JP2023013627A - Copper/Ceramic Bonded Body and Insulated Circuit Board - Google Patents

Abstract

The present invention provides a copper/ceramic joined body that can suppress the occurrence of cracks in a ceramic member even when subjected to a severe cooling/heating cycle and has excellent cooling/heating cycle reliability. A copper/ceramic joined body (10) in which copper members (12, 13) made of copper or a copper alloy and a ceramic member (11) are joined together, and a joint interface between the ceramic member (11) and the copper members (12, 13) is provided. An active metal compound layer 21 is formed on the ceramic member 11 side, and an active metal diffusion region 23 is formed on the ceramic member 11 side of the copper members 12 and 13. and the maximum reachable distance LB of the active metal diffusion region 23B from the active metal compound layer 21B in the central region B are within a range of 20 μm or more and 80 μm or less, and the maximum reachable distance A difference between LA and the maximum reaching distance LB is 10 μm or less. [Selection drawing] Fig. 2

Description

The present invention provides a copper/ceramic bonded body in which a copper member made of copper or a copper alloy and a ceramic member are joined together, and an insulating circuit in which a copper plate made of copper or a copper alloy is joined to the surface of a ceramic substrate. It relates to substrates.

A power module, an LED module, and a thermoelectric module have a structure in which a power semiconductor element, an LED element, and a thermoelectric element are joined to an insulating circuit board in which a circuit layer made of a conductive material is formed on one side of an insulating layer. .
For example, power semiconductor elements for high power control used to control wind power generation, electric vehicles, hybrid vehicles, etc. generate a large amount of heat during operation. A circuit layer formed by bonding a metal plate having 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. Insulated circuit boards have been widely used in the past.

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 this patent document 1, copper plates are arranged on one surface and the other surface of a ceramic substrate with an Ag—Cu—Ti brazing material interposed therebetween, and the copper plates are joined by heat treatment (so-called active metal brazing method).

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 Al ₂ O ₃ are bonded using a bonding material containing Ag and Ti. ing.
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 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, thereby improving the wettability of the bonding material and the copper plate. The bonding strength with the ceramic substrate is improved.

Japanese Patent No. 3211856 Japanese Patent No. 5757359 JP 2018-008869 A

By the way, recently, the heat generation temperature of the semiconductor elements mounted on the insulated circuit board tends to be higher, and the insulated circuit board is required to have higher cooling/heating cycle reliability to withstand severe cooling/heating cycles. It is
Here, 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, diffuses into the copper plate side, and an intermetallic compound containing Cu and Ti precipitates. As a result, the vicinity of the joint interface becomes hard, cracks may occur in the ceramic member during thermal cycle loading, and there is a risk of deterioration in thermal cycle reliability.

The present invention has been made in view of the above-mentioned circumstances. It is an object of the present invention to provide an insulated circuit board made of this copper/ceramic bonded body.

In order to solve the above-mentioned problems, the inventors of the present invention conducted intensive studies and found that when a ceramic member and a copper member are joined using a joining material containing an active metal, the liquid phase generated at the time of joining is a liquid phase in the copper member. The active metal is repelled from the central portion to the peripheral edge portion side, and a relatively large amount of active metal exists in the peripheral edge portion of the copper member. It was found that there is a tendency to be harder than the region. Then, the inventors have found that stress concentrates on the peripheral edge region of the hard copper member at the bonding interface during a thermal cycle load, and cracks are likely to occur in the ceramic member.

The present invention has been made based on the above findings, and the copper/ceramic joined body of the present invention is a copper/ceramic joined body in which a copper member made of copper or a copper alloy and a ceramic member are joined. At the joint interface between the ceramic member and the copper member, an active metal compound layer is formed on the ceramic member side, and the active metal (Ti, Zr, Nb, Hf) are diffused from the ceramic member side to the copper member side to form an active metal diffusion region in which the concentration of the active metal in the copper member is 0.5% by mass or more. said maximum reaching distance _LA from said active metal compound layer of said active metal diffusion region in a peripheral region of said copper member and from said active metal compound layer of said active metal diffusion region in a central region of said copper member; of the active metal diffusion region in the peripheral edge region of the copper member, and the maximum reach length _{L B in} the central region of the copper member The difference from the maximum reaching distance _LB of the active metal diffusion region is 10 μm or less.

According to the copper/ceramic joined body of the present invention, the maximum reaching distance L _A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper member and the active distance L A in the central region of the copper member Since the maximum reachable distance L _B of the metal diffusion region from the active metal compound layer is in the range of 20 μm or more and 80 μm or less, the ceramic member and the copper member are firmly joined by the active metal, and the joining is performed. Hardening of the interface is suppressed.
The difference between the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper member and the maximum reaching distance L _B of the active metal diffusion region in the central region of the copper member is 10 μm or less. Therefore, it is possible to suppress the peripheral region of the copper member from becoming relatively hard at the joint interface, suppress the occurrence of cracks in the ceramic member under thermal cycle load, and have excellent thermal cycle reliability. .

