Copper / ceramic joints and insulated circuit boards

Abstract

To provide a copper / ceramic assembly excellent in cooling / heating cycle reliability, capable of suppressing occurrence of cracks in a ceramic member even when loaded with a harsh cooling / heating cycle.SOLUTION: Copper members 12 and 13 are bonded to one face and another face of a ceramic member 11, respectively. At the joint interfaces between the ceramic member 11 and the copper members 12 and 13, the maximum value of indentation hardness in a region from 10 μm to 50 μm from the interface between active metal compound layers 21 and 31 and the copper members 12 and 13 to the copper members 12 and 13 sides is 120 mgf / μm2 or more and 200 mgf / μm2 or less. The difference between the maximum value H1 of the indentation hardness of the copper member 12 bonded to the one face and the maximum value H2 of the indentation hardness of the copper member 13 bonded to the other face is 50 mgf / μm2 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 the structure of the bonding interface between a copper plate bonded to one side of a ceramic member and a copper plate bonded to the other side of the ceramic member differs depending on the shapes of the copper members bonded to one side and the other side of the ceramic member, the application condition of the bonding material, the condition of liquid phase generation during bonding, etc. They also found that if the hardness of the bonding interface between one side of a ceramic member and the copper members bonded to the other side is different, the balance of thermal stresses applied to the ceramic member during thermal cycle loading will be disrupted, making the ceramic member more susceptible to cracking.

[0009] The present invention has been made based on the above-mentioned findings, and a 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, The ceramic member contains oxygen (O) or nitrogen (N), the copper members are bonded to one surface and the other surface of the ceramic member, respectively; At a bonding interface between the ceramic member and the copper member bonded to the one surface side and at a bonding interface between the ceramic member and the copper member bonded to the other surface side, On the ceramic member side, Contains oxygen (O) or nitrogen (N) and an active metal selected from Ti, Zr, Nb, and Hf An active metal compound layer is formed, and the maximum indentation hardness in a region of the active metal compound layer extending from the interface with the copper member to the copper member side by 20 μm to 50 μm is 120 mgf / μm 2 More than 200mgf / μm 2 the difference between the maximum value H1 of the indentation hardness of the copper member bonded to the one surface side and the maximum value H2 of the indentation hardness of the copper member bonded to the other surface side is within the range of 50 mgf / μm 2 It is characterized by the following:

[0010] In the present invention, the indentation hardness H is calculated by measuring the load-displacement correlation when a test load of 5000 mgf is applied using a triangular pyramidal diamond indenter called a Berkovich indenter, which has an inter-edge angle of 114.8° or more and 115.1° or less, and using the following formula: hc=ht-0.75×P / S (ht: indentation depth, P: load, S: contact stiffness (= dP / dh|Pmax), hc: contact depth) Contact area A=24.56×hc 2 Indentation hardness H=P / A

[0011] According to the copper / ceramic joined body of the present invention, an active metal compound layer is formed on the ceramic member side at the joining interface between one surface of the ceramic member and the copper member joined to the other surface of the ceramic member, and the maximum indentation hardness of the active metal compound layer in a region from the interface with the copper member to the copper member side, which is 20 μm to 50 μm, is 120 mgf / μm. 2 More than 200mgf / μm 2 Since the content is within the range below, the ceramic member and the copper member are firmly bonded together by the active metal, and the bonded interface is prevented from becoming harder than necessary. The difference between the maximum value H1 of the indentation hardness of the copper member joined to the one surface side and the maximum value H2 of the indentation hardness of the copper member joined to the other surface side is 50 mgf / μm 2 Since the hardness of the bonding interface between one surface of the ceramic member and the copper members bonded to the other surface of the ceramic member is not significantly different, the occurrence of cracks in the ceramic member when subjected to thermal cycle loading can be suppressed, and the ceramic member has excellent thermal cycle reliability.

