Copper / ceramic joints and insulated circuit boards

Abstract

To provide a copper / ceramic joined body that can suppress the occurrence of crack in the ceramic member even when a severe thermal cycle is applied, and has excellent thermal cycle reliability.SOLUTION: Provided is a copper / ceramic joined body 10 which is formed by joining copper members 12 and 13 made of copper or a copper alloy, and a ceramic member 11, and in which, at a joint interface between the ceramic member 11 and the copper members 12, 13, an active metal compound layer 21 is formed on the ceramic member 11 side, and, in a field of view extending for 200 μm in a width direction of the joint interface in a cross section along a direction of lamination between the ceramic member 11 and the copper members 12 and 13, and extending for 10 μm from the surface of the active metal compound layer 21 toward the copper members 12 and 13 side, an area A of the active metal-containing precipitate is 360 μm2 or less, and a ratio A / B between the area A of the active metal-containing precipitate and an area B of an Ag-enriched phase having an Ag concentration of 10 atm % or more is within a range of 0.03 or more and 0.8 or less.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a copper / ceramic bonded body formed by bonding a copper member made of copper or a copper alloy to a ceramic member, and to an insulated circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate. [Background technology]

[0002] In power modules, LED modules, and thermoelectric modules, a power semiconductor element, an LED element, and a thermoelectric element are bonded to an insulating circuit board having a circuit layer made of a conductive material formed on one side of an insulating layer. For example, power semiconductor elements for controlling large amounts of electric power used to control wind power generation, electric vehicles, hybrid vehicles, etc. generate a large amount of heat during operation. Therefore, as the substrate on which these elements are mounted, an insulated circuit board has been widely used that includes a ceramic substrate, a circuit layer formed by bonding a metal plate with excellent conductivity to one surface of the ceramic substrate, and a metal layer for heat dissipation formed by bonding a metal plate to the other surface of the ceramic substrate.

[0003] For example, Patent Document 1 proposes an insulated circuit board in which a circuit layer and a metal layer are formed by bonding copper plates to one side and the other side of a ceramic substrate. In Patent Document 1, copper plates are placed on one side and the other side of the ceramic substrate with an Ag-Cu-Ti based brazing material interposed therebetween, and the copper plates are bonded by performing a heat treatment (the so-called active metal brazing method).

[0004] Furthermore, Patent Document 2 proposes a power module substrate in which a copper plate made of copper or a copper alloy and a ceramic substrate made of AlN or Al2O3 are bonded together using a bonding material containing Ag and Ti. Furthermore, Patent Document 3 proposes a power module substrate in which a copper plate made of copper or a copper alloy and a ceramic substrate made of silicon nitride are bonded together using a bonding material containing Ag and Ti. As described above, when a copper plate and a ceramic substrate are bonded using a bonding material containing Ti, Ti, which is an active metal, reacts with the ceramic substrate, improving the wettability of the bonding material and increasing the bonding strength between the copper plate and the ceramic substrate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3211856 [Patent Document 2] Patent No. 5757359 [Patent Document 3] Japanese Patent Application Publication No. 2018-008869 Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, there has been a trend toward higher heat generation temperatures from semiconductor elements mounted on insulated circuit boards, and insulated circuit boards are being required to have higher thermal cycle reliability than ever before, so that they can withstand severe thermal cycles. Here, as mentioned above, when a copper plate and a ceramic substrate are joined using a joining material containing Ti, Ti, an active metal, diffuses to the copper plate side, and an intermetallic compound containing Cu and Ti precipitates, which hardens the area near the joining interface, causing cracks in the ceramic member when subjected to thermal cycling, which could reduce thermal cycling reliability.

[0007] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a copper / ceramic bonded body that can suppress the occurrence of cracks in the ceramic members even when subjected to severe thermal cycling and has excellent thermal cycling reliability, and an insulated circuit board made of this copper / ceramic bonded body. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the inventors conducted extensive research and found that when a ceramic member and a copper member are joined using a joining material containing Ag and an active metal, the joining layer formed at the joining interface contains an Ag-enriched phase with a high Ag concentration and active metal-containing precipitates containing the active metal, and the joining interface hardens due to precipitation hardening caused by the active metal-containing precipitates. Therefore, it was discovered that by optimizing the amount of active metal-containing precipitates present, it is possible to suppress the occurrence of cracks in the ceramic member when subjected to thermal cycles.

