JP2011210947A - Insulating substrate and module with the insulating substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating substrate that passes both a cooling cycle test and a power cycle test.SOLUTION: The insulating substrate 30 is provided between a radiator 20 and a semiconductor device 50. The insulating substrate 30 includes a first wiring layer 31, a ceramic insulating layer 32 and a second wiring layer 33. The first wiring layer 31 is brazed to the radiator 20, and 0.2% proof stress has a first value. The second wiring layer 33 is soldered to the semiconductor device 50, and 0.2% proof stress has a second value. The first value of the first wiring layer 31 is smaller than the second value of the second wiring layer 33.

Description

  The present invention relates to an insulating substrate provided between a radiator and a semiconductor device. The present invention also relates to a module in which a radiator and a semiconductor device are joined via the insulating substrate.

  Patent Document 1 discloses an insulating substrate provided between a radiator and a semiconductor device. This type of insulating substrate has a structure in which a first wiring layer, a ceramic insulating layer, and a second wiring layer are stacked. Each of the first wiring layer and the second wiring layer is brazed to the ceramic insulating layer. Aluminum is often used for the material of the first wiring layer and the second wiring layer, and aluminum nitride is often used for the material of the ceramic insulating layer. In the insulating substrate, the first wiring layer and the radiator are brazed, and the second wiring layer and the semiconductor device are soldered.

  A module including a heat radiator, an insulating substrate, and a semiconductor device is required in various fields. For example, this type of module is used in an in-vehicle inverter circuit that converts DC power into AC power and supplies it to an AC motor.

  A vehicle-mounted inverter circuit is used in an environment with a large temperature fluctuation range. For this reason, in-vehicle inverter circuits must maintain their characteristics even in such an environment. Therefore, this type of module requires high reliability in tests related to stress resistance when it is repeatedly exposed to a temperature environment that varies between low and high temperatures (generally referred to as a thermal cycle test). Further, in a vehicle-mounted inverter circuit, since a large current is controlled to be turned on and off, the mounted semiconductor device itself becomes a high-temperature heating element. For this reason, this type of module is required to have high reliability even in a test related to stress resistance when the semiconductor device is repeatedly turned on and off (generally called a power cycle test).

International Publication No. 2009/116439

  In the insulating substrate used in the module of Patent Document 1, aluminum having the same weight percent (same purity) is used as the material of the first wiring layer and the second wiring layer. However, the present inventors have found that it is difficult to satisfy both the thermal cycle test and the power cycle test when aluminum of the same purity is used for the first wiring layer and the second wiring layer.

  The first wiring layer of the insulating substrate is provided between the radiator and the ceramic insulating layer of the insulating substrate, and is brazed to each of the radiator and the ceramic insulating layer. For this reason, the first wiring layer is subjected to thermal strain due to the difference in thermal expansion between the radiator and the ceramic insulating layer in the thermal cycle test. Therefore, the first wiring layer needs to be designed in consideration of the thermal cycle test.

  On the other hand, the second wiring layer of the insulating substrate is provided between the ceramic insulating layer of the insulating substrate and the semiconductor device, and is brazed to the ceramic insulating layer and soldered to the semiconductor device. For this reason, the second wiring layer and the solder material are in direct contact. In the power cycle test, when the semiconductor device is repeatedly turned on and off, a temperature distribution having a peak near the center is formed in the plane of the semiconductor device. As a result of the study by the present inventors, it has been found that due to this temperature distribution, the joint surface between the second wiring layer and the solder material is deformed so as to wave, and the solder material is damaged. From this knowledge, it has been found that the second wiring layer needs to be designed in consideration of the power cycle test. Thus, as a result of the study by the present inventors, the first wiring layer of the insulating substrate needs to be designed with priority given to the thermal cycle test, and the power cycle test is performed on the second wiring layer of the insulating substrate. It has been found that a design that gives priority to consideration is necessary.

  An object of the technology disclosed in the present specification is to provide an insulating substrate that satisfies both a thermal cycle test and a power cycle test. The technique disclosed in the present specification is further intended to provide a module in which a radiator and a semiconductor device are joined via such an insulating substrate.