Here, in the copper/ceramic bonded body of the present invention, the thickness _t1A of the active metal compound layer formed in the peripheral region of the copper member and the active metal layer formed in the central region of the copper member It is preferable that the thickness _t1B of the compound layer is in the range of 0.05 μm or more and 1.2 μm or less, and the thickness ratio _t1A / _t1B is in the range of 0.7 or more and 1.4 or less.
In this case, the thickness _t1A of the active metal compound layer formed in the peripheral region of the copper member and the thickness _t1B of the active metal compound layer formed in the central region of the copper member are 0.05 μm. Since the thickness is within the range of 1.2 μm or less, the ceramic member and the copper member are reliably and strongly bonded by the active metal, and hardening of the bonding interface is further suppressed.
Further, since the thickness ratio _t1A / _t1B is within the range of 0.7 or more and 1.4 or less, there is a large difference in the hardness of the bonding interface between the peripheral region and the central region of the copper member. Therefore, it is possible to further suppress the occurrence of cracks in the ceramic member under thermal cycle load.

Further, in the copper/ceramic joined body of the present invention, an Ag—Cu alloy layer is formed on the side of the copper member at the joint interface between the ceramic member and the copper member, and the peripheral edge region of the copper member The thickness t2 _A of the Ag—Cu alloy layer formed in the central region of the copper member and the thickness t2 _B of the Ag—Cu alloy layer formed in the central region of the copper member are in the range of 1 μm or more and 30 μm or less, and the thickness It is preferable that the thickness ratio _t2A / _t2B is in the range of 0.7 or more and 1.4 or less.
In this case, the thickness _t2A of the Ag--Cu alloy layer formed in the peripheral region of the copper member and the thickness _t2B of the Ag--Cu alloy layer formed in the central region of the copper member are 1 μm. Since the thickness is within the range of 30 μm or less, the Ag of the bonding material sufficiently reacts with the copper member, so that the ceramic member and the copper member are reliably and firmly bonded, and the bonding interface is further hardened. Suppressed.
Since the thickness ratio _t2A / _t2B is in the range of 0.7 or more and 1.4 or less, there is a large difference in the hardness of the bonding interface between the peripheral region and the central region of the copper member. is not generated, and the occurrence of cracks in the ceramic member under thermal cycle load can be further suppressed.

The insulating circuit board of the present invention is an insulating circuit board in which a copper plate made of copper or a copper alloy is bonded to the surface of a ceramic substrate, and the bonding interface between the ceramic substrate and the copper plate includes: is formed with an active metal compound layer, and active metals (Ti, Zr, Nb, Hf) are diffused from the ceramic substrate side to the copper plate side on the ceramic substrate side of the copper plate. An active metal diffusion region is formed in which the concentration of the active metal in the copper plate is 0.5% by mass or more, and the maximum reach of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate is The distance L _A and the maximum reachable distance L _B of the active metal diffusion region from the active metal compound layer in the central region of the copper plate are in the range of 20 μm or more and 80 μm or less, and in the peripheral region of the copper plate _A difference between the maximum reaching distance LA of the active metal diffusion region and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate is 10 μm or less.

According to the insulated circuit board of the present invention, the maximum reaching distance _LA of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate and the distance of the active metal diffusion region in the central region of the copper plate Since the maximum reachable distance _LB from the active metal compound layer is in the range of 20 μm or more and 80 μm or less, the ceramic substrate and the copper plate are firmly bonded by the active metal, and the bonding interface becomes hard. is suppressed.
The difference between the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper plate and the maximum reaching distance L _B of the active metal diffusion region in the central region of the copper plate is 10 μm or less. Therefore, it is possible to suppress the peripheral region of the copper plate from becoming relatively hard at the joint interface, suppress the occurrence of cracks in the ceramic substrate under thermal cycle loads, and have excellent thermal cycle reliability.

Here, in the insulated circuit board of the present invention, the thickness _t1A of the active metal compound layer formed in the peripheral region of the copper plate and the thickness of the active metal compound layer formed in the central region of the copper plate Preferably, the thickness _t1B is in the range of 0.05 μm or more and 1.2 μm or less, and the thickness ratio _t1A / _t1B is in the range of 0.7 or more and 1.4 or less.
In this case, the thickness _t1A of the active metal compound layer formed in the peripheral region of the copper plate and the thickness _t1B of the active metal compound layer formed in the central region of the copper plate are 0.05 μm or more. Since the thickness is within the range of 0.2 μm or less, the ceramic substrate and the copper plate are reliably and strongly bonded by the active metal, and hardening of the bonding interface is further suppressed.
Further, since the thickness ratio _t1A / _t1B is within the range of 0.7 or more and 1.4 or less, there is a large difference in the hardness of the bonding interface between the peripheral region and the central region of the copper plate. Moreover, it is possible to further suppress the occurrence of cracks in the ceramic substrate under thermal cycle load.

Further, in the insulated circuit board of the present invention, an Ag—Cu alloy layer is formed on the side of the copper plate at the bonding interface between the ceramic substrate and the copper plate, and the Ag—Cu alloy layer is formed on the peripheral edge region of the copper plate. The thickness t2 _A of the Ag--Cu alloy layer and the thickness t2 _B of the Ag--Cu alloy layer formed in the central region of the copper plate are in the range of 1 μm or more and 30 μm or less, and the thickness ratio t2 _A /t2 _B is preferably in the range of 0.7 or more and 1.4 or less.
In this case, the thickness _t2A of the Ag--Cu alloy layer formed in the peripheral region of the copper plate and the thickness _t2B of the Ag--Cu alloy layer formed in the central region of the copper plate are 1 μm or more and 30 μm. Since it is within the following range, the Ag of the bonding material sufficiently reacts with the copper plate, and the ceramic substrate and the copper plate are reliably and strongly bonded, and hardening of the bonding interface is further suppressed.
Since the thickness ratio _t2A / _t2B is in the range of 0.7 or more and 1.4 or less, there is a large difference in the hardness of the bonding interface between the peripheral region and the central region of the copper plate. In addition, it is possible to further suppress the occurrence of cracks in the ceramic substrate under a thermal cycle load.

