Copper-ceramic bond

Abstract

To provide a copper ceramic bonded body that has high bonding strength.SOLUTION: A copper ceramic bonded body 100 includes a copper material 10 made of Cu or a Cu alloy, a ceramic material 20 bonded to the copper material and made of a nitride of Si or Al, and a bonding layer 30 formed on the bonding surfaces 10s and 20s between the copper material and the ceramic material, 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. The bonding layer includes a first layer 31 constituting an interface with the copper material, and including a solid solution phase 31A formed by solidly dissolving Mg in Cu and a compound phase 31B containing the intermetallic compound between Cu and Mg, and a second layer 32 constituting the interface with the ceramic material and containing a nitride of an active metal element.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This disclosure relates to copper-ceramic joints, brazing materials, and methods for manufacturing copper-ceramic joints. [Background technology]

[0002] A bonded structure (hereinafter also referred to as a copper-ceramic bonded structure) made by joining copper and ceramic materials is sometimes used as a component material for power control devices installed in electric vehicles and hybrid vehicles. While a technique using an active metal brazing material containing silver (Ag) is known for joining copper and ceramic materials, in recent years, a technique using an active metal brazing material that does not contain Ag has been proposed to overcome issues such as Ag migration and high costs (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-140929 [Overview of the project] [Problems that the invention aims to solve]

[0004] The purpose of this disclosure is to improve the bonding strength in copper-ceramic joints. [Means for solving the problem]

[0005] According to one aspect of this disclosure, A copper material consisting of Cu or a Cu alloy, A ceramic material made of Si or Al nitride is bonded to the aforementioned copper material, A bonding layer is formed on the bonding surface between the copper material and the ceramic material, and comprises Cu and Mg, and further comprises 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, Er. The aforementioned bonding layer The first layer comprises a solid solution phase formed by solid solution of Mg in Cu and a compound phase containing an intermetallic compound of Cu and Mg, forming an interface with the copper material. A second layer comprising a nitride of the active metal element and forming an interface with the ceramic material, It has, When the first layer is observed in a cross-section perpendicular to the bonding surface, in the near-interface region adjacent to the interface with the second layer, the total cross-sectional area SA of the solid solution phase and the total cross-sectional area SB of the compound phase satisfy the relationship SA / (SA+SB)>0.6. A copper-ceramic bonded body is provided.

[0006] According to other aspects of this disclosure, A copper material consisting of Cu or a Cu alloy, A ceramic material made of Si or Al nitride is bonded to the aforementioned copper material, A bonding layer is formed on the bonding surface between the copper material and the ceramic material, and comprises Cu and Mg, and further comprises 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, Er. The aforementioned bonding layer The first layer comprises a solid solution phase formed by solid solution of Mg in Cu and a compound phase containing an intermetallic compound of Cu and Mg, forming an interface with the copper material. A second layer comprising a nitride of the active metal element and forming an interface with the ceramic material, It has, The first layer has a path made of the solid solution phase connecting the second layer and the copper material. A copper-ceramic bonded body is provided.

[0007] According to yet another aspect of this disclosure, Used for joining copper materials made of Cu or Cu alloy and ceramic materials made of Si or Al nitride. It contains 65 to 95 at% of Cu, 4.5 to 33 at% of Mg, and a total of 0.1 to 7 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, Er A brazing material is provided.

[0008] According to still another aspect of the present disclosure, A step of arranging a copper material made of Cu or a Cu alloy and a ceramic material made of a nitride of Si or Al so as to be laminated via a brazing material, A step of heating and holding the laminate of the copper material and the ceramic material while applying pressure in the lamination direction, and having As the brazing material, a material containing 65 to 95 at% of Cu, 4.5 to 33 at% of Mg, and a total of 0.1 to 7 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, Er is used A method for manufacturing a copper-ceramic bonded body is provided.

Advantages of the Invention

[0009] According to the present disclosure, it becomes possible to increase the bonding strength in a copper-ceramic bonded body.

Brief Description of the Drawings

[0010] [Figure 1] It is an enlarged partial cross-sectional view of a copper-ceramic bonded body 100 in one aspect of the present disclosure. [Figure 2] (a) is an enlarged partial cross-sectional photograph of the main part A of FIG. 1, and (b) is an enlarged partial cross-sectional photograph of the main part B of FIG. 1. [Figure 3] It is an enlarged partial cross-sectional photograph of the main part C of FIG. 1. [Figure 4] (a) is a diagram schematically showing the shear stress applied to the bonding layer 30, and (b) is a diagram schematically showing the tensile stress applied to the bonding layer 30. [Figure 5](a) shows the state where the copper material 10 and the ceramic material 20 are arranged via the brazing material 50, (b) shows the state of heating while pressing the laminate of the copper material 10 and the ceramic material 20, and (c) shows the manufactured copper-ceramic joint body 100, respectively. [Figure 6] It is a figure which shows typically the state at the time of performing a shear strength test. [Figure 7] It is a partial cross-sectional enlarged photograph of the joint layer where the large void 33L of the size has occurred.

