracted attention as a joining method that can obtain high joining strength, and a Ag-Cu-Ti based brazing filler metal is used as a typical joining material. For example, in Patent Document 1, after an Ag-Cu-Sn-Ti based brazing filler metal is placed on a ceramic substrate, Cu is laminated and a 1.0 × 10 －３ A metal / ceramic bonded body is obtained by performing a heat treatment at 780° C. to 850° C. in a vacuum of 100 Pa or less.

[0005] For example, Patent Document 2 proposes a ceramic circuit board in which a copper plate and a ceramic substrate are joined using a Cu-Mg-Ti based brazing filler metal. According to Patent Document 2, a metal / ceramic joined body can be obtained by laminating a Cu plate and a ceramic substrate with an active metal foil and a magnesium (Mg) foil interposed therebetween, and then heat treating the laminate at a temperature in the range of 700°C to 830°C.

[0006] Patent No. 6743073 International Publication No. 2021 / 033421

[0007] At the interface between metal and ceramics, which is bonded using a bonding method using an active metal brazing material, the active metal reacts with the ceramic to form an interfacial reaction layer, which can provide a bonded body with a certain degree of high bonding strength and reliability. However, because the metal and ceramic members have significantly different thermal expansion coefficients, strain and defects can increase in the bonding layer disposed between the metal and ceramic members, which can lead to a decrease in bonding strength and reliability.

[0008] As in Patent Document 1, Cu and aluminum nitride (AlN) or silicon nitride (Si ３ N ４ ) is joined using a Ag-Cu-Sn-Ti brazing filler metal, Cu and Si ３ N ４ Compared with the thermal expansion coefficient of the bonding layer placed between the Si ３ N ４ The thermal expansion coefficient of the SiO2 is low, which may cause problems with reliability in thermal cycle tests (hereinafter referred to as thermal cycle reliability).

[0009] Furthermore, as in Patent Document 2, by dispersing an active metal oxide phase with a low thermal expansion coefficient in the bonding layer, it is possible to alleviate thermal stress caused by the difference in thermal expansion coefficient between the copper member and the ceramic member. However, since a magnesium oxide (MgO) layer that is prone to brittle fracture is formed in a layered form between the copper member and the ceramic member, there is a possibility that the bonding strength will be reduced.

[0010] An object of the present disclosure is to provide a metal / ceramic bonded body having high bonding strength and high thermal cycle reliability.

[0011] According to one aspect of the present disclosure, there is provided a metal / ceramic bonded body comprising: a metal member; a ceramic member bonded to the metal member; and a bonding layer formed on a bonding surface between the metal member and the ceramic member, the bonding layer containing Cu and Mg and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er, wherein a non-lamellar MgO phase containing MgO is present in the bonding layer.

[0012] According to another aspect of the present disclosure, there is provided a brazing filler metal used for joining a metal member and a ceramic member, the brazing filler metal containing 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total amount of 0.1 to 10 at %, wherein at least a portion of the Mg is contained in the form of MgO, and the Cu and Mg are contained in a state where the average particle size is 45 μm or less.

[0013] According to yet another aspect of the present disclosure, there is provided a method for producing a metal / ceramic joined body, the method comprising: arranging a metal member and a ceramic member so as to be stacked with a brazing filler metal therebetween; and heating and holding the laminate of the metal members and the ceramic members while applying pressure in the stacking direction, wherein the brazing filler metal contains 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total amount of 0.1 to 10 at %, at least a portion of the Mg is contained in the form of MgO, and the Cu and the Mg have an average particle size of 45 μm or less; and performing a hydrogen reduction treatment on the brazing filler metal.

[0014] According to the present disclosure, it is possible to provide a metal / ceramic bonded body having high bonding strength and high thermal cycle reliability.

[0015] FIG. 1 is a partial cross-sectional schematic diagram of a metal / ceramic bonded body 100 according to one embodiment of the present disclosure. FIG. 2 is a cross-sectional photograph (SEM image) of the first layer 31 and its surroundings. FIG. 3 is an enlarged photograph (STEM image) of the MgO phase 33. FIG. 4 is an electron energy loss (EELS) spectrum of the MgO phase 33 analyzed using a scanning transmission electron microscope. FIG. 5(a) is a schematic diagram showing shear stress applied to the bonding layer 30, and FIG. 5(b) is a schematic diagram showing tensile stress applied to the bonding layer 30. FIG. 6(a) shows a state in which the metal member 10 and the ceramic member 20 are arranged via the brazing material 50. FIG. 6(b) shows a state in which the laminate of the metal member 10 and the ceramic member 20 is heated while being pressurized. FIG. 6(c) shows the manufactured metal / ceramic bonded body 100. FIG. 7 is a cross-sectional photograph of the bonding layer in which a large void 34L is generated. FIG. 8 is a diagram schematically showing how a shear strength test is carried out.

[0016] <One Aspect of the Present Disclosure> One aspect of the present disclosure will be described below with reference to the above-mentioned drawings. Note that all drawings used in the following description are schematic. The dimensions and proportions of each element shown in the drawings do not necessarily correspond to the actual dimensions. Furthermore, the dimensions and proportions of each element do not necessarily correspond between drawings. Note that in this specification, "A to B" means a numerical range of "greater than or equal to A and less than or equal to B."

[0017] (1) Configuration of Metal / Ceramic Bonded Body As shown in FIG. 1 , a metal / ceramic bonded body 100 includes a metal member 10, a ceramic member 20 bonded to the metal member 10, and a bonding layer 30 formed on the bonding surfaces between the metal member 10 and the ceramic member 20.

