JP2019033131A - Ceramic circuit board - Google Patents

Abstract

To provide a ceramic circuit board capable of suppressing warping of a base plate as well as maintaining high adhesiveness of a ceramic base material and a metal layer even by repeated heat generation and cooling.SOLUTION: A ceramic circuit board includes a ceramic base material 1 and at least one of metal layers 2a and 2b respective provided on the sides of the ceramic base material 1 and containing Al and/or Cu, and at least one of the metal layers 2a and 2b forms a metal circuit, and the ultra-fine load hardness of the outermost layer of the metal layers 2a and 2b is 70 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a ceramic circuit board, and more particularly to a ceramic circuit board suitable for mounting a high power electronic component such as a power module.

  In recent years, with higher performance of industrial equipment such as robots and motors, there is a demand for higher current and higher efficiency of inverters. Under such circumstances, in the power module used for the inverter, the heat generated from the semiconductor element is steadily increasing. In order to efficiently diffuse the heat generated from the semiconductor element, a ceramic circuit board having good thermal conductivity is used.

  The power module is generally a ceramic circuit board, a semiconductor element provided on one surface of the ceramic circuit board, and Cu provided on the other surface of the ceramic circuit board by soldering or the like, and having excellent thermal conductivity, A base plate made of Cu-Mo, Cu-C, Al, Al-SiC, Sl-C, and the like, and a heat dissipating fin provided by screwing or the like on the surface of the base plate opposite to the ceramic circuit board. Prepare.

  However, since the soldering of the base plate and the ceramic circuit board is performed by heating, there is a problem in that the base plate is likely to warp due to the difference in thermal expansion coefficient between the base plate and the ceramic circuit board.

  Heat generated from the semiconductor element or the like during operation of the power module is transmitted to the heat radiating fin through the ceramic circuit board, solder, and base plate. Therefore, if the base plate is warped, a gap (air gap) due to the warp is generated when the heat dissipating fins are attached to the base plate, and the heat dissipation performance is extremely lowered.

  In order to improve the problem of warping, for example, in a ceramic substrate having a metal layer bonded to both surfaces of a ceramic substrate, metal layers having different hardness, type, thickness, etc. are used as a metal circuit board and a heat sink, respectively. It has been proposed to join on one and other surfaces of a ceramic substrate (see, for example, Patent Document 1).

  Moreover, when manufacturing a power module, it is proposed to join a base plate and a ceramic circuit board by bringing the base plate in a molten state into contact with the ceramic circuit board (for example, Patent Document 2). reference).

JP 2004-207587 A JP 2002-76551 A

  From the viewpoint of reliability, the ceramic circuit board can not only suppress warpage of the base plate when it is joined to the base plate in the production of power modules, but also can generate the ceramic base material and metal layer by repeated heat generation and cooling in actual use. It is desirable that high adhesion can be maintained. However, the conventional ceramic circuit board and power module still have room for improvement from the viewpoint of reliability described above.

  The present invention has been made in view of such a situation, and not only can suppress warping of the base plate when joining to the base plate, but also can regenerate and cool the ceramic substrate and metal layer. An object of the present invention is to provide a ceramic circuit board capable of maintaining high adhesion.

  The present invention comprises a ceramic substrate and at least one metal layer containing Al and / or Cu provided on both surfaces of the ceramic substrate, and at least one of the metal layers forms a metal circuit. A ceramic circuit board is provided in which the outermost layer of the metal layer has an ultra-micro load hardness of 70 or more.

  In the outermost layer, a compressive stress or a tensile stress of 40 MPa or less may remain.

The ceramic substrate may be made of AlN, Si ₃ N ₄ or Al ₂ O ₃ and may have a thickness of 0.2 to 1.5 mm.

  The metal layer may be formed of at least one selected from the group consisting of an alloy containing Cu, Al, Cu and Mo, and an alloy containing Cu and W, and has a thickness of 0.1 to 2.0 mm. May be.

  A metal layer has a 1st metal layer and a 2nd metal layer, and the ceramic base material, the 1st metal layer, and the 2nd metal layer may be laminated | stacked in this order. In this case, the second metal layer may contain Cu. Further, the end surface of the first metal layer and the end surface of the second metal layer may be flush with each other, and the end surface of the first metal layer may protrude beyond the end surface of the second metal layer.