[0012] In the copper / ceramic joined body of the present invention, it is preferable that at the joining interface between the ceramic member and the copper member, the thickness ta1 of the active metal compound layer formed on the one surface of the ceramic member and the thickness ta2 of the active metal compound layer formed on the other surface of the ceramic member are in the range of 0.05 μm to 1.2 μm, and the thickness ratio ta1 / ta2 is in the range of 0.7 to 1.4. In this case, the thickness ta1 of the active metal compound layer formed on one side of the ceramic member and the thickness ta2 of the active metal compound layer formed on the other side of the ceramic member are 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. Furthermore, since the thickness ratio ta1 / ta2 is within the range of 0.7 or more and 1.4 or less, there is no significant difference in hardness at the bonding interface between one side of the ceramic member and the copper members bonded to the other side, and the occurrence of cracks in the ceramic member when subjected to thermal cycle loading can be further suppressed.

[0013] 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 a ratio tb1 / tb2 of a thickness tb1 of the Ag-Cu alloy layer formed on the one surface of the ceramic member to a thickness tb2 of the Ag-Cu alloy layer formed on the other surface of the ceramic member is in the range of 0.7 to 1.4. In this case, the ratio tb1 / tb2 of the thickness tb1 of the Ag-Cu alloy layer formed on one side of the ceramic member to the thickness tb2 of the Ag-Cu alloy layer formed on the other side of the ceramic member is within the range of 0.7 or more and 1.4 or less, so there is no significant difference in the hardness of the bonding interface between the copper members bonded to one side of the ceramic member and the other side, and the occurrence of cracks in the ceramic member when subjected to thermal cycle loading can be further suppressed.

[0014] Furthermore, in the copper / ceramic bonded body of the present invention, the copper members bonded to one surface and the other surface of the ceramic member, respectively, have an average indentation hardness of 70 mgf / μm in regions of 10 μm to 30 μm from the surface opposite to the ceramic member. 2 More than 90mgf / μm 2It is preferable that the content is within the following range. In this case, the average indentation hardness in a region of 10 μm to 30 μm from the surface of the copper member opposite to the ceramic member is 70 mgf / μm 2 More than 90mgf / μm 2 Since the hardness is within the range below, the copper member as a whole does not become hard, and when other members are joined to the surface of this copper member, the joining reliability with these other members can be improved.

[0015] The insulating circuit board of the present invention is an insulating circuit board having a ceramic substrate and a copper plate made of copper or a copper alloy bonded to the surface of the ceramic substrate, wherein the ceramic substrate contains oxygen (O) or nitrogen (N); the copper plates are bonded to one surface and the other surface of the ceramic substrate, At the bonding interface between the ceramic substrate and the copper plate bonded to the one side and at the bonding interface between the ceramic substrate and the copper plate bonded to the other side, an active metal compound layer containing oxygen (O) or nitrogen (N) and an active metal selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side, and the maximum indentation hardness in a region from the interface with the copper plate to the copper plate side by 20 μm to 50 μm is 120 mgf / μm 2 More than 200mgf / μm 2 The difference between the maximum value H1 of the indentation hardness of the copper plate bonded to one surface side and the maximum value H2 of the indentation hardness of the copper plate bonded to the other surface side is within the range of 50 mgf / μm 2 It is characterized by the following:

[0016] According to the insulating circuit board of the present invention, an active metal compound layer is formed on the ceramic substrate side at the bonding interface between one surface of the ceramic substrate and a copper plate bonded to the other surface of the ceramic substrate, and the maximum indentation hardness in a region of the active metal compound layer extending from the interface with the copper plate to the copper plate side by 20 μm to 50 μm is 120 mgf / μm. 2 More than 200mgf / μm 2Since the content is within the range below, the ceramic substrate and the copper plate are firmly bonded together by the active metal, and the bonded interface is prevented from becoming hard. The difference between the maximum value H1 of the indentation hardness of the copper plate bonded to the one surface side and the maximum value H2 of the indentation hardness of the copper plate bonded to the other surface side is 50 mgf / μm 2 Since the hardness of the bonding interface between the copper plates bonded to one side of the ceramic substrate and the other side of the ceramic substrate is not significantly different, the occurrence of cracks in the ceramic substrate when subjected to thermal cycles can be suppressed, and the ceramic substrate has excellent thermal cycle reliability.

