JP2001358267A - Semiconductor device and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device provided with a plurality of protrusions for controlling the thickness of junctions on a backside pattern of an insulation substrate or on a base plate, wherein a thermal stress generated in the junctions around the protrusions can be suppressed, an anti-crack property of the junctions can be increased, and a high reliability can be secured. SOLUTION: The backside pattern of the insulation substrate or the base plate is provided with a plurality of protrusions for controlling the thickness of the junctions between the backside pattern and base plate. An end of each protrusion facing the periphery of the backside pattern is located 1 to 10 mm away from the peripheral edge of the pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power module, and more particularly to a semiconductor device in which an insulating substrate and a base plate are joined at a joint, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 17 and FIG.
FIG. 17 is a view showing a conventional semiconductor device disclosed in Japanese Patent Publication No. 186331, FIG. 17 is a sectional view thereof, and FIG. 18 is a perspective view showing a base plate. In the figure, 1 is a semiconductor element made of Si, 2 is aluminum nitride as a ceramic, 3 and 4 are conductive patterns provided on both sides of the aluminum nitride 2, a front side pattern and a back side pattern, and 5 is a ceramic 2 and a front side. An insulating substrate composed of the side pattern 3 and the back side pattern 4; 6 a base plate; 7 a solder used for fixing the semiconductor element 1 and the insulating substrate 5; 8 a fixation between the insulating substrate 5 and the base plate 6 18 are a plurality of projections metal-joined in the vicinity of each corner of the base plate, made of aluminum or the like, and arranged in parallel with each other. Are located close to the peripheral edge 4a of the back side pattern 4 of the insulating substrate 5.

In the state shown in FIG. 17, first, a semiconductor device is placed in a decompression tank at a temperature equal to or higher than the melting temperature of a joint 8 such as solder and under atmospheric pressure. At this time, the joint 8 is in a molten state, and countless small-diameter voids are generated inside. Next, when the pressure in the decompression tank is reduced, the pressure in the void is higher than the pressure in the tank, so that the void expands and becomes large, for example, by merging with a nearby void. In addition, the voids increase in fluidity due to the increase in size, gradually move in the molten bonding material, and dissipate in the surrounding tank. Next, if the depressurized state is continued for a while, the voids are almost scattered into the surrounding tank, and only the void around the projection 9 and only a few voids are formed. Next, when the inside of the decompression tank is returned to the atmospheric pressure, the pressure of the melted joint 8 becomes equal to the pressure in the tank, so that the void existing around the projection 9 and the void slightly remaining in the joint 8 contract. , Become smaller. Thereafter, the joint 8 is solidified to join the insulating substrate 5 and the base plate 6 by the joint 8. Thus, the voids in the joint 8 having the protrusions 9 are sufficiently small.

The plurality of projections 9 are metal-bonded in the vicinity of each corner of the base plate 6, and when the back side pattern 4 and the base plate 6 are bonded by a bonding portion 8 such as solder.
The thickness of the joint 8 is regulated.

On the other hand, when a fluxless solder is used as the solder, a cleaning step using a chemical solution, which has been conventionally used, is not required in the soldering step, and environmental problems can be solved.
Further, the manufacturing cost can be reduced.

[0006]

A conventional semiconductor device is:
Since a plurality of projections are metal-joined in the vicinity of each corner of the base plate, these projections may be located very close to the periphery of the back side pattern of the insulating substrate. In addition, there is a problem that thermal stress concentrates on a joint such as solder positioned around the end of the protrusion, and cracks are generated in the joint early from the protrusion. Further, in the step of soldering the back side pattern and the base plate using a fluxless solder, when soldering is performed under atmospheric pressure or reduced pressure, poor solder wettability on the solder bonding surface occurs. Had the problem of fear.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and suppresses a thermal stress that is likely to occur in a joint such as a solder located around the end of a projection, thereby reducing the joint. It is an object of the present invention to improve the crack resistance of a part and provide a semiconductor device having excellent reliability.

Further, the present invention provides a method of manufacturing a semiconductor device capable of improving the wettability of solder at a solder joint surface in a step of solder-joining the back side pattern and the base plate using a fluxless solder. The purpose is to provide.

