JP2004022914A - Insulated circuit board and its cooling structure and power semiconductor device and its cooling structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an insulated circuit board, a cooling structure therefor, a power semiconductor device and a cooling structure therefor in which a structure which is cooled by a cooling liquid-state medium is bonded by frictional stirring and bonding, heat radiation characteristics are improved and high reliability is provided. <P>SOLUTION: In the insulated circuit board in which a circuit board composed of copper or copper alloy, a ceramics wafer and a radiation shield composed of copper or steel alloy are successively bonded by brazing material, the radiation shield has a plurality of plate-like fins or stick-like fins except for its full peripheral portion, a plate portion thicker than the fins is integrally formed on both outer sides of the arrangement of the plate-like fins, and a plate portion thicker than a diameter of the stick-like fins is integrally formed on both outer sides of one of arrangements of the stick-like fins. Besides, the insulated circuit board is composed of the power semiconductor device in which a semiconductor power element is packaged on the circuit board of the insulated circuit board. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an insulated circuit board for heat dissipation used in a power module on which a semiconductor power element is mounted, a cooling structure thereof, and a power semiconductor device and a cooling structure thereof.
[0002]
[Prior art]
Conventionally, as a heat radiating board for a semiconductor power element, an insulating circuit board composed of a laminate of a circuit board, a ceramics board and a heat radiating board is joined to a heat sink plate made of an Al-SiC composite material by using an Al-Si brazing material. And the like are known from JP-A-10-65075 and the like. These heat dissipation boards had to use expensive heat sink plates. Japanese Patent Application Laid-Open No. H11-330311 discloses a method of mounting a power module on a single insulated circuit board composed of a laminate of a circuit board, a ceramics plate, and a heat sink without using such a heat sink plate. Silicon nitride is applied to the ceramic plate of this publication, and an insulated circuit board is fixed to a device casing with screws. Although it has a simple mounting structure, the radiator plate does not have a fin function, and has insufficient heat radiation characteristics.
[0003]
Japanese Patent Application Laid-Open No. 2001-135557 discloses an insulated circuit board in which a laminate of a circuit board, a ceramics plate, and a heat sink is joined with a silver brazing material. In the case of this example, it is described that when the heat radiating plate is a normal copper plate, cracks occur in the ceramics plate in a temperature cycle. In addition, the radiator plate did not have a fin function, and there was a problem in the heat radiation characteristics.
[0004]
Further, Japanese Patent Application Laid-Open No. 2000-183260 discloses an insulated circuit board composed of a laminate of a circuit board, a ceramic plate, and a heat sink. The radiator plate of this publication does not have a fin function, and the insulating circuit board is mounted on a water-cooled heat sink with screws. On the other hand, Japanese Patent Application Laid-Open No. 2001-168256 discloses an insulated circuit board in which a laminate of a circuit board, a ceramics board, and a heat sink is joined with an A1-Si brazing material. Although the radiator plate of this publication has fins made of aluminum alloy, the plane size of the ceramic plate is the largest, and when cracks occur in the ceramic plate, refrigerant such as water leaks to the outside, which is not convenient. There were drawbacks.
[0005]
Japanese Patent Application Laid-Open No. 8-335652 discloses an insulated circuit board comprising a laminate of a circuit board, a ceramics board, a heat sink, a plastic porous metal layer, and a finned heat sink processed by extrusion of copper. In this publication, the structure is complicated, and the plastic porous metal layer is thick, for example, 0.3 mm to 1.0 mm. The porous portion is filled with silicone grease and used, and the thermal resistance of this portion is large. It is difficult to obtain sufficient heat radiation characteristics.
[0006]
[Problems to be solved by the invention]
The insulated circuit board for heat dissipation having a laminated structure of a circuit board, a ceramics board, and a heat sink used in a power module has the following problems.
(A) The radiator plate had no fin function and did not have sufficient heat radiation characteristics. Therefore, a heat sink member is required separately, and the mounting structure of the cooling system is complicated.