[0009] The present invention has been made based on the above-mentioned findings, and the copper / ceramic joined body of the present invention is a copper / ceramic joined body obtained by joining a copper member made of copper or a copper alloy to a ceramic member, wherein an active metal compound layer is formed on the ceramic member side at the joining interface between the ceramic member and the copper member, and an area A of an active metal-containing precipitate is 360 μm within a field of view of 200 μm in the width direction of the joining interface in a cross section along the lamination direction of the ceramic member and the copper member and 10 μm from the surface of the active metal compound layer toward the copper member. 2 and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is within the range of 0.03 to 0.8.

[0010] In the copper / ceramic joined body of the present invention, within a field of view of 200 μm in the width direction of the joining interface in a cross section taken along the lamination direction of the ceramic member and the copper member and 10 μm from the surface of the active metal compound layer toward the copper member, the ratio A / B of the area A of the active metal-containing precipitates to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.03 or more. This ensures that the active metal reacts sufficiently, and the ceramic member and the copper member are firmly joined. In addition, the area A of the active metal-containing precipitate is 360 μm 2and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.8 or less, so that the bonding interface can be prevented from hardening and the occurrence of cracks in the ceramic members when subjected to thermal cycles.

[0011] In the copper / ceramic bonded body of the present invention, the thickness t1 of the active metal compound layer is preferably in the range of 0.05 μm to 1.2 μm. In this case, the thickness t1 of the active metal compound layer is set within the range of 0.05 μm or more and 1.2 μm or less, so that the active metal reliably and firmly bonds the ceramic member and the copper member, and hardening of the bonding interface is further suppressed.

[0012] In the copper / ceramic joined body of the present invention, it is preferable that an Ag-Cu alloy layer is formed on the copper member side at the joining interface between the ceramic member and the copper member, and that the thickness t2 of the Ag-Cu alloy layer is in the range of 1 μm to 30 μm. In this case, Ag of the bonding material reacts sufficiently with the copper member to reliably and firmly bond the ceramic member and the copper member, and hardening of the bonding interface is further suppressed.

[0013] The insulated circuit board of the present invention is an insulated circuit board in which a copper plate made of copper or a copper alloy is bonded to the surface of a ceramic substrate, wherein an active metal compound layer is formed on the ceramic substrate side at the bonding interface between the ceramic substrate and the copper plate, and the area A of the active metal-containing precipitate is 360 μm in a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper plate side. 2 and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is within the range of 0.03 to 0.8.

[0014] In the insulating circuit board of the present invention, within a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper member, the ratio A / B of the area A of the active metal-containing precipitates to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.03 or more, so that the active metal reacts sufficiently and the ceramic substrate and the copper plate are firmly bonded together. In addition, the area A of the active metal-containing precipitate is 360 μm 2 and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.8 or less, so that the bonding interface can be prevented from hardening and the occurrence of cracks in the ceramic substrate when subjected to thermal cycles.

[0015] In the insulating circuit board of the present invention, the thickness t1 of the active metal compound layer is preferably within the range of 0.05 μm to 1.2 μm. In this case, the thickness t1 of the active metal compound layer is set within the range of 0.05 μm or more and 1.2 μm or less, so that the active metal reliably and firmly bonds the ceramic substrate and the copper plate, and further prevents the bonding interface from hardening.

