Copper-ceramic joint and insulated circuit board

Abstract

The copper-ceramic joint body of the present application is a copper-ceramic joint body (10) formed by joining a copper member (12, 13) composed of copper or a copper alloy and a ceramic member (11), in an end region (E) of the copper member (12, 13), the area ratio of an Ag solid solution portion (12A, 13A) in which the Ag concentration is 0.5 mass% or more and 15 mass% or less is in a range of 0.03 or more and 0.35 or less.

Description

Technical Field

[0001] The present invention relates to a copper-ceramic bonding body formed by joining a copper component made of copper or a copper alloy and a ceramic component, and an insulating circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate.

[0002] This application claims priority based on Japanese Patent Application No. 2021-125532, filed on July 30, 2021, the contents of which are incorporated herein by reference. Background Technology

[0003] Power modules, LED modules, and thermoelectric modules are structures formed by bonding power semiconductor elements, LED elements, and thermoelectric elements onto an insulating circuit board on one side of an insulating layer where a circuit layer made of conductive material is formed.

[0004] For example, power semiconductor devices used for controlling high-power applications such as wind power generation, electric vehicles, and hybrid electric vehicles generate a lot of heat during operation. Therefore, as the substrate on which these power semiconductor devices are mounted, the following insulating circuit board has been widely used. This insulating circuit board includes: a ceramic substrate; a circuit layer formed by bonding a metal plate with excellent conductivity to one side of the ceramic substrate; and a heat dissipation metal layer formed by bonding a metal plate to the other side of the ceramic substrate.

[0005] For example, Patent Document 1 discloses 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 placed on one and the other sides of a ceramic substrate with an Ag-Cu-Ti solder between them, and the copper plates are bonded by heat treatment (so-called active metal brazing).

[0006] Furthermore, Patent Document 2 proposes a power module substrate that uses a bonding material containing Ag and Ti to bond a copper plate made of copper or a copper alloy and a ceramic substrate made of AlN or Al2O3.

[0007] Furthermore, Patent Document 3 discloses a power module substrate that uses a solder composed of Al-Si, Al-Ge, Al-Cu, Al-Mg, or Al-Mn alloys to bond an aluminum plate or aluminum alloy to a ceramic substrate. In this Patent Document 3, protrusions are formed around a circuit layer formed on one side of the ceramic substrate and a heat dissipation layer formed on the other side. This ensures the insulation between the circuit layer and the heat dissipation layer and increases the heat capacity of both.

[0008] Patent Document 1: Japanese Patent No. 3211856 (B)

[0009] Patent Document 2: Japanese Patent No. 5757359 (B)

[0010] Patent Document 3: Japanese Patent No. 5957862 (B)

[0011] However, there has been a recent trend of increasing heat generation temperature of semiconductor devices mounted on insulating circuit boards. As a result, insulating circuit boards are required to have higher thermal cycling reliability than ever before, capable of withstanding severe thermal cycling.

[0012] In the case of an insulating circuit board formed by bonding a copper plate and a ceramic substrate, as described in Patent Document 3, when a protrusion is formed in the circuit layer, thermal stress is concentrated at the end of the circuit layer when subjected to thermal cycling, and the bonding reliability may decrease.

[0013] Furthermore, the ends of copper components will solidify due to the Ag solid solution contained in the bonding material. When the ends of copper components harden due to solidification, thermal stress is still concentrated at the ends of the circuit layer, which may reduce the reliability of the bonding. Summary of the Invention

[0014] The present invention was made in view of the above circumstances, and its object is to provide a copper-ceramic bonding body that can suppress the generation of cracks in ceramic components even under severe thermal cycling and has excellent thermal cycling reliability, and an insulating circuit board made of the copper-ceramic bonding body.

[0015] To address the aforementioned issues, one aspect of the present invention relates to a copper-ceramic joint formed by joining a copper component made of copper or a copper alloy and a ceramic component, characterized in that, in the end region of the copper component, the area ratio of the Ag solid solution portion with an Ag concentration of 0.5% by mass or more and 15% by mass or less is in the range of 0.03 or more and 0.35 or less.

[0016] Furthermore, the end region of the copper component in this invention refers to the region within the following range in a cross section along the stacking direction of the copper-ceramic bond: a width of 100 μm from the end of the copper component toward the central side of the copper component and a height from the bonding surface of the ceramic component to the surface of the copper component on the side opposite to the ceramic component.

[0017] According to one aspect of the present invention, the copper-ceramic joint has an area ratio of Ag solid solution with an Ag concentration of 0.5% by mass or more and 15% by mass or less in the end region of the copper component of 0.03 or more. Therefore, even at the end of the copper component, Ag reacts sufficiently at the interface with the ceramic component, and the ceramic component and the copper component can be firmly bonded together.