According to the present invention, even when a severe thermal cycle is applied, the occurrence of cracks in the ceramic member can be suppressed, and the copper / ceramics joined body has excellent thermal cycle reliability, and the copper / ceramics joined body It is possible to provide an insulated circuit board that is

1 is a schematic explanatory diagram of a power module using an insulated circuit board according to an embodiment of the present invention; FIG. FIG. 2 is an enlarged explanatory view of a bonding interface between a circuit layer and a metal layer of an insulated circuit board and a ceramic substrate according to an embodiment of the present invention; (a) is an explanatory diagram of the peripheral region and the central region of the circuit layer and the metal layer, (b) is the peripheral region, and (c) is the central region. 1 is a flowchart of a method for manufacturing an insulated circuit board according to an embodiment of the present invention; FIG. It is a schematic explanatory drawing of the manufacturing method of the insulation circuit board which concerns on embodiment of this invention. FIG. 4 is an explanatory diagram of a bonding material disposing step in the method of manufacturing an insulated circuit board according to the embodiment of the present invention;

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The copper/ceramic bonded body according to the present embodiment includes a ceramic substrate 11 as a ceramic member made of ceramics, and 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. is an insulating circuit board 10 formed by bonding the . FIG. 1 shows a power module 1 having an insulated circuit board 10 according to this embodiment.

This power module 1 includes an insulating circuit board 10 on which a circuit layer 12 and a metal layer 13 are arranged, and a semiconductor element 3 bonded to one surface (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 (lower side in FIG. 1) of the metal layer 13 .

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

The heat sink 5 is for dissipating heat from the insulating circuit board 10 described above. The heat sink 5 is made of copper or a copper alloy, and is made of phosphorus-deoxidized copper in this embodiment. The heat sink 5 is provided with a channel through which cooling fluid flows.
In addition, in this embodiment, the heat sink 5 and the metal layer 13 are joined by a solder layer 7 made of a solder material. The solder layer 7 is made of, for example, a Sn--Ag-based, Sn--In-based, or Sn--Ag--Cu-based solder material.

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

The ceramics substrate 11 is made of ceramics such as silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), alumina (Al ₂ O ₃ ), etc., which are excellent in insulation and heat dissipation. In this embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN), which has excellent heat dissipation properties. The thickness of the ceramic substrate 11 is set within a range of, for example, 0.2 mm or more and 1.5 mm or less, and is set to 0.635 mm in this embodiment.

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 (upper surface in FIG. 4) of the ceramic substrate 11. As shown in FIG.
In this embodiment, the circuit layer 12 is formed by bonding a rolled plate of oxygen-free copper to the ceramic substrate 11 .
The thickness of the copper plate 42 that forms the circuit layer 12 is set within a range of 0.1 mm or more and 2.0 mm or less, and is set to 0.6 mm in this embodiment.

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

Here, as shown in FIG. 2, an active metal compound layer 21 and an Ag—Cu alloy layer 22 are formed in order from the ceramic substrate 11 side at the bonding interface between the ceramic substrate 11, the circuit layer 12 and the metal layer 13. ing.
In the circuit layer 12 and the metal layer 13, the active metal (Ti in this embodiment) diffuses toward the circuit layer 12 and the metal layer 13 on the side of the bonding interface with the ceramic substrate 11, thereby forming a circuit. An active metal diffusion region 23 is formed in which the active metal concentration in the layer 12 and the metal layer 13 is 0.5 mass % or more.

In the insulated circuit board 10 of the present embodiment, as shown in FIG. 2, the interface structure between the peripheral region A and the central region B of the circuit layer 12 and the metal layer 13 is defined as follows. there is
In this embodiment, as shown in FIG. 2A, the peripheral region A of the circuit layer 12 and the metal layer 13 is a cross section along the lamination direction of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11. 2, the region extends from the widthwise end of the circuit layer 12 and the metal layer 13 to 200 μm further inward in the width direction from a position 20 μm inward from the widthwise end.
In addition, as shown in FIG. 2(a), the central region B of the circuit layer 12 and the metal layer 13 is the circuit layer 12 in the cross section along the lamination direction of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11. and a region of 200 μm in the width direction including the center of the metal layer 13 in the width direction.

Here, as shown in FIG. 2(b), in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13, the maximum reaching distance LA of the active metal diffusion region 23A from the active metal compound layer _21A is in the range of 20 μm or more and 80 μm or less.
Further, as shown in FIG. 2(c), in the central region B of the bonding interface between the circuit layer 12 and the metal layer 13, the maximum reaching distance L _B of the active metal diffusion region 23B from the active metal compound layer 21B is , 20 μm or more and 80 μm or less.

In the present embodiment, the maximum reaching distance L _A of the active metal diffusion region 23A in the peripheral edge region A of the bonding interface between the circuit layer 12 and the metal layer 13 and the bonding interface between the circuit layer 12 and the metal layer 13 The difference from the maximum reaching distance LB of the active metal diffusion region 23B in the central region _B is 10 μm or less.