[0016] In addition, in the insulating circuit board of the present invention, it is preferable that an Ag-Cu alloy layer is formed on the copper plate side at the bonding interface between the ceramic substrate and the copper plate, and that the thickness t2 of the Ag-Cu alloy layer is in the range of 1 μm or more and 30 μm or less. In this case, Ag of the bonding material reacts sufficiently with the copper plate to reliably and firmly bond the ceramic substrate and the copper plate, and hardening of the bonding interface is further suppressed. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a copper / ceramic bonded body that can suppress the occurrence of cracks in ceramic members even when subjected to severe thermal cycles and has excellent thermal cycle reliability, and an insulated circuit board made of this copper / ceramic bonded body. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a schematic explanatory diagram of a power module using an insulating circuit board according to an embodiment of the present invention. FIG. [Figure 2] 3 is an enlarged explanatory view of the bonding interface between the circuit layer and the metal layer of the insulating circuit board according to the embodiment of the present invention and the ceramic substrate. FIG. [Figure 3] 1 is a flowchart of a method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 4] 1A to 1C are schematic explanatory views of a method for manufacturing an insulating circuit board according to an embodiment of the present invention. [Figure 5] FIG. 2 is an explanatory diagram showing a method for calculating the area A of the active metal-containing precipitate and the area B of the Ag-enriched phase in an example of the present invention. [Figure 6] 1 is a photograph showing an example of the observation result of a bonding interface in this example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The copper / ceramic joined body according to this embodiment is an insulating circuit board 10 formed by joining a ceramic substrate 11 as a ceramic member made of ceramic to a copper plate 42 (circuit layer 12) and a copper plate 43 (metal layer 13) as copper members made of copper or a copper alloy. Fig. 1 shows a power module 1 including the insulating circuit board 10 according to this embodiment.

[0020] This power module 1 includes an insulating circuit board 10 having a circuit layer 12 and a metal layer 13 arranged thereon, a semiconductor element 3 bonded to one surface (the upper surface in FIG. 1) of the circuit layer 12 via a bonding layer 2, and a heat sink 5 arranged on the other side (the lower side in FIG. 1) of the metal layer 13.

[0021] The semiconductor element 3 is made of a semiconductor material such as Si, etc. The semiconductor element 3 and the circuit layer 12 are bonded together via a bonding layer 2. The bonding layer 2 is made of, for example, an Sn--Ag based, Sn--In based, or Sn--Ag--Cu based solder material.

[0022] The heat sink 5 is used to dissipate heat from the insulating circuit board 10. The heat sink 5 is made of copper or a copper alloy, and in this embodiment is made of phosphorus-deoxidized copper. The heat sink 5 is provided with a flow path for a cooling fluid to flow. In this embodiment, the heat sink 5 and the metal layer 13 are joined together by a solder layer 7 made of a solder material. The solder layer 7 is made of, for example, a Sn—Ag-based, Sn—In-based, or Sn—Ag—Cu-based solder material.

[0023] As shown in FIG. 1, the insulating circuit board 10 of this embodiment comprises a ceramic substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 1) of the ceramic substrate 11, and a metal layer 13 disposed on the other surface (the lower surface in FIG. 1) of the ceramic substrate 11.

[0024] The ceramic substrate 11 is made of ceramics such as silicon nitride (Si3N4), aluminum nitride (AlN), and alumina (Al2O3), which have excellent insulating and heat dissipating properties. In this embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN), which has particularly excellent heat dissipating properties. The thickness of the ceramic substrate 11 is set, for example, within the range of 0.2 mm to 1.5 mm, and in this embodiment, it is set to 0.635 mm.

[0025] As shown in FIG. 4, the circuit layer 12 is formed by bonding a copper plate 42 made of copper or a copper alloy to one surface (the upper surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the circuit layer 12 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 42 that will become the circuit layer 12 is set within the range of 0.1 mm to 2.0 mm, and in this embodiment is set to 0.6 mm.

[0026] As shown in FIG. 4, the metal layer 13 is formed by joining a copper plate 43 made of copper or a copper alloy to the other surface (the lower surface in FIG. 4) of the ceramic substrate 11. In this embodiment, the metal layer 13 is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate 11. The thickness of the copper plate 43 that will become the metal layer 13 is set within the range of 0.1 mm to 2.0 mm, and in this embodiment, it is set to 0.6 mm.

[0027] Here, at the bonding interface between the ceramic substrate 11 and the circuit layer 12 and metal layer 13, an active metal compound layer 21 and an Ag—Cu alloy layer 22 are formed in this order from the ceramic substrate 11 side, as shown in FIG. In this embodiment, the bonding material 45 contains Ti as an active metal, and the ceramic substrate 11 is made of aluminum nitride, so that the active metal compound layer 21 is made of titanium nitride (TiN).

