JP5724244B2 - Manufacturing method of power module substrate, power module substrate, power module substrate with heat sink, and power module - Google Patents

Description

  The present invention relates to a method for manufacturing a power module substrate used in a semiconductor device for controlling a large current and a high voltage, a power module substrate manufactured by the method for manufacturing a power module substrate, a power module substrate with a heat sink, and this The present invention relates to a power module including a power module substrate.

Among semiconductor elements, a power module for supplying power has a relatively high calorific value, and as a substrate on which the power module is mounted, for example, as shown in Patent Document 1, an Al (AlN (aluminum nitride) substrate is formed on a ceramic substrate. A power module substrate in which a metal plate of (aluminum) is bonded via a brazing material is used.
The metal plate is formed as a circuit layer, and a power element semiconductor chip is mounted on the metal plate via a solder material.
In addition, a metal plate made of Al or the like is bonded to the lower surface of the ceramic substrate to form a metal layer for heat dissipation, and the entire power module substrate is bonded to the heat sink via this metal layer. Yes.

  As a means for forming a circuit layer, in addition to a method of forming a circuit pattern on a metal plate after bonding the metal plate to a ceramic substrate, for example, as disclosed in Patent Document 2, a circuit pattern is previously formed. A method of joining the formed metal piece to a ceramic substrate has been proposed.

JP 2003-086744 A JP 2008-311294 A

  By the way, when brazing the ceramic substrate and the metal plate, an Al—Si based alloy brazing foil containing 7.5% by mass or more of Si is often used to set the melting point low. Thus, in an Al-Si alloy containing a relatively large amount of Si, it is difficult to produce a foil material by rolling or the like because of insufficient ductility.

  Moreover, when brazing material foil is used, an oxide film exists on the three surfaces of the surface of the metal plate and both surfaces of the brazing material foil, and the total oxide film present at the interface portion between the metal plate and the ceramic substrate. The thickness tended to increase.

Furthermore, a brazing filler metal foil is disposed between the ceramic substrate and the metal plate, and these are heated by pressurizing them in the laminating direction. It was necessary to laminate and arrange a foil, a ceramic substrate, and a metal plate.
In particular, as described in Patent Document 2, when joining metal pieces formed in a circuit pattern in advance via a brazing material foil, the shape of the joining surface is complicated. It was necessary to improve the positional accuracy of the ceramic substrate and the metal plate.
When the position of the brazing foil is shifted, a molten metal layer cannot be sufficiently formed between the ceramic substrate and the metal plate, and the bonding strength between the ceramic substrate and the metal plate is reduced. There is a fear.

  Furthermore, recently, power modules have been reduced in size and thickness, and the usage environment has become severe, and the amount of heat generated from electronic components such as mounted semiconductor elements tends to increase. Thus, it is necessary to dispose the power module substrate on the heat sink. In this case, since the power module substrate is constrained by the heat radiating plate, a large shearing force acts on the bonding interface between the metal plate and the ceramic substrate during the cooling / heating cycle load. There is a demand for improvement in bonding strength and reliability between a substrate and a metal plate.

  The present invention has been made in view of the above-described circumstances, and provides a power module substrate that is easily and at low cost and in which a metal plate and a ceramic substrate are reliably bonded to each other with high reliability of a thermal cycle. And a power module substrate manufactured by the method for manufacturing a power module substrate, a power module substrate with a heat sink, and a power module including the power module substrate. Objective.

