JP7230602B2 - Insulated circuit board and its manufacturing method - Google Patents

Description

The present invention relates to an insulated circuit board such as a power module board and a method for manufacturing the same.

As an insulating circuit board, a power module board is known in which a circuit layer is bonded to one surface of an insulating substrate made of a ceramic substrate such as aluminum nitride, and a metal layer is bonded to the other surface. Such a power module substrate generally uses aluminum or copper for the circuit layer and the metal layer.

For example, Patent Literature 1 and Patent Literature 2 disclose an insulated circuit board in which a copper plate is bonded to one surface of a ceramic substrate and an aluminum plate is bonded to the other surface. In this case, the ceramic substrate and the copper plate are joined by a brazing filler metal using an Ag--Cu--Ti based active metal, and the ceramic substrate and the aluminum plate are joined by an Al--Si based brazing filler metal.
This power module substrate is manufactured as follows. First, on one side of a ceramic substrate, a copper plate is laminated via an active metal brazing material such as Ag--Cu--Ti as a brazing material suitable for joining ceramics and a copper plate, and the brazing material is pressed under a predetermined pressure. is heated to a temperature higher than the melting temperature, thereby joining the ceramic substrate and the copper plate. Next, on the other surface of the ceramic substrate, an aluminum plate is laminated via an Al—Si brazing filler metal suitable for bonding between the ceramic and the aluminum plate, and while applying pressure at a predetermined pressure, the temperature exceeds the melting temperature of the brazing filler metal. to join the ceramic substrate and the aluminum plate.
In such an insulated circuit board, a semiconductor element is mounted on a copper plate (copper layer) via a solder material.

JP 2003-197826 A JP 2013-229579 A

In such an insulated circuit board, a phenomenon occurs in which the molten solder used for joining the copper plate and the ceramic substrate seeps out to the surface of the copper plate and creeps up along the side surface of the copper plate. Molten solder that has crawled up to the surface becomes a so-called solder stain, which not only impairs the appearance, but also leads to deterioration in the wettability of the solder material used when joining semiconductor elements. Similarly, when an aluminum plate is used for the circuit layer, there is a problem of solder stains due to the molten solder creeping up. Attempts to suppress the occurrence of this wax stain may impair the bondability.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances. It aims at providing a circuit board and its manufacturing method.

An insulating circuit board of the present invention is an insulating circuit board in which a circuit layer is formed on one surface of a ceramic substrate, and a semiconductor element is mounted on the surface of the circuit layer opposite to the ceramic substrate. A rib is formed surrounding the mounting surface, the height of the rib is 10 μm or more and 30 μm or less, the width of the rib is 100 μm or more, and the value obtained by multiplying the height of the rib by the width of the rib is 2000 μm. ² or more.

In the present invention, since the ribs are formed so as to surround the mounting surface of the circuit layer on which the semiconductor element is to be mounted, in the manufacturing stage (bonding process) of the insulated circuit board, when the circuit layer is pressed by the pressure plate, Since the ribs are pressed against each other, the ribs can prevent the molten solder from entering between the ribs and the pressure plate even if the molten solder moves along the end surface of the circuit layer toward the surface side. Therefore, it is possible to suppress the occurrence of brazing stains and improve the solder bondability of the semiconductor element without impairing the bondability between the metal plate and the ceramic substrate.

If the height of the rib is less than 10 μm, the pressure plate bends and comes into contact with the mounting surface during the bonding process of the insulated circuit board, making it difficult to press the rib with a high pressure. On the other hand, if the height of the rib exceeds 30 μm, the pressure plate similarly bends in the bonding process, making it difficult to press the rib periphery with a high pressure. If the width of the rib is less than 100 μm, the pressure plate will bend in the bonding process, making it difficult for a load to be applied to the surface to be mounted, resulting in poor bondability.

Furthermore, the value obtained by multiplying the rib height by the rib width (the cross-sectional area of the surface formed by the rib height and the rib width) is set to a value of 2000 μm ² or more. Since the value obtained by multiplying the rib height by the rib width is 2000 μm ² or more, the components of the brazing filler metal do not diffuse into the ribs and reach the mounting surface, and when wire bonding or the like is performed, In addition, it is possible to suppress the decrease in adhesion.

As a preferred aspect of the insulated circuit board of the present invention, the rib may be formed along the edge of the circuit layer.
In the above aspect, since the ribs are formed along the edge of the circuit layer, the surface of the circuit layer on which the semiconductor is to be mounted can be made large.

