Circuit board and semiconductor power module using the circuit board

Abstract

A circuit board in which circuit wiring is soldered to a ceramic substrate and which has low cost and high reliability even if chamfered regions are formed in cross-sectional corners of the circuit wiring, and a semiconductor power module using the circuit board are provided. The circuit board according to the present invention, in which circuit wiring is soldered to one main surface of a ceramic substrate, is characterized in that the circuit wiring is made of a metal material having a thickness of 0.4 mm or more and has chamfered regions at the corners of the end face when the circuit wiring is viewed in the cross-sectional direction, and a space between the chamfered region of the circuit wiring and the ceramic substrate is filled with a soldering material and the soldering material forms a fillet that skirts outward from the end face of the circuit wiring when the circuit board is viewed in the cross-sectional direction.

Description

Technical Field

[0002]

[0001] The present invention relates to a circuit board suitable for a semiconductor power module, and particularly to a circuit board in which circuit wiring is brazed and joined to one main surface of an electrical insulating board, and a semiconductor power module using the circuit board.

Background Art

[0002] In industrial machines and vehicles (e.g., automobiles, railway vehicles), in recent years, from the viewpoints of precise operation control and energy saving, the electrification and electronic control of power sources have been rapidly progressing. Along with this, the importance of semiconductor power modules responsible for power control of these power sources has been extremely increasing. In a semiconductor power module, usually, a plurality of power semiconductor elements for controlling large power are mounted on a circuit board, and each power semiconductor element is controlled simultaneously / synchronously.

[0003] Typical power semiconductor elements include, for example, IGBT (Insulated Gate Bipolar Transistor), power MOSFET (Power Metal Oxide Semiconductor Field Effect Transistor), etc.

[0004] Also, a circuit board in which circuit wiring is disposed on one main surface of a ceramic board excellent in electrical insulation, heat resistance, and thermal conductivity, and a heat dissipation metal member is disposed on the other main surface is often used. Examples of the ceramic board include aluminum nitride (AlN) board, silicon nitride (Si3N4) board, aluminum oxide (Al2O3) board, silicon carbide (SiC), alumina zirconia (ZTA) board, beryllium oxide (BeO) board, etc. The joining of the circuit wiring and the ceramic board, and the joining of the heat dissipation metal member and the ceramic board are usually performed by brazing material.

[0005] There is a strong demand for higher power output and miniaturization of rotating electric machines (e.g., motors), and the semiconductor power modules that control these rotating electric machines are also required to be more powerful and smaller. When attempting to increase the power output and miniaturize semiconductor power modules, the heat density increases, so thicker circuit wiring is required to improve heat dissipation characteristics. However, thickening the circuit wiring leads to an increase in the etching process required for circuit formation and an increase in the spacing between circuit patterns due to the side edge shape, resulting in increased manufacturing costs and making miniaturization difficult.

[0006] Therefore, a process in which a thick metal plate is pre-processed into the shape of a circuit wiring pattern and then attached to an insulating substrate is being considered. However, when the circuit wiring pattern is formed by pre-processing, burrs may be generated during processing, or the surface roughness of the cut surface may become rough. If the surface roughness of the cut surface becomes rough, sparks may be generated from these points, potentially causing current to flow between adjacent circuit wirings, thus hindering the proper use of the power module.

[0007] Patent Document 1 (JP 2007-053349) reports one technology to address such problems. Patent Document 1 discloses an insulating substrate in which a conductor pattern is arranged on the surface side of a ceramic substrate, wherein the rising surface of the outer surface of the conductor constituting the conductor pattern, which rises from the surface side of the ceramic substrate, is configured to rise substantially perpendicular to the direction along the surface of the ceramic substrate, the conductor pattern is joined to the surface of the ceramic substrate with brazing material, and at least the lower side of the rising surface of the conductor in the direction rising from the surface side of the ceramic substrate is covered with the brazing material.

[0008] According to Patent Document 1, it is possible to achieve high current and high voltage in semiconductor power modules, and even with such a configuration, it is possible to suppress the size increase of the insulating substrate and furthermore, to achieve low-cost production. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2007-053349 [Overview of the Initiative] [Problems that the invention aims to solve]

[0010] However, due to technological advancements, circuit wiring is becoming thicker than what was assumed in Patent Document 1. Since the height of burrs increases in relation to the plate thickness, it is difficult to join parts while ignoring the burrs after processing, and burr removal processing is required after processing.

