Copper / ceramic joint and insulated circuit board

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 an active metal diffusion region 23 is formed on the ceramic member 11 side of the copper members 12, 13, a maximum reaching distance LA of an active metal diffusion region 23A in the peripheral region A from an active metal compound layer 21A and a maximum reaching distance LB of an active metal diffusion region 23B in the central region B from an active metal compound layer 21B are within the range of 20 μm or more and 80 μm or less, and a difference between the maximum reaching distance LA and the maximum reaching distance LB is 10 μm 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 insulating circuit board formed by bonding a copper plate made of copper or a copper alloy to a surface of a ceramic substrate. [Background technology]

[0002] In power modules, LED modules and thermoelectric modules, power semiconductor elements, LED elements and thermoelectric elements are bonded to an insulating circuit board having an insulating layer on one side of which a circuit layer made of a conductive material is formed. For example, power semiconductor elements for controlling large amounts of power used to control wind power generation, electric vehicles, hybrid vehicles, and the like generate a large amount of heat during operation. Therefore, as a substrate for mounting these elements, an insulated circuit board has been widely used which includes a ceramic substrate, a circuit layer formed by bonding a metal plate with excellent electrical 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 insulating circuit board in which a circuit layer and a metal layer are formed by bonding copper plates to one and the other sides of a ceramic substrate. In Patent Document 1, copper plates are arranged on one and the other sides of a ceramic substrate with an Ag-Cu-Ti brazing material interposed therebetween, and the copper plates are bonded by performing a heat treatment (so-called active metal brazing method).

[0004] Moreover, 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 thereby improving 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] JP 2018-008869 A Summary of the Invention [Problem to be solved by the invention]

[0006] Recently, the heat generation temperature of semiconductor elements mounted on insulating circuit boards has tended to increase, and insulating circuit boards are 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, which is an active metal, diffuses to the copper plate side and an intermetallic compound containing Cu and Ti precipitates, which hardens the vicinity of the joining interface, causing cracks in the ceramic member when subjected to thermal cycles, which may reduce thermal cycle reliability.

[0007] The present invention has been made in view of the above-mentioned circumstances, and has an object to provide a copper / ceramic bonded body that is capable of suppressing the occurrence of cracks in the 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. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present inventors conducted extensive research and found that when a ceramic member and a copper member are joined using a joining material containing an active metal, the liquid phase generated during joining is expelled from the center of the copper member to the peripheral portion, and the active metal is relatively abundant in the peripheral portion of the copper member, so that the peripheral portion of the copper member tends to be harder than the central portion at the joining interface between the ceramic member and the copper member.Then, the inventors found that stress is concentrated in the hard peripheral portion of the copper member at the joining interface during thermal cycle loading, making the ceramic member more likely to crack.

[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 a joining interface between the ceramic member and the copper member, and an active metal diffusion region is formed on the copper member side of the ceramic member by diffusing active metals (Ti, Zr, Nb, Hf) from the ceramic member side to the copper member side, in which the concentration of the active metal in the copper member is 0.5 mass % or more, and Maximum reach L A and from the active metal compound layer of the active metal diffusion region in the central region of the copper member. Maximum reach L B is in the range of 20 μm to 80 μm, and the maximum reach L of the active metal diffusion region in the peripheral region of the copper member A and the maximum reach L of the active metal diffusion region in the central region of the copper member. B The difference between the above and the above is 10 μm or less.

[0010] According to the copper / ceramic bonded body of the present invention, the maximum reach L of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper member is Aand the maximum reach L of the active metal diffusion region from the active metal compound layer in the central region of the copper member. B Since the thickness is within the range of 20 μm or more and 80 μm or less, the ceramic member and the copper member are firmly bonded together by the active metal, and hardening of the bonded interface is suppressed. The maximum reach L of the active metal diffusion region in the peripheral region of the copper member A and the maximum reach L of the active metal diffusion region in the central region of the copper member. B Since the difference between the above is 10 μm or less, the peripheral region of the copper member is prevented from becoming relatively hard at the joining interface, and the occurrence of cracks in the ceramic member when subjected to thermal cycle loading can be suppressed, resulting in excellent thermal cycle reliability.