(B) To realize a finned insulated circuit board, it was necessary to prevent the ceramic plate from being broken.
(C) The fin could not be processed at low cost by pressing or grinding.
(D) When the ceramics plate was broken, the cooling water leaked to the outside, so that the usability was poor.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide an insulated circuit board having a structure that can be cooled by a liquid refrigerant and capable of being joined by friction stir welding and having good heat radiation characteristics and high reliability, a cooling structure thereof, and a power semiconductor device and a cooling structure thereof. Is to do.
[0008]
[Means for Solving the Problems]
The present invention is a metal, preferably a circuit board made of copper or copper alloy, a ceramic substrate and a metal, preferably an insulated circuit board in which a heat sink made of copper or copper alloy is sequentially joined by brazing material, wherein the heat sink is the It has a plurality of flat fins or rod fins except for the entire outer peripheral portion.
[0009]
Further, in the insulated circuit board according to the present invention, the radiator plate has a plurality of flat fins or rod fins except for the entire outer peripheral portion thereof. It is characterized in that the thick portion is formed integrally, or a thick portion thicker than the diameter of the fin is formed integrally on both outer sides of one of the row of the bar-shaped fins.
[0010]
According to the present invention, a metal, preferably a circuit board made of copper or a copper alloy, a ceramic substrate, and a heat sink made of a metal, preferably copper or a copper alloy are sequentially joined with a brazing material, and the heat sink is cooled in contact with a liquid refrigerant. In the cooling structure of the insulated circuit board, the radiator plate has a plurality of flat fins except for the entire outer peripheral portion thereof, and a member that forms the passage of the refrigerant is joined to the entire outer peripheral portion of the radiator plate. It is characterized by the following.
[0011]
Further, in the cooling structure of the insulated circuit board according to the present invention, the heat radiating plate has a plurality of flat fins except for the entire outer peripheral portion thereof, and has a thicker wall thickness than the fins on both outer sides of the row of the flat fins. The member is integrally formed, and a member that forms the passage for the refrigerant is joined to the entire outer peripheral portion of the heat sink.
[0012]
Further, in the cooling structure of the insulated circuit board according to the present invention, the heat sink has bar-shaped fins except for the entire outer peripheral portion thereof, and a member forming the passage of the refrigerant is joined to the entire outer peripheral portion of the heat sink. It is characterized by the following.
[0013]
It is preferable that the joining is performed by friction stir welding by plastic flow due to insertion of a rotating tool into the joining portion. Further, the circuit board and the heat sink may be made of aluminum or aluminum alloy.
[0014]
According to the present invention, in a power semiconductor device in which a conductor power element is mounted on a circuit board of an insulated circuit board, the insulated circuit board is made of the above-described insulated circuit board.
[0015]
According to the present invention, the following effects are expected.
(A) Sufficient heat radiation characteristics can be obtained with a simple structure capable of providing friction stir welding by providing fins on the heat radiation plate.
(B) Even if a finned heat sink made of copper or a copper alloy having a relatively large thickness is joined to the ceramic substrate, the ceramic plate can be prevented from being broken by taking the following measures. In other words, by using a ceramic substrate with high thermal conductivity and high strength as the ceramic plate, the active metal brazing material immediately below the end of the ceramic substrate is made to protrude from the joint between the ceramic substrate and the heat sink, so that the end of the ceramic substrate is Reduce the maximum residual stress generated. Further, by reducing the thickness of the heat radiating plate immediately below the end of the ceramic substrate, the maximum residual stress generated at the end of the ceramic substrate is reduced. As the ceramic substrate, silicon nitride, aluminum nitride, alumina or the like is preferable.
(C) At the time of etching the circuit board, by processing the fins of the heat sink by etching, the processing cost of the fins can be reduced.
(D) By making the plane size of the heat radiating plate larger than that of the silicon nitride substrate, even if the silicon nitride substrate is broken, the cooling water can be prevented from flowing out, so that the usability can be improved.
