JP2011201760A - Substrate for power module, substrate with heat sink for power module, power module, method for producing substrate for power module, and method for producing substrate with heat sink for power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for a power module which comprises a metal plate and a ceramic substrate that are surely bonded and which has high heat cycle reliability, to provide a substrate with a heat sink for the power module, the power module with the substrate for the power module, a method for producing the substrate for the power module and a method for producing the substrate with the heat sink for the power module.SOLUTION: The substrate 10 for the power module which is formed by laminating and bonding the metal plates 12, 13 comprising aluminum or an aluminum alloy on and to the surface of the ceramic substrate 11. In the metal plates 12, 13, Ag is solid-solved and the concentration of Ag in the metal plates 12, 13 near the interface with the ceramic substrate 11 is set to be ≥0.05 mass% and ≤10 mass%.

Description

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

Among semiconductor elements, a power element for supplying power has a relatively high calorific value. Therefore, as a substrate on which the power element is mounted, for example, as shown in Patent Document 1, an Al (AlN (aluminum nitride)) ceramic substrate is made of Al ( 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 element) 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 provided. There has been proposed a method of joining a metal piece formed in a shape to a ceramic substrate.

  Here, in order to obtain good bonding strength between the circuit layer and the metal plate as the metal layer and the ceramic substrate, for example, the following Patent Document 3 discloses a technique in which the surface roughness of the ceramic substrate is less than 0.5 μm. Has been.

JP 2003-086744 A JP 2008-311294 A Japanese Patent Laid-Open No. 3-234045

However, when the metal plate is bonded to the ceramic substrate, there is a disadvantage that a sufficiently high bonding strength cannot be obtained even if the surface roughness of the ceramic substrate is simply reduced, and the reliability cannot be improved. For example, even if the surface of the ceramic substrate is subjected to a honing process with Al ₂ O ₃ particles in a dry manner and the surface roughness is set to Ra = 0.2 μm, interface peeling may occur in the peeling test. I understood. Further, even when the surface roughness was set to Ra = 0.1 μm or less by the polishing method, there was a case where the interface peeling occurred in the same manner.

  In particular, power modules have recently been reduced in size and thickness, and the usage environment has become stricter, 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 at the time of thermal cycle loading. There is a demand for improvement in bonding strength and reliability between the metal plate and the metal plate.

  The present invention has been made in view of the above-described circumstances, in which a metal plate and a ceramic substrate are securely bonded to each other, a power module substrate having a high heat cycle reliability, a power module substrate with a heat sink, and the power module. An object of the present invention is to provide a power module including a power substrate, a method for manufacturing the power module substrate, and a method for manufacturing a power module substrate with a heat sink.

  In order to solve such problems and achieve the above object, the power module substrate of the present invention is for a power module in which a metal plate made of aluminum or an aluminum alloy is laminated and bonded to the surface of a ceramic substrate. In the substrate, Ag is solid-solved in the metal plate, and the Ag concentration in the vicinity of the interface with the ceramic substrate in the metal plate is set within a range of 0.05% by mass or more and 10% by mass or less. It is characterized by being.

In the power module substrate having this configuration, Ag is solid-dissolved in the metal plate, so that the bonding interface side portion of the metal plate is solid-solution strengthened. Thereby, the fracture | rupture in a metal plate part can be prevented and joining reliability can be improved.
Here, since the Ag concentration in the vicinity of the interface with the ceramic substrate in the metal plate is set to 0.05% by mass or more, the bonding interface side portion of the metal plate can be surely solid-solution strengthened. Moreover, since the Ag concentration in the vicinity of the interface with the ceramic substrate of the metal plate is 10% by mass or less, it is possible to prevent the strength of the bonding interface of the metal plate from being excessively increased. When a cooling / heating cycle is applied, it is possible to absorb the thermal stress with the metal plate and prevent cracking of the ceramic substrate.

In addition to Ag, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are solid-solved in the metal plate. It is preferable that the total of the Ag concentration in the vicinity of the interface with the ceramic substrate and the concentration of the additive element is set in a range of 0.05% by mass or more and 10% by mass or less.
In this case, in addition to Ag, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved in the metal plate. The part will be solid-solution strengthened. Thereby, the fracture | rupture in a metal plate part can be prevented and joining reliability can be improved.
Here, since the total concentration of Ag and the additive element in the vicinity of the interface with the ceramic substrate in the metal plate is 0.05% by mass or more, the bonding interface side portion of the metal plate is reliably dissolved. Can be strengthened. In addition, since the total concentration of Ag and the additive element in the vicinity of the interface with the ceramic substrate in the metal plate is 10% by mass or less, the strength of the bonding interface of the metal plate is prevented from becoming excessively high. it can.

Furthermore, the ceramic substrate is made of AlN or Si ₃ N ₄ , and the oxygen concentration is set to be twice or more the oxygen concentration in the crystal grains of the ceramic substrate at the bonding interface between the metal plate and the ceramic substrate. A high oxygen concentration portion may be formed, and the thickness of the high oxygen concentration portion may be 4 nm or less.
In this case, an oxygen high-concentration portion having an oxygen concentration of at least twice the oxygen concentration in the crystal grains of the ceramic substrate is formed at the bonding interface between the ceramic substrate made of AlN or Si ₃ N ₄ and the metal plate made of aluminum. Since it is formed, the bonding strength between the ceramic substrate made of AlN or Si ₃ N ₄ and the metal plate made of aluminum is improved by oxygen present at the bonding interface. Furthermore, since the thickness of the high oxygen concentration portion is 4 nm or less, the occurrence of cracks in the high oxygen concentration portion due to stress when a thermal cycle is applied is suppressed.
Here, the oxygen concentration in the crystal grains of the ceramic substrate is an oxygen concentration in a portion of the ceramic substrate that is away from the bonding interface by a certain distance (for example, 5 nm or more).

Moreover, it is preferable that the Ag high concentration part by which Ag density | concentration was made into 2 times or more of Ag density | concentration in the said metal plate was formed in the joining interface of the said metal plate and the said ceramic substrate.
In this case, an Ag high-concentration portion in which the Ag concentration is at least twice the Ag concentration in the metal plate is formed at the bonding interface between the ceramic substrate and the metal plate made of pure aluminum. It is possible to improve the bonding strength between the ceramic substrate and the metal plate by the Ag atoms.
The Ag concentration in the metal plate is the Ag concentration in a portion of the metal plate that is away from the bonding interface by a certain distance (for example, 5 nm or more).

Furthermore, the ceramic substrate is made of AlN, and the mass ratio of Al, Ag, O, and N obtained by analyzing the bonding interface including the high Ag concentration portion by energy dispersive X-ray analysis is Al: Ag: O: N = 50 to 90% by mass: 1 to 30% by mass: 1 to 10% by mass: preferably 25% by mass or less.
Alternatively, the ceramic substrate is made of Si ₃ N ₄ , and the mass ratio of Al, Si, Ag, O, and N analyzed by energy dispersive X-ray analysis of the joint interface including the Ag high concentration portion is as follows. Al: Si: Ag: O: N = 15 to 45% by mass: 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: preferably 25% by mass or less.
Further, the ceramic substrate is made of Al ₂ O ₃ , and the mass ratio of Al, Ag, and O analyzed by energy dispersive X-ray analysis of the bonding interface including the Ag high concentration portion is Al: Ag. : O = 50 to 90% by mass: 1 to 30% by mass: 45% by mass or less is preferable.

  When the mass ratio of Ag atoms present at the bonding interface exceeds 30% by mass, a reaction product of Al and Ag is excessively generated, and this reaction product may inhibit the bonding. In addition, the vicinity of the bonding interface of the metal plate is unnecessarily strengthened by the reactant, and stress may act on the ceramic substrate during a thermal cycle load, and the ceramic substrate may be broken. On the other hand, if the mass ratio of Ag atoms is less than 1% by mass, there is a possibility that the bonding strength by Ag atoms cannot be sufficiently improved. Therefore, the mass ratio of Ag atoms at the bonding interface is preferably in the range of 1 to 30% by mass.

Here, since the spot diameter at the time of performing the analysis by the energy dispersive X-ray analysis method is extremely small, measurement is performed at a plurality of points (for example, 10 to 100 points) on the bonding interface, and the average value is calculated. . Further, when measuring, the bonding interface between the crystal grain boundary of the metal plate and the ceramic substrate is not measured, but only the bonding interface between the crystal grain and the ceramic substrate is measured.
The analytical value obtained by the energy dispersive X-ray analysis method in this specification is the energy dispersive X-ray fluorescence element analyzer NORAN manufactured by Thermo Fisher Scientific Co., Ltd. mounted on the electron microscope JEM-2010F manufactured by JEOL. The acceleration was performed at 200 kV using System7.

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.

  Here, in the above-described power module substrate with a heat sink, a first metal plate made of aluminum or an aluminum alloy is joined to one surface of the ceramic substrate, and the other surface of the ceramic substrate is made of aluminum or an aluminum alloy. A second metal plate is joined, and the heat sink is joined to a surface of the second metal plate opposite to the joint surface with the ceramic substrate, and the second metal plate and Ag is dissolved in the heat sink, and the Ag concentration in the vicinity of the interface between the second metal plate and the heat sink is preferably set in a range of 0.05% by mass or more and 10% by mass or less. .

According to the power module substrate with a heat sink having this configuration, since the Ag is dissolved in the second metal plate and the heat sink, the respective joint interface side portions of the second metal plate and the heat sink are dissolved. It will be strengthened.
Since the Ag concentration in the vicinity of the bonding interface between the second metal plate and the heat sink is 0.05% by mass or more, the bonding interface side portion between the second metal plate and the heat sink is securely dissolved. Can be strengthened. Moreover, since the Ag concentration in the vicinity of the bonding interface between the second metal plate and the heat sink is 10% by mass or less, the strength of the bonding interface between the second metal plate and the heat sink is excessively increased. The thermal distortion can be absorbed by the second metal plate.

Further, in addition to Ag, the second metal plate and the heat sink are solid-dissolved with one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li, It is preferable that the total of the Ag concentration and the concentration of the additive element in the vicinity of the interface between the second metal plate and the heat sink is set in a range of 0.05% by mass to 10% by mass.
In this case, since one or two or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved in the second metal plate and the heat sink in addition to Ag. The joint interface side portion of the second metal plate and the heat sink is solid solution strengthened. Thereby, generation | occurrence | production of the fracture | rupture in said 2nd metal plate and said heat sink can be prevented, and joining reliability can be improved.
Here, since the total concentration of Ag and the additive element in the vicinity of the interface between the second metal plate and the heat sink is 0.05% by mass or more, the interface side between the second metal plate and the heat sink The part can be solid-solution strengthened with certainty. In addition, since the total concentration of Ag and the additive element in the vicinity of the interface between the second metal plate and the heat sink is 10% by mass or less, the strength of the bonding interface between the second metal plate and the heat sink is It can be prevented from becoming excessively high.

In the power module substrate with a heat sink described above, it is preferable that the thickness of the second metal plate is set to be greater than the thickness of the first metal plate.
In this case, the rigidity on the side where the heat sink is provided can be made higher than the rigidity on the opposite side, and the warpage of the power module substrate with a heat sink can be suppressed.

