JP2023044869A - Copper/ceramic joint 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 a copper member (12) made of copper or a copper alloy and a ceramic member (11) are joined together, wherein Cu is present at the joint interface between the ceramic member (11) and the copper member (12). A Mg solid-solution layer 31 in which Mg is solid-dissolved in the matrix is formed, and the maximum value of the indentation hardness in the region E1 from 20 μm to 50 μm from the bonding surface of the ceramic member 11 to the copper member 12 side is 90 mgf/. It is within the range of μm 2 or more and 150 mgf/μm 2 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 Literature 1 proposes an insulated circuit board in which a circuit layer and a metal layer are formed by joining copper plates to one surface and the other surface of a ceramic substrate. In this 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). In this active metal brazing method, since a brazing filler metal containing Ti, which is an active metal, is used, the wettability between the molten brazing filler metal and the ceramic substrate is improved, and the ceramic substrate and the copper plate are joined well. It will be.

Further, Patent Document 2 proposes an insulated circuit board in which a ceramic substrate and a copper plate are joined using a Cu--Mg--Ti based brazing material.
In this patent document 2, it is configured to be joined by heating at 560 to 800 ° C. in a nitrogen gas atmosphere, and Mg in the Cu-Mg-Ti alloy sublimates and does not remain at the joint interface. and substantially no titanium nitride (TiN) is formed.

Furthermore, Patent Document 3 discloses an insulated circuit board in which a copper plate and a ceramic substrate are joined using Mg.
In Patent Document 3, even when terminals and the like are ultrasonically bonded, it is possible to suppress the occurrence of cracks at the bonded interface between the copper plate and the ceramic substrate.

Japanese Patent No. 3211856 Japanese Patent No. 4375730 Japanese Patent Application Laid-Open No. 2021-035901

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 disclosed in Patent Documents 1 and 2, when a copper plate and a ceramic substrate are bonded using a bonding material containing Ti, which is an active metal, Ti, which is an active metal, diffuses into the copper plate side. However, the precipitation of intermetallic compounds containing Cu and Ti makes the vicinity of the joint interface hard, and cracks may occur in the ceramic member during a thermal cycle load, resulting in a decrease in thermal cycle reliability.

Further, as disclosed in Patent Document 3, when a ceramic substrate and a copper plate are joined using Mg, Mg is solid-dissolved in the parent phase of Cu at the joint interface between the ceramic substrate and the copper plate. A Mg solid solution layer is formed. Therefore, the vicinity of the bonding surface of the copper plate becomes hard due to solid-solution hardening of Mg.
Furthermore, oxygen present at the bonding interface reacts with Mg to precipitate Mg oxide in the Mg solid-solution layer, and this precipitation hardening may further harden the bonding interface.
As described above, even when the ceramic substrate and the copper plate are joined using Mg without using Ti, which is an active metal, the joint interface becomes hard, and there is a possibility that the thermal cycle reliability cannot be sufficiently improved. rice field.

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 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 together, the ceramic member and At the joint interface with the copper member, an Mg solid-solution layer in which Mg is solid-dissolved in the Cu matrix is formed. It is characterized in that the maximum value of indentation hardness is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less.

The indentation hardness H in the present invention is the load when a test load of 5000 mgf is applied using a triangular pyramidal diamond indenter called a Berkovich indenter with an inter-ridge angle of 114.8° or more and 115.1° or less. - Measure the correlation of displacement and calculate from the following formula.
hc = ht - 0.75 x P/S
(ht: indentation depth, P: load, S: contact stiffness (=dP/dh|Pmax), hc: contact depth)
Contact area A = 24.56 x ^hc2
Indentation hardness H = P/A

According to the copper/ceramic joined body of the present invention, an Mg solid-solution layer in which Mg is solid-dissolved in a Cu parent phase is formed at the joint interface between the ceramic member and the copper member, and the ceramic member The maximum value of the indentation hardness in the region from 20 μm to 50 μm from the joint surface to the copper member side is 90 mgf / μm ² or more, so the copper in the vicinity of the joint interface is sufficiently melted to generate a liquid phase. The ceramic member and the copper member are firmly joined together.
On the other hand, since the maximum value of the indentation hardness in the above-mentioned region is suppressed to 150 mgf/μm ² or less, the vicinity of the joint interface is not unnecessarily hard, and the occurrence of cracks under thermal cycle load can be suppressed. .
Therefore, it is possible to obtain a copper/ceramic bonded body having high bonding strength and particularly excellent thermal cycle reliability.