[0018] The metal member 10 may be made of, for example, pure copper, a copper alloy, pure nickel, or a nickel alloy. Examples of pure copper include oxygen-free copper, tough-pitch copper, and phosphorus-deoxidized copper. Examples of copper alloys include alloys containing copper (Cu) as the main element and at least one element selected from the group consisting of zinc (Zn), tin (Sn), phosphorus (P), aluminum (Al), beryllium (Be), cobalt (Co), nickel (Ni), iron (Fe), and manganese (Mn). The shape and dimensions of the metal member 10 are not particularly limited. However, when the metal / ceramic bonded body 100 is used as a constituent material for an insulated circuit board, the metal member 10 may be, for example, a flat plate having a thickness ranging from 0.1 mm to 4.0 mm. In this embodiment, the metal member 10 is made of pure copper.

[0019] The ceramic member 20 is made of, for example, silicon nitride (Si ３ N ４ ), aluminum nitride (AlN), silicon carbide (SiC), aluminum oxide (Al ２ O ３ ), diamond, etc. There are no particular limitations on the shape or dimensions of the ceramic member 20, but when the metal / ceramic bonded body 100 is used as a constituent material of an insulating circuit board, it can be a flat plate having a thickness in the range of 0.2 mm to 4.0 mm, for example. In this embodiment, the ceramic member 20 is made of silicon nitride (Si ３ N ４ ) will be explained.

[0020] A bonding layer 30 is formed between the metal member 10 and the ceramic member 20 along their bonding surfaces 10s, 20s. The bonding layer 30 contains copper (Cu) and magnesium (Mg), and further contains at least one active metal element selected from the group consisting of titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), calcium (Ca), yttrium (Y), cerium (Ce), lanthanum (La), samarium (Sm), ytterbium (Yb), neodymium (Nd), gadolinium (Gd), erbium (Er), and the like. Note that when the ceramic member 20 is Si ３ N ４ In the case of AlN or AlN, it is particularly preferable to use Ti, V, Nb, Cr, Mo, or Ca as the active metal element, and Ti is particularly preferable. In this embodiment, the case where Ti is used as the active metal element will be described.

[0021] As described below, the bonding layer 30 is formed by a brazing filler metal 50 containing Cu, Mg, and the above-described active metal elements in predetermined proportions, reacting with the metal member 10 and the ceramic member 20. The brazing filler metal 50 used in this embodiment is a Cu-Mg-based brazing filler metal that does not contain Ag, and contains, for example, 50 to 80 at% Cu, 5 to 20 at% Mg, and 0.1 to 10 at% active metal elements (Ti in this embodiment) in total. In other words, the brazing filler metal 50 used in this embodiment contains 5 to 20 at% Mg, 0.1 to 10 at% active metal elements in total, and the remainder (excluding inevitable impurities) is Cu. By using such a brazing filler metal 50 and performing bonding using the method described below, the bonding layer 30 in this embodiment exhibits the following various characteristics.

[0022] 1, the bonding layer 30 has a laminated structure of a first layer 31 that forms an interface with the metal member 10, and a second layer 32 that forms an interface with the ceramic member 20 and is in contact with the first layer 31. The thickness of the first layer 31 is, for example, 1 to 2000 μm, and the thickness of the second layer 32 is, for example, 1 to 2000 nm.

[0023] Fig. 2 is a cross-sectional photograph (SEM image) of the first layer 31 and its surroundings. As shown in Fig. 2, the first layer 31 has a solid solution phase 31A (the light gray portion in the figure) and a compound phase 31B (the dark gray portion in the figure).

[0024] The solid solution phase 31A is mainly composed of a solid solution of Mg dissolved in Cu crystals. The solid solution phase 31A may further contain active metal elements such as Ti contained in the brazing filler metal 50, and Si and Al contained in the ceramic member 20.

[0025] The compound phase 31B is an intermetallic compound containing Cu and Mg, for example, a compound having the composition formula MgCu ２ The compound phase 31B may further contain an intermetallic compound containing the above-mentioned active metal element precipitated therein. When Ti is selected as the active metal element, the intermetallic compound containing the active metal element may contain a compound represented by the composition formula Cu ４ Ti, Cu ３ Ti ２ , Cu ２ Ti, Cu ４ Ti ３ ,CuTi,CuTi ２ , Ti ５ Si ３ , Ti ３ At least one compound selected from the group of compounds represented by Si, CuTiSi, etc. may be mentioned.

[0026] As shown in FIG. 2 , the bonding layer 30 (first layer 31) contains a non-lamellar MgO phase 33 containing magnesium oxide (MgO) (e.g., the outer peripheral portion of the region indicated by the radius R in FIG. 2 ). In other words, the MgO phase 33 is not concentrated in a specific region of the bonding layer 30 (first layer 31), but is dispersed in both the thickness direction and the surface direction (the direction of the bonding surfaces 10s and 20s) of the bonding layer 30. Furthermore, as shown in FIG. 2 , the MgO phase 33 preferably extends in a curved manner without forming large clumps. The presence of the MgO phase 33 in the bonding layer 30 (particularly the first layer 31) in this manner can mitigate thermal stress caused by the difference in thermal expansion coefficients between the metal member 10 and the ceramic member 20, thereby improving bonding strength and thermal cycle reliability. The MgO phase 33 is not shown in FIG. 1 .

[0027] As shown in FIG. 2 , the MgO phase 33 preferably exists in a shell-like manner, surrounding at least one of the solid solution phase 31A and the compound phase 31B. The presence of the MgO phase 33 in this manner reduces thermal stress between the solid solution phase 31A and the compound phase 31B, thereby improving bonding strength and thermal cycle reliability. The phrase "surrounding at least one of the solid solution phase 31A and the compound phase 31B" refers to the case where the MgO phase 33 forms a closed space (a closed curve in a cross-sectional photograph) and completely surrounds a certain region, as well as the case where the MgO phase 33 is absent from a portion of the periphery of the region. In this specification, for example, if the MgO phase 33 covers 80% or more of the surface area of ​​the region (the periphery in a cross-sectional photograph), the MgO phase 33 is said to exist in a manner surrounding the region.