Mode for carrying out the invention

[0011] <One aspect of the present disclosure> Hereinafter, one aspect of the present disclosure will be described with reference to the above-described drawing group. In addition, the drawings used in the following description are all schematic. The dimensions and ratios of each element shown in the drawings do not necessarily match the reality. Also, between the drawings, the dimensions and ratios of each element do not necessarily match.

[0012] (1) Configuration of copper-ceramic joint body As shown in FIG. 1, the copper-ceramic joint body 100 includes a copper material 10 and a ceramic material 20 joined to the copper material 10.

[0013] The copper material 10 is made of pure copper (hereinafter also referred to as Cu) or a copper alloy (hereinafter also referred to as Cu alloy). As the pure copper, for example, oxygen-free copper, tough pitch copper, or phosphor-deoxidized copper can be used. As the copper alloy, copper (Cu) is the main element, and for example, an alloy added with 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) can be used. Regarding the shape and dimensions of the copper material 10, there is no particular limitation, but when the copper-ceramic joint body 100 is used as a constituent material of an insulating circuit board, for example, it can be a flat plate having a thickness within the range of 0.1 mm or more and 4.0 mm or less.

[0014] The ceramic material 20 is composed of a sintered body made of silicon (Si) or aluminum (Al) nitride, that is, silicon nitride represented by the composition formula Si3N4, or aluminum nitride represented by the composition formula AlN. There are no particular limitations on the shape or dimensions of the ceramic material 20, but when the copper ceramic bond 100 is used as a component material for an insulating circuit board, it can be a flat plate having a thickness in the range of 0.2 mm to 4.0 mm. Below, as an example, the case in which the ceramic material 20 is made of silicon nitride will be described.

[0015] A bonding layer 30 is formed between the copper material 10 and the ceramic material 20, along their bonding surfaces 10s and 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), etc. Below, as an example, the case where the active metal element is Ti will be described.

[0016] As will be described later, the bonding layer 30 is formed by the reaction of a brazing material 50 (see Figure 5) containing Cu, Mg, and the above-mentioned active metal elements in predetermined proportions with the copper material 10 and the ceramic material 20, respectively. The brazing material 50 used in this embodiment does not contain Ag, and in addition to containing Mg and the above-mentioned active metal elements, it also contains Cu in the proportions described later. Preferably, the brazing material 50 used in this embodiment contains Mg in the form of an intermetallic compound with Cu. By performing bonding using such a brazing material 50, the bonding layer 30 in this embodiment exhibits the following various characteristics.

[0017] The following describes the various characteristics of the bonding layer 30.

[0018] (Feature 1) As shown in Figure 1, the bonding layer 30 has a laminated structure consisting of a first layer 31 that forms the interface with the copper material 10 and a second layer 32 that forms the interface with the ceramic material 20. The thickness of the first layer 31 is exemplified as 1 to 2000 μm, and the thickness of the second layer 32 is exemplified as 1 to 2000 nm.

[0019] Figures 2(a) and 2(b) illustrate magnified cross-sectional photographs of the first layer 31, respectively. These photographs were taken of the first layer 31 and its surroundings from different observation positions. As shown in these photographs, the first layer 31 has a solid solution phase 31A and a compound phase 31B. The solid solution phase 31A and the compound phase 31B are separated in a sea-island-like manner. For example, the compound phase 31B is dispersed in an island-like manner within the continuous sea-like solid solution phase 31A.

[0020] The solid solution phase 31A mainly consists of a solid solution in which Mg is dissolved in Cu crystals. In addition, active metal elements such as Ti that were contained in the brazing material 50, and Si and Al that were contained in the ceramic material 20 may also be dissolved in the solid solution phase 31A.

[0021] Compound phase 31B mainly consists of an intermetallic compound of Cu and Mg, i.e., a compound represented by the compositional formula MgCu2 (hereinafter also referred to as a Cu-Mg alloy). Compound phase 31B may also contain precipitated intermetallic compounds containing the active metal element mentioned above. When Ti is selected as the active metal element, the intermetallic compound containing the active metal element can be at least one compound selected from the group of compounds represented by compositional formulas such as Cu4Ti, Cu3Ti2, Cu2Ti, Cu4Ti3, CuTi, CuTi2, Ti5Si3, Ti3Si, CuTiSi, etc.

[0022] The compound phase 31B, which mainly consists of intermetallic compounds, has brittle properties compared to the solid solution phase 31A, which mainly consists of solid solutions. Depending on how it appears in the first layer 31, it can significantly reduce the bonding strength between the copper material 10 and the ceramic material 20. This is because, when a brazing material containing Mg and the aforementioned active metal elements in their individual components but without Cu is used to bond the copper material 10 and the ceramic material 20, the intermetallic compounds will appear concentrated in the near-interface region D of the first layer 31, adjacent to the second layer 32. When intermetallic compounds appear concentrated in the near-interface region D, a fragile layer structure is formed along the bonding surface in the first layer 31, which significantly reduces the bonding strength between the copper material 10 and the ceramic material 20. In this case, bonding between the copper material 10 and the ceramic material 20 may become impossible altogether.