[0011] In the copper / ceramic bonded body of the present invention, the thickness t1 of the active metal compound layer formed in the peripheral region of the copper member A and a thickness t1 of the active metal compound layer formed in the central region of the copper member. B is within the range of 0.05 μm to 1.2 μm, and the thickness ratio t1 A / t1 B It is preferable that the ratio is within the range of 0.7 to 1.4. In this case, the thickness t1 of the active metal compound layer formed in the peripheral region of the copper member A and a thickness t1 of the active metal compound layer formed in the central region of the copper member. B Since the thickness is within the range of 0.05 μm or more and 1.2 μm or less, the ceramic member and the copper member are reliably and firmly bonded to each other by the active metal, and hardening of the bonded interface is further suppressed. And the thickness ratio t1 A / t1 B Since the hardness of the bonding interface between the peripheral region and the central region of the copper member does not differ significantly, the occurrence of cracks in the ceramic member when subjected to thermal cycles can be further suppressed.

[0012] In the copper / ceramic bonded body of the present invention, an Ag-Cu alloy layer is formed on the copper member side at the bonding interface between the ceramic member and the copper member, and the thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper member is A and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper member. B is within the range of 1 μm to 30 μm, and the thickness ratio t2 A / t2 B It is preferable that the ratio is within the range of 0.7 to 1.4. In this case, the thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper member A and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper member. B Since the thickness is within the range of 1 μm or more and 30 μm or less, the 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. And the thickness ratio t2 A / t2 B Since the hardness of the bonding interface between the peripheral region and the central region of the copper member does not differ significantly, the occurrence of cracks in the ceramic member when subjected to thermal cycles can be 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 a surface of a ceramic substrate, and 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 an active metal diffusion region is formed on the ceramic substrate side of the copper plate in which an active metal (Ti, Zr, Nb, Hf) diffuses from the ceramic substrate side to the copper plate side, and the concentration of the active metal in the copper plate is 0.5 mass % or more, and the active metal diffusion region in the peripheral region of the copper plate is formed by diffusing active metals (Ti, Zr, Nb, Hf) from the ceramic substrate side to the copper plate side. Maximum reach L A and from the active metal compound layer of the active metal diffusion region in the central region of the copper plate. Maximum reach LB is in the range of 20 μm to 80 μm, and the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion region in the central region of the copper plate. B The difference between the above and the above is 10 μm or less.

[0014] According to the insulating circuit board of the present invention, the maximum reach L of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate is A and the maximum reach L of the active metal diffusion region from the active metal compound layer in the central region of the copper plate. B Since the thickness is within the range of 20 μm or more and 80 μm or less, the ceramic substrate and the copper plate are firmly bonded by the active metal, and the bonded interface is prevented from becoming hard. The maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion region in the central region of the copper plate. B Since the difference between the hardness and the hardness is set to 10 μm or less, the peripheral region of the copper plate at the bonding interface can be prevented from becoming relatively hard, the occurrence of cracks in the ceramic substrate when subjected to thermal cycle loading can be suppressed, and the ceramic substrate has excellent thermal cycle reliability.

[0015] In the insulating circuit board of the present invention, the thickness t1 of the active metal compound layer formed in the peripheral region of the copper plate A and a thickness t1 of the active metal compound layer formed in the central region of the copper plate. B is within the range of 0.05 μm to 1.2 μm, and the thickness ratio t1 A / t1 B It is preferable that the ratio is within the range of 0.7 to 1.4. In this case, the thickness t1 of the active metal compound layer formed in the peripheral region of the copper plate A and a thickness t1 of the active metal compound layer formed in the central region of the copper plate. BSince the thickness is within the range of 0.05 μm or more and 1.2 μm or less, the ceramic substrate and the copper plate are reliably and firmly bonded to each other by the active metal, and hardening of the bonded interface is further suppressed. And the thickness ratio t1 A / t1 B Since the range of is 0.7 or more and 1.4 or less, there is no significant difference in hardness of the bonding interface between the peripheral region and the central region of the copper plate, and it is possible to further suppress the occurrence of cracks in the ceramic substrate when subjected to thermal cycle loading.