(E) As a brazing material for joining the circuit board and the ceramic substrate, or the ceramic substrate and the heat sink, an active metal brazing material of an Ag-Cu-Ti alloy is preferable.
[0016]
The present invention provides a power semiconductor device in which a semiconductor power element is mounted on a circuit board of an insulated circuit board, wherein the insulated circuit board comprises the above-described insulated circuit board, and wherein the semiconductor power element is a circuit of an insulated circuit board. In the cooling structure of a power semiconductor device mounted on a board and having the insulating circuit board having a cooling structure, it is preferable that the cooling structure of the insulating circuit board be the cooling structure of the insulating circuit board described above. With these structures, a more reliable power semiconductor device can be realized.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
FIG. 1 is a sectional view showing one embodiment of an insulated circuit board with fins according to the present invention. As shown in the figure, the finned insulating circuit board has a structure in which a circuit board 1, a silicon nitride substrate 2, and a heat sink 3 having fins 4 are laminated. The structure shown in this figure is a structure in which the fins 4 described later are water-cooled. For this reason, both outer sides of the rows of the fins 4 are formed as thick portions 9 having a thickness larger than the width of the fins 4. The joining can be performed by friction stir welding in which a rotary tool is inserted into the joining portion as described above. A plate-like member having a structure capable of flowing in and out of the refrigerant is similarly joined to both sides in the length direction of the fin 4.
[0018]
These laminates are joined using the active metal brazing materials 5 and 6. When the active metal brazing material is an Ag-Cu-Ti alloy, the laminate is firmly joined at a temperature of about 850 ° C under a high vacuum or an inert atmosphere. The circuit board 1 and the heat sink 3 are made of copper or a copper alloy having high thermal conductivity and low electric resistance. For the silicon nitride substrate 2, a material having a thermal conductivity of about 80 W / m · K and a bending strength of about 700 MPa was used.
[0019]
Next, the approximate thickness and dimensions of each material will be described. The thickness of the circuit board 1 is about 0.3 to 1.0 mm, the thickness of the silicon nitride substrate 2 is about 0.3 to 0.8 mm, the thickness of the active metal brazing materials 5 and 6 is about 0.02 mm, and heat radiation. The thickness t of the flat part of the plate 3 is about 0.6 to 1.5 mm, and the thickness T of the entire part of the heat sink 3 is about 1.0 to 4.0 mm. The width w of the fin 4 is about 0.5 to 2.0 mm, the height h of the fin 4 is about 0.4 to 2.5 mm, and the width d of the groove 7 between the fins 4 is about 0.5 to 2.. 0 mm. If the width of the outermost high-thickness portion 9 of the heat sink 3 is L2 and the width of the outermost groove 8 is L1, these dimensions are approximately 1.0 to 3.0 mm.
[0020]
The following effects can be obtained by using an insulated circuit board having such a structure.
(A) By providing fins on a heat radiating plate made of copper or a copper alloy, high heat radiating characteristics can be obtained with a simple structure.
(B) Even when a bonded body of the finned heat radiating plate 3 made of copper or copper alloy having a relatively large thickness and the silicon nitride substrate 2 is used under a severe heat cycle, the silicon nitride substrate 2 itself is prevented from being broken. be able to. That is, the high-strength silicon nitride substrate 2 was used for the ceramic plate, and the active metal brazing material 6 immediately below the end 2X of the silicon nitride substrate 2 was connected to the silicon nitride substrate 2 and the heat radiating plate as shown by 6a in the figure. This is an effect of reducing the maximum residual stress generated at the end of the silicon nitride substrate 2 by the structure protruding from the bonding portion 3. Further, by disposing the portion immediately below the end 2X of the silicon nitride substrate 2 on the outermost groove 8 of the heat sink 3, that is, the thickness of the heat sink 3 directly below the end 2X of the silicon nitride substrate 2 is reduced. This has the effect of reducing the maximum residual stress generated at the end of the silicon nitride substrate 2.
