JP7299672B2 - Ceramic circuit board and its manufacturing method - Google Patents

Description

The present invention relates to a ceramic circuit board and its manufacturing method, and more particularly to a ceramic circuit board suitable for mounting high-power electronic components such as power modules and its manufacturing method.

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

A power module generally includes a ceramic circuit board, a semiconductor element provided on one side of the ceramic circuit board, and a semiconductor element provided on the other side of the ceramic circuit board by soldering or the like. A base plate made of Cu--Mo, Cu--C, Al, Al--SiC, Al--C, or the like, and radiation fins provided by screwing or the like on the surface of the base plate opposite to the ceramic circuit board. Prepare.

Heat generated from a semiconductor element or the like during operation of the power module is transferred to the heat dissipation fins through the ceramic circuit board, solder, and base plate. During actual use, the power module is placed in an environment where heat generation and cooling are repeated. There is a problem that cracks occur in the ceramic substrate due to thermal stress that repeatedly occurs between the ceramic substrate and the metal circuit, resulting in a decrease in reliability.

To address such reliability issues, for example, in a ceramic circuit board having metal layers bonded to both sides of a ceramic substrate, metal layers with different hardness, types, thickness, etc. are used as a metal circuit board and a heat sink, respectively. It has been proposed to join on one side and the other side of a ceramic substrate by using a ceramic substrate (see, for example, Patent Document 1). In addition, when manufacturing a power module, it has been proposed to join the base plate and the ceramic circuit board by bringing the molten base plate and the ceramic circuit board into contact (for example, Patent Document 2). reference).

JP 2004-207587 A JP-A-2002-76551

From the viewpoint of reliability, the ceramic circuit board does not peel off the metal layer from the ceramic base material or cause cracks in the ceramic base material even when repeatedly heated and cooled in actual use. It is desirable to be able to maintain high adhesion of the layers. However, conventional ceramic circuit boards and power modules using the same still have room for improvement during high-temperature operation, and there is also a demand for improved heat dissipation.

The present invention has been made in view of such circumstances, and has excellent reliability that can sufficiently demonstrate performance even when used in an environment where heat generation and cooling are repeated, and An object of the present invention is to provide a ceramic circuit board with excellent heat dissipation and a method for manufacturing the same.

The present invention provides a ceramic circuit board comprising a ceramic substrate and metal layers provided on both sides of the ceramic substrate, wherein the metal layer provided on at least one surface of the ceramic substrate forms a metal circuit. A manufacturing method is provided. This manufacturing method includes (A) the step of forming a first metal layer containing copper as a main component on both sides of a ceramic substrate; In the step (B), a layer containing copper as a main component is formed as a second metal layer located on one side of the ceramic base, and the other side of the ceramic base is formed. A layer containing aluminum as a main component is formed as the second metal layer located on the side of the ceramic substrate, and the metal layer has a multilayer structure including a first metal layer and a second metal layer in this order from the ceramic substrate side. It has a thickness of 0.5 to 2.0 mm.

According to the above manufacturing method, the second metal layer, which constitutes a part of one of the metal layers formed on both surfaces of the ceramic substrate, is a layer containing copper as the main component of the first metal layer. By forming the metal layer on the surface by thermal spraying, it is possible to form a sufficiently thick metal layer that is superior in thermal conductivity compared to the ceramic base material, and to obtain a ceramic circuit board that is excellent in heat dissipation. Further, a layer containing aluminum as a main component is thermally sprayed onto the surface of the first metal layer as a second metal layer constituting a part of the other metal layer of the metal layers formed on both surfaces of the ceramic substrate. This second metal layer functions as a buffer layer between the base plate and contributes to improving the reliability of the ceramic circuit board. The term "main component" as used herein means a component contained in an amount of 70% by mass or more based on the total mass of the target metal layer (first metal layer or second metal layer).

The above manufacturing method is for manufacturing a ceramic circuit board having a first metal layer containing copper as a main component. Instead of forming the first metal layer, a first metal layer containing aluminum as a main component may be formed.

The present invention provides a ceramic circuit board. A ceramic circuit board according to a first aspect comprises a ceramic substrate and metal layers provided on both sides of the ceramic substrate, wherein the metal layer provided on at least one surface of the ceramic substrate serves as a metal circuit. to form The metal layer has a multilayer structure including a first metal layer and a second metal layer in this order from the ceramic substrate side, and has a thickness of 0.2 to 1.5 mm. The first metal layer contains copper as a main component, and the second metal layer located on one side of the ceramic substrate contains copper as a main component and is formed by thermal spraying. The second metal layer located on the other side of the base material is mainly composed of aluminum and is formed by thermal spraying.

