JP6939973B2 - Copper / ceramic joints and insulated circuit boards - Google Patents

Description

The present invention comprises a copper / ceramics joint formed by joining a copper member made of copper or a copper alloy and a ceramics member made of silicon-containing ceramics, and a ceramic substrate made of silicon-containing ceramics on the surface of a copper or copper alloy. It relates to an insulated circuit board in which copper plates are joined.

The power module, LED module, and thermoelectric module have a structure in which a power semiconductor element, an LED element, and a thermoelectric element are bonded to an insulating circuit substrate in which a circuit layer made of a conductive material is formed on one surface of the insulating layer. ..
For example, a power semiconductor element for high power control used for controlling a wind power generation, an electric vehicle, a hybrid vehicle, etc. has a large amount of heat generation during operation. An insulated circuit board provided with a circuit layer formed by joining a metal plate having excellent conductivity to one surface of the ceramics substrate has been widely used conventionally. As the insulating circuit board, a circuit board in which a metal plate is joined to the other surface of a ceramics substrate to form a metal layer is also provided.

For example, Patent Document 1 proposes a power module substrate in which a first metal plate and a second metal plate constituting a circuit layer and a metal layer are copper plates, and the copper plates are directly bonded to a ceramic substrate by the DBC method. ing. In this DBC method, the copper plate and the ceramic substrate are joined by forming a liquid phase at the interface between the copper plate and the ceramic substrate by utilizing the eutectic reaction between copper and the copper oxide.

Further, Patent Document 2 proposes an insulating circuit board in which a circuit layer and a metal layer are formed by joining a copper plate to one surface and the other surface of a ceramic substrate. In Patent Document 1, a copper plate is arranged on one surface and the other surface of a ceramic substrate with an Ag-Cu-Ti brazing material interposed therebetween, and the copper plate is joined by heat treatment (so-called). Active metal brazing method). Since this active metal brazing method uses a brazing material containing Ti, which is an active metal, the wettability between the molten brazing material and the ceramic substrate is improved, and the ceramic substrate and the copper plate are satisfactorily bonded. It will be.

Further, Patent Document 3 describes 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, and is formed at a bonding interface. It has been proposed that a nitride compound layer and an Ag—Cu eutectic layer are formed, and the thickness of the nitride compound layer is within the range of 0.15 μm or more and 1.0 μm or less.

Japanese Unexamined Patent Publication No. 04-162756 Japanese Patent No. 3211856 Japanese Unexamined Patent Publication No. 2018-008869

However, as disclosed in Patent Document 1, when the ceramic substrate and the copper plate are joined by the DBC method, the joining temperature is set to 1065 ° C. or higher (eutectic temperature of copper and copper oxide or higher). Since it is necessary, there is a risk that the ceramic substrate may deteriorate at the time of joining.
Further, as disclosed in Patent Document 2, when the ceramic substrate and the copper plate are joined by the active metal brazing method, the joining temperature is relatively high at 900 ° C. Therefore, the ceramics are also used. There was a problem that the substrate deteriorated.

Here, in Patent Document 3, a copper plate made of copper or a copper alloy and a ceramic substrate made of silicon nitride are joined using a joining material containing Ag and Ti, and the ceramic member and the ceramic member are joined under relatively low temperature conditions. It is possible to join with a copper member, and it is possible to suppress deterioration of the ceramic member at the time of joining.

By the way, recently, depending on the application of the insulated circuit board, a more severe cooling / heating cycle may be applied than in the past.
Therefore, there is a demand for an insulating circuit board having high bonding strength and not causing cracks in the ceramic substrate even when the ceramic substrate is loaded with a cold cycle, even in an application where a colder cycle is more severe than before.

The present invention has been made in view of the above-mentioned circumstances, and is a copper / ceramics joint having high bonding strength, less likely to cause cracks in the ceramic substrate even under a cold cycle load, and particularly excellent in cold cycle reliability. , And an insulated circuit board.