[0028] In the region surrounded by the MgO phase 33, the proportion of the solid solution phase 31A (e.g., area proportion in the cross section) is preferably 90% or more, or the proportion of the compound phase 31B (e.g., area proportion in the cross section) is preferably 90% or more. This means that a large amount of the MgO phase 33 is present at the boundary between the solid solution phase 31A and the compound phase 31B. The presence of the MgO phase 33 in this manner can mitigate the generation of thermal stress between the solid solution phase 31A and the compound phase 31B, thereby further improving the bonding strength and thermal cycle reliability.

[0029] The diameter R of the region surrounded by the MgO phase 33 is preferably, for example, 1 μm or more and 20 μm or less. This can further improve the bonding strength and thermal cycle reliability. The diameter R may also be the equivalent circle diameter of the region surrounded by the MgO phase 33 in the cross-sectional photograph shown in FIG.

[0030] Fig. 3 is an enlarged photograph (STEM image) of the MgO phase 33. As shown in Fig. 3, the MgO phase 33 is preferably formed by a large number of MgO particles connected together. The thickness d of the MgO phase 33 is preferably, for example, 10 nm or more and 1 µm or less. Furthermore, the particle size of the MgO particles in the MgO phase 33 is preferably, for example, 10 nm or more and 30 nm or less. This can further improve the bonding strength and thermal cycle reliability.

[0031] It is preferable that the MgO phase 33 is uniformly dispersed in the first layer 31. Specifically, for example, ２ When the area ratio of the MgO phase 33 in the region is measured multiple times (e.g., three times) in different observation fields, it is preferable that the difference between the maximum and minimum values ​​of the area ratio of the MgO phase 33 be within 5%. This can further improve the bonding strength and thermal cycle reliability. When measuring the area ratio of the MgO phase 33 in the cross section of the first layer 31, for example, it may be calculated by image analysis of a cross-sectional photograph such as that shown in FIG. 2, or the area of ​​the MgO phase 33 may be calculated as the product of the sum of the circle-equivalent diameters R of the regions surrounded by the MgO phase 33 and the average thickness d of the MgO phase 33.

[0032] In the cross section of the first layer 31 (for example, a cross section of 500 μm ２ In the region ( ), the area ratio of the MgO phase 33 is preferably, for example, 0.4% or more and 15% or less. If the area ratio of the MgO phase 33 is less than 0.4%, the effect of improving the bonding strength may be insufficient. In contrast, by setting the area ratio of the MgO phase 33 to 0.4% or more, the bonding strength can be sufficiently improved. On the other hand, if the area ratio of the MgO phase 33 exceeds 15%, the effect of improving the thermal cycle reliability may be reduced. In contrast, by setting the area ratio of the MgO phase 33 to 15% or less, the thermal cycle reliability can be sufficiently improved.

[0033] Fig. 4 shows an example of an electron energy loss (EELS) spectrum analyzed by a scanning transmission electron microscope for the MgO phase 33. When the EELS analysis is performed on the MgO phase 33, it can be confirmed that the spectrum has peaks (indicated by arrows in the figure) in the ranges of 50 to 80 eV and 530 to 560 eV, respectively.

[0034] When joining the metal member 10 and the ceramic member 20 using a brazing filler metal containing Mg, there is a concern that evaporation of the Mg contained in the brazing filler metal may cause voids or pinholes (hereinafter, these will be collectively referred to as voids) to occur in the first layer 31. Fig. 7 shows an example of a cross-sectional photograph of the joining layer containing a void 34L generated due to evaporation of Mg, etc. In Fig. 7, a void 34L of approximately 3500 μm ２ Within the field of view, the presence of voids 34L with an equivalent circle diameter (the diameter of a circle having an area equal to the cross-sectional area of ​​the voids 34L) of 8 μm or more can be confirmed. Note that the equivalent circle diameter of the void 34L in the upper right of FIG. 7 is about 9 to 10 μm, the equivalent circle diameter of the void 34L in the upper left is 5 μm or more, and the equivalent circle diameter of the void 34L in the lower left is about 3 to 4 μm.

[0035] The presence of such large voids 34L is a factor that reduces the bonding strength between the metal member 10 and the ceramic member 20. If a brazing filler metal containing Mg and the above-mentioned active metal element in simple form but not Cu is used to bond the metal member 10 and the ceramic member 20, the Mg contained in the brazing filler metal will evaporate violently, and the generation of voids 34L with a circle equivalent diameter exceeding 8 μm in the first layer 31 will be unavoidable, resulting in a significant reduction in the bonding strength between the metal member 10 and the ceramic member 20. In this case, bonding between the metal member 10 and the ceramic member 20 itself may become impossible.

[0036] In response to such issues, in this embodiment, by using a brazing filler metal 50 that not only contains Mg and an active metal element but also Cu in the above-mentioned proportions during joining, it is possible to sufficiently suppress the appearance of large voids 34L, for example, voids 34L having a circle equivalent diameter of 8 μm or more, in the joining layer 30.

[0037] For example, in FIG. 2, the ２ Within the field of view, no voids 34L having a circular equivalent diameter of 8 μm or more were observed, and only one void 34S having a circular equivalent diameter of about 1 to 2 μm was observed.

[0038] As described above, when the first layer 31 of the bonding layer 30 in this embodiment is observed in a cross section perpendicular to the bonding surfaces 10s and 20s, the thickness of the first layer 31 is approximately 10,000 μm. ２ In other words, when the first layer 31 is observed in a cross section perpendicular to the bonding surfaces 10s and 20s, the number of voids 34L having a circle-equivalent diameter of 8 μm or more is 10,000 μm or more. ２ There is less than one per

[0039] In this embodiment, when observing the first layer 31 in a cross section perpendicular to the bonding surfaces 10s and 20s, even if voids 34S are observed, their equivalent circular diameter is less than 8 μm, for example, less than 5 μm, and preferably less than 3 μm.