In order to solve the above problems and achieve the above object, a method for manufacturing a power module substrate according to the present invention is for a power module in which a metal plate made of aluminum is laminated and bonded to the surface of a ceramic substrate. a method for manufacturing a substrate, said by fixing the Si to at least one of the bonding surfaces and bonding surfaces of the metal plate of the ceramic substrate, including 0.002 mg / cm ² or more 1.2 mg / cm ² or less of Si A Si fixing step for forming a Si layer, a laminating step for laminating the ceramic substrate and the metal plate through the Si layer, pressurizing and heating the laminated ceramic substrate and the metal plate in a laminating direction, A heating step for forming a molten metal region at the interface between the ceramic substrate and the metal plate, and solidifying the molten metal region A solidifying step for joining the ceramic substrate and the metal plate, and in the heating step, by diffusing Si of the Si layer to the metal plate side, at the interface between the ceramic substrate and the metal plate. Forming the molten metal region made of an Al-Si eutectic system, and maintaining the temperature constant in the state in which the molten metal region is formed in the solidification step, and further adding Si in the molten metal region to the metal By diffusing to the plate side, solidification of the molten metal region proceeds while the temperature is kept constant .

In the manufacturing method of the power module substrate having this configuration, Si is fixed to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate, and is 0.002 mg / cm ² or more and 1.2 mg / cm ^2. It comprises a Si fixing step for forming the following Si layer containing Si, and in the heating step, by diffusing Si of the Si layer toward the metal plate, at the interface between the ceramic substrate and the metal plate, Since the molten metal region made of the Al—Si eutectic system is formed, there is no need to use an Al—Si based brazing foil that is difficult to manufacture, and the metal plate and the ceramic substrate can be reliably manufactured at low cost. A power module substrate bonded to the substrate can be manufactured.

  In addition, since the Si layer is directly formed on at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate without using the brazing material foil, it is necessary to perform an alignment operation of the brazing material foil. There is no. Therefore, for example, even when a metal piece previously formed in a circuit pattern is bonded to a ceramic substrate, troubles due to misalignment can be prevented.

Moreover, when the Si layer is directly formed on the metal plate and the ceramic substrate, the oxide film is formed only on the surface of the metal plate, and the total thickness of the oxide film present at the interface between the metal plate and the ceramic substrate is Since the thickness is reduced, the yield of initial bonding is improved.
The Si layer is formed on at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate. From the viewpoint of productivity, it is preferable to form the Si layer on the bonding surface of the metal plate. . When the Si layer is formed on the bonding surface of the ceramic substrate, the Si layer must be formed on each ceramic substrate. On the other hand, when forming the Si layer on the joint surface of the metal plate, the Si layer is continuously formed from one end to the other end of the long metal strip wound in a roll shape. Is possible, and is excellent in productivity.

Further, since the amount of Si to be fixed is 0.002 mg / cm ² or more, a molten metal region made of an Al—Si eutectic system can be surely formed at the interface between the ceramic substrate and the metal plate, It becomes possible to firmly join the metal plate.
Furthermore, since the amount of Si to be fixed is 1.2 mg / cm ² or less, it is possible to prevent the Si layer itself from being cracked, and from the Al—Si eutectic system at the interface between the ceramic substrate and the metal plate. A molten metal region can be reliably formed. Furthermore, it can be prevented that Si is excessively diffused to the metal plate side and the strength of the metal plate near the interface is excessively increased. Therefore, when a cooling cycle is loaded on the power module substrate, the thermal stress can be absorbed by the metal plate, and cracking of the ceramic substrate can be prevented.

Here, in the Si fixing step, it is preferable that Al is fixed together with Si.
In this case, since Al is fixed together with Si, the Si layer to be formed contains Al and Si, and the generation of cracks in the Si layer can be suppressed. In addition, the Si layer is preferentially melted, so that the molten metal region can be reliably formed, and the ceramic substrate and the metal plate can be firmly bonded. In order to fix Al together with Si, Si and Al may be vapor-deposited at the same time, or sputtering using an alloy of Si and Al as a target. Furthermore, Si and Al may be laminated.

Further, the Si fixing step, deposition, CVD, sputtering, it is preferable that as to fix the Si to at least one of the bonding surfaces and bonding surfaces of the metal plate thus the ceramic substrate in a cold spray over.
In this case, deposition, CVD, sputtering, thus cold spray over, Si is securely affixed to at least one of the bonding surfaces and bonding surfaces of the metal plate of the ceramic substrate, the bonding interface between the ceramic substrate and the metal plate It becomes possible to reliably form the Si layer. In addition, the amount of Si adhered can be adjusted with high accuracy, and it is possible to securely form the molten metal region and firmly bond the ceramic substrate and the metal plate.