Furthermore, in the above-described power module substrate with a heat sink, the second metal plate is preferably configured by laminating a plurality of metal plates.
In this case, since the second metal plate has a structure in which a plurality of metal plates are laminated, the second metal plate can sufficiently prevent thermal distortion caused by the difference in thermal expansion coefficient between the heat sink and the ceramic substrate. And the occurrence of cracks in the ceramic substrate can be suppressed.

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.

The method for manufacturing a power module substrate according to the present invention is a method for manufacturing a power module substrate in which a metal plate made of aluminum or an aluminum alloy is laminated and bonded to the surface of the ceramic substrate, and the bonding surface of the ceramic substrate A fixing step of fixing Ag to at least one of the joining surfaces of the metal plate and forming a fixing layer containing Ag; and a stacking step of stacking the ceramic substrate and the metal plate via the fixing layer; A heating step of pressurizing and heating the laminated ceramic substrate and the metal plate in a laminating direction to form a molten metal region at an interface between the ceramic substrate and the metal plate, and solidifying the molten metal region. A solidifying step for bonding the ceramic substrate and the metal plate, and in the fixing step, The interface of the serial ceramic substrate and the metal plate, Ag, and is interposed within the 0.01 mg / cm ² or more 10 mg / cm ² or less, in the heating step, to diffuse toward the Ag in the metal plate Thus, the molten metal region is formed at the interface between the ceramic substrate and the metal plate.

According to the method for manufacturing a power module substrate having this configuration, the method includes a fixing step of fixing Ag to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate to form a fixing layer containing Ag. Therefore, Ag intervenes at the bonding interface between the metal plate and the ceramic substrate. Here, since Ag is an element that lowers the melting point of aluminum, a molten metal region can be formed at the interface between the metal plate and the ceramic substrate even under relatively low temperature conditions.
Therefore, it is possible to firmly bond the ceramic substrate and the metal plate even if they are bonded under relatively low temperature and short time bonding conditions.

  Also, in the heating step, Ag is diffused toward the metal plate to form the molten metal region at the interface between the ceramic substrate and the metal plate, and the molten metal region is solidified to thereby form the metal. Since the plate and the ceramic substrate are joined, it is not necessary to use a brazing material foil or the like, and a power module substrate in which the metal plate and the ceramic substrate are securely joined can be manufactured at low cost.

  Thus, since the ceramic substrate and the metal plate can be joined without using a brazing material foil, it is not necessary to perform an alignment operation or the like of the brazing material foil. Even when the formed metal piece is bonded to the ceramic substrate, troubles due to misalignment can be prevented in advance.

Further, in the fixing step, since the fixed amount of Ag interposed at the interface between the ceramic substrate and the metal plate is 0.01 mg / cm ² or more, the molten metal region is formed at the interface between the ceramic substrate and the metal plate. Thus, the ceramic substrate and the metal plate can be firmly bonded.
Furthermore, since the fixed amount of Ag interposed at the interface between the ceramic substrate and the metal plate is 10 mg / cm ² or less, it is possible to prevent cracks from occurring in the fixed layer. It is possible to reliably form a molten metal region at the interface. Furthermore, it can be prevented that Ag diffuses excessively toward the metal plate and the strength of the metal plate near the interface becomes excessively high. 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.

Further, in the fixing step, the interface between the ceramic substrate and the metal plate, the Ag, so is interposed within the 0.01 mg / cm ² or more 10 mg / cm ² or less, of the metal plate the A power module substrate in which the Ag concentration in the vicinity of the interface with the ceramic substrate is in the range of 0.05 mass% or more and 10 mass% or less can be manufactured.

  In addition, since the fixing layer is formed directly on the metal plate and the ceramic substrate, the oxide film is formed only on the surface of the metal plate. As a result, the total thickness of the oxide film present at the interface between the metal plate and the ceramic substrate is reduced compared to the case where the brazing material foil having the oxide film formed on both sides is used, so that the yield of initial bonding can be improved. it can.

Here, in the fixing step, it is preferable to fix one or two or more additional elements selected from Zn, Ge, Mg, Ca, Ga and Li in addition to Ag.
In this case, in addition to Ag, at least one selected from Zn, Ge, Mg, Ca, Ga and Li is added to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate. In addition to Ag, Zn, Ge, Mg, and the like are provided at the bonding interface between the metal plate and the ceramic substrate. One or more additive elements selected from Ca, Ga and Li are present. Here, the additive elements Zn, Ge, Mg, Ca, Ga, and Li are elements that lower the melting point of aluminum in the same manner as Ag, and therefore, at the interface between the metal plate and the ceramic substrate at a relatively low temperature. A molten metal region can be formed.

In the fixing step, it is preferable that Al is fixed together with Ag.
In this case, since Al is fixed together with Ag, the formed fixed layer contains Al, and in the heating process, the fixed layer is preferentially melted to reliably form a molten metal region. Thus, the ceramic substrate and the metal plate can be firmly bonded. In order to fix Al together with Ag, Ag and Al may be vapor-deposited simultaneously, or sputtering may be performed using an alloy of Ag and Al as a target. Al and Ag may be laminated.

Further, the fixing step may be performed by applying Ag to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate by plating, vapor deposition, CVD, sputtering, cold spray, or application of ink in which powder is dispersed. Is preferably fixed.
In this case, Ag is securely fixed to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate by plating, vapor deposition, CVD, sputtering, cold spray, or application of ink in which powder is dispersed. Therefore, Ag can be reliably interposed at the bonding interface between the ceramic substrate and the metal plate. In addition, the amount of Ag 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.

Furthermore, in the fixing step, it is preferable to form the fixing layer by applying an Ag paste to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate.
In this case, it is possible to reliably form the fixed layer by applying the Ag paste. In addition, even if the Ag paste is heated and baked in an air atmosphere, the Ag does not oxidize, so that a fixed layer containing Ag can be easily formed.
In addition, when using Ag paste, in order to prevent the oxidation of a metal plate at the time of heating in air | atmosphere, it is preferable to apply | coat to the ceramic substrate side. Also, the ceramic substrate and the metal plate are laminated in a state where the Ag paste is applied, and the Ag paste is fired when the laminated ceramic substrate and the metal plate are pressed and heated in the lamination direction. It is good also as a structure.

  In the method for manufacturing a power module substrate with a heat sink according to the present invention, a first metal plate made of aluminum or an aluminum alloy is bonded to one surface of a ceramic substrate, and the other surface of the ceramic substrate is made of aluminum or an aluminum alloy. A method of manufacturing a power module substrate with a heat sink, wherein a second metal plate is bonded, and the heat sink is bonded to a surface of the second metal plate opposite to the bonding surface with the ceramic substrate. A ceramic substrate bonding step of bonding the ceramic substrate and the first metal plate, the ceramic substrate and the second metal plate, and bonding the heat sink to one surface of the second metal plate. A heat sink joining step, wherein the heat sink joining step comprises the second metal. An Ag layer forming step of forming an Ag layer by adhering Ag to at least one of the bonding surface and the bonding surface of the heat sink, and laminating the second metal plate and the heat sink via the Ag layer. Heat sink laminating step and heat sink heating step of pressurizing and heating the laminated second metal plate and the heat sink in the laminating direction to form a molten metal region at the interface between the second metal plate and the heat sink And a molten metal solidifying step for bonding the second metal plate and the heat sink by solidifying the molten metal region, and in the heat sink heating step, Ag of the Ag layer is The molten metal region at the interface between the second metal plate and the heat sink is diffused toward the metal plate and the heat sink. It is characterized by the formation.

In the method for manufacturing a power module substrate with a heat sink having this configuration, the heat sink joining step for joining the second metal plate and the heat sink includes at least one of the joining surface of the second metal plate and the joining surface of the heat sink. In addition, since an Ag layer forming step of fixing Ag to form an Ag layer is provided, Ag intervenes at the bonding interface between the second metal plate and the heat sink. Since Ag is an element that lowers the melting point of aluminum, a molten metal region can be formed at the interface between the heat sink and the second metal plate under relatively low temperature conditions.
Therefore, even if it joins on comparatively low temperature and short time joining conditions, it becomes possible to join a heat sink and a 2nd metal plate firmly.

Further, by diffusing Ag in the Ag layer toward the second metal plate and the heat sink, the molten metal region is formed at the interface between the heat sink and the second metal plate. Since the second metal plate and the heat sink are joined by solidifying, it is not necessary to use an Al-Si brazing foil that is difficult to manufacture, and the second metal plate can be manufactured at low cost. Thus, a power module substrate with a heat sink in which the heat sink and the heat sink are securely bonded can be manufactured.
Further, since Ag is directly fixed to at least one of the joining surface of the heat sink and the joining surface of the second metal plate without using the brazing material foil, the positioning operation of the brazing material foil, etc. There is no need to do.
Moreover, when Ag is directly fixed to the joining surface of the heat sink and the joining surface of the second metal plate, the oxide film is formed only on the surfaces of the second metal plate and the heat sink, Since the total thickness of the oxide film present at the interface between the two metal plates and the heat sink is reduced, the yield of initial bonding is improved.

Here, it is preferable to simultaneously perform the ceramic substrate bonding step and the heat sink bonding step.
In this case, by performing the ceramic substrate bonding step and the heat sink bonding step at the same time, the cost required for bonding can be greatly reduced. Further, since it is not necessary to repeatedly heat and cool, it is possible to reduce the warpage of the power module substrate with a heat sink.

Furthermore, it is preferable that the second metal plate is configured by laminating a plurality of metal plates.
In this case, since the second metal plate has a structure in which a plurality of metal plates are laminated, the second metal plate can sufficiently prevent thermal distortion caused by the difference in thermal expansion coefficient between the heat sink and the ceramic substrate. And the occurrence of cracks in the ceramic substrate can be suppressed.

Further, the Ag layer forming step includes plating, vapor deposition, CVD, sputtering, cold spray, or application of paste or ink in which powder is dispersed, and the bonding surface of the heat sink and the bonding surface of the second metal plate. It is preferable to fix Ag to at least one of them.
In this case, Ag is at least one of the bonding surface of the heat sink and the bonding surface of the second metal plate by plating, vapor deposition, CVD, sputtering, cold spray, or application of paste and ink in which powder is dispersed. Since it adheres to one side, it becomes possible to intervene Ag reliably in the joining interface of a heat sink and a 2nd metal plate. In addition, the amount of Ag adhered can be adjusted with high accuracy, and it is possible to securely form the molten metal region and firmly bond the heat sink and the second metal plate.

Furthermore, in the Ag layer forming step, it is preferable to fix Al together with Ag.
In this case, since Al is fixed together with Ag, the formed Ag layer contains Al, and in the heat sink heating step, this Ag layer is preferentially melted to reliably form a molten metal region. It becomes possible, and a heat sink and a 2nd metal plate can be joined firmly. In order to fix Al together with Ag, Ag and Al may be vapor-deposited simultaneously, or sputtering may be performed using an alloy of Ag and Al as a target. Al and Ag may be laminated.

  According to the present invention, a metal plate and a ceramic substrate are securely bonded to each other, and a power module substrate having a high heat cycle reliability, a power module substrate with a heat sink, a power module including the power module substrate, and the power module It is possible to provide a manufacturing method of a power board and a manufacturing method of a power module substrate with a heat sink.