[0018] Furthermore, since the area ratio of the Ag solid solution portion is less than 0.35, it prevents the end region of the copper component from becoming too hard due to solid solution solidification, and it can suppress cracking or peeling of the ceramic component under load thermal cycling.

[0019] In this embodiment of the invention, in the copper-ceramic joint, it is preferable that an active metal compound layer is formed on the ceramic component side at the joint interface between the ceramic component and the copper component, wherein the thickness t1 of the active metal compound layer is in the range of 0.05 μm or more and 0.8 μm or less.

[0020] At this time, since an active metal compound layer is formed on the ceramic component side, and the thickness t1 of the active metal compound layer is in the range of 0.05 μm or more and 0.8 μm or less, the ceramic component and the copper component are reliably and firmly bonded by the active metal, and the hardening of the bonding interface is further suppressed.

[0021] Furthermore, in the copper-ceramic joint according to one aspect of the present invention, preferably an Ag-Cu alloy layer is formed on the copper component side at the joint interface between the ceramic component and the copper component, wherein the thickness t2 of the Ag-Cu alloy layer is in the range of 1 μm or more and 15 μm or less.

[0022] At this time, since an Ag-Cu alloy layer is formed on the side of the copper component at the interface between the ceramic component and the copper component, and the thickness t2 of the Ag-Cu alloy layer is in the range of 1 μm or more and 15 μm or less, the Ag of the bonding material reacts fully with the copper component, thereby reliably and firmly bonding the ceramic component and the copper component, and further suppressing the hardening of the bonding interface.

[0023] One aspect of the present invention relates to an insulating circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate, characterized in that, in the end region of the copper plate, the area ratio of the Ag solid solution portion with an Ag concentration of 0.5% by mass or more and 15% by mass or less is in the range of 0.03 or more and 0.35 or less.

[0024] Furthermore, the end region of the copper plate in this invention refers to the region within the following range in a cross section along the stacking direction of the insulating circuit substrate: a width of 100 μm from the end of the copper plate toward the center of the copper plate and a height from the bonding surface of the ceramic substrate to the surface of the copper plate on the side opposite to the ceramic substrate.

[0025] According to one aspect of the present invention, the insulating circuit board has an area ratio of Ag solid solution with an Ag concentration of 0.5% by mass or more and 15% by mass or less in the end region of the copper plate of 0.03 or more. Therefore, even at the end of the copper plate, Ag reacts sufficiently at the interface with the ceramic substrate, and the ceramic substrate and the copper plate can be firmly bonded.

[0026] Furthermore, since the area ratio of the Ag solid solution portion is 0.35 or less, it prevents the end region of the copper plate from becoming too hard due to solid solution solidification, and it can suppress cracking or peeling of the ceramic substrate under load thermal cycling.

[0027] In this invention, in the insulating circuit substrate, preferably at the interface between the ceramic substrate and the copper plate, an active metal compound layer is formed on the ceramic substrate side, and the thickness t1 of the active metal compound layer is in the range of 0.05 μm or more and 0.8 μm or less.

[0028] At this time, since an active metal compound layer is formed on the ceramic substrate side at the bonding interface between the ceramic substrate and the copper plate, and the thickness t1 of the active metal compound layer is in the range of 0.05μm or more and 0.8μm or less, the ceramic substrate and the copper plate are reliably and firmly bonded by the active metal, and the hardening of the bonding interface is further suppressed.

[0029] Furthermore, in the insulating circuit substrate according to one aspect of the present invention, preferably at the interface between the ceramic substrate and the copper plate, an Ag-Cu alloy layer is formed on the copper plate side, and the thickness t2 of the Ag-Cu alloy layer is in the range of 1 μm or more and 15 μm or less.

[0030] At this time, since 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 is in the range of 1 μm or more and 15 μm or less, the Ag of the bonding material reacts fully with the copper plate, thereby reliably and firmly bonding the ceramic substrate and the copper plate, and further suppressing the hardening of the bonding interface.

[0031] According to the present invention, a copper-ceramic bonding material that can suppress the generation of cracks in ceramic components even under severe thermal cycling and has excellent thermal cycling reliability, and an insulating circuit board made of the copper-ceramic bonding material, can be provided. Attached Figure Description

[0032] Figure 1 This is a schematic diagram illustrating a power module using an insulating circuit board according to an embodiment of the present invention.

[0033] Figure 2This is an enlarged illustration of the ends of the circuit layer and metal layer of the insulating circuit board according to an embodiment of the present invention.

[0034] Figure 3 This is an enlarged illustration of the interface between the circuit layer and the metal layer of the insulating circuit board and the ceramic substrate according to the embodiments of the present invention.

[0035] Figure 4 This is a flowchart of a method for manufacturing an insulating circuit board according to an embodiment of the present invention.