In the ceramic circuit board, one of the metal layers located on both surfaces of the ceramic substrate has the second metal layer containing copper as a main component, so that the ceramic circuit board has excellent heat dissipation properties. In addition, the other metal layer of the metal layers positioned on both sides of the ceramic substrate has a second metal layer containing aluminum as a main component, and this second metal layer buffers between the base plate and the base plate. It functions as a layer and contributes to improving the reliability of ceramic circuit boards.

The ceramic circuit board according to the second aspect is the same as the first aspect except that it has a metal layer having the following structure. That is, the metal layer of the ceramic circuit board according to the second aspect has a multilayer structure including a first metal layer and a second metal layer in this order from the ceramic substrate side, and has a thickness of 0.2 to 1.5 mm. and satisfies the following conditions.
- The first metal layer is mainly composed of copper and has a thickness in the range of 0.1 to 0.3 mm.
- The second metal layer located on one side of the ceramic substrate is mainly composed of copper and has a thickness in the range of 0.4 to 1.9 mm.
- The second metal layer located on the other side of the ceramic substrate is mainly composed of aluminum and has a thickness in the range of 0.4 to 1.9 mm.

In the ceramic circuit board provided with the metal layers having the above configuration, one of the metal layers located on both sides of the ceramic substrate is mainly composed of copper and has a thickness in the range of 0.4 to 1.9 mm. Since it has the second metal layer, it has excellent heat dissipation. In addition, the other metal layer of the metal layers located on both sides of the ceramic substrate has a second metal layer containing aluminum as a main component and having a thickness in the range of 0.4 to 1.9 mm, This second metal layer functions as a buffer layer between the base plate and contributes to improving the reliability of the ceramic circuit board.

The ceramic circuit board according to the first and second aspects has a first metal layer containing copper as a main component. The ceramic circuit board according to the present invention has a first metal layer containing copper as a main component Instead of the layer, it may have a first metal layer whose main component is aluminum.

Adhesion between the ceramic substrate and the metal layer can be evaluated by a heat cycle test. In the ceramic circuit board according to the present invention, the operation of leaving the ceramic circuit board in an environment of 180° C. for 30 minutes and then leaving the ceramic circuit board in an environment of -45° C. for 30 minutes is regarded as one cycle, and this cycle is repeated 500 times. It is preferable that the metal circuit does not peel off from the ceramic substrate after repeated heat cycle tests.

Preferably, the second metal layer is thicker than the first metal layer. By forming the second metal layer thicker than the first metal layer by thermal spraying, a metal layer having a sufficient thickness and less residual stress can be formed on the surface of the ceramic substrate. The end face of the first metal layer and the end face of the second metal layer may be flush with each other, or the end face of the first metal layer may protrude outside the end face of the second metal layer.

From the viewpoint of mechanical strength, heat resistance, etc., the material of the ceramic substrate is preferably Si ₃ N ₄ . From the viewpoint of heat dissipation of the ceramic circuit board, it is preferable that the ceramic substrate is sufficiently thin, and the thickness thereof is preferably in the range of 0.2 to 1.5 mm.

INDUSTRIAL APPLICABILITY According to the present invention, there is provided a ceramic circuit board which has excellent reliability and excellent heat dissipation properties so that performance can be sufficiently exhibited even when used in an environment where heat generation and cooling are repeated, and a method for manufacturing the same. provided.

1 is a cross-sectional view showing an embodiment of a ceramic circuit board; FIG. FIG. 4 is a cross-sectional view showing another embodiment of a ceramic circuit board; It is a sectional view showing one mode of a power module.

Several embodiments of the invention are described in detail below. However, the present invention is not limited to the following embodiments.

<Ceramic circuit board>
FIG. 1 is a cross-sectional view showing one embodiment of a ceramic circuit board. As shown in FIG. 1, a ceramic circuit board 10A includes a ceramic base 1 and metal layers 2 and 3 provided on both sides of the ceramic base 1. As shown in FIG. In this embodiment, the metal layer 2 forms an electrical circuit (see FIG. 3). The metal layer 2 has a multilayer structure including a first metal layer 2a and a second metal layer 2b in this order from the ceramic substrate 1 side. The metal layer 3 has a multilayer structure including a first metal layer 3a and a second metal layer 3b in this order from the ceramic substrate 1 side.