It is a schematic explanatory drawing of the power module using the board | substrate for power modules which is the 1st Embodiment of this invention. It is explanatory drawing which shows Ag concentration distribution and Ge concentration distribution of the circuit layer and metal layer of the board | substrate for power modules which are the 1st Embodiment of this invention. It is a TEM observation figure of the joining interface of the circuit layer of the board | substrate for power modules which is the 1st Embodiment of this invention, a metal layer (metal plate), and a ceramic substrate. It is a flowchart which shows the manufacturing method of the board | substrate for power modules which is the 1st Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules which is the 1st Embodiment of this invention. It is explanatory drawing which shows the joining interface vicinity of the metal plate and ceramic substrate in FIG. It is a schematic explanatory drawing of the power module using the board | substrate for power modules which is the 2nd Embodiment of this invention. It is explanatory drawing which shows Ag density distribution of the circuit layer and metal layer of the board | substrate for power modules which is the 2nd Embodiment of this invention. It is the schematic diagram of the joining interface of the circuit layer of the board | substrate for power modules which is the 2nd Embodiment of this invention, a metal layer (metal plate), and a ceramic substrate. It is a flowchart which shows the manufacturing method of the board | substrate for power modules which is the 2nd Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules which is the 2nd Embodiment of this invention. It is a schematic explanatory drawing of the power module using the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing which shows Ag density distribution of the circuit layer and metal layer of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is a schematic diagram of the junction interface of the circuit layer of the board | substrate for power modules which is the 3rd Embodiment of this invention, a metal layer (metal plate), and a ceramic substrate. It is a flowchart which shows the manufacturing method of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules with a heat sink provided with the board | substrate for power modules which is the 3rd Embodiment of this invention. It is a schematic explanatory drawing of the power module using the board | substrate for power modules with a heat sink which is the 4th Embodiment of this invention. It is explanatory drawing which shows Ag density distribution of the metal layer and heat sink of the board | substrate for power modules with a heat sink which is the 4th Embodiment of this invention. It is a flowchart of the manufacturing method of the board | substrate for power modules with a heat sink which is the 4th Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules with a heat sink which is the 4th Embodiment of this invention. It is explanatory drawing which shows the joining interface vicinity of the 2nd metal plate (metal layer) in FIG. 21, and a heat sink. It is a schematic explanatory drawing of the power module using the board | substrate for power modules with a heat sink which is the 5th Embodiment of this invention. It is a flowchart of the manufacturing method of the board | substrate for power modules with a heat sink which is the 5th Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules with a heat sink which is the 5th Embodiment of this invention. It is explanatory drawing which shows the manufacturing method of the board | substrate for power modules with a heat sink which is the 5th Embodiment of this invention. It is a schematic explanatory drawing of the power module using the board | substrate for power modules with a heat sink which is other embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, a power module substrate, a power module substrate with a heat sink and a power module, and a method for manufacturing the power module substrate according to the first embodiment of the present invention will be described with reference to FIGS.

  A power module 1 shown in FIG. 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. Yes. 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 (the length in the left-right direction in FIG. 1) is set wider than the width of the circuit layer 12 and the metal layer 13.

  As shown in FIG. 5, 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.

  As shown in FIG. 5, 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 the top plate portion 5 joined to the power module substrate 10 and the flow path 6 for circulating a cooling medium (for example, cooling water). And. 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, at the bonding interface 30 between the ceramic substrate 11, 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. In addition to Ag, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved in (metal plate 23).
In the vicinity of the bonding interface 30 between the circuit layer 12 and the metal layer 13, a concentration gradient layer 33 is formed in which the Ag concentration and the concentration of the additive element gradually decrease as the distance from the bonding interface 30 in the stacking direction increases. Here, the total of the Ag concentration in the vicinity of the bonding interface 30 between the circuit layer 12 and the metal layer 13 and the concentration of the additive element is set in a range of 0.05 mass% or more and 10 mass% or less.

Note that the Ag concentration in the vicinity of the bonding interface 30 between the circuit layer 12 and the metal layer 13 and the concentration of the additive element are average values measured at five points from the bonding interface 30 by EPMA analysis (spot diameter 30 μm). . 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.
Here, in the present embodiment, Ge is used as an additive element, and the total of the Ag concentration and the Ge concentration in the vicinity of the junction interface 30 between the circuit layer 12 and the metal layer 13 is set to 0.05 mass% or more and 10 mass% or less. Has been.

Further, when 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) is observed with a transmission electron microscope, as shown in FIG. An Ag high concentration portion 32 in which Ag is concentrated is formed. In the Ag high concentration portion 32, the Ag concentration is set to be twice or more the Ag concentration in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). Note that the thickness H of the Ag high concentration portion 32 is 4 nm or less.
Further, in the Ag high concentration portion 32, the oxygen concentration is set higher than the oxygen concentration in the ceramic substrate 11.

Note that, as shown in FIG. 3, the bonding interface 30 observed here is a lattice image of the ceramic substrate 11 and the interface side end of the lattice image of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). The reference plane S is the center between the end of the bonding interface side. The Ag concentration in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) is constant from the bonding interface 30 in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). This is the Ag concentration in a portion (point A in FIG. 3) that is a distance away (5 nm or more in the present embodiment).
The oxygen concentration in the ceramic substrate 11 is the oxygen concentration in the crystal grains in a portion (point C in FIG. 3) of the ceramic substrate 11 that is away from the bonding interface 30 by a certain distance (5 nm or more in this embodiment). is there.

  The mass ratio of Al, Ag, O, and N when the bonding interface 30 (point B in FIG. 3) is analyzed by energy dispersive X-ray analysis (EDS) is Al: Ag: O: N = 50. It is set in the range of -90 mass%: 1-30 mass%: 1-10 mass%: 25 mass% or less. In addition, the spot diameter at the time of performing the analysis by EDS is 1 to 4 nm, the bonding interface 30 is measured at a plurality of points (for example, 20 points in the present embodiment), and the average value is calculated. Further, the bonding interface 30 between the crystal grain boundaries of the metal plates 22 and 23 constituting the circuit layer 12 and the metal layer 13 and the ceramic substrate 11 is not measured, and the metal plate 22 constituting the circuit layer 12 and the metal layer 13 Only the bonding interface 30 between the crystal grains 23 and the ceramic substrate 11 is a measurement target.

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

(Fixing step S01)
First, as shown in FIGS. 5 and 6, one or two kinds selected from Ag, Zn, Ge, Mg, Ca, Ga, and Li are formed on the respective joint surfaces of the metal plates 22 and 23 by sputtering. The above additive elements are fixed to form the fixing layers 24 and 25.
Here, in the present embodiment, Ge is used as an additive element, the Ag amount in the fixed layers 24 and 25 is 0.01 mg / cm ² or more and 10 mg / cm ² or less, and the Ge amount as the additive element is 0.01 mg / cm ^2. cm ² or more 10 mg / cm ² is set below.

(Lamination process S02)
Next, as shown in FIG. 5, 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. 5 and 6, the metal plates 22 and 23 are laminated so that the surfaces on which the fixing layers 24 and 25 are formed face the ceramic substrate 11. That is, the fixing layers 24 and 25 (Ag and Ge) 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 S03)
Next, the stacked body 20 formed in the stacking step S02 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. 6, the molten metal regions 26 and 27 adhere to the metal plates 22 and 23 by diffusion of Ag and the additive element (Ge) of the fixing layers 24 and 25 toward the metal plates 22 and 23. It is formed by increasing the Ag concentration and additive element concentration (Ge concentration) in the vicinity of the layers 24 and 25 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, the above-mentioned pressurizing pressure is preferably in the range of 1 to 35 kgf / cm ² .
Here, in this embodiment, the pressure in the vacuum heating furnace is set in a range of 10 ⁻³ to 10 ⁻⁶ Pa, and the heating temperature is set in a range of 550 ° C. or more and 650 ° C. or less.

(Coagulation step S04)
Next, the temperature is kept constant with the molten metal regions 26 and 27 formed. Then, Ag and the additive element (Ge) in the molten metal regions 26 and 27 are further diffused toward the metal plates 22 and 23. As a result, the Ag concentration and the additive element concentration (Ge concentration) of the portions that were the molten metal regions 26 and 27 are gradually decreased and the melting point is increased, and solidification proceeds while the temperature is kept constant. Will do. 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, an adhering step S01 for adhering an additive element (Ge) to the bonding surfaces of the metal plates 22 and 23 in addition to Ag. Therefore, Ag and an additive element (Ge) are present at the bonding interface 30 between the metal plates 22 and 23 and the ceramic substrate 11. Here, since Ag and Ge are elements that lower the melting point of aluminum, a molten metal region can be formed at the interface between the metal plate and the ceramic substrate under relatively low temperature conditions.

  Further, the ceramic substrate 11, the circuit layer 12 (metal plate 22), and the metal layer 13 (metal plate 23) are fixed layers containing Ag and an additive element (Ge) formed on the joint surfaces of the metal plates 22 and 23. The molten metal regions 26 and 27 are formed by diffusing 24 and 25 Ag and the additive element (Ge) toward the metal plates 22 and 23, and the Ag and additive element (Ge) in the molten metal regions 26 and 27 are formed. Are diffused into the metal plates 22 and 23 to be solidified, so that the ceramic substrate 11 and the metal plates 22 and 23 are firmly bonded even when bonded under relatively low temperature and short time bonding conditions. It becomes possible.

In addition, at 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), Ag is added to the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). And the additive element (Ge) are in solid solution, and the total of the Ag concentration and additive element concentration (Ge concentration) on the bonding interface 30 side of the circuit layer 12 and the metal layer 13 is 0.05 mass% or more and 10 mass % Of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) on the bonding interface 30 side are solid-solution strengthened, and the circuit layer 12 (metal plate 22). And the generation | occurrence | production of the crack in the metal layer 13 (metal plate 23) can be prevented.
Further, in the heating step S03, Ag and the additive element (Ge) are sufficiently diffused toward the metal plates 22 and 23, and the metal plates 22 and 23 and the ceramic substrate 11 are firmly bonded. .

  Moreover, in this embodiment, the ceramic substrate 11 is made of AlN, and Ag high concentration in which Ag is concentrated at the bonding interface 30 between the metal plates 22 and 23 to be the circuit layer 12 and the metal layer 13 and the ceramic substrate 11. The portion 32 is formed, and the Ag concentration of the Ag high concentration portion 32 is more than twice the Ag concentration in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). The Ag atoms existing in the vicinity of the interface can improve the bonding strength between the ceramic substrate and the metal plate. Moreover, since the thickness of this Ag high concentration part 32 shall be 4 nm or less, it is suppressed that a crack generate | occur | produces in the Ag high concentration part 32 by the stress at the time of applying a heat cycle.

  Furthermore, in this embodiment, the mass ratio of Al, Ag, O, and N obtained by analyzing the bonding interface 30 by the energy dispersive X-ray analysis method is Al: Ag: O: N = 50 to 90% by mass: 1 to 30. Since the mass% is set to 1 to 10 mass%: 25 mass% or less, it is possible to prevent the reaction product of Al and Ag from being excessively generated at the bonding interface 30 to inhibit the bonding, and also due to Ag atoms. The effect of improving the bonding strength can be sufficiently achieved. Further, it is possible to prevent a portion having a high oxygen concentration from being thick at the bonding interface 30 and to suppress generation of cracks when a thermal cycle is loaded.