In addition, in the present embodiment, the thickness t1 A of the active metal compound layer 21A formed in the peripheral region A of the bonding interface between the circuit layer 12 and the metal layer 13 and the thickness t1 _A of the active metal compound layer 21A and the thickness The thickness t1B of the active metal compound layer 21B formed in the central region _B of the bonding interface is in the range of 0.05 μm or more and 1.2 μm or less, and the thickness ratio _t1A / _t1B is 0.05 μm or more and 1.2 μm or less. It is preferably within the range of 7 or more and 1.4 or less.
Here, the active metal compound layers 21 ( 21 A, 21 B) are layers made of compounds of active metals (Ti, Zr, Nb, Hf) used in the bonding material 45 . More specifically, when the ceramic substrate is made of silicon nitride (Si ₃ N ₄ ) or aluminum nitride (AlN), the layer becomes a nitride of these active metals, and the ceramic substrate is made of alumina (Al ₂ O ₃ ), the layer consists of oxides of these active metals. The active metal compound layers 21 (21A, 21B) are formed by aggregating active metal compound particles. The average particle size of these particles is 10 nm or more and 100 nm or less.
In this embodiment, since the bonding material 45 contains Ti as an active metal and the ceramic substrate 11 is made of aluminum nitride, the active metal compound layers 21 (21A, 21B) are made of titanium nitride (TiN). Configured. That is, the active metal compound layers 21 (21A, 21B) are formed by aggregation of particles of titanium nitride (TiN) having an average particle diameter of 10 nm or more and 100 nm or less.

Furthermore, in the present embodiment, the thickness t2A of the Ag—Cu alloy layer 22A formed in the peripheral region _A of the bonding interface between the circuit layer 12 and the metal layer 13 and the thickness t2A between the circuit layer 12 and the metal layer 13 The ratio _t2A / _t2B to the thickness t2B of the Ag—Cu alloy layer 22B formed in the central region _B of the joint interface is preferably within the range of 0.7 or more and 1.4 or less. .
Further, the thickness of the Ag--Cu alloy layers 22 (22A, 22B) is preferably 1 μm or more and 30 μm or less.

A method for manufacturing the insulating circuit board 10 according to the present embodiment will be described below with reference to FIGS. 3 and 4. FIG.

(Bonding Material Arranging Step S01)
A copper plate 42 to be the circuit layer 12 and a copper plate 43 to be the metal layer 13 are prepared.
Then, a bonding material 45 is applied to the bonding surfaces of the copper plate 42 to be the circuit layer 12 and the copper plate 43 to be the metal layer 13 and dried. The coating thickness of the paste-like bonding material 45 is preferably within the range of 10 μm or more and 50 μm or less after drying.
In this embodiment, the paste bonding material 45 is applied by screen printing.

The bonding material 45 contains Ag and active metals (Ti, Zr, Nb, Hf). In this embodiment, as the bonding material 45, an Ag--Ti based brazing material (Ag--Cu--Ti based brazing material) is used. The Ag--Ti-based brazing material (Ag--Cu--Ti-based brazing material) contains, for example, 0% by mass or more and 45% by mass or less of Cu, and 0.5% by mass or more and 20% by mass of Ti, which is an active metal. It is preferable to use a composition having a content in the range of mass % or less, with the balance being Ag and unavoidable impurities.

The specific surface area of Ag powder contained in the bonding material 45 is preferably 0.15 m ² /g or more, more preferably 0.25 m ² /g or more, and more preferably 0.40 m ² /g or more. is more preferred. On the other hand, the specific surface area of the Ag powder contained in the bonding material 45 is preferably 1.40 m ² /g or less, more preferably 1.00 m ² /g or less, and 0.75 m ² /g or less. is more preferable.
The particle size of the Ag powder contained in the paste-like bonding material 45 preferably has a D10 of 0.7 μm or more and 3.5 μm or less and a D100 of 4.5 μm or more and 23 μm or less.

Here, in the pressing and heating step S03 to be described later, by applying pressure in the stacking direction, the generated liquid phase is expelled from the central portion of the copper plates 42 and 43 to the peripheral portion side, and the peripheral portions of the copper plates 42 and 43 are activated. A relatively large amount of metal components will be present.
Therefore, in this embodiment, as shown in FIG. The bonding material 45 is applied so as to be thinner than the coating thickness of the bonding material 45B in the central portion of the copper plate 43 that becomes the metal layer 13 .
Note that the difference between the coating thickness of the bonding material 45A in the peripheral edge portion of the copper plate 42 serving as the circuit layer 12 and the copper plate 43 serving as the metal layer 13 and the coating thickness of the bonding material 45B in the central portion is in the range of 5 μm or more and 15 μm or less. It is preferable to

(Lamination step S02)
Next, a copper plate 42 to be the circuit layer 12 is laminated on one surface (upper surface in FIG. 4) of the ceramic substrate 11 with a bonding material 45 interposed therebetween, and on the other surface (lower surface in FIG. 4) of the ceramic substrate 11 , a copper plate 43 to be the metal layer 13 is laminated with a bonding material 45 interposed therebetween.

(Pressure and heating step S03)
Next, the copper plate 42, the ceramic substrate 11, and the copper plate 43 are heated in a heating furnace in a vacuum atmosphere to melt the bonding material 45 while being pressurized.
Here, the heating temperature in the pressurizing and heating step S03 is preferably in the range of 800° C. or higher and 850° C. or lower. The total temperature integral value in the heating step from 780° C. to the heating temperature and the holding step at the heating temperature is preferably within the range of 7° C.·h or more and 80° C.·h or less.
Moreover, the pressure load in the pressurization and heating step S03 is preferably within the range of 0.029 MPa or more and 2.94 MPa or less.
Further, the degree of vacuum in the pressurizing and heating step S03 is preferably in the range of 1×10 ⁻⁶ Pa or more and 5×10 ⁻² Pa or less.