In order to solve the above-mentioned problems, the copper / ceramics joint of the present invention is a copper / ceramics joint in which a copper member made of copper or a copper alloy and a ceramics member made of silicon-containing ceramics are joined. The maximum indentation hardness measured using a Berkovich indenter in the region from 10 μm to 50 μm from the bonding interface between the copper member and the ceramic member to the copper member side is in the range of 110 mgf / μm ² or more and 150 mgf / μm ^{2 or less.} At the bonding interface between the ceramic member and the copper member, an active metal containing one or more active metal compounds selected from Ti, Zr, Nb, and Hf on the ceramic member side. A compound layer is formed, and the maximum particle size of the active metal compound particles in the active metal compound layer is 180 nm or less.

According to the copper / ceramics joint of the present invention, the maximum indentation hardness in the region from 10 μm to 50 μm from the bonding interface between the copper member and the ceramics member to the copper member side is 110 mgf / μm ² or more . Therefore, the copper in the vicinity of the bonding interface is sufficiently melted to form a liquid phase, and the ceramic member and the copper member are firmly bonded.
On the other hand, since the maximum indentation hardness in the above-mentioned region is ^{suppressed to 150 mgf / μm 2} or less, the vicinity of the bonding interface is not harder than necessary, and the occurrence of cracks during a thermal cycle load can be suppressed.
Therefore, it is possible to obtain a copper / ceramics bonded body having high bonding strength and particularly excellent thermal cycle reliability.

Further, in the copper / ceramics joint of the present invention, at the bonding interface between the ceramics member and the copper member, one or more types selected from Ti, Zr, Nb, and Hf are placed on the ceramics member side. of which the active metal compound layer containing an active metal compound is formed, the maximum particle size of the active metal compound particles in the active metal compound layer is 180nm or less, in the active metal compound layer, relatively hardness The proportion occupied by the low grain boundary region (metal phase) is increased, and the impact resistance of the active metal compound layer is improved. Thereby, for example, when the terminal material is ultrasonically bonded to the copper member, the generation of cracks in the active metal compound layer is suppressed, the peeling of the copper member and the ceramics member, and the generation of cracks in the ceramics member are suppressed. be able to.

Further, in the copper / ceramics bonded body of the present invention, it is preferable that Si, Cu, and Ag are present in the active metal compound layer.
In this case, since Si, Cu, and Ag are present in the active metal compound layer, the occurrence of cracks in the active metal compound layer can be suppressed, and the bonding interface between the copper member and the ceramic member can be suppressed. A copper / ceramics bonded body having a higher bonding strength can be obtained without forming an unreacted portion.

The insulating circuit substrate of the present invention is an insulating circuit substrate in which a copper plate made of copper or a copper alloy is bonded to the surface of a ceramic substrate made of silicon-containing ceramics, and the copper plate and the ceramic substrate are joined from the bonding interface. The maximum indentation hardness measured using a Berkovich indenter in the region from 10 μm to 50 μm toward the copper plate is within the range of 110 mgf / μm ² or more and 150 mgf / μm ² or less, and at the bonding interface between the copper plate and the ceramics substrate. Is formed on the ceramic substrate side with an active metal compound layer containing one or more active metal compounds selected from Ti, Zr, Nb, and Hf, and the activity in the active metal compound layer. The maximum particle size of the metal compound particles is 180 nm or less.

According to the insulating circuit board of the present invention, the maximum indentation hardness in the region from 10 μm to 50 μm from the bonding interface between the copper plate and the ceramic substrate to the copper plate side is 110 mgf / μm ² or more, and thus the bonding interface. The nearby copper is sufficiently melted to form a liquid phase, and the ceramic substrate and the copper plate are firmly bonded to each other.
On the other hand, since the maximum indentation hardness in the above-mentioned region is ^{suppressed to 150 mgf / μm 2} or less, the vicinity of the bonding interface is not harder than necessary, and the occurrence of cracks during a thermal cycle load can be suppressed.
Therefore, it is possible to obtain an insulated circuit board having high bonding strength and particularly excellent thermal cycle reliability.