[0017] Here, in the insulating circuit board of the present invention, at the bonding interface between the ceramic substrate and the copper plate, it is preferable that the thickness ta1 of the active metal compound layer formed on one side of the ceramic substrate and the thickness ta2 of the active metal compound layer formed on the other side of the ceramic substrate are in the range of 0.05 μm or more and 1.2 μm or less, and that the thickness ratio ta1 / ta2 is in the range of 0.7 or more and 1.4 or less. In this case, the thickness ta1 of the active metal compound layer formed on one side of the ceramic substrate and the thickness ta2 of the active metal compound layer formed on the other side of the ceramic substrate are 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. Furthermore, since the thickness ratio ta1 / ta2 is within the range of 0.7 or more and 1.4 or less, there is no significant difference in hardness at the bonding interface between one side of the ceramic substrate and the copper plate bonded to the other side, and the occurrence of cracks in the ceramic substrate when subjected to thermal cycle loading can be further suppressed.

[0018] In the insulating circuit board of the present invention, at the bonding interface between the ceramic substrate and the copper plate, Copper plate sideAn Ag-Cu alloy layer is formed on the ceramic member, and it is preferable that the ratio tb1 / tb2 of the thickness tb1 of the Ag-Cu alloy layer formed on the one surface side of the ceramic member to the thickness tb2 of the Ag-Cu alloy layer formed on the other surface side of the ceramic member is in the range of 0.7 to 1.4. In this case, the ratio tb1 / tb2 of the thickness tb1 of the Ag-Cu alloy layer formed on one side of the ceramic substrate to the thickness tb2 of the Ag-Cu alloy layer formed on the other side of the ceramic substrate is within the range of 0.7 or more and 1.4 or less, so there is no significant difference in the hardness of the bonding interface between the copper plates bonded to one side and the other side of the ceramic substrate, and the occurrence of cracks in the ceramic substrate when subjected to thermal cycle loading can be further suppressed.

[0019] Furthermore, in the insulating circuit board of the present invention, the copper plates bonded to one surface and the other surface of the ceramic substrate, respectively, have an average indentation hardness of 70 mgf / μm in a region of 10 μm to 30 μm from the surface opposite the ceramic substrate. 2 More than 90mgf / μm 2 It is preferable that the content is within the following range. In this case, the average indentation hardness in a region of 10 μm to 30 μm from the surface of the copper plate opposite to the ceramic substrate is 70 mgf / μm 2 More than 90mgf / μm 2 Since the hardness is within the range below, the copper plate as a whole does not become hard, and when other members are joined to the surface of this copper plate, the joining reliability with these other members can be improved. [Effects of the Invention]

[0020] 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]

[0021] [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] 1A and 1B are enlarged explanatory views of the bonding interface between the circuit layer and the ceramic substrate and the bonding interface between the metal layer and the ceramic substrate of an insulating circuit board according to an embodiment of the present invention, where (a) is the bonding interface with the circuit layer and (b) is the bonding interface with the metal layer. [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. DETAILED DESCRIPTION OF THE INVENTION

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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 joining punched sheets of rolled oxygen-free copper to the ceramic substrate 11 in a state where the sheets are arranged in a circuit pattern. 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.

[0029] 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.

[0030] At the bonding interface between the ceramic substrate 11 and the circuit layer 12, 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, the maximum value H1 of the indentation hardness in a region E1 extending from the interface between the active metal compound layer 21 and the circuit layer 12 to the circuit layer 12 side by 20 μm to 50 μm is 120 mgf / μm. 2 More than 200mgf / μm 2 It is within the following range:

[0031] At the bonding interface between the ceramic substrate 11 and the metal layer 13, an active metal compound layer 31 and an Ag—Cu alloy layer 32 are formed in this order from the ceramic substrate 11 side, as shown in FIG. In addition, in the metal layer 13, the maximum value H2 of the indentation hardness in the region E2 extending from the interface between the active metal compound layer 31 and the metal layer 13 to the metal layer 13 side by 20 μm to 50 μm is 120 mgf / μm. 2 More than 200mgf / μm 2 It is within the following range:

[0032] In this embodiment, the difference between the maximum value H1 of the indentation hardness of the circuit layer 12 formed on one surface of the ceramic substrate 11 and the maximum value H2 of the indentation hardness of the metal layer 13 formed on the other surface of the ceramic substrate 11 is 50 mgf / μm 2 It is stated as follows.