[0040] In this embodiment, when the first layer 31 is observed in a cross section perpendicular to the bonding surfaces 10s and 20s, voids 34S having a circle equivalent diameter of less than 8 μm, for example, voids 34S having a circle equivalent diameter of more than 2 μm and less than 8 μm, may be observed. However, the number of voids 34S is not more than approximately 10,000 μm. ２ In this embodiment, the number of voids 34S having a circle equivalent diameter of 1 μm or more and 2 μm or less may be observed, but the number of voids 34S is limited to approximately 10,000 μm. ２ In any given field of view, the number of particles is extremely small, 20 or less, preferably 10 or less.

[0041] Of the bonding layer 30, the second layer 32 constituting the interface with the ceramic member 20 is mainly composed of titanium nitride (TiN), which is a nitride of an active metal element (Ti in this embodiment). When the ceramic member 20 is made of silicon nitride, the second layer 32 contains a compound of the composition formula Ti ５ Si ３ The active metal compound (for example, TiN) in the second layer 32 exists in the form of a layer along the interface with the ceramic member 20, for example.

[0042] The second layer 32 has a composition formula of MgSiN ２ The nitride crystals X may contain nitride crystals X represented by the formula: ##STR1## The nitride crystals X may be unevenly distributed in the second layer 32, for example, near the interface with the ceramic member 20. When the thickness of the second layer 32 is Tx, the thickness of the region where the nitride crystals X are unevenly distributed is about 5% to 50%, preferably about 10 to 40% of Tx. For example, when the thickness Tx of the second layer 32 is about 250 nm, the thickness of the region where the nitride crystals X are unevenly distributed is about 10 to 150 nm, preferably about 20 to 100 nm. The presence of nitride crystals X can be confirmed by, for example, crystal analysis of the second layer 32 using a transmission electron microscope with precession electron diffraction (TEM-PED). The second layer 32 in this embodiment has a composition formula of Mg ３ N ２In this embodiment, the nitride crystal Y is not confirmed even when analyzed by the TEM-PED method.

[0043] In this embodiment, the second layer 32 may contain MgO. Since MgO has a lattice constant close to that of TiN or Cu, the inclusion of MgO in the second layer 32 can alleviate stress due to lattice constant mismatch and improve the bonding strength between the metal member 10 and the ceramic member 20.

[0044] In this embodiment, the second layer 32 may further contain a silicide or an aluminide of an active metal element. ３ N ４ In the case where the second layer 32 is made of Ti ５ Si ３ In the case where the ceramic member 20 is made of AlN, the second layer 32 may contain an aluminide of an active metal element such as TiAl. ５ Si ３ The case where Ti ５ Si ３ Such a silicide or aluminide of an active metal element may be present, for example, in a region of the second layer 32 from the interface with the first layer 31 to 60% of the thickness Tx of the second layer 32.

[0045] In the second layer 32, MgO is ５ Si ３ It is preferable that MgO is not substantially dispersed in the target region (i.e., in the silicide or aluminide of the active metal element). In this specification, "substantially no MgO is dispersed" does not only mean a case where no MgO is dispersed in the target region at all, but also a case where only a trace amount of MgO (for example, less than 5% of the ratio of MgO contained in the second layer 32) is dispersed. In addition, the nitride crystal X described above also contains Ti ５ Si ３ Preferably, the active metal element is not substantially dispersed in the silicide or aluminide of the active metal element.

[0046] The second layer 32 may further include a Cu phase. When the second layer 32 includes a Cu phase, it is preferable that at least a portion of the MgO in the second layer 32 is dispersed (dispersed in islands) in the Cu phase. Since MgO has a lattice constant similar to that of Cu, the dispersion of MgO in the Cu phase can efficiently improve the bonding strength between the metal member 10 and the ceramic member 20. The Cu phase in the second layer 32 may be a phase consisting of simple Cu, or, similar to the solid solution phase 31A of the first layer 31, may be a phase mainly composed of a solid solution in which Mg is solid-dissolved in Cu crystals.

[0047] Nitrides of active metal elements such as TiN may be dispersed (dispersed in islands) near the interface between the first layer 31 and the second layer 32. The TiN present near the interface between the first layer 31 and the second layer 32 may be dispersed, for example, with a diameter of 1 to 30 nm and at intervals of about 50 to 300 nm. Because TiN may be accompanied by MgO, it is possible to alleviate stress caused by a lattice constant mismatch between Cu in the first layer 31 and TiN, thereby further improving the bonding strength between the metal member 10 and the ceramic member 20.

[0048] By virtue of these various features, this embodiment succeeds in significantly improving the bonding strength and thermal cycle reliability between the metal member 10 and the ceramic member 20 .

[0049] Specifically, the shear strength of the bonding layer 30 in this embodiment is 10 MPa or more, preferably 40 MPa or more, and the tensile strength of the bonding layer 30 in this embodiment is 17.3 MPa or more, preferably 86.6 MPa or more.

[0050] The shear strength of the bonding layer 30 refers to the magnitude of shear stress per unit area required to fracture the bonding layer 30 (shear fracture) when stress (shear stress) is applied to the bonding layer 30 so as to displace the metal member 10 and the ceramic member 20 in opposite directions parallel to the bonding surfaces 10s and 20s, as shown in Fig. 5(a). The tensile strength of the bonding layer 30 refers to the magnitude of tensile stress per unit area required to fracture the bonding layer 30 (peeling fracture) when stress (tensile stress) is applied to the bonding layer 30 so as to pull the metal member 10 and the ceramic member 20 apart in a direction perpendicular to the bonding surfaces 10s and 20s, as shown in Fig. 5(b).

[0051] Furthermore, the metal / ceramic bonded body 100 of this embodiment has high thermal cycle reliability. Specifically, for example, when 200 thermal cycles of -50°C for 30 minutes and 150°C for 30 minutes are performed, no cracking of the ceramic member 20 and no peeling of the metal member 10 are observed, demonstrating high thermal cycle reliability. Note that the presence or absence of cracking of the ceramic member 20 and peeling of the metal member 10 can be confirmed by, for example, ultrasonic flaw detection (SAT) testing.