Here, in the copper/ceramic joined body of the present invention, the average value of indentation hardness in a region from 20 μm to 50 μm from the joint surface of the ceramic member to the copper member side is 80 mgf/μm ² or more and 140 mgf/μm ² It is preferable to be within the following range.
In this case, the average value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic member to the copper member side is in the range of 80 mgf/μm ² or more and 140 mgf/μm ² or less. Thus, the ceramic member and the copper member are reliably and firmly joined, and hardening of the joining interface is further suppressed.
Therefore, it is possible to obtain a copper/ceramic bonded body having high bonding strength and particularly excellent thermal cycle reliability.

Further, in the copper/ceramic joined body of the present invention, the indentation hardness in a region of 10 μm or more and 30 μm or less from the surface of the copper member joined to the ceramic member opposite to the ceramic member to the ceramic member side is preferably in the range of 70 mgf/μm ² or more and 85 mgf/μm ² or less.
In this case, since the average value of the indentation hardness in the region of 10 μm or more and 30 μm or less from the surface of the copper member opposite to the ceramic member is in the range of 70 mgf/μm ² or more and 85 mgf/μm ² or less. , the entire copper member is not hardened, and when other members are joined to the surface of this copper member, the reliability of joining with these other members can be improved.

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 a parent phase of Cu. A Mg solid-solution layer in which Mg is solid-dissolved is formed therein, and the maximum value of indentation hardness in a region from 20 μm to 50 μm from the joint surface of the ceramic substrate to the copper plate side is 90 mgf/μm ² or more and 150 mgf/ It is characterized by being in the range of μm ² or less.

According to the insulated circuit board of the present invention, a Mg solid-solution layer in which Mg is solid-dissolved in a Cu parent phase is formed at the bonding interface between the ceramic substrate and the copper plate, and the bonding surface of the ceramic substrate to the copper plate side, the maximum value of the indentation hardness in the region from 20 μm to 50 μm is 90 mgf/μm ² or more, so the copper in the vicinity of the bonding interface is sufficiently melted to generate a liquid phase, and the ceramics The substrate and the copper plate are firmly bonded.
On the other hand, since the maximum value of the indentation hardness in the above-mentioned region is suppressed to 150 mgf/μm ² or less, the vicinity of the joint interface is not unnecessarily hard, and the occurrence of cracks under 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.

Here, in the insulating circuit board of the present invention, the average value of indentation hardness in a region from 20 μm to 50 μm from the joint surface of the ceramic substrate to the copper plate side is in the range of 80 mgf/μm ² or more and 140 mgf/μm ² or less. preferably within.
In this case, the average value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 80 mgf/μm ² or more and 140 mgf/μm ² or less. The ceramic substrate and the copper plate are reliably and strongly bonded, and hardening of the bonding interface is further 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 board of the present invention, the average value of indentation hardness in a region of 10 μm or more and 30 μm or less from the surface of the copper plate bonded to the ceramic substrate opposite to the ceramic substrate to the ceramic substrate side. is preferably in the range of 70 mgf/μm ² or more and 85 mgf/μm ² or less.
In this case, since the average value of the indentation hardness in the region of 10 μm or more and 30 μm or less from the surface of the copper plate opposite to the ceramic substrate is in the range of 70 mgf/μm ² or more and 85 mgf/μm ² or less, The entire copper plate is not hardened, and when other members are joined to the surface of this copper plate, the reliability of joining with these other members can be improved.

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; 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.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
The copper/ceramic joined body according to the present embodiment includes a ceramic substrate 11 as a ceramic 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 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 22 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 22 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 23 made of copper or a copper alloy to the other surface (lower surface in FIG. 4) of the ceramic substrate 11. As shown in FIG.
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 23 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, at the bonding interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13), as shown in FIG. .
The Mg solid-solution layer 31 is formed by exposing the bonding interface between the circuit layer 12 (metal layer 13) and the ceramic substrate 11 using an EPMA apparatus (JXA-8539F manufactured by JEOL Ltd.) at a magnification of 200 and an acceleration voltage of 15 kV. Quantitative analysis is performed by observing a region (400 μm long × 600 μm wide) including the bonding interface, and the Mg concentration is 0.01 atomic % or more and 6.9 atomic % or less, where Cu concentration + Mg concentration = 100 atomic %. is.

Then, in the insulating circuit board 10 of the present embodiment, as shown in FIG. is within the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less.
Further, in the present embodiment, the average value of the indentation hardness in the region E1 is preferably within the range of 80 mgf/μm ² or more and 140 mgf/μm ² or less.