[0033] In addition, in this embodiment, it is preferable that the thickness ta1 of the active metal compound layer 21 formed on one side of the ceramic substrate 11 and the thickness ta2 of the active metal compound layer 31 formed on the other side of the ceramic substrate 11 are in the range of 0.05 μm or more and 1.2 μm or less, and that the thickness ratio ta1 / ta2 is in the range of 0.7 or more and 1.4 or less. 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 layers 21 and 31 are made of titanium nitride (TiN).

[0034] Furthermore, in this embodiment, it is preferable that the ratio tb1 / tb2 of the thickness tb1 of the Ag-Cu alloy layer 22 formed on one surface of the ceramic substrate 11 to the thickness tb2 of the Ag-Cu alloy layer 32 formed on the other surface of the ceramic substrate 11 be within a range of 0.7 to 1.4. It is also preferable that the thickness of the Ag-Cu alloy layer 22 (Ag-Cu alloy layer 32) be 1 μm to 30 μm.

[0035] In this embodiment, the average indentation hardness of the circuit layer 12 formed on one surface of the ceramic substrate 11 and the metal layer 13 formed on the other surface of the ceramic substrate 11 in regions E3 and E4 that are 10 μm or more and 30 μm or less from the surface opposite to the ceramic substrate 11 is 70 mgf / μm. 2 More than 90mgf / μm 2 It is preferable that the content is within the following range.

[0036] A method for manufacturing the insulating circuit board 10 according to this embodiment will be described below with reference to FIGS.

[0037] (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. Here, the copper plate 42 that will become the circuit layer 12 is a pressed piece arranged in a circuit pattern. 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.

[0038] 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 mass% to 32 mass% and Ti as an active metal in the range of 0.5 mass% to 20 mass%, with the balance being Ag and unavoidable impurities.

[0039] Here, by adjusting the specific surface area (BET value) of the Ag powder contained in the paste-like bonding material 45, the maximum values ​​H1 and H2 of the indentation hardness are controlled in the regions E1 and E2 extending from the interface of the active metal compound layers 21 and 31 with the circuit layer 12 and metal layer 13 toward the circuit layer 12 and metal layer 13, respectively, from 20 μm to 50 μm. That is, when the specific surface area of ​​the Ag powder is small, the sinterability of the paste-like joining material 45 is high, a liquid phase is easily generated in the heating step S03 described later, the diffusion of the active metal is promoted, and the maximum value of the indentation hardness at the joining interface is large. On the other hand, when the specific surface area of ​​the Ag powder is large, the sinterability of the paste-like joining material 45 is low, a liquid phase is less likely to be generated in the heating step S03 described later, the diffusion of the active metal is suppressed, and the maximum value of the indentation hardness at the joining interface is small. The lower limit of the specific surface area of ​​Ag powder is 0.15 m 2 / g or more, and 0.25m 2 / g or more is more preferable, and 0.40m 2 The upper limit of the specific surface area of ​​the Ag powder 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. The particle size of the Ag powder contained in the paste-like bonding material 45 is preferably in the range of D10 being 0.7 μm or more and 3.5 μm or less, and D100 being 4.5 μm or more and 23 μm or less.

[0040] (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.

[0041] (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 pressed together, and the bonding material 45 is melted. Here, the heating temperature in the heating step S03 is preferably within a range of 800° C. to 850° C. In addition, 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 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 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.

[0042] (Cooling process S04) After the 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.

[0043] Here, by adjusting the cooling rate on the circuit layer 12 (copper plate 42) side and the metal layer 13 (copper plate 43) side, the maximum indentation hardness values ​​H1 and H2 in the regions E1 and E2 extending from the interface between the active metal compound layers 21 and 31 and the circuit layer 12 and metal layer 13 to the circuit layer 12 and metal layer 13 side are controlled. That is, when the cooling rate is fast, the diffusion of the active metal stops early and the maximum value of the indentation hardness at the bonded interface becomes small, whereas when the cooling rate is slow, the diffusion of the active metal continues for a long period of time and the maximum value of the indentation hardness at the bonded interface becomes large.