As a preferred embodiment of the insulated circuit board of the present invention, the circuit layer may be made of aluminum, an aluminum alloy, copper, or a copper alloy.

In the method of manufacturing an insulated circuit board according to the present invention, a circuit layer metal plate having ribs surrounding a mounting surface on which a semiconductor element is to be mounted is arranged on one surface of a ceramic substrate via a brazing material and laminated. a laminate forming step of forming a body; and a joining step of joining the circuit layer metal plate to one surface of the ceramic substrate by applying pressure and heat to the laminate in the stacking direction to form a circuit layer. and wherein the rib height is 10 μm or more and 30 μm or less, the rib width is 100 μm or more, and the value obtained by multiplying the rib height by the rib width is 2000 μm or more ^, In the joining step, a pressing plate is brought into contact with the rib to press the laminate.

In the present invention, when pressurizing and heating the laminate of the circuit layer metal plate, the brazing material and the ceramic substrate, the pressure plate is brought into contact with the ribs of the circuit layer metal plate formed with ribs surrounding the mounting surface. Therefore, even if the molten solder runs along the end surface of the circuit layer metal plate, the pressurizing plate and the ribs can prevent the molten solder from spreading on the surface, thereby suppressing solder stains.

ADVANTAGE OF THE INVENTION According to this invention, the solder|soldering bondability of a semiconductor element can be improved by suppressing the generation|occurrence|production of a brazing stain, without impairing the bondability of a metal plate and a ceramic substrate.

1 is a cross-sectional view showing a cross section of an insulated circuit board according to an embodiment of the present invention; FIG. It is the figure which looked at the insulation circuit board shown in FIG. 1 from the circuit layer side. 2 is a cross-sectional view showing an enlarged end portion of a circuit layer of the insulated circuit board of FIG. 1; FIG. 1. It is a figure which shows a part of manufacturing method of the insulated circuit board shown in FIG. 1. It is a figure which shows another part of the manufacturing method of the insulated circuit board shown in FIG. It is the figure which looked at the insulation circuit board in the 1st modification of the said embodiment from the circuit layer side. It is the figure which looked at the insulation circuit board in the 2nd modification of the said embodiment from the circuit layer side.

An embodiment of the present invention will be described below with reference to the drawings.

[Schematic configuration of insulating circuit board]
1 is a cross-sectional view of the insulating circuit board 1 of the present embodiment, FIG. 2 is a plan view of the insulating circuit board 1 viewed from the circuit layer 3 side, and FIG. 3 is a cross-sectional view showing an enlarged end of 3. FIG.

As shown in FIG. 2, the insulating circuit board 1 is formed in a rectangular shape with a vertical dimension of 10 mm or more and 100 mm or less and a horizontal dimension of 10 mm or more and 100 mm or less in plan view. As shown in FIG. 1, such an insulating circuit board 1 comprises a rectangular ceramic substrate 2, a circuit layer 3 formed on one surface 21a of the ceramic substrate 2, and the other surface 21b of the ceramic substrate 2. and a metal layer 4 formed on the These circuit layer 3 and metal layer 4 are formed in a rectangular plate shape slightly smaller than the ceramic substrate 2 .

[Structure of ceramic substrate]
The ceramic substrate 2 is made of a ceramic material such as aluminum nitride (AlN), silicon nitride (Si ₃ N ₄ ), alumina (Al ₂ O ₃ ), etc., and has a thickness of 0.3 mm to 1.0 mm. . Also, the ceramic substrate 2 is formed in a rectangular plate shape in a plan view, and is slightly larger than each of the circuit layer 3 and the metal layer 4 .

[Configuration of circuit layer]
The circuit layer 3 is formed by brazing a metal plate made of pure aluminum with a purity of 99.00% or more, an aluminum alloy, pure copper such as oxygen-free copper or tough pitch copper, or a copper alloy to the ceramic substrate 2 . For example, in this embodiment, the circuit layer 3 is made of oxygen-free copper.
On the surface 31a of the circuit layer 3 opposite to the ceramic substrate 2, as shown in FIG. 2, a rectangular frame-shaped rib 32 is formed surrounding a mounting surface Ar1 on which a semiconductor element (not shown) is mounted. ing. The planned mounting surface Ar1 is arranged substantially at the center of the circuit layer 3, and its shape can be freely set according to the type of semiconductor to be mounted on the insulating circuit board 1 and the like. Further, the rib 32 is formed along the edge of the circuit layer 3 and is formed with a gap from the mounting surface Ar1.

