阅读说明：本技术 铜-陶瓷接合体、绝缘电路基板、铜-陶瓷接合体的制造方法及绝缘电路基板的制造方法 (Copper-ceramic joined body, insulated circuit board, method for producing copper-ceramic joined body, and method for producing insulated circuit board ) 是由 寺崎伸幸 于 2019-08-27 设计创作，主要内容包括：本发明的铜-陶瓷接合体通过接合由铜或铜合金构成的铜部件(22)与由氮化铝构成的陶瓷部件(11)而成,其特征在于,在铜部件(22)与陶瓷部件(11)之间,形成有Mg固溶于Cu的母相中的Mg固溶层(32)。(A copper-ceramic joined body comprising a copper member (22) made of copper or a copper alloy and a ceramic member (11) made of aluminum nitride joined together, characterized in that a solid Mg solution layer (32) in which Mg is dissolved in a matrix phase of Cu is formed between the copper member (22) and the ceramic member (11).)

1. A copper-ceramic joined body obtained by joining a copper member made of copper or a copper alloy and a ceramic member made of aluminum nitride,

an Mg solid solution layer in which Mg is solid-dissolved in a matrix phase of Cu is formed between the copper member and the ceramic member.

2. The copper-ceramic junction body according to claim 1,

an area ratio of the intermetallic compound phase in a region of 50 μm from the joining surface of the ceramic member toward the copper member side is 15% or less.

3. An insulated circuit board comprising a ceramic substrate made of aluminum nitride and a copper plate made of copper or a copper alloy bonded to a surface of the ceramic substrate,

an Mg solid solution layer in which Mg is solid-dissolved in a matrix phase of Cu is formed between the copper plate and the ceramic substrate.

4. The insulated circuit substrate of claim 3,

an area ratio of the intermetallic compound phase in a region of 50 μm from the bonding surface of the ceramic substrate toward the copper plate side is 15% or less.

5. A method for producing a copper-ceramic bonded body according to claim 1 or 2, the method comprising:

an Mg placement step of placing Mg between the copper member and the ceramic member;

a lamination step of laminating the copper member and the ceramic member via Mg; and

a joining step of joining the copper member and the ceramic member laminated via Mg by heat treatment in a vacuum atmosphere while pressing the copper member and the ceramic member in a lamination direction,

in the Mg disposing step, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

6. The method of producing a copper-ceramic joined body according to claim 5,

the pressure load in the bonding step is set to be in the range of 0.049MPa to 3.4MPa, and the heating temperature is set to be in the range of 500 ℃ to 850 ℃.

7. A method for manufacturing an insulated circuit board according to claim 3 or 4, comprising:

an Mg placement step of placing Mg between the copper plate and the ceramic substrate;

a lamination step of laminating the copper plate and the ceramic substrate via Mg; and

a bonding step of bonding the copper plate and the ceramic substrate laminated via Mg by heat treatment in a vacuum atmosphere while pressing the copper plate and the ceramic substrate in a lamination direction,

in the Mg disposing step, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

8. The method of manufacturing an insulated circuit substrate according to claim 7,

the pressure load in the bonding step is set to be in the range of 0.049MPa to 3.4MPa, and the heating temperature is set to be in the range of 500 ℃ to 850 ℃.

Technical Field

The present invention relates to a copper-ceramic joined body obtained by joining a copper member made of copper or a copper alloy and a ceramic member made of aluminum nitride, an insulated circuit board, a method for producing a copper-ceramic joined body, and a method for producing an insulated circuit board.

The present application claims priority based on patent application No. 2018-159457 filed in japanese application at 28.8.2018, and the contents thereof are incorporated herein by reference.

Background

The power module, the LED module and the thermoelectric module are arranged in the following structures: a power semiconductor element, an LED element, and a thermoelectric element are bonded to an insulating circuit board in which a circuit layer made of a conductive material is formed on one surface of an insulating layer.

For example, a power semiconductor device for high power control used for controlling a wind power generation, an electric vehicle, a hybrid vehicle, or the like generates a large amount of heat during operation, and therefore, as a substrate on which the power semiconductor device is mounted, for example, the following insulating circuit substrate has been widely used: the insulating circuit board includes a ceramic substrate made of aluminum nitride and a circuit layer formed by bonding a metal plate having excellent conductivity to one surface of the ceramic substrate. As an insulated circuit board, there is also provided a board in which a metal layer is formed by bonding a metal plate to the other surface of a ceramic board.

For example, patent document 1 proposes the following insulated circuit board: the first metal plate and the second metal plate constituting the circuit layer and the metal layer were copper plates, and the copper plates were directly bonded to the ceramic substrate by a DBC method. In the DBC method, a liquid phase is generated at an interface between the copper plate and the ceramic substrate by utilizing a eutectic reaction between copper and a copper oxide, thereby bonding the copper plate and the ceramic substrate.