[0044] In the cooling step S04, by flowing an inert gas on either the circuit layer 12 (copper plate 42) side or the metal layer 13 (copper plate 43) side, it is possible to adjust the cooling rate on the circuit layer 12 (copper plate 42) side and the metal layer 13 (copper plate 43) side. Furthermore, when the SPS (spark plasma sintering) method is applied in the heating step S03 and the cooling step S04, the cooling rate can be adjusted on the circuit layer 12 (copper plate 42) side and the metal layer 13 (copper plate 43) side by adjusting the flow rate of the cooling water between the electrode on the circuit layer 12 (copper plate 42) side and the electrode on the metal layer 13 (copper plate 43) side.

[0045] 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 heating step S03, and the cooling step S04.

[0046] (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 .

[0047] (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.

[0048] In the insulating circuit board 10 (copper / ceramic bonded body) of this embodiment configured as described above, active metal compound layers 21, 31 are formed on the ceramic substrate 11 side at the bonding interface between the circuit layer 12 formed on one surface of the ceramic substrate 11 and the metal layer 13 formed on the other surface, and the maximum indentation hardnesses H1, H2 in regions E1, E2 extending from the interfaces of the active metal compound layers 21, 31 with the circuit layer 12 and metal layer 13 to the circuit layer 12 and metal layer 13 sides by 20 μm to 50 μm are 120 mgf / μm. 2 As described above, the active metal of the bonding material 45 has reacted sufficiently, and the ceramic substrate 11, the circuit layer 12, and the metal layer 13 are firmly bonded together. On the other hand, the maximum values ​​H1 and H2 of the indentation hardness in the regions E1 and E2 extending from the interface between the active metal compound layers 21 and 31 and the circuit layer 12 and the metal layer 13 to the circuit layer 12 and the metal layer 13 side are 200 mgf / μm. 2 Since the bonded interface is prevented from becoming harder than necessary, the thermal cycle reliability can be improved.

[0049] In order to bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13 more firmly, the maximum values ​​H1 and H2 of the indentation hardness at the bonding interface are set to 125 mgf / μm. 2 It is preferable that the density is 130 mgf / μm or more. 2 More preferably, it is set to the above. In order to further prevent the joining interface from becoming harder than necessary, the maximum values ​​H1 and H2 of the indentation hardness of the joining interface are set to 180 mgf / μm 2 It is preferable that the density is 150 mgf / μm or less. 2 It is more preferable to set the following:

[0050] In this embodiment, the difference between the maximum value H1 of the indentation hardness of the circuit layer 12 formed on one surface of the ceramic substrate 11 and the maximum value H2 of the indentation hardness of the metal layer 13 formed on the other surface of the ceramic substrate 11 is 50 mgf / μm 2 Since the hardness of the bonding interface between the circuit layer 12 formed on one surface of the ceramic substrate 11 and the metal layer 13 formed on the other surface of the ceramic substrate 11 is not significantly different, the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycles can be suppressed, and the ceramic substrate 11 has excellent thermal cycle reliability.

[0051] In order to further improve the thermal cycle reliability, the difference between the maximum value H1 of the indentation hardness of the circuit layer 12 formed on one surface of the ceramic substrate 11 and the maximum value H2 of the indentation hardness of the metal layer 13 formed on the other surface of the ceramic substrate 11 is set to 40 mgf / μm 2 It is preferable that the density is 30 mgf / μm or less. 2 It is more preferable to set the following:

[0052] Furthermore, in this embodiment, when the thickness ta1 of the active metal compound layer 21 formed on the circuit layer 12 side formed on one surface of the ceramic substrate 11 and the thickness ta2 of the active metal compound layer 31 formed on the metal layer 13 side formed on the other surface of the ceramic substrate 11 are 0.05 μm or more, the active metal of the bonding material 45 reacts sufficiently with the ceramic substrate 11, and the ceramic substrate 11 is bonded even more firmly to the circuit layer 12 and the metal layer 13. On the other hand, when the thickness ta1 of the active metal compound layer 21 and the thickness ta2 of the active metal compound layer 31 are set to 1.2 μm or less, the bonding interface can be prevented from becoming harder than necessary, and the thermal cycle reliability can be further improved.