[0016] In the insulating circuit board of the present invention, 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 the thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper plate is A and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper plate. B is within the range of 1 μm to 30 μm, and the thickness ratio t2 A / t2 B It is preferable that the ratio is within the range of 0.7 to 1.4. In this case, the thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper plate A and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper plate. B Since the thickness is within the range of 1 μm or more and 30 μm or less, the 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. And the thickness ratio t2 A / t2 B Since the hardness of the bonding interface between the peripheral region and the central region of the copper plate does not differ significantly, the occurrence of cracks in the ceramic substrate when subjected to thermal cycles can be further suppressed. Effect 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 description of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic explanatory diagram of a power module using an insulating circuit board according to an embodiment of the present invention. [Diagram 2] 1A is an explanatory view of the peripheral region and the central region of the circuit layer and the metal layer of the insulating circuit board according to an embodiment of the present invention, and FIG. [Diagram 3] FIG. 2 is a flow diagram 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 diagrams of a method for producing an insulating circuit board according to an embodiment of the present invention. [Diagram 5] 5A to 5C are explanatory diagrams of a bonding material providing step in the method for producing an insulating circuit board according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The copper / ceramic bonded body according to this embodiment is an insulating circuit board 10 formed by bonding a ceramic substrate 11 as a ceramic member made of ceramics 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 of the circuit layer 12 (the upper surface in FIG. 1) via a bonding layer 2, and a heat sink 5 arranged on the other side of the metal layer 13 (the lower side in FIG. 1).

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

[0022] The heat sink 5 is for dissipating 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 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 includes 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) that 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 within a range of 0.2 mm to 1.5 mm, for example, and is set to 0.635 mm in this embodiment.

[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 becomes the circuit layer 12 is set within a range of 0.1 mm to 2.0 mm, and is set to 0.6 mm in this embodiment.

[0026] As shown in FIG. 4, the metal layer 13 is formed by bonding 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 becomes the metal layer 13 is set within a range of 0.1 mm to 2.0 mm, and is set to 0.6 mm in this embodiment.

[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 addition, in the circuit layer 12 and the metal layer 13, an active metal diffusion region 23 is formed on the bonding interface side with the ceramic substrate 11, in which the concentration of the active metal in the circuit layer 12 and the metal layer 13 is 0.5 mass % or more, as a result of the active metal (Ti in this embodiment) diffusing toward the circuit layer 12 side and the metal layer 13 side.

[0028] In insulating circuit board 10 of this embodiment, as shown in FIG. 2, the interface structure in peripheral region A and central region B of circuit layer 12 and metal layer 13 is specified as follows. In this embodiment, the peripheral region A of the circuit layer 12 and the metal layer 13 is a region extending 20 μm inward from the widthwise end of the circuit layer 12 and the metal layer 13 in a cross section along the stacking direction of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11, as shown in FIG. 2(a). In addition, the central region B of the circuit layer 12 and the metal layer 13 is a region of 200 μm in the width direction including the width center of the circuit layer 12 and the metal layer 13 in a cross section along the stacking direction of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11, as shown in Figure 2(a).

[0029] As shown in FIG. 2(b), in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13, the maximum reach L A is set to be within the range of 20 μm or more and 80 μm or less. As shown in FIG. 2(c), in the central region B of the bonding interface between the circuit layer 12 and the metal layer 13, the maximum reach L B is set to be within the range of 20 μm or more and 80 μm or less.

[0030] In this embodiment, the maximum reach L of the active metal diffusion region 23A in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13 is A and the maximum reach L of the active metal diffusion region 23B in the central region B of the bonding interface between the circuit layer 12 and the metal layer 13. B The difference between these is set to be 10 μm or less.

[0031] In this embodiment, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13 is A and a thickness t1 of the active metal compound layer 21B formed in the central region B of the bonding interface between the circuit layer 12 and the metal layer 13. B is within the range of 0.05 μm to 1.2 μm, and the thickness ratio t1 A / t1 BIt is preferable that the ratio is within the range of 0.7 to 1.4. Here, the active metal compound layer 21 (21A, 21B) is a layer made of a compound of the active metal (Ti, Zr, Nb, Hf) used in the bonding material 45. More specifically, when the ceramic substrate is made of silicon nitride (Si3N4) or aluminum nitride (AlN), the layer is made of the nitride of these active metals, and when the ceramic substrate is made of alumina (Al2O3), the layer is made of the oxide of these active metals. The active metal compound layer 21 (21A, 21B) is formed by an aggregation of particles of the active metal compound. The average particle size of these particles is 10 nm or more and 100 nm or less. In this embodiment, since the bonding material 45 contains Ti as an active metal and the ceramic substrate 11 is made of aluminum nitride, the active metal compound layer 21 (21A, 21B) is made of titanium nitride (TiN). That is, the active metal compound layer 21 (21A, 21B) is formed by an aggregation of titanium nitride (TiN) particles having an average particle size of 10 nm or more and 100 nm or less.