[0011] This removal process creates chamfered areas (for example, rounded, smoothly cut R-surfaces or chamfered surfaces cut at an angle of approximately 45°) at the cross-sectional corners of the circuit wiring. As a result, the joint structure becomes prone to stress concentration at the edges of the joint surface with the insulating substrate, creating another problem: cracking and delamination are likely to occur at the insulating substrate and its interface due to thermal stress caused by power cycles and temperature cycles.

[0012] Therefore, the object of the present invention is to provide a low-cost and highly reliable circuit board and a semiconductor power module using the circuit board, even when chamfered areas are formed at the cross-sectional corners of the circuit wiring. [Means for solving the problem]

[0013] (I) One aspect of the present invention is a circuit board in which circuit wiring is brazed to one main surface of a ceramic substrate, The circuit wiring is made of a metal material having a thickness of 0.4 mm or more, and when the circuit wiring is viewed from the cross-sectional direction, it has a chamfered area at the corner of the end face. When the circuit board is viewed in cross-sectional direction, the brazing material fills the space between the chamfered region of the circuit wiring and the ceramic substrate, and the brazing material forms a fillet that extends outward beyond the end face of the circuit wiring. Ori , The height of the chamfered region is greater than the thickness of the brazing material used to join the circuit wiring and the ceramic substrate. The trailing length of the fillet is at least twice the thickness of the brazing material. The present invention provides a circuit board characterized by the following features.

[0014] In the present invention, the following improvements and modifications can be made to the circuit board (I) described above. 。 (i The trailing length of the fillet is less than the height of the chamfered area. ( ii The ceramic substrate is an aluminum nitride (AlN) substrate, a silicon nitride (Si3N4) substrate, an aluminum oxide (Al2O3) substrate, a silicon carbide (SiC) substrate, an alumina zirconia (ZTA) substrate, or a beryllium oxide (BeO) substrate. ( iii The circuit wiring is made of a metallic material having an electrical conductivity of 50% or higher than IACS (International Standard Soft Copper). ( iv The brazing material is a material containing 50% by mass or more of silver (Ag) or a material containing 70% by mass or more of Cu. ( v The material containing 50% by mass or more of Ag is a material containing 50% by mass or more and 80% by mass of Ag, 15% by mass or more and 30% by mass of Cu, and more than 0% by mass and 5% by mass or less of titanium (Ti). The material containing 70% by mass or more of Cu is a material containing 70% by mass or more and less than 95% by mass of Cu, 5% by mass or more and 25% by mass of magnesium (Mg), and more than 0% by mass and 5% by mass or less of Ti. ( vi The circuit board has a heat-dissipating metal member brazed to the other main surface of the ceramic substrate. ( viiThe heat-dissipating metal member is made of the same material as the circuit wiring, has a heat-dissipating chamfer region at the corner of the end face when the heat-dissipating metal member is viewed in the cross-sectional direction, and when the circuit board is viewed in the cross-sectional direction, the brazing material fills the space between the heat-dissipating chamfer region and the ceramic substrate, and the brazing material forms a fillet that extends outward from the end face of the heat-dissipating metal member. ( viii )An interfacial reaction layer is formed between the ceramic substrate and the brazing material.

[0015] (II) Another aspect of the present invention is a semiconductor power module in which a power semiconductor element is mounted on a circuit board, The circuit board is the above circuit board, and a semiconductor power module is provided.

Effect of the Invention

[0016] According to the present invention, even when a chamfer region is formed at the cross-sectional corner of the circuit wiring, a circuit board with low cost and high reliability and a semiconductor power module using the circuit board can be provided.

Brief Description of the Drawings

[0017] [Figure 1] It is a schematic cross-sectional view showing an example of a semiconductor power module according to an embodiment of the present invention. [Figure 2] It is a circuit board according to an embodiment of the present invention, and is an enlarged schematic cross-sectional view showing an example of a joint portion between a circuit wiring and a ceramic substrate. [Figure 3] It is a circuit board according to an embodiment of the present invention, and is an enlarged schematic cross-sectional view showing another example of a joint portion between a circuit wiring and a ceramic substrate. [[ID=​​​​​​When circuit wiring with chamfered edges is brazed to a ceramic substrate, if a gap is created between the chamfered edge and the ceramic substrate where the brazing material is not filled, this gap can act as a stress concentration point due to thermal stress caused by temperature cycles, etc., which can easily lead to cracking of the brazed material and delamination of the circuit wiring. The inventors diligently researched circuit boards that can ensure high bonding reliability while using pre-patterned thick-film circuit wiring (for example, circuit wiring prepared by shearing), and as a result, completed the present invention.