[0009]

According to a first aspect of the present invention, there is provided a semiconductor device in which conductive patterns are formed on both sides, a semiconductor element is mounted on a front side pattern, and a base plate has a joint on a back side pattern. In a semiconductor device comprising an insulating substrate joined through a plurality of projections for regulating the thickness of the joining portion on the back side pattern or the base plate, the projections are provided on the periphery of the back side pattern. The facing end is located in a region 1 mm to 10 mm apart from the peripheral edge.

The semiconductor device according to a second aspect of the present invention is the semiconductor device according to the first aspect, wherein the back side pattern has a square portion, and the projection is provided near the corner of the back side pattern. It extends obliquely with respect to the side of the shape portion.

A semiconductor device according to a third aspect of the present invention comprises:
In the semiconductor device according to the second aspect, the back side pattern has a rectangular portion, and the protrusion extends at approximately 45 degrees with respect to the side of the rectangular portion.

Further, a semiconductor device according to a fourth aspect of the present invention comprises:
In the semiconductor device according to the first invention, the projection is joined to the base plate, and the projecting surface of the projection is configured to be substantially parallel to the joining surface of the base.

Further, a semiconductor device according to a fifth aspect of the present invention comprises:
In the semiconductor device according to the first invention, the projection is bonded to the back side pattern, and the projection surface of the projection is configured to be substantially parallel to the surface of the back side pattern.

A method of manufacturing a semiconductor device according to a sixth aspect of the present invention comprises the steps of: mounting a semiconductor element on a front side pattern of an insulating substrate having conductive patterns formed on both sides; Before joining the back side pattern and the base plate, providing a plurality of projections on the back side pattern or the base plate for regulating the thickness of the joint portion. In the method of manufacturing a semiconductor device, the protrusion has an end facing the periphery of the back surface side pattern of 1 mm from the periphery.
A step of forming the base plate so as to be located in a region of 10 mm to 10 mm. When the base plate is joined to the back side pattern, a reducing gas or an inert gas, or a mixed gas of a reducing gas and an inert gas is used. It is performed in the atmosphere.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Embodiment 1 of the present invention will be described with reference to FIGS. 1 is a sectional view of the semiconductor device, FIG. 2 is a partially enlarged bottom view of the insulating substrate,
3 is a plan view of the base plate, FIG. 4 is a thermal stress characteristic diagram of the solder in which the insulating substrate and the base plate are joined, FIG. 5 is a cross-sectional view showing a state in which the insulating substrate and the base plate are joined, and FIG. It is a partial enlarged bottom view of a board | substrate. In the figure, 1 is a semiconductor element made of Si, 2 is ceramics, and the corner 2a is aluminum nitride having a round shape, 3 is a surface side pattern provided on the surface of the aluminum nitride 2, and 4 is This is a back side pattern provided on the back side, and a rectangular peripheral edge 4a such as a rectangle or a square is constituted by each side 4b, 4c, 4d, 4e and a circular corner 4f. 5 is an insulating substrate composed of the aluminum nitride 2, the front side pattern 3, and the back side pattern 4, 6
Is a base plate, and a dashed line 6b on the upper surface 6a is an imaginary line indicating a region facing the rectangular peripheral edge 4a of the back side pattern 4, and is formed by dividing each side 6c, 6d, 6e, 6f and a circular corner 6g. Have. Reference numeral 7 denotes solder used for fixing the semiconductor element 1 to the insulating substrate 5, 8 denotes a joint made of solder used for fixing the insulating substrate 5 to the base plate 6, and 90 denotes a corner 6 g of the base plate 6.
Are made of an aluminum material or the like, and are arranged in parallel with each other. As shown by L1 and L2 in FIG.
Indicates a broken line 6 indicating a region facing the back side pattern 4.
1 m from each side 6c, 6d, 6e, 6f of b and the corner 6g
m or more. Here, since the dashed line 6b of the base plate 6 and the peripheral edge 4a of the back side pattern 4 are opposed to each other, each end 90a, 90b of the projection 90 is located on the back side of the insulating substrate 5 indicated by a broken line in FIG. In the drawing, the region facing the side pattern 4 is one side from the sides 4b, 4c, 4d, and 4e of the peripheral edge 4a of the back side pattern 4 as indicated by L1 and L2 in FIG.
mm or more.