Further, patent document 2 proposes an insulated circuit board in which: a circuit layer and a metal layer are formed on one surface and the other surface of the ceramic substrate by bonding copper plates. In this insulated circuit board, copper plates are arranged on one surface and the other surface of a ceramic substrate with an Ag — Cu — Ti-based brazing material interposed therebetween, and the copper plates are joined by heat treatment (so-called active metal brazing method). In this active metal brazing method, since a brazing material containing Ti as an active metal is used, the wettability of the molten brazing material with the ceramic substrate is improved, and the ceramic substrate and the copper plate are well joined.

Patent document 3 proposes a slurry including: a brazing filler metal for bonding a copper plate and a ceramic substrate in a high-temperature nitrogen atmosphere contains a powder made of a Cu-Mg-Ti alloy. In patent document 3, the Cu — Mg — Ti alloy is heated at 560 to 800 ℃ in a nitrogen atmosphere to bond the Cu — Mg — Ti alloy, and Mg in the Cu — Mg — Ti alloy is sublimated without remaining in a bonding interface, and titanium nitride (TiN) is not substantially formed.

Patent document 1: japanese laid-open patent publication No. H04-162756

Patent document 2: japanese patent No. 3211856

Patent document 3: japanese patent No. 4375730

However, as disclosed in patent document 1, when the ceramic substrate and the copper plate are bonded by the DBC method, the bonding temperature needs to be 1065 ℃ or higher (the eutectic temperature between copper and copper oxide or higher), and therefore the ceramic substrate may be deteriorated during bonding. Further, when bonding is performed in a nitrogen atmosphere or the like, there is a problem that the atmosphere gas remains at the bonding interface and partial discharge is likely to occur.

As disclosed in patent document 2, when a ceramic substrate and a copper plate are joined by an active metal brazing method, the brazing material contains Ag, and Ag is present at the joining interface, so that migration is likely to occur, and the brazing material cannot be used for high withstand voltage applications. Further, since the bonding temperature is relatively high and 900 ℃, the ceramic substrate may be deteriorated. In addition, a titanium nitride phase or an intermetallic compound phase containing Ti is generated in the vicinity of the bonding surface of the ceramic substrate, and the ceramic substrate may be cracked during high-temperature operation.

As disclosed in patent document 3, when a slurry contains a powder made of a Cu — Mg — Ti alloy and is joined in a nitrogen atmosphere using a joining solder made of the slurry, there is a problem that gas remains at a joining interface and partial discharge is likely to occur. Further, organic matter contained in the slurry remains at the bonding interface, and there is a possibility that the bonding may become insufficient. Further, an intermetallic compound phase containing Ti is generated in the vicinity of the bonding surface of the ceramic substrate, and the ceramic substrate may be cracked during high-temperature operation.

Disclosure of Invention

The present invention has been made in view of the above circumstances, and an object thereof is to provide a copper-ceramic joined body, an insulated circuit board, a method for producing the copper-ceramic joined body, and a method for producing the insulated circuit board, in which a copper member and a ceramic member are joined reliably, the copper-ceramic joined body has excellent migration resistance, and occurrence of ceramic cracking during high-temperature operation can be suppressed.

In order to solve the above problems and achieve the above object, a copper-ceramic joined body according to the present invention is a copper-ceramic joined body obtained by joining a copper member made of copper or a copper alloy and a ceramic member made of aluminum nitride, wherein a Mg solid solution layer in which Mg is solid-dissolved in a matrix phase of Cu is formed between the copper member and the ceramic member.

In the copper-ceramic joined body having such a structure, since a Mg solid solution layer in which Mg is solid-dissolved in a matrix phase of Cu is formed between the copper member made of copper or a copper alloy and the ceramic member made of aluminum nitride, Mg disposed between the ceramic member and the copper member sufficiently diffuses toward the copper member side, and Cu and Mg sufficiently react. Therefore, the interface reaction is sufficiently performed at the joint interface between the copper member and the ceramic member, and a copper-ceramic joint body in which the copper member and the ceramic member are reliably joined can be obtained. Further, since Ti, Zr, Nb, and Hf are not present at the joint interface between the Cu member and the ceramic member, nitride phases of Ti, Zr, Nb, and Hf or intermetallic compound phases containing Ti, Zr, Nb, and Hf are not generated, and cracking of the ceramic member can be suppressed even during high-temperature operation.

Further, since Ag is not present at the joint interface between the Cu member and the ceramic member, the migration resistance is also excellent.

In the copper-ceramic joined body of the present invention, the area ratio of the intermetallic compound phase in a region of 50 μm from the joining surface of the ceramic member toward the copper member side is preferably 15% or less.

In this case, since the area ratio of the intermetallic compound phase in the region of 50 μm from the joining surface of the ceramic member toward the copper member side is 15% or less, a large amount of hard and brittle intermetallic compound phases do not exist in the vicinity of the joining surface of the ceramic member, and cracking of the ceramic member during high-temperature operation can be reliably suppressed.

An insulated circuit board according to the present invention is an insulated circuit board obtained by bonding a copper plate made of copper or a copper alloy to a surface of a ceramic substrate made of aluminum nitride, wherein a solid-solution layer of Mg in which Mg is solid-dissolved in a matrix phase of Cu is formed between the copper plate and the ceramic substrate.

In the insulated circuit board having such a structure, the copper plate and the ceramic substrate are reliably bonded, and the insulated circuit board has excellent migration resistance and can be used with high reliability even under high withstand voltage conditions.

