JP7552282B2 - Ceramics/copper/graphene bonded body, its manufacturing method, and ceramics/copper/graphene bonded structure - Google Patents

Description

This invention relates to a ceramic/copper/graphene bonded structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded together, a method for producing the same, and a ceramic/copper/graphene bonded structure.

A graphene-containing carbonaceous material containing graphene aggregates has excellent thermal conductivity and is therefore particularly suitable as a material for forming a heat dissipation member, a heat conduction member, or the like.
For example, by forming an insulating layer made of ceramics or the like on the surface of the graphene-containing carbonaceous member containing the above-mentioned graphene aggregates, it becomes possible to use the graphene-containing carbonaceous member as an insulating substrate.

For example, Patent Document 1 discloses an anisotropic heat conduction element having a structure in which graphene sheets are stacked along a first direction and an intermediate member (copper plate) joined to an end face of the structure in a second direction intersecting the first direction, with the intermediate member being pressure-bonded to the end face via an insert material containing at least titanium.

JP 2012-238733 A

Incidentally, the insulating substrate may be subjected to thermal cycles in the environment in which it is used. In particular, in recent years, the insulating substrate may be used in harsh environments such as engine compartments, and may be subjected to thermal cycles under severe conditions with large temperature differences.
In the above-mentioned Patent Document 1, the copper intermediate and the graphene structure are joined via an insert material containing titanium. However, depending on the joining conditions, the copper intermediate and the graphene structure cannot be firmly joined, and there is a risk of peeling when subjected to severe thermal cycles.

In addition, when the copper/graphene bonded body of Patent Document 1 is installed as a heat dissipation member on a specific device, the conductive copper intermediate body comes into contact with the device, and current may flow into the bonded portion through this intermediate body, which may cause the bond between the copper intermediate body and the graphene structure to not be able to be maintained.

The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a ceramic/copper/graphene bonded body in which a copper member made of copper or a copper alloy and a graphene-containing carbonaceous member containing graphene aggregates are firmly bonded, the current flowing through the bonded portion can be suppressed, peeling does not occur even when subjected to thermal cycle loads, and the bonded body has excellent thermal cycle reliability, and a method for manufacturing the same.

In order to solve such problems and achieve the above-mentioned object, the ceramic/copper/graphene bonded body of the present invention is a ceramic/copper/graphene bonded body having a structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded together, and is characterized in that at the bonding interface between the copper member and the graphene-containing carbonaceous member, an active metal carbide layer containing carbides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the graphene-containing carbonaceous member side, and an Mg solid solution layer in which Mg is dissolved in a Cu matrix is formed between this active metal carbide layer and the copper member.

In the ceramic/copper/graphene bonded body having this configuration, an active metal carbide layer is formed on the bonding surface of the graphene-containing carbonaceous member at the bonding interface between the copper member and the graphene-containing carbonaceous member, and an Mg solid solution layer in which Mg is dissolved in the Cu matrix is formed on the bonding surface side of the copper member. As a result, Mg in the Mg solid solution layer sufficiently reacts with the active metal in the active metal carbide layer, and the copper member is firmly bonded to the graphene-containing carbonaceous material via this active metal carbide layer, so that cracks and peeling can be suppressed at the bonding interface during thermal cycle loading. Furthermore, since the ceramic/copper/graphene bonded body having this configuration contains copper as a constituent material, it has the function of efficiently dissipating heat as a heat spreader during transitional periods.

Moreover, in the ceramic/copper/graphene bonded body having this configuration, the copper member having electrical conductivity is covered with the ceramic member. Therefore, when the ceramic/copper/graphene bonded body is brought into contact with a predetermined device, a current is prevented from flowing into the bonded portion through the copper member, and the bond between the copper member and the graphene-containing carbonaceous member can be maintained.
Therefore, the ceramic/copper/graphene bonded body having this configuration can maintain stable heat dissipation characteristics while suppressing the occurrence of peeling at the bonded interface due to thermal cycles, and can achieve high reliability.

In the ceramic/copper/graphene joint of the present invention, it is preferable that the Mg solid solution layer contains a Cu-Mg intermetallic compound phase made of an intermetallic compound containing Cu and Mg.
In this case, the Cu--Mg intermetallic compound phase is distributed on the bonding surface side with the active metal carbide layer and is significantly involved in the bonding, thereby increasing the strength of the bond with the active metal carbide layer.

When the area of the Mg solid solution layer within a range of 50 μm from the boundary between the active metal carbide layer and the Mg solid solution layer toward the copper member side is defined as A, and the area of the Cu-Mg intermetallic compound phase is defined as B, it is preferable that the ratio B/A is 0.3 or less.

In the ceramic/copper/graphene joint of the present invention, it is preferable that a second intermetallic compound phase made of an intermetallic compound containing Cu and the active metal is present in the Mg solid solution layer.
In this case, the second intermetallic compound phase is distributed on the bonding surface side with the active metal carbide layer and is significantly involved in bonding, so that the strength of the bond with the active metal carbide layer can be increased.

In the ceramic/copper/graphene bonded body of the present invention, the ceramic member may be made of an oxygen-containing ceramic, and a magnesium oxide layer may be formed on the ceramic member side at a bonding interface between the ceramic member and the copper member.
In this case, the formation of the magnesium oxide layer can strengthen the bond between the oxygen-containing ceramic member and the copper member, and can suppress the occurrence of cracks and peeling at the bond interface when subjected to thermal cycle loading.

In the ceramic/copper/graphene bonded body of the present invention, the ceramic member may be made of a nitrogen-containing ceramic, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf may be formed on the ceramic member side at the bonding interface between the ceramic member and the copper member.
In this case, by forming an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf, the bond between the nitrogen-containing ceramic member and the copper member can be strengthened, and cracks and peeling can be suppressed from occurring at the bond interface when subjected to thermal cycle loading.