[0021]
In order to prevent the silicon nitride substrate 2 from being broken on the circuit board 1 side, the active metal brazing material 5 immediately below the end 1X of the circuit board 1 is connected to the circuit board 1 as shown by 5a in FIG. The structure protruding from the junction of the silicon substrate 2 was effective.
(C) As described later, when the circuit board 1 is etched, the heat sink 3 and the fins 4 can be simultaneously etched and the fin processing cost can be reduced.
(D) As shown in the figure, by setting the plane size of the heat radiating plate 3 larger than that of the silicon nitride substrate 2, even if the silicon nitride substrate 2 is broken, the presence of the heat radiating plate 3 causes the cooling water on the fin 4 side. External leakage (outflow to the circuit board 1 side) can be prevented, and usability has been improved.
[0022]
FIG. 2 is a plan view of the finned heat sink 3 of the previous figure. This figure is a plan view of the heat sink 3 as viewed from the fin 4 side. In the figure, 100 parts indicated by dotted lines indicate end positions 2X of the silicon nitride substrate 2. As described above, the position of the joint end portion of the silicon nitride substrate 2 was at the low thickness portion (dimension t) of the heat sink 3, which was effective in preventing the silicon nitride substrate 2 from being broken as described above. The flow of the cooling water flowing through the groove 7 between the fins 4 is indicated by an arrow in the figure. The previous figure is a sectional view of the insulated circuit board at the position AA in the figure.
[0023]
(Example 2)
FIG. 3 is a sectional view showing an embodiment applied to a cooling structure of a power semiconductor device in which a semiconductor power element is mounted on the finned insulated circuit board according to the present invention of FIGS. 1 and 2. After bonding the semiconductor power element 10 to the circuit board 1 with the solder 11, the heat sink 3 having the fins 4 is fixed to the member 12. When the member 12 is made of aluminum or an aluminum alloy, the heat sink 3 is airtightly joined to the member 12 by friction stir welding by plastic flow by inserting a rotating tool into a butt portion of the heat sink 3 with the member 12 at the thick portion 9. be able to. For joining by the friction stir welding, thick portions 9 are formed at both ends of the radiator plate 3 where the fins 4 are arranged.
[0024]
The member 12 has a cap structure in which the portions other than the portions corresponding to the upper and lower portions in FIG. 2 are flat, and the portions corresponding to the upper and lower portions have side plate portions whose height is slightly longer than the height of the fins. The side plate is provided with a supply port for supplying cooling water and a discharge port on the opposite side. The two are joined on the left and right sides of the thick portion 9 in a direction perpendicular to the plane of the paper, and the fins 4 are formed on the upper and lower portions of the heat sink 3 as shown in FIG. Are joined by friction stir welding by insertion of the above-mentioned rotating tool from the outside at a butt portion where no space is formed. The joint of the side plate has a structure that is partially supported by the fins 4 and is not deformed at the time of joining. Therefore, the joint is thicker than the thin non-joined part and generally thinner than the thick part 9. It has a structure. The same applies to the following embodiments.
[0025]
By flowing the cooling water into the grooves 7 between the fins 4, the semiconductor power element 10 can be efficiently cooled with a simple mounting structure. The distance between the member 12 and the fin 4 is reduced so as to reduce deformation of the flat plate due to friction stir welding. Finally, it is needless to say that a solution to at least one of the problems (a) to (d) of the above-described prior art is included in the present invention.
[0026]
(Example 3)
FIG. 4 is a sectional view showing another embodiment of the finned insulated circuit board according to the present invention. This drawing is an embodiment in the case where the thickness T of the entire heat sink 3 is as thin as about 1.5 mm or less. In this case, even if the end position 2X of the silicon nitride substrate 2 is located at the high thickness portion 9 of the heat sink 3, the silicon nitride substrate 2 could be prevented from being broken. This is because the residual stress generated in the silicon nitride substrate 2 largely depends on the thickness of the heat sink 3. Also in this embodiment, as in the first embodiment, joining can be performed by friction stir welding in which a rotary tool is inserted into the joint. A plate-like member having a structure capable of flowing in and out of the refrigerant is similarly joined to both sides in the length direction of the fin 4.