  According to the present invention, there is provided a ceramic circuit board that not only can suppress warping of the base plate when bonded to the base plate, but also can maintain high adhesion between the ceramic base material and the metal layer by repeated heat generation and cooling. It becomes possible to do.

It is sectional drawing which shows one Embodiment of a ceramic circuit board. It is sectional drawing which shows one Embodiment of a ceramic circuit board. It is sectional drawing which shows one Embodiment of a ceramic circuit board. It is sectional drawing which shows one Embodiment of a power module.

  Hereinafter, some embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

  FIG. 1 is a cross-sectional view showing an embodiment of a ceramic circuit board. As shown in FIG. 1, the ceramic circuit board 100 includes a ceramic substrate 1 and metal layers 2 a and 2 b provided on both surfaces of the ceramic substrate 1. At least one of the metal layers 2a and 2b forms an electric circuit (metal circuit). As shown in FIG. 1, the metal layers 2a and 2b may be composed of single metal layers 21a and 21b, respectively.

  The metal layers 2a and 2b contain Al and / or Cu, but preferably contain Al and / or Cu as a main component. Here, the “main component” means a component contained by 70% by mass or more based on the total mass of the metal layers 2a and 2b. When a metal layer contains both Al and Cu, those total amounts should just be 70 mass% or more. The proportion of the main component may be 90% by mass or more, or 95% by mass or more. The metal layer may contain a trace amount of inevitable impurities.

  In the ceramic circuit board 100 according to the present embodiment, the super micro load hardness of the outermost layer of the metal layers 2a and 2b is 70 or more. The outermost layers of the metal layers 2a and 2b refer to the single metal layers when the metal layers 2a and 2b are composed of single metal layers 21a and 21b, respectively. Are each composed of two or more layers, the outermost layer (the furthest from the ceramic substrate 1) of the two or more layers.

  The ceramic circuit board having such features not only can suppress warping of the base plate when bonded to the base plate, but also has high adhesion between the ceramic substrate and the metal layer due to repeated heat generation and cooling (heat cycle). The present inventors consider the reason why the property can be maintained as follows.

  First, according to the study by the present inventors, the occurrence of warpage of the base plate at the time of manufacturing the power module, the peeling of the ceramic base material and the metal layer by the heat cycle, and the occurrence of cracks in the ceramic base material It has been found that this is due to the difference in the coefficient of linear thermal expansion between the ceramic base material and the metal layer. In general, the linear thermal expansion coefficient of the metal layer is larger than the linear thermal expansion coefficient of the ceramic substrate. Therefore, tensile stress remains in the metal layer when the temperature is returned from the temperature at which the ceramic substrate and the metal layer are joined to room temperature or due to a heat cycle. It is considered that the above-described problems occur due to the residual tensile stress (residual stress).

  In order to reduce the residual stress, the present inventors paid attention to the ultra-small load hardness of the outermost layer of the metal layer of the ceramic circuit board. An indentation hardness test method is used as a method for measuring the hardness of the metal. This method is a method for evaluating the hardness from the area or depth of an indentation (indentation) formed by applying a constant load. In this evaluation method, when the tensile stress remains in the metal, the indentation is expanded by the tensile stress, and thus the measured value becomes small. On the other hand, when the compressive stress remains in the metal, the indentation is hindered by the compressive stress, and the measured value becomes large. The ceramic circuit board according to the present invention has been able to reduce the residual tensile stress (residual stress) in the ceramic circuit board by increasing the measured value of the hardness of the outermost layer of the metal layer in the obtained ceramic circuit board. The present inventors are thinking.

In the present specification, the ultra-small load hardness of the outermost layer of the metal layer of the ceramic circuit board is expressed by the following equation from the following formula by measurement with a micro-hardness meter using a triangular pyramid indenter with an edge-to-edge angle of 115 °. It means a value calculated as “HT115”.
HT115 = 160.07 · P / d ²
In the above formula, P represents the added maximum load (mN), and d represents the length (μm) of the perpendicular of the indentation by the triangular pyramid indenter.

  From the viewpoint as described above, it is preferable that the ultra-small load hardness of the outermost layer of the metal layers 2a and 2b is 80 or more. The upper limit value of the ultra micro load hardness is not particularly limited, but is, for example, 200 or less.