The ceramic substrate can be prevented from cracking during high-temperature operation, and can be used with high reliability even under high-temperature conditions.

In the insulated circuit board of the present invention, the area ratio of the intermetallic compound phase in a region of 50 μm from the bonding surface of the ceramic substrate to the copper plate side is preferably 15% or less.

In this case, since the area ratio of the intermetallic compound phase in the region of 50 μm from the bonding surface of the ceramic substrate to the copper plate side is 15% or less, a large amount of hard and brittle intermetallic compound phases do not exist in the vicinity of the bonding surface of the ceramic substrate, and cracking of the ceramic substrate during high-temperature operation can be reliably suppressed.

The method for producing a copper-ceramic bonded body of the present invention is a method for producing a copper-ceramic bonded body, the method comprising: a Mg arrangement step of arranging between the copper member and the ceramic memberPlacing Mg; a lamination step of laminating the copper member and the ceramic member via Mg; and a joining step of joining the copper member and the ceramic member laminated via Mg by heating in a vacuum atmosphere while pressing the copper member and the ceramic member in a laminating direction, wherein in the Mg disposing step, an amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

According to the method of manufacturing a copper-ceramic joined body having such a structure, Mg is disposed between the copper member and the ceramic member, and heat treatment is performed in a vacuum atmosphere while pressurizing them in the lamination direction, so that no gas, organic matter, or the like remains at the joining interface.

In the Mg disposing step, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²In the following range, a liquid phase necessary for the interfacial reaction can be sufficiently obtained. Therefore, a copper-ceramic joined body in which the copper member and the ceramic member are reliably joined can be obtained.

Since Ti, Zr, Nb, and Hf are not used for bonding, a nitride phase of Ti, Zr, Nb, and Hf or an intermetallic compound phase containing Ti, Zr, Nb, and Hf does not exist in the vicinity of the bonding surface of the ceramic member, and a copper-ceramic bonded body in which cracking of the ceramic member during high-temperature operation can be suppressed can be obtained.

Since Ag is not used for bonding, a copper-ceramic bonded body having excellent migration resistance can be obtained.

In the method for producing a copper-ceramic bonded body according to the present invention, it is preferable that the pressing load in the bonding step is set to be in a range of 0.049MPa to 3.4MPa, and the heating temperature is set to be in a range of 500 ℃ to 850 ℃.

In this case, since the pressure load in the joining step is set in the range of 0.049MPa to 3.4MPa, the ceramic member, the copper member, and Mg can be brought into close contact with each other, and the interface reaction between them can be promoted during heating.

Since the heating temperature in the bonding step is set to 500 ℃ or higher than the eutectic temperature of Cu and Mg, a liquid phase can be sufficiently generated at the bonding interface. On the other hand, since the heating temperature in the bonding step is set to 850 ℃ or lower, the occurrence of an excessive liquid phase can be suppressed. Further, the thermal load on the ceramic member is reduced, and the deterioration of the ceramic member can be suppressed.

A method for manufacturing an insulated circuit board according to the present invention is a method for manufacturing an insulated circuit board, including: an Mg placement step of placing Mg between the copper plate and the ceramic substrate; a lamination step of laminating the copper plate and the ceramic substrate via Mg; and a bonding step of bonding the copper plate and the ceramic substrate laminated via Mg by heating in a vacuum atmosphere while pressing the copper plate and the ceramic substrate in a laminating direction, wherein in the Mg disposing step, an amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

According to the method for manufacturing an insulated circuit board having this configuration, Mg is disposed between the copper plate and the ceramic substrate, and these are subjected to heat treatment in a vacuum atmosphere in a state where they are pressurized in the lamination direction, so that no gas, organic matter, or the like remains at the bonding interface.

In the Mg disposing step, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²In the following range, a liquid phase necessary for the interfacial reaction can be sufficiently obtained. Therefore, an insulated circuit board in which the copper plate and the ceramic substrate are reliably joined can be obtained. Further, since Ti, Zr, Nb, and Hf are not used for bonding, a nitride phase of Ti, Zr, Nb, and Hf or an intermetallic compound phase containing Ti, Zr, Nb, and Hf does not exist in the vicinity of the bonding surface of the ceramic substrate, and an insulated circuit board in which cracking of the ceramic substrate during high-temperature operation can be suppressed can be obtained.

Further, since Ag is not used for bonding, an insulated circuit board having excellent migration resistance can be obtained.

In the method for manufacturing an insulated circuit board according to the present invention, it is preferable that the pressure load in the bonding step is set to be in a range of 0.049MPa to 3.4MPa, and the heating temperature is set to be in a range of 500 ℃ to 850 ℃.

In this case, since the pressure load in the bonding step is set in the range of 0.049MPa to 3.4MPa, the ceramic substrate, the copper plate, and Mg can be brought into close contact with each other, and the interface reaction between them can be promoted during heating.