As shown in FIG. 3, the height h1 of the rib 32 is set to 10 μm or more and 30 μm or less. Also, the width w1 of the rib 32 is set to 100 μm or more.
When the height h1 of the ribs 32 is less than 10 μm, the pressure plate 61 (see FIGS. 4C and 5) bends in the process of bonding the insulated circuit board 1 and comes into contact with the planned mounting surface Ar1. If the height h1 of the rib 32 exceeds 30 μm, the pressure plate 61 is bent in the bonding process, making it difficult to press the periphery of the rib 32 with a high pressure. Further, when the width of the rib 32 is less than 100 μm, the pressure plate 61 is bent in the bonding process, and a load is less likely to be applied to the mounting surface Ar1, thereby deteriorating bondability.
Although the upper limit of the width of the rib 32 is not particularly limited, it is preferably 300 μm or less. If the width of the rib 32 exceeds 300 μm, the area of the planned mounting surface Ar1 becomes small, and the insulating circuit board 1 itself needs to be enlarged, which may increase the manufacturing cost of the insulating circuit board 1 .

In addition, in order to prevent the inside of the rib 32 from diffusing and reaching the mounting surface Ar1, the height h1 and the width w1 of the rib 32 are set within the ranges described above, and the height h1 of the rib 32 and the width w1 of the rib 32 By setting the value (cross-sectional area of the surface formed by the height h1 of the rib 32 and the width of the rib 32) multiplied by the width w1 of the molten solder to a value of 2000 μm ² or more, the molten solder in the circuit layer 3 suppressing the spread of
In addition, as shown in FIG. 3, the solidified residual solder 51 is located on the end surface 31c of the circuit layer 3. As shown in FIG.

[Structure of metal layer]
The metal layer 4 is formed by brazing a metal plate made of pure aluminum with a purity of 99.00% or more, an aluminum alloy, pure copper such as oxygen-free copper or tough pitch copper, or a copper alloy to the ceramic substrate 2 . In this embodiment, the metal layer 4, like the circuit layer 3, is made of oxygen-free copper.
A rib 42 having the same shape as the rib 32 is formed on the surface 41a of the circuit layer 3 opposite to the ceramic substrate 2, as shown in FIG.

[Manufacturing method of insulated circuit board]
Next, a method for manufacturing the insulating circuit board 1 configured as described above will be described. This manufacturing method comprises a metal plate forming step of forming the circuit layer metal plate 30 and the metal layer metal plate 40 , and the circuit layer metal plate 30 , the ceramic substrate 2 and the metal layer metal plate 40 through the brazing material 50 . and a laminate forming step of forming a laminate 100 by laminating the laminate 100, and pressing and heating the laminate 100 in the lamination direction to join the circuit layer metal plate 30 and the metal layer metal plate 40 to the ceramic substrate 2. and a bonding step of forming the circuit layer 3 and the metal layer 4 by using the bonding process.
Each step will be described below in the order of steps.

(Metal plate forming step)
Each of the circuit layer metal plate 30 and the metal layer metal plate 40 is made of oxygen-free copper, and has the above-described ribs 32 and ribs 42 formed thereon. Each of the circuit layer metal plate 30 and the metal layer metal plate 40 is prepared by preparing a coil-shaped metal base plate having a size capable of forming the metal plates 30 and 40, and letting out the metal base plate from the coil. It is sent to a press (not shown) while being intermittently conveyed. In this press machine, in order to form the metal plate into the outer shape of each of the metal plates 30 and 40, the metal plate is fed between the die and the punch, and the punch is lowered to punch out the metal plate into a rectangular shape. A plate-like metal plate is formed. After that, in order to form the ribs 32 and 42 on one surface of the metal plate, the central portion of the metal plate (the portion including the planned mounting area Ar1) is etched. As a result, the circuit layer metal plate 30 and the metal layer metal plate 40 having the ribs 32 and 42 are formed.

In the metal plate forming step, the ribs 32 and 42 are formed by etching the central portion of the rectangular metal plate, but the present invention is not limited to this, and the ribs 32 and 42 are formed by polishing or the like, for example. You may At this time, the peripheral edge of one surface (the surface pressed by the punch) of the metal plate punched by the punch becomes a drooped surface, and burrs are generated on the peripheral edge of the other surface. By doing so, the ribs 32 and 42 may be formed. That is, any method may be used to manufacture the circuit layer metal plate 30 and the metal layer metal plate 40 .