When the insulating substrate 5 and the base plate 6 are metal-bonded, the thermal stress applied to the solder at the bonding portion 8 is, as a result of the experiment, as shown in FIG. It was found that when the size was smaller than 1 mm, the stress sharply increased, and when it was 1 mm or more, the stress was greatly reduced. In the first embodiment, a position where the thermal stress is reduced, that is, a position of 1 mm or more is selected based on the experimental results shown in the graph of FIG.
0a, 90b. Therefore, the protrusion 90
The thermal stress generated in the joints 8 around the ends 90a and 90b of the first and second joints is suppressed, the crack resistance of the joints 8 is improved, and a semiconductor device having excellent reliability can be obtained.

When the back side pattern 4 of the insulating substrate 5 and the base plate 6 are joined by soldering, the thickness of the joint 8 is regulated by the protrusion 90. The experimental results shown in the graph of FIG. In the case where the ends 90a and 90b of the protrusion 90 are arranged at the position where the thermal stress is reduced based on the above, the dimension from the peripheral edge 4a of the back side pattern 4 is 10 m in FIG.
When the ends 90a and 90b are separated from each other beyond m, the protrusion 90
Of the insulating substrate 5 around the end 90a of
The thickness d of the joining portion 8 of the peripheral edge 4a becomes thinner than the end portion 90a, and thermal stress tends to concentrate on the thin portion. In the first embodiment of the present invention, the end portion of the projection 90 in FIG. Since the positions of 90a and 90b are located 1 mm or more and 10 mm or less from the peripheral edge 4a of the back side pattern 4 like L1 and L2, the ends 90a and 90b of the protrusion 90 are provided.
, The inclination α is slight in the insulating substrate 5, the inclination α is slight, and the thickness of the joint 8 can be ensured. Here, in FIG. 5, the relationship among the thermal stress Δε, the amount of deformation ΔL of the joint 8 in the length direction of the solder, and the thickness d of the solder at the joint is Δε = K × ΔL / d. Joint 8 as described above
Is ensured, the concentration of thermal stress can be prevented. Therefore, generation of cracks in the peripheral portion of the joint 8 can be prevented.

Embodiment 2 FIG. Embodiment 2 of the present invention will be described with reference to FIGS. 7, 8, and 9. FIG. 7 is a rear view of the insulating substrate used in the semiconductor device, FIG. 8 is a plan view of the base plate, and FIG. 9 is a partially enlarged plan view of FIG. In FIG. 7, reference numeral 4 denotes a back surface side pattern provided on the back surface, and a rectangular peripheral edge 4a is constituted by sides 4b, 4c, 4d, and 4e and a circular corner 4f. 8 and 9, reference numeral 6 denotes a base plate, and a broken line 6b on the upper surface 6a is an imaginary line indicating a region facing the rectangular peripheral edge 4a of the back side pattern 4, and each side 6c, 6d, 6e, 6f , And 6 g of circular corners. Reference numeral 90 denotes a plurality of projections which are metal-joined in the vicinity of the corners 6g of the broken line 6b of the base plate 6 and extend obliquely with respect to the sides 6c, 6d, 6e, 6f. And each end 90a, 90b
Each side 6c, 6d, 6e, 6f of a broken line 6a indicating a region facing the back surface side pattern 4 and 1 mm to
They are separated within a range of 10 mm. Therefore, the protrusion 90
The end portions 90a and 90b of the back side pattern 4 have respective sides 4b and 4b as shown by L1 and L2 in FIG.
c, 4d, and 4e are separated from the corner 4f in a range of 1 mm to 10 mm.

In this configuration, the plurality of projections 90 are provided on the sides 6c, 6d, 6c near the corner 6g of the broken line 6b indicating the area of the base plate 6 facing the back side pattern 4.
e, 6f, the plurality of protrusions 9 are provided on the sides 4a, 4b, 4
It also extends obliquely with respect to c and 4d. Therefore, if only the position of the end 9a is separated from the broken line 6b by 1 mm, the end 9b is naturally located on the periphery 4 of the back side pattern 4.
It is located at a distance of less than 1 mm from “a” and in a region with low thermal stress. That is, it is easier to position the protrusion 90 in a region where the thermal stress is low, as compared with the case where the protrusion 90 is arranged in parallel to each of the sides 4a, 4b, 4c and 4d.

In the first and second embodiments of the present invention, the projections are described as being joined to the base plate. However, the same effects can be obtained by joining the projections to the insulating substrate.