In this embodiment, the circuit layer 12 formed on one surface of the ceramics substrate 11 and the metal layer 13 formed on the other surface of the ceramics substrate 11 are separated from the surface of the ceramics substrate 11 opposite to the surface of the ceramics substrate 11 . It is preferable that the average value of the indentation hardness in the region E2 of 10 μm or more and 30 μm or less toward the 11 side is in the range of 70 mgf/μm ² or more and 85 mgf/μm ² 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.

(Mg placement step S01)
First, a ceramic substrate 11 is prepared, and as shown in FIG. Place Mg.
In this embodiment, Mg foils 25 are arranged between the copper plate 22 forming the circuit layer 12 and the ceramic substrate 11 and between the copper plate 23 forming the metal layer 13 and the ceramic substrate 11 .
Here, in the Mg placement step S01, the amount of Mg to be placed is set within the range of 0.34 mg/cm ² or more and 4.35 mg/cm ² or less.
The amount of Mg to be arranged is preferably 0.52 mg/cm ² or more, more preferably 0.69 mg/cm ² or more. On the other hand, the amount of Mg disposed is preferably 3.48 mg/cm ² or less, more preferably 2.61 mg/cm ² or less.

(Lamination step S02)
Next, the copper plate 22 and the ceramic substrate 11 are laminated with the Mg foil 25 interposed therebetween, and the ceramic substrate 11 and the copper plate 23 are laminated with the Mg foil 25 interposed therebetween.

(Joining step S03)
Next, the laminated copper plate 22, Mg foil 25, ceramic substrate 11, Mg foil 25, and copper plate 23 are pressed in the direction of lamination, and placed in a vacuum furnace for heating. The copper plate 23 is joined.

Here, the holding temperature in the bonding step S03 is preferably within the range of 700° C. or higher and 850° C. or lower. The temperature integral value S in the heating process from 670° C. to the holding temperature and the holding process at the heating temperature is preferably in the range of 30° C.·h or more and 500° C./h or less.
Moreover, the pressure load P in the joining step S03 is preferably in the range of 0.09 MPa or more and 1.96 MPa or less.

Further, the product P×S of the pressure load P and the temperature integral value S is preferably within the range of 30° C.·h·MPa or more and 650° C.·h·MPa or less.
By setting the product P×S of the pressure load P and the temperature integral value S within the above range, the discharge state of the liquid phase generated during bonding is adjusted, and the diffusion state of Mg to the copper plates 22 and 23 is controlled. becomes possible.

Furthermore, it is preferable that the degree of vacuum in the furnace in the bonding step S03 is in the range of 1×10 ⁻⁶ Pa or more and 5×10 ⁻² Pa or less.
Also, the cooling rate during cooling is preferably in the range of 2° C./min or more and 20° C./min or less. The cooling rate here is the average value of the cooling rate from the holding temperature to 670°C.

As described above, the insulating 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 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 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-described steps.

According to the insulated circuit board 10 (copper/ceramic bonded body) of the present embodiment configured as described above, the bonded interface between the ceramic substrate 11 and the circuit layer 12 (metal layer 13) has a parent phase of Cu. A Mg solid-solution layer 31 in which Mg is solid-dissolved is formed therein, and the maximum value of indentation hardness in a region E1 from 20 μm to 50 μm from the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) side. is 90 mgf/μm ² or more, the copper in the vicinity of the bonding interface is sufficiently melted to generate a liquid phase, and the ceramic substrate 11 and the circuit layer 12 (metal layer 13) are firmly bonded. .
On the other hand, since the maximum value of the indentation hardness in the aforementioned region E1 is suppressed to 150 mgf/μm ² or less, the vicinity of the joint interface is not unnecessarily hard, and the occurrence of cracks during thermal cycle load can be suppressed. can.
Therefore, it is possible to obtain the insulated circuit board 10 having high bonding strength and particularly excellent thermal cycle reliability.

In order to further improve the thermal cycle reliability, the maximum value of the indentation hardness in the region E1 from 20 μm to 50 μm from the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) side is set to 145 mgf/μm. It is preferably ² or less, more preferably 135 mgf/μm ² or less.
On the other hand, in order to more reliably bond the ceramic substrate 11 and the circuit layer 12 (metal layer 13), the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) is 20 μm to 50 μm in the region E1. The maximum value of indentation hardness is preferably 100 mgf/μm ² or more, more preferably 110 mgf/μm ^{2 or} more.