[0028] In insulating circuit board 10 of this embodiment, active metal-containing precipitates are present at the bonding interface between ceramic substrate 11 and circuit layer 12 and at the bonding interface between ceramic substrate 11 and metal layer 13. Here, in a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate 11, the circuit layer 12, and the metal layer 13, and 10 μm from the surface of the active metal compound layer 21 toward the circuit layer 12 and the metal layer 13, the area A of the active metal-containing precipitate is 360 μm 2 This makes it possible to prevent the bonding interface from becoming hard, and to prevent the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycles. 2 The area A of the active metal-containing precipitate is preferably 10 μm or more. 2 It is difficult to manufacture an insulating circuit board 10 that is less than 1 / 2 mm. Furthermore, the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is set to a range of 0.03 to 0.8, which prevents the bonding interface from becoming hard and prevents the ceramic substrate 11 from cracking when subjected to thermal cycles.

[0029] Furthermore, in this embodiment, the thickness t1 of the active metal compound layer 21 formed at the bonding interface between the circuit layer 12 and the metal layer 13 is preferably within the range of 0.05 μm to 1.2 μm. In this embodiment, the thickness t2 of the Ag--Cu alloy layer 22 formed at the bonding interface between the circuit layer 12 and the metal layer 13 is preferably 1 μm or more and 30 μm or less.

[0030] A method for manufacturing the insulating circuit board 10 according to this embodiment will be described below with reference to FIGS.

[0031] (Joint material placement process S01) A copper plate 42 that will become the circuit layer 12 and a copper plate 43 that will become the metal layer 13 are prepared. Then, a bonding material 45 is applied to the bonding surfaces of the copper plate 42 that will become the circuit layer 12 and the copper plate 43 that will become the metal layer 13, and then dried. The thickness of the applied paste bonding material 45 is preferably in the range of 10 μm to 50 μm after drying. In this embodiment, the paste-like bonding material 45 is applied by screen printing.

[0032] The bonding material 45 contains Ag and active metals (Ti, Zr, Nb, Hf). In this embodiment, an Ag-Ti based brazing filler metal (Ag-Cu-Ti based brazing filler metal) is used as the bonding material 45. Note that the Ag-Ti based brazing filler metal (Ag-Cu-Ti based brazing filler metal) preferably contains, for example, Cu in the range of 0% by mass to 45% by mass, Ti (active metal) in the range of 0.5% by mass to 20% by mass, and the remainder being Ag and unavoidable impurities.

[0033] Ag powder is used as the Ag in the bonding material 45, and active metal powder is used as the active metal. The specific surface area of the Ag powder contained is 0.15 m 2 / g or more, and 0.25m 2 / g or more is more preferable, and 0.40m 2 On the other hand, the specific surface area of the Ag powder contained in the bonding material 45 is 1.40 m / g or more. 2 / g or less, and 1.00m 2 / g or less is more preferable, and 0.75m 2 It is more preferable that the saturation rate is 1 / g or less.

[0034] In this embodiment, the particle size distribution [D 90 -D 10 ] Ag and particle size distribution of the active metal powder [D 90 -D 10 ] 活性金属 The ratio [D 90 -D 10 ] Ag / [D 90 -D 10 ] 活性金属 By adjusting the above, the area A of the active metal-containing precipitate at the bonding interface and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more are adjusted.

[0035] Particle size distribution ratio [D 90 -D 10 ] Ag / [D 90 -D 10 ] 活性金属 By making the ratio of the area A and the area ratio A / B of the active metal-containing precipitates 0.01 or more, it is possible to prevent the ratio of the particle size distribution [D 90 -D 10 ] Ag / [D 90 -D 10 ] 活性金属 By making the value 1.00 or less, the area A and the area ratio A / B of the active metal-containing precipitate are prevented from becoming lower than necessary. The particle size distribution ratio [D 90 -D 10 ] Ag / [D 90 -D 10 ] 活性金属 is more preferably 0.05 or more, and even more preferably 0.15 or more. 90 -D 10 ] Ag / [D 90 -D 10 ] 活性金属 is more preferably 0.80 or less, and even more preferably 0.50 or less.

[0036] (Lamination process S02) Next, a copper plate 42 that will become the circuit layer 12 is laminated on one surface (top surface in Figure 4) of the ceramic substrate 11 via a bonding material 45, and a copper plate 43 that will become the metal layer 13 is laminated on the other surface (bottom surface in Figure 4) of the ceramic substrate 11 via a bonding material 45.