[0052] (2) Method for Manufacturing Metal / Ceramic Bonded Body Next, a method for manufacturing the above-described metal / ceramic bonded body 100 will be described with reference to FIGS. 6(a) to 6(c).

[0053] First, as shown in FIG. 6( a ), the metal member 10 and the ceramic member 20 are arranged so as to be stacked with the brazing material 50 interposed therebetween.

[0054] As described above, the brazing filler metal 50 is a Cu-Mg-based brazing filler metal that does not contain Ag, and for example, a material containing 50 to 80 at % Cu, 5 to 20 at % Mg, and the above-mentioned active metal element (Ti in this embodiment) in a total ratio of 0.1 to 10 at % can be used.

[0055] The Cu contained in the brazing filler metal 50 acts to impart the various characteristics described above to the bonding layer 30 formed by the reaction of the brazing filler metal 50 with the metal member 10 and the ceramic member 20. Furthermore, the Mg contained in the brazing filler metal 50 acts to improve the wettability between the metal member 10 and the brazing filler metal 50 and the wettability between the ceramic member 20 and the brazing filler metal 50 in a balanced manner when bonding the metal member 10 and the ceramic member 20. Furthermore, the active metal element contained in the brazing filler metal 50 reacts with the ceramic member 20 to form a second layer 32, thereby improving the bonding strength between the bonding layer 30 and the ceramic member 20.

[0056] In addition, if the Mg content in the brazing material 50 is less than 5 at %, or the active metal element content is less than 0.1 at %, and the Cu content exceeds 80 at %, the effects of adding Mg or active metal elements described above may not be obtained.

[0057] Furthermore, if the Mg content in the brazing material 50 exceeds 20 at %, or if the total active metal element content exceeds 10 at %, and the Cu content is less than 50 at %, the above-mentioned effect of adding Cu may not be obtained.

[0058] In the brazing material 50, Cu exists in the form of a simple substance (pure Cu), a hydride (CuH), an intermetallic compound with Mg (MgCu ２ The active metal element may be contained in at least one of the following forms: a simple substance (pure Ti), a hydride (TiH ２ ), an intermetallic compound with Cu, or an intermetallic compound with Mg.

[0059] In the brazing filler metal 50 of this embodiment, at least a portion of Mg must be contained in the form of an oxide (MgO). For example, it is preferable that 10 to 50 at % of the Mg contained in the brazing filler metal 50 is contained in the form of MgO. This allows a non-lamellar MgO phase 33 to be formed during joining. Furthermore, the Mg contained in the brazing filler metal 50 may be present in the form of a simple substance (pure Mg), a hydride (MgH２ ), intermetallic compound with Cu (MgCu ２ ), compounds with active metal elements (for example, Mg—Ti compounds), etc. Specifically, for example, by subjecting simple Mg to a surface oxidation treatment in advance, Mg whose surface is covered with MgO can be included in the brazing filler metal 50.

[0060] In the brazing filler metal 50, Cu and Mg must be contained either as simple substances or as an alloy containing Cu and Mg, with small particle sizes (for example, with an average particle size (D50) of 45 μm or less). This increases the surface area, making it easier to absorb oxygen, and allows the formation of a non-lamellar MgO phase 33. There is no particular lower limit to the average particle sizes of Cu and Mg, but it is, for example, 5 μm or more. The average particle size can be measured using a laser diffraction particle size distribution analyzer. In this specification, D50 is considered to be the average particle size.

[0061] Before joining, the brazing filler metal 50 needs to be heat-treated (hydrogen reduction treatment) in a 100% hydrogen atmosphere or a non-oxidizing (inert) atmosphere containing 3 vol. % or more hydrogen. By subjecting the brazing filler metal 50 to hydrogen reduction treatment, the proportion of MgO in the brazing filler metal 50 can be increased. This makes it easier for the non-lamellar MgO phase 33 to form during joining.

[0062] The brazing filler metal 50 may be in the form of a powder, foil, or paste. From the viewpoint of facilitating the formation of the MgO phase 33 as shown in FIG. 2 , a powder or paste form is preferable. When the brazing filler metal 50 is in the form of a paste, the main solvent may be an alcohol such as terpineol or butanediol, or a toluene. The binder may be polyvinyl alcohol, ethyl cellulose, polymethacrylic acid, polyacrylic, or the like. The surfactant may be a cationic, anionic, or nonionic activator. A plasticizer or a dispersant may also be included.

[0063] The brazing material 50 can be placed on the intended joining surfaces 10s', 20s' of the metal member 10 and the ceramic member 20 by known methods such as screen printing, transfer, dispensing, inkjet, spray coating, sputtering, vapor deposition, etc.

[0064] Next, as shown in FIG. 6(b), the laminate 100' of the metal member 10 and the ceramic member 20 arranged with the brazing material 50 interposed therebetween is heated and held in a predetermined atmosphere while being pressurized in the lamination direction. The predetermined atmosphere may be any one of a vacuum atmosphere (reduced pressure atmosphere), an inert gas atmosphere, and a reducing atmosphere. ２ The oxygen concentration can be adjusted by introducing an inert gas such as MgO. When the MgO phase 33 is formed, oxygen is taken from the surroundings of the laminate 100', making it difficult for Cu, Ti, etc. to oxidize, and thus high bonding strength can be maintained.

[0065] The heating temperature during bonding may be, for example, equal to or higher than the melting point of the brazing filler metal 50 and equal to or lower than the melting point of the metal member 10. The temperature is preferably equal to or lower than 115% of the melting point (absolute temperature) of the brazing filler metal 50, and more preferably equal to or higher than 101% and equal to or lower than 110% of the melting point (absolute temperature) of the brazing filler metal 50. This improves the diffusibility of the active metal element, making it easier to form the second layer 32. When using the brazing filler metal 50 of this embodiment, the heating temperature is preferably, for example, equal to or higher than 735°C and equal to or lower than 900°C. The heat treatment furnace used for bonding may be a known furnace, such as a stationary batch furnace, a multi-chamber furnace, or a belt conveyor furnace.