Further, in the insulating circuit substrate of the present invention, at the bonding interface between the copper plate and the ceramics substrate, one or more active metals selected from Ti, Zr, Nb, and Hf are placed on the ceramics substrate side. It is active metal compound layer comprising a compound formed, the maximum particle size of the active metal compound particles in the active metal compound layer is 180nm or less, in the active metal compound layer, having a relatively low hardness particle The ratio occupied by the boundary region (metal phase) increases, and the impact resistance of the active metal compound layer is improved. Thereby, for example, when the terminal material is ultrasonically bonded to the copper plate, the generation of cracks in the active metal compound layer can be suppressed, the peeling of the copper plate and the ceramic substrate, and the generation of cracks in the ceramic substrate can be suppressed. can.

Further, in the insulating circuit board of the present invention, it is preferable that Si, Cu, and Ag are present in the active metal compound layer.
In this case, since Si, Cu, and Ag are present in the active metal compound layer, it is possible to suppress the occurrence of cracks in the active metal compound layer and at the bonding interface between the copper plate and the ceramic substrate. An insulated circuit board having a high bonding strength can be obtained without forming an unreacted portion.

According to the present invention, it is possible to provide a copper / ceramics bonded body having high bonding strength, less likely to cause cracks in the ceramic substrate even under a cold cycle load, and particularly excellent in thermal cycle reliability, and an insulating circuit board. can.

It is the schematic explanatory drawing of the power module using the insulation circuit board which concerns on embodiment of this invention. It is an enlarged explanatory view of the bonding interface between the circuit layer (metal layer) of the insulating circuit board which concerns on embodiment of this invention, and a ceramics substrate. It is an observation photograph of the active metal compound layer formed at the junction interface between the circuit layer (metal layer) of the insulating circuit board which concerns on embodiment of this invention, and a ceramics substrate. This is an example of the EDS spectrum of the active metal compound layer. It is a flow chart of the manufacturing method of the insulation circuit board which concerns on embodiment of this invention. It is the schematic explanatory drawing of the manufacturing method of the insulation circuit board which concerns on embodiment of this invention. It is explanatory drawing which shows the measurement part of the maximum indentation hardness in the vicinity of a bonding interface in an Example. It is explanatory drawing which shows the measurement principle of the indentation hardness test in an Example.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
The copper / ceramics joint according to the present embodiment includes a ceramics substrate 11 as a ceramics member made of ceramics, and a copper plate 22 (circuit layer 12) and a copper plate 23 (metal layer 13) as copper members made of copper or a copper alloy. Is an insulated circuit board 10 formed by joining. FIG. 1 shows a power module 1 provided with an insulated circuit board 10 according to the present embodiment.

The power module 1 is a semiconductor element 3 bonded to an insulating circuit board 10 on which a circuit layer 12 and a metal layer 13 are arranged and one surface (upper surface in FIG. 1) of the circuit layer 12 via a bonding layer 2. And a heat sink 30 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 a bonding layer 2.
The bonding layer 2 is made of, for example, a Sn-Ag-based, Sn-In-based, or Sn-Ag-Cu-based solder material.

The heat sink 30 is for dissipating heat from the above-mentioned insulating circuit board 10. The heat sink 30 is made of copper or a copper alloy, and in this embodiment, it is made of phosphorylated copper. The heat sink 30 is provided with a flow path 31 for flowing a cooling fluid.
In this embodiment, the heat sink 30 and the metal layer 13 are joined by a solder layer 32 made of a solder material. The solder layer 32 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 disposed on one surface (upper surface in FIG. 1) of the ceramic substrate 11, and ceramics. It includes a metal layer 13 disposed on the other surface (lower surface in FIG. 1) of the substrate 11.