  For example, a thermal spraying method (cold spray method) is conceivable as a method of setting the ultra-micro load hardness of the outermost layer of the metal layers 2a and 2b within the above-described numerical range. The cold spray method is a technique in which metal particles in a solid state are jetted toward a substrate at supersonic speed to form a metal layer on the substrate. Since the metal particles are plastically deformed and accumulated at the time of collision, it is possible to increase the value of the ultra fine load hardness of the metal layer by work hardening due to the deformation.

  In the ceramic circuit board 100 according to the present embodiment, the residual stress of the outermost layer of the metal layers 2a and 2b is preferably 40 MPa or less, more preferably 30 MPa or less, still more preferably 20 MPa or less, and particularly preferably 10 MPa or less. The residual stress of the outermost layer of the metal layers 2a and 2b is evaluated by the measurement method by X-ray diffraction described in the examples.

  As a method for reducing the residual stress of the outermost layer of the metal layers 2a and 2b, for example, a method of reducing the residual stress of the metal layer by reducing the temperature at the time of joining the ceramic substrate and the metal layer is effective. Conceivable. The method for joining the ceramic substrate and the metal layer is not particularly limited. For example, an adhesive method in which both are bonded using an adhesive, an active metal method, a spraying method, etc., alone or in combination. The method to use is mentioned. From the viewpoint of reducing the temperature at the time of joining, it is preferable to use an adhesion method, a thermal spraying method, etc., and from the viewpoint of sufficiently ensuring heat dissipation as a power module without using an adhesive with low thermal conductivity, It is preferable to use an active metal method, a thermal spraying method or the like. From such a viewpoint, after forming a thin metal layer on the surface of the ceramic substrate by an active metal method or the like, a method of joining a metal of a predetermined thickness at a low temperature or a method of forming a metal layer by a thermal spraying method is effective. . Details of the method of joining the ceramic substrate and the metal layer will be described later.

In order to obtain such a ceramic circuit board 100, for example, the ceramic substrate 1 is preferably formed of AlN, Si ₃ N ₄ or Al ₂ O ₃ . The thickness of the ceramic substrate 1 is preferably 0.2 to 1.5 mm, and more preferably 0.25 to 1.0 mm. If the thickness of the ceramic substrate 1 is less than 0.2 mm, the thermal shock resistance is lowered, and if it exceeds 1.5 mm, the heat dissipation tends to be lowered.

  The metal layers 2a and 2b are preferably formed of at least one selected from the group consisting of alloys containing Cu, Al, Cu and Mo, and alloys containing Cu and W. The metal layers 2a and 2b may be formed of the same kind of material or different kinds of materials, but are formed of the same kind of material from the viewpoint of facilitating the manufacture of the ceramic circuit board. It is preferable.

  The thickness of the metal layers 2a and 2b is preferably 0.1 to 2.0 mm, and more preferably 0.2 to 1.0 mm. If the thickness of the metal layers 2a and 2b is less than 0.1 mm, the current that can be passed is limited, and if it exceeds 2.0 mm, the thermal shock resistance tends to be reduced. The thicknesses of the metal layers 2a and 2b may be substantially the same or different, but are preferably substantially the same from the viewpoint of facilitating the production of the ceramic circuit board.

  As described above, the ceramic circuit board 100 can be obtained by bonding the ceramic base 1 and the metal layers 2a and 2b. Examples of the method for bonding the ceramic substrate and the metal layer include a method using an adhesive, an active metal method, a thermal spraying method, or the like alone or in combination.

  The bonding method is a method in which both are bonded using an adhesive, and a circuit is formed by an etching method if desired after a metal plate is bonded to both surfaces of a ceramic substrate with, for example, an acrylic adhesive.

In the active metal method, for example, when joining a metal layer containing Cu, a brazing material of Ag (90%)-Cu (10%)-TiH ₂ (3.2%) is used at a temperature of 800 ° C. A method of forming a circuit by an etching method if desired after bonding Cu plates to both sides of the substrate. When joining Al-containing metal layers, use Al-Cu-Mg clad foil as a brazing material, join Al plates on both sides of the ceramic substrate at a temperature of 630 ° C, and then form a circuit by etching if desired. The method of doing is mentioned.

  The thermal spraying method (cold spray method) is, for example, heating a metal powder composed of a plurality of metal particles to 10 to 270 ° C. and accelerating to a speed of 250 to 1050 m / s and then spraying the ceramic base material. A step of forming a metal layer thereon, and a step of heat-treating the ceramic substrate and the metal layer formed on the ceramic substrate in an inert gas atmosphere. By using Al and / or Cu particles as the metal particles constituting the metal powder, a metal layer containing these is formed.