(Cooling step S04)
After the pressurizing and heating step S03, the molten bonding material 45 is cooled to solidify, and the copper plate 42 and the ceramics substrate 11 to be the circuit layer 12, and the ceramics substrate 11 and the copper plate 43 to be the metal layer 13 are formed. Join with.
The cooling rate in this cooling step S04 is preferably within the range of 2° C./min or more and 20° C./min or less. The cooling rate here is the cooling rate from the heating temperature to 780° C., which is the Ag—Cu eutectic temperature.

As described above, the insulated circuit board 10 of the present embodiment is manufactured through the bonding material disposing step S01, the laminating step S02, the pressurizing and heating step S03, and the cooling step S04.

(Heat-sink bonding step S05)
Next, the heat sink 5 is bonded to the other side of the metal layer 13 of the insulated circuit board 10 .
The insulating circuit board 10 and the heat sink 5 are laminated with a solder material interposed therebetween and placed in a heating furnace.

(Semiconductor element bonding step S06)
Next, the semiconductor element 3 is soldered to one surface of the circuit layer 12 of the insulating circuit board 10 .
The power module 1 shown in FIG. 1 is produced by the above-described steps.

According to the insulating circuit board 10 (copper/ceramic bonded body) of the present embodiment configured as described above, the active metal compound layer of the active metal diffusion region 23A in the peripheral region A of the circuit layer 12 and the metal layer 13 The maximum reaching distance L _A from 21A and the maximum reaching distance L _B of the active metal diffusion region 23B in the central region B of the circuit layer 12 and the metal layer 13 from the active metal compound layer 21B are within a range of 20 μm or more and 80 μm or less. Therefore, the ceramic substrate 11, the circuit layer 12, and the metal layer 13 are strongly bonded by the active metal, and hardening of the bonded interface is suppressed.

In order to bond the ceramic substrate 11, the circuit layer 12 and the metal layer 13 more firmly, the maximum thickness of the active metal compound layers 21 (21A, 21B) in the active metal diffusion regions 23 (23A, 23B) is increased. The reaching distances L _A and L _B are preferably 25 μm or more, more preferably 35 μm or more.
Further, in order to further suppress the bonding interface from becoming unnecessarily hard, the maximum reaching distance L _A of the active metal diffusion regions 23 (23A, 23B) from the active metal compound layers 21 (21A, 21B), _LB is preferably 75 μm or less, more preferably 65 μm or less.

The maximum reaching distance LA of the active metal diffusion region 23A in the peripheral region _A of the circuit layer 12 and the metal layer 13 and the maximum reaching distance of the active metal diffusion region 23B in the central region B of the circuit layer 12 and the metal layer 13 Since the difference from LB is set to 10 μm or less, it is possible to suppress the peripheral edge region _A of the circuit layer 12 and the metal layer 13 from becoming relatively hard at the bonding interface, and the ceramic substrate 11 under thermal cycle load. Cracking can be suppressed, and the thermal cycle reliability is excellent.
In order to further improve the thermal cycle reliability, the maximum reaching distance L _A of the active metal diffusion region 23A in the peripheral region A of the circuit layer 12 and the metal layer 13 and the central portion of the circuit layer 12 and the metal layer 13 The difference from the maximum reaching distance LB of the active metal diffusion region 23B in the region _B is preferably 8 μm or less, more preferably 6 μm or less.

In addition, in the present embodiment, the thickness t1 _A of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 and the thickness t1A formed in the central region B of the circuit layer 12 and the metal layer 13 When the thickness _t1B of the applied active metal compound layer 21B is in the range of 0.05 μm or more and 1.2 μm or less, the ceramic substrate 11, the circuit layer 12 and the metal layer 13 are reliably bonded by the active metal. In addition, hardening of the bonding interface is further suppressed.

In order to bond the ceramic substrate 11, the circuit layer 12 and the metal layer 13 more firmly, the thickness t1 of the active metal compound layer 21A formed in the peripheral region _A of the circuit layer 12 and the metal layer 13 , and the thickness t1B of the active metal compound layer 21B formed in the central region _B of the circuit layer 12 and the metal layer 13 is preferably 0.08 μm or more, more preferably 0.15 μm or more. preferable.
Further, in order to further suppress the bonding interface from becoming harder than necessary, the thickness t1 A of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 and the thickness t1 _A of the circuit layer 12 and the thickness t1B of the active metal compound layer 21B formed in the central region _B of the metal layer 13 is preferably 1.0 μm or less, more preferably 0.6 μm or less.

Furthermore, in the present embodiment, the thickness t1 A of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 and the thickness t1 _A formed in the central region B of the circuit layer 12 and the metal layer 13 When the ratio _t1A / _t1B of the thickness _t1B of the active metal compound layer 21B is in the range of 0.7 or more and 1.4 or less, the peripheral edge portions of the circuit layer 12 and the metal layer 13 There is no large difference in the hardness of the bonding interface between the region A and the central region B, and cracking of the ceramic substrate 11 under thermal cycle load can be further suppressed.