[0037] (Pressure and heating step S03) Next, the copper plate 42, the ceramic substrate 11, and the copper plate 43 are heated in a heating furnace in a vacuum atmosphere while being pressed together, and the bonding material 45 is melted. Here, the heating temperature in the pressurizing and heating step S03 is preferably within a range of 800° C. to 850° C. The total temperature integral value in the temperature increase step from 780° C. to the heating temperature and the holding step at the heating temperature is preferably within a range of 7° C. h to 120° C. h. The pressure load in the pressurizing and heating step S03 is preferably set within a range of 0.029 MPa or more and 2.94 MPa or less. Furthermore, the degree of vacuum in the pressurizing and heating step S03 is 1×10 -6 Pa or more 5×10 -2 It is preferable to set it in the range of Pa or less.

[0038] (Cooling process S04) After the pressurizing and heating step S03, the molten bonding material 45 is solidified by cooling, bonding the copper plate 42 that will become the circuit layer 12 to the ceramic substrate 11, and the ceramic substrate 11 to the copper plate 43 that will become the metal layer 13. The cooling rate in the cooling step S04 is preferably in the range of 2°C / min to 20°C / min, and is the cooling rate from the heating temperature to 780°C, which is the Ag-Cu eutectic temperature.

[0039] As described above, the insulating circuit board 10 of this embodiment is manufactured by the bonding material applying step S01, the laminating step S02, the pressurizing and heating step S03, and the cooling step S04.

[0040] (Heat sink bonding process S05) Next, the heat sink 5 is bonded to the other surface of the metal layer 13 of the insulating circuit board 10 . The insulating circuit board 10 and the heat sink 5 are stacked with a solder material interposed therebetween and placed in a heating furnace, where the insulating circuit board 10 and the heat sink 5 are solder-joined via the solder layer 7 .

[0041] (Semiconductor element bonding process S06) Next, the semiconductor element 3 is joined to one surface of the circuit layer 12 of the insulating circuit board 10 by soldering. Through the above-described steps, the power module 1 shown in FIG. 1 is manufactured.

[0042] In the insulating circuit board 10 (copper / ceramic bonded body) of this embodiment configured as described above, within a field of view of 200 μm in the width direction of the bonded interface in a cross section along the stacking direction of the ceramic substrate 11 and the circuit layer 12 and metal layer 13 and 10 μm from the surface of the active metal compound layer 21 toward the circuit layer 12 and metal layer 13, the ratio A / B of the area A of the active metal-containing precipitates to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.03 or more. Therefore, the active metal has reacted sufficiently, and the ceramic substrate 11 is firmly bonded to the circuit layer 12 and metal layer 13. In addition, the area A of the active metal-containing precipitate is 360 μm 2 and the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is 0.8 or less, so that the bonding interface can be prevented from hardening and the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycles.

[0043] Furthermore, in this embodiment, an active metal compound layer 21 is formed at the bonding interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13, and when the thickness t1 of the active metal compound layer 21 is within the range of 0.05 μm or more and 1.2 μm or less, the active metal reliably and firmly bonds the ceramic substrate 11 to the circuit layer 12 and the metal layer 13, and further prevents the bonding interface from hardening.

[0044] In order to further improve thermal cycle reliability, the thickness t1 of the active metal compound layer 21 is preferably set to 0.08 μm or less, and more preferably set to 0.15 μm or less. In order to further prevent the bonding interface from becoming harder than necessary, the thickness t1 of the active metal compound layer 21 is preferably set to 1.0 μm or less, and more preferably set to 0.6 μm or less.

[0045] Furthermore, in this embodiment, an Ag-Cu alloy layer 22 is formed at the bonding interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13, and when the thickness t2 of this Ag-Cu alloy layer 22 is within the range of 1 μm or more and 30 μm or less, the Ag of the bonding material reacts sufficiently with the circuit layer 12 and the metal layer 13 to reliably and firmly bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13, and hardening of the bonding interface is further suppressed.

[0046] In order to bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13 more firmly, the thickness t2 of the Ag-Cu alloy layer 22 is preferably 3 μm or more, and more preferably 5 μm or more. In order to further prevent the bonding interface from becoming harder than necessary, the thickness t2 of the Ag--Cu alloy layer 22 is preferably set to 25 μm or less, and more preferably set to 15 μm or less.