(Laminate forming step)
Then, as shown in FIG. 4A, the circuit layer metal plate 30 having the ribs 32 surrounding the mounting surface Ar1 on which the semiconductor element is to be mounted is mounted on one surface of the ceramic substrate 2 with the brazing material 50 interposed therebetween. The ribs 32 are arranged on the surface 21a of the ceramics substrate 2 with the ribs 32 facing away from the ceramics substrate 2, and the metal plate 40 for the metal layer formed with the ribs 42 is attached to the other surface 21b of the ceramics substrate 2 via the brazing material 50. are arranged in a state of facing in the direction opposite to the ceramic substrate 2 . By stacking these, a laminate 100 as shown in FIG. 4B is formed.
The brazing material 50 is formed in a foil shape, and is composed of, for example, Ag--Ti or Ag--Cu--Ti based active metal brazing material.

(Joining process)
Then, as shown in FIG. 4(c), the laminated body 100 formed by the laminated body forming step is sandwiched between pressure plates 61 and 62 of a pressure jig, and a pressure of 0.05 MPa to 1.0 MPa, more preferably 0.05 MPa to 1.0 MPa, is applied in the lamination direction. is pressurized at 0.5 to 0.8 MPa. At this time, the pressure surface of the pressure plate 61 is in contact with the upper surface of the rib 32 of the circuit layer metal plate 30 , and the pressure surface of the pressure plate 62 is in contact with the upper surface of the rib 42 . That is, the pressing plates 61 and 62 press the upper surfaces of the ribs 32 and 42, respectively. Each of the pressing plates 61 and 62 is made of carbon, for example, and a graphite sheet is arranged on the pressing surface thereof.

Then, in a state where the laminated body 100 is pressurized, it is placed in a heating furnace (not shown) together with the pressurizing plates 61 and 62, and heated to a temperature of 800° C. or higher and 930° C. or lower, more preferably 800° C. to 830° C. under a vacuum atmosphere. The ceramic substrate 2 is joined to the circuit layer metal plate 30 and the metal layer metal plate 40 by heating for 1 to 60 minutes at , thereby forming the circuit layer 3 and the metal layer 4 on the ceramic substrate 2 . Here, the ceramic substrate 2 and the circuit layer 3 and the ceramic substrate 2 and the metal layer 4 are joined via brazing material layers (not shown) formed by melting the brazing material 50 .
Here, when the laminate 100 is pressed and heated at the above temperature, as shown in FIG. and the molten solder creeps up the end surface 31c of the circuit layer metal plate 30. Ar1 is never reached. Therefore, when the insulated circuit board 1 is heated and then cooled, the molten solder solidifies in the vicinity of the outer peripheral surface of the rib 32 (the end surface 31c of the circuit layer 3) and becomes the residual solder 51. As shown in FIG.

It should be noted that the molten solder seeps out from between the ceramic substrate 2 and the metal layer metal plate 40, and flows out to the end surface of the metal layer metal plate 40. However, since the ribs 42 are formed, The pressure plate 62 prevents the metal plate 40 from reaching the surface 41 a of the metal layer metal plate 40 .

In this manner, the insulating circuit board 1 having the circuit layer 3 formed on one surface 21a of the ceramic substrate 2 and the metal layer 4 formed on the other surface 21b is obtained. Since solder stains are not generated on the mounting surface Ar1 of the circuit layer 3 of the insulated circuit board 1, the semiconductor element (not shown) is reliably fixed by the solder material, and the board is suitable for use as a power module board or the like. available.

In the insulating circuit board 1 of the present embodiment, the ribs 32 are formed so as to surround the mounting surface Ar1 on which the semiconductor element of the circuit layer 3 is mounted. Since the ribs 32 are pressed when the pressure plate 61 presses the circuit layer 3 (circuit layer metal plate 30), even if the molten solder moves along the end face of the circuit layer 3 to the surface side, the ribs 32 and The ribs 32 can prevent molten solder from entering between the pressure plate 61 and the pressure plate 61 . Therefore, it is possible to suppress the occurrence of wax stains and improve the solder bondability of the semiconductor element without impairing the bondability between the circuit layer metal plate 30 and the ceramic substrate 2 . Further, since the ribs 32 are formed along the edge of the circuit layer 3, the surface Ar1 on which the semiconductor is to be mounted on the circuit layer 3 can be widened.