[0027]
FIG. 5 shows a plan view of the finned heat sink 3 of the preceding figure. This figure is a plan view of the heat sink 3 as viewed from the fin 4 side. In the figure, 100 parts indicated by dotted lines indicate end positions 2X of the silicon nitride substrate 2. When the thickness of the heat sink 3 is relatively thin, even if the bonding end position 100 part of the silicon nitride substrate 2 is arranged above the outermost high-thickness part 9 or the fin 4 part of the heat sink 3, The destruction of the silicon nitride substrate 2 could be prevented.
[0028]
Also in the present embodiment, a cooling structure of a power semiconductor device on which a semiconductor power element is mounted can be formed as in the second embodiment. The fins 4 of this embodiment are formed over both ends of the radiator plate 3, and the members 12 are formed at both ends of the arrangement of the fins 4 shown in FIG. A slightly thicker flat plate is used, and a flat plate is used on the side surface, and similarly joined by the above-mentioned friction stir welding.
[0029]
(Example 4)
FIG. 6 is a sectional view showing another embodiment of the finned insulated circuit board according to the present invention. This drawing is an embodiment in which the thickness of the heat radiating plate 3 other than the fin 4 is uniform and the thickness t of the flat portion of the heat radiating plate 3 is as thin as about 1.5 mm or less. Also in the case of this figure, the destruction of the silicon nitride substrate 2 could be prevented.
[0030]
FIG. 7 shows a plan view of the finned heat sink 3 of the previous figure. This figure is a plan view of the heat sink 3 as viewed from the fin 4 side. In the figure, 100 parts indicated by dotted lines indicate end positions 2X of the silicon nitride substrate 2. As shown in the figure, the junction end position 100 of the silicon nitride substrate 2 is disposed above the low thickness portion of the heat sink 3.
[0031]
Also in the present embodiment, a cooling structure of a power semiconductor device having a semiconductor power element mounted thereon can be formed as in the second embodiment. As shown in FIG. 7, no fins are formed on the entire outer peripheral portion, and the cap-shaped member 12 is joined to the entire end portion of the heat sink 3 by friction stir welding in the same manner as in the second embodiment.
[0032]
(Example 5)
FIG. 8 is a sectional view showing another embodiment of the finned insulated circuit board according to the present invention. This figure is a plan view of the heat sink seen from the fin 4 side. The fins 4 and 4a are formed, and the fins 4 have the same height as the outermost part 9 of the heat sink. On the other hand, the thickness of the fin 4a is smaller than the thickness of the fin 4 part, and is lower than the outermost part 9 of the heat sink. 2X is indicated. As shown in the figure, in this embodiment, a junction end portion 100 of the silicon nitride substrate 2 is disposed above the low-thickness portion and the low-thickness fin 4a of the heat sink 3.
[0033]
Also in the present embodiment, a cooling structure of a power semiconductor device having a semiconductor power element mounted thereon can be formed as in the second embodiment. The plane parallel to the paper is formed by a flat plate having a shape corresponding to the shape.
[0034]
(Example 6)
FIG. 9 is a cross-sectional view showing another embodiment of the finned insulated circuit board according to the present invention. This figure is a plan view of the heat radiating plate 3 as viewed from the fin 4b side, and differs from FIG. 2 in the shape of the fin. That is, while the fin shape is rectangular in FIG. 2, the fin 4b in this figure is a round pin shape, and the fins 4, 4a, 4b, etc., which are arranged like a sword mountain, are Since the fins are processed at the same time when they are processed by etching, they can be easily manufactured even if the fin shape changes.