  The power module substrate of the present invention is a power module substrate manufactured by the above-described method for manufacturing a power module substrate, wherein Si is dissolved in the metal plate, Of these, the Si concentration in the vicinity of the interface with the ceramic substrate is set in the range of 0.05 mass% to 0.5 mass%.

In the power module substrate having this configuration, Si is dissolved in the metal plate, and the Si concentration in the bonding interface side portion is set to 0.05% by mass or more. Is sufficiently diffused to the metal plate side, and the metal plate and the ceramic plate are firmly joined. Furthermore, the joint interface side portion of the metal plate is solid-solution strengthened by Si. Thereby, generation | occurrence | production of the crack in a metal plate part can be prevented, and the improvement of the joining reliability of the board | substrate for power modules can be aimed at.
Moreover, since the Si concentration at the bonding interface side portion is set to 0.5% by mass or less, it is possible to prevent the strength of the metal plate in the vicinity of the interface from being excessively increased, and a cooling cycle is loaded on the power module substrate. In this case, the thermal stress can be absorbed by the metal plate, and cracking of the ceramic substrate can be prevented.

The power module substrate of the present invention is a power module substrate manufactured by a method for manufacturing a power module substrate, wherein the ceramic substrate is any one of AlN, Al ₂ O ₃ and Si ₃ N _4. It is characterized by being composed.
In the power module substrate having this configuration, the ceramic substrate is made of any one of AlN, Al ₂ O ₃ and Si ₃ N ₄ having excellent insulation and strength. Can be provided.

A power module substrate with a heat sink according to the present invention includes the above-described power module substrate and a heat sink that cools the power module substrate.
According to the power module substrate with a heat sink having this structure, since the heat module for cooling the power module substrate is provided, the heat generated in the power module substrate can be efficiently cooled by the heat sink.

A power module according to the present invention includes the power module substrate described above and an electronic component mounted on the power module substrate.
According to the power module having this configuration, the bonding strength between the ceramic substrate and the metal plate is high, and the reliability can be drastically improved even when the usage environment is severe.

  According to the present invention, a method for manufacturing a power module substrate that can easily and inexpensively obtain a power module substrate with a high reliability of a thermal cycle in which a metal plate and a ceramic substrate are reliably bonded, It is possible to provide a power module substrate manufactured by the method for manufacturing a power module substrate, a power module substrate with a heat sink, and a power module including the power module substrate.

It is a schematic explanatory drawing of the power module using the board | substrate for power modules which is embodiment of this invention. It is explanatory drawing which shows Si concentration distribution of the circuit layer and metal layer of the board | substrate for power modules which is embodiment of this invention. It is a flowchart which shows the manufacturing method of the board | substrate for power modules which is embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules which is embodiment of this invention. It is explanatory drawing which shows the joining interface vicinity of the metal plate and ceramic substrate in FIG.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a power module substrate, a power module substrate with a heat sink, and a power module according to an embodiment of the present invention.
The power module 1 includes a power module substrate 10 on which a circuit layer 12 is disposed, a semiconductor chip 3 bonded to the surface of the circuit layer 12 via a solder layer 2, and a heat sink 4. Here, the solder layer 2 is made of, for example, a Sn—Ag, Sn—In, or Sn—Ag—Cu solder material. In the present embodiment, a Ni plating layer (not shown) is provided between the circuit layer 12 and the solder layer 2.