In order to further suppress the occurrence of cracks in the ceramic substrate 11 under thermal cycle load, the thickness t1 _A of the active metal compound layer 21A formed in the peripheral region A of the circuit layer 12 and the metal layer 13, and , the ratio _t1A / _t1B of the thickness t1B of the active metal compound layer 21B formed in the central region _B of the circuit layer 12 and the metal layer 13 is in the range of 0.8 or more and 1.2 or less. is more preferable, and more preferably within the range of 0.9 or more and 1.1 or less.

Further, in the present embodiment, the thickness t2 A of the Ag—Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13, and the thickness t2 _A of the central region B of the circuit layer 12 and the metal layer 13 When the thickness _t2B of the formed Ag—Cu alloy layer 22B is in the range of 1 μm or more and 30 μm or less, the Ag of the bonding material 45, which will be described later, and the circuit layer 12 and the metal layer 13 are sufficiently As a result, the ceramic substrate 11, the circuit layer 12 and the metal layer 13 are reliably and strongly bonded together, and hardening of the bonding interface is further suppressed.

In order to bond the ceramic substrate 11, the circuit layer 12 and the metal layer 13 more firmly, the thickness t2 _A and the thickness t2B of the Ag—Cu alloy layer 22B formed in the central region _B of the circuit layer 12 and the metal layer 13 are preferably 3 μm or more, more preferably 5 μm or more.
Further, in order to further suppress the joining interface from becoming harder than necessary, the thickness t2 _A of the Ag—Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 and the circuit The thickness t2B of the Ag—Cu alloy layer 22B formed in the central region _B of the layer 12 and the metal layer 13 is preferably 25 μm or less, more preferably 15 μm or less.

Furthermore, in the present embodiment, the thickness t2A of the Ag—Cu alloy layer 22A formed in the peripheral region _A of the circuit layer 12 and the metal layer 13 and the thickness t2A formed in the central region B of the circuit layer 12 and the metal layer 13 When the ratio _t2A / _t2B to the thickness _t2B of the Ag--Cu alloy layer 22B is within the range of 0.7 or more and 1.4 or less, the circuit layer 12 and the metal layer 13 There is no large difference in the hardness of the joint interface between the peripheral edge region A and the central region B, and cracking of the ceramic substrate under thermal cycle load can be further suppressed.

In order to further suppress the occurrence of cracks in the ceramic substrate 11 under thermal cycle load, the Ag—Cu alloy layer 22A formed in the peripheral region A of the circuit layer 12 and the metal layer 13 has a thickness t2 _A and , the ratio _t2A / _t2B of the thickness t2B of the Ag—Cu alloy layer 22B formed in the central region _B of the circuit layer 12 and the metal layer 13 is within the range of 0.8 or more and 1.2 or less. It is more preferable to make it within the range of 0.9 or more and 1.1 or less.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical idea of the invention.
For example, in the present embodiment, a power module is configured by mounting a semiconductor element on an insulated 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 the circuit layer of the insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on the circuit layer of the insulating circuit board.

In addition, in the insulating circuit board of the present embodiment _, the ceramic substrate is made of aluminum nitride ₍ AlN). , other ceramic substrates such as silicon nitride (Si ₃ N ₄ ) may be used.

Furthermore, in the present embodiment, Ti was used as an example of the active metal contained in the bonding material. It suffices if it contains the above active metals. These active metals may be contained as hydrides.

Further, in the present embodiment, by adjusting the coating thickness of the bonding material in the peripheral portion and the central portion of the copper plate, the maximum reaching distance L _A of the active metal diffusion region in the peripheral portion region of the circuit layer and the metal layer and the circuit Although described as controlling the maximum reach L _B of the active metal diffusion region in the central region of the layer and metal layer, but not limited to this, the bonding material to be applied at the periphery and center of the copper plate are different to control the maximum reach L _A of the active metal diffusion region in the peripheral region of the circuit layer and the metal layer and the maximum reach L _B of the active metal diffusion region in the central region of the circuit layer and the metal layer. may

For example, by adjusting the specific surface area (BET value) of Ag powder contained in the bonding material, it is possible to control the aforementioned maximum reaching distance. That is, when the specific surface area of the Ag powder is small, the sinterability of the paste-like bonding material becomes high, the liquid phase is likely to occur in the pressurization and heating process, the diffusion of the active metal is promoted, and the maximum reach distance described above is increased. becomes longer. On the other hand, when the specific surface area of the Ag powder is large, the sinterability of the paste-like bonding material becomes low, making it difficult to generate a liquid phase in the pressurization and heating processes, suppressing the diffusion of the active metal, and increasing the maximum reach distance described above. becomes shorter.
Alternatively, bonding materials containing different types and amounts of active metals may be used to separately paint the peripheral edge portion and the central portion of the copper plate.

Furthermore, in the present embodiment, the circuit layer was described as being formed by bonding a rolled plate of oxygen-free copper to a ceramic substrate, but the present invention is not limited to this, and a copper piece punched out of a copper plate is used. A circuit layer may be formed by bonding to a ceramic substrate while being arranged in a circuit pattern. In this case, each copper piece should have the interface structure with the ceramic substrate as described above.
Further, in the present embodiment, the bonding material is provided on the bonding surface of the copper plate, but the present invention is not limited to this, and the bonding material may be provided between the ceramic substrate and the copper plate. Alternatively, a bonding material may be provided on the bonding surface of the ceramic substrate.

The results of confirmatory experiments conducted to confirm the effects of the present invention will be described below.