When the ceramic circuit board 10A having the above configuration is joined to the base plate (see the base plate 20 in FIG. 3) in the power module manufacturing process, not only can the warp of the base plate be suppressed, but heat generation and cooling are repeated. High adhesion between the ceramic substrate 1 and the metal layers 2 and 3 can be maintained even when used in a harsh environment. The inventors of the present invention consider the reason for this as follows.

First, according to the study of the present inventors, the occurrence of warping of the base plate during the production of the power module, the separation of the ceramic substrate and the metal layer due to the heat cycle, and the occurrence of cracks in the ceramic substrate are caused by the ceramic circuit substrate. It has been found that the reason for this is the difference in coefficient of linear thermal expansion between the ceramic base material and the metal layer. In general, the coefficient of linear thermal expansion of the metal layer is larger than the coefficient of linear thermal expansion of the ceramic substrate. Therefore, tensile stress remains in the metal layer when the temperature at which the ceramic substrate and the metal layer are bonded is returned to room temperature or due to heat cycles. It is considered that the residual tensile stress (residual stress) causes the problems described above.

The present inventors focused on the linear thermal expansion coefficient of the ceramic circuit board in order to reduce the residual stress. According to further studies by the inventors of the present invention, the coefficient of linear thermal expansion of the ceramic circuit board depends on the structure (thickness, etc.) and composition of the ceramic base and metal layer, It has been found that the residual stress generated by the difference in thermal expansion between the two materials when returning from the temperature at which the two are joined to room temperature. For this reason, for example, ceramic circuit boards having the same structure may have different coefficients of linear thermal expansion depending on the joining method. In general, the ceramic base material and the metal layer are often joined by brazing by the active metal method at a temperature of about 800 ° C. When joining under such conditions, the process of cooling to room temperature after joining Tensile stress remains in the metal layer with a large coefficient of linear thermal expansion. When tensile stress remains, the measured value of the coefficient of linear thermal expansion of the obtained ceramic circuit board is the theory of the coefficient of linear thermal expansion calculated from the structure (thickness, etc.) and composition of the ceramic base material and metal layer that constitute it. It is considered that the value will be smaller than the value. In the ceramic circuit board according to the present embodiment, the measured value of the coefficient of linear thermal expansion of the obtained ceramic circuit board is increased and the measured value is brought closer to the theoretical value, thereby reducing the residual stress in the ceramic circuit board. The present inventors believe that

Furthermore, since the ceramic circuit board according to the present embodiment can reduce its own residual stress, it suppresses the warpage of the base plate when it is joined to the base plate regardless of the type of base plate or the value of the linear thermal expansion coefficient. I think it is possible.

As a method for increasing the measured value of the linear thermal expansion coefficient of the ceramic circuit board, for example, it is considered effective to increase the thickness of the metal layer having a large linear thermal expansion coefficient. However, if the coefficient of linear thermal expansion of the ceramic circuit board is too large, the tensile stress of the metal layer against the ceramic base material will increase, and in a heat cycle test assuming actual use, cracks will occur in the ceramic base material. Problems can occur.

On the other hand, as a method of bringing the measured value of the linear thermal expansion coefficient of the ceramic circuit board closer to the theoretical value, for example, a method of lowering the temperature when joining the ceramic substrate and the metal layer to reduce the residual stress of the metal layer. etc. are considered to be effective. The method for joining the ceramic base material and the metal layer is not particularly limited, but for example, a bonding method in which the two are bonded using an adhesive, an active metal method, a thermal spraying method, etc. alone or in combination. A method of using them in combination is mentioned. From the viewpoint of reducing the temperature at the time of joining, it is preferable to use an adhesive method, a thermal spraying method, or the like. It is preferable to use an active metal method, a thermal spraying method, or the like. From this point of view, it is effective to form a thin metal layer on the surface of the ceramic base material by the active metal method or the like, and then join the metal plates with a predetermined thickness at a low temperature or to form the metal layer by thermal spraying. is. The details of the method for joining the ceramic base material and the metal layer will be described later.

In order to obtain such a ceramic circuit board 10A, _the ceramic base 1 is preferably made of _Si3N4 , for example.

The thickness of the ceramic substrate 1 is preferably 0.2-1.5 mm, more preferably 0.25-1.0 mm. If the thickness of the ceramic substrate 1 is less than 0.2 mm, the thermal shock resistance tends to be lowered, and if it exceeds 1.5 mm, the heat dissipation tends to be lowered.