Furthermore, in the method for manufacturing the insulated circuit board 1 of the present embodiment, when the laminate 100 of the circuit layer metal plate 30, the metal layer metal plate 40, the brazing material 50, and the ceramic substrate 2 is pressed and heated, the mounting Since the pressure plate 61 is brought into contact with the ribs 32 of the circuit layer metal plate 30 formed with the ribs 32 surrounding the planned surface Ar1 and pressurized, even if the molten solder runs along the end face 31c of the circuit layer metal plate 30, the pressure is applied. The pressure plate 61 and the ribs 32 can prevent the molten solder from spreading on its surface, thereby suppressing the occurrence of solder stains.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the present invention.
For example, in the above-described embodiment, the ribs 32 are formed along the edge of the circuit layer 3, but the present invention is not limited to this. FIG. 6 is a view of the insulated circuit board 1 according to the first modification of the above embodiment viewed from the circuit layer 3A side.
In this modification, the rib 32A is formed with a slight gap from the mounting surface Ar1 on the surface 31a of the circuit layer 3A, and the outer peripheral edge of the rib 32A does not coincide with the edge of the circuit layer 3A. That is, the rib 32A is arranged at a position away from the edge of the circuit layer 3A (center side). The rib 32A is formed in a rectangular frame shape surrounding the planned mounting surface Ar1, and its height h1 and width w1 are set within the same range as in the above embodiment. A value obtained by multiplying the height h1 of the rib 32A by the width w1 of the rib 32A is set to a value of 2000 μm ² or more. For this reason, in the manufacturing process (bonding process) of the insulated circuit board 1 in this modification, it is possible to prevent the molten brazing filler metal crawling up the end surface 31c of the circuit layer 3A from entering the mounting surface Ar1. In addition, since the end surface 31c of the circuit layer 3A and the rib 32A are separated from each other, the molten solder accumulates in the area outside the rib 32A on the surface 31a of the circuit layer 3A, and the molten solder enters the mounting surface Ar1. can be reliably suppressed.

Further, in the first modified example, the rib 32A is formed in a rectangular frame shape, but the present invention is not limited to this. FIG. 7 is a view of the insulated circuit board 1 according to the second modification of the above embodiment viewed from the circuit layer 3B side.
In this modification, as in the first modification, the rib 32B is formed with a slight gap from the mounting surface Ar1 on the surface 31a of the circuit layer 3B, and the outer peripheral edge of the rib 32B and the edge of the circuit layer 3B are separated from each other. do not match. The rib 32B is formed in a circular frame shape surrounding the planned mounting surface Ar1, and its height h1 and width w1 are set within the same range as in the above embodiment. A value obtained by multiplying the height h1 of the rib 32B by the width w1 of the rib 32B is set to a value of 2000 μm ² or more. Therefore, in the manufacturing process (bonding process) of the insulated circuit board 1 in this modification, it is possible to prevent the molten brazing filler metal crawling up the end surface 31c of the circuit layer 3B from entering the mounting surface Ar1.

Although the metal layer 4 is provided in the above embodiment, the present invention is not limited to this, and the metal layer 4 may be omitted. Moreover, even when the metal layer 4 is provided, the metal layer 4 does not have to have the ribs 42 .

Although the circuit layer 3 and the metal layer 4 are made of oxygen-free copper in the above embodiment, at least one of them may be made of pure aluminum or an aluminum alloy. In this case, an Al—Si based brazing material may be used as the brazing material 50 .

A silicon nitride plate having a rectangular shape of 30 mm square and a thickness of 0.325 mm was used as the ceramic substrate, and a punched oxygen-free copper plate having a rectangular shape of 27 mm square and a thickness of 0.3 mm was used as the metal plate for the circuit layer. board. A 15 mm square rectangular mounting surface was provided in the center of the oxygen-free copper plate. In Examples 1 to 11 and Comparative Examples 1 to 5, ribs were formed by wet etching with iron chloride on the surface of the oxygen-free copper plate to be mounted. Each rib was formed along the edge of the circuit layer. Table 1 shows the values obtained by multiplying the rib height h1 and the rib width w1 by the rib height h1 and the rib width w1. In Comparative Example 5, ribs were not formed.

After forming a laminate by laminating an oxygen-free copper plate with the planned mounting surface facing away from the ceramic substrate on the ceramic substrate via a foil brazing material made of Ag-8.8% by mass Ti. An insulated circuit board was produced by heating at 830° C. for 60 minutes in a vacuum atmosphere while pressing the laminate at 0.1 MPa in the stacking direction with a carbon pressure plate having a graphite sheet formed on the surface. Then, the presence or absence of wax stains on the surface to be mounted of the manufactured insulated circuit board was evaluated, and the results are shown in Table 1.