  In addition, there is provided a fixing step S01 in which Ag and an additive element (Ge) are fixed to the joint surface of the metal plate to form the fixing layers 24 and 25. In the heating step S03, the additive element ( Ge) is diffused toward the metal plates 22 and 23 so that the molten metal regions 26 and 27 are formed at the interface between the ceramic substrate 11 and the metal plates 22 and 23. It is not necessary to use a brazing material foil, and the power module substrate 10 in which the metal plates 22 and 23 and the ceramic substrate 11 are reliably bonded can be manufactured at low cost.

Further, since the fixing layers 24 and 25 are formed directly on the joint surfaces of the metal plates 22 and 23 without using the brazing material foil, it is not necessary to perform the alignment work of the brazing material foil, and the ceramics can be surely used. The board | substrate 11 and the metal plates 22 and 23 can be joined. Therefore, this power module substrate 10 can be produced efficiently.
In addition, since the fixing layers 24 and 25 are formed on the joining surfaces of the metal plates 22 and 23, the oxide film interposed at the interface between the metal plates 22 and 23 and the ceramic substrate 11 is formed on the surfaces of the metal plates 22 and 23. Therefore, the yield of initial bonding can be improved.

  Next, a power module substrate, a power module substrate with a heat sink and a power module, and a method for manufacturing the power module substrate according to the second embodiment of the present invention will be described with reference to FIGS. .

  A power module 101 shown in FIG. 7 includes a power module substrate 110 on which a circuit layer 112 is disposed, a semiconductor chip 3 bonded to the surface of the circuit layer 112 via a solder layer 2, and a heat sink 140. Yes. 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 112 and the solder layer 2.

The power module substrate 110 includes a ceramic substrate 111, a circuit layer 112 disposed on one surface of the ceramic substrate 111 (upper surface in FIG. 7), and the other surface (lower surface in FIG. 7) of the ceramic substrate 111. And a disposed metal layer 113.
The ceramic substrate 111 prevents electrical connection between the circuit layer 112 and the metal layer 113, and is made of Al ₂ O ₃ (alumina) having high insulation. Further, the thickness of the ceramic substrate 111 is set in a range of 0.2 to 1.5 mm, and in this embodiment, is set to 0.635 mm.

The circuit layer 112 is formed by bonding a conductive metal plate 122 to one surface of the ceramic substrate 111. In the present embodiment, the circuit layer 112 is formed by joining a metal plate 122 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to the ceramic substrate 111.
The metal layer 113 is formed by bonding a metal plate 123 to the other surface of the ceramic substrate 111. In this embodiment, similarly to the circuit layer 112, the metal layer 113 is formed by joining a metal plate 123 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to the ceramic substrate 111. Is formed.

The heat sink 140 is for cooling the power module substrate 110 described above, and includes a top plate portion 141 joined to the power module substrate 110 and a flow path 142 through which a cooling medium flows. The heat sink 140 (top plate portion 141) 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 115 made of aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC) is provided between the top plate portion 141 of the heat sink 140 and the metal layer 113. .

As shown in FIG. 8, at the bonding interface 130 between the ceramic substrate 111, the circuit layer 112 (metal plate 122), and the metal layer 113 (metal plate 123), the circuit layer 112 (metal plate 122) and the metal layer 113. Ag is dissolved in (metal plate 123).
More specifically, a concentration gradient layer 133 is formed in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 so that the Ag concentration gradually decreases as the distance from the bonding interface 130 in the stacking direction increases. Here, the Ag concentration in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 is set within a range of 0.05 mass% or more and 10 mass% or less.
The Ag concentration in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 is an average value obtained by measuring five points at a position 50 μm from the bonding interface 130 by EPMA analysis (spot diameter of 30 μm). Further, the graph of FIG. 8 is obtained by performing line analysis in the stacking direction in the center portion of the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123), and obtaining the concentration at the above-mentioned 50 μm position as a reference. It is.

  Further, when the bonding interface 130 between the ceramic substrate 111 and the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123) is observed with a transmission electron microscope, as shown in FIG. An Ag high concentration portion 132 in which Ag is concentrated is formed. In the Ag high concentration portion 132, the Ag concentration is set to be twice or more the Ag concentration in the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123). Note that the thickness H of the Ag high concentration portion 132 is 4 nm or less.

  Note that, as shown in FIG. 9, the bonding interface 130 observed here is the lattice side image of the interface side edge of the lattice image of the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123) and the ceramic substrate 111. The reference plane S is the center between the end of the bonding interface side. The Ag concentration in the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123) is a fixed distance from the bonding interface 130 in the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123). This is the Ag concentration at a distant portion (in this embodiment, 5 nm or more).

  The mass ratio of Al, Ag, and O when the bonding interface 130 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Ag: O = 50 to 90% by mass: 1 to 30% by mass: It is set within a range of 45% by mass or less. In addition, the spot diameter at the time of performing the analysis by EDS is 1 to 4 nm, the bonding interface 130 is measured at a plurality of points (for example, 20 points in the present embodiment), and the average value is calculated. Further, the bonding interface 130 between the crystal grain boundaries of the metal plates 122 and 123 constituting the circuit layer 112 and the metal layer 113 and the ceramic substrate 111 is not measured, and the metal plate 122 and the metal layer 122 constituting the circuit layer 112 and the metal layer 113. Only the bonding interface 130 between the crystal grains 123 and the ceramic substrate 111 is set as a measurement target.

  Below, the manufacturing method of the board | substrate for power modules of the above-mentioned structure is demonstrated with reference to FIG.10 and FIG.11.

(Ag paste application process S101)
First, as shown in FIG. 11, an Ag paste is applied to one surface and the other surface of the ceramic substrate 111 by screen printing to form Ag paste layers 124a and 125a. The thickness of the Ag paste layers 124a and 125a is about 0.02 to 200 μm after drying.
The Ag paste layers 124a and 125a are heated to 150 to 200 ° C. to remove the solvent, and then fired at 300 to 500 ° C. to fire the decomposed Ag paste layer.

The Ag paste used here contains Ag powder, a resin, a solvent, and a dispersant, and the content of the Ag powder is 60% by mass or more and 90% by mass or less of the entire Ag paste. The remainder is made of resin, solvent, and dispersant. In the present embodiment, the content of the Ag powder is 85% by mass of the entire Ag paste.
In the present embodiment, the viscosity of the Ag paste is adjusted to 10 Pa · s to 500 Pa · s, more preferably 50 Pa · s to 300 Pa · s.

The Ag powder has a particle size of 0.05 μm or more and 1.0 μm or less. In this embodiment, an Ag powder having an average particle size of 0.8 μm was used.
As the solvent, those having a boiling point of 200 ° C. or more are suitable, and for example, α-terpineol, butyl carbitol acetate, diethylene glycol dibutyl ether and the like can be applied. In the present embodiment, diethylene glycol dibutyl ether is used.
The resin is for adjusting the viscosity of the Ag paste, and is suitable to be decomposed at 500 ° C. or higher. For example, an acrylic resin, an alkyd resin, or the like can be applied. In this embodiment, ethyl cellulose is used.
In this embodiment, a dicarboxylic acid-based dispersant is added. In addition, you may comprise Ag paste, without adding a dispersing agent.

(Lamination process S102)
Next, the metal plate 122 is laminated on one surface side of the ceramic substrate 111, and the metal plate 123 is laminated on the other surface side of the ceramic substrate 111.

(Heating step S103)
Next, the metal plate 122, the ceramic substrate 111, and the metal plate 123 are charged in a stacking direction (pressure 1 to 35 kgf / cm ² ) in a vacuum heating furnace and heated. At this time, the resin in the decomposed Ag paste layer is removed at the time of 400 to 500 ° C. in the temperature raising process, and Ag fired layers 124 and 125 are formed. The Ag fired layers 124 and 125 become Ag fixing layers in the present embodiment.
Further, by further heating, Ag in the Ag fired layers 124 and 125 diffuses toward the metal plates 122 and 123, and a molten metal region is formed at the interface between the metal plates 122 and 123 and the ceramic substrate 111. Here, in this embodiment, the pressure in the vacuum heating furnace is set in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, and the heating temperature is set in the range of 600 ° C. to 650 ° C.

(Coagulation step S104)
Next, the temperature is kept constant in a state where the molten metal region is formed, and Ag in the molten metal region is further diffused toward the metal plates 122 and 123. Then, the Ag concentration in the portion that was the molten metal region gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. That is, the ceramic substrate 111 and the metal plates 122 and 123 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 power module substrate 110 is produced.

  In the power module substrate 110 and the power module 101 according to the present embodiment configured as described above, the ceramic substrate 111, the circuit layer 112 (metal plate 122), and the metal layer 113 (metal plate 123) are ceramics. A molten metal region is formed by diffusing Ag of the Ag fired layers 124 and 125 formed on one surface and the other surface of the substrate 111 toward the metal plates 122 and 123, and Ag in the molten metal region is Since the metal plates 122 and 123 are joined by further diffusing and solidifying, the ceramic substrate 111 and the metal plates 122 and 123 are firmly joined even if they are joined under relatively low temperature and short time joining conditions. It becomes possible.

  Further, at the bonding interface 130 between the ceramic substrate 111 and the circuit layer 112 and the metal layer 113, Ag is dissolved in the circuit layer 112 and the metal layer 113, and the respective bonding interfaces 130 between the circuit layer 112 and the metal layer 113. Since the Ag concentration on the side is set within the range of 0.05% by mass or more and 10% by mass or less, the portion of the circuit layer 112 and the metal layer 113 on the bonding interface 130 side is strengthened by solid solution, Generation of cracks in the metal layer 113 can be prevented.

Further, in this embodiment, the ceramic substrate 111 is made of Al ₂ O ₃ , and Ag is concentrated on the bonding interface 130 between the ceramic plates 111 and the metal plates 122 and 123 that become the circuit layer 112 and the metal layer 113. Since the Ag high concentration portion 132 is formed and the Ag concentration of the Ag high concentration portion 132 is set to be twice or more the Ag concentration in the circuit layer 112 and the metal layer 113, Ag atoms present in the vicinity of the interface Thus, it is possible to improve the bonding strength between the ceramic substrate and the metal plate. Moreover, since the thickness of this Ag high concentration part 132 is 4 nm or less, it is suppressed that a crack generate | occur | produces in the Ag high concentration part 132 by the stress at the time of applying a heat cycle.

  Furthermore, in this embodiment, the mass ratio of Al, Ag, and O obtained by analyzing the bonding interface 130 by the energy dispersive X-ray analysis method is Al: Ag: O = 50 to 90 mass%: 1 to 30 mass%: 45. Since the content is less than or equal to mass%, it is possible to prevent the reaction between Al and Ag from being excessively generated at the bonding interface 130 and hinder the bonding, and to sufficiently exert the effect of improving the bonding strength by Ag atoms. be able to.