The metal layer 2 has a multilayer structure including a first metal layer 2a and a second metal layer 2b in this order from the ceramic substrate 1 side. The metal layer 3 has a multilayer structure including a first metal layer 3a and a second metal layer 3b in this order from the ceramic substrate 1 side.

The first metal layers 2a and 3a contain Cu (copper) as a main component. The term "main component" as used herein means a component contained in an amount of 70% by mass or more based on the total mass of the first metal layers 2a and 3a. The content of Cu in the first metal layers 2a and 3a may be 90% by mass or more, or may be 95% by mass or more. Elements other than Cu that can be contained in the first metal layers 2a and 3a include Mo, C, and the like.

The second metal layer 2b contains Cu (copper) as a main component. The content of Cu in the second metal layer 2b may be 90% by mass or more, or may be 95% by mass or more. Elements other than Cu that the second metal layer 2b may contain include Mo, C, and the like.

The second metal layer 3b contains Al (aluminum) as a main component. The Al content in the second metal layer 3b may be 90% by mass or more, or may be 95% by mass or more. Elements other than Al that the second metal layer 3b may contain include Si, C, and the like.

The second metal layers 2b, 3b are preferably thicker than the first metal layers 2a, 3a. By forming the second metal layers 2b and 3b formed by the thermal spraying method to be thicker than the first metal layers 2a and 3a formed by the active metal method or the thermal spraying method, for example, it has a sufficient thickness and Metal layers 2 and 3 with little residual stress can be formed on the surface of the ceramic substrate 1 .

The thickness of each of the first metal layers 2a and 3a is, for example, in the range of 0.1 to 0.3 mm, preferably in the range of 0.11 to 0.2 mm, and more preferably 0.12 to 0.15 mm. is more preferably in the range of When the thickness of the first metal layers 2a and 3a is less than 0.1 mm, it tends to be difficult to form the first metal layers 2a and 3a. As a result, residual stress increases and reliability decreases. The thicknesses of the first metal layers 2a and 3a may be substantially the same or different, but are preferably substantially the same from the viewpoint of facilitating the manufacture of the ceramic circuit board 10A.

The thickness of each of the second metal layers 2b and 3b is, for example, in the range of 0.4 to 1.9 mm, preferably in the range of 0.8 to 1.5 mm, and 1.0 to 1.3 mm. is more preferably in the range of If the thickness of the second metal layers 2b and 3b is less than 0.4 mm, the effect of relieving residual stress tends to be insufficient. It tends to take a long time to form the metal layers 2b and 3b. The thicknesses of the second metal layers 2b and 3b may be substantially the same or different, but are preferably substantially the same from the viewpoint of facilitating the manufacture of the ceramic circuit board 10A.

Each of the metal layers 2 and 3 has a thickness of 0.5 to 2.0 mm, preferably 1.0 to 1.8 mm. If the thickness of the metal layer 2 forming the electric circuit is less than 0.5 mm, the current that can flow is limited. As shown in FIG. 3, if the thickness of the metal layer 3 bonded to the base plate 20 via the first solder 21 is less than 0.5 mm, the heat radiation of the ceramic circuit board 10A will be insufficient. Become. On the other hand, when the thickness of the metal layers 2 and 3 exceeds 2.0 mm, the thermal shock resistance becomes insufficient. The thicknesses of the metal layers 2 and 3 may be substantially the same or different, but are preferably substantially the same from the viewpoint of facilitating the manufacture of the ceramic circuit board 10A.

The ceramic circuit board 10A is heated by repeating this cycle 500 times, with one cycle consisting of leaving the ceramic circuit board 10A in an environment of 180° C. for 30 minutes and then leaving the ceramic circuit board 10A in an environment of −45° C. for 30 minutes. It is preferable that the metal layers 2 and 3 do not separate from the ceramic substrate 1 after the cycle test.

<Method for producing ceramic circuit board>
Next, a method for manufacturing the ceramic circuit board 10A will be described. The manufacturing method according to the present embodiment includes (A) a step of forming first metal layers 2a and 3a containing copper as a main component on both surfaces of a ceramic substrate 1, and (B) the first metal layers 2a and 3a. forming the second metal layers 2b and 3b on the surface of the second metal layer 2b and 3b by a thermal spraying method, and in the step (B), a layer containing copper as the main component is formed as the second metal layer 2b, and the second metal A layer containing aluminum as a main component is formed as the layer 3b.