Embodiment 3 Third Embodiment A third embodiment of the present invention will be described with reference to FIGS. FIG. 10 is a bottom view of the insulating substrate used for the semiconductor device, and FIG. 11 is a partially enlarged bottom view thereof. In the figure, 2 is made of ceramics and has sides 2a, 2b, 2
In the aluminum nitride having c and 2d, inclined portions 2e are formed at both corners of one side 2c, and each corner 2f is formed in a circular shape. Numeral 4 is formed in a small shape similar to the aluminum nitride 2 and each side 4b, 4c, 4d, 4
In the back side pattern composed of e and circular corners 4f, inclined portions 4g are formed at both corners of one side 4d. 90
Is a plurality of protrusions which are metal-joined in the vicinity of the corners 4f of the back side pattern 4 and extend approximately 45 degrees with respect to each side 4b, 4c, 4d, 4e of the rectangular portion. Corner 90 of end 90a facing peripheral edge 4a of side pattern 4
c is 2.5 mm away from the peripheral edge 4 a of the back side pattern 4.

In this configuration, the protrusions 90 are metal-bonded in the vicinity of the corners 4f of the insulating substrate 4, and the sides 4 of the square portion are formed.
Since b, 4c, 4d, and 4e extend at approximately 45 degrees, if one corner 9c of the end 9a is positioned, the other is naturally separated by 2.5 mm from the periphery of the back side pattern. Positioning when joining the projections 90 becomes extremely easy. Further, since the distance from the both sides 4a and 4d of the back surface side pattern 4 is substantially the same, the protrusion 90
And the thermal stress on both sides becomes uniform, so that the thermal stress can be prevented from concentrating on one of the side 4a side or the side 4d side of the protrusion 90.

In the above embodiment of the present invention, the corner 90c of the end 90a of the projection 90 has been described as being separated from the periphery of the backside pattern 4 by 2.5 mm. The same effect can be obtained as long as it is separated from the peripheral edge 4a in a region of 1 mm to 10 mm.

Further, in the third embodiment of the present invention, the projection is joined to the insulating substrate. However, the same effect can be obtained by joining the projection to the base plate.

Embodiment 4 Embodiment 4 of the present invention will be described with reference to FIGS. FIG. 12 is a sectional view of a base plate, and FIG. 13 is a sectional view of a semiconductor device using the base plate. In the figure, reference numeral 90 denotes a projection made of a bonding wire piece, which is metal-joined in the vicinity of each corner of the base plate 6, and whose protruding surface 90 c is substantially parallel to the upper surface 6 a of the base plate 6.

In this configuration, since the projecting surface 90c of the projection 90 is substantially parallel to the upper surface 6a of the base plate 6, the surface 4h of the back side pattern 4 becomes parallel to the upper surface 6a of the base plate 6, and In contrast to 6, the inclination of the surface 4h of the back side pattern 4 can be prevented, the thickness of the joint 8 can be made uniform, the concentration of thermal stress can be suppressed, and the occurrence of cracks in the joint 8 can be prevented.

Embodiment 5 FIG. Embodiment 5 of the present invention will be described with reference to FIG. FIG. 14 is a cross-sectional view showing a state in which the protrusions are bonded to the insulating substrate. In the figure, reference numeral 90 denotes a protrusion formed of a bonding wire piece, which is metal-bonded in the vicinity of each corner of the back side pattern 4 and has a protrusion. Surface 90c
Are substantially parallel to the surface 4h of the back side pattern 4.

In this configuration, the surface 4h of the back side pattern 4
On the other hand, since the projection surface 90c of the projection 90 is substantially parallel,
The surface 4h of the back side pattern 4 and the joining surface of the base plate 6 become parallel, and the surface 4h of the back side pattern 4
Can be prevented, and similarly to the fourth embodiment, the thickness of the joint 8 can be made uniform, the concentration of thermal stress can be suppressed, and the occurrence of cracks in the joint can be prevented.