  In the above-described embodiment, the case where the metal layers 2a and 2b are each composed of a single metal layer 21a and 21b has been described. However, the present invention is not limited to the above-described embodiment, and the metal layers 2a and 2b each include two metal layers 2a and 2b. You may have a metal layer more than a layer.

  2 and 3 are cross-sectional views showing another embodiment of the ceramic circuit board. In the ceramic circuit board 101 of FIG. 2 and the ceramic circuit board 102 of FIG. 3, the metal layers 2a and 2b are respectively on the first metal layers 22a and 22b and the first metal layers 22a and 22b in contact with the ceramic substrate 1. The second metal layers 23a and 23b are formed. In the ceramic circuit board 101 shown in FIG. 2, the end face 22E of the first metal layers 22a and 22b and the end face 23E of the second metal layers 23a and 23b are flush, but the ceramic circuit board is more excellent. From the viewpoint of having thermal shock resistance, the end surfaces 22E of the first metal layers 22a and 22b are outside the end surfaces 23E of the second metal layers 23a and 23b, that is, the ceramic substrate, like the ceramic circuit board 102 shown in FIG. You may protrude to the edge part side of the material 1. FIG. The width of the portion where the end surface 22E protrudes beyond the end surface 23E may be, for example, 1 to 1000 μm.

  The ceramic circuit board described above is suitably used in a power module, and not only can suppress warpage of the base plate that occurs when it is joined to the base plate, but also can be applied to the ceramic base material and the metal layer by repeated heat generation and cooling. High adhesion can be maintained.

  The warpage of the base plate that occurs when joining the base plate is measured as the amount of deformation (warp change) from the initial shape (initial warpage amount) of the base plate itself when the ceramic circuit board is joined to the base plate. The Further, the amount of warpage of the base plate means the amount of warpage per 10 cm length in the heat radiation surface direction at an arbitrary position of the base plate. The amount of warpage change of the base plate is preferably 20 μm or less, more preferably 15 μm or less, and still more preferably 10 μm or less for bonding to the ceramic circuit board. The warpage change amount is defined as an absolute value of a difference between the warpage amount of the base plate before bonding to the ceramic circuit board and the warpage amount of the base plate after bonding to the ceramic circuit board.

  FIG. 4 is a cross-sectional view showing an embodiment of the power module. As shown in FIG. 4, the power module 200 includes a base plate 3, a ceramic circuit substrate 103 bonded to the base plate 3 via a first solder 4, and a second solder 5 on the ceramic circuit substrate 103. And a semiconductor element 6 joined via the.

  The ceramic circuit board 103 includes a ceramic substrate 1 and metal layers 2 a and 2 b provided on both surfaces of the ceramic substrate 1. The base plate 3 is bonded to the metal layer 2b through the first solder 4. The semiconductor element 6 is bonded to a predetermined portion of the metal layer 2a via the second solder 5, and is bonded to a predetermined portion of the metal layer 2a with a metal wire 7 such as an aluminum wire (aluminum wire). Yes. In the power module shown in FIG. 4, the metal layer 2a forms an electric circuit (metal circuit). The metal layer 2b may or may not form a metal circuit.

  Each of the above-described components provided on the base plate 3 is covered with, for example, a hollow box-shaped resin casing 8 opened on one side, and is accommodated in the casing 8. A hollow portion between the base plate 3 and the housing 8 is filled with a filler 9 such as silicone gel. An electrode 10 penetrating through the housing 8 is joined to a predetermined portion of the metal layer 2a via a third solder 11 so that electrical connection with the outside of the housing 8 is possible.

  At the edge of the base plate 2, a mounting hole 3 a for screwing when a heat radiating component is attached to the power module 200 is formed. The number of mounting holes 3a is, for example, four or more. Instead of the attachment hole 3a, an attachment groove in which the side wall of the base plate 3 has a U-shaped cross section may be formed at the edge of the base plate 3.

  Since the power module 200 includes the above-described ceramic circuit board according to the present embodiment, the power module 200 is suitably used as a drive inverter for a train or automobile that requires high breakdown voltage, high output, and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Example 1]
As the ceramic substrate, an aluminum nitride (AlN) substrate (size: 50 mm × 60 mm × 0.635 mmt) was used. An Al-Cu-Mg clad foil was used as a brazing material, Al plates (thickness 0.2 mm) were bonded to both surfaces of the ceramic substrate at a temperature of 630 ° C., and an Al circuit was formed by etching. Subsequently, a Cu circuit having a thickness of 0.4 mm was laminated by a thermal spraying method (cold spray method), annealed at a temperature of 300 ° C., and then subjected to electroless Ni plating to produce a ceramic circuit board.