  In the technique disclosed in this specification, the 0.2% proof stress value of the portion where the first wiring layer of the insulating substrate is brazed to the heat sink and the second wiring layer of the insulating substrate are soldered to the semiconductor device. It is characterized in that the 0.2% proof stress values of the parts are different. The technique disclosed in the present specification is characterized in that the value of 0.2% proof stress of the part of the first wiring layer is smaller than the value of 0.2% proof stress of the part of the second wiring layer. That is, a relatively soft material having a low 0.2% proof stress is used for the first wiring layer. For this reason, when a soft material is employed for the first wiring layer, even if thermal strain due to the thermal expansion difference between the heat sink and the insulating layer of the insulating substrate is applied to the first wiring layer, the soft first wiring layer Thermal strain can be reduced. Thereby, the reliability in a thermal cycle test can be improved significantly. On the other hand, a material having a high 0.2% proof stress and a relatively hard material is used for the second wiring layer. For this reason, when a hard material is employ | adopted for a 2nd wiring layer, the deformation | transformation of a 2nd wiring layer resulting from a temperature cycle stress is suppressed, and the change of a solder material can be suppressed. Thereby, the reliability in a power cycle test can be improved significantly. Thus, by using materials having different 0.2% proof stress values for the first wiring layer and the second wiring layer, it is possible to provide an insulating substrate that satisfies both the thermal cycle test and the power cycle test. it can.

  That is, the technology disclosed in this specification is embodied in an insulating substrate provided between a heat radiator and a semiconductor device. The insulating substrate includes a first wiring layer, a second wiring layer, an insulating layer provided between the first wiring layer and the second wiring layer and brazed to the first wiring layer and the second wiring layer. And. The first wiring layer has a first portion that is brazed to the radiator. The 0.2% proof stress of the first part is the first value. The second wiring layer has a second portion that is soldered to the semiconductor device. The 0.2% proof stress of the second part is the second value. In the insulating substrate disclosed in this specification, the first value of the first portion of the first wiring layer is smaller than the second value of the second portion of the second wiring layer.

  In the insulating substrate disclosed in this specification, the material of the first portion of the first wiring layer may contain aluminum, and the material of the second portion of the second wiring layer may contain aluminum. In this case, it is desirable that the weight percentage of aluminum in the first part is higher than the weight percentage of aluminum in the second part. That is, different purity aluminum is used for the first part of the first wiring layer and the second part of the second wiring layer, high-purity aluminum is used for the first wiring layer, and the second wiring layer is used for the second wiring layer. It is desirable to use low purity aluminum. High purity aluminum used for the first wiring layer is relatively soft because the 0.2% yield strength value is low. The low-purity aluminum used for the second wiring layer is relatively hard because the 0.2% yield strength value is high. Thus, by using aluminum of different purity for the first wiring layer and the second wiring layer, it is possible to provide an insulating substrate that satisfies both the thermal cycle test and the power cycle test.

  In the insulating substrate disclosed in this specification, the weight percentage of aluminum in the first portion of the first wiring layer is 99.99% or more, and the weight percentage of aluminum in the second portion of the second wiring layer is 99.99. It is desirable to be less than%.

  In the insulating substrate disclosed in this specification, the material of the second portion of the second wiring layer is preferably an aluminum alloy. More preferably, the aluminum weight percentage of the aluminum alloy is 97.55% or less. It has been confirmed in the present specification that the reliability of the power cycle test is improved when an aluminum alloy is used as the material of the second portion of the second wiring layer.

  In the insulating substrate disclosed in this specification, the first wiring layer has a third portion to be brazed to the insulating layer. Furthermore, in the insulating substrate disclosed in this specification, the second wiring layer has a fourth portion that is brazed to the insulating layer. In this case, it is desirable that the weight percentage of aluminum in the third part and the fourth part is the same. According to this insulating substrate, the third portion of the first wiring layer and the fourth portion of the second wiring layer, which have the same weight percentage, are bonded to both surfaces of the insulating layer. For this reason, since the first wiring layer and the second wiring layer can be brazed to both surfaces of the insulating layer under the same conditions, a high-quality insulating substrate can be manufactured.

  In the insulating substrate disclosed in this specification, the first wiring layer may be composed of a plurality of layers having different weight percentages of aluminum. The second wiring layer may also be composed of a plurality of layers having different aluminum weight percentages. In this case, the sum of the products of 0.2% proof stress and thickness of each of the plurality of layers constituting the first wiring layer is equal to the 0.2% proof stress and thickness of each of the plurality of layers constituting the second wiring layer. It is desirable to match the sum of products. According to the insulating substrate of this aspect, the warpage of the insulating substrate is suppressed, and the mountability is improved.