[0047] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of the invention. For example, in the present embodiment, a power module is described as being configured by mounting a semiconductor element on an insulating circuit board, but the present invention is not limited to this. For example, an LED module may be configured by mounting an LED element on a circuit layer of an insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on a circuit layer of an insulating circuit board.

[0048] Furthermore, in the insulating circuit board of this embodiment, the ceramic substrate has been described as being made of aluminum nitride (AlN), but this is not limitative and other ceramic substrates such as alumina (Al2O3) and silicon nitride (Si3N4) may also be used.

[0049] Furthermore, in the present embodiment, Ti has been described as an example of the active metal contained in the bonding material, but the present invention is not limited thereto, and the bonding material may contain one or more active metals selected from Ti, Zr, Hf, and Nb. These active metals may be contained as hydrides.

[0050] Furthermore, in this embodiment, the circuit layer is described as being formed by bonding a rolled sheet of oxygen-free copper to a ceramic substrate, but this is not limited thereto, and the circuit layer may be formed by bonding copper pieces punched out of a copper plate in a circuit pattern to a ceramic substrate. In this case, it is sufficient that each copper piece has the interface structure with the ceramic substrate as described above. In addition, in this embodiment, the bonding material is described as being disposed on the bonding surface of the copper plate, but this is not limited to this, and it is sufficient that the bonding material is disposed between the ceramic substrate and the copper plate, and the bonding material may also be disposed on the bonding surface of the ceramic substrate. [Example]

[0051] The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0052] First, we prepared ceramic substrates (40 mm x 40 mm) listed in Table 1. The thicknesses were 0.635 mm for AlN and Al2O3, and 0.32 mm for Si3N4. Furthermore, copper plates made of oxygen-free copper and measuring 37 mm x 37 mm and having the thickness shown in Table 1 were prepared as copper plates to be used as circuit layers and metal layers.

[0053] The bonding material containing Ag powder and active metal powder shown in Table 1 was applied to the copper plate that would become the circuit layer and metal layer so that the target thickness after drying would be the value shown in Table 1. The bonding material used was a paste material, and the amounts of Ag, Cu, and active metal were as shown in Table 1. The BET value (specific surface area) of the Ag powder was measured using an AUTOSORB-1 manufactured by QUANTACHRROME, with pretreatment of heating at 150°C for 30 minutes for vacuum degassing, followed by N2 adsorption, liquid nitrogen at 77K, and the BET multipoint method.

[0054] Particle size distribution of Ag powder [D 90 -D 10 ] Ag and particle size distribution of the active metal powder [D 90 -D 10 ] 活性金属 was measured as follows: The particle size distribution was measured by laser diffraction scattering particle size distribution measurement using Microtrac's MT3300EXII. The powder was dispersed in an aqueous solution of sodium hexametaphosphate, and the sample was subjected to US dispersion for 1 minute. The measurement was performed three times, and the average value was used. In the measurement results, the particle size at which the cumulative frequency was 10% on a volume basis was defined as D10, and the particle size at which the cumulative frequency was 90% was defined as D90. The particle size of the Ag powder (D90 - D10) was calculated as [D 90 -D 10 ] Ag , the particle size of D90-D10 in the activated metal powder is [D 90 -D 10 ] 活性金属 [D 90 -D 10 ] Ag and [D 90 -D 10 ] 活性金属 The ratio ([D 90 -D 10 ] Ag / D 90 -D 10 ] 活性金属 ) are listed in Table 1.

[0055] A copper plate to serve as a circuit layer was laminated on one surface of the ceramic substrate, and a copper plate to serve as a metal layer was laminated on the other surface of the ceramic substrate.

[0056] The laminate was heated while being pressurized in the lamination direction to generate an Ag-Cu liquid phase. The pressure load was 0.294 MPa, and the temperature integral values were as shown in Table 2. The heated laminate was then cooled to bond the copper plate that would become the circuit layer, the ceramic substrate, and the metal plate that would become the metal layer, thereby obtaining an insulated circuit board (copper / ceramic bonded body).