The step (A) is a step of forming the first metal layers 2a and 3a containing copper as a main component on both surfaces of the ceramic substrate 1 . The first metal layers 2a and 3a may be formed by, for example, an active metal method or a thermal spraying method (also referred to as a "cold spraying method").

The active metal method includes a step of bonding metal plates to both sides of the ceramic substrate 1 using a brazing material. The thickness and composition of the metal plates to be joined may be selected according to the thickness and composition of the first metal layers 2a and 3a to be formed. The temperature condition for joining is, for example, in the range of 780 to 810° C., and an appropriate temperature may be set according to the type of brazing material used.

When joining a metal plate containing Cu (Cu plate) to the ceramic substrate 1, for example, Ag (90%)-Cu (10%)-TiH ₂ (3.5%) brazing material is used at a temperature of 800 A Cu plate is bonded to both surfaces of the ceramic substrate 1 at ℃.

The thermal spraying method (also referred to as “cold spraying method”) applies metal powder (Cu-containing powder) at 10 to 270° C. (preferably 20 to 260° C.) to the target surface (the surface of the ceramic base 1). at a speed of 250-1050 m/s (preferably 400-1000 m/s). According to the composition of the first metal layers 2a, 3a to be formed, the composition of the metal powder to be sprayed may be selected, and the temperature conditions and spraying speed may be set. The amount of sprayed metal powder may be adjusted according to the thickness of the first metal layers 2a and 3a. A spray gun, for example, may be used to spray the metal powder. Nitrogen, for example, is used as working gas for injecting the metal powder.

When the metal layers (first metal layers 2a and 3a) are directly formed on the surface of the ceramic base 1 by thermal spraying, the metal powder may be may not adhere well to Therefore, in the step (A), it is preferable to form the first metal layers 2a and 3a by the active metal method.

In the step (B), a second metal layer 2b containing copper as a main component is formed on the surface of the first metal layer 2a by thermal spraying, and a second metal layer 2b containing aluminum as a main component is formed on the surface of the first metal layer 3a. This is the step of forming the double metal layer 3b by thermal spraying.

For the second metal layer 2b, Cu-containing powder at 10 to 270° C. (preferably 20 to 260° C.) is directed toward the surface of the first metal layer 2a at 250 to 1050 m/sec (preferably 400 to 1000 m/sec). formed by spraying at a velocity of According to the composition of the second metal layer 2b to be formed, the composition of the Cu-containing powder to be sprayed may be selected, and the temperature conditions and spraying speed may be set. The spray amount of the Cu-containing powder may be adjusted according to the thickness of the second metal layer 2b.

For the second metal layer 3b, Al-containing powder at 10 to 270° C. (preferably 20 to 260° C.) is directed toward the surface of the first metal layer 3a at 250 to 1050 m/sec (preferably 400 to 1000 m/sec). formed by spraying at a velocity of According to the composition of the second metal layer 3b to be formed, the composition of the Al-containing powder to be sprayed may be selected, and the temperature conditions and spraying speed may be set. The spray amount of the Al-containing powder may be adjusted according to the thickness of the second metal layer 3b.

After forming the first metal layers 2a and 3a in the step (A) and before forming the second metal layers 2b and 3b by thermal spraying in the step (B), at least one of the first metal layers 2a and 3a A circuit pattern may be formed by etching the . In this case, the second metal layer may be formed by thermal spraying while a mask material having openings corresponding to this circuit pattern is placed on the surface of the ceramic substrate 1 . By using the mask material, the second metal layer can be formed only at desired locations. Electroless Ni plating or the like may be applied to the surface of the second metal layer.

According to the manufacturing method described above, a layer containing copper as the main component is formed by thermal spraying as the second metal layer 2b, thereby forming a sufficiently thick metal layer 2 having excellent thermal conductivity compared to the ceramic substrate 1. It is possible to obtain the ceramic circuit board 10A having excellent heat dissipation. Further, by forming a layer containing aluminum as the main component as the second metal layer 3b by thermal spraying, the second metal layer 3b can serve as a buffer layer between the base plate 20 and the base plate 20 . As a result, the ceramic circuit board 10A can maintain its function for a sufficiently long period of time when assembled in the power module 50 as shown in FIG.