  In the insulating substrate disclosed in this specification, at least one of the first wiring layer and the second wiring layer has a step formed between the central portion and the peripheral portion, and the peripheral portion is thinner than the central portion. Is desirable. According to the insulating substrate of this aspect, thermal distortion at the peripheral edge of the insulating substrate is suppressed.

  According to the technique disclosed in this specification, a module in which a heat radiator and a semiconductor device are joined via the insulating substrate can be provided. The module disclosed in the present specification has high reliability in both the thermal cycle test and the power cycle test. For this reason, it is desirable that the module disclosed in this specification is for in-vehicle use that requires high reliability.

  The insulating substrate disclosed in this specification has high reliability in both the thermal cycle test and the power cycle test.

FIG. 1 shows the configuration of the module. FIG. 2 shows the result of a power cycle test when the material of the second wiring layer of the insulating substrate is changed. FIG. 3 shows a configuration of another example of the insulating substrate. FIG. 4 shows a configuration of another example of the insulating substrate. FIG. 5 shows another example of the structure of the insulating substrate. FIG. 6 shows a configuration of another example of the insulating substrate. FIG. 7 shows a configuration of another example of the insulating substrate. FIG. 8 shows another example of the structure of the insulating substrate.

The features of the technology disclosed in this specification will be summarized.
(Feature 1) The insulating substrate includes a first wiring layer, a ceramic insulating layer, and a second wiring layer. The weight percentage of aluminum in the first wiring layer is higher than the weight percentage of aluminum in the second wiring layer.
(Feature 2) In Feature 1, it is preferable that high purity system aluminum is used for the first wiring layer and an aluminum alloy is used for the second wiring layer. As a result, the first wiring layer is soft and the second wiring layer is hard.
(Feature 3) In Feature 1, the thickness of the second wiring layer is thinner than the thickness of the ceramic insulating layer. In this case, the apparent linear expansion coefficient of the insulating substrate is reduced.

  FIG. 1 shows the configuration of an in-vehicle power module 10. The power module 10 is used for an inverter circuit connected between a DC power source and an AC motor. The power module 10 includes a radiator 20, an insulating substrate 30, and a semiconductor device 50.

  The radiator 20 is a water-cooling type and includes a plurality of through holes through which the cooling water flows. As a material for the radiator 20, an Al—Mn-based aluminum alloy (JIS symbol: A3003) is used.

  The insulating substrate 30 is provided between the radiator 20 and the semiconductor device 50 and has a structure in which a first wiring layer 31, a ceramic insulating layer 32, and a second wiring layer 33 are stacked. The first wiring layer 31 and the ceramic insulating layer 32 are brazed via an Al—Si based brazing material. The second wiring layer 33 and the ceramic insulating layer 32 are also brazed via an Al—Si based brazing material. The first wiring layer 31 of the insulating substrate 30 and the radiator 20 are brazed via an Al—Si brazing material. The second wiring layer 33 of the insulating substrate 30 and the semiconductor device 50 are soldered via a Sn—Cu-based or Sn—Ag—Cu-based solder material 40.

  Pure aluminum is used as the material of the first wiring layer 31 of the insulating substrate 30. The weight percentage of aluminum in the first wiring layer 31 is 99.99% or more (so-called 4N—Al). The 0.2% proof stress of the first wiring layer 31 is 15 MPa and is relatively soft. In one example, the thickness of the first wiring layer 31 is about 0.6 to 3.0 mm.

Aluminum nitride (AlN) is used as the material of the ceramic insulating layer 32 of the insulating substrate 30. Instead of this example, the ceramic insulating layer 32 may be made of a ceramic such as silicon nitride (Si ₃ N ₄ ) or alumina (Al ₂ O ₃ ). In one example, the thickness of the ceramic insulating layer 32 is about 0.3 to 1.0 mm.

  As a material of the second wiring layer 33 of the insulating substrate 30, an Al—Mn based aluminum alloy (JIS symbol: A3003) is used. The weight percentage of aluminum in the second wiring layer 33 is 97.55% or less. The 0.2% proof stress of the second wiring layer 33 is 44 MPa and is relatively hard. In one example, the thickness of the second wiring layer 33 is about 0.2 to 0.6 mm.