In addition, in the insulating circuit board 10 of the present embodiment, the average value of the indentation hardness in the region E1 from 20 μm to 50 μm from the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) side is 80 mgf/μm ² or more. When it is within the range of 140 mgf/μm ² or less, the ceramic substrate 11 and the circuit layer 12 (metal layer 13) are reliably and strongly bonded by Mg, and the bonded interface is further hardened. Suppressed.
Therefore, it is possible to obtain the insulated circuit board 10 having high bonding strength and particularly excellent thermal cycle reliability.

In addition, the lower limit of the average value of the indentation hardness in the region E1 from 20 μm to 50 μm from the bonding surface of the ceramic substrate 11 to the circuit layer 12 (metal layer 13) side is more preferably 85 mgf/μm ² or more. More preferably, it is 90 mgf/μm ² or more. Further, the upper limit of the average indentation hardness in the region E1 is more preferably 135 mgf/μm ² or less, and further preferably 125 mgf/μm ² or less.

Furthermore, in the insulating circuit board 10 of the present embodiment, the average indentation hardness in the region E2 of 10 μm or more and 30 μm or less from the surface of the circuit layer 12 (metal layer 13) opposite to the ceramic substrate 11 toward the ceramic substrate 11 When the value is in the range of 70 mgf/μm ² or more and 85 mgf/μm ² or less, the entire circuit layer 12 (metal layer 13) is not hardened, and the surface of this circuit layer 12 (metal layer 13) It is possible to improve the reliability of bonding with these other members when other members are joined to the .

In addition, the upper limit of the average value of the indentation hardness in the region E2 of 10 μm or more and 30 μm or less from the surface of the circuit layer 12 (metal layer 13) opposite to the ceramic substrate 11 toward the ceramic substrate 11 is 83 mgf/μm ² or less. is more preferably 80 mgf/μm ² 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, 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.
Further, in the present embodiment, the Mg foil is arranged between the ceramic substrate and the copper plate, but the present invention is not limited to this, and the bonding material may be arranged between the ceramic substrate and the copper plate. Alternatively, Mg may be provided on the bonding surface of the ceramic substrate, or Mg may be provided on the bonding surface of the copper plate. Alternatively, Mg may be placed on the ceramic substrate and/or copper plate by sputtering or vapor deposition. A clad material of copper plate and Mg foil can also be used. A paste containing Mg powder and/or MgH ₂ powder can be used to dispose Mg between the ceramic substrate and the copper plate.

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.

Then, the copper plate and the ceramic substrate were bonded under the conditions shown in Table 1 to obtain the insulated circuit substrates (copper/ceramic bonded bodies) of Inventive Examples 1 to 9 and Comparative Example 1. The degree of vacuum in the vacuum furnace during bonding was set to 2×10 ⁻³ Pa.

The obtained insulated circuit board (copper/ceramic bonded body) was evaluated for indentation hardness and thermal cycle reliability (cracking of ceramic substrate, bonding rate after thermal cycle load) as follows.

(indentation hardness)
The obtained insulated circuit board (copper/ceramic bonded body) was cut in the lamination direction, and at the bonding interface between the ceramic substrate and the circuit layer and the metal layer, the distance from the bonding surface of the ceramic substrate to the circuit layer and the metal layer was 20 μm to 50 μm. The indentation hardness in the region E1 was measured and calculated at 4 points in each field of view and 4 points in 5 fields of view in total, and the maximum and average values were obtained.
In addition, the indentation hardness in the region E2 of 10 μm or more and 30 μm or less from the surface of the circuit layer and the metal layer on the opposite side of the ceramic substrate to the ceramic substrate side was measured at 4 points in each field of view, and at 40 points in total of 5 fields of view. was measured and the average value was calculated.

(Cold/heat cycle reliability)
Using a thermal shock tester (TSA-72ES manufactured by Espec Co., Ltd.), the insulating circuit board described above was subjected to a thermal cycle in the gas phase, and the presence or absence of cracks in the ceramics was determined by SAT inspection. In addition, the conditions of the thermal cycle were set as follows according to the material of the ceramic substrate.
For AlN, Al ₂ O ₃ : −40° C.×15 min←→150° C.×15 min, SAT inspection every 100 cycles up to 1000 cycles.
For Si ₃ N ₄ : −40° C.×15 min←→150° C.×15 min, SAT inspection every 200 cycles up to 3000 cycles.