Furthermore, in the ceramic/copper/graphene bonded body of the present invention, it is preferable that the graphene-containing carbonaceous member includes graphene aggregates formed by deposition of single or multiple layers of graphene and flat graphite particles, the flat graphite particles are stacked using the graphene aggregates as a binder such that basal planes of the flat graphite particles are folded over, and the basal planes of the flat graphite particles are oriented in one direction.
In this case, it is possible to further improve the thermal conductivity characteristics of the graphene-containing carbonaceous member.

The method for producing a ceramic/copper/graphene bonded body of the present invention is a method for producing the above-mentioned ceramic/copper/graphene bonded body, and includes a copper/graphene bonding step of bonding the copper member and the graphene-containing carbonaceous member, and a copper/ceramic bonding step of bonding the copper member and the ceramic member, the copper/graphene bonding step including an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf and Mg between the copper member and the graphene-containing carbonaceous member, a lamination step of laminating the copper member and the graphene-containing carbonaceous member with the active metal and Mg interposed therebetween, and a bonding step of bonding the copper member and the graphene-containing carbonaceous member laminated with the active metal and Mg interposed therebetween by heat treatment in a vacuum atmosphere while applying pressure in a lamination direction, and the active metal and Mg arranging step includes a step of bonding the copper member and the ^graphene -containing carbonaceous member laminated with the active metal and Mg interposed therebetween by applying pressure in a lamination direction, and It is characterized in that the number is ² or more.

According to the method for producing a ceramic/copper/graphene bonded body having this configuration, in the active metal and Mg arranging step, the amount of active metal is set to 0.4 μmol/cm2 or ^more , and the amount of Mg is set to 14 μmol/cm2 or ^more , so that a sufficient liquid phase necessary for the interface reaction can be obtained, thereby ensuring bonding between the copper member and the graphene-containing carbonaceous material.

Here, in the method for producing a ceramic/copper/graphene bonded body of the present invention, it is preferable that a pressurized load in the bonding step is in the range of 0.049 MPa or more and 1.96 MPa or less, and a heating temperature in the bonding step is in the range of 700° C. or more and 950° C. or less.
In this case, in the joining process, the pressure load is set within the range of 0.049 MPa or more and 1.96 MPa or less, and the heating temperature is set within the range of 700°C or more and 950°C or less, so that the liquid phase necessary for the interfacial reaction can be maintained and a uniform interfacial reaction can be promoted.

In the method for producing a ceramic/copper/graphene bonded body of the present invention, in the copper/ceramic bonding step, it is preferable that one or more active metals selected from Ti, Zr, Nb and Hf, and Mg are disposed between the copper member and the ceramic member, and the copper member and the graphene-containing carbonaceous member stacked via the active metal and the Mg are bonded to each other by heat treatment in a vacuum atmosphere while being pressurized in a stacking direction.
In this case, one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg are used as bonding materials, which strengthens the bond between the copper member and the ceramic member, thereby making it possible to suppress cracks and peeling at the bonding interface when subjected to thermal cycle loading.

In the method for producing a ceramic/copper/graphene bonded body of the present invention, in the copper/ceramic bonding step, it is preferable that Mg is disposed between the copper member and the ceramic member, and the copper member and the graphene-containing carbonaceous member stacked via the Mg are bonded to each other by heat treatment in a vacuum atmosphere while being pressurized in a stacking direction.
In this case, Mg is used as the bonding material, which strengthens the bond between the copper member and the ceramic member, making it possible to suppress the occurrence of cracks and peeling at the bonding interface when subjected to thermal cycles.

The ceramic/copper/graphene bonding structure of the present invention is a ceramic/copper/graphene bonding structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded together, and is characterized in that at the bonding interface between the copper member and the graphene-containing carbonaceous member, an active metal carbide layer containing carbides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the graphene-containing carbonaceous member side, and an Mg solid solution layer in which Mg is dissolved in a Cu matrix is formed between the active metal carbide layer and the copper member.

In this ceramic/copper/graphene bonding structure, an active metal carbide layer is formed on the bonding surface of the graphene-containing carbonaceous member at the bonding interface between the copper member and the graphene-containing carbonaceous member, and an Mg solid solution layer in which Mg is dissolved in the Cu matrix is formed on the bonding surface side of the copper member. As a result, Mg in the Mg solid solution layer sufficiently reacts with the active metal in the active metal carbide layer, and the copper member is firmly bonded to the graphene-containing carbonaceous material via this active metal carbide layer, so that cracks and peeling can be suppressed at the bonding interface during thermal cycle loading. Furthermore, since this ceramic/copper/graphene bonding structure contains copper as a constituent material, it has the function of efficiently dissipating heat as a heat spreader during transitional periods.

Moreover, in the ceramic/copper/graphene bonding structure having this configuration, the copper member having electrical conductivity is covered with the ceramic member. Therefore, when the structure is brought into contact with a specific device, a current is prevented from flowing into the bonding portion through the copper member, and the bonding between the copper member and the graphene-containing carbonaceous member can be maintained.
Therefore, the ceramic/copper/graphene bonding structure having this configuration can maintain stable heat dissipation characteristics while suppressing the occurrence of peeling at the bonding interface due to thermal cycles, thereby achieving high reliability.

According to the present invention, a copper/graphene bonded body having excellent thermal cycle reliability and a manufacturing method thereof can be provided, in which a copper member made of copper or a copper alloy and a graphene-containing carbonaceous member containing graphene aggregates are firmly bonded, the current flowing through the bonded portion can be suppressed, and peeling does not occur even when subjected to thermal cycle loads.

FIG. 1 is a schematic explanatory diagram of a power module using a ceramic/copper/graphene bonded body (insulating substrate) according to an embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a ceramic/copper/graphene bonded body (insulating substrate) according to an embodiment of the present invention. FIG. 2 is an enlarged schematic view of a bonding interface between a copper member and a graphene-containing carbonaceous member and a bonding interface between a copper member and a ceramic member in a ceramic/copper/graphene bonded body (insulating substrate) according to an embodiment of the present invention. FIG. 1 is a flow diagram showing an example of a method for producing a ceramic/copper/graphene bonded body (insulating substrate) according to an embodiment of the present invention.