[Wax stain]
Regarding the evaluation of wax stains, on the planned mounting surface of the oxygen-free copper plate, it was visually confirmed whether there was a stain with a length of 1 mm or more from the end of the planned mounting surface, and one or more such stains were found. A case was rated as unsatisfactory "B" and otherwise rated as good "A". The results are as shown in Table 1.

[Joinability]
For evaluation of bondability, the voids at the interface between the ceramic substrate and the oxygen-free copper plate are measured with an ultrasonic inspection device, and the void area ratio at the interface is 3% or more when the area of the oxygen-free copper plate is taken as 100%. The case was evaluated as unsatisfactory "B", and the case of less than 3% was evaluated as good "A". The results are as shown in Table 1.

[Ag diffusion]
Regarding the evaluation of Ag diffusion, after bonding the ceramic substrate and the copper plate, the surface of the rib (the surface opposite to the ceramic substrate) was observed with an optical microscope (20x), and the color (discoloration) different from the color of the oxygen-free copper plate was observed. A case in which a crack occurred was evaluated as unsatisfactory "B", and a case in which it did not occur was evaluated as good "A". The results are as shown in Table 1.

As shown in Table 1, the rib height is 10 μm or more and 30 μm or less, the rib width is 100 μm or more, and the value obtained by multiplying the rib height by the rib width is 2000 μm ^or more. With respect to No. 11, no wax stain was observed, and the solder stain was evaluated as good "A", and the bondability and Ag diffusion were also evaluated as good "A".

On the other hand, among Comparative Examples 1 to 3 in which the value obtained by multiplying the rib height by the rib width is less than 2000 μm ² even if the rib height or rib width is within the above range, in Comparative Example 1, The rib width was as small as 50 μm, and the value obtained by multiplying the rib height by the rib width was too small as 1000 μm ² or less. In Comparative Example 2, the rib height was as small as 5 μm, and the value obtained by multiplying the rib height by the rib width was as small as 1500 μm ² , so the Ag diffusion evaluation was "B". In addition, in Comparative Example 3, the rib height was as small as 5 μm, the rib width was as small as 50 μm, and the value obtained by multiplying these was extremely small as 250 μm ² . It was "B" impossible. In Comparative Example 4, the rib height was too large, ie, 40 μm, so the bondability was evaluated as failing “B”. In Comparative Example 5, in which ribs were not formed, although the bondability was evaluated as "A", wax stains were observed at multiple locations, and discoloration of the oxygen-free copper plate occurred. Both wax stains and Ag diffusion were evaluated as unsatisfactory "B".

1 Insulated circuit board 2 Ceramic substrate 21a Surface 21b Surface 3 Circuit layer 4 Metal layer 30 Circuit layer metal plate 31a Surface 31c End surface 32 Rib 40 Metal layer metal plate 41a Surface 42 Rib 50 Brazing material 51 Remaining solder 61 62 Pressure plate 100 laminate

Claims (4)

An insulated circuit board having a circuit layer formed on one surface of a ceramic substrate,
ribs are formed on the surface of the circuit layer opposite to the ceramic substrate, and surround a surface to be mounted on which a semiconductor element is to be mounted;
The insulation characterized in that the rib has a height of 10 μm or more and 30 μm or less, a width of the rib of 100 μm or more, and a value obtained by multiplying the rib height by the rib width is 2000 μm or ^more . circuit board. 2. The insulated circuit board according to claim 1, wherein said rib is formed along the edge of said circuit layer. 3. The insulated circuit board according to claim 1, wherein said circuit layer is made of any one of aluminum, aluminum alloy, copper, and copper alloy. a laminate forming step of forming a laminate by arranging a circuit layer metal plate having ribs surrounding a mounting surface on which a semiconductor element is to be mounted on one surface of a ceramic substrate via a brazing material;
a bonding step of bonding the circuit layer metal plate to one surface of the ceramic substrate to form a circuit layer by applying pressure and heat to the laminate in the stacking direction;
The rib height is 10 μm or more and 30 μm or less, the rib width is 100 μm or more, and the value obtained by multiplying the rib height by the rib width is 2000 μm or more ^,
A method of manufacturing an insulated circuit board, wherein in the joining step, a pressure plate is brought into contact with the rib to press the laminate.

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