[0035]
Also in the present embodiment, a cooling structure of a power semiconductor device having a semiconductor power element mounted thereon can be formed as in the second embodiment. A plane parallel to the paper is the same as in the second embodiment.
[0036]
(Example 7)
FIG. 10 is a plan view showing another embodiment of the finned insulated circuit board according to the present invention. This figure is a plan view of the heat sink 3 viewed from the fin 4 side, and differs from FIG. 2 in the following point. That is, the outermost high-thickness portion 9 of the heat sink 3 surrounds the fin 4. In this embodiment, the cooling water flows from the portion (1) in a direction perpendicular to the paper surface, flows in the direction of the arrow, and flows out of the portion (2) in a direction perpendicular to the paper surface. Note that the position of the joint end of the silicon nitride substrate 2 is shown as 100 parts in the figure.
[0037]
Also in this embodiment, a cooling structure of a power semiconductor device having a semiconductor power element mounted thereon can be formed in the same manner as in the second embodiment. .
[0038]
(Example 8)
FIG. 11 is a plan view showing another embodiment of the finned insulated circuit board according to the present invention. This figure is a plan view of the heat sink 3 viewed from the fin 4b side, and differs from FIG. 10 in the following point. That is, while the fin shape is rectangular in FIG. 10, the fin 4b in this figure has a round pin shape, and is an embodiment arranged like a sword mountain.
[0039]
Also in this embodiment, a cooling structure of a power semiconductor device having a semiconductor power element mounted thereon can be formed in the same manner as in the second embodiment. .
[0040]
(Example 9)
FIG. 12 is a cross-sectional view showing a method for etching a finned insulated circuit board according to the present invention. After the laminate of the circuit board 1, the silicon nitride substrate 2, and the heat sink 3 is joined using the active metal brazing materials 5, 6, the laminate is covered with a photosensitive resist or a film 200. This figure shows a state where unnecessary portions of the photosensitive resist and the film 200 are removed by photoetching. By spraying a ferric chloride solution on the laminate in this state, the circuit board 1 made of copper or a copper alloy and the heat radiating plate 3 can be etched. In this way, the heat sink 3 having the fins 4 as shown in FIG. 1 can be easily formed at the time of etching the circuit board 1. Similarly, the structure shown in FIGS. 4 to 11 can be formed by photoetching.
[0041]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the structure which can be cooled by a liquid refrigerant is made into the structure which can be joined by friction stir welding, The heat dissipation characteristic is good, and the insulating circuit board which has high reliability, its cooling structure, the power semiconductor device, and its cooling structure are provided. can do.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a finned insulated circuit board according to the present invention.
FIG. 2 is a plan view of the insulated circuit board with fins shown in FIG. 1 as viewed from the fin side.
FIG. 3 is a cross-sectional view of a cooling device for a power semiconductor device in which a semiconductor power element is mounted on a finned insulated circuit board according to the present invention.
FIG. 4 is a cross-sectional view showing another example of the finned insulated circuit board according to the present invention.
FIG. 5 is a plan view of the insulated circuit board with fins shown in the preceding figure as viewed from the fin side.
FIG. 6 is a sectional view showing another example of the finned insulated circuit board according to the present invention.
7 is a plan view of the insulated circuit board with fins shown in FIG. 6 as viewed from the fin side.
FIG. 8 is a plan view showing another example of the finned insulated circuit board according to the present invention.
FIG. 9 is a plan view showing another example of the finned insulated circuit board according to the present invention.
FIG. 10 is a plan view showing another example of the finned insulated circuit board according to the present invention.
FIG. 11 is a plan view showing another example of the insulated circuit board with fins according to the present invention.
FIG. 12 is a cross-sectional view of manufacturing the finned insulated circuit board according to the present invention by an etching method.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Circuit board, 2 ... Silicon nitride board, 3 ... Heat sink, 4, 4a, 4b ... Fin, 5, 6 ... Active metal brazing material, 5a, 6a ... Projection part of active metal brazing material, 7 ... Groove, 8 ... outermost groove, 9 ... thick part, 10 ... semiconductor power element, 11 ... solder, 12 ... member, 1X ... end of circuit board, 2X ... end of silicon nitride substrate, 100 ... joining of silicon nitride substrate End position, 200: photosensitive resist or film.