  In the present embodiment, the Ag fired layers 124 and 125 obtained by firing the Ag paste layers 124a and 125a are used as Ag fixing layers, so that Ag is reliably interposed between the ceramic substrate 111 and the metal plates 122 and 123. Can do. In addition, since this Ag paste does not oxidize even when heated and fired in an air atmosphere, the Ag fired layers 124 and 125 can be formed relatively easily.

  Next, a power module substrate, a power module substrate with a heat sink and a power module, and a method for manufacturing the power module substrate according to the third embodiment of the present invention will be described with reference to FIGS. .

  A power module 201 shown in FIG. 12 includes a power module substrate 210 on which a circuit layer 212 is disposed, a semiconductor chip 3 bonded to the surface of the circuit layer 212 via a solder layer 2, and a heat sink 240. Yes. 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 212 and the solder layer 2.

The power module substrate 210 includes a ceramic substrate 211, a circuit layer 212 disposed on one surface (the upper surface in FIG. 12) of the ceramic substrate 211, and the other surface (the lower surface in FIG. 12) of the ceramic substrate 211. And a disposed metal layer 213.
The ceramic substrate 211 prevents electrical connection between the circuit layer 212 and the metal layer 213, and is made of highly insulating Si ₃ N ₄ (silicon nitride). Further, the thickness of the ceramic substrate 211 is set in a range of 0.2 to 1.5 mm, and in this embodiment, is set to 0.32 mm.

The circuit layer 212 is formed by bonding a conductive metal plate 222 to one surface of the ceramic substrate 211. In the present embodiment, the circuit layer 212 is formed by joining a metal plate 222 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to the ceramic substrate 211.
The metal layer 213 is formed by bonding a metal plate 223 to the other surface of the ceramic substrate 211. In the present embodiment, the metal layer 213 is bonded to the ceramic substrate 211 by a metal plate 223 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or higher, like the circuit layer 212. Is formed.

  The heat sink 240 is for cooling the power module substrate 210 described above. The heat sink 240 in the present embodiment includes a top plate portion 241 joined to the power module substrate 210, a bottom plate portion 245 disposed so as to face the top plate portion 241, and the top plate portion 241 and the bottom plate portion 245. The corrugated fins 246 interposed between the top plate portion 241, the bottom plate portion 245, and the corrugated fins 246 define a flow path 242 through which the cooling medium flows.

Here, the heat sink 240 is configured by brazing the top plate portion 241 and the corrugated fin 246, and the corrugated fin 246 and the bottom plate portion 245, respectively. In the present embodiment, as shown in FIG. 17, the top plate portion 241 and the bottom plate portion 245 include base material layers 241A and 245A and bonding layers 241B and 245B made of a material having a lower melting point than the base material layers 241A and 245A. The top plate portion 241 and the bottom plate portion 245 are disposed so that the bonding layers 241B and 245B face the corrugated fins 246 side. That is, the base material layer 241A of the top plate portion 241 is configured to be in contact with the metal layer 213.
In the present embodiment, the base material layers 241A and 245A are made of an A3003 alloy, and the bonding layers 241B and 245B are made of an A4045 alloy.

As shown in FIG. 13, at the bonding interface 230 between the ceramic substrate 211, the circuit layer 212 (metal plate 222), and the metal layer 213 (metal plate 223), the circuit layer 212 (metal plate 222) and the metal layer 213. Ag is dissolved in (metal plate 223).
More specifically, a concentration gradient layer 233 is formed in the vicinity of the bonding interface 230 between the circuit layer 212 and the metal layer 213 so that the Ag concentration gradually decreases as the distance from the bonding interface 230 in the stacking direction increases. Here, the Ag concentration in the vicinity of the bonding interface 230 between the circuit layer 212 and the metal layer 213 is set within a range of 0.05 mass% or more and 10 mass% or less.
The Ag concentration in the vicinity of the bonding interface 230 between the circuit layer 212 and the metal layer 213 is an average value measured at 5 points from the bonding interface 230 by EPMA analysis (spot diameter of 30 μm). Further, the graph of FIG. 13 is obtained by performing line analysis in the stacking direction in the central portion of the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223), and obtaining the above-mentioned concentration at the 50 μm position as a reference. It is.

Further, when the bonding interface 230 between the ceramic substrate 211 and the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223) is observed with a transmission electron microscope, as shown in FIG. An Ag high concentration portion 232 in which Ag is concentrated is formed. In the Ag high concentration portion 232, the Ag concentration is set to be twice or more the Ag concentration in the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223). Note that the thickness H of the Ag high concentration portion 232 is set to 4 nm or less.
Further, in the Ag high concentration portion 232, the oxygen concentration is set higher than the oxygen concentration in the ceramic substrate 211.

Note that, as shown in FIG. 14, the bonding interface 230 observed here is a lattice image of the interface side edge of the lattice image of the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223) and the ceramic substrate 211. The reference plane S is the center between the end of the bonding interface side. Further, the Ag concentration in the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223) is a fixed distance from the bonding interface 230 in the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223). This is the Ag concentration at a distant portion (in this embodiment, 5 nm or more).
The oxygen concentration in the ceramic substrate 211 is the oxygen concentration in the crystal grains in a portion of the ceramic substrate 211 that is away from the bonding interface 230 by a certain distance (5 nm or more in this embodiment).

  The mass ratio of Al, Si, Ag, O, and N when the bonding interface 230 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Si: Ag: O: N = 15 to 45 mass. %: 15 to 45 mass%: 1 to 30 mass%: 1 to 10 mass%: 25 mass% or less. In addition, the spot diameter at the time of performing the analysis by EDS is 1 to 4 nm, the bonding interface 230 is measured at a plurality of points (for example, 20 points in the present embodiment), and the average value is calculated. Further, the bonding interface 230 between the crystal grain boundaries of the metal plates 222 and 223 constituting the circuit layer 212 and the metal layer 213 and the ceramic substrate 211 is not measured, and the metal plate 222 constituting the circuit layer 212 and the metal layer 213. Only the bonding interface 230 between the crystal grains 223 and the ceramic substrate 211 is set as a measurement target.

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

(Ag paste application process S201)
First, as shown in FIG. 16, Ag paste is applied to one surface and the other surface of the ceramic substrate 211 by slot die or ink jet printing to form Ag paste layers 224a and 225a. The thickness of the Ag paste layers 224a and 225a is about 0.02 to 200 μm after drying.
Here, the Ag paste used contains Ag powder, a solvent, and a dispersant, and the content of the Ag powder is 60% by mass or more and 90% by mass or less of the entire Ag paste. The balance is a solvent and a dispersant. In the present embodiment, the content of the Ag powder is 85% by mass of the entire Ag paste.
In the present embodiment, the viscosity of the Ag paste is adjusted to 10 Pa · s to 500 Pa · s, more preferably 50 Pa · s to 300 Pa · s.

The Ag powder has a particle size of 0.02 μm or more and 0.04 μm or less. In this embodiment, an Ag powder having an average particle size of 0.03 μm was used.
As the solvent, those having a boiling point of 200 ° C. or more are suitable, and for example, α-terpineol, butyl carbitol acetate, diethylene glycol dibutyl ether and the like can be applied. In the present embodiment, diethylene glycol dibutyl ether is used.
In this embodiment, a dicarboxylic acid-based dispersant is added. In addition, you may comprise Ag paste, without adding a dispersing agent.

(Ag paste firing step S202)
Next, the ceramic substrate 211 on which the Ag paste layers 224a and 225a are formed is heated to 150 to 200 ° C. in an air atmosphere to form Ag fired layers 224 and 225. In the present embodiment, the Ag fired layers 224 and 225 are Ag fixing layers.

(Lamination process S203)
Next, the metal plate 222 is laminated on one surface side of the ceramic substrate 211, and the metal plate 223 is laminated on the other surface side of the ceramic substrate 211.

(Heating step S204)
Next, the metal plate 222, the ceramic substrate 211, and the metal plate 223 are charged in the stacking direction (pressure 1 to 35 kgf / cm ² ) and placed in a vacuum heating furnace to be heated, and the Ag fired layers 224 and 225 are heated. Is diffused toward the metal plates 222 and 223 to form a molten metal region at the interface between the metal plates 222 and 223 and the ceramic substrate 211.
Here, in this embodiment, the pressure in the vacuum heating furnace is set in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, and the heating temperature is set in the range of 600 ° C. to 650 ° C.

(Coagulation step S205)
Next, the temperature is kept constant in a state where the molten metal region is formed, and Ag in the molten metal region is further diffused toward the metal plates 222 and 223. Then, the Ag concentration in the portion that was the molten metal region gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. That is, the ceramic substrate 211 and the metal plates 222 and 223 are bonded 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 power module substrate 210 is produced.

(Heat sink lamination step S206)
Next, the top plate portion 241, the corrugated fins 246, and the bottom plate portion 245 constituting the heat sink 240 are laminated on the other surface side of the metal layer 213 of the power module substrate 210. At this time, an Ag fixing layer 226 is interposed between the metal layer 213 and the top plate portion 241. In the present embodiment, the Ag fixing layer 226 is formed on the other surface of the metal layer 213 by sputtering, plating, or screen printing Ag paste.
Further, the top plate portion 241 and the bottom plate portion 245 are laminated so that the bonding layer 241B of the top plate portion 241 and the bonding layer 245B of the bottom plate portion 245 face the corrugated fin 246 side.

(Heat sink heating step S207)
Next, the laminated power module substrate 210, the top plate portion 241, the corrugated fins 246, and the bottom plate portion 245 are charged in the lamination direction (pressure 1 to 35 kgf / cm ² ) and charged into the atmosphere heating furnace. Then, Ag of the Ag fixing layer 226 is diffused toward the metal plate 223 and the top plate portion 241, and a molten metal region is formed between the metal layer 213 and the top plate portion 241 of the heat sink 240. At the same time, the bonding layers 241B and 245B are also melted between the top plate portion 241 and the corrugated fins 246 and between the bottom plate portion 245 and the corrugated fins 246 to form a molten metal region.
Here, in this embodiment, the inside of the atmosphere heating furnace is a nitrogen gas atmosphere, and the heating temperature is set in a range of 550 ° C. or more and 630 ° C. or less.

(Molten metal solidification step S208)
And by cooling, the metal layer 213 and the top-plate part 241 are joined by solidifying the molten metal area | region formed between the metal layer 213 and the top-plate part 241 of the heat sink 240. FIG. Further, by solidifying the molten metal region formed between the top plate portion 241 and the corrugated fins 246, and between the bottom plate portion 245 and the corrugated fins 246, the top plate portion 241 and the corrugated fins 246, the bottom plate portion 245 and the corrugated fins 246, Are joined.

  In this manner, the top plate portion 241, the corrugated fins 246, and the bottom plate portion 245 are brazed to form the heat sink 240, and the heat sink 240 and the power module substrate 210 are joined to each other for the power module with a heat sink. A substrate will be manufactured.

  In the power module substrate 210 and the power module 201 according to the present embodiment configured as described above, the ceramic substrate 211, the circuit layer 212 (metal plate 222), and the metal layer 213 (metal plate 223) are ceramics. A molten metal region is formed by diffusing Ag of the Ag fired layers 224 and 225 formed on one surface and the other surface of the substrate 211 toward the metal plates 222 and 223, and Ag in the molten metal region is Since the bonding is performed by further diffusing and solidifying the metal plates 222 and 223, the ceramic substrate 211 and the metal plates 222 and 223 are firmly bonded even when bonded under relatively low temperature and short time bonding conditions. It becomes possible.