Since the heating temperature in the bonding step is set to 500 ℃ or higher than the eutectic temperature of Cu and Mg, a liquid phase can be sufficiently generated at the bonding interface. On the other hand, since the heating temperature in the bonding step is set to 850 ℃ or lower, the occurrence of an excessive liquid phase can be suppressed. Further, the thermal load on the ceramic substrate is reduced, and the deterioration of the ceramic substrate can be suppressed.

According to the present invention, it is possible to provide a copper-ceramic joined body, an insulated circuit board, a method for producing the copper-ceramic joined body, and a method for producing the insulated circuit board, in which a copper member and a ceramic member are joined reliably, the copper-ceramic joined body has excellent migration resistance, and occurrence of ceramic cracking during high-temperature operation can be suppressed.

Drawings

Fig. 1 is a schematic explanatory view of a power module using an insulated circuit board (copper-ceramic bonded body) according to an embodiment of the present invention.

Fig. 2 is a schematic view of a bonding interface between a circuit layer (copper member) and a metal layer (copper member) of an insulated circuit board (copper-ceramic bonded body) and a ceramic board (ceramic member) according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a method for producing an insulated circuit board (copper-ceramic bonded body) according to an embodiment of the present invention.

Fig. 4 is an explanatory view showing a method for producing an insulated circuit board (copper-ceramic bonded body) according to an embodiment of the present invention.

FIG. 5 shows the results of observing the bonding interface between the copper plate and the ceramic substrate in the copper-ceramic bonded body of example 1 of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The copper-ceramic joined body according to the present embodiment is an insulated circuit board 10 configured by joining a ceramic board 11 as a ceramic member, and a copper plate 22 (circuit layer 12) and a copper plate 23 (metal layer 13) as copper members.

Fig. 1 shows an insulated circuit board 10 according to an embodiment of the present invention and a power module 1 using the insulated circuit board 10.

The power module 1 includes: an insulated circuit board (10); a semiconductor element 3 bonded to one side (upper side in fig. 1) of the insulating circuit board 10 via a first solder layer 2; and a heat sink 51 bonded to the other side (lower side in fig. 1) of the insulated circuit board 10 via the second solder layer 8.

The insulated circuit board 10 includes: a ceramic substrate 11; a circuit layer 12 disposed on one surface (upper surface in fig. 1) of the ceramic substrate 11; and a metal layer 13 disposed on the other surface (lower surface in fig. 1) of the ceramic substrate 11.

The ceramic substrate 11 is for preventing electrical connection between the circuit layer 12 and the metal layer 13, and is made of aluminum nitride having high insulation properties in the present embodiment. The thickness of the ceramic substrate 11 is set in a range of 0.2mm to 1.5mm, and in the present embodiment, the thickness of the ceramic substrate 11 is preferably 0.635 mm.

As shown in fig. 4, the circuit layer 12 is formed by bonding a copper plate 22 made of copper or a copper alloy to one surface of the ceramic substrate 11. In the present embodiment, as the copper plate 22 constituting the circuit layer 12, a rolled plate of oxygen-free copper is used. The circuit layer 12 is formed with a circuit pattern, one surface (upper surface in fig. 1) of which is a mounting surface on which the semiconductor element 3 is mounted. The thickness of the circuit layer 12 is set in a range of 0.1mm to 1.0mm, and in the present embodiment, the thickness of the circuit layer 12 is preferably 0.6 mm.

As shown in fig. 4, the metal layer 13 is formed by bonding a copper plate 23 made of copper or a copper alloy to the other surface of the ceramic substrate 11. In the present embodiment, as the copper plate 23 constituting the metal layer 13, a rolled plate of oxygen-free copper is used. The thickness of the metal layer 13 is set in a range of 0.1mm to 1.0mm, and in the present embodiment, the thickness of the metal layer 13 is preferably 0.6 mm.

The heat sink 51 is a heat sink for cooling the insulating circuit board 10, and in the present embodiment, is made of a material having good heat conductivity. In the present embodiment, the heat sink 51 is preferably made of copper or a copper alloy having excellent heat conductivity. The heat sink 51 is bonded to the metal layer 13 of the insulating circuit board 10 via the second solder layer 8.

As shown in fig. 4, the ceramic substrate 11 and the circuit layer 12 (copper plate 22) and the ceramic substrate 11 and the metal layer 13 (copper plate 23) are bonded via the Mg film 25.

As shown in fig. 2, a Mg solid solution layer 32 in which Mg is solid-dissolved in a parent phase of Cu is formed at a bonding interface between the ceramic substrate 11 and the circuit layer 12 (copper plate 22) and at a bonding interface between the ceramic substrate 11 and the metal layer 13 (copper plate 23).

The Mg content in the Mg solid solution layer 32 is set to be in the range of 0.01 atomic% to 3 atomic%. The thickness of the Mg solid solution layer 32 is set to be in the range of 0.1 μm to 150 μm, preferably 0.1 μm to 80 μm.

The Mg solid solution layer 32 has a concentration gradient in which the Mg concentration gradually increases from the circuit layer 12 (metal layer 13) toward the ceramic substrate 11.

In the present embodiment, the area ratio of the intermetallic compound phase in a region of 50 μm from the bonding surface of the ceramic substrate 11 toward the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) is preferably 15% or less.