Embodiments of the present invention will be described below with reference to the attached drawings. Note that each embodiment shown below is specifically described to provide a better understanding of the gist of the invention, and does not limit the present invention unless otherwise specified. Also, the drawings used in the following description may show essential parts enlarged for the sake of convenience in order to make the features of the present invention easier to understand, and the dimensional ratios of each component may not necessarily be the same as the actual ones.

First, a ceramic/copper/graphene bonded body (ceramic/copper/graphene bonded structure) according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4. FIG.
The ceramic/copper/graphene bonded body in the present embodiment is an insulating substrate 20 having a structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded together.

First, a power module using a ceramic/copper/graphene bonded body (insulating substrate 20) according to this embodiment will be described.
A power module 1 shown in FIG. 1 includes an insulating circuit board 10, a semiconductor element 3 joined to one surface side (the upper side in FIG. 1) of the insulating circuit board 10 via a solder layer 2, and a heat sink 31 disposed on the other surface side (the lower side in FIG. 1) of the insulating circuit board 10.

Insulating circuit board 10 comprises an insulating layer (insulating substrate 20), a circuit layer 12 disposed on one surface (the upper surface in FIG. 1 ) of the insulating layer, and a metal layer 13 disposed on the other surface (the lower surface in FIG. 1 ) of the insulating layer.
The insulating layer prevents electrical connection between the circuit layer 12 and the metal layer 13, and is formed of an insulating substrate 20 in this embodiment.

The circuit layer 12 is formed by bonding a metal plate having excellent electrical conductivity to one surface of the insulating layer (insulating substrate 20). In this embodiment, a copper plate made of copper or a copper alloy, specifically a rolled plate of oxygen-free copper, is used as the metal plate constituting the circuit layer 12. A circuit pattern is formed on this circuit layer 12, and one surface thereof (the upper surface in FIG. 1 ) serves as a mounting surface on which the semiconductor element 3 is mounted.
The thickness of the metal plate (copper plate) that becomes the circuit layer 12 is set within a range of 0.1 mm to 1.0 mm, and in this embodiment, it is set to 0.6 mm.
There is no particular limitation on the method for joining the metal plate (copper plate) that will become the circuit layer 12 and the insulating substrate 20, and they can be joined using an active metal brazing material or the like.

The metal layer 13 is formed by joining a metal plate having excellent thermal conductivity to the other surface of the insulating layer (insulating substrate 20). In this embodiment, a copper plate made of copper or a copper alloy, specifically a rolled plate of oxygen-free copper, is used as the metal plate constituting the metal layer 13.
The thickness of the metal plate (copper plate) that becomes the metal layer 13 is set within a range of 0.1 mm to 1.0 mm, and in this embodiment, it is set to 0.6 mm.
There is no particular limitation on the method for joining the metal plate (copper plate) that will become the metal layer 13 to the insulating substrate 20, and they can be joined using an active metal brazing material or the like.

The heat sink 31 is for cooling the insulating circuit board 10 described above, and has a structure in which a plurality of flow paths 32 are provided for circulating a cooling medium (for example, cooling water).
The heat sink 31 is preferably made of a material having good thermal conductivity, such as aluminum or an aluminum alloy, copper or a copper alloy, and in this embodiment, is made of 2N aluminum having a purity of 99 mass % or more.
In this embodiment, the metal layer 13 of the insulating circuit board 10 and the heat sink 31 are bonded by solid-state diffusion bonding.

The semiconductor element 3 is made of a semiconductor material such as Si or SiC. The semiconductor element 3 is mounted on the circuit layer 12 via a solder layer 2 made of a solder material such as Sn-Ag, Sn-In, or Sn-Ag-Cu.

The insulating substrate 20 of this embodiment constituting the insulating layer has a structure in which a ceramic plate 26 made of a ceramic member, a copper plate 21 made of a copper member made of copper or a copper alloy, and a carbon plate 25 made of a graphene-containing carbonaceous member containing graphene aggregates are laminated together, as shown in Fig. 2. The copper plates 21 are bonded to both main surfaces of the carbon plate 25, respectively.
Here, an example of insulating substrate 20 is shown in which ceramic plate 26, copper plate 21, carbon plate 25, copper plate 21, and ceramic plate 26 are stacked in this order, but there is no limit to the number of layers as long as the outermost layer (end) in the stacking direction is ceramic plate 26 and the order of ceramic plate 26, copper plate 21, and carbon plate 25 is maintained.

The graphene-containing carbonaceous material constituting the carbon plate 25 preferably contains graphene aggregates formed by the deposition of single or multiple layers of graphene and flat graphite particles, and the flat graphite particles are preferably laminated with the graphene aggregates as a binder so that the basal surfaces of the flat graphite particles are folded over. The basal surfaces of the flat graphite particles are preferably oriented in one direction.

The flat graphite particles have a basal surface on which the hexagonal carbon mesh plane appears and an edge surface on which the end of the hexagonal carbon mesh plane appears. As the flat graphite particles, flake graphite, flaky graphite, earthy graphite, flaky graphite, kish graphite, pyrolytic graphite, highly oriented pyrolytic graphite, etc. can be used.
Here, the average particle size of the graphite particles as viewed from the basal plane is preferably in the range of 10 μm to 1000 μm, and more preferably in the range of 50 μm to 800 μm. By setting the average particle size of the graphite particles within the above range, the thermal conductivity is improved.
Furthermore, the thickness of the graphite particles is preferably in the range of 1 μm to 50 μm, and more preferably in the range of 1 μm to 20 μm. By setting the thickness of the graphite particles within the above range, the orientation of the graphite particles can be appropriately adjusted.
Furthermore, by adjusting the thickness of the graphite particles to within the range of 1/1000 to 1/2 of the particle diameter as viewed from the basal plane, excellent thermal conductivity and the orientation of the graphite particles can be appropriately adjusted.