[0023] To address these challenges, in this embodiment, when joining the copper material 10 and the ceramic material 20, a brazing material 50 containing not only Mg and active metal elements but also Cu in the proportion described later is used, thereby successfully suppressing the localized appearance of the compound phase 31B in the first layer 31, for example, the localized appearance of the compound phase 31B in the region D near the interface with the second layer 32.

[0024] Specifically, in this embodiment, when the first layer 31 is observed in a cross section perpendicular to the bonding surfaces 10s and 20s between the copper material 10 and the ceramic material 20, in the near-interface region D adjacent to the interface with the second layer 32, that is, in a predetermined region of the first layer 31 within a thickness of, for example, 10 μm from the interface with the second layer 32 toward the copper material 10, the total cross-sectional area SA of the solid solution phase 31A and the total cross-sectional area SB of the compound phase 31B satisfy the relationship SA / (SA+SB)>0.6, preferably >0.7, and more preferably >0.8.

[0025] As shown in Figures 2(a) and 2(b), in this embodiment, the compound phase 31B is dispersed with a substantially uniform frequency of appearance without local concentration in substantially the entire thickness direction and substantially the entire width direction of the first layer 31. Therefore, in this embodiment, SA and SB satisfy the above relationship not only in the near-interface region D, but also in any region within the first layer 31 excluding the near-interface region D (for example, any region closer to the copper material 10 than the near-interface region D). In other words, in this embodiment, when the first layer 31 is observed in a cross section perpendicular to the bonding surfaces 10s and 20s between the copper material 10 and the ceramic material 20, the average value SA / (SA+SB) > 0.6, preferably > 0.7, and more preferably > 0.8 is satisfied over the entire thickness direction, and it can be said that SA / (SA+SB) > 0.6, preferably > 0.7, and more preferably > 0.8 is satisfied in any local region within the first layer 31, for example, with a thickness of 10 μm.

[0026] As the total cross-sectional areas SA and SB satisfy the above-described relationship, a fragile layer structure formed by the localized generation of compound phase 31B will not appear in the first layer 31 of this embodiment, as shown in Figures 2(a) and 2(b), respectively. A path consisting of solid solution phase 31A connecting the second layer 32 and the copper material 10 is secured in the first layer 31. Since this path is mainly composed of a solid solution, it has excellent ductility and malleability, and it connects the second layer 32 and the copper material 10 continuously without being interrupted by the brittle compound phase 31B. This path constitutes a strong connecting structure between the copper material 10 and the ceramic material 20.

[0027] (Feature 2) When joining a copper material 10 and a ceramic material 20 using a brazing material containing Mg, there is a concern that voids and pinholes (hereinafter collectively referred to as voids) may occur in the first layer 31 due to the evaporation of Mg contained in the brazing material. Figure 7 shows an example of a magnified cross-sectional photograph of the joined layer containing voids 33L caused by the evaporation of Mg, etc. In Figure 7, the area is approximately 3500 μm. 2Within the field of view, the presence of void 33L with an equivalent circle diameter (the diameter of a circle with an area equal to the cross-sectional area of ​​the void) of 8 μm or larger can be confirmed. Note that the equivalent circle diameter of void 33L in the upper right of Figure 7 is approximately 9-10 μm, the equivalent circle diameter of void 33L in the upper left is 5 μm or larger, and the equivalent circle diameter of void 33L in the lower left is approximately 3-4 μm.

[0028] The presence of such large voids 33L reduces the bonding strength between the copper material 10 and the ceramic material 20. If a brazing material containing Mg and the aforementioned active metal elements in their individual components, but without Cu, is used to bond the copper material 10 and the ceramic material 20, the Mg in the brazing material will evaporate rapidly, making the formation of voids 33L with an equivalent circular diameter exceeding 8 μm in the first layer 31 unavoidable. As a result, the bonding strength between the copper material 10 and the ceramic material 20 will be significantly reduced. Furthermore, in this case, bonding between the copper material 10 and the ceramic material 20 may become impossible altogether.

[0029] To address these challenges, in this embodiment, by using a brazing material 50 that contains not only Mg and active metal elements but also Cu in the proportions described later during bonding, we have succeeded in sufficiently suppressing the appearance of large voids 33L, for example, voids 33L with an equivalent circle diameter of 8 μm or more, in the bonding layer 30.

[0030] For example, in Figure 2(a), approximately 10,000 μm 2 Within the field of view, no void 33S with an equivalent diameter of 3 μm or larger were observed, and only three void 33S with an equivalent diameter of approximately 1-2 μm were found. Furthermore, for example, in Figure 2(b), approximately 10,000 μm 2 Within the field of view, there is only one void 33S with an equivalent circle diameter of approximately 2.5 μm, and only two void 33S with an equivalent circle diameter of approximately 1 to 2 μm.

[0031] As described above, in this embodiment, when the first layer 31 is observed in a cross-section perpendicular to the bonding surfaces 10s and 20s, the bonding layer 30 has a thickness of approximately 10,000 μm. 2 It possesses an extremely excellent characteristic: no voids 33L with an equivalent circular diameter of 8 μm or larger are observed within any given field of view.