[0036] Figure 5 This is a schematic diagram illustrating a method for manufacturing an insulating circuit board according to an embodiment of the present invention. Detailed Implementation

[0037] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0038] The copper-ceramic bonding body involved in this embodiment is an insulating circuit board 10 formed by bonding a ceramic substrate 11, which is a ceramic component made of ceramic, and copper plates 42 (circuit layer 12) and 43 (metal layer 13), which are copper components made of copper or copper alloy. Figure 1 A power module 1 equipped with the insulating circuit board 10 of this embodiment is shown.

[0039] The power module 1 includes: an insulating circuit board 10 provided with a circuit layer 12 and a metal layer 13; on one side of the circuit layer 12 (on Figure 1 The semiconductor element 3 (top) is bonded via bonding layer 2; and the semiconductor element 3 is disposed on the other side of metal layer 13 (in... Figure 1 The radiator 5 is located on the lower side (in the middle).

[0040] Semiconductor element 3 is made of semiconductor material such as Si. Semiconductor element 3 is bonded to circuit layer 12 via bonding layer 2.

[0041] The bonding layer 2 is composed of, for example, Sn-Ag, Sn-In, or Sn-Ag-Cu solder materials.

[0042] The heat sink 5 is used to dissipate heat from the aforementioned insulating circuit board 10. The heat sink 5 is made of copper or a copper alloy; in this embodiment, it is made of phosphorus-deoxidized copper. A flow path for cooling fluid is provided in the heat sink 5.

[0043] In this embodiment, the heat sink 5 and the metal layer 13 are bonded by a solder layer 7 made of solder material. The solder layer 7 is made of, for example, Sn-Ag, Sn-In, or Sn-Ag-Cu solder material.

[0044] And, as Figure 1As shown, the insulating circuit board 10 of this embodiment includes: a ceramic substrate 11; and a surface disposed on one side of the ceramic substrate 11 (on...). Figure 1 The circuit layer 12 (top) and the circuit layer disposed on the other side of the ceramic substrate 11 (on the top). Figure 1 The metal layer 13 (with the middle layer below) is located below.

[0045] The ceramic substrate 11 is made of ceramics such as silicon nitride (Si3N4), aluminum nitride (AlN), and alumina (Al2O3), which have excellent insulation and heat dissipation properties. In this embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN), which has particularly excellent heat dissipation properties. Furthermore, the thickness of the ceramic substrate 11 is set, for example, in the range of 0.2 mm or more and 1.5 mm or less; in this embodiment, it is set to 0.635 mm.

[0046] like Figure 5 As shown, the circuit layer 12 is located on one side of the ceramic substrate 11 (on... Figure 5 The middle part (top) is formed by joining a copper plate 42 made of copper or a copper alloy.

[0047] In this embodiment, the circuit layer 12 is formed by bonding an oxygen-free copper rolled plate onto a ceramic substrate 11.

[0048] Furthermore, the thickness of the copper plate 42 that forms the circuit layer 12 is set in the range of 0.1 mm or more and 2.0 mm or less; in this embodiment, it is set to 0.6 mm.

[0049] like Figure 5 As shown, the metal layer 13 passes through the other side of the ceramic substrate 11 (on the other side). Figure 5 (The middle part is below) is formed by joining copper plates 43 made of copper or copper alloys.

[0050] In this embodiment, the metal layer 13 is formed by bonding an oxygen-free copper rolled plate onto a ceramic substrate 11.

[0051] Furthermore, the thickness of the copper plate 43 that forms the metal layer 13 is set in the range of 0.1 mm or more and 2.0 mm or less; in this embodiment, it is set to 0.6 mm.

[0052] And, as Figure 2As shown, in the insulating circuit board 10 of this embodiment, at the interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13, in the end region E (the region surrounded by the dashed line) of the circuit layer 12 and the metal layer 13, the area ratio of Ag solid solution portions 12A and 13A with an Ag concentration of 0.5% by mass or more and 15% by mass or less is in the range of 0.03 or more and 0.35 or less. The Ag solid solution portions 12A and 13A are mainly formed in the end region E near the side surfaces (left and right end faces) of the circuit layer 12 and the metal layer 13 and at the interface with the ceramic substrate 11.

[0053] In this embodiment, the Ag solid solution portions 12A and 13A are regions where, when EPMA (electron probe microanalysis) analysis is performed on the ends of the circuit layer 12 and the metal layer 13, and the total amount of Cu, Ag contained in the bonding material 45 (described later), and active elements is set to 100% by mass, the Ag concentration is 0.5% by mass or more and 15% by mass or less.

[0054] In addition, such as Figure 2 As shown, the Ag solid solution portions 12A and 13A sometimes exist at the interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13, the end faces of the circuit layer 12 and the metal layer 13, and the surface side of the ends of the circuit layer 12 and the metal layer 13.