The graphene aggregate is formed by depositing single-layer or multi-layer graphene, and the number of layers of the multi-layer graphene is, for example, not more than 100, and preferably not more than 50. This graphene aggregate can be produced, for example, by dropping a graphene dispersion in which single-layer or multi-layer graphene is dispersed in a solvent containing a lower alcohol or water onto a filter paper, and depositing the graphene aggregate while separating the solvent.
Here, the average particle size of the graphene aggregates is preferably within a range of 1 μm to 1000 μm. By setting the average particle size of the graphene aggregates within the above range, the thermal conductivity is improved.
Furthermore, the thickness of the graphene aggregate is preferably within a range of 0.05 μm or more and less than 50 μm. By setting the thickness of the graphene aggregate within the above range, the strength of the carbonaceous member is ensured.

3 shows an enlarged schematic diagram of a bonding interface between a copper plate 21 made of a copper member made of copper or a copper alloy and a carbon plate 25 made of a graphene-containing carbonaceous material, and a bonding interface between the copper plate 21 and a ceramic plate 26. As shown in FIG. 3, at the bonding interface 40 between the copper plate 21 made of a copper member and the carbon plate 25 made of the graphene-containing carbonaceous material, an active metal carbide layer 41 containing one or two types of active metal carbides is formed on the bonding surface of the carbon plate 25.
The copper plate 21 contains simple metals such as Mg and Cu, intermetallic compounds (IMCs) such as Cu-Mg and Cu-Ti, and the like, and in particular, at the joint interface 40, an Mg solid solution layer 42 in which Mg is dissolved in a Cu matrix is formed between the copper plate 21 and the active metal carbide layer 41. The Mg solid solution layer 42 may contain a Cu-Mg intermetallic compound phase made of an intermetallic compound containing Cu and Mg, or a second intermetallic compound phase made of an intermetallic compound containing Cu and an active metal.

The Cu-Mg intermetallic compound phase is composed of a Cu ₂ Mg phase and/or a CuMg ₂ phase.
In the Mg solid solution layer 42, in a cross section along the lamination direction of the copper member and the graphene-containing carbonaceous member, when the area of a region within a distance of 50 μm from the boundary surface 40 a with the active metal carbide layer 41 toward the copper member is defined as A (μm ² ) and the area of the Cu-Mg intermetallic compound phase is defined as B (μm ² ), the ratio B/A is preferably 0.3 or less, more preferably 0.25 or less, and most preferably 0.15 or less.
There are also cases where the Mg solid solution layer 42 does not contain a Cu--Mg intermetallic compound phase, that is, where the ratio B/A is zero.

The active metal carbide layer 41 is formed by a reaction between the active metal contained in the bonding material interposed between the copper plate 21 and the carbon plate 25 and the carbon contained in the carbon plate 25 during bonding.
For example, one or more selected from Ti, Zr, Hf, and Nb can be used as the active metal constituting the active metal carbide layer 41. In this embodiment, the active metal is Ti, and the active metal carbide layer 41 is made of titanium carbide (Ti-C).

Here, if the thickness _t1 of the active metal carbide layer 41 is less than 0.05 μm, the reaction between the active metal and carbon may be insufficient, and the bonding strength between the copper plate 21 and the carbon plate 25 via the active metal carbide layer 41 may be insufficient. On the other hand, if the thickness _t1 of the active metal carbide layer 41 exceeds 1.5 μm, cracks may occur in the active metal carbide layer 41 when subjected to a thermal cycle load.
Therefore, in this embodiment, it is preferable to set the thickness _t1 of the active metal carbide layer 41 within the range of 0.05 μm or more and 1.5 μm or less.
The lower limit of the thickness _t1 of the active metal carbide layer 41 is more preferably 0.1 μm or more, and even more preferably 0.25 μm or more. On the other hand, the upper limit of the thickness _t1 of the active metal carbide layer 41 is more preferably 1.2 μm or less, and even more preferably 1.0 μm or less.

The ceramic plate 26 is bonded to the copper plate 21 via a compound layer 43. The compound layer 43 is a layer formed by reacting one or more types of active metal selected from Ti, Zr, Nb, and Hf, or _Mg , as a bonding material, with the constituent elements of the ceramic plate 26. As the ceramic plate 26, for example, oxides such as _Al2O3 and Zr-added _Al2O3 , nitrides such as _AlN and _Si3N4 , and _SiAlON are used.

When the ceramic plate 26 is mainly composed of oxides, it is preferable to use Mg as the bonding material, in which case the main element constituting the compound layer 43 is MgO. When the ceramic plate 26 is mainly composed of nitrides, it is preferable to use Ti as the bonding material, in which case the main element constituting the compound layer 43 is TiN.

Next, the manufacturing method of the ceramic/copper/graphene bonded body (insulating substrate 20) according to this embodiment will be described with reference to the flow diagram shown in FIG. 4.

(Carbon plate forming step S01)
First, the above-mentioned flat graphite particles and graphene aggregates are weighed to have a predetermined blend ratio, and then mixed using an existing mixer such as a ball mill.
The mixture thus obtained is filled into a mold having a given shape and pressed to obtain a molded product. Heating may be performed during the pressing.
The resulting molded body is then cut to obtain the carbon plate 25 .

The pressure during molding is preferably in the range of 20 MPa to 1000 MPa, and more preferably in the range of 100 MPa to 300 MPa. The temperature during molding is preferably in the range of 50°C to 300°C. Furthermore, the pressurization time is preferably in the range of 0.5 minutes to 10 minutes.