[0053] In addition, in order to further firmly bond the ceramic substrate 11 to the circuit layer 12 and the metal layer 13, it is preferable that the thickness ta1 of the active metal compound layer 21 and the thickness ta2 of the active metal compound layer 31 be 0.08 μm or more, and it is even more preferable that they be 0.15 μm or more. In addition, in order to further prevent the bonding interface from becoming unnecessarily hard, it is preferable that the thickness ta1 of the active metal compound layer 21 and the thickness ta2 of the active metal compound layer 31 be 1.0 μm or less, and it is more preferable that they be 0.6 μm or less.

[0054] Furthermore, in this embodiment, when the thickness ratio ta1 / ta2 of the thickness ta1 of the active metal compound layer 21 and the thickness ta2 of the active metal compound layer 31 is within the range of 0.7 or more and 1.4 or less, there is no significant difference in the hardness of the bonding interface between the circuit layer 12 formed on one side of the ceramic substrate 11 and the metal layer 13 formed on the other side of the ceramic substrate 11, and the occurrence of cracks in the ceramic substrate 11 when subjected to a thermal cycle load can be further suppressed. In addition, in order to further suppress the occurrence of cracks in the ceramic substrate 11 during thermal cycle loading, it is more preferable that the thickness ratio ta1 / ta2 of the thickness ta1 of the active metal compound layer 21 to the thickness ta2 of the active metal compound layer 31 is in the range of 0.8 or more and 1.2 or less, and even more preferable that it is in the range of 0.9 or more and 1.1 or less.

[0055] Furthermore, in this embodiment, when the ratio tb1 / tb2 of the thickness tb1 of the Ag-Cu alloy layer 22 formed on one side of the ceramic substrate 11 to the thickness tb2 of the Ag-Cu alloy layer 32 formed on the other side of the ceramic substrate 11 is within the range of 0.7 or more and 1.4 or less, there is no significant difference in the hardness of the bonding interface between the circuit layer 12 formed on one side of the ceramic substrate 11 and the metal layer 13 formed on the other side of the ceramic substrate 11, and the occurrence of cracks in the ceramic substrate 11 when subjected to thermal cycle loading can be further suppressed. In addition, in order to further suppress the occurrence of cracks in the ceramic substrate 11 during thermal cycle loading, it is more preferable to set the thickness ratio tb1 / tb2 between the thickness tb1 of the Ag-Cu alloy layer 22 and the thickness tb2 of the Ag-Cu alloy layer 32 in the range of 0.8 or more and 1.2 or less, and even more preferable to set it in the range of 0.9 or more and 1.1 or less.

[0056] Furthermore, in this embodiment, the average value of indentation hardness in regions E3 and E4, which are 10 μm or more and 30 μm or less from the surface opposite to the ceramic substrate 11, of the circuit layer 12 formed on one surface of the ceramic substrate 11 and the metal layer 13 formed on the other surface of the ceramic substrate 11, is 70 mgf / μm. 2 More than 90mgf / μm 2 When the temperature is within the range below, the entire circuit layer 12 and the entire metal layer 13 do not harden, and the bonding reliability between the semiconductor element 3 bonded to the surface of the circuit layer 12 and the heat sink 5 bonded to the surface of the metal layer 13 can be improved.

[0057] 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.

[0058] 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.

[0059] 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. [Example]

[0060] The results of confirmation experiments conducted to confirm the effects of the present invention will be described below.

[0061] 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. Two 37mm x 18mm copper pieces made of oxygen-free copper were prepared as copper plates to serve as circuit layers, with the thicknesses shown in Table 1. Furthermore, another 37mm x 37mm copper plate made of oxygen-free copper with the thicknesses shown in Table 1 was prepared as a copper plate to serve as a metal layer.

[0062] A bonding material containing Ag powder with a BET value shown in Table 1 was applied to a copper plate that would become a circuit layer so that the target thickness after drying would be 30 μm. A bonding material containing Ag powder with a BET value shown in Table 1 was applied to a copper plate that would become a metal layer so that the target thickness after drying would be 30 μm. The bonding material used was a paste material, 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 including vacuum degassing at 150°C for 30 minutes, followed by N2 adsorption and liquid nitrogen at 77K using the BET multi-point method.