[0066] Other conditions for bonding are exemplified as follows: Oxygen concentration: 0.01 ppm or more and 1000 ppm or less Pressure: 0.5 kPa or more Holding time: not particularly limited, but for example, 3 minutes or more and 120 minutes or less

[0067] During heating, a liquid phase must be formed in a portion of the brazing filler metal 50, and the active metal element must be melted within the liquid phase. This state can be achieved by setting the heating temperature at 735°C or higher. However, if the heating temperature is too high, the evaporation of Mg becomes intense, making it difficult to form a liquid phase or causing voids in the resulting bonding layer 30. Setting the heating temperature at 900°C or lower can avoid these problems. Applying a pressure of 0.5 kPa or higher can maintain the tight contact between the metal member 10 and the ceramic member 20 via the brazing filler metal 50, thereby increasing the bonding strength between the metal member 10 and the ceramic member 20. There is no particular upper limit to the pressure, but it can be set to, for example, approximately 20 kPa.

[0068] Thereafter, the heated laminate 100' is cooled, resulting in a metal / ceramic bonded body 100 having the various characteristics described above, as shown in FIG.

[0069] When the metal / ceramic bonded body 100 is used as an insulated circuit board, etching may be performed after applying an etching resist to the metal member 10 to form a circuit pattern on the metal member 10. The type of etching resist is not particularly limited, and known resists such as heat-curable and ultraviolet-curable resists may be used. The method for applying the etching resist is also not particularly limited, and methods such as applying a film-like resist, screen printing, and inkjet coating may be used. Furthermore, after removing the unnecessary portions of the metal member 10 from the metal / ceramic bonded body 100 by etching, the unnecessary portions of the bonding layer 30 may be further removed.

[0070] (3) Effects According to this aspect, one or more of the following effects can be obtained.

[0071] (a) In this embodiment, the bonding layer 30 (first layer 31) contains a non-lamellar MgO phase 33 containing magnesium oxide (MgO). The presence of the non-lamellar MgO phase 33 in the bonding layer 30 (particularly the first layer 31) can mitigate the generation of thermal stress caused by the difference in thermal expansion coefficient between the metal member 10 and the ceramic member 20, thereby improving the bonding strength and thermal cycle reliability.

[0072] (b) In this embodiment, it is preferable that MgO phase 33 exists so as to surround at least one of solid solution phase 31 A and compound phase 31 B. The existence of MgO phase 33 in such a manner can mitigate the occurrence of thermal stress between solid solution phase 31 A and compound phase 31 B, thereby further improving the bonding strength and thermal cycle reliability.

[0073] (c) In this embodiment, it is preferable that the proportion of the solid solution phase 31A is 90% or more, or the proportion of the compound phase 31B is 90% or more, within the region surrounded by the MgO phase 33. This means that the MgO phase 33 is present in large amounts at the boundary between the solid solution phase 31A and the compound phase 31B. The presence of the MgO phase 33 in this manner reduces the occurrence of thermal stress between the solid solution phase 31A and the compound phase 31B, thereby further improving the bonding strength and thermal cycle reliability.

[0074] (d) In this embodiment, it is possible to dramatically increase the bonding strength between the metal member 10 and the ceramic member 20. For example, it is possible to increase the shear strength of the bonding layer 30 to 10 MPa or more, preferably 40 MPa or more. Also, it is possible to increase the tensile strength of the bonding layer 30 to 17.3 MPa or more, preferably 86.6 MPa or more.

[0075] (e) In this embodiment, it is possible to dramatically improve the thermal cycle reliability of the metal / ceramic bonded body 100. For example, when 200 cycles of a thermal cycle of −50° C. for 30 minutes and 150° C. for 30 minutes are performed, no cracking of the ceramic member 20 and no peeling of the metal member 10 are observed, and high thermal cycle reliability can be achieved.

[0076] Other Aspects of the Present Disclosure The above describes specific aspects of the present disclosure. However, the present disclosure is not limited to the above aspects and can be modified in various ways without departing from the spirit and scope of the present disclosure.

[0077] The metal / ceramic bonded body 100 in this embodiment is not limited to use as an insulated circuit board, but can be widely applied to various uses, such as heat sinks and components of internal combustion engines and power generating machines. In these cases, the same effects as those of the above-described embodiment can be obtained.

[0078] (Production of Samples 1 to 38) As the ceramic member, a 50 mm x 50 mm x 0.32 mm Si ３ N ４ Substrate, 50 mm x 50 mm x 0.635 mm AlN substrate, 50 mm x 50 mm x 0.635 mm Al ２ O ３ A substrate was prepared. The metal member was Si. ３ N ４ The substrates were Cu plates of 48 mm x 48 mm x 0.8 mm, AlN substrates, and Al ２ O ３ A 48mm x 48mm x 0.3mm Cu plate was prepared for the substrate. A paste made by mixing Cu, Mg, and Ti in a predetermined ratio was used as the brazing filler metal. Cu and Mg powders with an average particle size of 45 μm or less were used. Mg was pre-oxidized to form MgO. Polyethylene glycol and diethylene glycol monobutyl ether with a molecular weight of 400 or less were used as solvents, and the solvent ratio in the paste was 9 mass%. The Cu:Mg:Ti element mixing ratio (weight ratio) in the paste was as shown in Tables 1 to 3. This paste was applied to the intended joining surfaces of the ceramic members using screen printing. A metal member was placed directly on the applied paste film and subjected to hydrogen reduction treatment in a 100% hydrogen atmosphere. Samples 1 to 36 were then fabricated by applying a pressure of 8 kPa along the stacking direction and heat-treating the materials for 60 minutes in a vacuum at the predetermined joining temperatures shown in Tables 1 to 3.