The power module substrate 10 has a ceramic substrate 11, a circuit layer 12 disposed on one surface (the upper surface in FIG. 1) of the ceramic substrate 11, and the other surface (lower surface in FIG. 1) of the ceramic substrate 11. And a disposed metal layer 13.
The ceramic substrate 11 prevents electrical connection between the circuit layer 12 and the metal layer 13, and is made of highly insulating AlN (aluminum nitride). In addition, the thickness of the ceramic substrate 11 is set within a range of 0.2 to 1.5 mm, and in this embodiment is set to 0.635 mm. In the present embodiment, as shown in FIG. 1, the width of the ceramic substrate 11 is set wider than the widths of the circuit layer 12 and the metal layer 13.

  The circuit layer 12 is formed by bonding a conductive metal plate 22 to one surface of the ceramic substrate 11. In the present embodiment, the circuit layer 12 is formed by joining a metal plate 22 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to the ceramic substrate 11.

  The metal layer 13 is formed by bonding a metal plate 23 to the other surface of the ceramic substrate 11. In the present embodiment, the metal layer 13 is formed by joining a metal plate 23 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more, like the circuit layer 12, to the ceramic substrate 11. Is formed.

The heat sink 4 is for cooling the power module substrate 10 described above, and includes a top plate portion 5 joined to the power module substrate 10 and a flow path 6 for circulating a cooling medium (for example, cooling water). It has. The heat sink 4 (top plate portion 5) is preferably made of a material having good thermal conductivity, and in this embodiment, is made of A6063 (aluminum alloy).
In the present embodiment, a buffer layer 15 made of aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC) is provided between the top plate portion 5 of the heat sink 4 and the metal layer 13. .

As shown in FIG. 2, the circuit layer 12 (metal plate 22) is formed at the center in the width direction of the bonding interface 30 between the ceramic substrate 11, the circuit layer 12 (metal plate 22), and the metal layer 13 (metal plate 23). ) And the metal layer 13 (metal plate 23), a concentration gradient layer 33 is formed in which the concentration of Si gradually decreases as the distance from the bonding interface 30 in the stacking direction increases. Here, the Si concentration on the bonding interface 30 side of the concentration gradient layer 33 is set in the range of 0.05 mass% or more and 0.5 mass% or less.
The Si concentration on the bonding interface 30 side of the concentration gradient layer 33 is an average value measured at five points from the bonding interface 30 by the EPMA analysis (spot diameter 30 μm). Further, the graph of FIG. 2 is obtained by performing line analysis in the stacking direction in the central portion of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23), and obtaining the above-mentioned concentration at the 50 μm position as a reference. It is.

  Below, the manufacturing method of the board | substrate 10 for power modules of the above-mentioned structure is demonstrated with reference to FIGS.

(Si fixing step S1)
First, as shown in FIGS. 4 and 5, Si is fixed to the joint surfaces of the metal plates 22 and 23 by sputtering to form Si layers 24 and 25. Here, so that the Si fixed amount of Si layers 24 and 25 is adjusted to 0.002 mg / cm ² or more 1.2 mg / cm ² or less. In the present embodiment, the Si fixing amount in the Si layers 24 and 25 is set to 0.466 mg / cm ² .

(Lamination process S2)
Next, as shown in FIG. 4, the metal plate 22 is laminated on one surface side of the ceramic substrate 11, and the metal plate 23 is laminated on the other surface side of the ceramic substrate 11. At this time, as shown in FIGS. 4 and 5, the metal plates 22 and 23 are laminated so that the surfaces on which the Si layers 24 and 25 are formed face the ceramic substrate 11. That is, Si layers 24 and 25 are interposed between the metal plates 22 and 23 and the ceramic substrate 11, respectively. In this way, the laminate 20 is formed.