[0055] And, as Figure 2 As shown, the end region E in this embodiment refers to the region that, in a cross-sectional view along the stacking direction of the ceramic substrate 11, has a width of 100 μm from the ends of the circuit layer 12 and the metal layer 13 toward the center of the circuit layer 12 and the metal layer 13, and a thickness t (the distance from the surface of the ceramic substrate 11 to the surface of the circuit layer 12 and the metal layer 13 facing the side opposite to the ceramic substrate 11). Furthermore, when Ag solid solution portions 12A and 13A are formed on the end faces of the circuit layer 12 and the metal layer 13, the width of the end region E is 100 μm from the ends of these Ag solid solution portions 12A and 13A toward the center of the circuit layer 12 and the metal layer 13.

[0056] And, as Figure 3 As shown, in this embodiment, it is preferable to form an active metal compound layer 21 at the interface with the circuit layer 12 and the metal layer 13, and the thickness t1 of the active metal compound layer 21 is in the range of 0.05 μm or more and 0.8 μm or less.

[0057] Here, the active metal compound layer 21 is a layer composed of compounds of active metals (selected from one or more of Ti, Zr, Nb, and Hf) used in the bonding material 45. More specifically, when the ceramic substrate is composed of silicon nitride (Si3N4) or aluminum nitride (AlN), it becomes a layer composed of nitrides of these active metals; when the ceramic substrate is aluminum oxide (Al2O3), it becomes a layer composed of oxides of these active metals. The active metal compound layer 21 is formed by the aggregation of particles of the active metal compound. The average particle size is 10 nm or more and 100 nm or less.

[0058] Furthermore, in this embodiment, the bonding material 45 contains Ti as an active metal. Since the ceramic substrate 11 is made of aluminum nitride, the active metal compound layer 21 is made of titanium nitride (TiN). That is, it is formed by the aggregation of titanium nitride (TiN) particles with an average particle size of 10 nm or more and 100 nm or less.

[0059] In addition, such as Figure 3 As shown, in this embodiment, preferably at the interface with the circuit layer 12 and the metal layer 13, an Ag-Cu alloy layer 22 is formed on the side of the circuit layer 12 and the metal layer 13 of the active metal compound layer 21, and the thickness t2 of the Ag-Cu alloy layer 22 is 1 μm or more and 15 μm or less.

[0060] Alternatively, the active metal compound layer 21 can be considered part of the ceramic substrate (ceramic component) 11. The Ag-Cu alloy layer 22 can also be considered part of the circuit layer (copper component) 12 and the metal layer (copper component) 13. Therefore, the interface between the ceramic substrate 11 and the circuit layer 12 and metal layer 13 (copper plates 42, 43) is the interface between the active metal compound layer 21 and the Ag-Cu alloy layer 22. When the Ag-Cu alloy layer 22 is absent, the interface between the ceramic substrate 11 and the circuit layer 12 and metal layer 13 (copper plates 42, 43) is the interface between the active metal compound layer 21 and the circuit layer 12 and metal layer 13 (copper plates 42, 43).

[0061] The following is for reference. Figure 4 and Figure 5 The manufacturing method of the insulating circuit board 10 according to this embodiment will be described.

[0062] (Joint material preparation process S01)

[0063] Copper plate 42 is prepared to become circuit layer 12 and copper plate 43 is prepared to become metal layer 13.

[0064] Furthermore, a bonding material 45 is applied to the bonding surface of the copper plate 42, which forms the circuit layer 12, and the copper plate 43, which forms the metal layer 13, and then dried. The coating thickness of the paste-like bonding material 45 is preferably set in the range of 10 μm or more and 50 μm or less after drying.

[0065] In this embodiment, the paste-like bonding material 45 is applied by screen printing.

[0066] The bonding material 45 contains Ag and an active metal (selected from one or more of Ti, Zr, Nb, and Hf). In this embodiment, an Ag-Ti solder (Ag-Cu-Ti solder) is used as the bonding material 45. Furthermore, as the Ag-Ti solder (Ag-Cu-Ti solder), a solder with the following composition is preferably used, for example: the solder contains Cu in the range of 0% to 45% by mass and Ti as an active metal in the range of 0.5% to 20% by mass, with the remainder being Ag and unavoidable impurities.

[0067] Here, for the coated bonding material 45, the equivalent film thickness of Ag and the mass ratio of Ag to active metal (Ag / active metal) are adjusted. Therefore, in the pressurization and heating process S03 described later, the absolute amount and flowability of the generated Ag-Cu liquid phase can be controlled.

[0068] Specifically, it is preferable to set the equivalent film thickness of Ag to 2.5 μm or more, and more preferably to 3.5 μm or more. On the other hand, it is preferable to set the equivalent film thickness of Ag to 10 μm or less, and more preferably to 8 μm or less.

[0069] Furthermore, it is preferable to set the mass ratio of Ag to active metal (Ag / active metal) to 8 or more, more preferably 12 or more. On the other hand, it is preferable to set the mass ratio of Ag to active metal (Ag / active metal) to 60 or less, more preferably 45 or less.