[0032] In this embodiment, when the first layer 31 is observed in a cross-section perpendicular to the bonding surfaces 10s and 20s, even if a void 33S is observed, its equivalent circular diameter is less than 8 μm, for example, less than 5 μm, preferably less than 3 μm.

[0033] Furthermore, in this embodiment, when the first layer 31 is observed in a cross-section perpendicular to the bonding surfaces 10s and 20s, voids 33S with an equivalent circle diameter of less than 8 μm, for example, voids 33S with an equivalent circle diameter of more than 2 μm but less than 8 μm, may be observed, but their number is approximately 10,000 μm. 2 Within any field of view, the number is very small, 10 or less, preferably 5 or less. In this embodiment, voids 33S with an equivalent circular diameter of 1 μm or more and 2 μm or less may also be observed, but their number is approximately 10,000 μm. 2 Within any given field of view, the number is very small, 20 or less, preferably 10 or less.

[0034] (Feature 3) Of the bonding layer 30, the second layer 32 that forms the interface with the ceramic material 20 is mainly composed of titanium nitride (TiN), which is a nitride of an active metal element (Ti in this case). When the ceramic material 20 is made of silicon nitride, the second layer 32 may also contain compounds represented by the composition formula Ti5Si3.

[0035] In this embodiment, the second layer 32 contains nitride crystals X represented by the compositional formula MgSiN2. Furthermore, as shown in Figure 3, the nitride crystals X are concentrated near the interface with the ceramic material 20 within the second layer 32.

[0036] The thickness of the region where nitride crystals X are unevenly distributed is approximately 5% to 50%, preferably 10% to 40%, of the thickness of the second layer 32, where Tx is the thickness of the second layer 32. For example, as shown in Figure 3, if the thickness Tx of the second layer 32 is approximately 250 nm, the thickness of the region where nitride crystals X are unevenly distributed is approximately 10% to 150 nm, preferably 20% to 100 nm.

[0037] The presence of nitride crystals X can be confirmed for the second layer 32 by, for example, using crystal analysis with precession electron diffraction (TEM-PED method).

[0038] Furthermore, the second layer 32 in this embodiment substantially does not contain nitride crystals Y represented by the compositional formula Mg3N2. Nitride crystals Y cannot be confirmed even by analysis using the TEM-PED method.

[0039] (Feature 4) By possessing these various features, this embodiment succeeds in significantly increasing the bonding strength between the copper material 10 and the ceramic material 20.

[0040] Specifically, the shear strength of the bonding layer 30 in this embodiment is 10 MPa or more, preferably 50 MPa or more. Furthermore, the tensile strength of the bonding layer 30 in this embodiment is 17.3 MPa or more, preferably 86.6 MPa or more.

[0041] The shear strength of the bonding layer 30, as used herein, refers to the magnitude of shear stress per unit area required to cause the bonding layer 30 to fracture (shear failure) when stress (shear stress) is applied to the bonding layer 30 in such a way that the copper material 10 and the ceramic material 20 are displaced in opposite directions along directions parallel to the bonding surfaces 10s and 20s, as shown in Figure 4(a). The tensile strength of the bonding layer 30, as shown in Figure 4(b), refers to the magnitude of tensile stress per unit area required to cause the bonding layer 30 to fracture (peel failure) when stress (tensile stress) is applied to the bonding layer 30 in such a way that the copper material 10 and the ceramic material 20 are pulled apart along directions perpendicular to the bonding surfaces 10s and 20s.

[0042] (2) Method for manufacturing copper ceramic bond Next, the manufacturing method for the copper-ceramic bonded body 100 described above will be explained using Figures 5(a) to 5(c).

[0043] First, as shown in Figure 5(a), the copper material 10 and the ceramic material 20 described above are arranged to be stacked via the brazing material 50.

[0044] As described above, the brazing material 50 can be a material containing 65-95 at% Cu, 4.5-33 at% Mg, and a total of 0.1-7 at% of the aforementioned active metal elements.

[0045] The Cu contained in the brazing material 50 acts to cause the various characteristics described above to manifest in the bonding layer 30 formed by the reaction of the brazing material 50 with the copper material 10 and the ceramic material 20. In addition, the Mg contained in the brazing material 50 acts to improve the wettability between the copper material 10 and the brazing material 50, and between the ceramic material 20 and the brazing material 50, in a balanced manner when bonding the copper material 10 and the ceramic material 20. Furthermore, the active metal elements contained in the brazing material 50 react with the ceramic material 20 to form a second layer 32, and act to increase the bonding strength between the bonding layer 30 and the ceramic material 20.

[0046] Furthermore, if the Mg content in the brazing material 50 falls below 4.5 at%, or the total active metal element content falls below 0.1 at%, and the Cu content exceeds 95 at%, the effects of Mg addition and the effects of active metal element addition described above will not be obtained.