First, a ceramic substrate (40 mm×40 mm) shown in Table 1 was prepared. The thickness of AlN and Al ₂ O ₃ was 0.635 mm, and the thickness of Si ₃ N ₄ was 0.32 mm.
In addition, a copper plate made of oxygen-free copper and having a thickness of 37 mm×37 mm and having a thickness shown in Table 1 was prepared as a copper plate serving as a circuit layer and a metal layer.

A bonding material containing Ag powder having a BET value shown in Table 1 was applied to the peripheral portion of the copper plate serving as the circuit layer and the metal layer so that the target thickness after drying would be the value shown in Table 1.
In addition, a bonding material containing Ag powder having a BET value shown in Table 1 was applied to the central portion of the copper plate serving as the circuit layer and the metal layer so that the target thickness after drying would be the value shown in Table 1.
A paste material was used as the bonding material, and the amounts of Ag, Cu, and active metal were as shown in Table 1.
In addition, the BET value (specific surface area) of the Ag powder was measured by using AUTOSORB-1 manufactured by QUANTACHRROME, vacuum deaeration by heating at 150 ° C. for 30 minutes as pretreatment, N ₂ adsorption, liquid nitrogen 77 K, BET multipoint method. It was measured.

A copper plate serving as a circuit layer was laminated on one surface of the ceramic substrate. A copper plate serving as a metal layer was laminated on the other surface of the ceramic substrate.

This laminate was heated while being pressed in the lamination direction to generate an Ag—Cu liquid phase. At this time, the pressure load was set to 0.294 MPa, and the temperature integral value was set as shown in Table 2.
Then, by cooling the heated laminate, the copper plate serving as the circuit layer, the ceramic substrate, and the metal plate serving as the metal layer were bonded to obtain an insulated circuit substrate (copper/ceramic bonded body).

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

(maximum reaching distance of active metal diffusion region)
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 were observed with an EPMA device, and an elemental map (width 200 μm × height 200 μm) was obtained for active metals in the circuit layer and the metal layer. ) were acquired in 5 fields each.
Then, the maximum reaching distance from the active metal compound layer of the active metal diffusion region having an active metal concentration of 0.5% by mass or more was measured. In addition, the concentration of the active metal is a value in which the sum of the respective concentrations of Ag, Cu, and active metal is 100% by mass. Table 2 lists the maximum reachable distance among the maximum reachable distances in each of the 5 fields of view and a total of 10 fields of view.

(Active metal compound layer)
A 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 examined using a scanning electron microscope (ULTRA55 manufactured by Carl Zeiss NTS, acceleration voltage 1.8 kV) at a magnification of 30,000. Measured, and elemental mapping of N, O and active metal elements was obtained for each of 5 fields by the energy dispersive X-ray analysis method. It was determined that there was an active metal compound layer when the active metal element and N or O were present in the same region.
Observations were made in 5 fields of view, totaling 10 fields of view, and the average value obtained by dividing the area of the range in which the active metal element and N or O existed in the same region by the measured width was expressed as the "thickness of the active metal compound layer." 2.

(Ag—Cu alloy layer)
Elemental mapping of Ag, Cu, and active metals was obtained for cross sections of the bonding interface between the circuit layer and the ceramic substrate and the bonding interface between the ceramic substrate and the metal layer using an EPMA apparatus. Each elemental mapping was acquired in each of 5 fields of view.
Then, when Ag + Cu + active metal = 100% by mass, the area where the Ag concentration is 15% by mass or more is defined as the Ag-Cu alloy layer, and the area is obtained and divided by the width of the measurement area (area / measurement area width). The average of the values is shown in Table 2 as the thickness of the Ag--Cu alloy layer.

(Cold/heat cycle reliability)
Depending on the material of the ceramic substrate, the insulating circuit substrate described above was subjected to the following cooling and heating cycles, and the presence or absence of cracks in the ceramics was determined by SAT inspection. Table 2 shows the evaluation results.
For AlN, Al ₂ O ₃ : −40° C.×5 min←→150° C.×5 min, SAT inspection every 50 cycles up to 500 cycles.
For Si ₃ N ₄ : SAT inspection every 200 cycles up to 2000 cycles at −40° C.×5 min←→150° C.×5 min.

First, invention examples 1-3 using AlN as a ceramic substrate and comparative examples 1 and 2 are compared.
In Comparative Example 1, the difference between the maximum reaching distance _LA of the active metal diffusion region in the peripheral region of the copper plate and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate was set to 15 μm. , the maximum reaching distance _LA of the active metal diffusion region in the peripheral region of the copper plate is set to 12 μm, and the number of cracks generated is 200 times in the thermal cycle test.
In Comparative Example 2, the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper plate is 16 μm, and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate is 19 μm. In the cycle test, cracks occurred 150 times.

On the other hand, in Inventive Examples 1-3, the maximum reaching distance L _A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper plate and the active metal diffusion region in the central region of the copper plate The maximum reaching distance _LB from the compound layer is set to be in the range of 20 μm or more and 80 μm or less, and the difference between the maximum reaching distance _LA and the maximum reaching distance _LB is set to 10 μm or less. The number of times cracks occurred was 300 to 500, indicating excellent thermal cycle reliability.

Next, invention examples 4-6 using Si ₃ N ₄ as the ceramic substrate and comparative examples 3 and 4 are compared.
In Comparative Example 3, the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper plate was 108 μm, and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate was 102 μm. In the cycle test, cracks occurred 1200 times.
In Comparative Example 4, the difference between the maximum reaching distance _LA of the active metal diffusion region in the peripheral region of the copper plate and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate was 14 μm. , the number of cracks occurred 1400 times in the thermal cycle test.