Embodiment 6 FIG. A sixth embodiment of the present invention will be described with reference to FIGS. FIG. 15 is a flowchart showing the manufacturing process of the present invention, and FIG. 16 is a plan view showing a base plate. First, in S1, a front-side pattern 3 and a back-side pattern 4 are formed on both surfaces of aluminum nitride 2. At this time, the back side pattern 4 is formed of the respective sides 4b, 4c, 4
It is formed to have d and 4e. Next, in S2, the rectangular sides 4b, 4c, 4d, 4
The projection 9 is bonded by bonding such that the bonding wire is inclined at approximately 45 degrees with respect to e. At this time, the projection 90 has an end 90 a facing the peripheral edge 4 a of the back side pattern 4.
It is formed so as to be located in a region of 10 mm to 10 mm. Next, in S3, a fluxless cream solder is applied to a region of the surface pattern 4 of the insulating substrate 5 where the semiconductor element 1 is to be mounted. On the other hand, in step S4, cream solder is also applied to the base plate 6. Next, in S5, the semiconductor element 1 is mounted on the cream solder applied to the front surface side pattern 3 of the insulating substrate 5. Next, in S6, the insulating substrate 5 on which the semiconductor element 1 is mounted is mounted on the fluxless cream solder of the base plate 6. Next, in S7, with the insulating substrate 5 mounted on the base plate 6, the solder is melted in an atmosphere of an inert gas to bond the insulating substrate 5 to the base plate 6, and the insulating substrate 5 to the semiconductor element 1. .

According to this method, even when a fluxless solder is used, the soldering is performed in an atmosphere of an inert gas, so that a decrease in the wettability and fluidity of the solder is suppressed, and the thickness of the solder becomes uniform. , Base plate 6 as shown in FIG.
Of the back side pattern 4 with respect to the
Can be prevented from being concentrated, and cracks in the joint 8 can be further suppressed.

In this method, the case where the projections 90 are provided on the back side pattern 4 of the insulating substrate 5 has been described. However, the projections 90 may be formed on the base plate 6, and in this case, as shown in FIG. Resist 1 for preventing the flow of solder on base plate 6
Then, the protrusions 9 are formed such that the corners 90c of the end portions 90a facing the peripheral edge 4a of the back side pattern 4 are located in a region of 1 mm to 10 mm from the peripheral edge of the back side pattern 4.
Join 0. After that, the protrusion 90 is formed on the back side pattern 4.
Is the same as that in the case where is formed.

In the sixth embodiment of the present invention, the case where soldering is performed in an atmosphere of an inert gas has been described. However, in the atmosphere of a reducing gas or a mixed gas of a reducing gas and an inert gas. Similar effects can be obtained with solder joints.

Further, in the above embodiment of the present invention, the joint 8 is formed by solder, but the same effect can be obtained by using an adhesive.

[0034]

Since the present invention is configured as described above, it has the following effects.

Since the projections have an end facing the periphery of the back side pattern located in a region 1 mm to 10 mm away from the periphery of the back side pattern, thermal stress generated in the solder around the projections is suppressed, and Is improved, and a semiconductor device having excellent reliability can be obtained.

In addition, since the protrusions extend in the vicinity of the corners of the back side pattern having the square portion and are inclined with respect to the sides of the square portion, the positions of only the ends are shifted from the periphery of the back side pattern. If it is separated by 1 mm, the other parts are naturally separated from the peripheral edge by 1 mm, so that the positioning of the projection becomes easy.

Further, the back side pattern has a square portion,
Since the protrusions extend at approximately 45 degrees to the sides of the square portion, the distances from both sides of the back side pattern sandwiching the protrusions are substantially the same, so that the thermal stress on both sides of the protrusions becomes uniform, Concentration of thermal stress can be prevented.

In the case where the projection is joined to the base plate and the projecting surface facing the back side pattern of the projection and the joining surface facing the back side pattern of the base are substantially parallel, or the projection is If the projection surface on the base side of the projection and the surface of the back side poweron are configured to be substantially parallel to each other, the surface of the back side pattern becomes parallel to the base plate, The inclination of the surface of the back side pattern with respect to the base plate can be prevented, the thickness of the joint becomes uniform, the concentration of thermal stress can be suppressed, and cracks at the joint can be prevented.