(First active metal and Mg arrangement step S02)
Next, a copper plate 21 made of copper or a copper alloy is prepared, the joining surface of this copper plate 21 is placed opposite the joining surface of the carbon plate 25 obtained in the previous step, and one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg are placed between the two plates as joining materials. When the copper plate 21 is replaced with a plate of a different material, Cu is further placed as a joining material. The active metal and Mg can be placed by sputtering, (co)deposition, foil material, or paste application (hydrides of active metal and Mg can also be used).

As the bonding material, the amount of active metal to be placed between the copper plate 21 and the carbon plate 25 is 0.4 μmol/ ^cm2 or more, and the amount of Mg is 14 μmol/cm2 or ^more . Preferably, the amount of active metal is in the range of 0.4 μmol/ ^cm2 to 47.0 μmol/ ^cm2 , the amount of Cu is in the range of 4 μmol/ ^cm2 to 350 μmol/ ^cm2 , and the amount of Mg is in the range of 14 μmol/ ^cm2 to 180 μmol/ ^cm2 .

(First lamination step S03)
Next, the copper plates 21 are laminated (attached) to both main surfaces of the carbon plate 25 via a bonding material.

(First joining step S04)
Next, the carbon plate 25 and the copper plate 21 laminated with the bonding material therebetween are pressed in the lamination direction and heated, and then cooled, thereby bonding the carbon plate 25, the copper plate 21, and the ceramic plate 26 together.
Here, the heating temperature is preferably within a range of 700° C. to 950° C. The holding time at the heating temperature is preferably within a range of 10 minutes to 180 minutes. The applied pressure is preferably within a range of 0.049 MPa to 1.96 MPa. The atmosphere during bonding is preferably a non-oxidizing atmosphere.

In this first bonding process S04, the active metal (Ti in this embodiment) contained in the bonding material reacts with the carbon contained in the carbon plate 25 at the bonding interface between the carbon plate 25 and the copper plate 21, thereby forming an active metal carbide layer 41 on the bonding surface of the carbon plate 25.
Then, a part of the Cu, Mg, and active metal contained in the bonding material is absorbed into the copper plate 21, and further, the Cu and Mg contained in the bonding material react with each other, so that an Mg solid solution layer 42 in which Mg is dissolved in a Cu matrix is formed between the copper plate 21 and the active metal carbide layer 41. In the Mg solid solution layer 42, a Cu-Mg intermetallic compound phase made of an intermetallic compound containing Cu and Mg may be present, or a second intermetallic compound phase made of an intermetallic compound containing Cu and an active metal may be present.

(Second active metal and Mg arrangement step S05)
Next, a ceramic plate 26 is prepared, the bonding surface of this ceramic plate 26 is placed opposite the bonding surface of the copper plate 25, and at least one material consisting of one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg is placed between the two plates. The active metal and Mg can be placed by sputtering, (co)evaporation, foil material, or paste application (hydrides of the active metal and Mg can also be used).

When one or more types of active metals selected from Ti, Zr, Nb, and Hf are disposed between the copper plate 21 and the ceramic plate 25 as the bonding material, the amount of the active metal to be disposed is preferably within a range of 0.4 μmol/ ^cm2 to 47.0 μmol/ ^cm2 . When Mg is disposed between the copper plate 21 and the ceramic plate 25 as the bonding material, the amount of Mg to be disposed is preferably within a range of ¹⁴ μmol/ ^cm2 to 180 μmol/cm2.

(Second lamination step S06)
Next, a ceramic plate 26 is laminated via a bonding material onto each of the two copper plates 21 laminated onto the carbon plate 25. In this case, the bonding surface of the copper plate 21 becomes the main surface opposite to the carbon plate 25.

(Second bonding step S07)
Next, the copper plate 21 and the ceramic plate 26 laminated with the bonding material therebetween are pressed in the lamination direction and heated, and then cooled, thereby bonding the copper plate 21 and the ceramic plate 26 together.
Here, the heating temperature is preferably within a range of 700° C. to 950° C. The holding time at the heating temperature is preferably within a range of 10 minutes to 90 minutes. The applied pressure is preferably within a range of 0.049 MPa to 1.96 MPa. The atmosphere during bonding is preferably a non-oxidizing atmosphere.

By this second joining process S07, the oxygen or nitrogen that constitutes the ceramic plate 26 reacts with the elements of the joining material at the joining interface between the copper plate 21 and the ceramic plate 26, forming an oxide layer or nitride layer.

When the ceramic plate 26 contains oxides such as Al ₂ O ₃ and Zr-added Al ₂ O ₃ , and the bonding material between the copper plate 21 and the ceramic plate 26 is Mg, the bonding process S04 causes Mg to react with oxygen contained in the ceramic plate 26, and an MgO layer (compound layer 43) is formed at the bonding interface between the copper plate 21 and the ceramic plate 26.

When the ceramic plate 26 contains a nitride _such as AlN or _Si3N4 , and the bonding material between the copper plate 21 and the ceramic plate 26 is Ti, the bonding step S04 causes Ti to react with the nitrogen contained in the ceramic plate 26, and a TiN layer (compound layer 43) is formed at the bonding interface between the copper plate 21 and the ceramic plate 26.

When the ceramic plate 26 contains SiAlON and the bonding material between the copper plate 21 and the ceramic plate 26 is Ti, the bonding process S04 causes Ti to react with the nitrogen contained in the ceramic plate 26, forming a TiN layer (compound layer 43) at the bonding interface between the copper plate 21 and the ceramic plate 26.

The above steps produce the ceramic/copper/graphene bonded body (insulating substrate 20) of this embodiment.