As described above, if the area ratio of the intermetallic compound phase in the joint interface is suppressed, a Cu — Mg intermetallic compound phase containing Cu and Mg may be dispersed in the Mg solid solution layer 32. As the Cu-Mg intermetallic compound phase, for example, Cu is mentioned₂Mg、CuMg₂And the like.

Next, a method for manufacturing the insulated circuit board 10 according to the present embodiment will be described with reference to fig. 3 and 4.

(Mg disposing step S01)

As shown in fig. 4, Mg is disposed between the copper plate 22 to be the circuit layer 12 and the ceramic substrate 11, and between the copper plate 23 to be the metal layer 13 and the ceramic substrate 11. In the present embodiment, the Mg film 25 is formed by depositing Mg.

In the Mg disposing step S01, the amount of Mg disposed was set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

(laminating step S02)

Next, the copper plate 22 and the ceramic substrate 11 are laminated via the Mg film 25, and the ceramic substrate 11 and the copper plate 23 are laminated via the Mg film 25.

(joining step S03)

Next, the copper plate 22, the ceramic substrate 11, and the copper plate 23 are stacked while being pressurized in the stacking direction, and are placed in a vacuum furnace and heated, thereby bonding the copper plate 22, the ceramic substrate 11, and the copper plate 23.

The pressure load in the bonding step S03 is preferably set to be in the range of 0.049MPa to 3.4 MPa.

The heating temperature in the joining step S03 is preferably in the range of 500 ℃ to 850 ℃.

The degree of vacuum in the bonding step S03 is preferably set to 1X 10^-6Pa or more and 5X 10^-2Pa or less.

The holding time at the heating temperature is preferably set within a range of 5min to 180 min.

The cooling rate when the temperature is lowered from the heating temperature (bonding temperature) to 480 ℃ is not particularly limited, but is preferably 25 ℃/min or less, and more preferably 20 ℃/min or less. The lower limit of the cooling rate is not particularly limited, and may be 3 ℃/min or more, or may be 5 ℃/min or more.

As described above, the insulated circuit board 10 of the present embodiment is manufactured through the Mg placement step S01, the lamination step S02, and the bonding step S03.

(Heat sink bonding step S04)

Next, the heat sink 51 is bonded to the other surface of the metal layer 13 of the insulating circuit board 10. The insulating circuit board 10 and the heat sink 51 are stacked via a solder material and loaded into a heating furnace, and the insulating circuit board 10 and the heat sink 51 are solder-bonded via the second solder layer 8.

(semiconductor element bonding step S05)

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

Through the above steps, the power module 1 shown in fig. 1 is manufactured.

According to the insulated circuit board 10 (copper-ceramic bonded body) of the present embodiment having the above configuration, since the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) made of oxygen-free copper and the ceramic board 11 made of aluminum nitride are bonded via the Mg film 25, and the Mg solid solution layer 32 in which Mg is solid-dissolved in the parent phase of Cu is formed between the ceramic board 11 and the circuit layer 12 (copper plate 22) and between the ceramic board 11 and the metal layer 13 (copper plate 22), Mg disposed between the ceramic board 11 and the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) is sufficiently diffused to the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) side, and Cu and Mg react sufficiently. Therefore, the interface reaction is sufficiently performed at the bonding interface, and the insulating circuit board 10 (copper-ceramic bonded body) in which the copper plate 22 (circuit layer 12), the copper plate 23 (metal layer 13) and the ceramic board 11 are reliably bonded can be obtained.

Since Ti, Zr, Nb, and Hf are not present at the bonding interface between the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) and the ceramic substrate 11, nitride phases of Ti, Zr, Nb, and Hf or intermetallic compound phases containing Ti, Zr, Nb, and Hf are not generated, and cracking of the ceramic substrate 11 can be suppressed even during high-temperature operation. The total content of Ti, Zr, Nb, and Hf in the bonding interface between the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) and the ceramic substrate 11 is preferably 0.3 mass% or less, and more preferably 0.1 mass% or less.

Since Ag is not present at the bonding interface between the ceramic substrate 11 and the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13), the migration resistance is excellent. The content of Ag in the bonding interface between the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) and the ceramic substrate 11 is preferably 0.2 mass% or less, and more preferably 0.1 mass% or less.

In the present embodiment, when the area ratio of the intermetallic compound phase in the region from the joining surface of the ceramic substrate 11 to 50 μm toward the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) is 15% or less, a large amount of hard and brittle intermetallic compound phases do not exist near the joining surface of the ceramic substrate 11, and cracking of the ceramic substrate 11 during high-temperature operation can be reliably suppressed.

The area ratio of the intermetallic compound phase in a region of 50 μm from the bonding surface of the ceramic substrate 11 toward the copper plate 22 (circuit layer 12) and the copper plate 23 (metal layer 13) is preferably 10% or less, and more preferably 8% or less.

The method for manufacturing the insulated circuit board 10 (copper-ceramic bonded body) according to the present embodiment includes: an Mg disposing step S01 of disposing Mg (Mg film 25) between the copper plates 22 and 23 and the ceramic substrate 11; a laminating step S02 of laminating the copper plates 22 and 23 and the ceramic substrate 11 via the Mg film 25; and a bonding step S03 of bonding the laminated copper plate 22, ceramic substrate 11, and copper plate 23 by heat treatment in a vacuum atmosphere while pressurizing them in the laminating direction, so that no gas or organic matter residue remains at the bonding interface.