In the ceramic circuit board 10A according to the present embodiment, as shown in FIG. 1, the end faces 2c, 3c of the first metal layers 2a, 3a and the end faces 2d, 3d of the second metal layers 2b, 3b are flush with each other. . From the viewpoint of achieving better thermal shock resistance of the ceramic circuit board, as in the ceramic circuit board 10B shown in FIG. It may protrude outside the end faces 2d and 3d, that is, on the end side of the ceramic substrate 1. As shown in FIG. The width of the portion where the end surfaces 2c and 3c protrude from the end surfaces 2d and 3d is, for example, 1 to 1000 μm.

In the above embodiment, the case where the first metal layers 2a and 3a are layers containing copper as a main component was illustrated, but the first metal layers 2a and 3a are layers containing Al (aluminum) as a main component. good too. The Al content in the first metal layers 2a and 3a may be 90% by mass or more, or may be 95% by mass or more. Elements other than Al that the first metal layers 2a and 3a may contain include Si, C, and the like. When this layer is formed by the active metal method, for example, an Al--Cu--Mg clad foil is used as a brazing material, and Al plates are joined to both sides of the ceramic substrate 1 at a temperature of 630.degree. When this layer is formed by thermal spraying, Al-containing powder at 10 to 270° C. (preferably 20 to 260° C.) is directed toward the surface of the ceramic substrate 1 at 250 to 1050 m/sec (preferably 400 to 1000 m/sec.). seconds).

The ceramic circuit board according to the above embodiment is suitably used in a power module, has high heat dissipation properties, and can suppress warping of the base plate that occurs when it is joined to the base plate. Also by cooling, the high adhesion between the ceramic base and the metal layer can be maintained.

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

<Power module>
FIG. 3 is a cross-sectional view showing one embodiment of the power module. As shown in FIG. 3, the power module 50 includes a base plate 20, a ceramics circuit board 10 bonded onto the base plate 20 via a first solder 21, and a second solder 22 on the ceramics circuit board 10. and a semiconductor element 6 that is joined via the . The ceramic circuit board 10 is a ceramic circuit board 10A or a ceramic circuit board 10B, and the metal layer 2 forms an electric circuit (metal circuit). The metal layer 3 may or may not form a metal circuit.

The base plate 20 is joined to the metal layer 3 via the first solder 21 . The semiconductor element 6 is bonded to a predetermined portion of the metal layer 2 via a second solder 22, and is also bonded to a predetermined portion of the metal layer 2 with a metal wire 7 such as an aluminum wire (aluminum wire). there is Each of the components provided on the base plate 20 is covered with, for example, a hollow box-shaped resin housing 25 with one side open and housed in the housing 25 . A hollow portion between the base plate 20 and the housing 25 is filled with a filler 28 such as silicone gel. An electrode 9 penetrating the housing 25 is joined to a predetermined portion of the metal layer 2 via a third solder 23 so as to be electrically connected to the outside of the housing 8 .

An edge of the base plate 20 is formed with a mounting hole 20a for screwing a heat radiating component to the power module 50, for example. The number of mounting holes 20a is, for example, four or more. At the edge of the base plate 20, instead of the mounting hole 20a, a mounting groove may be formed so that the side wall of the base plate 20 has a U-shaped cross section.

Since the power module 50 includes the ceramic circuit board according to the present embodiment described above, it can be suitably used as a drive inverter for trains or automobiles in which high withstand voltage, high output, etc. are required.

EXAMPLES 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)
A silicon nitride (Si ₃ N ₄ ) substrate (size: 50 mm×60 mm×0.32 mmt) was used as a ceramic substrate. Cu plates (thickness: 0.1 mm, equivalent to first metal layers 2a and 3a) were joined to both sides of the ceramic substrate at a temperature of 800° C. using Ag—Cu—TiH ₂ brazing material (step (A)). . Subsequently, a Cu circuit (corresponding to the second metal layer 2b) having a thickness of 0.9 mm was laminated on the Cu plate on one side of the ceramic substrate by a thermal spray method (cold spray method) under the following conditions ( (B) step). In addition, an Al circuit (corresponding to the second metal layer 3b) having a thickness of 0.9 mm was laminated on the Cu plate on the other side of the ceramic substrate by a thermal spray method (cold spray method) under the following conditions (( B) step). After the obtained laminate was annealed at a temperature of 300° C., the surfaces of the Cu circuit and the Al circuit were subjected to electroless Ni plating, and a ceramic circuit board according to this example was produced. The "Cu circuit" and "Al circuit" in this example are formed on the entire surface of the ceramic substrate.
<Conditions of thermal spraying method (formation of Cu circuit)>
・Temperature of Cu powder: 260°C
・Cu powder spraying speed: 800 m / sec ・Working gas: nitrogen <Conditions of thermal spraying method (formation of Al circuit)>
・Temperature of Al powder: 260°C
・Al powder spraying speed: 800 m / sec ・Working gas: nitrogen