[0019] Embodiments of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the embodiments described herein, and it is possible to combine it with prior art or improve upon it without departing from the technical spirit of the invention. In addition, the same reference numerals may be used for synonymous components, and redundant explanations may be omitted.

[0020] [First Embodiment] (Semiconductor power module) Figure 1 is a schematic cross-sectional view showing an example of a semiconductor power module according to one embodiment of the present invention. In the semiconductor power module 100 shown in Figure 1, power semiconductor elements 20 are mounted on one side of a circuit board 10, and a heat sink 30 is thermally connected to the other side of the circuit board 10.

[0021] The circuit board 10 has circuit wiring 13 bonded to one main surface of the ceramic substrate 11 via brazing material 12, and a heat dissipation metal member 14 bonded to the other main surface of the ceramic substrate 11 via brazing material 12. The power semiconductor element 20 has a first input / output terminal bonded to one of the circuit wirings 13 via conductive bonding material 21 (e.g., solder), and a second input / output terminal and signal electrodes bonded to the other of the circuit wirings 13 via conductive wire 22 (e.g., bonding wire). The heat sink 30 is bonded to the heat dissipation metal member 14 via heat transfer bonding material 31 (e.g., solder).

[0022] The ceramic substrate 11 is preferably selected by comprehensively considering thermal conductivity, thermal expansion coefficient, thermal shock resistance, etc. For example, AlN substrates, Si3N4 substrates, Al2O3 substrates, SiC substrates, ZTA substrates, or BeO substrates can be suitably used.

[0023] The circuit wiring 13 is not particularly limited as long as it is made of a metal material, but from the viewpoint of improving heat dissipation and suppressing Joule heating, it is preferable to use a metal material with good conductivity, and more preferably a metal material having conductivity of 50% IACS or higher. For example, pure Cu (e.g., tough pitch copper, deoxidized copper, oxygen-free copper), Cu alloys (e.g., Cu-Fe alloy, Cu-Cr alloy, Cu-Zr alloy, alumina-dispersed copper), Ag, and Al can be suitably used. From the viewpoint of heat dissipation, the thickness of the circuit wiring 13 is preferably 0.4 mm or more, more preferably 0.5 mm or more, and even more preferably greater than 0.8 mm. On the other hand, from the viewpoint of stress, it is preferably 2 mm or less, more preferably 1.8 mm or less, and even more preferably 1.6 mm or less.

[0024] Although the details of the circuit board 10 will be described later, the semiconductor power module 100 according to the present invention has the advantage of being able to handle higher power and smaller size than conventional modules because the circuit board 10 is designed to accommodate higher power and smaller wiring spacing than conventional modules.

[0025] [Second Embodiment] (Circuit board) Figure 2 is a schematic enlarged cross-sectional view showing an example of a joint between circuit wiring and a ceramic substrate, which is a circuit board according to one embodiment of the present invention. As shown in Figure 2, the circuit board 10a has circuit wiring 13a joined to one main surface of the ceramic substrate 11 via brazing material 12.

[0026] Figure 2 and Figure 3, described later, illustrate the case of circuit wiring formed by shearing and punching, but the method of forming circuit wiring used in the present invention is not limited to shearing / punching. When circuit wiring is formed by shearing / punching, the end face, when viewed from the cross-sectional direction, usually has a first region (also called the burr region), a second region (height c, also called the shear surface region), and a third region (height b, also called the fracture surface region), and burrs are generated at the end of the third region. The circuit wiring used in the present invention has a chamfered region (height a) formed at the lower end corner of the end face (the corner facing the ceramic substrate).

[0027] The height a of the chamfered area (corresponding to the radius of curvature of the R chamfer) is preferably greater than the joining thickness d of the brazing material 12, and more preferably twice or more. By making the height a of the chamfered area greater than the joining thickness d of the brazing material 12, the influence of thermal stress can be reduced. Specifically, the height a of the chamfered area is preferably 0.02 mm or more, more preferably 0.05 mm or more, and even more preferably 0.1 mm or more. It is also preferably 0.5 mm or less, more preferably 0.3 mm or less, and even more preferably 0.25 mm or less.