[0057] The obtained insulating circuit board (copper / ceramic bonded body) was evaluated for the area A of the active metal-containing precipitate, the area B of the Ag-enriched phase, the thickness t1 of the active metal compound layer, the thickness t2 of the Ag-Cu alloy layer, and thermal cycle reliability as follows.

[0058] (Area of active metal-containing precipitate A) The cross sections of the bonding interfaces between the circuit layer and the metal layer and the ceramic substrate were observed using an EPMA device, and element maps (50 μm wide x 30 μm high) of the active metal were obtained from five fields of view for each, for a total of 10 fields of view. As shown in Figure 5, in the region from the active metal compound layer to 10 µm toward the surface of the circuit layer (metal layer), when Ag + Cu + active metal = 100 atomic %, the region where the active metal concentration is in the range of 30 atomic % to 70 atomic % was defined as the active metal-containing precipitate, and the area A of the active metal-containing precipitate was calculated. The average value of these 10 fields of view is shown in Table 2. If the active metal compound layer is undulating, the region is set along the undulations.

[0059] (Area of Ag-enriched phase B) As with the area A of the active metal-containing precipitate, the cross section of the bonding interface between the circuit layer and the metal layer and the ceramic substrate was observed using an EPMA device, and elemental maps (50 μm wide x 30 μm high) for Ag were obtained from five fields of view each, for a total of 10 fields of view. As shown in Figure 5, in the region from the active metal compound layer to 10 μm toward the surface of the circuit layer (metal layer), when Ag + Cu + active metal = 100 atomic %, the region where the Ag concentration was 10 atomic % or more was defined as the Ag-enriched phase, and the area B of the Ag-enriched phase was calculated. The average values of these 10 fields of view are shown in Table 2. Furthermore, the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase was calculated and shown in Table 2. An example of the observation results of the bonded interface is shown in Figure 6. Active metal-containing precipitates and an Ag-enriched phase are observed at the bonded interface.

[0060] (Active metal compound layer) The cross sections of the bonding interface between the circuit layer and ceramic substrate, and the bonding interface between the ceramic substrate and metal layer were measured at a magnification of 30,000x using a scanning electron microscope (Carl Zeiss NTS ULTRA55, accelerating voltage 1.8 kV), and elemental mapping of N, O, and active metal elements was obtained using energy dispersive X-ray analysis. The presence of an active metal compound layer was determined when an active metal element and N or O were present in the same region. Observations were made in five fields of view for each sample, and the area in which the active metal element and N or O were present in the same region was divided by the measured width, and the average value was calculated and recorded in Table 2 as the "thickness of the active metal compound layer."

[0061] (Ag-Cu alloy layer) The cross-sections of the bonding interface between the circuit layer and the ceramic substrate, and between the ceramic substrate and the metal layer were subjected to elemental mapping of Ag, Cu, and active metals using an EPMA device. Elemental mapping was performed in five fields of view for each. When Ag + Cu + active metal = 100% by mass, the area where the Ag concentration was 15% by mass or more was defined as the Ag-Cu alloy layer. The area was calculated and divided by the width of the measurement area (200 μm) to obtain the value (area / width of measurement area (200 μm)). The average of these values is shown in Table 2 as the thickness of the Ag-Cu alloy layer.

[0062] (thermal cycle reliability) The above-mentioned insulating circuit boards were subjected to the following thermal cycles depending on the material of the ceramic substrate, and the presence or absence of ceramic cracks was determined by SAT testing. The evaluation results are shown in Table 2. For AlN and Al2O3: -40℃ x 5 min ←→ 150℃ x 5 min, SAT inspection every 50 cycles up to 500 cycles. For Si3N4: -40℃ x 5 min ←→ 150℃ x 5 min, SAT inspection every 200 cycles up to 2000 cycles.

[0063] [Table 1]

[0064] [Table 2]

[0065] First, invention examples 1-3 and comparative example 1, which use AlN as the ceramic substrate, will be compared. In Comparative Example 1, in a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper plate, the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more was 0.007, and the number of times cracks occurred in a thermal cycle test was 50.

[0066] In contrast, in Inventive Example 1-3, the area A of the active metal-containing precipitate was 360 μm 2 The ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is set to be within the range of 0.03 to 0.8, and the number of crack occurrences in a thermal cycling test was 350 to 500, demonstrating excellent thermal cycling reliability.