[0032] In this embodiment, the thickness t2 of the Ag-Cu alloy layer 22A formed in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13 is A and a thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the bonding interface between the circuit layer 12 and the metal layer 13. B Ratio to t2 A / t2 B It is preferable that the ratio is within the range of 0.7 to 1.4. The thickness of the Ag--Cu alloy layer 22 (22A, 22B) is preferably 1 μm or more and 30 μm or less.

[0033] A method for manufacturing the insulating circuit board 10 according to this embodiment will be described below with reference to FIGS.

[0034] (Joint material placement process S01) A copper plate 42 which will become the circuit layer 12 and a copper plate 43 which 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 within a range of 10 μm to 50 μm after drying. In this embodiment, the paste-like bonding material 45 is applied by screen printing.

[0035] The bonding material 45 contains Ag and active metals (Ti, Zr, Nb, Hf). In this embodiment, an Ag-Ti brazing material (Ag-Cu-Ti brazing material) is used as the bonding material 45. It is preferable to use the Ag-Ti brazing material (Ag-Cu-Ti brazing material) having a composition that contains, for example, Cu in the range of 0 mass% to 45 mass% and Ti as an active metal in the range of 0.5 mass% to 20 mass%, with the remainder being Ag and unavoidable impurities.

[0036] The specific surface area of ​​the Ag powder contained in the bonding material 45 is 0.15 m 2 / g or more, and 0.25m 2 / g or more, and more preferably 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 2 / g or less, and 1.00m 2 / g or less, and more preferably 0.75m 2 It is more preferable that the molecular weight is 1 / g or less. The particle size of the Ag powder contained in the paste-like bonding material 45 is preferably within a range of D10 of 0.7 μm to 3.5 μm and D100 of 4.5 μm to 23 μm.

[0037] Here, in the pressurizing and heating step S03 described later, by applying pressure in the stacking direction, the generated liquid phase is expelled from the center of the copper plates 42, 43 to the peripheral portion, and a relatively large amount of active metal components is present on the peripheral portion of the copper plates 42, 43. Therefore, in this embodiment, as shown in Figure 5, the bonding material 45 is applied so that the application thickness of the bonding material 45A at the peripheral portions of the copper plate 42 that becomes the circuit layer 12 and the copper plate 43 that becomes the metal layer 13 is thinner than the application thickness of the bonding material 45B at the central portions of the copper plate 42 that becomes the circuit layer 12 and the copper plate 43 that becomes the metal layer 13. In addition, it is preferable that the difference between the coating thickness of bonding material 45A at the peripheral portions of copper plate 42 which becomes circuit layer 12 and copper plate 43 which becomes metal layer 13, and the coating thickness of bonding material 45B at the central portions, is within the range of 5 μm or more and 15 μm or less.

[0038] (Lamination process S02) Next, a copper plate 42 which will become the circuit layer 12 is laminated on one surface (the upper surface in Figure 4) of the ceramic substrate 11 via an adhesive material 45, and a copper plate 43 which will become the metal layer 13 is laminated on the other surface (the lower surface in Figure 4) of the ceramic substrate 11 via an adhesive material 45.

[0039] (Pressure and heating process 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 pressurized, so that the bonding material 45 melts. 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 increasing 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 80° 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 the range to 0.1 Pa or less.

[0040] (Cooling process S04) Then, after the pressurizing and heating step S03, cooling is performed to solidify the molten bonding material 45, thereby 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 within a range of 2° C. / min to 20° C. / min from the heating temperature to 780° C., which is the Ag-Cu eutectic temperature.

[0041] As described above, the insulating circuit board 10 of this embodiment is manufactured by the bonding material providing step S01, the laminating step S02, the pressurizing and heating step S03, and the cooling step S04.

[0042] (Heat sink bonding process S05) Next, heat sink 5 is bonded to the other surface side of metal layer 13 of insulating circuit board 10. Insulated circuit board 10 and heat sink 5 are laminated with a solder material interposed therebetween and loaded into a heating furnace, where insulating circuit board 10 and heat sink 5 are solder-joined via solder layer 7 .

[0043] (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.