[0047] Furthermore, if the Mg content in the brazing material 50 exceeds 33 at%, or the total active metal element content exceeds 7 at%, and the Cu content is less than 65 at%, the effects of Cu addition described above will not be obtained. For example, the SA and SB described above will no longer satisfy the relationship SA / (SA+SB)>0.6, and it will no longer be possible to secure a path in the first layer 31 consisting of the solid solution phase 31A that connects the second layer 32 and the copper material 10. Also, for example, when the first layer 31 is observed in a cross section perpendicular to the bonding surfaces 10s and 20s, voids 33L with an equivalent circle diameter of 8 μm or more will appear. Also, for example, nitride crystals X represented by the composition formula MgSiN2 will no longer appear in the second layer 32 that constitutes the interface with the ceramic material 20. As a result, the shear strength and tensile strength of the bonding layer 30 decrease significantly, with the shear strength falling below 10 MPa and the tensile strength below 17.3 MPa. Furthermore, in some cases, the bonding between the copper material 10 and the ceramic material 20 may substantially fail.

[0048] Based on these considerations, it is preferable that the amounts of Cu, Mg, and active metal elements added to the brazing material 50 be within the range of 65-95 at% for Cu, 4.5-33 at% for Mg, and a total of 0.1-7 at% for the aforementioned active metal elements.

[0049] Furthermore, Cu can be included in at least one of the following forms: elemental (Cu crystal), hydride (CuH), intermetallic compound with Mg (MgCu2), or intermetallic compound with an active metal element (e.g., Cu-Ti compound). Mg can be included in at least one of the following forms: elemental (Mg crystal), hydride (MgH2), intermetallic compound with Cu (MgCu2), or compound with an active metal element (e.g., Mg-Ti compound). If the active metal element is selected, for example, Ti, it can be included in at least one of the following forms: elemental (Ti crystal), hydride (TiH2), intermetallic compound with Cu, or intermetallic compound with Mg.

[0050] The brazing material 50 preferably contains Mg not in the form of pure Mg, but in the form of an intermetallic compound (MgCu2) with Cu. Furthermore, the brazing material 50 preferably contains Cu in the form of pure Cu and an intermetallic compound (MgCu2) with Mg. Having a Cu-MgCu2 eutectic composition in the brazing material 50 makes it possible to lower the melting point of the brazing material 50. This also allows for a reduction in the heating temperature during joining, thus avoiding excessive evaporation of Mg. As a result, the various characteristics described above can be more reliably expressed in the formed joint layer 30.

[0051] The brazing material 50 may be in powder, foil, or paste form. In the case of a powder form, the average particle size (D50) of the powder can be, for example, 5 to 50 μm. In the case of a foil form, the average film thickness can be, for example, 5 to 200 μm. In the case of a paste form, alcohols such as terpineol and butanediol or toluene can be used as the main solvent, polyvinyl alcohol, ethylcellulose, polymethacrylic acid, polyacrylic, etc. can be used as a binder, and cationic, anionic, or nonionic surfactants can be used. Plasticizers and dispersants may be further included.

[0052] As a method for placing the brazing material 50 on the planned joining surfaces 10s' and 20s' between the copper material 10 and the ceramic material 20, known methods such as screen printing, transfer, dispensing, inkjet, spray coating, sputtering, and vapor deposition can be used.

[0053] Next, as shown in Figure 5(b), the laminate 100' of copper material 10 and ceramic material 20 arranged via brazing material 50 is heated and held in a predetermined atmosphere while being pressed in the lamination direction.

[0054] Examples of conditions include the following: Atmosphere: One of the following: reduced pressure atmosphere, inert gas atmosphere, or reducing atmosphere. Oxygen concentration: 1000 ppm or less, preferably 300 ppm or less, more preferably 30 ppm or less Pressurization: 0.5kPa or higher Heating temperature: 735℃ or higher and 900℃ or lower Retention time: There are no specific restrictions, but for example, 3 minutes to 120 minutes.

[0055] During heating, it is necessary for a liquid phase to be formed in a portion of the brazing material 50, and in addition, the active metal element must be molten in that liquid phase. This state can be created by heating the material to a temperature of 735°C or higher. However, if the heating temperature is too high, the evaporation of Mg will be severe, making it difficult to form the liquid phase, or voids 33L may be generated in the formed bonding layer 30. These problems can be avoided by heating the material to a temperature of 900°C or lower. By applying pressure of 0.5kPa or higher, the adhesion between the copper material 10 and the ceramic material 20 via the brazing material 50 can be maintained, and the bonding strength between the copper material 10 and the ceramic material 20 can be increased. There is no particular upper limit to the pressure, but for example, it can be set to around 2.0kPa. The oxygen component in the atmosphere is a factor that oxidizes the active metal element and Mg, so it is desirable to keep it low, and these problems can be resolved by using the concentration range described above.

[0056] Subsequently, the heated laminate 100' is cooled. As a result, a copper-ceramic bonded body 100 having the various characteristics described above is manufactured, as shown in Figure 5(c).

[0057] (3) Effects According to this embodiment, one or more of the following effects can be obtained.