[0079] Sample 37 was prepared under the same conditions as Sample 1, except that Cu and Mg powders with an average particle size of approximately 100 μm were used as the raw materials for the brazing material, and the Mg surface oxidation treatment and the brazing material hydrogen reduction treatment were not performed.

[0080] For Sample 38, Cu was not used as the raw material of the brazing material, and a paste made by mixing Mg and Ti powders in an element mixing ratio of 97:3 was used. The other conditions were the same as those for Sample 29.

[0081] (Presence and Aspect of MgO Phase) The presence and aspect of the MgO phase in the bonding layer (first layer) were determined by observing and analyzing the cross section of the bonded body using a scanning electron microscope (SEM) and a scanning transmission electron microscope (STEM). Random pieces of approximately 10 mm x 10 mm were cut from the resulting metal / ceramic bonded body, embedded in resin, and the cross section of the bonded body was polished to obtain a sample for SEM observation. A sample for STEM observation was processed using a focused ion beam (FIB) to include a region in the bonding layer where the MgO phase was likely to exist. Using the STEM, a 5 μm x 5 μm area was observed at an acceleration voltage of 200 kV and a magnification of 400,000 times. The spectrum was analyzed using electron energy loss spectroscopy (EELS). If a peak such as that shown in FIG. 4 was observed, indicating the formation of a non-layered MgO phase, this was indicated by a "◯" in Tables 1 to 3. If no peak was observed, it was determined that the MgO phase was not formed, and this was indicated by a "X" in Tables 1 to 3.

[0082] (Bonding Strength Test) A shear strength test of the bonding layer was performed on the obtained metal / ceramic bonded bodies (Samples 1 to 38). In this test, for the obtained Samples 1 to 38, the metal member was first machined into a cylindrical shape with a diameter of 3 mm and a height of 2 mm, and the bonding surface of the surrounding ceramic member was exposed to prepare a test specimen. Then, as shown in FIG. 8, with the ceramic member of the test specimen fixed, the cylindrical metal member was pressed using a displacement jig in a direction parallel to the bonding surface. The magnitude of the stress at which the bonding layer broke (shear fracture) was measured, and the shear strength of the bonding layer was calculated based on this value. The shear test position (contact height H of the displacement jig) was set at a height of 200 μm from the exposed surface of the ceramic member, and the displacement axis movement speed was 100 μm / s. The tensile strength was calculated from the obtained shear strength, and the shear strength and tensile strength values ​​are shown in Tables 1 to 3.

[0083] (Reliability Test) A thermal cycle test was performed on the obtained metal / ceramic bonded bodies (Samples 1 to 38). The test conditions included 200 cycles of a thermal cycle of -50°C for 30 minutes and 150°C for 30 minutes. Every 50 cycles, the presence or absence of cracks in the ceramic members and delamination of the metal members was determined by ultrasonic flaw detection (SAT). When no cracks in the ceramic members or delamination of the metal members were observed, this was indicated by "◯" in Tables 1 to 3. When partial cracks in the ceramic members or partial delamination of the metal members were observed, this was indicated by "△" in Tables 1 to 3. When large cracks in the ceramic members or large delamination of the metal members were observed, this was indicated by "X" in Tables 1 to 3.

[0084]

[0085]

[0086]

[0087] As shown in Tables 1 to 3, Samples 1 to 36, in which a non-lamellar MgO phase was formed in the bonding layer (first layer), had high bonding strength, and no cracking of the ceramic member or delamination of the metal member was observed even after thermal cycling tests. On the other hand, Sample 37, in which an MgO phase was not formed in the bonding layer (first layer), had slightly lower bonding strength, and partial cracking of the ceramic member and partial delamination of the metal member were observed after thermal cycling tests. Furthermore, Sample 38, in which Cu was not used as a brazing filler metal raw material, had very low bonding strength and low thermal cycling reliability. From the above, it was confirmed that forming a non-lamellar MgO phase in the bonding layer (first layer) can produce a metal / ceramic bonded body with high bonding strength and high thermal cycling reliability.

[0088] <Preferred Aspects of the Present Disclosure> Preferred aspects of the present disclosure are described below. These aspects can be combined with each other.

[0089] According to one aspect of the present disclosure, there is provided a metal / ceramic bonded body comprising: a metal member; a ceramic member bonded to the metal member; and a bonding layer formed on a bonding surface between the metal member and the ceramic member, the bonding layer containing Cu and Mg and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er, wherein a non-lamellar MgO phase containing MgO is present in the bonding layer.

[0090] Preferably, the bonding layer has: a first layer that forms an interface with the metal member and includes a solid solution phase in which Mg is solid-dissolved in Cu and a compound phase having an intermetallic compound containing Cu and Mg; and a second layer that forms an interface with the ceramic member, includes a compound of the active metal element, and is in contact with the first layer, and the non-lamellar MgO phase is present in the first layer.

[0091] Preferably, the MgO phase is present so as to surround at least one of the solid solution phase and the compound phase.

[0092] Preferably, within the region surrounded by the MgO phase, the proportion of the solid solution phase is 90% or more, or the proportion of the compound phase is 90% or more.

[0093] Preferably, the area ratio of the MgO phase in the cross section of the first layer is 5% or more and 15% or less.

[0094] Preferably, the cross section of the first layer is 500 μm ２ When the area ratio of the MgO phase in the region is measured multiple times in different observation fields, the difference between the maximum value and the minimum value of the area ratio of the MgO phase is within 5%.

[0095] Preferably, the electron energy loss spectrum of the MgO phase analyzed by a scanning transmission electron microscope has peaks in the ranges of 50 to 80 eV and 530 to 560 eV.

[0096] Preferably, the bonding layer contains 50 to 80 at % of Cu, 5 to 20 at % of Mg, and 0.1 to 10 at % of the active metal elements in total.