In the above embodiment, the carbon plate 25 and the copper plate 21 are joined together, and then the copper plate 21 and the ceramic plate 26 are joined together. However, the carbon plate 25, the copper plate 21, and the ceramic plate 26 may be joined together at the same time.
Specifically, first, one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg are placed as bonding materials on one surface of the carbon plate 25, and the copper plate 21 is laminated on the placed active metals and Mg. Furthermore, one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg are placed as bonding materials on the copper plate 21, and the ceramic plate 26 is laminated on the placed active metals and Mg.
When the copper plate 21 and the ceramic plate 26 are laminated on the other surface of the carbon plate 25, the carbon plate 25, the copper plate 21 and the ceramic plate 26 are laminated in the same manner.
The active metal and Mg can be deposited by sputtering, (co)evaporation, application of a foil, or a paste (hydrides of the active metal and Mg can also be used).

Next, the carbon plate 25, the copper plate 21 and the ceramic plate 26 are pressed together in the stacking direction and heated, and then cooled, thereby bonding the carbon plate 25, the copper plate 21 and the ceramic plate 26 together.
Here, the heating temperature is preferably within a range of 700° C. to 950° C. The holding time at the heating temperature is preferably within a range of 10 minutes to 180 minutes. The applied pressure is preferably within a range of 0.049 MPa to 1.96 MPa. The atmosphere during bonding is preferably a non-oxidizing atmosphere.

As described above, according to the ceramic/copper/graphene bonded body (insulating substrate 20) of this embodiment, at the bonding interface between the copper member (copper plate 21) and the graphene-containing carbonaceous member (carbon plate 25), an active metal carbide layer 41 is formed on the bonding surface of the graphene-containing carbonaceous member, and an Mg solid solution layer 42 in which Mg is dissolved in the Cu matrix is formed on the bonding surface side of the copper member. As a result, Mg in the Mg solid solution layer 42 sufficiently reacts with the active metal in the active metal carbide layer 41, and the copper member is firmly bonded to the graphene-containing carbonaceous material via this active metal carbide layer 41, so that cracks and peeling can be suppressed from occurring at the bonding interface during thermal cycle loading. Furthermore, since the ceramic/copper/graphene bonded body of this embodiment contains copper as a constituent material, it has the function of efficiently dissipating heat as a heat spreader during the transition period.

Moreover, in the ceramic/copper/graphene bonded body of the present embodiment, the copper member having conductivity is covered with the ceramic member. Therefore, when the ceramic/copper/graphene bonded body is brought into contact with a predetermined device, a current is prevented from flowing into the bonded portion through the copper member, and the bond between the copper member and the graphene-containing carbonaceous member can be maintained.
Therefore, the ceramic/copper/graphene bonded body of the present embodiment can maintain stable heat dissipation characteristics while suppressing the occurrence of peeling at the bonded interface due to thermal cycles, and can achieve high reliability.

In addition, in the ceramic/copper/graphene bonded body of this embodiment, it is preferable that the Mg solid solution layer contains a Cu-Mg intermetallic compound phase consisting of an intermetallic compound containing Cu and Mg. In this case, the Cu-Mg intermetallic compound phase is distributed on the bonding surface side with the active metal carbide layer and is significantly involved in the bonding, thereby increasing the strength of the bond with the active metal carbide layer.

In addition, in the ceramic/copper/graphene bonded body of this embodiment, it is preferable that the Mg solid solution layer contains a second intermetallic compound phase consisting of an intermetallic compound containing Cu and an active metal. In this case, the second intermetallic compound phase is distributed on the bonding surface side with the active metal carbide layer and is significantly involved in the bonding, thereby increasing the strength of the bond with the active metal carbide layer.

In addition, in the ceramic/copper/graphene bonded body of this embodiment, the ceramic member is made of an oxygen-containing ceramic, and a magnesium oxide layer may be formed on the ceramic member side at the bonding interface between the ceramic member and the copper member. In this case, the magnesium oxide layer is formed, so that the bond between the oxygen-containing ceramic member and the copper member can be strengthened, and cracks and peeling can be suppressed at the bonding interface when subjected to a thermal cycle load.

In addition, in the ceramic/copper/graphene bonded body of this embodiment, the ceramic member is made of a nitrogen-containing ceramic, and an active metal nitride layer containing one or more nitrides of active metals selected from Ti, Zr, Nb, and Hf may be formed on the ceramic member side at the bonding interface between the ceramic member and the copper member. In this case, the active metal nitride layer containing one or more nitrides of active metals selected from Ti, Zr, Nb, and Hf is formed, thereby strengthening the bond between the nitrogen-containing ceramic member and the copper member, and suppressing the occurrence of cracks and peeling at the bonding interface during thermal cycle loading.

Furthermore, in the ceramic/copper/graphene bonded body of this embodiment, the graphene-containing carbonaceous member preferably includes graphene aggregates formed by the deposition of single or multiple layers of graphene and flat graphite particles, and the flat graphite particles are laminated with the graphene aggregates as a binder so that the basal surfaces of the flat graphite particles are folded over, and the basal surfaces of the flat graphite particles are preferably oriented in one direction. In this case, it is possible to further improve the thermal conductivity characteristics of the graphene-containing carbonaceous member.

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 concept of the invention.
For example, in the present embodiment, a power module is configured by mounting a semiconductor element (power semiconductor element) on the circuit layer of an insulating 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 an insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on the circuit layer of an insulating circuit board.

In addition, in this embodiment, as shown in FIG. 1, the insulating substrate 20 of this embodiment is described as being applied as the insulating layer of the insulating circuit board 10, but this is not limited thereto, and there is no particular restriction on the method of using the ceramic/copper/graphene bonded body of the present invention.

The following describes the confirmation experiments conducted to confirm the effectiveness of the present invention (Invention Examples 1-8, 11-19, and Comparative Examples 1-3).

As disclosed in this embodiment, flat graphite particles and graphene aggregates were mixed in a predetermined ratio and molded under pressure and heat to obtain a molded body in which flat graphite particles were laminated with the graphene aggregates as a binder so that their basal surfaces were folded over. The obtained molded body was cut out to obtain a carbon plate (40 mm x 40 mm x 1.0 mm thick).