[0070] Furthermore, the specific surface area of ​​the Ag powder contained in the bonding material 45 is preferably 0.15 m². 2 / g or more, preferably 0.25m 2 / g or more, further preferably 0.40m 2 / g or more. On the other hand, the specific surface area of ​​the Ag powder contained in the bonding material 45 is preferably 1.40m². 2 / g or less, more preferably 1.00m 2 / g or less, more preferably 0.75m 2 / g or less.

[0071] Furthermore, regarding the particle size of the Ag powder contained in the paste-like bonding material 45, D10 is preferably in the range of 0.7 μm or more and 3.5 μm or less, and D100 is in the range of 4.5 μm or more and 23 μm or less. In the particle size distribution obtained by laser diffraction scattering particle size distribution measurement method, D10 is the particle size with a cumulative frequency of 10% based on volume, and D100 is the particle size with a cumulative frequency of 100% based on volume.

[0072] (Lamination process S02)

[0073] Next, on one side of the ceramic substrate 11 (on Figure 5 The copper plate 42 (top) is laminated to form the circuit layer 12 via bonding material 45, and on the other side of the ceramic substrate 11 (on the top) Figure 5 The copper plate 43 (bottom) is formed into metal layer 13 by being laminated with bonding material 45.

[0074] (Pressure and heating process S03)

[0075] Next, while the copper plate 42, ceramic substrate 11 and copper plate 43 are under pressure, they are heated in a furnace under vacuum atmosphere to melt the bonding material 45.

[0076] Here, the heating temperature in the pressurization and heating process S03 is preferably in the range of 800°C or higher and 850°C or lower.

[0077] Furthermore, it is preferable that the product of the temperature integral value and the pressure load in the heating process from 780°C to the heating temperature and the holding process at the heating temperature is in the range of 0.3°C·h·MPa or more and 40°C·h·MPa or less. More preferably, the product of the temperature integral value and the pressure load is 0.6°C·h·MPa or more, and even more preferably 1.0°C·h·MPa or more. On the other hand, more preferably, the product of the temperature integral value and the pressure load is 20°C·h·MPa or less, and even more preferably 10°C·h·MPa or less.

[0078] Furthermore, the pressurization load in the pressurization and heating process S03 is preferably in the range of 0.029 MPa or more and 0.98 MPa or less.

[0079] Furthermore, the vacuum level in the pressurization and heating process S03 is preferably 1×10⁻⁶. -6 Pa or higher and 5×10 -2 Within the range below Pa.

[0080] (Cooling process S04)

[0081] Furthermore, after the pressurization and heating process S03, cooling is performed to solidify the molten bonding material 45, which will become the copper plate 42 of the circuit layer 12 and the ceramic substrate 11, and the ceramic substrate 11 and the copper plate 43 of the metal layer 13 are bonded together.

[0082] In this embodiment, the product R×P of the cooling rate R (°C / min) from the heating temperature to 780°C and the pressure load P (MPa) is preferably in the range of 0.15 ((°C / min)·MPa) or more and 15 ((°C / min)·MPa) or less.

[0083] Furthermore, the product R×P of the cooling rate R (°C / min) from the heating temperature to 780°C and the pressure load P (MPa) is more preferably 0.5 ((°C / min)·MPa) or more, and even more preferably 0.75 ((°C / min)·MPa) or more. On the other hand, the product R×P of the cooling rate R (°C / min) from the heating temperature to 780°C and the pressure load P (MPa) is more preferably 10 ((°C / min)·MPa) or less, and even more preferably 8 ((°C / min)·MPa) or less.

[0084] By adjusting the equivalent film thickness of Ag and the mass ratio of Ag to active metal (Ag / active metal) when coating the bonding material 45, and specifying the product of the temperature integral value and the pressure load in the pressurization and heating process S03 and the product of the cooling rate R (°C / min) from the heating temperature to 780°C and the pressure load P (MPa) in the cooling process S04 as described above, it is possible to control the flow of the liquid phase and adjust the area ratio of the Ag solid solution portions 12A and 13A.

[0085] As described above, the insulating circuit board 10 of this embodiment is manufactured by means of a bonding material preparation process S01, a lamination process S02, a pressurization and heating process S03, and a cooling process S04.

[0086] (Radiator joining process S05)

[0087] Next, the heat sink 5 is bonded to the other side of the metal layer 13 of the insulating circuit board 10.

[0088] The insulating circuit board 10 and the heat sink 5 are stacked with solder material and placed in a heating furnace. The insulating circuit board 10 and the heat sink 5 are soldered together through the solder layer 7.

[0089] (Semiconductor device bonding process S06)

[0090] Next, the semiconductor element 3 is bonded to one side of the circuit layer 12 of the insulating circuit board 10 by soldering.

[0091] Through the above processes, a product is manufactured. Figure 1 The power module 1 shown.