[0028] From the viewpoint of preventing unwanted current flow between adjacent wirings in the circuit wiring 13a, it is desirable that the surface roughness of the wiring sides (end faces when viewed from the cross-sectional direction) be small. For example, an arithmetic mean roughness Ra (according to JIS B0651) of 3.2 μm or less is preferred, and 1.6 μm or less is more preferred. For this reason, polishing of the wiring sides (end faces) may be performed as needed.

[0029] Preferably, the brazing material 12 fills the space between the chamfered region of the circuit wiring 13a and the ceramic substrate 11, and forms a fillet 12a that extends outward from the end face. There are no particular limitations on the bonding thickness d of the brazing material 12, but it is preferable to control it within a range of, for example, 0.01 mm or more and 0.1 mm or less.

[0030] From the viewpoint of reducing the influence of thermal stress, the height h of the fillet 12a is preferably such that the chamfered area is completely covered, and from the viewpoint of controlling the hem length g of the fillet 12a, it is preferable to control it up to the third area. That is, the height h of the fillet 12a is preferably greater than or equal to the sum of the height a of the chamfered area and the joint thickness d of the brazing material, and less than or equal to the sum of the height b of the third area and the joint thickness d of the brazing material.

[0031] From the viewpoint of reducing the influence of thermal stress, the hem length g of the fillet 12a is preferably greater than the joint thickness d of the brazing material 12, and more preferably twice or more. On the other hand, from the viewpoint of preventing unwanted current flow between adjacent wirings of the circuit wiring 13a, the hem length g of the fillet 12a is preferably less than or equal to the height a of the chamfered area.

[0032] Furthermore, in order to improve the bonding between the ceramic substrate 11 and the brazing material 12, it is preferable that an interfacial reaction layer 11a be formed between the ceramic substrate 11 and the brazing material 12. For example, a TiN layer can be suitably used as the interfacial reaction layer 11a.

[0033] The brazing material 12 can preferably be a silver brazing material (e.g., Ag-Cu-Ti material, Ag-Cu-Sn-Ti material, Ag-Cu-Sn-In-Ti material) or a copper brazing material (e.g., Cu-Mg-Ti material). More specifically, as the silver brazing material, a material containing 55% to 75% by mass of Ag, 20% to 35% by mass of Cu, 1% to 7% by mass of Ti, 8% or less by mass of Sn (tin), and 12% or less by mass of In (indium) is preferred. As the copper brazing material, a material containing 70% to less than 95% by mass of Cu, 5% to 25% by mass of Mg, and more than 0% by mass and 5% or less by mass of Ti is preferred.

[0034] Furthermore, the above-mentioned silver solder material and copper solder material may contain one or more of the following as melting point adjusting components in a total amount of 5% by mass or less: Al, Si, P (phosphorus), Ca (calcium), Mn (manganese), Zn (zinc), Ga (gallium), Ge (germanium), As (arsenic), Sr (strontium), Sb (antimony), Ba (barium), and Bi (bismuth). In addition, one or more of the following as components that promote the formation of the interfacial reaction layer 11a may be contained in a total amount of 5% by mass or less: Sc (scandium), Y (yttrium), lanthanides, Zr (zirconium), Hf (hafnium), V (vanadium), Nb (niobium), Ta (tantalum), Cr (chromium), Mo (molybdenum), and W (tungsten).

[0035] There are no particular limitations on the form of the brazing material 12, and conventional forms (e.g., paste, foil) can be used as appropriate. Furthermore, there are no particular limitations on the preparation of the brazing material 12, and conventional methods can be used as appropriate.

[0036] As mentioned above, in the circuit board 10 shown in Figure 1, a heat-dissipating metal member 14 is provided on the main surface opposite to the main surface of the ceramic substrate 11 on which the circuit wiring 13 is arranged. In the present invention, the provision of the heat-dissipating metal member 14 is not essential, but from the viewpoint of thermal countermeasures for semiconductor power modules 100 that aim for high power and miniaturization, it is preferable to provide the heat-dissipating metal member 14.

[0037] To avoid repetition, a detailed explanation will be omitted, but the heat dissipation metal member 14 is joined to the ceramic substrate 11 via brazing material 12 in a structure similar to that of the circuit wiring 13. Furthermore, from the viewpoint of suppressing warping of the circuit board 10, it is preferable that the heat dissipation metal member 14 is made of the same material and has the same thickness as the circuit wiring 13.