[0058] (a) By joining the copper material 10 and the ceramic material 20 using the brazing material 50 described above, which contains not only Mg and active metal elements respectively, but also Cu in the proportion described above, it becomes possible to avoid the localized generation of the compound phase 31B within the first layer 31 (for example, localized generation in the vicinity of the interface D described above). As a result, when the first layer 31 is observed in a cross section perpendicular to the joining surfaces 10s and 20s, in the vicinity of the interface D adjacent to the second layer 32, the total cross-sectional area SA of the solid solution phase 31A and the total cross-sectional area SB of the compound phase 31B satisfy the relationship SA / (SA+SB)>0.6. In addition, a path consisting of the solid solution phase 31A connecting the second layer 32 and the copper material 10 is secured within the first layer 31.

[0059] (b) By joining the copper material 10 and the ceramic material 20 using the brazing material 50 described above, it is possible to suppress the generation of voids 33L in the first layer 31. As a result, when the first layer 31 is observed in a cross section perpendicular to the joining surfaces 10s and 20s, 10,000 μm 2 Within the field of view, void 33L, which has an equivalent diameter of 8 μm or larger, is no longer observed.

[0060] (c) By joining the copper material 10 and the ceramic material 20 using the brazing material 50 described above, it becomes possible to include nitride crystals X represented by the composition formula MgSiN2 in the second layer 32. Furthermore, it is possible to make these nitride crystals X concentrated near the interface with the ceramic material 20 in the second layer 32.

[0061] (d) At least one of these various features makes it possible to dramatically increase the bonding strength between the copper material 10 and the ceramic material 20. For example, it is possible to make the shear strength of the bonding layer 30 10 MPa or more, preferably 50 MPa or more. Also, it is possible to make the tensile strength of the bonding layer 30 17.3 MPa or more, preferably 86.6 MPa or more.

[0062] <Other aspects of this disclosure> The aspects of this disclosure have been specifically described above. However, this disclosure is not limited to the aspects described above and can be modified in various ways without departing from its essence.

[0063] While examples of using silicon nitride and aluminum nitride as the material for the ceramic material 20 have been described, the invention is not limited to these, and alumina (Al2O3), silicon carbide (SiC), boron carbide (B4C), ZTA (zirconia-reinforced alumina), diamond, etc. may also be used. Even in these cases, the technology of this disclosure can be applied, and the same effects as those of the embodiments described above can be obtained.

[0064] An example has been described in which a copper material 10 made of Cu or a Cu alloy is used as the metal material to be bonded to the ceramic material 20, but the invention is not limited to these, and a nickel material made of Ni or a Ni alloy may also be used. Even in this case, the technology of this disclosure can be applied, and the same effects as in the embodiments described above can be obtained.

[0065] The copper-ceramic bond in this embodiment is not limited to applications as an insulating circuit board, but can be widely applied to various applications such as heat sinks and components of internal combustion engines and power generation machines, and in these cases as well, the same effects as in the embodiment described above can be obtained. [Examples]

[0066] (Samples 1-20) As the ceramic material, a 0.3 mm thick silicon nitride plate was used, and as the copper material, a 2.0 mm thick oxygen-free copper plate was used. As the brazing material, a paste made by mixing Cu-Mg alloy powder, Cu powder, and TiH2 powder in predetermined ratios was used. For paste formation, 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 elemental mixing ratio of Cu:Mg:Ti in the paste was as shown in Table 1. This paste was applied to the intended bonding surface of the ceramic material using screen printing, the copper material was placed directly on the applied paste film, and pressure was applied with a force of 8 kPa along the lamination direction, resulting in a bond of 1.0 × 10⁻⁶. -2 Samples 1-20 were prepared by heat treatment under the conditions shown in Table 1 in a vacuum atmosphere below Pa.

[0067] For samples 1-20, the first layer was observed in cross-sections perpendicular to the bonding surfaces at 10s and 20s. The cross-sectional area ratio expressed as SA / (SA+SB) was measured in the vicinity of the interface with the second layer, extending toward the copper material side. This observation was performed using FE-SEM and EDX. From the EDX, a phase with Cu as the main phase was identified and designated as the solid solution phase. Phases with a different contrast in the backscattered electron image from the solid solution phase were designated as compound phases. The total cross-sectional areas and their ratios were calculated using the image analysis software "Image J(registered trademark)". The analysis range was 10 μm from the interface with the second layer and 90 μm in width.

[0068] Subsequently, a shear strength test of the bonding layer was conducted. In this test, first, for the obtained samples 1 to 20 (copper-ceramics bonded bodies), the copper material was processed into a cylindrical shape with a diameter of 3 mm and a height of 2 mm, and the bonding surface of the surrounding ceramic material was exposed to prepare test pieces. Then, as shown in Fig. 6, with the ceramic material of the test piece fixed, the cylindrical copper material was pressed using a displacement jig along the direction parallel to the bonding surface, and the magnitude of the stress when the bonding layer reached fracture (shear fracture) was measured. Based on this value, the shear strength of the bonding layer was calculated. 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 material, and the moving speed of the displacement axis was set at 100 μm / s.

[0069] Also, based on the results of the shear strength test, the tensile strength of the bonding layer was calculated. The tensile strength of the bonding layer can be converted from the shear strength using the von Mises formula, and its magnitude is approximately 1.73 times the shear strength.