  The semiconductor device 50 uses a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or IGBT (Insulated Gate Bipolar Transistor) power device.

  Next, features of the power module 10 will be described. In the insulating substrate 30 used in the power module 10, high-purity high purity aluminum (4N—Al) is used for the first wiring layer 31 on the radiator 20 side, and the second wiring layer 33 on the semiconductor device 50 side is used. A low-purity aluminum alloy (A3003) is used.

In the insulating substrate 30, the first wiring layer 31 is brazed to the radiator 20 and is also brazed to the ceramic insulating layer 32. For this reason, the first wiring layer 31 is strongly restrained by both the radiator 20 and the ceramic insulating layer 32. The thermal expansion coefficient of the aluminum alloy (A3003) that is the material of the radiator 20 is 21 × 10 ⁻⁶ / K, and the thermal expansion coefficient of aluminum nitride (AlN) that is the material of the ceramic insulating layer 32 of the insulating substrate 30 is 5 × 10 ^-6 / K, and the difference in thermal expansion coefficient between the two is large. For this reason, when the power module 10 is repeatedly exposed to a temperature that fluctuates between −40 ° C. and 105 ° C. in the thermal cycle test, the thermal strain caused by the thermal expansion difference between the radiator 20 and the ceramic insulating layer 32 is caused by the first wiring. Join layer 31. However, since soft high-purity aluminum (4N—Al) is used for the first wiring layer 31, it is possible to relieve thermal distortion caused by the thermal expansion difference between the radiator 20 and the ceramic insulating layer 32. For this reason, the power module 10 has high reliability in the thermal cycle test.

  In the insulating substrate 30, the second wiring layer 33 is brazed to the ceramic insulating layer 32 and is soldered to the semiconductor device 50 via the solder material 40. Here, the power cycle test will be described. In the power cycle test, the semiconductor device 50 is repeatedly turned on and off, and the stress resistance caused by the heat generation of the semiconductor device 50 itself is inspected. In the power cycle test, when the semiconductor device 50 generates heat, a temperature distribution having a peak at the center is formed in the surface of the solder material 40.

  If a temperature distribution with a peak at the center is formed in the surface of the solder material, when high purity aluminum (4N-Al) is used for the second wiring layer, the joint surface between the solder material and the second wiring layer Deforms to wave. This is because when the temperature distribution is formed in the surface of the solder material by the power cycle test, the expansion / contraction of the central portion of the solder material becomes larger than the expansion / contraction of the peripheral portion, thereby the bonding surface of the solder material and the second wiring layer. Is presumed to be deformed.

  On the other hand, in this embodiment, a low-purity aluminum alloy (A3003) is used as the material of the second wiring layer 33 of the insulating substrate 30. An aluminum alloy with low purity has a high 0.2% yield strength and is a hard material. For this reason, when a hard aluminum alloy (A3003) is adopted for the second wiring layer 33, the deformation of the second wiring layer 33 is suppressed, thereby suppressing the deformation of the solder material 40 resulting from the power cycle test. Can do.

  FIG. 2 shows the result of the power cycle test when the aluminum material of the second wiring layer 33 is changed. As shown in FIG. 2, in the case of high purity aluminum (4N-Al), the life until the solder material is damaged in the power cycle test is the shortest. On the other hand, when the aluminum alloy (A3003) is used as the material of the second wiring layer 33 as in the present embodiment, the life of the power cycle test is about 1 as compared with the case of pure aluminum (4N-Al). It was confirmed that the life was extended up to 6 times. Although pure aluminum is used, pure aluminum (weight percentage of aluminum is 99% or less, 0.2% proof stress is 33 MPa, JIS symbol: A1100) is lower in purity than high pure aluminum (4N-Al). Even when it was used as the material for the second wiring layer 33, it was confirmed that the life of the power cycle test was extended to about 1.3 times that of pure aluminum (4N-Al). From these results, it was confirmed that a material with a low weight percent of aluminum is preferable for the second wiring layer 33 in consideration of the power cycle test.

  In this way, in the power module 10, high purity pure aluminum (4N-Al) is used for the first wiring layer 31, and low purity pure aluminum (A1100) or aluminum alloy (A3003) with low purity is used for the second wiring layer 33. ) Can satisfy both the thermal cycle test and the power cycle test. The power module 10 can have high reliability in both a cooling cycle test and a power cycle test.