In the present embodiment, the ceramic substrate 211 is made of Si ₃ N ₄ , and Ag is concentrated on the bonding interface 230 between the metal plates 222 and 223 that become the circuit layer 212 and the metal layer 213 and the ceramic substrate 211. Since the Ag high concentration portion 232 is formed, and the Ag concentration of the Ag high concentration portion 232 is set to be twice or more the Ag concentration in the circuit layer 212 and the metal layer 213, Ag atoms present in the vicinity of the interface As a result, the bonding strength between the ceramic substrate 211 and the metal plates 222 and 223 can be improved. Moreover, since the thickness of this Ag high concentration part 232 is 4 nm or less, it is suppressed that a crack generate | occur | produces in the Ag high concentration part 232 by the stress at the time of applying a heat cycle.

  Furthermore, in this embodiment, the mass ratio of Al, Si, Ag, O, and N obtained by analyzing the bonding interface 230 by the energy dispersive X-ray analysis method is Al: Si: Ag: O: N = 15 to 45 mass%. 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less, and a reaction product of Al and Ag is excessively generated at the bonding interface 230 to inhibit the bonding. In addition, the effect of improving the bonding strength by Ag atoms can be sufficiently achieved. Further, it is possible to prevent a portion having a high oxygen concentration from being thick at the bonding interface 230, and to suppress generation of cracks when a thermal cycle is loaded.

In the present embodiment, the Ag fired layers 224 and 225 obtained by firing the Ag paste layers 224a and 225a are used as Ag fixing layers, so that Ag is reliably interposed between the ceramic substrate 211 and the metal plates 222 and 223. Can do. In addition, since this Ag paste does not oxidize even when heated and fired in an air atmosphere, the Ag fired layers 224 and 225 can be formed relatively easily.
In addition, in this embodiment, Ag particles having a particle size of 0.02 μm or more and 0.04 μm or less are used, and an Ag paste containing no resin is used. Therefore, the Ag paste layers 224a and 225a are fired at a low temperature of 200 ° C. Thus, the Ag fired layers 224 and 225 can be formed.

Next, a fourth embodiment of the present invention will be described with reference to FIGS.
A power module 301 shown in FIG. 18 includes a power module substrate 310 on which a circuit layer 312 is disposed, a semiconductor chip 3 bonded to the surface of the circuit layer 312 via a solder layer 2, and a heat sink 340. Yes. Here, the solder layer 2 is made of, for example, a Sn—Ag, Sn—In, or Sn—Ag—Cu solder material. In this embodiment, a Ni plating layer (not shown) is provided between the circuit layer 312 and the solder layer 2.

The power module substrate 310 includes a ceramic substrate 311, a circuit layer 312 disposed on one surface of the ceramic substrate 311 (upper surface in FIG. 18), and the other surface (lower surface in FIG. 18) of the ceramic substrate 311. The metal layer 313 is provided.
The ceramic substrate 311 prevents electrical connection between the circuit layer 312 and the metal layer 313, and is made of highly insulating AlN (aluminum nitride). Further, the thickness of the ceramic substrate 311 is set in a range of 0.2 to 1.5 mm, and in this embodiment, is set to 0.635 mm.

The circuit layer 312 is formed by bonding a first metal plate 322 having conductivity to one surface of the ceramic substrate 311.
The metal layer 313 is formed by bonding the second metal plate 323 to the other surface of the ceramic substrate 311.
In the present embodiment, the first metal plate 322 and the second metal plate 323 are aluminum (so-called 4N aluminum) rolled plates having a purity of 99.99% or more.

  The heat sink 340 is for cooling the power module substrate 310 described above, and a top plate portion 341 joined to the power module substrate 310 and a flow path 342 for circulating a cooling medium (for example, cooling water). And. The heat sink 340 (top plate portion 341) is preferably made of a material having good thermal conductivity, and in this embodiment, is made of A6063 (aluminum alloy).

As shown in FIG. 19, Ag is fixed to the metal layer 313 (second metal plate 323) and the heat sink 340 at the bonding interface 330 between the second metal plate 323 (metal layer 313) and the heat sink 340. It is melted.
More specifically, concentration gradient layers 333 and 334 are formed in the vicinity of the bonding interface 330 between the metal layer 313 and the heat sink 340 and the Ag concentration gradually decreases as the distance from the bonding interface 330 in the stacking direction increases. Here, the Ag concentration in the vicinity of the bonding interface 330 between the metal layer 313 and the heat sink 340 is set within a range of 0.05 mass% or more and 10 mass% or less.

  Note that the Ag concentration in the vicinity of the bonding interface 330 between the metal layer 313 and the heat sink 340 is an average value measured at five points from the bonding interface 330 by a EPMA analysis (spot diameter of 30 μm). Further, the graph of FIG. 19 was obtained by performing line analysis in the stacking direction at the width center portion of the metal layer 313 (metal plate 323) and the heat sink 340 (top plate portion 341), and obtaining the above-described concentration at the 50 μm position as a reference. Is.

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

(Ag layer forming step S301 / adhering step S311)
First, as shown in FIG. 21, Ag is fixed to one surface of the first metal plate 322 to be the circuit layer 312 by sputtering to form the first Ag layer 324 and the second metal plate to be the metal layer 313. Ag is fixed to one surface of the H.323 by sputtering to form a second Ag layer 325 (fixing step S311).
Further, Ag is fixed to the other surface of the second metal plate 323 to be the metal layer 313 by sputtering to form an Ag layer 326 (Ag layer forming step S301).
Here, in this embodiment, the Ag amount in the first Ag layer 324, the second Ag layer 325, and the Ag layer 326 is set to 0.01 mg / cm ² or more and 10 mg / cm ² or less.

(Heat Sink Laminating Step S302 / Ceramic Substrate Laminating Step S312)
Next, as shown in FIG. 21, the first metal plate 322 is laminated on one surface side of the ceramic substrate 311, and the second metal plate 323 is laminated on the other surface side of the ceramic substrate 311 ( Ceramic substrate lamination step S312). At this time, as shown in FIG. 21, the first Ag plate 322 of the first metal plate 322 and the second Ag layer 325 of the second metal plate 323 are formed so that the surfaces thereof face the ceramic substrate 311. A metal plate 322 and a second metal plate 323 are stacked.
Further, the heat sink 340 is laminated on the other surface side of the second metal plate 323 (heat sink lamination step S302). At this time, as shown in FIG. 21, the second metal plate 323 and the heat sink 340 are laminated so that the surface of the second metal plate 323 on which the Ag layer 326 is formed faces the heat sink 340.
That is, the first Ag layer 324 is interposed between the first metal plate 322 and the ceramic substrate 311, the second Ag layer 325 is interposed between the second metal plate 323 and the ceramic substrate 311, and the second metal An Ag layer 326 is interposed between the plate 323 and the heat sink 340.

(Heat sink heating step S303 / ceramics substrate heating step S313)
Next, the first metal plate 322, the ceramic substrate 311, the second metal plate 323, and the heat sink 340 are charged in the stacking direction (pressure 1 to 35 kgf / cm ² ) in a vacuum heating furnace. Heat. The first molten metal region 327 is formed at the interface between the first metal plate 322 and the ceramic substrate 311 by diffusing Ag of the first Ag layer 324 toward the first metal plate 322. Also, the second molten metal region 328 is formed at the interface between the second metal plate 323 and the ceramic substrate 311 by diffusing Ag of the second Ag layer 325 toward the second metal plate 323 (heating the ceramic substrate). Step S313).
At the same time, a molten metal region 329 is formed between the second metal plate 323 and the heat sink 340 (heat sink heating step S303). As shown in FIG. 22, the molten metal region 329 is formed in the vicinity of the Ag layer 326 of the second metal plate 323 and the heat sink 340 as Ag of the Ag layer 326 diffuses toward the second metal plate 323 and the heat sink 340. This is formed by increasing the Ag concentration and lowering the melting point.
Here, in this embodiment, the pressure in the vacuum heating furnace is set in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, and the heating temperature is set in the range of 600 ° C. to 650 ° C.

(Molten metal solidification step S304 / first molten metal and second molten metal solidification step S314)
Next, the temperature is kept constant with the molten metal region 329 formed. Then, Ag in the molten metal region 329 further diffuses toward the second metal plate 323 and the heat sink 340. As a result, the Ag concentration in the portion that was the molten metal region 329 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. That is, the heat sink 340 and the second metal plate 323 are bonded by so-called diffusion bonding (Transient Liquid Phase Diffusion Bonding).

  Similarly, Ag in the first molten metal region 327 further diffuses toward the first metal plate 322. Further, Ag in the second molten metal region 328 further diffuses toward the second metal plate 323. Then, the Ag concentration in the portions of the first molten metal region 327 and the second molten metal region 328 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. Will go. Thereby, the ceramic substrate 311 and the first metal plate 322, and the ceramic substrate 311 and the second metal plate 323 are joined. That is, the ceramic substrate 311, the first metal plate 322, and the second metal plate 323 are joined by so-called diffusion bonding (Transient Liquid Phase Diffusion Bonding). After solidification progresses in this way, cooling is performed to room temperature.

  As described above, the first metal plate 322 to be the circuit layer 312 and the ceramic substrate 311 are joined, the second metal plate 323 to be the metal layer 313 and the ceramic substrate 311 are joined, and the second The metal plate 323 and the heat sink 340 are joined together, and the power module substrate with a heat sink according to this embodiment is manufactured.

  In the present embodiment configured as described above, an Ag layer forming step S301 for forming an Ag layer 326 between the second metal plate 323 to be the metal layer 313 and the heat sink 340 is provided. Ag is present at the bonding interface 330 between the second metal plate 323 and the heat sink 340. Since Ag is an element that lowers the melting point of aluminum, the molten metal region 329 can be formed at the interface between the heat sink 340 and the second metal plate 323 under a relatively low temperature condition. Therefore, the heat sink 340 and the second metal plate 323 can be firmly bonded even when bonded under relatively low temperature and short time bonding conditions.

  Further, in the present embodiment, since the first metal plate 322 and the ceramic substrate 311 and the second metal plate 323 and the ceramic substrate 311 are provided with the fixing step S311 for fixing Ag to the bonding surface S311. Ag is also present at the bonding interface between one metal plate 322 and the ceramic substrate 311 and at the bonding interface between the second metal plate 323 and the ceramic substrate 311, and the ceramic substrate 311, the first metal plate 322, and the ceramic substrate 311. And the second metal plate 323 can be firmly bonded.

  Furthermore, in the heat sink heating step S303, the molten metal region 329 is formed by diffusing Ag of the Ag layer 326 formed on the bonding surface of the second metal plate 323 toward the second metal plate 323 and the heat sink 340. In the molten metal solidification step S304, Ag in the molten metal region 329 is further solidified by being diffused toward the second metal plate 323 and the heat sink 340, so that the heat sink 340 and the second metal plate 323 (metal layer 313) are solidified. ) Can be firmly bonded to the heat sink 340 and the second metal plate 323 even when bonded under relatively low temperature and short time bonding conditions.