[0044] According to the insulating circuit board 10 (copper / ceramic bonded body) of the present embodiment configured as described above, the maximum reachable distance L of the active metal diffusion region 23A in the peripheral region A of the circuit layer 12 and the metal layer 13 from the active metal compound layer 21A is A , and the maximum reach L of the active metal diffusion region 23B in the central region B of the circuit layer 12 and the metal layer 13 from the active metal compound layer 21B. B Since the thickness is within the range of 20 μm or more and 80 μm or less, the ceramic substrate 11 is firmly bonded to the circuit layer 12 and the metal layer 13 by the active metal, and the bonded interface is prevented from becoming hard.

[0045] In order to bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13 more firmly, the maximum reach L of the active metal diffusion region 23 (23A, 23B) from the active metal compound layer 21 (21A, 21B) is set to 1 / 2 mm. A ,L B is preferably 25 μm or more, and more preferably 35 μm or more. In order to further prevent the bonding interface from becoming unnecessarily hard, the maximum reach L of the active metal diffusion region 23 (23A, 23B) from the active metal compound layer 21 (21A, 21B) is A ,L B is preferably 75 μm or less, and more preferably 65 μm or less.

[0046] The maximum reach L of the active metal diffusion region 23A in the peripheral region A of the circuit layer 12 and the metal layer 13 is A and the maximum reach L of the active metal diffusion region 23B in the central region B of the circuit layer 12 and the metal layer 13. B Since the difference between the above is 10 μm or less, the peripheral region A of the circuit layer 12 and the metal layer 13 at the bonding interface can be prevented from becoming relatively hard, the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycle loading can be suppressed, and the ceramic substrate 11 has excellent thermal cycle reliability. In order to further improve the thermal cycle reliability, the maximum reach L of the active metal diffusion region 23A in the peripheral region A of the circuit layer 12 and the metal layer 13 is A and the maximum reach L of the active metal diffusion region 23B in the central region B of the circuit layer 12 and the metal layer 13. B The difference between these is preferably 8 μm or less, and more preferably 6 μm or less.

[0047] In this embodiment, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is A、 and the thickness t1 of the active metal compound layer 21B formed in the central region B of the circuit layer 12 and the metal layer 13. BWhen the thickness 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 hardening of the bonding interface is further suppressed.

[0048] In order to bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13 more firmly, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is set to 0.05 mm. A and the thickness t1 of the active metal compound layer 21B formed in the central region B of the circuit layer 12 and the metal layer 13. B is preferably 0.08 μm or more, and more preferably 0.15 μm or more. In order to further prevent the bonding interface from becoming unnecessarily hard, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is set to 0.5 mm. A and the thickness t1 of the active metal compound layer 21B formed in the central region B of the circuit layer 12 and the metal layer 13. B is preferably 1.0 μm or less, and more preferably 0.6 μm or less.

[0049] Furthermore, in this embodiment, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is A and the thickness t1 of the active metal compound layer 21B formed in the central region B of the circuit layer 12 and the metal layer 13. B Ratio of t1 A / t1 B When the ratio is within the range of 0.7 or more and 1.4 or less, there is no significant difference in hardness of the bonding interface between the peripheral region A and the central region B of the circuit layer 12 and the metal layer 13, and it is possible to further suppress the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycle loading.

[0050] In order to further suppress the occurrence of cracks in the ceramic substrate 11 during thermal cycle loading, the thickness t1 of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is set to 0.5 μm.A and the thickness t1 of the active metal compound layer 21B formed in the central region B of the circuit layer 12 and the metal layer 13. B Ratio of t1 A / t1 B is more preferably within the range of 0.8 or more and 1.2 or less, and even more preferably within the range of 0.9 or more and 1.1 or less.

[0051] In this embodiment, the thickness t2 of the Ag-Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is A , and the thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the circuit layer 12 and the metal layer 13. B In the case where the thickness is within the range of 1 μm or more and 30 μm or less, Ag of the bonding material 45 described later reacts sufficiently with the circuit layer 12 and the metal layer 13, so that the ceramic substrate 11, the circuit layer 12 and the metal layer 13 are reliably and firmly bonded to each other, and hardening of the bonding interface is further suppressed.

[0052] 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 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is set to 0.05 mm. A , and the thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the circuit layer 12 and the metal layer 13. B is preferably 3 μm or more, and more preferably 5 μm or more. In order to further prevent the bonding interface from becoming unnecessarily hard, the thickness t2 of the Ag-Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is set to 0.05 mm. A , and the thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the circuit layer 12 and the metal layer 13. B is preferably 25 μm or less, and more preferably 15 μm or less.