( Reference Examples 2, 4, 6, 8 and Examples 3, 5, 7 )
A silicon nitride (Si ₃ N ₄ ) substrate having a thickness shown in Table 1 was used, and a first metal layer made of a material (Cu or Al) shown in Table 1 was formed on both sides of the substrate. A ceramic circuit board was produced in the same manner as in Example 1, except that a Cu circuit and an Al circuit having a thickness shown in Table 1 were formed on the surface of the first metal layer by a thermal spray method (cold spray method). .

( Reference example 9)
A silicon nitride (Si ₃ N ₄ ) substrate (size: 50 mm×60 mm×0.32 mmt) was used as a ceramic substrate. An Al layer having a thickness of 0.1 mm was formed on both sides of the ceramic substrate by thermal spraying (cold spraying) under the following conditions.
<Conditions of thermal spraying method (formation of Al layer)>
・Temperature of Al powder: 260°C
・Al powder spraying speed: 800 m / sec ・Working gas: nitrogen

Subsequently, a Cu circuit having a thickness of 0.9 mm was laminated on the Al layer on one side of the ceramic substrate by thermal spraying (cold spraying) under the following conditions (step (B)). Further, an Al circuit having a thickness of 0.9 mm was laminated on the Al circuit on the other side of the ceramic substrate by thermal spraying (cold spray method) under the following conditions (step (B)). After the obtained laminate was annealed at a temperature of 300° C., the surfaces of the Cu circuit and the Al circuit were plated with electroless Ni to produce a ceramic circuit board.
<Conditions of thermal spraying method (formation of Cu circuit)>
・Temperature of Cu powder: 260°C
・Cu powder spraying speed: 800 m / sec ・Working gas: nitrogen <Conditions of thermal spraying method (formation of Al circuit)>
・Temperature of Al powder: 260°C
・Al powder spraying speed: 800 m / sec ・Working gas: nitrogen

(Comparative Examples 1 to 3)
A silicon nitride (Si ₃ N ₄ ) substrate having a thickness shown in Table 1 was used, and a Cu circuit and an Al circuit having the thickness shown in Table 1 were formed by thermal spraying (cold spray method). A ceramic circuit board was produced in the same manner as in Example 1 except for the above.

(Comparative Example 4)
A silicon nitride (Si ₃ N ₄ ) substrate having a thickness shown in Table 1 was used, and a Cu circuit and an Al circuit having the thickness shown in Table 1 were formed by thermal spraying (cold spray method). A ceramic circuit board was produced in the same manner as in Reference Example 9 except for the above.

(Comparative Example 5)
A silicon nitride (Si ₃ N ₄ ) substrate (size: 50 mm×60 mm×0.32 mmt) was used as a ceramic substrate. A Cu plate (thickness: 0.3 mm) was joined to both sides of the ceramic substrate at a temperature of 800° C. using Ag—Cu—TiH ₂ brazing material. A ceramic circuit board was produced through a step of applying electroless Ni plating to the surface of the Cu plate.

(Comparative Example 6)
A silicon nitride (Si ₃ N ₄ ) substrate (size: 50 mm×60 mm×0.32 mmt) was used as a ceramic substrate. Using an Al--Cu--Mg clad foil as a brazing material, Al plates (thickness: 2.0 mm) were joined to both sides of the ceramic substrate at a temperature of 630° C., and then Al circuits were formed by etching. After the obtained laminate was annealed at a temperature of 300° C., the surface of the Al circuit was plated with electroless Ni to produce a ceramic circuit board.

<Apparent Thermal Conductivity of Ceramic Circuit Board>
The apparent thermal conductivity of the ceramic circuit boards according to Examples 1 , 3, 5, 7, Reference Examples 2, 4, 6, 8, 9 and Comparative Examples 1 to 6 was measured using a NETZSCH flash analyzer (LFA467). was obtained as follows. The thermal diffusivity of the blackened sample (ceramic circuit board) was measured at a flash voltage of 200V. The apparent thermal conductivity of the sample was calculated using this measured value and the apparent density and apparent specific heat capacity calculated from the thickness of each layer and the sample size by the law of addition. The physical properties of silicon nitride and Cu are given below. Table 2 shows the results.
Silicon nitride (Si ₃ N ₄ ): density 3.2 g/cm ³ , specific heat capacity 0.68 J/g·K
Cu: density 8.89 g/cm ³ , specific heat capacity 0.389 J/g·K
Al: density 2.7 g/cm ³ , specific heat capacity 0.88 J/g·K