The ceramic substrate 11 is made of silicon-containing ceramics having excellent insulating properties and heat dissipation, and in this embodiment, it is made of silicon nitride (Si ₃ N ₄ ). The thickness of the ceramic substrate 11 is set, for example, within the range of 0.2 mm or more and 1.5 mm or less, and in the present embodiment, it is set to 0.32 mm.

As shown in FIG. 6, the circuit layer 12 is formed by joining a copper plate 22 made of copper or a copper alloy to one surface (upper surface in FIG. 6) of the ceramic substrate 11.
In the present embodiment, the circuit layer 12 is formed by joining a copper plate 22 made of a rolled plate of oxygen-free copper to a ceramic substrate 11.
The thickness of the copper plate 22 to be the circuit layer 12 is set within the range of 0.1 mm or more and 2.0 mm or less, and in this embodiment, it is set to 0.6 mm.

As shown in FIG. 6, the metal layer 13 is formed by joining a copper plate 23 made of copper or a copper alloy to the other surface (lower surface in FIG. 6) of the ceramic substrate 11.
In the present embodiment, the metal layer 13 is formed by joining a copper plate 23 made of a rolled plate of oxygen-free copper to a ceramic substrate 11.
The thickness of the copper plate 23 to be the metal layer 13 is set within the range of 0.1 mm or more and 2.0 mm or less, and in the present embodiment, it is set to 0.6 mm.

Then, at the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13), as shown in FIG. 2, a compound of one or more active metals selected from Ti, Zr, Nb, and Hf. The active metal compound layer 41 containing the above is formed.
The active metal compound layer 41 is formed by reacting the active metal contained in the bonding material with the ceramic substrate 11.
In the present embodiment, Ti is used as the active metal, and since the ceramic substrate 11 is made of aluminum nitride, the active metal compound layer 41 is a titanium nitride (TiN) layer.

Here, in the insulated circuit board 10 of the present embodiment, the maximum in the region from 10 μm to 50 μm from the junction interface between the circuit layer 12 (metal layer 13) and the ceramics substrate 11 to the circuit layer 12 (metal layer 13) side. The indentation hardness is within the range of ^{70 mgf / μm 2} or more and 150 mgf / μm ^{2 or less.}
Incidentally, it is preferable that the maximum indentation hardness of the lower limit of the above is 75mgf / μm ² or more, and more preferably 85mgf / μm ² or more. On the other hand, the maximum indentation hardness of the upper limit mentioned is preferably at 135mgf / μm ² or less, and more preferably 125mgf / μm ² or less.

Further, in the insulating circuit substrate 10 of the present embodiment, as shown in FIG. 3, it is preferable that the maximum particle size of the active metal compound particles 45 in the active metal compound layer 41 is 180 nm or less. The grain boundaries between the active metal compound particles 45 form a metal phase. Since the maximum particle size of the active metal compound particles 45 is 180 nm or less, the proportion of the metal phase having a relatively low hardness increases, and the impact resistance of the active metal compound layer 41 is improved. Thereby, for example, when the terminal material is ultrasonically bonded to the copper member, the generation of cracks in the active metal compound layer 41 is suppressed, the peeling of the copper member and the ceramics member, and the generation of cracks in the ceramics member are suppressed. Can be done.
The maximum particle size of the active metal compound particles 45 in the active metal compound layer 41 is more preferably 150 nm or less, and even more preferably 120 nm or less.

Further, in the insulating circuit board 10 of the present embodiment, it is preferable that Si, Cu, and Ag are present in the active metal compound layer 41.
For Si, Cu, and Ag present in the active metal compound layer 41, the interparticles and grain boundaries of the active metal compound particles 45 in the active metal compound layer 41 are observed using a transmission electron microscope, and the EDS spectrum is observed. It can be confirmed by obtaining. An example of the EDS spectrum of the active metal compound layer 41 is shown in FIG. Peaks of Si, Cu, and Ag have been confirmed, and it can be seen that Si, Cu, and Ag are present in the active metal compound layer 41.