Further, the protrusion has an end facing the peripheral edge of the back side pattern from 1 mm to 10 mm from the peripheral edge of the back side pattern.
Forming the base plate so as to be located in the region of the insulating substrate, when joining the base plate to the back side pattern of the insulating substrate, a reducing gas, or an inert gas, or a mixed gas of a reducing gas and an inert gas. When performed in an atmosphere, even when using fluxless solder, the wettability and fluidity of the solder are improved, the thickness of the solder is uniform, the inclination of the back side pattern with respect to the base plate is prevented, and Can be prevented from concentrating on thermal stress, and cracks at the joint can be further suppressed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a semiconductor device according to a first embodiment of the present invention;

FIG. 2 is a partially enlarged bottom view of the insulating substrate according to the first embodiment of the present invention;

FIG. 3 is a plan view of a base plate according to the first embodiment of the present invention.

FIG. 4 is a thermal stress characteristic diagram of the solder in which the insulating substrate and the base plate are joined according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a state where the insulating substrate and the base plate according to Embodiment 1 of the present invention are joined together.

FIG. 6 is a partially enlarged bottom view of the insulating substrate according to the first embodiment of the present invention;

FIG. 7 is a back view of the insulating substrate according to the second embodiment of the present invention.

FIG. 8 is a plan view of a base plate according to the second embodiment of the present invention.

FIG. 9 is a partially enlarged plan view of an insulating substrate according to a second embodiment of the present invention.

FIG. 10 is a bottom view of the insulating substrate according to the third embodiment of the present invention.

FIG. 11 is a partially enlarged bottom view of an insulating substrate according to a third embodiment of the present invention.

FIG. 12 is a sectional view of a base plate according to a fourth embodiment of the present invention.

FIG. 13 is a sectional view of a semiconductor device using a base plate according to a fourth embodiment of the present invention.

FIG. 14 is a cross-sectional view showing a state where projections are joined to an insulating substrate according to Embodiment 5 of the present invention.

FIG. 15 is a flowchart showing a sixth embodiment of the present invention.

FIG. 16 is a partially enlarged plan view of a base plate according to Embodiment 6 of the present invention.

FIG. 17 is a cross-sectional view showing a conventional semiconductor device.

FIG. 18 is a perspective view showing a conventional base plate.

[Explanation of symbols]

Reference Signs List 1 semiconductor element, 2 aluminum nitride, 3 front side pattern, 4 back side pattern, 4a peripheral edge, 4b, 4c, 4
d, 4e sides, 5 insulating substrate, 6 base plate, 6a joining surface, 8 joining portion, 90 projection, 90a, 90b end, 90c projecting surface

Claims (6)

[Claims] An insulating substrate having a conductive pattern formed on both sides thereof, a semiconductor element mounted on a front side pattern thereof, and a base plate bonded to a back side pattern via a bonding portion; Alternatively, in the semiconductor device in which a plurality of protrusions for regulating the thickness of the bonding portion are provided on the base plate, the protrusions are regions in which an end facing the peripheral edge of the back side pattern is separated from the peripheral edge by 1 mm to 10 mm. A semiconductor device, which is located in a semiconductor device. 2. A method according to claim 1, wherein the back side pattern has a square portion, and the protrusion extends in the vicinity of a corner of the back side pattern so as to be inclined with respect to a side of the square portion. The semiconductor device according to claim 1. 3. The semiconductor device according to claim 2, wherein the back side pattern has a rectangular portion, and the protrusion extends at substantially 45 degrees to a side of the rectangular portion. 4. The projection is joined to a base plate, and a projecting surface of the projection on the back side pattern side and a joining surface of the base on the back side pattern side are substantially parallel to each other. The semiconductor device according to claim 1, wherein: 5. The projection is bonded to the back side pattern, and a projection surface on the base side of the projection and a surface of the back side pattern are configured substantially parallel to each other.
13. The semiconductor device according to claim 1. 6. A step of mounting a semiconductor element on a front side pattern of an insulating substrate having conductive patterns formed on both sides, a step of bonding a base plate to a back side pattern of the insulating substrate via a bonding portion, In the method for manufacturing a semiconductor device, the method further comprising a step of providing a plurality of protrusions for regulating the thickness of the bonding portion on the back surface side pattern or the base plate before bonding the pattern and the base plate. The edge facing the periphery of the back side pattern is 1 mm from the periphery.
a step of forming the base plate so as to be located in a region of 10 mm to 10 mm. When the base plate is joined to the back side pattern, a reducing gas or an inert gas, or a mixture of a reducing gas and an inert gas is used. A method for manufacturing a semiconductor device, wherein the method is performed in a gas atmosphere.