In the Mg disposing step S01, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²In the following range, a liquid phase necessary for the interfacial reaction can be sufficiently obtained. This makes it possible to obtain the insulated circuit board 10 (copper-ceramic bonded body) in which the copper plates 22 and 23 and the ceramic board 11 are reliably bonded.

Since Ti, Zr, Nb, and Hf are not used for bonding, a nitride phase of Ti, Zr, Nb, and Hf or an intermetallic compound phase containing Ti, Zr, Nb, and Hf does not exist in the vicinity of the bonding surface of the ceramic substrate 11, and thus the insulating circuit substrate 10 (copper-ceramic bonded body) capable of suppressing cracking of the ceramic substrate 11 at the time of high-temperature operation can be obtained.

Since Ag is not used for bonding, the insulating circuit board 10 (copper-ceramic bonded body) having excellent migration resistance can be obtained.

The Mg content is less than 0.17Mg/cm²In the case of (3), the amount of the generated liquid phase is insufficient, and the bonding rate may be lowered. Further, the amount of Mg exceeds 3.48Mg/cm²In the case of (3), the amount of the generated liquid phase is too large, and the liquid phase leaks from the bonding interface, and there is a possibility that a bonded body having a predetermined shape cannot be manufactured. In addition, Cu-Mg intermetallic compoundThe compound phase may be excessively generated, and the ceramic substrate 11 may be broken.

Therefore, in the present embodiment, the amount of Mg is set to 0.17Mg/cm²Above and 3.48mg/cm²Within the following ranges.

The lower limit of the amount of Mg is preferably 0.24Mg/cm²Above, more preferably 0.32mg/cm²The above. On the other hand, the upper limit of the amount of Mg is preferably 2.38Mg/cm²Hereinafter, more preferably 1.58mg/cm²The following.

In the present embodiment, since the pressing load in the bonding step S03 is set to 0.049MPa or more, the ceramic substrate 11, the copper plates 22 and 23, and the Mg film 25 can be brought into close contact with each other, and the interface reaction therebetween can be promoted during heating. Since the pressure load in the bonding step S03 is 3.4MPa or less, cracking and the like of the ceramic substrate 11 in the bonding step S03 can be suppressed.

The lower limit of the pressing load in the joining step S03 is preferably 0.098MPa or more, and more preferably 0.294MPa or more. On the other hand, the upper limit of the pressing load in the bonding step S03 is preferably 1.96MPa or less, and more preferably 0.98MPa or less.

In the present embodiment, the heating temperature in the bonding step S03 is set to 500 ℃ or higher than the eutectic temperature of Cu and Mg, and therefore, a liquid phase can be sufficiently generated at the bonding interface. On the other hand, since the heating temperature in the joining step S03 is set to 850 ℃ or lower, the occurrence of an excessive liquid phase can be suppressed. Further, the thermal load on the ceramic substrate 11 is reduced, and deterioration of the ceramic substrate 11 can be suppressed.

The lower limit of the heating temperature in the bonding step S03 is preferably 600 ℃ or higher, and more preferably 680 ℃ or higher. On the other hand, the upper limit of the heating temperature in the bonding step S03 is preferably 800 ℃ or lower, and more preferably 760 ℃ or lower.

In the present embodiment, the degree of vacuum in the bonding step S03 is set to 1 × 10^-6Pa or more and 5X 10^-2In the range of Pa or less, oxidation of the Mg film 25 can be suppressed, and the ceramic substrate 11 and the copper plates 22 and 23 can be reliably bonded.

The lower limit of the degree of vacuum in the bonding step S03 is preferably 1 × 10^-4Pa or more, more preferably 1X 10^-3Pa or above. On the other hand, the upper limit of the degree of vacuum in the bonding step S03 is preferably 1 × 10^-2Pa or less, more preferably 5X 10^{- 3}Pa or less.

In the present embodiment, when the holding time of the heating temperature in the bonding step S03 is set to be in the range of 5min to 180min, the liquid phase can be sufficiently formed, and the ceramic substrate 11 and the copper plates 22 and 23 can be reliably bonded.

The lower limit of the holding time of the heating temperature in the joining step S03 is preferably 10min or more, and more preferably 30min or more. On the other hand, the upper limit of the holding time of the heating temperature in the joining step S03 is preferably 150min or less, and more preferably 120min or less.

The embodiments of the present invention have been described above, but the present invention is not limited to these embodiments, and can be modified as appropriate within a range not departing from the technical spirit of the present invention.

For example, although the copper plate constituting the circuit layer or the metal layer is described as a rolled plate of oxygen-free copper, the invention is not limited thereto, and may be formed of other copper or copper alloy.

In the present embodiment, the case where the circuit layer and the metal layer are made of copper plates has been described, but the present invention is not limited to this, and if at least one of the circuit layer and the metal layer is made of copper plates, the other may be made of other metal plates such as aluminum plates.