[0063] A copper plate, which would become the circuit layer, was laminated on one side of the ceramic substrate, with two copper pieces spaced 1 mm apart. A copper plate serving as a metal layer was laminated on the other surface of the ceramic substrate.

[0064] This laminate was heated while being pressed in the lamination direction to melt the bonding material. At this time, the pressure load was 0.196 MPa, and the temperature integral value was 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). In the examples, the joining was performed using the SPS (spark plasma sintering) method, and the cooling rates shown in Table 2 were adjusted by adjusting the flow rates of the cooling water between the electrode on the circuit layer side and the electrode on the metal layer side.

[0065] The obtained insulating circuit board (copper / ceramic bonded body) was evaluated for indentation hardness, active metal compound layer, Ag—Cu alloy layer, and thermal cycle reliability as follows.

[0066] (indentation hardness) The obtained insulating circuit board (copper / ceramic bonded body) was cut in the lamination direction, and the indentation hardness was measured and calculated at five points in the bonding interface between the ceramic substrate and the circuit layer and metal layer, in a region from 20 μm to 50 μm toward the circuit layer and metal layer from the interface between the active metal compound layer and the circuit layer and metal layer, using the method described above, and the maximum value was determined. In addition, the indentation hardness was measured and calculated at five points in the region of 10 μm to 30 μm from the surface of the circuit layer and the metal layer opposite to the ceramic substrate, and the average value was calculated.

[0067] (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, and the average value obtained by dividing the area in which the active metal element and N or O existed in the same region by the measured width was taken as the "thickness of the active metal compound layer."

[0068] (Ag-Cu alloy layer) The cross section of the bonding interface between the circuit layer and the ceramic substrate, and the bonding interface between the ceramic substrate and the metal layer was subjected to line analysis in five fields of view using an EPMA device. When Ag + Cu + active metal = 100 mass%, the area where the Ag concentration was 15 mass% or more was defined as the Ag-Cu alloy layer, and its thickness was measured. The average of the measurements in five fields of view was reported as the thickness of the Ag-Cu alloy layer in the table.

[0069] (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.

[0070] [Table 1]

[0071] [Table 2]

[0072] When comparing Invention Examples 1-3 and Comparative Examples 1 and 2, which used AlN as the ceramic substrate, the maximum values ​​of the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side were 120 mgf / μm 2 More than 200mgf / μm 2 The difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side is 50 mgf / μm. 2 In the present invention example 1-3, the difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side is 61 mgf / μm 2 The maximum value of the indentation hardness H2 on the metal layer side was 217 mgf / μm 2 It is confirmed that the thermal cycle reliability is superior to that of Comparative Example 2, which was evaluated as "1".

[0073] When comparing Examples 4-6 of the present invention and Comparative Examples 3 and 4, which used Si3N4 as the ceramic substrate, the maximum values ​​of the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side were 120 mgf / μm 2 More than 200mgf / μm 2 The difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side is 50 mgf / μm. 2 In the present invention examples 4-6, the difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side is 62 mgf / μm 2 Comparative Example 3, in which the difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side was 55 mgf / μm 2 It is confirmed that the thermal cycle reliability is superior to that of Comparative Example 4, which was rated as "1".

[0074] When comparing Invention Examples 7 and 8 and Comparative Example 5, which used Al2O3 as the ceramic substrate, the maximum values ​​of the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side were 120 mgf / μm 2More than 200mgf / μm 2 The difference between the indentation hardness H1 on the circuit layer side and the indentation hardness H2 on the metal layer side is 50 mgf / μm. 2 In Examples 7 and 8 of the present invention, the maximum value of the indentation hardness H2 on the metal layer side was 94 mgf / μm 2 It is confirmed that the thermal cycle reliability is superior to that of Comparative Example 5, which was evaluated as "1".