  In the present embodiment, the ceramic substrate 311, the first metal plate 322 (circuit layer 312), and the second metal plate 323 (metal layer 313) are also subjected to the first metal plate 322 in the ceramic substrate heating step S 313. The first molten metal is formed by diffusing Ag of the first Ag layer 324 and the second Ag layer 325 formed on the joint surface of the second metal plate 323 toward the first metal plate 322 and the second metal plate 323. The region 327 and the second molten metal region 328 are formed, and in the first molten metal and second molten metal solidification step S314, Ag in the first molten metal region 327 and the second molten metal region 328 is further converted into the first metal plate. The ceramic substrate 311, the first metal plate 322 (circuit layer 312), and the second metal plate are solidified by diffusing toward the second metal plate 323. 23 (metal layer 313) is bonded to the ceramic substrate 311, the first metal plate 322 (circuit layer 312), and the second metal even when bonded under relatively low temperature and short time bonding conditions. It is possible to firmly join the plate 323 (metal layer 313).

  Furthermore, brazing material foil is not used for joining the heat sink 340 and the second metal plate 323 and joining the ceramic substrate 311 to the first metal plate 322 and the second metal plate 323. It is not necessary to perform the alignment operation of the material foil, and the heat sink 340 and the second metal plate 323, the ceramic substrate 311, the first metal plate 322, and the second metal plate 323 can be reliably bonded. it can. Therefore, the power module substrate with a heat sink according to the present embodiment can be produced efficiently at low cost.

  In the present embodiment, the ceramic substrate 311 is bonded to the first metal plate 322 and the second metal plate 323, and the second metal plate 323 and the heat sink 340 are bonded at the same time. Thus, the cost required for the joining can be greatly reduced. Further, since it is not necessary to repeatedly heat and cool the ceramic substrate 311, the warpage of the power module substrate with a heat sink can be reduced, and a high-quality power module substrate with a heat sink can be produced. Can do.

  Further, the Ag layer forming step S301 is configured to form the Ag layer 326 by adhering Ag to the joint surface of the second metal plate 323 by sputtering, so that the Ag layer 326 is formed between the heat sink 340 and the second metal plate 323. Ag can be reliably interposed. In addition, the amount of Ag adhered can be adjusted with high accuracy, the molten metal region 329 can be formed reliably, and the heat sink 340 and the second metal plate 323 can be firmly bonded.

  Further, in the power module substrate with a heat sink according to the present embodiment, the second metal plate 323 (metal layer 313) and the heat sink at the bonding interface 330 between the heat sink 340 and the second metal plate 323 (metal layer 313). Ag is dissolved in 340, and the Ag concentration on the bonding interface 330 side of each of the second metal plate 323 (metal layer 313) and the heat sink 340 is in the range of 0.05 mass% or more and 10 mass% or less. Therefore, the portion of the second metal plate 323 (metal layer 313) and the heat sink 340 on the bonding interface 330 side is solid-solution strengthened, and cracks in the second metal plate 323 (metal layer 313) and the heat sink 340 are generated. Occurrence can be prevented. Therefore, a highly reliable power module substrate with a heat sink can be provided.

Next, a fifth embodiment of the present invention will be described with reference to FIGS.
The power module 401 includes a power module substrate 410 on which a circuit layer 412 is disposed, a semiconductor chip 3 bonded to the surface of the circuit layer 412 via a solder layer 2, and a heat sink 440.

  The power module substrate 410 includes a ceramic substrate 411, a circuit layer 412 disposed on one surface of the ceramic substrate 411 (upper surface in FIG. 23), and the other surface (lower surface in FIG. 23) of the ceramic substrate 411. And a disposed metal layer 413. The ceramic substrate 411 is made of highly insulating AlN (aluminum nitride).

The circuit layer 412 is formed by joining a first metal plate 422 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to a ceramic substrate 411.
The metal layer 413 is formed by bonding a second metal plate 423 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99% or more to the ceramic substrate 411.

  The heat sink 440 is for cooling the power module substrate 410 described above. The heat sink 440 according to the present embodiment includes a top plate portion 441 joined to the power module substrate 410, a bottom plate portion 445 disposed so as to face the top plate portion 441, and the top plate portion 441 and the bottom plate portion 445. A corrugated fin 446 interposed between the top plate portion 441, the bottom plate portion 445, and the corrugated fin 446 defines a flow path 442 through which a cooling medium flows.

  Here, the heat sink 440 is configured by brazing the top plate portion 441 and the corrugated fin 446, and the corrugated fin 446 and the bottom plate portion 445, respectively. In this embodiment, as shown in FIG. 26, the bottom plate portion 445 is configured by a laminated aluminum plate in which a base material layer 445A and a bonding layer 445B made of a material having a melting point lower than that of the base material layer 445A are laminated. . In the present embodiment, the base material layer 445A is made of an A3003 alloy, and the bonding layer 445B is made of an A4045 alloy.

At the joining interface between the top plate portion 441 of the heat sink 440 and the second metal plate 423 (metal layer 413), Ag is dissolved in the second metal plate 423 (metal layer 413) and the top plate portion 441. ing.
Further, Ag is dissolved in the bonding interface between the first metal plate 422 (circuit layer 412) and the ceramic substrate 411 and the bonding interface between the first metal plate 423 (metal layer 413) and the ceramic substrate 411. is doing.

  Below, the manufacturing method of the board | substrate for power modules with a heat sink of the above-mentioned structure is demonstrated.

(Fixed layer forming step S401)
First, as shown in FIG. 25, Ag is fixed to one surface of the first metal plate 422 to be the circuit layer 412 by sputtering to form the first Ag layer 424, and the second metal plate to be the metal layer 413 is formed. A second Ag layer 425 is formed on one surface of 423 by fixing Ag by sputtering. Further, Ag is fixed to the other surface of the second metal plate 423 by sputtering to form an Ag layer 426.
Here, in this embodiment, the Ag amount in the first Ag layer 424, the second Ag layer 425, and the Ag layer 426 is set to 0.01 mg / cm ² or more and 10 mg / cm ² or less.

(Lamination process S402)
Next, as shown in FIG. 25, the first metal plate 422 is laminated on one surface side of the ceramic substrate 411, and the second metal plate 423 is laminated on the other surface side of the ceramic substrate 411. At this time, as shown in FIG. 25, the first Ag plate 422 of the first metal plate 422 and the second Ag layer 425 of the second metal plate 423 are formed so that the surface of the first metal plate 422 faces the ceramic substrate 411. A metal plate 422 and a second metal plate 423 are stacked.
Further, the top plate portion 441 is laminated on the surface side of the second metal plate 423 where the Ag layer 426 is formed.

(Heating step S403)
Next, the first metal plate 422, the ceramic substrate 411, the second metal plate 423, and the top plate portion 441 are pressed in the stacking direction (pressure 1 to 35 kgf / cm ² ) and installed in the vacuum heating furnace. And heat. The first molten metal region 427 is formed at the interface between the first metal plate 422 and the ceramic substrate 411 by diffusing Ag of the first Ag layer 424 toward the first metal plate 422. The second molten metal region 428 is formed at the interface between the second metal plate 423 and the ceramic substrate 411 by diffusing Ag of the second Ag layer 425 toward the second metal plate 423.
Further, the molten metal region 429 is formed between the second metal plate 423 and the top plate portion 441 by diffusing Ag of the Ag layer 426 toward the second metal plate 423 and the top plate portion 441. .
Here, in this embodiment, the pressure in the vacuum heating furnace is set in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, and the heating temperature is set in the range of 600 ° C. to 650 ° C.

(Molten metal solidification step S404)
Next, the temperature is kept constant with the first molten metal region 427 and the second molten metal region 428 formed. Then, Ag in the first molten metal region 427 diffuses toward the first metal plate 422, and Ag in the second molten metal region 428 diffuses toward the second metal plate 423. Become. As a result, the Ag concentration in the portions of the first molten metal region 427 and the second molten metal region 428 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. To go. As a result, the ceramic substrate 411 is bonded to the first metal plate 422 and the second metal plate 423.
Further, the temperature is kept constant with the molten metal region 429 formed. Then, Ag in the molten metal region 429 diffuses toward the second metal plate 423 and the top plate portion 441. As a result, the Ag concentration in the portion that was the molten metal region 429 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. Thereby, the 2nd metal plate 423 and the top-plate part 441 are joined.

(Fin laminating step S405)
Next, as shown in FIG. 26, brazing material foil 447 (for example, low melting point aluminum alloy foil such as Al-10% Si alloy foil), corrugated fin 446, bottom plate portion on the other surface side of top plate portion 441. 445 are stacked. At this time, the bottom plate portion 445 is laminated so that the bonding layer 445B of the bottom plate portion 445 faces the corrugated fin 446 side. Further, for example, a flux (not shown) whose main component is KAlF ₄ is interposed between the top plate portion 441 and the corrugated fins 446 and between the bottom plate portion 445 and the corrugated fins 446.

(Brazing process S406)
Next, in a state where the top plate portion 441, the corrugated fins 446, and the bottom plate portion 445 are pressurized in the stacking direction (pressure 1 to 35 kgf / cm ² ), the top plate portion 441 is charged and heated in an atmosphere heating furnace. And a corrugated fin 446, and between the bottom plate portion 445 and the corrugated fin 446, a molten metal layer is formed by melting the brazing material foil 447 and the bonding layer 445B.
Here, in this embodiment, the inside of the atmosphere heating furnace is a nitrogen gas atmosphere, and the heating temperature is set in a range of 550 ° C. or more and 630 ° C. or less.
Then, by cooling, the molten metal layer formed between the top plate portion 441 and the corrugated fin 446 and between the bottom plate portion 445 and the corrugated fin 446 is solidified, and the top plate portion 441 and the corrugated fin 446, and the bottom plate portion 445 and the corrugated The fin 446 is brazed. At this time, oxide films are formed on the surfaces of the top plate portion 441, the corrugated fins 446, and the bottom plate portion 445, but these oxide films are removed by the aforementioned flux.

  Thus, the power module substrate with a heat sink according to the present embodiment is manufactured.

  In the manufacturing method of the power module substrate with a heat sink and the power module substrate with a heat sink according to the present embodiment configured as described above, the top plate portion 441 of the heat sink 440 and the second metal plate 423 (metal layer 413). ) And a diffusion of the Ag to form a molten metal region 429, and further diffuse the Ag in the molten metal region 429, and the top plate portion 441 of the heat sink 440 and the power module substrate. 410 is bonded, it is possible to reliably bond the top plate portion 441 of the heat sink 440 and the power module substrate 410 even under relatively low temperature conditions.

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) Or an aluminum alloy.

Moreover, in 1st Embodiment, although it demonstrated as what was set as the structure which fixes Ge in addition to Ag on the joint surface of a metal plate, it is not limited to this, Additive elements other than Ge (Zn, Mg) , Ca, Ga and Li) may be fixed, or these additional elements may not be fixed.
Furthermore, in the first embodiment, it has been described that Ag and Ge are fixed by sputtering. However, the present invention is not limited to this. Ink in which plating, vapor deposition, CVD, cold spray, or powder is dispersed is used. Ag or an additive element may be fixed by application such as.