[0038] [Third Embodiment] (Circuit board) Figure 3 is a schematic cross-sectional view of an enlarged section of a circuit board according to one embodiment of the present invention, showing another example of the joint between the circuit wiring and the ceramic substrate. As shown in Figure 3, circuit board 10b differs from circuit board 10a in that the shape of the chamfered area is C-chamfered, but otherwise they are the same.

[0039] Naturally, circuit board 10b performs the same function and effect as circuit board 10a. [Examples]

[0040] The present invention will be described in more detail below with reference to experimental examples. However, the present invention is not limited to these experimental examples.

[0041] [Experiment 1] (Preparation of Examples 1-6 and Comparative Examples 1-4) For the ceramic substrates, we prepared Si3N4 substrates (width 11 mm × length 42 mm × thickness 0.32 mm) and AlN substrates (width 11 mm × length 42 mm × thickness 0.635 mm). For the circuit wiring and heat dissipation metal components, we prepared sheared oxygen-free copper plates (width 10 mm × length 40 mm × thickness 1-1.5 mm), and chamfered edges were applied to the burrs at the end of the processed sections (chamfered area height a = 0.1-0.2 mm).

[0042] The following brazing materials were prepared: silver solder-1 (60Ag-25Cu-10In-5Ti, mass%), silver solder-2 (66Ag-29.5Cu-3Sn-1.5Ti, mass%), and copper solder-1 (89Cu-10Mg-1Ti, mass%). The brazing materials were prepared in the form of a paste (binding agent: polyisobutyl methacrylate 5% by mass, solvent: terpineol 10% by mass, brazing material powder: remainder) and foil (thickness 0.05 mm).

[0043] Brazing material (paste or foil) was applied or placed on both main surfaces of the ceramic substrate in a size 0.05 mm larger than the width and length of the circuit wiring and heat dissipation metal component, respectively. The circuit wiring and heat dissipation metal component were then placed on top of the brazing material. Next, the circuit wiring and heat dissipation metal component were pressed against the ceramic substrate at 0.01 to 0.1 MPa while the temperature was raised to 760 to 820°C and held for 60 minutes to perform the brazing process. This resulted in the production of 11 experimental samples each for Examples 1 to 6 and Comparative Examples 1 to 4. The specifications of each experimental sample are shown in Table 1 below.

[0044] [Experiment 2] (Cross-sectional observation and evaluation of joint reliability) One sample was selected from each of the experimental specimens prepared for Examples 1-6 and Comparative Examples 1-4. A scanning electron microscope (SEM) was used to observe the cross-sections of the joints between the circuit wiring and the ceramic substrate, and between the heat dissipation metal component and the ceramic substrate. For each specimen, the height of the chamfered area, the joint thickness, and the fillet hem length were measured at four joint locations, and the average values ​​were calculated. The results are shown in Table 1.

[0045] The bonding reliability was evaluated by performing temperature cycling tests on 10 experimental samples each from Examples 1-6 and Comparative Examples 1-4. The test conditions consisted of "holding at -40°C for 30 minutes" → "holding at room temperature for 10 minutes" → "holding at 250°C for 30 minutes" → "holding at room temperature for 10 minutes," with 3000 cycles performed. Afterwards, the presence or absence of cracks in the bonding areas of the experimental samples was investigated using an ultrasonic flaw detection device (SAT). Samples with one or fewer cracks out of 10 were evaluated as "pass," and those with two or more cracks out of 10 were evaluated as "fail." The results are shown in Table 1.

[0046] [Table 1]

[0047] As shown in Table 1, Examples 1 to 6 (experimental samples in which the brazing material fills the space between the chamfered region and the ceramic substrate, and the brazing material forms a fillet that extends beyond the shear surface region) were confirmed to have satisfactory bonding reliability. On the other hand, Comparative Examples 1 to 4 (experimental samples in which the brazing material does not completely fill the space between the chamfered region and the ceramic substrate, and the fillet extension length is a negative number) were confirmed to have unsatisfactory bonding reliability.