[0075] 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 (ceramic member) even when subjected to severe thermal cycles, and can provide an insulated circuit board (copper / ceramic bonded body) with excellent thermal cycle reliability. [Explanation of symbols]

[0076] 10 Insulated circuit board (copper / ceramic bonded body) 11 Ceramic substrate (ceramic component) 12 Circuit layer (copper material) 13 Metal layer (copper material) 21,31 Active metal compound layer 22,32 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, The ceramic member contains oxygen (O) or nitrogen (N), the copper members are bonded to one surface and the other surface of the ceramic member, respectively; At the bonding interface between the ceramic member and the copper member bonded to the one surface side and at the bonding interface between the ceramic member and the copper member bonded to the other surface side, an active metal compound layer containing oxygen (O) or nitrogen (N) and an active metal selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side, and the maximum indentation hardness in a region of the active metal compound layer from the interface with the copper member to the copper member side is 120 mgf / μm ２ More than 200mgf / μm ２ Within the following range: The difference between the maximum value H1 of the indentation hardness of the copper member joined to the one surface side and the maximum value H2 of the indentation hardness of the copper member joined to the other surface side is 50 mgf / μm ２ A copper / ceramic joined body characterized by the following:

2. 2. The copper / ceramic joined body according to claim 1, wherein a thickness ta1 of the active metal compound layer formed on the one surface of the ceramic member and a thickness ta2 of the active metal compound layer formed on the other surface of the ceramic member are in the range of 0.05 μm to 1.2 μm, and a thickness ratio ta1 / ta2 is in the range of 0.7 to 1.

4.

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 a ratio tb1 / tb2 of a thickness tb1 of the Ag-Cu alloy layer formed on the one surface of the ceramic member to a thickness tb2 of the Ag-Cu alloy layer formed on the other surface of the ceramic member is within a range of 0.7 to 1.

4.

4. The copper members bonded to one surface and the other surface of the ceramic member have an average indentation hardness of 70 mgf / μm in a region of 10 μm to 30 μm from the surface opposite to the ceramic member. ２ More than 90mgf / μm ２ 4. The copper / ceramic joined body according to claim 1, wherein the thickness of the copper / ceramic bonded body is within the following range:

5. An insulating circuit board having a copper plate made of copper or a copper alloy bonded to the surface of a ceramic substrate, the ceramic substrate contains oxygen (O) or nitrogen (N), the copper plates are bonded to one surface and the other surface of the ceramic substrate, At the bonding interface between the ceramic substrate and the copper plate bonded to the one side and at the bonding interface between the ceramic substrate and the copper plate bonded to the other side, an active metal compound layer containing oxygen (O) or nitrogen (N) and an active metal selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side, and the maximum indentation hardness in a region from the interface with the copper plate to the copper plate side by 20 μm to 50 μm is 120 mgf / μm. ２ More than 200mgf / μm ２ Within the following range: The difference between the maximum value H1 of the indentation hardness of the copper plate joined to the one surface side and the maximum value H2 of the indentation hardness of the copper plate joined to the other surface side is 50 mgf / μm ２ An insulating circuit board characterized by:

6. 6. The insulating circuit board according to claim 5, wherein a thickness ta1 of the active metal compound layer formed on said one surface of said ceramic substrate and a thickness ta2 of the active metal compound layer formed on said other surface of said ceramic substrate are within a range of 0.05 μm or more and 1.2 μm or less, and a thickness ratio ta1 / ta2 is within a range of 0.7 or more and 1.4 or less.

7. an Ag—Cu alloy layer is formed on the copper plate side at the bonding interface between the ceramic substrate and the copper plate; 7. The insulating circuit board according to claim 5, wherein a ratio tb1 / tb2 of a thickness tb1 of the Ag-Cu alloy layer formed on one surface of the ceramic substrate to a thickness tb2 of the Ag-Cu alloy layer formed on the other surface of the ceramic substrate is within a range of 0.7 to 1.

4.

8. The copper plates bonded to one surface and the other surface of the ceramic substrate have an average indentation hardness of 70 mgf / μm in a region of 10 μm to 30 μm from the surface opposite to the ceramic substrate. ２ More than 90mgf / μm ２ 8. The insulating circuit board according to claim 5, wherein the thickness is within the following range:

Images