Mg and active metal were placed on one side of this carbon plate in the amounts of Mg and active metal shown in Tables 1 and 2, a copper plate (37 mm x 37 mm x 0.3 mm thick) was laminated on the placed Mg and active metal, Mg and active metal were further placed on the copper plate in the amounts of Mg and active metal shown in Tables 1 and 2, and a ceramic plate (made of silicon nitride, 37 mm x 37 mm x 0.3 mm thick) was laminated on the placed Mg and active metal, and the carbon plate, copper plate, and ceramic plate were joined under the conditions shown in Tables 1 and 2.
The amount of Mg and the amount of active metal placed on one surface of the carbon plate were the same as the amount of Mg and the amount of active metal placed on the copper plate.
Note that Mg and the active metal were deposited by co-evaporation.
Here, the bonded interface between the carbon plate and the copper plate was observed to confirm the presence or absence of an active metal carbide layer, a Cu-Mg intermetallic compound phase, an active metal compound phase, and an Mg solid solution layer.

(Presence or absence of active metal carbide layer)
In the cross section along the lamination direction of the obtained bonded body, the bonding interface between the copper plate and the carbon plate was observed using a scanning transmission electron microscope (Titan ChemiSTEM (with EDS detector) manufactured by FEI) at a magnification of 20,000 to 120,000 times and an acceleration voltage of 200 kV. Mapping was performed using an energy dispersive X-ray analysis method (NSS7 manufactured by Thermo Scientific), and an electron diffraction pattern was obtained by irradiating an electron beam narrowed to about 1 nm in the area where the active metal and C overlap (NBD (nanobeam diffraction) method). If this electron diffraction pattern was an intermetallic compound of the active metal and C, the active metal carbide layer was determined to be "present".

(Presence or absence of Cu-Mg intermetallic compound phase)
In the cross section along the lamination direction of the obtained bonded body, the bonding interface between the copper plate and the carbon plate was observed using an electron beam microanalyzer (JXA-8539F manufactured by JEOL Ltd.) at a magnification of 2000 times and an acceleration voltage of 15 kV, and an elemental map of Mg was obtained in the region (400 μm × 600 μm) (hereinafter referred to as the observation region) including the bonding interface. The presence or absence of the Cu-Mg intermetallic compound phase was confirmed by determining the region where the Cu concentration was 5 atomic % or more and the Mg concentration was 30 atomic % or more and 70 atomic % or less in the average of five points of quantitative analysis in the region where the presence of Mg was confirmed. Note that the concentration here is the concentration when the total amount of Cu and Mg is 100 atomic %.
In addition, for the joints of Inventive Examples 11 to 19, the ratio B/A was measured, where A is the area of a region in the observation region within a distance of 50 μm from the boundary between the active metal carbide layer and the Mg solid solution layer toward the copper member side, and B is the area of the Cu-Mg intermetallic compound phase in a region in the observation region within a distance of 50 μm from the boundary between the active metal carbide layer and the Mg solid solution layer toward the copper member side.

(Presence or absence of active metal compound phase)
The bonding interface between the copper plate and the ceramic substrate was observed using an electron beam microanalyzer (JXA-8539F manufactured by JEOL Ltd.) at a magnification of 2000 times and an acceleration voltage of 15 kV, and an elemental map of the active metal in the region (400 μm × 600 μm) including the bonding interface was obtained. In the region where the presence of the active metal was confirmed, the region where the Cu concentration was 5 atomic % or more and the active metal concentration was 16 atomic % or more and 70 atomic % or less was regarded as a Cu-active intermetallic compound phase, and the presence or absence of the active metal compound phase was confirmed and indicated as the presence or absence of the second intermetallic compound phase. Note that the concentration here is the concentration when the total amount of Cu and the active metal is 100 atomic %.

(Presence or absence of Mg solid solution phase)
The region (400 μm×600 μm) including the bonding interface between the copper plate and the ceramic substrate was observed with an electron beam microanalyzer (JXA-8539F manufactured by JEOL Ltd.) at a magnification of 2000 times and an acceleration voltage of 15 kV. Quantitative analysis was performed at 10 μm intervals from the surface of the ceramic substrate toward the copper plate side, in a range of 10 to 20 points depending on the thickness of the copper plate, and the presence or absence of the Mg solid solution phase was confirmed by defining the region with a Mg concentration of 0.01 atomic % to 6.9 atomic % as the Mg solid solution phase.

The resulting joined bodies of Examples 1 to 8 of the present invention and Comparative Examples 1 to 3 were subjected to 2000 cycles of thermal cycling of -40°C for 5 minutes and 150°C for 5 minutes.
Further, a heating test was carried out on the obtained bonded bodies of Examples 11 to 19 of the present invention in a vacuum atmosphere, in which a cycle of heating at 400° C. for 30 minutes and cooling to room temperature (25° C.) was repeated 10 times.
Thereafter, the initial bonded area and non-bonded area between the carbon plate and the copper plate were measured for these bonded bodies using an ultrasonic flaw detector (FineSAT200 manufactured by Hitachi Power Solutions Co., Ltd.), and the bonding rate of the interface between the carbon plate and the copper plate was calculated using the following formula.
(Bonding rate) = [{(Initial bonding area) - (Non-bonding area)}/(Initial bonding area)] x 100
The initial bonded area here means the area of the parts that should be bonded. The non-bonded area means the part that should be bonded but is not actually bonded, that is, the area of the peeled part. In the image obtained by binarizing the ultrasonic inspection image, the peeling is shown as a white part in the bonded part, so the area of this white part was taken as the non-bonded area (peeled area).