[0048] The embodiments and experimental examples described above are explained to aid in understanding the present invention, and the present invention is not limited to the specific configurations described. For example, it is possible to replace some of the configurations of the embodiments with configurations that are common knowledge to those skilled in the art, and it is also possible to add configurations that are common knowledge to those skilled in the art to the configurations of the embodiments. In other words, the present invention allows for deletion, substitution with other configurations, and addition of other configurations to some of the configurations of the embodiments and experimental examples specified herein, as long as it does not depart from the technical spirit of the invention. [Explanation of symbols]

[0049] 100...Semiconductor power module, 10, 10a, 10b...Circuit board, 11...Ceramic substrate, 11a...Interface reaction layer, 12...Brazing material, 12a...Fillet, 13, 13a, 13b...Circuit wiring, 14...Metal component for heat dissipation, 20...Power semiconductor element, 21...Conductive bonding material, 22...Conductive wire, 30...Heat sink, 31...Heat transfer bonding material.

Claims

1. A circuit board in which circuit wiring is brazed to one main surface of a ceramic substrate, wherein the circuit wiring is made of a metal material having a thickness of 0.4 mm or more, and when the circuit wiring is viewed from the cross-sectional direction, it has a chamfered region at the corner of the end face. When the circuit board is viewed in cross-sectional direction, the brazing material fills the space between the chamfered region of the circuit wiring and the ceramic substrate, and the brazing material forms a fillet that extends outward from the end face of the circuit wiring. The height of the chamfered region is greater than the thickness of the brazing material used to join the circuit wiring and the ceramic substrate. The trailing length of the fillet is at least twice the thickness of the brazing material. A circuit board characterized by the following features.

2. In the circuit board according to claim 1, A circuit board characterized in that the tail length of the fillet is smaller than the height of the chamfered area.

3. In the circuit board according to claim 1, The circuit board is characterized in that the ceramic substrate is an aluminum nitride substrate, a silicon nitride substrate, an aluminum oxide substrate, a silicon carbide substrate, an alumina zirconia substrate, or a beryllium oxide substrate.

4. In the circuit board according to claim 1, The circuit board is characterized in that the circuit wiring is made of a metallic material having an conductivity of 50% IACS or higher.

5. In the circuit board according to claim 1, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

6. In the circuit board according to claim 5, The material containing 50% by mass or more of silver is a material containing 50% by mass or more and 80% by mass or less of silver, 15% by mass or more and 30% by mass or less of copper, and more than 0% by mass and 5% by mass or less of titanium. The material containing 70% by mass or more of copper is a material containing 70% by mass or more and less than 95% by mass of copper, 5% by mass or more and 25% by mass or less of magnesium, and more than 0% by mass and 5% by mass or less of titanium. A circuit board characterized by the following features.

7. In the circuit board according to claim 1, The circuit board is characterized in that a heat-dissipating metal member is brazed to the other main surface of the ceramic substrate.

8. In the circuit board according to claim 7, The heat dissipation metal member is made of the same material as the circuit wiring, and when viewed in cross-sectional direction, the heat dissipation metal member has a heat dissipation metal chamfer region at the corner of its end face. When the circuit board is viewed in cross-sectional direction, the brazing material fills the space between the heat-dissipating metal chamfered region and the ceramic substrate, and the brazing material forms a fillet that extends outward from the end face of the heat-dissipating metal member. A circuit board characterized by the following features.

9. In the circuit board according to claim 1, A circuit board characterized in that an interfacial reaction layer is formed between the ceramic substrate and the brazing material.

10. A semiconductor power module in which power semiconductor elements are mounted on a circuit board, A semiconductor power module characterized in that the circuit board is the circuit board described in claim 1.

11. In the circuit board according to claim 2, The circuit board is characterized in that the ceramic substrate is an aluminum nitride substrate, a silicon nitride substrate, an aluminum oxide substrate, a silicon carbide substrate, an alumina zirconia substrate, or a beryllium oxide substrate.

12. In the circuit board according to claim 2, The circuit board is characterized in that the circuit wiring is made of a metallic material having an conductivity of 50% IACS or higher.

13. In the circuit board according to claim 3, The circuit board is characterized in that the circuit wiring is made of a metallic material having an conductivity of 50% IACS or higher.

14. In the circuit board according to claim 11, The circuit board is characterized in that the circuit wiring is made of a metallic material having an conductivity of 50% IACS or higher.

15. In the circuit board according to claim 2, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

16. In the circuit board according to claim 3, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

17. In the circuit board according to claim 4, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

18. In the circuit board according to claim 11, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

19. In the circuit board according to claim 12, The aforementioned brazing material is a circuit board characterized by being a material containing 50% by mass or more of silver or a material containing 70% by mass or more of copper.

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