Hereinafter, a method for manufacturing the insulated circuit board 10 according to the present embodiment will be described with reference to FIGS. 5 and 6.

(Laminating step S01)
First, a ceramic substrate 11 made of silicon nitride (Si ₃ N ₄ ) is prepared, and as shown in FIG. 6, between the copper plate 22 to be the circuit layer 12 and the ceramic substrate 11, and the copper plate 23 to be the metal layer 13. An Ag-Ti-based brazing material (Ag-Cu-Ti-based brazing material) 24 is arranged between the ceramic substrate 11 and the ceramic substrate 11.
As the Ag-Ti-based brazing material (Ag-Cu-Ti-based brazing material) 24, for example, Cu is in the range of 0 mass% or more and 32 mass% or less, and Ti, which is an active metal, is 0.5 mass% or more and 20 mass% or less. It is preferable to use a composition containing Ag and unavoidable impurities in the balance. The thickness of the Ag-Cu-Ti brazing material 24 is preferably in the range of 2 μm or more and 10 μm or less.

(Heating step S02)
Next, while the copper plate 22 and the ceramic substrate 11 are pressurized, they are heated in a heating furnace in a vacuum atmosphere to melt the Ag-Ti brazing material (Ag-Cu-Ti brazing material) 24.
Here, the heating temperature in the heating step S02 is within the range of the eutectic point temperature of Cu and Si or more and 850 ° C. or less. Further, in this heating step S02, the temperature integral value at the above-mentioned heating temperature is set within the range of 1 ° C. · h or more and 110 ° C. · h or less.
The pressurizing load in the heating step S02 is within the range of 0.029 MPa or more and 2.94 MPa or less.

(Cooling step S03)
Then, after the heating step S02, the molten Ag-Ti-based brazing material (Ag-Cu-Ti-based brazing material) 24 is solidified by cooling.
The cooling rate in this cooling step S03 is preferably in the range of 2 ° C./min or more and 10 ° C./min or less.

Here, in the heating step S02 described above, a eutectic liquid phase is present at the grain boundary of TiN in the active metal compound layer 41, and this eutectic liquid phase is used as a diffusion path for Si and Ag on the ceramic substrate 11 side. -Ag, Cu, and Ti of the Cu-Ti brazing material 24 diffuse with each other, and the interfacial reaction of the ceramic substrate 11 is promoted.
As a result, the maximum indentation hardness in the region from 10 μm to 50 μm from the bonding interface with the ceramic substrate 11 toward the circuit layer 12 (metal layer 13) is within the range of ^{70 mgf / μm 2} or more and 150 mgf / μm ^{2 or less.}

As described above, the ceramic substrate 11 and the copper plates 22 and 23 are joined by the laminating step S01, the heating step S02, and the cooling step S03 to manufacture the insulated circuit board 10 according to the present embodiment.

(Heat sink joining step S04)
Next, the heat sink 30 is joined to the other surface side of the metal layer 13 of the insulating circuit board 10.
The insulating circuit board 10 and the heat sink 30 are laminated via a solder material and charged into a heating furnace, and the insulating circuit board 10 and the heat sink 30 are solder-bonded via the solder layer 32.

(Semiconductor element joining step S05)
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-mentioned steps.

According to the insulated circuit board 10 (copper / ceramics bonded body) of the present embodiment having the above configuration, the circuit layer 12 (metal layer) is formed from the bonding interface between the circuit layer 12 (metal layer 13) and the ceramics substrate 11. Since the maximum pushing hardness in the region from 10 μm to 50 μm to 13) is 70 mgf / μm ² or more, the copper near the bonding interface is sufficiently melted to form a liquid phase, and the ceramic substrate 11 and the circuit layer are formed. 12 (metal layer 13) is more firmly bonded.
On the other hand, since the above-mentioned maximum indentation hardness is ^{suppressed to 150 mgf / μm 2} or less, the vicinity of the bonding interface is not harder than necessary, and the occurrence of cracks at the time of a thermal cycle load can be suppressed.