In Comparative Example 1, the amount of Mg was small, so that the liquid phase generated at the interface was small, and the active metal carbide layer was not sufficiently generated. In Comparative Example 2, the amount of active metal was small, so that the active metal carbide layer was not sufficiently generated. In Comparative Example 3, the amount of Mg was small, so that the liquid phase generated at the interface was small, and further, the amount of active metal was small, so that the active metal carbide layer was not sufficiently generated.
Therefore, the bonding rate between the copper plate and the carbon plate shows a low value of less than 55% in the initial stage, and after the thermal cycle load, it becomes about 0 to 2%, and it is found that the bonding is almost completely eliminated.

In contrast, the ceramic/copper/graphene joints of Examples 1 to 8 and 11 to 19 of the present invention have an active metal carbide layer and an Mg solid solution layer at the joint, so the bonding rate between the copper plate and the carbon plate is high and exceeds 95%, and it is found that even when subjected to a thermal cycle load or heating test similar to those of Comparative Examples 1 to 3, the bonding rate does not fall below 90%. These results show that the ceramic/copper/graphene joints of Examples 1 to 8 and 11 to 19 of the present invention have sufficient strength to suppress peeling during a cooling cycle load, and achieve high reliability.

20 Insulating substrate (ceramics/copper/graphene composite)
21 Copper plate (copper material)
25 Carbon plate (graphene-containing carbonaceous material)
26 Ceramic plate (ceramic member)
40 Bonding interface 40a Boundary surface 41 Active metal carbide layer 42 Mg solid solution layer 43 Compound layer

Claims (12)

A ceramic/copper/graphene bonded body having a structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded to each other,
at a joining interface between the copper member and the graphene-containing carbonaceous member, an active metal carbide layer containing a carbide of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the graphene-containing carbonaceous member side,
A ceramic/copper/graphene joint, characterized in that an Mg solid solution layer, in which Mg is dissolved in a Cu matrix, is formed between the active metal carbide layer and the copper member. The ceramic/copper/graphene joint described in claim 1, characterized in that the Mg solid solution layer contains a Cu-Mg intermetallic compound phase consisting of an intermetallic compound containing Cu and Mg. 3. The ceramic/copper/graphene joint according to claim 2, wherein, when an area of a region in the Mg solid solution layer within a distance of 50 μm from a boundary between the active metal carbide layer and the Mg solid solution layer toward the copper member is defined as A and an area of the Cu-Mg intermetallic compound phase is defined as B, a ratio B/A is 0.3 or less. The ceramic/copper/graphene joint according to any one of claims 1 to 3, characterized in that the Mg solid solution layer contains a second intermetallic compound phase consisting of an intermetallic compound containing Cu and the active metal. The ceramic/copper/graphene bonded body according to any one of claims 1 to 4, characterized in that the ceramic member is made of an oxygen-containing ceramic, and a magnesium oxide layer is formed on the ceramic member side at the bonding interface between the ceramic member and the copper member. The ceramic/copper/graphene bonded body according to any one of claims 1 to 4, characterized in that the ceramic member is made of a nitrogen-containing ceramic, and an active metal nitride layer containing nitrides of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the ceramic member side at the bonding interface between the ceramic member and the copper member. The graphene-containing carbonaceous member according to any one of claims 1 to 6, characterized in that it includes graphene aggregates formed by the deposition of single or multiple layers of graphene and flat graphite particles, the flat graphite particles are stacked with the graphene aggregates as a binder so that the basal surfaces of the flat graphite particles are folded over, and the basal surfaces of the flat graphite particles are oriented in one direction. 8. A method for producing a ceramic/copper/graphene bonded body according to claim 1, comprising: a copper/graphene bonding step of bonding the copper member and the graphene-containing carbonaceous member; and a copper/ceramic bonding step of bonding the copper member and the ceramic member,
The copper/graphene bonding step includes an active metal and Mg arranging step of arranging one or more active metals selected from Ti, Zr, Nb, and Hf, and Mg, between the copper member and the graphene-containing carbonaceous member; a lamination step of laminating the copper member and the graphene-containing carbonaceous member with the active metal and Mg interposed therebetween; and a bonding step of bonding the copper member and the graphene-containing carbonaceous member laminated with the active metal and Mg interposed therebetween by heat treatment in a vacuum atmosphere while applying pressure in a lamination direction,
The method for producing a ceramic/copper/graphene bonded body, wherein in the active metal and Mg arranging step, the amount of active metal is 0.4 μmol/cm2 or ^more , and the amount of Mg is 14 μmol/cm2 or ^more . The pressure load in the joining step is in the range of 0.049 MPa or more and 1.96 MPa or less,
9. The method for producing a ceramic/copper/graphene bonded body according to claim 8, wherein a heating temperature in the bonding step is within a range of 700° C. or more and 950° C. or less. The method for producing a ceramic/copper/graphene bonded body according to claim 8 or 9, characterized in that in the copper/ceramic bonding process, one or more active metals selected from Ti, Zr, Nb, and Hf and Mg are placed between the copper member and the ceramic member, and the copper member and the graphene-containing carbonaceous member laminated via the active metal and Mg are bonded by heat treatment in a vacuum atmosphere while being pressurized in the lamination direction. The method for producing a ceramic/copper/graphene bonded body according to claim 8 or 9, characterized in that in the copper/ceramic bonding process, Mg is placed between the copper member and the ceramic member, and the copper member and the graphene-containing carbonaceous member laminated via the Mg are bonded by heat treatment in a vacuum atmosphere while being pressurized in the lamination direction. A ceramic/copper/graphene bonding structure in which a ceramic member, a copper member made of copper or a copper alloy, and a graphene-containing carbonaceous member containing graphene aggregates are bonded to each other,
at a joining interface between the copper member and the graphene-containing carbonaceous member, an active metal carbide layer containing a carbide of one or more active metals selected from Ti, Zr, Nb, and Hf is formed on the graphene-containing carbonaceous member side,
A ceramic/copper/graphene bonding structure, characterized in that an Mg solid solution layer, in which Mg is dissolved in a Cu matrix, is formed between the active metal carbide layer and the copper member.

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