  Hereinafter, with reference to the drawings, other forms of the insulating substrate 30 used in the power module 10 will be exemplified. In addition, the same code | symbol is attached | subjected about the common component of the insulated substrate 30 shown by FIG. 1, and the description may be abbreviate | omitted.

  The insulating substrate 30A shown in FIG. 3 is characterized in that the first wiring layer 31 is composed of two layers. A first layer 31 a is provided on the side to be brazed to the radiator 20, and a second layer 31 b is provided on the side to be brazed to the ceramic insulating layer 32. High purity aluminum (4N—Al) is used as the material of the first layer 31a, and an aluminum alloy (A3003) having the same purity as the second wiring layer 33 is used as the material of the second layer 31b. According to this example, the same purity material is brazed to both surfaces of the ceramic insulating layer 32. For this reason, the joining conditions for brazing the second layer 31b of the first wiring layer 31 to the ceramic insulating layer 32 and the joining conditions for brazing the second wiring layer 33 to the ceramic insulating layer 32 can be made common and joined simultaneously. it can. For this reason, the second layer 31b and the second wiring layer 33 of the first wiring layer 31 can be brazed to the ceramic insulating layer 32 under optimum conditions.

  The insulating substrate 30B shown in FIG. 4 is characterized in that an intermediate layer 31c is provided in the first wiring layer 31. As the material of the intermediate layer 31c, low-pure aluminum (A1100) whose weight percentage of aluminum is between the first layer 31a and the second layer 32b is used. According to this embodiment, when a cooling cycle is applied, the impurities contained in the second layer 31b, which is an aluminum alloy (A3003), are prevented from diffusing into the first layer 31a, which is high-pure aluminum (4N-Al). Is done. For this reason, alteration of the first wiring layer 31 is reduced, and reliability is improved.

  The insulating substrate 30C shown in FIG. 5 is characterized in that the second wiring layer 33 is composed of two layers. A first layer 33 a is provided on the side to be soldered to the semiconductor device 50, and a second layer 33 b is provided on the side to be brazed to the ceramic insulating layer 32. An aluminum alloy (A3003) is used as the material of the first layer 33a, and high-purity aluminum (4N—Al) having the same purity as the first wiring layer 31 is used as the material of the second layer 33b. According to this example, the same purity material is brazed on both surfaces of the ceramic insulating layer 32. For this reason, the joining condition for brazing the second layer 33b of the second wiring layer 33 to the ceramic insulating layer 32 and the joining condition for brazing the first wiring layer 31 to the ceramic insulating layer 32 can be made common and joined simultaneously. it can. As a result, the second layer 33b of the second wiring layer 33 and the first wiring layer 31 can be brazed to the ceramic insulating layer 32 under optimum conditions.

  The insulating substrate 30 </ b> D shown in FIG. 6 is characterized in that an intermediate layer 33 c is provided on the second wiring layer 33. As a material for the intermediate layer 33c, low-pure aluminum (A1100) whose weight percentage of aluminum is between the first layer 33a and the second layer 33b is used. According to this embodiment, when a cooling cycle is applied, the impurities contained in the first layer 33a, which is an aluminum alloy (A3003), are prevented from diffusing into the second layer 33b, which is high-purity aluminum (4N-Al). Is done. For this reason, alteration of the second wiring layer 33 is reduced, and reliability is improved.

  The insulating substrate 30E shown in FIG. 7 is characterized in that both the first wiring layer 31 and the second wiring layer 33 are composed of two layers. The first wiring layer 31 includes a first layer 31a and a bonding layer 31d. The second wiring layer 33 includes a first layer 33a and a bonding layer 33d. Low pure aluminum (A1100) is used for the material of the bonding layer 31d of the first wiring layer 31 and the bonding layer 33d of the second wiring layer 33. According to this example, the same purity material is brazed on both surfaces of the ceramic insulating layer 32. For this reason, the bonding conditions for brazing the bonding layer 31d of the first wiring layer 31 to the ceramic insulating layer 32 and the bonding conditions for brazing the bonding layer 33d of the second wiring layer 33 to the ceramic insulating layer 32 are made common and simultaneously bonded. can do. As a result, the bonding layer 31d of the first wiring layer 31 and the bonding layer 33d of the second wiring layer 33 can be brazed to the ceramic insulating layer 32 under optimum conditions.