[Example 2]
An Al circuit having a thickness of 0.2 mm was laminated on both surfaces of the same ceramic substrate as in Example 1 by a thermal spraying method (cold spray method), and annealed at a temperature of 500 ° C. Subsequently, a Cu circuit having a thickness of 0.4 mm was laminated by a thermal spraying method (cold spray method), annealed at a temperature of 300 ° C., and then subjected to electroless Ni plating to produce a ceramic circuit board.

[Example 3]
A silicon nitride (Si ₃ N ₄ ) base material (size: 50 mm × 60 mm × 0.32 mmt) was used as the ceramic base material. An Ag—Cu—TiH ₂ brazing material was used, Cu plates (thickness 0.1 mm) were bonded to both surfaces of the ceramic substrate at a temperature of 800 ° C., and a Cu circuit was formed by etching. Subsequently, a Cu circuit having a thickness of 0.9 mm was laminated by a thermal spraying method (cold spray method), annealed at a temperature of 300 ° C., and then subjected to electroless Ni plating to produce a ceramic circuit board.

[Comparative Example 1]
After using a Ag—Cu—TiH ₂ brazing filler metal to bond a Cu plate (thickness 0.3 mm) at a temperature of 800 ° C. to both surfaces of a ceramic substrate similar to that in Example 1, and forming a Cu circuit by etching, Electrolytic Ni plating was applied to produce a ceramic circuit board.

[Comparative Example 2]
A ceramic circuit board was produced in the same manner as in Comparative Example 1 except that an aluminum nitride (AlN) base material (size: 50 mm × 60 mm × 1.0 mmt) was used as the ceramic base material.

[Comparative Example 3]
A ceramic circuit board was produced in the same manner as in Comparative Example 1 except that a silicon nitride (Si ₃ N ₄ ) base material (size: 50 mm × 60 mm × 0.635 mmt) was used as the ceramic base material.

[Comparative Example 4]
A ceramic circuit board was produced in the same manner as in Comparative Example 1 except that a silicon nitride (Si ₃ N ₄ ) base material (size: 50 mm × 60 mm × 0.32 mmt) was used as the ceramic base material.

[Comparative Example 5]
A ceramic circuit board was produced by performing the same operation as in Comparative Example 4 except that a Cu plate (thickness: 1.0 mm) was used.

[Comparative Example 6]
After using an Al—Cu—Mg clad foil as a brazing material, joining Al plates (thickness 0.4 mm) at both temperatures of 630 ° C. on both surfaces of a ceramic substrate similar to Example 1, and forming an Al circuit by etching Then, electroless Ni plating was performed to produce a ceramic circuit board.

  Table 1 shows details of the ceramic circuit boards of the examples and comparative examples.

<Measurement of ultra-micro load hardness (HT115) of outermost layer of metal layer>
The obtained ceramic circuit board was cut into a size of 4 × 20 mm, embedded in an epoxy resin, and then the cut surface of the sample was polished by an automatic polishing apparatus was used as a measurement sample.
Using a micro hardness tester (manufactured by Shimadzu Corporation, trade name “DUH-211”), the load speed is 70.67 mN / sec, the test force is 500 mN, and the load holding time is 10 seconds. A test was conducted to measure the micro load hardness. The results are shown in Table 2.

<Measurement of residual stress>
The residual stress in the outermost layer of the metal layer of each ceramic circuit board was evaluated based on the result of measuring the X-ray diffraction pattern at the center of the metal layer using the X-ray diffraction method. The sin ² ψ method (parallel tilt method, ψ constant method) was used for stress evaluation, and the copper 331 diffraction line was analyzed. Specifically, a ceramic insulating substrate was attached to a sample plate of an X-ray diffraction apparatus (manufactured by Rigaku Corporation; Ultimate IV type) to which a multipurpose sample attachment was attached, and measurement was performed under the following measurement conditions.
X-ray source: CuKα ray (parallel beam optical system using multilayer mirror)
X-ray tube voltage and current: 40 kV and 40 mA
-X-ray incident side slit: 1 mm for the divergent slit, 10 mm for the vertical limiting slit
-X-ray receiving slit: Scattering slit and receiving slit are open. Parallel slit analyzer has an opening angle of 0.5 °
・ Vertical divergence-limited solar slit: X-ray incident side and light-receiving side have an opening angle of 5 °
Detector: Scintillation counter Measurement range (2θ): 134 ° to 139.5 °
・ Measurement step width: 0.02 °
-Counting time: 5 seconds per measurement step-Angle ψ between sample surface normal and diffraction surface normal: sin ² ψ is 0, 0.1, 0.2, 0.3, 0.4, 0.5 Set to be. In order to improve the measurement accuracy, the vibration may be applied within ± 5 °.