In the insulating circuit substrate 10 of the present embodiment, the maximum particle diameter of the active metal compound particles 45 in the active metal compound layer 41 formed at the bonding interface between the ceramics substrate 11 and the circuit layer 12 (metal layer 13) is 180 nm or less. In some cases, the ratio of the grain boundary region composed of the metal phase having a relatively low hardness to the active metal compound layer 41 increases, and the impact resistance of the active metal compound layer 41 can be ensured. As a result, for example, when the terminal material is ultrasonically bonded to the circuit layer 12 (metal layer 13), the occurrence of cracks in the active metal compound layer 41 is suppressed, and the circuit layer 12 (metal layer 13) and the ceramic substrate 11 are separated. Further, it is possible to suppress the occurrence of cracks on the ceramic substrate 11.

Further, in the insulating circuit board 10 of the present embodiment, when Si, Cu, and Ag are present in the active metal compound layer 41, the occurrence of cracks in the active metal compound layer 41 can be suppressed. At the same time, an unreacted portion is not generated at the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13), and the insulating circuit board 10 having higher bonding strength can be obtained.

Although the embodiments of the present invention have been described above, the present invention is not limited to this, and can be appropriately changed without departing from the technical idea of the invention.
For example, in the present embodiment, the semiconductor element is mounted on the insulating circuit board to form the power module, but the present embodiment is not limited to this. For example, an LED element may be mounted on the circuit layer of the insulated circuit board to form an LED module, or a thermoelectric element may be mounted on the circuit layer of the insulated circuit board to form a thermoelectric module.

Further, in the insulated circuit board of the present embodiment, it has been described that the circuit layer and the metal layer are both composed of a copper plate made of copper or a copper alloy, but the present invention is not limited to this.
For example, if the circuit layer and the ceramic substrate are composed of the copper / ceramics joint of the present invention, the material and joining method of the metal layer are not limited, and the metal layer may not be present, or the metal layer may be aluminum or It may be composed of an aluminum alloy or a laminate of copper and aluminum.
On the other hand, as long as the metal layer and the ceramic substrate are made of the copper / ceramics joint of the present invention, the material and joining method of the circuit layer are not limited, and the circuit layer may be made of aluminum or an aluminum alloy. , It may be composed of a laminate of copper and aluminum.

Further, in the present embodiment, it has been described that the Ag-Ti brazing material (Ag-Cu-Ti brazing material) 24 is arranged between the copper plates 22 and 23 and the ceramic substrate 11 in the laminating step S01. However, the present invention is not limited to this, and a bonding material containing another active metal may be used.
Further, in the present embodiment, it is described that the ceramic substrate is composed of silicon nitride (Si 3 _{N 4),} it is not limited to this, which has been configured with other silicon-containing ceramics May be good.

The results of the confirmation experiment conducted to confirm the effect of the present invention will be described below.

(Example 1)
First, a ceramic substrate (40 mm × 40 mm × 0.32 mm) made of silicon nitride (Si ₃ N _{4) was prepared.}
A copper plate (37 mm × 37 mm × thickness 1.0 mm) made of oxygen-free copper was used on both sides of this ceramic substrate using an Ag—Cu based brazing material containing the active metal shown in Table 1 under the conditions shown in Table 1. An insulating circuit board (copper / ceramics bonded body) was obtained by joining a copper plate and a ceramics substrate. The degree of vacuum of the vacuum furnace at the time of joining was set to 5 × 10 ^-3 Pa.