(Heating step S3)
Next, the stacked body 20 formed in the stacking step S2 is charged in the stacking direction (pressure 1 to 35 kgf / cm ² ) in a vacuum heating furnace and heated, as shown in FIG. In addition, molten metal regions 26 and 27 are formed at the interfaces between the metal plates 22 and 23 and the ceramic substrate 11, respectively. As shown in FIG. 5, the molten metal regions 26 and 27 are formed by diffusing Si in the Si layers 24 and 25 toward the metal plates 22 and 23, thereby causing Si in the vicinity of the Si layers 24 and 25 of the metal plates 22 and 23. It is formed by increasing the concentration and lowering the melting point. When the pressure is less than 1 kgf / cm ² , there is a possibility that the ceramic substrate 11 and the metal plates 22 and 23 cannot be bonded well. Moreover, when the above-mentioned pressure exceeds 35 kgf / cm < ² >, there exists a possibility that the metal plates 22 and 23 may deform | transform. Therefore, it is preferable that the pressure at the time of pressurizing the laminated body 20 be in the range of 1 to 35 kgf / cm ² .
Here, in this embodiment, the pressure in the vacuum heating furnace is set to 10 ⁻⁶ to 10 ⁻³ Pa, and the heating temperature is set to a range of 630 ° C. to 655 ° C.

(Coagulation step S4)
Next, the temperature is kept constant with the molten metal regions 26 and 27 formed. Then, Si in the molten metal regions 26 and 27 is further diffused to the metal plates 22 and 23 side. As a result, the Si concentration in the portions of the molten metal regions 26 and 27 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. That is, the ceramic substrate 11 and the metal plates 22 and 23 are joined by so-called diffusion bonding (Transient Liquid Phase Diffusion Bonding). After solidification progresses in this way, cooling is performed to room temperature.

  In this way, the metal plates 22 and 23 to be the circuit layer 12 and the metal layer 13 and the ceramic substrate 11 are joined, and the power module substrate 10 according to the present embodiment is manufactured.

  In the power module substrate 10 and the power module 1 according to the present embodiment configured as described above, the ceramic substrate 11, the circuit layer 12 (metal plate 22), and the metal layer 13 (metal plate 23) are made of metal. Molten metal regions 26 and 27 are formed by diffusing Si of the Si layers 24 and 25 formed on the joining surfaces of the plates 22 and 23 toward the metal plates 22 and 23, and the Si of the molten metal regions 26 and 27 is changed to Since bonding is performed by diffusing and solidifying the metal plates 22 and 23, the ceramic substrate 11, the circuit layer 12 (metal plate 22), and the metal layer 13 (metal plate 23) are bonded under relatively short-time bonding conditions. It becomes possible to do.

Further, at the center portion in the width direction of the bonding interface 30 between the ceramic substrate 11 and the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23), the circuit layer 12 (metal plate 22) and the metal layer 13 (metal) A concentration gradient layer 33 is formed in which Si is dissolved in the plate 23), and the concentration of Si gradually decreases as the distance from the bonding interface 30 in the stacking direction is increased. Since the Si concentration is set within a range of 0.05% by mass or more and 0.5% by mass or less, a portion of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) on the bonding interface 30 side. The solid solution strengthens and can prevent the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) from breaking.
Further, Si is sufficiently diffused to the metal plates 22 and 23 side in the heating step S3, and the metal plates 22 and 23 and the ceramic plate 11 are firmly bonded.

Further, by fixing the Si on the bonding surface of the metal plate, provided with a Si fixing step S1 for forming the Si layer 24, 25 comprising 0.002 mg / cm ² or more 1.2 mg / cm ² or less of Si, heating In step S3, Si in the Si layers 24 and 25 is diffused toward the metal plates 22 and 23, so that a molten metal region 26 made of an Al—Si eutectic system is formed at the interface between the ceramic substrate 11 and the metal plates 22 and 23. 27, a power module in which the metal plates 22, 23 and the ceramic substrate 11 are reliably bonded at low cost without the need to use an Al—Si brazing foil that is difficult to manufacture. The substrate 10 can be manufactured.

Further, since the Si adhesion amount in the Si layers 24 and 25 is 0.002 mg / cm ² or more, a molten metal region made of an Al—Si eutectic system is formed at the interface between the ceramic substrate 11 and the metal plates 22 and 23. 26 and 27 can be reliably formed, and the metal plates 22 and 23 and the ceramic substrate 11 can be firmly bonded.
Furthermore, since the Si fixing amount in the Si layers 24 and 25 is 1.2 mg / cm ² or less, it is possible to prevent cracks from occurring in the Si layers 24 and 25 themselves.