The following equation was used to calculate the residual stress σ. In the following equation, E is Young's modulus, ν is Poisson's ratio, and θ ₀ is the diffraction line angle when the sample is in an unstrained state. When the outermost layer of the metal layer is copper, E = 127200 MPa, ν = 0.364, 2θ ₀ = 136.882 ° in calculating the residual stress σ. When the outermost layer of the metal layer was aluminum, E = 68900 MPa, ν = 0.345, 2θ ₀ = 137.451 ° was calculated in calculating the residual stress σ. Δ (2θ) / Δ (sin ² ψ) was calculated by linearly approximating the 2θ-sin ² ψ plot. The results are shown in Table 2. In addition, when the sign of the residual stress is minus, it means compressive stress, and when it is plus, it means tensile stress.

<Measurement of warpage change of base plate after soldering>
After processing the Al—SiC (65%) material to a size of 140 × 190 × 5 mm, using the base plate plated with electroless Ni, the ceramic circuit boards obtained in the above examples and comparative examples The base plate was joined with eutectic solder to obtain a measurement sample.
By measuring the shape of the heat radiating surface of the base plate in the measurement sample using a three-dimensional contour measuring device (trade name “Contour Record 1600D-22”, manufactured by Tokyo Seimitsu Co., Ltd.), the warp of the base plate to a length of 10 cm The amount of change was measured. The results are shown in Table 2.

  Table 2 summarizes the evaluation results of each ceramic circuit board.

  With respect to the samples of Examples 1 to 3, a heat cycle test of 1000 cycles was performed by setting one cycle as an operation of leaving the sample in a 125 ° C. environment for 30 minutes and then leaving it in a −40 ° C. environment for 30 minutes. Even after the heat cycle test, abnormalities such as peeling of the metal circuit were not confirmed on the ceramic circuit boards of Examples 1 to 3, indicating that high adhesion was maintained.

  DESCRIPTION OF SYMBOLS 1 ... Ceramic base material, 2a, 2b ... Metal layer, 21a, 21b ... Single metal layer, 22a, 22b ... First metal layer, 22E ... End surface of the first metal layer, 23a, 23b ... Second metal layer, 23E: End face of second metal layer, 100, 101, 102, 103: Ceramic circuit board.

Claims (9)

A ceramic base material, and provided on each of both surfaces of the ceramic base material, and comprising at least one metal layer containing Al and / or Cu,
At least one of the metal layers forms a metal circuit;
A ceramic circuit board, wherein the outermost layer of the metal layer has an ultra-micro load hardness of 70 or more.   The ceramic circuit board according to claim 1, wherein a compressive stress or a tensile stress of 40 MPa or less remains in the outermost layer. The ceramic circuit board according to claim 1 or 2, wherein the ceramic base is formed of AlN, Si ₃ N ₄ or Al ₂ O ₃ .   The ceramic circuit board according to any one of claims 1 to 3, wherein the ceramic substrate has a thickness of 0.2 to 1.5 mm.   The metal layer is formed of at least one selected from the group consisting of an alloy containing Cu, Al, Cu and Mo, and an alloy containing Cu and W. Ceramic circuit board.   The ceramic circuit board according to claim 1, wherein the metal layer has a thickness of 0.1 to 2.0 mm.   The said metal layer has a 1st metal layer and a 2nd metal layer, The said ceramic base material, a said 1st metal layer, and a said 2nd metal layer are laminated | stacked in this order. The ceramic circuit board according to one item.   The ceramic circuit board according to claim 7, wherein the second metal layer contains Cu.   The end surface of the first metal layer and the end surface of the second metal layer are flush with each other, or the end surface of the first metal layer protrudes outside the end surface of the second metal layer. Or the ceramic circuit board of 8.

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