[0097] Preferably, when the first layer is observed in a cross section perpendicular to the bonding surface, the number of voids having a circle equivalent diameter of 8 μm or more is 10,000 μm or more. ２ There is less than one per

[0098] Preferably, when a thermal cycle of −50° C. for 30 minutes and 150° C. for 30 minutes is performed 200 times, no cracking of the ceramic member and no peeling of the metal member are observed.

[0099] According to another aspect of the present disclosure, there is provided a brazing filler metal used for joining a metal member and a ceramic member, the brazing filler metal containing 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total amount of 0.1 to 10 at %, wherein at least a portion of the Mg is contained in the form of MgO, and the Cu and Mg are contained in a state where the average particle size is 45 μm or less.

[0100] According to yet another aspect of the present disclosure, there is provided a method for producing a metal / ceramic joined body, the method comprising: arranging a metal member and a ceramic member so as to be stacked with a brazing filler metal therebetween; and heating and holding the laminate of the metal members and the ceramic members while applying pressure in the stacking direction, wherein the brazing filler metal contains 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total amount of 0.1 to 10 at %, at least a portion of the Mg is contained in the form of MgO, and the Cu and the Mg have an average particle size of 45 μm or less; and performing a hydrogen reduction treatment on the brazing filler metal.

[0101] According to yet another aspect of the present disclosure, there is provided a method for manufacturing a brazing filler metal used for joining a metal member and a ceramic member, the brazing filler metal containing 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total amount of 0.1 to 10 at %, at least a portion of the Mg is contained in the form of MgO, and the Cu and Mg are powders having an average particle size of 45 μm or less.

[0102] Preferably, the Mg contains MgO on the surface that has been subjected to a surface oxidation treatment.

[0103] REFERENCE SIGNS LIST 100 Metal / ceramic bonded body 100' Laminated body 10 Metal member 10s Bonding surface 20 Ceramic member 20s Bonding surface 30 Bonding layer 31 First layer 31A Solid solution phase 31B Compound phase 32 Second layer 33 MgO phase 34S Void (circle equivalent diameter less than 8 μm) 34L Void (circle equivalent diameter 8 μm or more) 50 Brazing filler metal

Claims

1. A metal / ceramic bonded body comprising: a metal member; a ceramic member bonded to the metal member; and a bonding layer formed on a bonding surface between the metal member and the ceramic member, the bonding layer containing Cu and Mg and further containing at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er, wherein a non-layered MgO phase containing MgO is present in the bonding layer.

2. The metal / ceramic bonded body according to claim 1, wherein the bonding layer comprises: a first layer forming an interface with the metal member and including a solid solution phase in which Mg is solid-dissolved in Cu and a compound phase having an intermetallic compound containing Cu and Mg; and a second layer forming an interface with the ceramic member, including a compound of the active metal element, and in contact with the first layer, wherein the non-lamellar MgO phase is present in the first layer.

3. A metal / ceramic joint according to claim 2, wherein the MgO phase is present so as to surround at least one of the solid solution phase and the compound phase.

4. A metal / ceramic joined body according to claim 2, wherein within the region surrounded by the MgO phase, the proportion of the solid solution phase is 90% or more, or the proportion of the compound phase is 90% or more.

5. A metal / ceramic joint according to claim 2, wherein the area ratio of the MgO phase in a cross section of the first layer is 5% or more and 15% or less.

6. Cross section of the first layer: 500 μm ２ 3. The metal / ceramic joined body according to claim 2, wherein, when an area ratio of the MgO phase in the region is measured multiple times in different observation fields, a difference between a maximum value and a minimum value of the area ratio of the MgO phase is within 5%.

7. A metal / ceramic joined body according to claim 1, wherein the MgO phase has peaks in the ranges of 50 to 80 eV and 530 to 560 eV in an electron energy loss spectrum analyzed by a scanning transmission electron microscope.

8. A metal / ceramic bonded body according to claim 1, wherein said bonding layer contains 50 to 80 at % Cu, 5 to 20 at % Mg, and a total of 0.1 to 10 at % of said active metal elements.

9. When the first layer is observed in a cross section perpendicular to the bonding surface, the number of voids having a circular equivalent diameter of 8 μm or more is 10,000 μm or more. ２ 3. The metal / ceramic bonded article according to claim 2, wherein the number of particles per one of the plurality of particles is less than one.

10. A metal / ceramic joined body according to claim 1, in which no cracking of the ceramic member and no peeling of the metal member are observed when the body is subjected to 200 thermal cycles of -50°C for 30 minutes and 150°C for 30 minutes.

11. A brazing filler metal used for joining metal members and ceramic members, comprising 50-80 at% Cu, 5-20 at% Mg, and a total of 0.1-10 at% of at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er, wherein at least a portion of the Mg is contained in the form of MgO, and the Cu and Mg are contained in a state in which the average particle size is 45 μm or less.

12. A method for manufacturing a metal / ceramic bonded body, comprising: a step of arranging a metal member and a ceramic member so as to be laminated with a brazing material interposed therebetween; and a step of heating and holding the laminate of the metal member and the ceramic member while applying pressure in the lamination direction, wherein the brazing material contains 50 to 80 at % Cu, 5 to 20 at % Mg, and at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er in a total ratio of 0.1 to 10 at %, at least a portion of the Mg is contained in the form of MgO, and the Cu and Mg are contained in a state having an average particle size of 45 μm or less, and the brazing material is subjected to a hydrogen reduction treatment.

13. A method for manufacturing a brazing filler metal used for joining metal members and ceramic members, comprising: 50 to 80 at% Cu, 5 to 20 at% Mg, and a total of 0.1 to 10 at% of at least one active metal element selected from the group consisting of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Ca, Y, Ce, La, Sm, Yb, Nd, Gd, and Er, at least a portion of the Mg being contained in the form of MgO, and the Cu and Mg are used as powders having an average particle size of 45 μm or less.

14. The method for producing a brazing filler metal according to claim 13, wherein the Mg contains MgO having been subjected to a surface oxidation treatment.

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