In addition, since the Si layers 24 and 25 are formed directly on the joining surfaces of the metal plates 22 and 23 without using the brazing material foil, it is not necessary to perform an alignment operation of the brazing material foil. Therefore, this power module substrate 10 can be produced efficiently.
In addition, since the Si layers 24 and 25 are formed, the oxide film interposed at the interface between the metal plates 22 and 23 and the ceramic substrate 11 exists only on the surfaces of the metal plates 22 and 23, so that The yield of joining can be improved.
Further, in the present embodiment, since the Si layers 24 and 25 are formed on the joint surfaces of the metal plates 22 and 23, the Si fixing step S1 can be performed efficiently.

As mentioned above, although embodiment of this invention was described, this invention is not limited to this, It can change suitably in the range which does not deviate from the technical idea of the invention.
For example, the metal plate constituting the circuit layer and the metal layer has been described as a rolled plate of pure aluminum having a purity of 99.99%, but is not limited to this, and aluminum having a purity of 99% (2N aluminum) It may be.

Moreover, although demonstrated as what provided the buffer layer which consists of aluminum, the aluminum alloy, or the composite material containing aluminum (for example, AlSiC etc.) between the top-plate part of a heat sink and a metal layer, even if this buffer layer is not provided Good.
Furthermore, although the heat sink has been described as being made of aluminum, it may be made of an aluminum alloy or a composite material containing aluminum. Furthermore, although the description has been made with the heat sink having the flow path of the cooling medium, the structure of the heat sink is not particularly limited, and heat sinks having various configurations can be used.

Although the ceramic substrate has been described as being composed of AlN, it is not limited thereto and may be composed of other ceramics such Si ₃ N ₄ or Al ₂ O _3.

Further, although the Si fixing step has been described as a configuration in which Si is fixed to the bonding surface of the metal plate, the present invention is not limited to this, and Si may be fixed to the bonding surface of the ceramic substrate.
Furthermore, in the Si fixing step, the Si layer is formed by sputtering. However, the present invention is not limited to this, and the Si layer may be formed by fixing Si by vapor deposition or CVD. In the Si fixing step, for example, Si and Al may be vapor-deposited at the same time, or an Si / Al alloy may be sputtered to form a Si layer containing Si and Al. Further, Al and Si may be laminated.

Further, the ceramic substrate and the metal plate have been described as being bonded using a vacuum heating furnace, but the present invention is not limited to this, and the ceramic substrate and the metal plate may be used in an N ₂ atmosphere, an Ar atmosphere, or a He atmosphere. You may join with.

A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.
Two metal plates made of 4N aluminum having a thickness of 0.6 mm were prepared, Si was fixed to one side of these metal plates by vacuum deposition, and these two metal plates were made of AlN having a thickness of 40 mm square and a thickness of 0.635 mm. A vacuum heating furnace (vacuum degree: 10 ⁻³ to 10 ⁻⁵⁾ is laminated on both surfaces of the ceramic substrate so that the vapor deposition surface faces the ceramic substrate, and the pressure is 1 to 5 kgf / cm ² in the stacking direction. Pa) was heated to 630 to 650 ° C. to produce a power module substrate including a ceramic substrate, a circuit layer, and a metal layer.