[0092] According to the insulating circuit board 10 (copper-ceramic bond) of this embodiment with the structure described above, since the area ratio of the Ag solid solution portions 12A and 13A with an Ag concentration of 0.5% by mass or more and 15% by mass or less in the end regions E of the circuit layer 12 and the metal layer 13 is 0.03 or more, even at the ends of the circuit layer 12 and the metal layer 13, Ag reacts sufficiently at the bonding interface with the ceramic substrate 11, and the ceramic substrate 11 can be firmly bonded to the circuit layer 12 and the metal layer 13.

[0093] Furthermore, since the area ratio of the Ag solid solution portions 12A and 13A is 0.35 or less, the end regions E of the circuit layer 12 and the metal layer 13 are prevented from becoming too hard due to solid solution curing, and cracks or peeling of the ceramic substrate 11 during thermal cycling are suppressed. Therefore, the reliability of thermal cycling can be significantly improved.

[0094] 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 to set the area ratio of the Ag solid solution portions 12A and 13A to 0.06 or more, and more preferably to 0.08 or more.

[0095] Furthermore, in order to prevent the end regions of the circuit layer 12 and the metal layer 13 from becoming too hard due to solid solution curing, it is preferable to set the area ratio of the Ag solid solution portions 12A and 13A to 0.27 or less, and more preferably to 0.20 or less.

[0096] Furthermore, in this embodiment, an active metal compound layer 21 is formed at the bonding interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13. When the thickness t1 of the active metal compound layer 21 is in the range of 0.05 μm or more and 0.8 μm or less, the ceramic substrate 11 is reliably and firmly bonded to the circuit layer 12 and the metal layer 13 through the active metal, and the hardening of the bonding interface is further suppressed.

[0097] In addition, in order to further improve the reliability of thermal cycling, it is preferable to set the thickness t1 of the active metal compound layer 21 to 0.08 μm or more, and more preferably to 0.15 μm or more.

[0098] Furthermore, in order to further suppress the bonding interface from becoming too hard, it is preferable to set the thickness t1 of the active metal compound layer 21 to 0.5 μm or less, and more preferably to 0.35 μm or less.

[0099] Furthermore, in this embodiment, an Ag-Cu alloy layer 22 is formed at the bonding interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13. When the thickness t2 of the Ag-Cu alloy layer 22 is in the range of 1 μm or more and 15 μm or less, the Ag of the bonding material reacts sufficiently with the circuit layer 12 and the metal layer 13, thereby reliably and firmly bonding the ceramic substrate 11 with the circuit layer 12 and the metal layer 13, and further suppressing the hardening of the bonding interface.

[0100] 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 to set the thickness t2 of the Ag-Cu alloy layer 22 to 3 μm or more, and more preferably to 5 μm or more.

[0101] Furthermore, in order to further suppress the bonding interface from becoming too hard, it is preferable to set the thickness t2 of the Ag-Cu alloy layer 22 to 13 μm or less, and more preferably to 11 μm or less.

[0102] The embodiments of the present invention have been described above, but the present invention is not limited thereto, and appropriate modifications can be made without departing from the technical concept of the present invention.

[0103] For example, in this embodiment, a power module is constructed by mounting semiconductor elements on an insulating circuit board, but it is not limited to this. For example, an LED module can be constructed by mounting LED elements on the circuit layer of the insulating circuit board, or a thermoelectric module can be constructed by mounting thermoelectric elements on the circuit layer of the insulating circuit board.

[0104] Furthermore, in the insulating circuit board of this embodiment, a ceramic substrate made of aluminum nitride (AlN) is used as an example for description, but it is not limited to this, and other ceramic substrates such as aluminum oxide (Al2O3) and silicon nitride (Si3N4) may also be used.

[0105] Furthermore, in this embodiment, Ti was described as an example of the active metal contained in the bonding material, but it is not limited to this; it is acceptable as long as it contains one or more active metals selected from Ti, Zr, Hf, and Nb. Additionally, these active metals may be contained in the form of hydrides.

[0106] Furthermore, in this embodiment, the circuit layer is formed by bonding a rolled sheet of oxygen-free copper to a ceramic substrate, but this is not a limitation. A circuit layer can also be formed by bonding copper sheets, formed from stamped copper plates, to a ceramic substrate in a circuit pattern configuration. In this case, each copper sheet only needs to have the interface structure with the ceramic substrate as described above.

[0107] Example

[0108] The results of the confirmation experiments conducted to verify the effectiveness of the present invention will be described below.

[0109] First, the ceramic substrates (40mm × 40mm) listed in Table 1 were prepared. Regarding thickness, the thickness was 0.635mm for AlN and Al2O3, and 0.32mm for Si3N4.

[0110] Furthermore, as the copper plate serving as the circuit layer and metal layer, a 37mm × 37mm copper plate made of oxygen-free copper with a thickness shown in Table 1 was prepared.