On the other hand, in Inventive Examples 4-6, the maximum reaching distance L _A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper plate and the active metal diffusion region in the central region of the copper plate The maximum reaching distance _LB from the compound layer is set to be in the range of 20 μm or more and 80 μm or less, and the difference between the maximum reaching distance _LA and the maximum reaching distance _LB is set to 10 μm or less. The number of times cracks occurred exceeded 1,600 to 2,000 times, indicating excellent thermal cycle reliability.

Next, inventive examples 7 and 8 using Al ₂ O ₃ as the ceramic substrate and comparative example 5 are compared.
In Comparative Example 5, the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper plate was 16 μm, and the maximum reaching distance _LB of the active metal diffusion region in the central region of the copper plate was 18 μm. In the test, cracks occurred 50 times.

On the other hand, in Examples 7 and 8 of the present invention, the maximum reaching distance L _A from the active metal compound layer of the active metal diffusion region in the peripheral region of the copper plate and the active metal diffusion region in the central region of the copper plate The maximum reaching distance _LB from the compound layer is set to be in the range of 20 μm or more and 80 μm or less, and the difference between the maximum reaching distance _LA and the maximum reaching distance _LB is set to 10 μm or less. The number of times cracks occurred was 350 to 450, indicating excellent thermal cycle reliability.

From the results of the above confirmation experiments, according to the example of the present invention, even when a severe thermal cycle is applied, the occurrence of cracks in the ceramic member can be suppressed, and the insulated circuit board (copper / It was confirmed that it is possible to provide a ceramic bonded body).

10 Insulated circuit board (copper/ceramic joint)
11 Ceramic substrate (ceramic member)
12 circuit layer (copper member)
13 metal layer (copper member)
21 (21A, 21B) active metal compound layer 22 (22A, 22B) Ag—Cu alloy layer 23 (23A, 23B) active metal diffusion region

Claims (6)

A copper/ceramic joined body obtained by joining a copper member made of copper or a copper alloy and a ceramic member,
An active metal compound layer is formed on the ceramic member side at the bonding interface between the ceramic member and the copper member,
Active metals (Ti, Zr, Nb, Hf) are diffused from the ceramic member side to the copper member side of the copper member on the ceramic member side, thereby increasing the concentration of the active metal in the copper member. is 0.5% by mass or more, and an active metal diffusion region is formed,
The maximum reaching distance LA of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper member and the distance _LA of the active metal diffusion region from the active metal compound layer in the central region of the copper member The maximum reaching distance L _B is set within the range of 20 μm or more and 80 μm or less,
A difference between the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper member and the maximum reaching distance L _B of the active metal diffusion region in the central region of the copper member is 10 μm or less. A copper/ceramic bonded body characterized by: The thickness t1A of the active metal compound layer formed in the peripheral region of the copper member and the thickness _t1B of the active metal compound layer formed in the central region of the copper member are 0.05 μm or _more1 . 2. The copper/ceramic joined body according to claim 1, wherein the thickness is within the range of 2 μm or less, and the thickness ratio _t1A / _t1B is within the range of 0.7 or more and 1.4 or less. At the bonding interface between the ceramic member and the copper member, an Ag—Cu alloy layer is formed on the copper member side,
The thickness _t2A of the Ag--Cu alloy layer formed in the peripheral region of the copper member and the thickness _t2B of the Ag--Cu alloy layer formed in the central region of the copper member are 1 μm or more and 30 μm or less. , and the thickness ratio t2 _A / t2 _B is within the range of 0.7 or more and 1.4 or less. Copper / ceramics joined body according to claim 1 or 2 . An insulated circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate,
At the bonding interface between the ceramic substrate and the copper plate, an active metal compound layer is formed on the ceramic substrate side,
Active metals (Ti, Zr, Nb, Hf) are diffused from the ceramic substrate side to the copper plate side of the copper plate on the ceramic substrate side, so that the concentration of the active metals in the copper plate is reduced to 0.0. an active metal diffusion region of 5% by mass or more is formed;
The maximum reach distance _LA of the active metal diffusion region from the active metal compound layer in the peripheral region of the copper plate and the maximum reach of the active metal diffusion region from the active metal compound layer in the central region of the copper plate The distance _LB is within the range of 20 μm or more and 80 μm or less,
The difference between the maximum reaching distance L _A of the active metal diffusion region in the peripheral region of the copper plate and the maximum reaching distance L _B of the active metal diffusion region in the central region of the copper plate is 10 μm or less. An insulated circuit board, characterized in that: The thickness _t1A of the active metal compound layer formed in the peripheral region of the copper plate and the thickness _t1B of the active metal compound layer formed in the central region of the copper plate are 0.05 μm or more and 1.2 μm or less. and the thickness ratio _t1A / _t1B is in the range of 0.7 to 1.4. At the bonding interface between the ceramic substrate and the copper plate, an Ag—Cu alloy layer is formed on the copper plate side,
The thickness _t2A of the Ag--Cu alloy layer formed in the peripheral region of the copper plate and the thickness _t2B of the Ag--Cu alloy layer formed in the central region of the copper plate are in the range of 1 μm or more and 30 μm or less. 6. The insulated circuit board according to claim 4, wherein the thickness ratio _t2A / _t2B is in the range of 0.7 to 1.4.

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