[0053] Furthermore, in this embodiment, the thickness t2 of the Ag-Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 is Aand the thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the circuit layer 12 and the metal layer 13. B Ratio to t2 A / t2 B is within the range of 0.7 or more and 1.4 or less, there is no significant difference in hardness of the bonding interface between the peripheral region A and the central region B of the circuit layer 12 and the metal layer 13, and the occurrence of cracks in the ceramic substrate when subjected to thermal cycle loading can be further suppressed.

[0054] In order to further suppress the occurrence of cracks in the ceramic substrate 11 during thermal cycle loading, the thickness t2 A and the thickness t2 of the Ag-Cu alloy layer 22B formed in the central region B of the circuit layer 12 and the metal layer 13. B Ratio to t2 A / t2 B is more preferably within the range of 0.8 or more and 1.2 or less, and even more preferably within the range of 0.9 or more and 1.1 or less.

[0055] 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 without departing from the technical concept of the invention. For example, in the present embodiment, a power module is 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.

[0056] In addition, in the insulating circuit board of this embodiment, the ceramic substrate is described as being made of aluminum nitride (AlN) as an example, but the present invention is not limited to this, and other ceramic substrates such as alumina (Al2O3), silicon nitride (Si3N4), etc. may also be used.

[0057] Furthermore, in the present embodiment, Ti is used 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.

[0058] In this embodiment, the thickness of the bonding material applied to the periphery and center of the copper plate is adjusted to reduce the maximum reach L of the active metal diffusion region in the periphery of the circuit layer and the metal layer. A and the maximum reach L of the active metal diffusion region in the central region of the circuit layer and the metal layer. B However, the present invention is not limited to this, and the maximum reach L of the active metal diffusion region in the peripheral region of the circuit layer and the metal layer can be controlled by applying different bonding materials to the peripheral and central portions of the copper plate. A and the maximum reach L of the active metal diffusion region in the central region of the circuit layer and the metal layer. B may be controlled.

[0059] For example, the above-mentioned maximum reach can be controlled by adjusting the specific surface area (BET value) of the Ag powder contained in the bonding material. That is, if the specific surface area of ​​the Ag powder is small, the sinterability of the paste-like bonding material is high, the liquid phase is easily generated during the pressurizing and heating process, the diffusion of the active metal is promoted, and the above-mentioned maximum reach is long. On the other hand, if the specific surface area of ​​the Ag powder is large, the sinterability of the paste-like bonding material is low, the liquid phase is less likely to be generated during the pressurizing and heating process, the diffusion of the active metal is suppressed, and the above-mentioned maximum reach is short. Also, bonding materials containing different types or amounts of active metals may be used to coat the peripheral and central portions of the copper plate.

[0060] Furthermore, in this embodiment, the circuit layer is formed by bonding a rolled sheet of oxygen-free copper to the ceramic substrate, but the present invention is not limited to this, and the circuit layer may be formed by bonding copper pieces punched out of a copper plate to the ceramic substrate in a state of being arranged in a circuit pattern. In this case, it is sufficient that each copper piece has an 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. EXAMPLES

[0061] The results of experiments carried out to confirm the effects of the present invention will be described below.

[0062] First, we prepared ceramic substrates (40 mm x 40 mm) as shown in Table 1. The thicknesses were 0.635 mm for AlN and Al2O3, and 0.32 mm for Si3N4. In addition, copper plates that would become the circuit layers and metal layers were prepared, each of which was made of oxygen-free copper and had a size of 37 mm×37 mm and a thickness shown in Table 1.

[0063] A bonding material containing Ag powder with the BET value shown in Table 1 was applied to the periphery of 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. In addition, a bonding material containing Ag powder with the BET value shown in Table 1 was applied to the center of 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, and the amounts of Ag, Cu, and active metals 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 measurement using N2 adsorption, liquid nitrogen at 77K, and the BET multipoint method.

[0064] 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.

[0065] 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).

[0066] The obtained insulating circuit board (copper / ceramic bonded body) was evaluated for the active metal diffusion region, the active metal compound layer, the Ag-Cu alloy layer, and thermal cycle reliability as described below.