<Crack evaluation in heat cycle test>
An Al base plate (size 140 mm × 190 mm × 5 mm) were respectively joined with eutectic solder to prepare a sample to be evaluated (a ceramic circuit board with a base plate). A heat cycle test of 500 cycles was carried out with one cycle consisting of leaving the sample in an environment of 180° C. for 30 minutes and then leaving the sample in an environment of −45° C. for 30 minutes. After the heat cycle test, the presence or absence of abnormalities in the samples (separation of the metal circuit and cracks in the ceramic substrate) was visually confirmed. Table 2 shows the results.

DESCRIPTION OF SYMBOLS 1... Ceramics base material 2, 3... Metal layer 2a, 3a... First metal layer 2b, 3b... Second metal layer 2c, 3c... End surface of first metal layer 2d, 3d... Second metal layer , 10A, 10B... Ceramic circuit board.

Claims (7)

a ceramic substrate having a thickness in the range of 0.2 to 1.5 mm;
metal layers provided on both sides of the ceramic base;
with
A method for manufacturing a ceramic circuit board, wherein the metal layer provided on at least one surface of the ceramic substrate forms a metal circuit,
(A) forming a first metal layer containing copper as a main component and having a thickness in the range of 0.1 to 0.3 mm on both surfaces of the ceramic substrate;
(B) forming a second metal layer on the surface of the first metal layer by a cold spray method;
including
In the step (B), a layer containing copper as a main component is formed as the second metal layer located on one side of the ceramic base, and the second metal layer located on the other side of the ceramic base is formed. Forming a layer containing aluminum as a main component as a bimetallic layer,
Manufacture of a ceramic circuit board, wherein the metal layer has a multilayer structure including the first metal layer and the second metal layer in this order from the ceramic substrate side and has a thickness of 0.5 to 2.0 mm. Method. 2. The method of manufacturing a ceramic circuit board according to claim 1, wherein said second metal layer is thicker than said first metal layer. a ceramic substrate having a thickness in the range of 0.2 to 1.5 mm;
metal layers provided on both sides of the ceramic base;
with
A ceramic circuit board in which the metal layer provided on at least one surface of the ceramic substrate forms a metal circuit,
The metal layer has a multilayer structure including a first metal layer and a second metal layer in this order from the ceramic substrate side and has a thickness of 0.5 to 2.0 mm,
The first metal layer is mainly composed of copper and has a thickness in the range of 0.1 to 0.3 mm,
The second metal layer located on one side of the ceramic base is mainly composed of copper and is formed by a cold spray method,
The ceramic circuit board, wherein the second metal layer located on the other surface side of the ceramic substrate is mainly composed of aluminum and is formed by a cold spray method. a ceramic substrate having a thickness in the range of 0.2 to 1.5 mm;
a metal layer provided on one side and the other side of the ceramic base;
with
A ceramic circuit board in which the metal layer provided on at least one surface of the ceramic substrate forms a metal circuit,
The metal layer has a multilayer structure including a first metal layer and a second metal layer in this order from the ceramic substrate side and has a thickness of 0.5 to 2.0 mm,
The first metal layer is mainly composed of copper and has a thickness in the range of 0.1 to 0.3 mm,
The second metal layer located on one side of the ceramic base is mainly composed of copper and has a thickness in the range of 0.4 to 1.9 mm,
The ceramic circuit board, wherein the second metal layer located on the other side of the ceramic substrate is mainly composed of aluminum and has a thickness in the range of 0.4 to 1.9 mm. After leaving the ceramic circuit board in an environment of 180° C. for 30 minutes and then leaving the ceramic circuit board in an environment of −45° C. for 30 minutes as one cycle, this cycle is repeated 500 times. After a heat cycle test,
5. The ceramic circuit board according to claim 3, wherein said metal circuit does not separate from said ceramic substrate. 6. The ceramic circuit board according to claim 3, wherein said ceramic substrate is made of Si ₃ N ₄ and has a thickness of 0.2 to 1.5 mm. 3. The end face of the first metal layer and the end face of the second metal layer are flush with each other, or the end face of the first metal layer protrudes outside the end face of the second metal layer. 7. The ceramic circuit board according to any one of -6.

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