  When both the first wiring layer 31 and the second wiring layer 33 are composed of a plurality of layers as in the insulating substrate 30E shown in FIG. 8, it is desirable that the following formula is satisfied.

Here, S _ai is the 0.2% proof stress of each layer of the first wiring layer 31. t _ai is the thickness of each layer of the first wiring layer 31. S _bj is the 0.2% proof stress of each layer of the second wiring layer 33. t _bj is the thickness of each layer of the second wiring layer 33.

  In the example of the insulating substrate 30E shown in FIG. 7, the 0.2% proof stress of the first layer 31a of the first wiring layer 31 is 15 MPa, the thickness is 0.3 mm, and 0.2% of the bonding layer 31d. The proof stress is 33 MPa and the thickness is 0.2 mm. The 0.2% proof stress of the first layer 33a of the second wiring layer 33 is 44 MPa, the thickness thereof is 0.1 mm, the 0.2% proof stress of the bonding layer 33d is 33 MPa, and the thickness thereof is 0.2 mm. It is. The ceramic insulating layer 32 has a thickness of 0.635 mm. For this reason, in the insulating substrate 30E shown in FIG. When Equation 1 is satisfied, the warping of the insulating substrate 30E is suppressed, and the mountability is improved.

  FIG. 8 shows a modification of the insulating substrate 30E of FIG. The insulating substrate 30E is characterized in that, in the first wiring layer 31, the bonding layer 31d is configured to be wider than the first layer 31a. Thereby, in the 1st wiring layer 31, the level | step difference surface 31A is formed between the peripheral part and the center part, and the peripheral part is formed thinner than the center part. Further, in the insulating substrate 30E, also in the second wiring layer 33, the bonding layer 33d is configured to be wider than the first layer 33d. Thereby, also in the 2nd wiring layer 33, the level | step difference surface 33A is formed between the peripheral part and the center part, and the peripheral part is formed thinner than the center part. In the 1st wiring layer 31 and / or the 2nd wiring layer 33, when the thickness of a peripheral part is formed thinly, the thermal distortion of a peripheral part is suppressed and the crack of a peripheral part is suppressed.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

10: power module 20: radiator 30: insulating substrate 31: first wiring layer 32: ceramic insulating layer 33: second wiring layer 50: semiconductor device

Claims (9)

An insulating substrate provided between a radiator and a semiconductor device,
A first wiring layer, a second wiring layer, an insulating layer provided between the first wiring layer and the second wiring layer and brazed to the first wiring layer and the second wiring layer And,
The first wiring layer has a first part brazed to the radiator, and the 0.2% proof stress of the first part is a first value,
The second wiring layer has a second portion soldered to the semiconductor device, and the 0.2% proof stress of the second portion is a second value,
An insulating substrate in which the first value is smaller than the second value. The material of the first portion of the first wiring layer contains aluminum,
The material of the second part of the second wiring layer contains aluminum,
The insulating substrate according to claim 1, wherein a weight percentage of aluminum in the first portion is higher than a weight percentage of aluminum in the second portion. The weight percentage of aluminum in the first portion is 99.99% or more;
The insulating substrate according to claim 2, wherein a weight percentage of aluminum in the second portion is less than 99.99%.   The insulating substrate according to claim 3, wherein a material of the second portion of the second wiring layer is an aluminum alloy.   The insulating substrate according to claim 4, wherein a weight percentage of aluminum in the aluminum alloy is 97.55% or less. The first wiring layer has a third portion brazed to the insulating layer,
The second wiring layer has a fourth portion brazed to the insulating layer,
The insulating substrate according to any one of claims 2 to 5, wherein a weight percentage of aluminum in the third portion and the fourth portion is the same. The first wiring layer is composed of a plurality of layers having different weight percentages of aluminum,
The second wiring layer is also composed of a plurality of layers having different weight percentages of aluminum,
The sum of products of 0.2% proof stress and thickness of each of the plurality of layers constituting the first wiring layer is 0.2% proof stress and thickness of each of the plurality of layers constituting the second wiring layer. The insulating substrate according to any one of claims 2 to 6, which coincides with a sum of the products of the two.   The at least one of the first wiring layer and the second wiring layer has a step formed between a central portion and a peripheral portion, and the peripheral portion is thinner than the central portion. An insulating substrate according to claim 1.   The module with which the heat radiator and the semiconductor device were joined via the insulating substrate as described in any one of Claims 1-8.

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