[0067] (Maximum reach of active metal diffusion zone) The cross-sections of the bonding interface between the circuit layer and the ceramic substrate, and the bonding interface between the ceramic substrate and the metal layer were observed using an EPMA device, and elemental maps (200 μm wide x 200 μm high) of the active metals in the circuit layer and the metal layer were obtained in five fields of view each. The maximum reach distance from the active metal compound layer of the active metal diffusion region where the active metal concentration was 0.5 mass% or more was measured. The active metal concentration was determined by taking the total concentration of Ag, Cu, and active metal as 100 mass%. The longest maximum reach distance among the maximum reach distances in 5 visual fields each, for a total of 10 visual fields, is shown in Table 2.

[0068] (Active metal compound layer) The cross-sections of the bonding interface between the circuit layer and the ceramic substrate, and the bonding interface between the ceramic substrate and the metal layer were measured at a magnification of 30,000 times 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 in five fields of view 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 existed in the same region. Observations were made in five fields of view for a total of 10 fields of view, and the area of ​​the range 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 recorded as the "thickness of the active metal compound layer" in Table 2.

[0069] (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. Each elemental mapping was obtained in five fields of view. When Ag+Cu+active metal=100% by mass, the area where the Ag concentration was 15% by mass or more was determined as the Ag-Cu alloy layer, and the area was calculated and divided by the width of the measurement area (area / width of measurement area). The average of these values ​​is shown in Table 2 as the thickness of the Ag-Cu alloy layer.

[0070] (Reliability of thermal cycles) The above-mentioned insulating circuit boards were subjected to the following thermal cycles according to the material of the ceramic substrate, and the presence or absence of ceramic cracks was judged by SAT inspection. The evaluation results are shown in Table 2. For AlN and Al2O3: -40℃×5min ←→ 150℃×5min, SAT inspection every 50 cycles up to 500 cycles. For Si3N4: -40℃×5min ←→ 150℃×5min, SAT inspection every 200 cycles up to 2000 cycles.

[0071] [Table 1]

[0072] [Table 2]

[0073] First, invention examples 1-3, which use AlN as the ceramic substrate, will be compared with comparative examples 1 and 2. In Comparative Example 1, the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate Aand the maximum reach L of the active metal diffusion region in the central region of the copper plate. B The difference between the maximum distance L and the active metal diffusion area in the peripheral area of ​​the copper plate is 15 μm. A The thickness is 12 μm, and cracks occurred 200 times in a thermal cycle test. In Comparative Example 2, the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A The maximum reach L of the active metal diffusion region in the central region of the copper plate is 16 μm. B The thickness is 19 μm, and cracks occurred 150 times in a thermal cycle test.

[0074] In contrast, in Example 1-3 of the present invention, the maximum reach L of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion area from the active metal compound layer in the central region of the copper plate B is within the range of 20 μm to 80 μm, and the maximum reach L A and the maximum reach L B The difference between the temperature and heat resistance is set to 10 μm or less, and the number of cracks that occurred in the thermal cycle test was 300 to 500, demonstrating excellent thermal cycle reliability.

[0075] Next, the present invention examples 4-6, which use Si3N4 as the ceramic substrate, will be compared with the comparative examples 3 and 4. In Comparative Example 3, the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A The maximum reach L of the active metal diffusion region in the central region of the copper plate is 108 μm. B The thickness is 102 μm, and cracks occurred 1,200 times in a thermal cycle test. In Comparative Example 4, the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion region in the central region of the copper plate. B The difference between these values ​​is said to be 14 μm, and cracks occurred 1,400 times in a thermal cycle test.

[0076] In contrast, in Example 4-6 of the present invention, the maximum reach L of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion area from the active metal compound layer in the central region of the copper plate B is within the range of 20 μm to 80 μm, and the maximum reach L A and the maximum reach L B The difference between the temperature and heat resistance is set to 10 μm or less, and the number of times cracks occurred in a thermal cycle test exceeded 1,600 to 2,000, demonstrating excellent thermal cycle reliability.

[0077] Next, invention examples 7 and 8, which used Al2O3 as the ceramic substrate, will be compared with comparative example 5. In Comparative Example 5, the maximum reach L of the active metal diffusion region in the peripheral region of the copper plate A is 16 μm, and the maximum reach of the active metal diffusion area in the central region of the copper plate, L B The thickness is 18 μm, and cracks occurred 50 times in a thermal cycle test.