In the present embodiment, the case where the Mg film is formed by vapor deposition in the Mg placement step has been described, but the present invention is not limited to this, and the Mg film may be formed by another method or the Mg foil may be placed. Further, a clad material of Cu and Mg may be disposed.

In the present embodiment, the Mg placement step may be performed by applying a Mg paste and a Cu — Mg paste. Further, the Cu paste and the Mg paste may be stacked. In this case, the Mg paste may be disposed on either the copper plate side or the ceramic substrate side. In additionIn addition, MgH may be provided as Mg₂。

The heat sink is exemplified as a heat sink, but the present invention is not limited thereto, and the structure of the heat sink is not particularly limited. For example, the heat sink may have a flow path through which the refrigerant flows or cooling fins. Further, as the heat spreader, a composite material (e.g., AlSiC) containing aluminum or an aluminum alloy can also be used.

Further, a buffer layer made of aluminum or an aluminum alloy or a composite material containing aluminum (for example, AlSiC or the like) may be provided between the top plate portion or the heat dissipation plate of the heat sink and the metal layer.

In the present embodiment, a case where a power semiconductor element is mounted on a circuit layer of an insulating circuit board to form a power module is described, but the present invention is not limited to this. For example, an LED module may be configured by mounting an LED element on an insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on a circuit layer of an insulating circuit board.

Examples

(inventive example 1 to inventive example 12, comparative example 1 to comparative example 2, and conventional example)

Confirmation experiments for confirming the effectiveness of the present invention will be described.

As shown in table 1, copper plates (oxygen-free copper, 37mm square, 0.15mm thick) containing Mg were stacked on both sides of a ceramic substrate made of 40mm square aluminum nitride, and bonded under the bonding conditions shown in table 1 to form a copper-ceramic bonded body. The thickness of the ceramic substrate was set to 0.635 mm. The degree of vacuum of the vacuum furnace during bonding was set to 5X 10^-3Pa。

In the conventional example, the amount of Ag between the ceramic substrate and the copper plate was 5.2mg/cm²The active solder of Ag-28 mass% Cu-5 mass% Ti was prepared.

In the bonding step S03, the temperature is reduced from the bonding temperature ("temperature (c)") to 480 c, and the temperature reduction rate is controlled so as to be reduced at a rate of 5 c/min. The temperature decrease rate is controlled by the gas partial pressure (presence or absence of circulation by the cooling fin) at the time of gas cooling.

The thus-obtained copper-ceramic bonded body was observed for the bonding interface, and a Mg solid solution layer and a Cu-Mg intermetallic compound phase were confirmed. The initial bonding rate of the copper-ceramic bonded body, and the cracking and migration of the ceramic substrate after the cooling-heating cycle were evaluated as follows.

(Mg solid solution layer)

A region (400 μm x 600 μm) including a bonding interface was observed at 2000-fold magnification and 15kV acceleration voltage on the bonding interface between a copper plate and a ceramic substrate by using an EPMA apparatus (JXA-8539F manufactured by JEOL Ltd.), quantitative analysis was performed at 10 points or more and 20 points or less from the surface of the ceramic substrate toward the copper plate side at intervals of 10 μm according to the thickness of the copper plate, and a region having a Mg concentration of 0.01 atomic% or more was defined as a Mg solid solution layer.

(area ratio of Cu-Mg intermetallic compound phase)

An element MAP of Mg in a region (400. mu. m.times.600. mu.m) including a bonding interface was obtained from a bonding interface between a copper plate and a ceramic substrate by an electron beam microanalyzer (JXA-8539F, manufactured by JEOL Ltd.) under conditions of 2000 times magnification and 15kV acceleration voltage, and a region satisfying a Cu concentration of 5 atomic% or more and a Mg concentration of 30 atomic% or more and 70 atomic% or less was defined as a Cu-Mg intermetallic compound phase on average of 5 points where quantitative analysis was performed in the region where the presence of Mg was confirmed.

Then, the area ratio (%) of the intermetallic compound phase in a region of 50 μm from the bonding surface of the ceramic substrate toward the copper plate side was calculated.

(initial bonding Rate)

The bonding ratio between the copper plate and the ceramic substrate was determined by the following equation using an ultrasonic flaw detector (FineSAT 200 manufactured by Hitachi Power Solutions co., ltd.). The initial joining area refers to an area to be joined before joining, i.e., an area of a joining surface of the copper plates. In the ultrasonic flaw detector, since peeling is indicated by a white portion in the joint, the area of the white portion is defined as the peeling area.

(bonding ratio) { (initial bonding area) - (peeling area) }/(initial bonding area)

(cracking of ceramic substrate)

Using a cold and hot impact tester (TSA-72 ES manufactured by ESPEC corp., ltd.), 300 cycles of-50℃ × 10 minutes ← → 150℃ × 10 minutes were performed in the gas phase.

After the cooling-heating cycle, the presence or absence of cracking of the ceramic substrate was evaluated.