[0111] Furthermore, a bonding material is applied to the copper plate that serves as both the circuit layer and the metal layer. The bonding material is a paste-like material, and the amounts of Ag, Cu, and active metal are shown in Table 1. Here, as shown in Table 1, the equivalent film thickness of Ag and the mass ratio of Ag to active metal (Ag / active metal) were adjusted.

[0112] A copper plate, which will serve as the circuit layer, is stacked on one side of the ceramic substrate. Furthermore, a copper plate, which will serve as the metal layer, is stacked on the other side of the ceramic substrate.

[0113] The laminate was heated under pressure along the lamination direction to produce an Ag-Cu liquid phase. The product of the temperature integral and the pressure load is shown in Table 2.

[0114] Furthermore, the heated laminate was cooled to solidify the Ag-Cu liquid phase. At this point, the product of the cooling rate from the heating temperature to 780°C and the applied pressure load is shown in Table 2.

[0115] Through the above processes, the copper plate that will become the circuit layer, the ceramic substrate, and the metal plate that will become the metal layer are joined together to obtain an insulating circuit board (copper-ceramic bond).

[0116] Regarding the obtained insulating circuit board (copper-ceramic junction), the area ratio of the Ag solid solution in the end region, the active metal compound layer, the Ag-Cu alloy layer, and the thermal cycling reliability were evaluated in the following manner.

[0117] (Area ratio of the Ag solid solution in the end region)

[0118] EPMA analysis was performed on the interface between the circuit layer and the ceramic substrate, and the interface between the ceramic substrate and the metal layer. The total amount of Ag+Cu+active metal was set as 100% by mass, and the region with Ag concentration between 0.5% by mass and 15% by mass was set as the Ag solid solution.

[0119] Furthermore, the area ratio of the Ag solid solution in the end region of the circuit layer and the metal layer (the region with a width of 100 μm from the end of the circuit layer and the center of the circuit layer and the thickness t of the circuit layer and the metal layer is called the end region) is calculated.

[0120] (Active metal compound layer)

[0121] Using a scanning electron microscope (Carl Zeiss NTS ULTRA55, accelerating voltage 1.8kV), the cross-sections of the interface between the circuit layer and the ceramic substrate, and the interface between the ceramic substrate and the metal layer, were measured at 30,000x magnification. Elemental mappings of N, O, and active metal elements were obtained using energy-dispersive X-ray diffraction (EDD). The presence of an active metal compound layer was identified when an active metal element and N or O were present in the same region.

[0122] Observations were conducted in five fields of view (a total of ten fields of view). The average value obtained by dividing the area in which the active metal element and N or O coexist in the same region by the measured width was taken as the “thickness of the active metal compound layer” and recorded in Table 2.

[0123] (Ag-Cu alloy layer)

[0124] Using an EPMA apparatus, elemental mappings of Ag, Cu, and active metals were obtained at cross-sections of the interface between the circuit layer and the ceramic substrate, and at the interface between the ceramic substrate and the metal layer. Elemental mappings were obtained in five fields of view.

[0125] Furthermore, when Ag + Cu + active metal = 100% by mass, the area with an Ag concentration of 15% by mass or higher is designated as the Ag-Cu alloy layer. Its area is calculated, and the value obtained by dividing this area by the width of the measurement area (area / width of the measurement area) is calculated. The average value of this value is taken as the thickness of the Ag-Cu alloy layer and recorded in Table 2.

[0126] (Reliability of hot and cold cycles)

[0127] Depending on the material of the ceramic substrate, the aforementioned insulating circuit board was subjected to the following thermal cycles, and the presence of ceramic cracks was determined by SAT (ultrasonic testing). The evaluation results are shown in Table 2. The number of ceramic crack occurrences in Table 2 refers to the number of thermal cycles required until ceramic cracks occur.

[0128] For AlN and Al2O3: Set the load to -40℃×10 minutes and 150℃×10 minutes as one cycle, and perform SAT check every 50 cycles until 500 cycles are completed.

[0129] When using Si3N4: Set the load to -40℃×10 minutes and 150℃×10 minutes as 1 cycle, and perform SAT check every 200 cycles until 2000 cycles are completed.

[0130] [Table 1]

[0131]

[0132] [Table 2]

[0133]

[0134] First, Examples 1 to 3 of the present invention, which use AlN as a ceramic substrate, are compared with Comparative Examples 1 and 2.

[0135] In Comparative Example 1, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.023, and the number of cracks generated in the thermal cycling test was 50.

[0136] In Comparative Example 2, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.423, and the number of cracks generated in the thermal cycling test was 50.

[0137] In contrast, in Example 1 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.346, and the number of cracks generated in the thermal cycling test is 300.

[0138] In Example 2 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.063, and the number of cracks generated in the thermal cycling test is 350.

[0139] In Example 3 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.086, and the number of cracks generated in the thermal cycling test is 400.

[0140] As described above, compared with Comparative Examples 1 and 2, the thermal cycling reliability of Examples 1 to 3 of the present invention is excellent.