[0078] In contrast, in Examples 7 and 8 of the present invention, the maximum reach L of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate A and the maximum reach L of the active metal diffusion area from the active metal compound layer in the central region of the copper plate B is within the range of 20 μm to 80 μm, and the maximum reach L A and the maximum reach L B The difference between the temperature and heat resistance is set to 10 μm or less, and the number of cracks that occurred in the thermal cycle test was 350 to 450 times, demonstrating excellent thermal cycle reliability.

[0079] From the results of the above confirmatory experiments, it was confirmed that according to the present invention, even when subjected to severe thermal cycles, the occurrence of cracks in the ceramic members can be suppressed, and an insulated circuit board (copper / ceramic bonded body) with excellent thermal cycle reliability can be provided. [Explanation of symbols]

[0080] 10 Insulated circuit board (copper / ceramic joint) 11 Ceramic substrate (ceramic component) 12 Circuit layer (copper material) 13 Metal layer (copper material) 21(21A,21B) Active metal compound layer 22(22A,22B) Ag-Cu alloy layer 23(23A,23B) Active metal diffusion region

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 a joint interface between the ceramic member and the copper member, an active metal diffusion region is formed on the ceramic member side of the copper member, in which an active metal (Ti, Zr, Nb, Hf) diffuses from the ceramic member side to the copper member side, and the concentration of the active metal in the copper member is 0.5 mass% or more; a maximum reach distance L A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper member and a maximum reach distance L B from the active metal compound layer of the active metal diffusion region in the central region of the copper member are within a range of 20 μm or more and 80 μm or less; The maximum reach L of the active metal diffusion region in the peripheral region of the copper member Ａ and the maximum reach L of the active metal diffusion region in the central region of the copper member. Ｂ A copper / ceramic bonded body, characterized in that the difference between the surface roughness and surface roughness is 10 μm or less.

2. The thickness t1 of the active metal compound layer formed on the peripheral region of the copper member Ａ and a thickness t1 of the active metal compound layer formed in the central region of the copper member. Ｂ is in the range of 0.05 μm or more and 1.2 μm or less, and the thickness ratio t1 Ａ / t1 Ｂ 2. The copper / ceramic bonded body according to claim 1, wherein the coefficient of friction is in the range of 0.7 to 1.

4.

3. an Ag-Cu alloy layer is formed on the copper member side at a bonding interface between the ceramic member and the copper member; The thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper member Ａ and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper member. Ｂ is in the range of 1 μm or more and 30 μm or less, and the thickness ratio t2 Ａ / t2 Ｂ 3. The copper / ceramic bonded body according to claim 1, wherein the coefficient of friction is in the range of 0.7 to 1.

4.

4. An insulating circuit board having a ceramic substrate and a copper plate made of copper or a copper alloy bonded to the surface thereof, an active metal compound layer is formed on the ceramic substrate side at a bonding interface between the ceramic substrate and the copper plate, an active metal diffusion region is formed on the ceramic substrate side of the copper plate, in which an active metal (Ti, Zr, Nb, Hf) is diffused from the ceramic substrate side to the copper plate side, and the concentration of the active metal in the copper plate is 0.5 mass% or more; a maximum reach distance L A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper plate and a maximum reach distance L B from the active metal compound layer of the active metal diffusion region in the central region of the copper plate are within a range of 20 μm or more and 80 μm or less; The maximum reach L of the active metal diffusion region in the peripheral region of the copper plate Ａ and the maximum reach L of the active metal diffusion region in the central region of the copper plate. Ｂ and the difference between the thickness and the thickness is 10 μm or less.

5. The thickness t1 of the active metal compound layer formed in the peripheral region of the copper plate Ａ and a thickness t1 of the active metal compound layer formed in the central region of the copper plate. Ｂ is in the range of 0.05 μm or more and 1.2 μm or less, and the thickness ratio t1 Ａ / t1 Ｂ 5. The insulating circuit board according to claim 4, wherein the resistance is within a range of 0.7 to 1.

4.

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; The thickness t2 of the Ag-Cu alloy layer formed in the peripheral region of the copper plate Ａ and a thickness t2 of the Ag-Cu alloy layer formed in the central region of the copper plate. Ｂ is in the range of 1 μm or more and 30 μm or less, and the thickness ratio t2 Ａ / t2 Ｂ 6. The insulating circuit board according to claim 4, wherein the resistance is within a range of 0.7 to 1.4.

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