[0070] These results are shown in Table 1.

Table 1

[0071] As shown in Table 1, it was confirmed that in samples 1 to 20, the cross-sectional area ratio represented by SA / (SA + SB) all exceeded 0.6. Also, in all samples, the shear strength was 10 MPa or more (in these samples, 50 MPa or more), and it was confirmed that the tensile strength converted based on this was 17.3 MPa or more (in these samples, 86.6 MPa or more).

[0072] As a result of cross-sectional observation, in samples 1 to 20, in all cases, (1) a path composed of a solid solution phase connecting the second layer and the copper material was secured in the first layer, (2) approximately 10000 μm 2It was also confirmed that, within the field of view, no voids with an equivalent circle diameter of 8 μm or larger were observed in the first layer, (3) even if voids with an equivalent circle diameter of more than 2 μm but less than 8 μm were observed in the first layer within the same field of view, the number of such voids was 10 or less, preferably 5 or less, (4) even if voids with an equivalent circle diameter of 1 μm or more and 2 μm or less were observed in the first layer within the same field of view, the number of such voids was 20 or less, preferably 10 or less, (5) the second layer contained nitride crystals X represented by the compositional formula MgSiN2, and (6) the nitride crystals X were unevenly distributed in the second layer of thickness Tx, near the interface with the ceramic material, with a thickness of 5% to 50%, preferably 10% to 40%, of Tx.

[0073] (Samples 21, 22) Similar to samples 1-20, a 0.32 mm thick silicon nitride plate was used as the ceramic material, and a 2 mm thick oxygen-free copper plate was used as the copper material. The brazing material used was a paste made by mixing Mg powder and TiH2 powder in a predetermined ratio, without containing Cu powder. For paste formation, as with samples 1-20, polyethylene glycol and diethylene glycol monobutyl ether with a molecular weight of 400 or less were used as solvents, with a solvent ratio of 9 mass% in the paste. The elemental mixing ratio of Cu:Mg:Ti in the paste was as shown in Table 1. This paste was applied to the intended bonding surface of the ceramic material using screen printing, the copper material was placed directly on the applied paste film, and pressure was applied along the lamination direction with a force of 8 kPa, resulting in a bond of 1.0 × 10⁻⁶. -2 Samples 21 and 22 were prepared by heat treatment under the conditions shown in Table 1 in a vacuum atmosphere below Pa.

[0074] Then, shear strength tests were performed on samples 21 and 22 using the method described above. As shown in Table 1, the shear strength was 0.5 MPa or less and the tensile strength was 0.9 MPa or less, confirming that these samples did not have practical joint strength (essentially, they were not joined). Furthermore, since these samples did not have sufficient joint strength to withstand processing for cross-sectional microstructure observation, it was not possible to observe the joined layer in a cross-section perpendicular to the joint surface.

[0075] <Preferred aspects of this disclosure> The following are preferred embodiments of this disclosure.

[0076] According to one aspect of this disclosure, A copper material consisting of Cu or a Cu alloy, A ceramic material made of Si or Al nitride is bonded to the aforementioned copper material, A bonding layer is formed on the bonding surface between the copper material and the ceramic material, and comprises Cu and Mg, and further comprises 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, Er. The aforementioned bonding layer The first layer comprises a solid solution phase formed by solid solution of Mg in Cu and a compound phase containing an intermetallic compound of Cu and Mg, forming an interface with the copper material. A second layer comprising a nitride of the active metal element and forming an interface with the ceramic material, It has, When the first layer is observed in a cross-section perpendicular to the bonding surface, in the near-interface region adjacent to the interface with the second layer, the total cross-sectional area SA of the solid solution phase and the total cross-sectional area SB of the compound phase satisfy the following relationship: SA / (SA+SB)>0.6, preferably >0.7, and more preferably >0.8. A copper-ceramic bonded body is provided.

[0077] According to other aspects of this disclosure, A copper material consisting of Cu or a Cu alloy, A ceramic material made of Si or Al nitride is bonded to the aforementioned copper material, A bonding layer is formed on the bonding surface between the copper material and the ceramic material, and comprises Cu and Mg, and further comprises 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, Er. The aforementioned bonding layer The first layer comprises a solid solution phase formed by solid solution of Mg in Cu and a compound phase containing an intermetallic compound of Cu and Mg, forming an interface with the copper material. A second layer comprising a nitride of the active metal element and forming an interface with the ceramic material, It has, The first layer has a path made of the solid solution phase connecting the second layer and the copper material. A copper-ceramic bonded body is provided.

[0078] Preferably, When the first layer was observed in a cross-section perpendicular to the bonding surface, 10,000 μm 2 Within any given field of view, no voids with an equivalent circular diameter of 8 μm or larger are observed.

[0079] Preferably, When the first layer was observed in a cross-section perpendicular to the bonding surface, 10,000 μm 2 Within any field of view, the number of voids with an equivalent circle diameter greater than 2 μm and less than 8 μm is 10 or less, preferably 5 or less, and the number of voids with an equivalent circle diameter of 1 μm or more and 2 μm or less is 20 or less, preferably 10 or less.