With respect to the obtained insulating circuit board (copper / ceramics joint), the maximum indentation hardness near the joint interface and the reliability of the thermal cycle were evaluated as follows.

(Maximum indentation hardness near the bonding interface)
The maximum indentation hardness was measured in a region from 10 μm to 50 μm from the bonding interface between the copper plate and the ceramic substrate to the copper plate side using an indentation hardness tester (ENT-1100a manufactured by Elionix Inc.). The measurement conditions were F _max = 5000 mgf (number of divisions = 500, step interval = 20 ms) using a Berkovich indenter. The target cross section was exposed by buffing to form a measurement surface, and as shown in FIG. 7, the indentation hardness was measured at 50 measurement points at 10 μm intervals, and the maximum value of the indentation hardness was confirmed. bottom.
In this indentation hardness test, as shown in FIG. 8, the load applied in the indenter indentation process and the indentation depth can be continuously measured, and information such as plasticity / elasticity / creep can be obtained from the load-displacement curve. Can be obtained.

(Cold heat cycle reliability)
After holding in the following atmosphere, the bonding interface between the copper plate and the ceramic substrate was inspected by SAT inspection, and the presence or absence of cracks in the ceramic was determined.
-78 ° C x 2 min ← → 350 ° C x 2 min
Then, the number of crack occurrence cycles was evaluated. Those in which cracks were confirmed less than 6 times were evaluated as "x", and those in which cracks were not confirmed even after 6 times were evaluated as "○". The evaluation results are shown in Table 1.

In Comparative Example 1 in which Ti was used as the active metal and the integrated temperature in the heating step was 0.5 ° C. · h, the maximum indentation hardness of the bonding interface was 173 mgf / μm ^2, which was larger than the range of the present invention. The reliability of the cold cycle became "x".
In Comparative Example 2 in which Zr was used as the active metal and the integrated temperature value in the heating step was 0.7 ° C. · h, the maximum indentation hardness of the bonding interface was 160 mgf / μm ^2, which was larger than the range of the present invention. The reliability of the cold cycle became "x".

On the other hand, in Reference Example 1-8 in which the maximum indentation hardness of the bonding interface was within the range of ^{70 mgf / μm 2} or more and 150 mgf / μm ² or less, the thermal cycle reliability was high regardless of the type of active metal. It became "○".

(Example 2)
A ceramic substrate (40 mm × 40 mm × 0.32 mm) made of silicon nitride (Si ₃ N _{4) was prepared.}
A copper plate (37 mm × 37 mm × thickness 0.2 mm) made of oxygen-free copper was used on both sides of this ceramic substrate using an Ag—Cu based brazing material containing the active metal shown in Table 2 under the conditions shown in Table 2. An insulating circuit board (copper / ceramics bonded body) was obtained by joining a copper plate and a ceramics substrate. The degree of vacuum of the vacuum furnace at the time of joining was set to 5 × 10 ^-3 Pa.

With respect to the obtained insulating circuit board (copper / ceramics joint), the maximum indentation hardness in the vicinity of the joint interface was evaluated by the same method as in Example 1.
In addition, the maximum particle size of the active metal compound particles in the active metal compound layer, the presence or absence of Si, Ag, and Cu in the active metal compound layer, and ultrasonic bonding were evaluated by the methods shown below.

(Maximum particle size of active metal compound particles)
The active metal compound layer was observed with a transmission electron microscope (Titan ChemiSTEM manufactured by FEI) at a magnification of 500,000 times to obtain a HAADF image.
The equivalent circle diameter of the active metal compound particles was calculated by image analysis of this HAADF image. From the results of image analysis in 10 fields of view, the maximum circle-equivalent diameter of the observed active metal compound particles is shown in Table 2 as the maximum particle diameter.