Here, the thickness (Si adhesion amount) of the Si layer formed by vacuum deposition is 0.008 μm (0.0019 mg / cm ² ), 0.6 μm (0.1398 mg / cm ² ), 0.8 μm (0. 1864 mg / cm ² ), 1.0 μm (0.2330 mg / cm ² ), 1.2 μm (0.2796 mg / cm ² ), 1.5 μm (0.3495 mg / cm ² ), 2.4 μm (0.5592 mg / cm ² ) cm ² ), 3.6 μm (0.8388 mg / cm ² ), 4.8 μm (1.1184 mg / cm ² ), 6.0 μm (1.3980 mg / cm ² ), 10 levels of power module substrate did.
A 50 mm × 60 mm, 5 mm thick aluminum plate corresponding to the top plate of the heat sink is disposed on the metal layer side of the power module substrate thus formed through a 0.9 mm thick buffer layer made of 4N aluminum. (A6063) was joined.
These test pieces were loaded in a cooling cycle of −45 ° C. to 105 ° C., and the joining rates were compared. The evaluation results are shown in Table 1.
In addition, the joining rate was computed with the following formula | equation. Here, the initial bonding area is an area to be bonded before bonding.
Bonding rate = (initial bonding area-peeling area) / initial bonding area

The thickness of the Si layer 0.008μm in (0.0019mg / cm ²⁾ and then 6.0μm thickness of Comparative Example 1 and Si layer (1.3980mg / cm ²⁾ and the comparative example 2, the thermal cycle The joining rate at 1000 times was 85% or less, and it was confirmed that the joining strength between the ceramic substrate and the metal plate was insufficient.
On the other hand, in Example 1-8 in which the thickness of the Si layer was in the range of 0.6 to 4.8 μm (0.1398 to 1.1184 mg / cm ² ), the bonding rate at 1000 cooling cycles was 95%. As described above, the bonding rate after 4000 times was 70% or more, and it was confirmed that the ceramic substrate and the metal plate were firmly bonded.

In particular, in Example 3-6 in which the thickness of the Si layer is in the range of 1.0 to 2.4 μm (0.2330 to 0.5592 mg / cm ² ), the bonding rate at 1000 cooling cycles is 99.99. The bonding rate at 5% or more and 4000 times was 85% or more, and it was confirmed that the bonding strength between the ceramic substrate and the metal plate was further improved.

Next, two metal plates made of 4N aluminum having a thickness of 0.6 mm are prepared, Si is fixed to one side of these metal plates by vacuum deposition, and the two metal plates are 40 mm square and have a thickness of 0.635 mm. of the surfaces of the ceramic substrate made of AlN, respectively deposition surface is laminated to the facing ceramic substrate, a vacuum heating furnace in a state pressurized with a pressure 5~35kgf / cm ² in the stacking direction (vacuum degree of ^{10 -3} to 10 ⁻⁵ Pa) to 630 to 650 ° C. to produce a power module substrate including a ceramic substrate, a circuit layer, and a metal layer.

Here, the thickness of the Si layer formed by vacuum deposition (Si adhesion amount) is 0.008 μm (0.0019 mg / cm ² ), 0.1 μm (0.0233 mg / cm ² ), 0.4 μm (0. 0932 mg / cm ² ), 0.6 μm (0.1398 mg / cm ² ), 0.8 μm (0.1864 mg / cm ² ), 1.0 μm (0.2330 mg / cm ² ), 1.2 μm (0.2796 mg / cm ² ) ^{cm 2), 1.5μm (0.3495mg /} cm 2), 2.4μm (0.5592mg / cm 2), 3.6μm (0.8388mg / cm 2), 4.8μm (1.1184mg / cm 2 ), A power module substrate having a 12 level of 6.0 μm (1.3980 mg / cm ² ) was molded.
A 50 mm × 60 mm, 5 mm thick aluminum plate corresponding to the top plate of the heat sink is disposed on the metal layer side of the power module substrate thus formed through a 0.9 mm thick buffer layer made of 4N aluminum. (A6063) was joined.
These test pieces were loaded in a cooling cycle of −45 ° C. to 105 ° C., and the joining rates were compared. The evaluation results are shown in Table 2.
In addition, the joining rate was computed with the following formula | equation. Here, the initial bonding area is an area to be bonded before bonding.
Bonding rate = (initial bonding area-peeling area) / initial bonding area

  Moreover, about these test pieces, Si density | concentration of the metal board vicinity of the joining interface (50 micrometers from a joining interface) of a ceramic substrate was measured by EPMA analysis (spot diameter of 30 micrometers). The measurement results are also shown in Table 2.