[0080] Preferably, The second layer contains nitride crystal X represented by the compositional formula MgSiN2.

[0081] Preferably, The nitride crystals X are unevenly distributed in the second layer, near the interface with the ceramic material.

[0082] Preferably, The second layer substantially does not contain nitride crystal Y represented by the compositional formula Mg3N2.

[0083] Preferably, The shear strength of the bonding layer is 10 MPa or more (preferably 50 MPa or more).

[0084] Preferably, The tensile strength of the bonding layer is 17.3 MPa or higher (preferably 86.6 MPa or higher).

[0085] In other aspects of this disclosure, Used for joining copper materials made of Cu or Cu alloy and ceramic materials made of Si or Al nitride. It contains 65-95 at% Cu, 4.5-33 at% Mg, and a total of 0.1-7 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. Brazing material is provided.

[0086] Preferably, The material contains Mg (not in the form of elemental Mg) but in the form of an intermetallic compound with Cu (MgCu2 crystal).

[0087] Preferably, The material contains Cu in the form of elemental Cu and as an intermetallic compound with Mg.

[0088] According to yet another aspect of this disclosure, A copper material to be bonded to a ceramic material made of Si or Al nitride, Made of Cu or Cu alloy, A layer is formed on the surface to be joined with the aforementioned ceramic material, consisting of a brazing material containing 65-95 at% Cu, 4.5-33 at% Mg, and a total of 0.1-7 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. Brazing material-attached copper is provided.

[0089] According to yet another aspect of this disclosure, A ceramic material that is joined to a copper material made of Cu or a Cu alloy, It consists of a nitride of Si or Al, A layer is formed on the surface to be joined with the copper material, consisting of a brazing material containing 65-95 at% Cu, 4.5-33 at% Mg, and a total of 0.1-7 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. Brazing material-coated ceramic material is provided.

[0090] In other aspects of this disclosure, A step of arranging a copper material made of Cu or a Cu alloy and a ceramic material made of Si or Al nitride so as to be laminated with a brazing material in between, The process includes heating and holding the laminate of the copper material and the ceramic material while applying pressure in the lamination direction, The brazing material used contains 65-95 at% Cu, 4.5-33 at% Mg, and a total of 0.1-7 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. A method for manufacturing a copper-ceramic bond is provided. [Explanation of symbols]

[0091] 100 Copper-ceramic bond 100' laminate 10 Copper material 10s joint surface 20 Ceramic materials 20s joint surface 30 Bonding layer 31 1st layer 31A Solid solution phase 31B Compound phase 32 2nd layer 33L void (equivalent diameter of circle 8μm or larger) 33S Void (Equivalent circle diameter less than 8 μm) 50 Brazing material D: Interfacial region X Nitride crystal

Claims

1. A copper material made of Cu or a Cu alloy, A ceramic material made of Si or Al nitride is bonded to the aforementioned copper material, A bonding layer is formed on the bonding surface between the copper material and the ceramic material, comprising Cu and Mg, and further comprising 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, and not containing Ag. The aforementioned bonding layer The first layer comprises a solid solution phase formed by solid solution of Mg in Cu and a compound phase containing an intermetallic compound of Cu and Mg, forming an interface with the copper material. A second layer comprising a nitride of the active metal element and forming an interface with the ceramic material, It has, When the first layer is observed in a cross-section perpendicular to the bonding surface, in a region within a thickness of 10 μm from the interface with the second layer toward the copper material side, a phase in which the main phase is Cu is identified from EDX and this is defined as the solid solution phase, and a phase whose backscattered electron image contrast is different from that of the solid solution phase is defined as the compound phase, then the total cross-sectional area SA of the solid solution phase and the total cross-sectional area SB of the compound phase satisfy the relationship SA / (SA+SB) > 0.

6. Copper-ceramic bond.

2. When the first layer was observed in a cross-section perpendicular to the bonding surface, 10,000 μm ２ No voids with an equivalent diameter of 8 μm or larger are observed within any given field of view. The copper-ceramic bonded body according to claim 1.

3. When the first layer was observed in a cross-section perpendicular to the bonding surface, 10,000 μm ２ Within any field of view, the number of voids with an equivalent circular diameter greater than 2 μm and less than 8 μm is 10 or less. The copper-ceramic bonded body according to claim 2.

4. The second layer has the composition formula MgSiN ２ It contains nitride crystal X represented by A copper-ceramic bonded body according to any one of claims 1 to 3.

5. The nitride crystals X are concentrated in the vicinity of the interface with the ceramic material within the second layer. The copper-ceramic bonded body according to claim 4.

6. The second layer is composed of Mg ３ N ２ Substantially contains nitride crystals Y represented by A copper-ceramic bonded body according to any one of claims 1 to 5.

7. The shear strength of the aforementioned bonding layer is 10 MPa or more. A copper-ceramic bonded body according to any one of claims 1 to 6.

8. The tensile strength of the aforementioned bonding layer is 17.3 MPa or higher. A copper-ceramic bonded body according to any one of claims 1 to 7.

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