  Further, in the fixing step, Al may be fixed together with Ag and additive elements. In particular, when an oxidation active element such as Mg, Ca, Li or the like is used as an additive element, it is possible to prevent oxidation of these elements by fixing together with Al.

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.
In the third embodiment of the present invention, the power module substrate and the heat sink may be bonded simultaneously.

  Furthermore, as shown in FIG. 27, the metal layer 513 may have a structure in which a plurality of metal plates 513A and 513B are stacked. In this case, the metal plate 513A located on one side (upper side in FIG. 27) of the metal layer 513 is bonded to the ceramic substrate 511, and the metal plate 513B located on the other side (lower side in FIG. 27) is the top of the heat sink 540. It will be joined to the plate part 541. Then, by forming an Ag layer between the metal plate 513B located on the other side and the top plate portion 541 of the heat sink 540, the metal plate 513B located on the other side and the top plate portion 541 of the heat sink 540 are joined. -ing Here, you may comprise the metal layer 513 by joining laminated | stacked metal plate 513A, 513B through an Ag layer. In FIG. 27, two metal plates 513A and 513B are stacked, but the number of stacked layers is not limited. Moreover, the metal plates to be stacked may have different sizes and shapes, or may be adjusted to the same size and shape. Furthermore, the composition of these metal plates may be different.

A comparative experiment conducted to confirm the effectiveness of the present invention will be described.
A power module substrate is fabricated by bonding a circuit layer made of 4N aluminum having a thickness of 0.6 mm and a metal layer made of 4N aluminum having a thickness of 0.6 mm to a ceramic substrate made of AlN having a thickness of 0.635 mm. did.
Here, on the joint surface of the aluminum plate (4N aluminum) to be the circuit layer and the metal layer, Ag and an additive element are fixed to form a fixed layer, and the metal plate and the ceramic substrate are laminated and heated under pressure (temperature). : 650 ° C., pressure: 4 kgf / cm ² , time: 30 minutes), and the metal plate and the ceramic substrate were joined.

Various test pieces in which the adhered Ag and the additive element were changed were produced, and the Ag concentration and the concentration of the additive element in the vicinity of the joint interface (position of 50 μm from the joint interface) were analyzed by EPMA. Moreover, the joining reliability was evaluated using these test pieces. As an evaluation of the bonding reliability, the bonding rates after 2000 times of the thermal cycle (−45 ° C.-125 ° C.) were compared. The 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

In Comparative Example 1 in which the adhesion amount of Ag was 11 mg / cm ² , the Ag concentration in the vicinity of the bonding interface exceeded 10% by mass, and the bonding after the cooling cycle (−45 ° C. to 125 ° C.) was repeated 2000 times The rate was 67.7%. This is presumably because the amount of Ag is large and the metal plate becomes too hard, and thermal stress due to the thermal cycle is applied to the joint interface.
Further, in Comparative Example 2 in which the Ag fixing amount was 0.009 mg / cm ² , the Ag concentration in the vicinity of the bonding interface was less than 0.05 mass%, and the cooling cycle (−45 ° C. to 125 ° C.) was 2000 times. The joining rate after the repetition was 60.1%. This is considered to be because the amount of Ag present at the interface is small and a molten metal region could not be sufficiently formed at the interface between the metal plate and the ceramic substrate.

  On the other hand, in Invention Example 1-36, the Ag concentration in the vicinity of the bonding interface or the total of the Ag concentration and the concentration of the additive element is 0.05% by mass or more and 10% by mass or less. The joining rate after 2000 times (-45 ° C.-125 ° C.) was 70% or more. The diffusion of various additive elements makes it possible to reliably form a molten metal region at the interface between the metal plate and the ceramic substrate, and it is determined that the metal plate and the ceramic substrate can be firmly bonded.

1 Power module 3 Semiconductor chip (electronic component)
10, 110, 210, 310, 410, 510 Power module substrate 11, 111, 211, 311, 411, 511 Ceramic substrate 12, 112, 212, 312, 412, 512 Circuit layer 13, 113, 213, Metal layer 22 , 122, 222, 322, 422 Metal plate (first metal plate)
23, 123, 223, 323, 423 Metal plate (second metal plate)
24, 25, 124, 125, 324, 325, 424, 425 Adhering layer 26, 27 Molten metal region 30, 130, 230 Bonding interface

Claims (23)

A power module substrate in which a metal plate made of aluminum or an aluminum alloy is laminated and bonded to the surface of a ceramic substrate,
Ag is dissolved in the metal plate, and the Ag concentration in the vicinity of the interface with the ceramic substrate in the metal plate is set within a range of 0.05% by mass or more and 10% by mass or less. Characteristic power module substrate.   In addition to Ag, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li are solid-solved in the metal plate, and the ceramic substrate of the metal plate 2. The power module substrate according to claim 1, wherein the sum of the Ag concentration and the concentration of the additive element in the vicinity of the interface is set in a range of 0.05% by mass or more and 10% by mass or less. The ceramic substrate is made of AlN or Si ₃ N ₄ , and the oxygen concentration at the bonding interface between the metal plate and the ceramic substrate is an oxygen concentration more than twice the oxygen concentration in the crystal grains of the ceramic substrate. The power module substrate according to claim 1, wherein a high concentration portion is formed, and the thickness of the oxygen high concentration portion is 4 nm or less.   The Ag high concentration portion in which the Ag concentration is set to be twice or more the Ag concentration in the metal plate is formed at the bonding interface between the metal plate and the ceramic substrate. Item 4. The power module substrate according to any one of Items 3 to 3. The ceramic substrate is made of AlN;
The mass ratio of Al, Ag, O, and N obtained by analyzing the bonding interface including the high concentration Ag portion by energy dispersive X-ray analysis is Al: Ag: O: N = 50 to 90% by mass: 1 to 30. The power module substrate according to claim 4, wherein the power module substrate has a mass% of 1 to 10 mass% and 25 mass% or less. The ceramic substrate is made of Si ₃ N ₄ ;
The mass ratio of Al, Si, Ag, O, and N obtained by analyzing the bonding interface including the high-concentration Ag portion by energy dispersive X-ray analysis is Al: Si: Ag: O: N = 15 to 45% by mass. The power module substrate according to claim 4, wherein the power module substrate is set to 15 to 45 mass%: 1 to 30 mass%: 1 to 10 mass%: 25 mass% or less. The ceramic substrate is made of Al ₂ O ₃ ;
The mass ratio of Al, Ag, and O obtained by analyzing the bonding interface including the high Ag concentration portion by energy dispersive X-ray analysis is Al: Ag: O = 50 to 90 mass%: 1 to 30 mass%: 45. The power module substrate according to claim 4, wherein the power module substrate has a mass% or less.   A power module substrate with a heat sink, comprising: the power module substrate according to any one of claims 1 to 7; and a heat sink that cools the power module substrate. A first metal plate made of aluminum or an aluminum alloy is bonded to one surface of the ceramic substrate, and a second metal plate made of aluminum or an aluminum alloy is bonded to the other surface of the ceramic substrate;
The heat sink is bonded to the surface of the second metal plate opposite to the bonding surface with the ceramic substrate,
Ag is dissolved in the second metal plate and the heat sink, and the Ag concentration in the vicinity of the interface between the second metal plate and the heat sink is in the range of 0.05 mass% to 10 mass%. The power module substrate with a heat sink according to claim 8, wherein the power module substrate is set.   In the second metal plate and the heat sink, in addition to Ag, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved, The Ag concentration in the vicinity of the interface between the second metal plate and the heat sink and the total concentration of the additive element are set in a range of 0.05% by mass or more and 10% by mass or less. Power module board with heat sink.   11. The power module substrate with a heat sink according to claim 9, wherein a thickness of the second metal plate is set to be larger than a thickness of the first metal plate. .   The substrate for a power module with a heat sink according to any one of claims 9 to 11, wherein the second metal plate is configured by laminating a plurality of metal plates.   A power module comprising: the power module substrate according to any one of claims 1 to 7; and an electronic component mounted on the power module substrate. A method for producing a power module substrate in which a metal plate made of aluminum or an aluminum alloy is laminated and bonded to the surface of a ceramic substrate,
A fixing step of fixing Ag to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate, and forming a fixing layer containing Ag;
A laminating step of laminating the ceramic substrate and the metal plate via the fixing 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 fixing step, Ag is interposed at the interface between the ceramic substrate and the metal plate within a range of 0.01 mg / cm ^{2 to} 10 mg / cm ² ,
In the heating step, the molten metal region is formed at the interface between the ceramic substrate and the metal plate by diffusing Ag toward the metal plate.   15. The power module according to claim 14, wherein in the fixing step, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are fixed in addition to Ag. Manufacturing method for industrial use.   16. The method for manufacturing a power module substrate according to claim 14, wherein Al is fixed together with Ag in the fixing step.   In the fixing step, Ag is applied to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate by plating, vapor deposition, CVD, sputtering, cold spray, or application of ink in which powder is dispersed. The method for manufacturing a power module substrate according to any one of claims 14 to 16, wherein the substrate is fixed.   17. The fixing step includes forming the fixing layer by applying an Ag paste to at least one of a bonding surface of the ceramic substrate and a bonding surface of the metal plate. A method for manufacturing a power module substrate according to claim 1. A first metal plate made of aluminum or an aluminum alloy is bonded to one surface of the ceramic substrate, and a second metal plate made of aluminum or an aluminum alloy is bonded to the other surface of the ceramic substrate. A method of manufacturing a power module substrate with a heat sink, wherein the heat sink is bonded to a surface opposite to a bonding surface with the ceramic substrate of the metal plate,
A ceramic substrate bonding step of bonding the ceramic substrate and the first metal plate, and the ceramic substrate and the second metal plate;
A heat sink joining step for joining the heat sink to one surface of the second metal plate,
The heat sink joining step includes
An Ag layer forming step in which Ag is fixed to at least one of the joining surface of the second metal plate and the joining surface of the heat sink; and
A heat sink laminating step of laminating the second metal plate and the heat sink via the Ag layer;
Heating and heating the laminated second metal plate and the heat sink in the laminating direction and forming a molten metal region at the interface between the second metal plate and the heat sink,
By solidifying the molten metal region, the molten metal solidifying step for joining the second metal plate and the heat sink,
In the heat sink heating step, the molten metal region is formed at an interface between the second metal plate and the heat sink by diffusing Ag of the Ag layer toward the second metal plate and the heat sink. A method for manufacturing a power module substrate with a heat sink.   The method for manufacturing a power module substrate with a heat sink according to claim 19, wherein the ceramic substrate bonding step and the heat sink bonding step are performed simultaneously.   21. The method for manufacturing a power module substrate with a heat sink according to claim 19 or 20, wherein the second metal plate is configured by laminating a plurality of metal plates.   The Ag layer forming step includes plating, vapor deposition, CVD, sputtering, cold spray, or application of paste or ink in which powder is dispersed, of the bonding surface of the heat sink and the bonding surface of the second metal plate. The method for manufacturing a power module substrate with a heat sink according to any one of claims 19 to 21, wherein Ag is fixed to at least one of the two.   The method for manufacturing a power module substrate with a heat sink according to any one of claims 19 to 22, wherein Al is fixed together with Ag in the Ag layer forming step.