Claims (13)

In an insulated circuit board in which a circuit board made of metal, a ceramic substrate, and a heat sink made of metal are sequentially joined with a brazing material, the heat sink has a plurality of flat fins or rod fins except for the entire outer peripheral portion thereof. And an insulated circuit board. In an insulated circuit board in which a circuit board made of metal, a ceramic substrate, and a heat sink made of metal are sequentially joined with a brazing material, the heat sink has a plurality of flat fins except for the entire outer peripheral portion thereof. Characterized in that thick portions thicker than the width of the fins are integrally formed at both ends arranged on the forming side. In an insulated circuit board in which a circuit board made of metal, a ceramic substrate, and a heat sink made of metal are sequentially joined by a brazing material, the heat sink has a plurality of rod-shaped fins except for the entire outer peripheral portion thereof, and the rod-shaped fins are formed. Characterized in that a thick portion thicker than the diameter of the fin is integrally formed at one end of the side. 4. The insulated circuit board according to claim 1, wherein the circuit board is formed by etching, and the fins are formed by etching simultaneously with the etching. 5. The insulated circuit board according to claim 1, wherein a width between the fins is smaller than a width immediately below an end of the ceramic substrate. The insulated circuit board according to any one of claims 1 to 5, wherein a height of the fin is equal to or less than that of the outer peripheral portion. 7. The brazing material according to claim 1, wherein the brazing material between the circuit board and the ceramic substrate and the brazing material between the ceramic substrate and the heat sink are active metal brazing materials, and the brazing material is the circuit material. An insulated circuit board having a structure protruding outward from at least one of an end of a plate and an end of the ceramic substrate. In a cooling structure of an insulated circuit board in which a circuit board made of metal, a ceramics substrate, and a heat sink made of metal are sequentially joined by a brazing material, and the heat sink is cooled in contact with a liquid refrigerant, the heat sink has an outer peripheral portion. A cooling structure for an insulated circuit board, comprising: a plurality of flat fins except for the above, wherein a member forming the passage of the refrigerant is joined to the entire outer peripheral portion of the heat sink. In a cooling structure of an insulated circuit board in which a circuit board made of metal, a ceramics substrate, and a heat sink made of metal are sequentially joined by a brazing material, and the heat sink is cooled in contact with a liquid refrigerant, the heat sink has an outer peripheral portion. Except for a plurality of flat fins, thick portions thicker than the width of the fins are integrally formed at both ends of the row of the flat fins, A cooling structure for an insulated circuit board, wherein a member forming a passage is joined. In a cooling structure of an insulated circuit board in which a circuit board made of metal, a ceramics substrate, and a heat sink made of metal are sequentially joined by a brazing material, and the heat sink is cooled in contact with a liquid refrigerant, the heat sink has an outer peripheral portion. A cooling structure for an insulated circuit board, comprising: a bar-shaped fin except for the above, and a member that forms the passage for the refrigerant joined to the entire outer peripheral portion of the heat sink. The cooling structure for an insulated circuit board according to any one of claims 8 to 10, wherein the joining is performed by friction stir welding by inserting a rotary tool into the joining portion. A power semiconductor device in which a semiconductor power element is mounted on a circuit board of an insulated circuit board, wherein the insulated circuit board comprises the insulated circuit board according to any one of claims 1 to 7. The cooling structure for a power semiconductor device, wherein the semiconductor power element is mounted on a circuit board of an insulated circuit board and the insulated circuit board has a cooling structure, wherein the cooling structure for the insulated circuit board is according to any one of claims 8 to 11. A cooling structure for a power semiconductor device, comprising a cooling structure for an insulated circuit board.

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