In Comparative Example 3 in which the thickness of the Si layer was 0.008 μm (0.0019 mg / cm ² ), even when the pressure applied during bonding was increased to 5 to 35 kgf / cm ² , the cooling / heating cycle 1000 The bonding rate at the time was 63%, and it was confirmed that the bonding strength between the ceramic substrate and the metal plate was insufficient. Further, in Comparative Example 4 in which the thickness of the Si layer was 6.0 μm (1.3980 mg / cm ² ), it was confirmed that the bonding rate after 4000 cooling cycles was as low as 60.3%. .
On the other hand, in Example 9-18 in which the thickness of the Si layer was in the range of 0.1 to 4.8 μm (0.0233 to 1.1184 mg / cm ² ), the bonding rate at 1000 cooling cycles was 89%. As described above, the bonding rate after 4000 times was 70% or more, and it was confirmed that the ceramic substrate and the metal plate were firmly bonded.

Further, when the thickness of the Si layer is 0.1 to 4.8 μm (0.0233 to 1.1184 mg / cm ² ), Si in the vicinity of the bonding interface of the ceramic substrate (50 μm from the bonding interface) of the metal plate. It was confirmed that the concentration was in the range of 0.1 mass% to 0.5 mass%.

1 Power module 3 Semiconductor chip (electronic component)
DESCRIPTION OF SYMBOLS 10 Power module substrate 11 Ceramic substrate 12 Circuit layer 13 Metal layer 22, 23 Metal plate 24, 25 Si layer 26, 27 Molten metal region 30 Bonding interface

Claims (7)

A method for manufacturing a power module substrate in which a metal plate made of aluminum is laminated and bonded to the surface of a ceramic substrate,
Wherein by fixing the Si to at least one of the bonding surfaces and bonding surfaces of the metal plate of the ceramic substrate, Si adhering step of forming a Si layer containing 0.002 mg / cm ² or more 1.2 mg / cm ² or less of Si When,
A laminating step of laminating the ceramic substrate and the metal plate via the Si layer;
Heating and pressurizing and heating the laminated ceramic substrate and the metal plate in a laminating direction to form a molten metal region at the interface between the ceramic substrate and the metal plate;
A solidification step of joining the ceramic substrate and the metal plate by solidifying the molten metal region;
In the heating step, by diffusing Si of the Si layer to the metal plate side, the molten metal region made of an Al-Si eutectic system is formed at the interface between the ceramic substrate and the metal plate ,
In the solidification step, the temperature is kept constant in a state where the molten metal region is formed, and Si in the molten metal region is further diffused to the metal plate side, whereby the temperature is kept constant. A method for producing a power module substrate, comprising solidifying a molten metal region .   The power module substrate manufacturing method according to claim 1, wherein in the Si fixing step, Al is fixed together with Si. The Si fixation step, deposition, CVD, sputtering, according to claim 1 or claim, characterized in that to fix the Si to at least one of the bonding surfaces and bonding surfaces of the metal plate thus the ceramic substrate in a cold spray over The manufacturing method of the board | substrate for power modules of 2. A power module substrate manufactured by the method for manufacturing a power module substrate according to any one of claims 1 to 3,
Si is dissolved in the metal plate, and the Si concentration in the vicinity of the interface with the ceramic substrate in the metal plate is set within a range of 0.05 mass% or more and 0.5 mass% or less. A power module substrate. A power module substrate manufactured by the method for manufacturing a power module substrate according to any one of claims 1 to 3,
The power module substrate, wherein the ceramic substrate is made of any one of AlN, Al ₂ O _3, and Si ₃ N ₄ . 6. A power module substrate with a heat sink, comprising: the power module substrate according to claim 4 ; and a heat sink for cooling the power module substrate. A power module comprising: the power module substrate according to claim 4 ; and an electronic component mounted on the power module substrate.

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