(migration)

The circuit layers were insulated and separated, the distance between the circuit patterns was 0.5mm, the temperature was 85 ℃, the humidity was 85% RH, and the voltage DC50V were placed for 2000 hours, and then the resistance between the circuit patterns was measured to obtain a resistance value of 1X 10⁶If Ω or less is judged to be short-circuited (occurrence of migration), the evaluation of migration is "B". After leaving under the same conditions as described above for 2000 hours, the resistance between the circuit patterns was measured to obtain a resistance value of more than 1X 10⁶In the case of Ω, it is determined that no migration has occurred, and the evaluation of migration is "a".

The evaluation results are shown in table 1. Fig. 5 shows the observation results of inventive example 1.

[ Table 1]

In the Mg preparation step, the amount of Mg was 0.09Mg/cm²In comparative example 1, which is less than the range of the present invention, the liquid phase is insufficient at the time of bonding, and thus a bonded body cannot be formed. Therefore, the evaluation thereafter is suspended.

In the Mg preparation step, the amount of Mg was 4.75Mg/cm²In comparative example 2, which is larger than the range of the present invention, the liquid phase was excessively generated at the time of bonding, and thus the liquid phase leaked from the bonding interface, and a bonded body having a predetermined shape could not be manufactured. Therefore, the evaluation thereafter is suspended.

In the conventional example in which the ceramic substrate and the copper plate were bonded using the Ag — Cu — Ti brazing filler metal, the evaluation of migration was judged to be "B". The reason is presumed to be that Ag is present at the bonding interface.

On the other hand, in invention examples 1 to 12, the initial bonding rate was also high, and no cracking of the ceramic substrate was observed. Also, migration was good.

As shown in fig. 5, the bonding interface was observed, and a Mg solid solution layer 32 was observed.

(inventive example 21 to inventive example 32)

The copper-ceramic bonded bodies were produced in the same manner as the copper-ceramic bonded bodies produced in the above-described invention examples 1 to 12, and the obtained copper-ceramic bonded bodies were evaluated for Cu as follows₂Area ratio of Mg and ultrasonic bonding interface.

The evaluation of the Mg solid solution layer, the area ratio of the Cu-Mg intermetallic compound phase, and the initial bonding ratio of the copper-ceramic bonded body was performed in the same manner as the evaluation performed in the above-described invention examples 1 to 12.

(Cooling speed)

In the bonding step S03, when the temperature was decreased from the bonding temperature ("temperature (° c)") to 480 ℃, the temperature decrease rate was controlled at the rate shown in table 2.

(Cu₂Area fraction of Mg)

Cu in the above Cu-Mg intermetallic compound phase is defined by the following equation₂The area ratio (%) of Mg was calculated.

Cu₂Area ratio (%) of Mg to Cu₂Area of Mg/(Cu)₂Area of Mg + CuMg₂Area of) x 100

“Cu₂The "area of Mg" is a region having a Mg concentration of 30 at% or more and less than 60 at%, "CuMg₂The area "of (b) is a region having a Mg concentration of 60 atomic% or more and less than 70 atomic%.

(ultrasonic bonding)

The obtained copper-ceramic bonded body was ultrasonically bonded to a copper terminal (10 mm. times.5 mm. times.1.5 mm thick) with a collapse amount (コプラス amount) of 0.5mm using an ultrasonic metal bonding machine (60C-904, manufactured by Ltd.).

After bonding, the bonding interface between the copper plate and the ceramic substrate was inspected using an ultrasonic flaw detector (Hitachi Power Solutions co., ltd. FineSAT200), and the case where cracking of the ceramic was observed was evaluated as "C", the case where peeling was observed was evaluated as "B", and the case where neither was observed was evaluated as "a". The evaluation results are shown in table 2.

[ Table 2]

Cu is decreased in temperature rate after the bonding step S03₂The value of the area ratio of Mg and the bondability of ultrasonic bonding were changed.

From the results shown in Table 2, it is clear that the cooling rate is preferably 25 ℃/min or less, and more preferably 20 ℃/min or less.

From the results shown in Table 2, Cu in the Cu-Mg intermetallic compound phase was clarified₂The area ratio of Mg is preferably 55% or more, more preferably 60% or more, and further preferably 67% or more.

As described above, according to the present invention, it has been confirmed that a copper-ceramic joined body (insulated circuit board) in which a copper member and a ceramic member are reliably joined, which has excellent migration resistance, and which can suppress the occurrence of ceramic cracking during high-temperature operation can be provided.

Further, according to the present invention, it was confirmed that a copper-ceramic bonded body (insulated circuit board) in which a copper member and a ceramic member are reliably bonded and which has excellent ultrasonic bonding properties can be provided by controlling the rate of temperature reduction from the bonding temperature to 480 ℃.

Industrial applicability

According to the present invention, it is possible to provide a copper-ceramic joined body, an insulated circuit board, a method for producing the copper-ceramic joined body, and a method for producing the insulated circuit board, in which a copper member and a ceramic member are joined reliably, the copper-ceramic joined body has excellent migration resistance, and occurrence of ceramic cracking during high-temperature operation can be suppressed.

Description of the symbols

10 insulating circuit board

11 ceramic substrate

12 circuit layers

13 Metal layer

22. 23 copper plate

32Mg solid solution layer