(Presence or absence of Si, Ag, Cu in the active metal compound layer)
Grain boundaries in the active metal compound layer were integrated using a transmission electron microscope (Titan ChemiSTEM manufactured by FEI) at an acceleration voltage of 200 kV, a magnification of 500,000 to 700,000 times, and 1100 frames at 7 μs per point. In the EDS spectrum, when Si, Ag and Cu were 0.15 cps / eV, Si, Ag and Cu were evaluated as "yes".

(Evaluation of ultrasonic bonding)
Using an ultrasonic metal bonding machine (manufactured by Ultrasonic Engineering Co., Ltd .: 60C-904) for an insulated circuit board, a copper terminal (10 mm x 20 mm x 2.0 mm thickness) was loaded with a load of 850 N and a coplus amount of 0.7 mm. , Ultrasonic bonding was performed under the condition of bonding area 5 mm × 5 mm. In addition, 50 copper terminals were joined to each.
After joining, the bonding interface between the copper plate and the ceramic substrate was inspected using an ultrasonic flaw detector (FineSAT200 manufactured by Hitachi Solutions, Ltd.). "D" was observed for peeling or cracking of the copper plate and the ceramic substrate in 5 or more out of 50, and peeling or cracking of the ceramic substrate was observed in 3 or more and 4 or less out of 50. "C" for all 50 pieces, "B" for 1 to 2 out of 50 pieces where peeling or ceramic cracking between the copper plate and ceramic substrate was observed, and "B" for all 50 pieces. Those in which no cracks were observed were evaluated as "A". The evaluation results are shown in Table 2.

Comparing Examples 11-13 of the present invention in which the active metal is Ti, Examples 14-16 of the present invention in which the active metal is Hf, Examples 17 and 18 of the present invention in which the active metal is Zr, and Reference Example 19, respectively, the active metal compound. It is confirmed that by reducing the maximum particle size of the active metal compound particles in the layer, it is possible to suppress the peeling of the copper plate and the ceramic substrate during ultrasonic bonding and the occurrence of cracks in the ceramic substrate.

As a result of the above, according to the example of the present invention, a copper / ceramics bonded body and an insulating circuit board, which have high bonding strength, are less likely to crack in the ceramic substrate even under a thermal cycle load, and have particularly excellent thermal cycle reliability. It was confirmed that it is possible to provide.

10 Insulated circuit board (copper / ceramic joint)
11 Ceramic substrate (ceramic member)
12 Circuit layer (copper member)
13 Metal layer (copper member)
41 Active metal compound layer 45 Active metal compound particles

Claims (4)

A copper / ceramics joint formed by joining a copper member made of copper or a copper alloy and a ceramics member made of silicon-containing ceramics.
The maximum indentation hardness measured using a Berkovich indenter in the region from 10 μm to 50 μm from the bonding interface between the copper member and the ceramic member to the copper member side is within the range of 110 mgf / μm ² or more and 150 mgf / μm ^{2 or less.} And
At the bonding interface between the ceramic member and the copper member, an active metal compound layer containing one or more active metal compounds selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side. Has been
A copper / ceramics conjugate in which the maximum particle size of the active metal compound particles in the active metal compound layer is 180 nm or less. The copper / ceramics conjugate according to claim 1, wherein Si, Cu, and Ag are present in the active metal compound layer. 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 made of silicon-containing ceramics.
The maximum indentation hardness measured using a Berkovich indenter in the region from 10 μm to 50 μm from the bonding interface between the copper plate and the ceramic substrate to the copper plate side is within the range of 110 mgf / μm ² or more and 150 mgf / μm ^{2 or less.} ,
At the bonding interface between the copper plate and the ceramic substrate, an active metal compound layer containing one or more active metal compounds selected from Ti, Zr, Nb, and Hf is formed on the ceramic substrate side. And
An insulating circuit board characterized in that the maximum particle size of the active metal compound particles in the active metal compound layer is 180 nm or less. The insulating circuit board according to claim 3, wherein Si, Cu, and Ag are present in the active metal compound layer.

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