(bonding rate)
The bonding rate before the thermal cycle load and the bonding rate after the thermal cycle load were evaluated as follows. In addition, when the crack of the ceramics substrate was confirmed, the bonding rate at that time was evaluated.
For the insulated circuit board, the bonding rate at the interface between the ceramic substrate and the copper plate (circuit layer and metal layer) was evaluated using an ultrasonic flaw detector (FineSAT FSP8V manufactured by Hitachi Power Solutions Co., Ltd.). was calculated.

Here, the initial bonding area is the area to be bonded before bonding, that is, the area (37 mm×37 mm) of the circuit layer and the metal layer in this example.
(bonding rate) = {(initial bonding area) - (peeling area)}/(initial bonding area)
In the image obtained by binarizing the ultrasonic flaw detection image, peeling is indicated by a white portion in the joint portion, so the area of this white portion was defined as the peeling area.

First, invention examples 1-3 using AlN as a ceramic substrate and comparative examples 1 and 2 are compared.
In Comparative Example 1, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is 86.3 mgf/μm ² , and the number of cracks generated in the thermal cycle test is 300. , and the bonding rate after the thermal cycle load was as low as 64.5%.
In Comparative Example 2, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is 170.5 mgf/μm ² , and the number of cracks generated is 200 in the thermal cycle test. times.

On the other hand, in Examples 1-3 of the present invention, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less. In the thermal cycle test, the number of cracks occurred 700 to 1000 times, and the bonding rate after the thermal cycle load was 90.6 to 98.9%, 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 value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is 87.3 mgf/μm ² , and the number of cracks generated in the thermal cycle test is 1200. , and the bonding rate after the thermal cycle load was as low as 52.5%.
In Comparative Example 4, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the joint surface of the ceramic substrate to the copper plate side is 179.1 mgf/μm ² , and the number of cracks generated in the thermal cycle test is 1400. times.

On the other hand, in Examples 4-6 of the present invention, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less. In the thermal cycle test, the number of cracks occurred exceeded 2400 to 3000 times, and the bonding rate after the thermal cycle load was 95.4 to 97.9%, 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 value of the indentation hardness in the region from 20 μm to 50 μm from the joint surface of the ceramic substrate to the copper plate side is 158.2 mgf/μm ² , and the number of cracks generated is 300 in the thermal cycle test. times.

On the other hand, in Examples 7 and 8 of the present invention, the maximum value of the indentation hardness in the region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less. In the thermal cycle test, the number of cracks occurred 800 to 900 times, and the bonding rate after the thermal cycle load was 96.5 to 97.7%, 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)
31 Mg solid solution layer

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 Mg solid-solution layer in which Mg is solid-dissolved in a Cu parent phase is formed at the bonding interface between the ceramic member and the copper member,
The maximum value of indentation hardness in a region from 20 μm to 50 μm from the bonding surface of the ceramic member to the copper member side is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less. / ceramic joints. An average value of indentation hardness in a region from 20 μm to 50 μm from the bonding surface of the ceramic member to the copper member side is set within a range of 80 mgf/μm ² or more and 140 mgf/μm ² or less. Item 1. A copper/ceramic joined body according to item 1. The average value of indentation hardness in a region of 10 μm or more and 30 μm or less from the surface of the copper member joined to the ceramic member opposite to the ceramic member toward the ceramic member is 70 mgf/μm ² or more and 85 mgf/μm 3. A copper/ceramic joined body according to claim ¹ or 2, characterized in that it is within the range of 2 or less. An insulated circuit board formed by bonding a copper plate made of copper or a copper alloy to the surface of a ceramic substrate,
An Mg solid-solution layer in which Mg is solid-dissolved in a Cu parent phase is formed at the bonding interface between the ceramic substrate and the copper plate,
An insulation circuit characterized in that a maximum value of indentation hardness in a region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 90 mgf/μm ² or more and 150 mgf/μm ² or less. substrate. 2. An average value of indentation hardness in a region from 20 μm to 50 μm from the bonding surface of the ceramic substrate to the copper plate side is in the range of 80 mgf/μm ² or more and 140 mgf/μm ² or less. 5. The insulating circuit board according to 4. The average value of indentation hardness in a region of 10 μm or more and 30 μm or less from the surface of the copper plate bonded to the ceramic substrate opposite to the ceramic substrate toward the ceramic substrate is 70 mgf/μm ² or more and 85 mgf/μm ^{2 or more} . 6. The insulated circuit board according to claim 4, wherein the following range is satisfied.

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