[0067] Next, invention examples 4-6, which used Si3N4 as the ceramic substrate, will be compared with comparative examples 2 and 3. In Comparative Example 2, the area A of the active metal-containing precipitate was 395.7 μm in a field of view of 200 μm in the width direction of the bonding interface in the cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer to the copper plate side. 2 The ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase with an Ag concentration of 10 atomic % or more was 1.256, and the number of crack occurrences in a thermal cycle test was 1,200. In Comparative Example 3, in a field of view of 200 μm in the width direction of the bonding interface in a cross section along the stacking direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper plate, the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more was 1.305, and the number of times cracks occurred in a thermal cycle test was 1,200.

[0068] In contrast, in Inventive Example 4-6, the area A of the active metal-containing precipitate was 360 μm 2 The ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is set to be within the range of 0.03 to 0.8, and the number of crack occurrences in a thermal cycling test exceeded 1800 to 2000, demonstrating excellent thermal cycling reliability.

[0069] Next, invention examples 7 and 8, which used Al2O3 as the ceramic substrate, will be compared with comparative example 4. In Comparative Example 4, in a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper plate, the ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more was 0.018, and the number of cracks that occurred in the thermal cycle test was 50.

[0070] In contrast, in Examples 7 and 8 of the present invention, the area A of the reactive metal-containing precipitate was 360 μm 2 The ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more is set to be within the range of 0.03 to 0.8, and the number of crack occurrences in a thermal cycling test exceeded 300 to 450, demonstrating excellent thermal cycling reliability.

[0071] From the results of the above confirmatory experiments, it was confirmed that the examples of the present invention can suppress the occurrence of cracks in the ceramic substrate even when subjected to severe thermal cycles, and can provide an insulated circuit substrate (copper / ceramic bonded body) with excellent thermal cycle reliability. [Explanation of symbols]

[0072] 10 Insulated circuit board (copper / ceramic bonded body) 11 Ceramic substrate (ceramic component) 12 Circuit layer (copper material) 13 Metal layer (copper material) 21 Active metal compound layer 22 Ag-Cu alloy layer

Claims

1. A copper / ceramic bonded body obtained by bonding a copper member made of copper or a copper alloy to a ceramic member, an active metal compound layer is formed on the ceramic member side at the bonding interface between the ceramic member and the copper member, In a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic member and the copper member and 10 μm from the surface of the active metal compound layer toward the copper member, The area A of the active metal-containing precipitate is 360 μm ２ The following is stated: a ratio A / B of an area A of the active metal-containing precipitate to an area B of an Ag-enriched phase having an Ag concentration of 10 atomic % or more, which is in the range of 0.03 to 0.

8.

2. 2. The copper / ceramic bonded body according to claim 1, wherein the thickness t1 of the active metal compound layer is in the range of 0.05 μm to 1.2 μm.

3. an Ag—Cu alloy layer is formed on the copper member side at the bonding interface between the ceramic member and the copper member; 3. The copper / ceramic joined body according to claim 1, wherein the thickness t2 of the Ag--Cu alloy layer is in the range of 1 μm to 30 μm.

4. An insulating circuit board having a copper plate made of copper or a copper alloy bonded to the surface of a ceramic substrate, an active metal compound layer is formed on the ceramic substrate side at the bonding interface between the ceramic substrate and the copper plate; In a field of view of 200 μm in the width direction of the bonding interface in a cross section along the lamination direction of the ceramic substrate and the copper plate and 10 μm from the surface of the active metal compound layer toward the copper plate, The area A of the active metal-containing precipitate is 360 μm ２ The following is stated: an area ratio A / B of the area A of the active metal-containing precipitate to the area B of the Ag-enriched phase having an Ag concentration of 10 atomic % or more, which is in the range of 0.03 to 0.

8.

5. 5. The insulating circuit board according to claim 4, wherein the thickness t1 of the active metal compound layer is in the range of 0.05 μm to 1.2 μm.

6. an Ag—Cu alloy layer is formed on the copper plate side at the bonding interface between the ceramic substrate and the copper plate; 6. The insulating circuit board according to claim 4, wherein the thickness t2 of the Ag--Cu alloy layer is within the range of 1 μm to 30 μm.

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