[0141] Next, Examples 4 to 6 of the present invention, which use Si3N4 as a ceramic substrate, are compared with Comparative Examples 3 and 4.

[0142] In Comparative Example 3, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.013, and the number of cracks generated in the thermal cycling test was 600.

[0143] In Comparative Example 4, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.400, and the number of crack initiation cycles in the thermal cycling test was 1200.

[0144] In contrast, in Example 4 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.031, and the number of cracks generated in the thermal cycling test is 1600.

[0145] In Example 5 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.211, and the number of cracks generated in the thermal cycling test is 1800.

[0146] In Example 6 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.125, and no cracks are generated even after 2000 cycles in the thermal cycling test.

[0147] As described above, compared with Comparative Examples 3 and 4, the thermal cycling reliability of Examples 4 to 6 of the present invention is excellent.

[0148] Next, Examples 7 and 8 of the present invention, which use Al2O3 as a ceramic substrate, are compared with Comparative Examples 5 and 6.

[0149] In Comparative Example 5, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.025, and the number of cracks generated in the thermal cycling test was 50.

[0150] In Comparative Example 6, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.370, and the number of crack initiation cycles in the thermal cycling test was 50.

[0151] In contrast, in Example 7 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) is 0.266, and the number of cracks generated in the thermal cycling test is 350.

[0152] In Example 8 of the present invention, the area ratio of the Ag solid solution in the end region of the circuit layer (metal layer) was 0.185, and the number of crack initiation cycles in the thermal cycling test was 400. As described above, compared with Comparative Examples 5 and 6, the thermal cycling reliability of Examples 7 and 8 of the present invention is excellent.

[0153] The results of the above confirmation experiments confirm that, according to the present invention, an insulating circuit board (copper-ceramic bonding material) can be provided that can suppress the generation of cracks in the ceramic substrate even under severe thermal cycling and has excellent thermal cycling reliability.

[0154] Industrial availability

[0155] According to the present invention, a copper-ceramic bonding material that can suppress the generation of cracks in ceramic components even under severe thermal cycling and has excellent thermal cycling reliability, and an insulating circuit board made of the copper-ceramic bonding material, can be provided.

[0156] Symbol Explanation

[0157] 10. Insulating circuit board (copper-ceramic bonding)

[0158] 11. Ceramic substrate (ceramic component)

[0159] 12 circuit layers (copper components)

[0160] 13 metal layers (copper components)

[0161] 12A, 13A Ag solid solution

[0162] 21 active metal compound layers

[0163] 22Ag-Cu alloy layer

Claims

1. A copper-ceramic joint, formed by joining a copper component made of copper or a copper alloy and a ceramic component, characterized in that, In the end region of the copper component, the area ratio of the Ag solid solution portion is in the range of 0.03 or higher and 0.35 or lower. The end region is a region with a width of 100 μm and a thickness t of the copper component, measured in cross-section along the stacking direction of the ceramic component, extending from the end of the copper component towards the center of the copper component. The thickness t is the distance from the surface of the ceramic component to the surface of the copper component facing the side opposite to the ceramic component. The Ag concentration in the Ag solid solution is 0.5% by mass or more and 15% by mass or less.

2. The copper-ceramic joint according to claim 1, characterized in that, At the interface between the ceramic component and the copper component, an active metal compound layer is formed on the side of the ceramic component. The thickness t1 of the active metal compound layer is in the range of 0.05 μm or more and 0.8 μm or less.

3. The copper-ceramic joint according to claim 1 or 2, characterized in that, At the interface between the ceramic component and the copper component, an Ag-Cu alloy layer is formed on the side of the copper component. The thickness t2 of the Ag-Cu alloy layer is in the range of more than 1 μm and less than 15 μm.

4. An insulating circuit board, formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate, characterized in that, In the end region of the copper plate, the area ratio of the Ag solid solution portion is in the range of 0.03 or higher and 0.35 or lower. The end region is a region with a width of 100 μm and a thickness t of the copper plate, measured in cross-section along the stacking direction of the ceramic substrate, extending from the end of the copper plate towards the center of the copper plate. The thickness t is the distance from the surface of the ceramic substrate to the surface of the copper plate facing the side opposite to the ceramic substrate. The Ag concentration in the Ag solid solution is 0.5% by mass or more and 15% by mass or less.

5. The insulating circuit board according to claim 4, characterized in that, At the interface between the ceramic substrate and the copper plate, an active metal compound layer is formed on the ceramic substrate side. The thickness t1 of the active metal compound layer is in the range of 0.05 μm or more and 0.8 μm or less.

6. The insulating circuit board according to claim 4 or 5, characterized in that, At the interface between the ceramic substrate and the copper plate, an Ag-Cu alloy layer is formed on the side of the copper plate, and the thickness t2 of the Ag-Cu alloy layer is in the range of more than 1 μm and less than 15 μm.

Images