JP2011238892A - 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 comprising a metal plate and a ceramic substrate which are surely bonded and having high heat cycle reliability, a substrate with a heat sink for a power module, a power module including the substrate for a power module and a method for producing the substrate for a power module, and a method for producing a substrate with a heat sink for a power module.SOLUTION: A substrate 10 for a power module includes metal plates 12 and 13 that comprise aluminum or an aluminum alloy and are laminated on and bonded to a surface of a ceramic substrate 11. One or more additional elements selected from among Zn, Ge, Mg, Ca, Ga and Li are solid-dissolved in the metal plates 12 and 13. The total concentration of the additional elements in the vicinity of the interface with the ceramic substrate 11 in the metal plates 12 and 13 is set within a range of 0.01 mass% or more to 5 mass% or less.

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. A substrate in which 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 in the metal plate The total concentration of the additive elements in the vicinity of the interface is set in the range of 0.01% by mass to 5% by mass.

In the power module substrate having this configuration, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li are dissolved in the metal plate. The joint interface side portion is strengthened by solid solution. Thereby, the fracture | rupture in a metal plate part can be prevented and joining reliability can be improved.
Here, since the total concentration of the additive elements in the vicinity of the interface with the ceramic substrate of the metal plate is 0.01% by mass or more, the solid-solution strengthening is performed on the bonding interface side portion of the metal plate. be able to. Moreover, since the total concentration of the additive elements in the vicinity of the interface with the ceramic substrate of the metal plate is 5% by mass or less, it is possible to prevent the strength of the bonding interface of the metal plate from becoming excessively high, When a cooling cycle is applied to the power module substrate, the thermal stress can be absorbed by the metal plate, and cracking of the ceramic substrate can be prevented.

Here, 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 higher than the oxygen concentration in the metal plate and the ceramic substrate. The oxygen high concentration portion may be formed, and the thickness of the oxygen high concentration portion may be 4 nm or less.
In this case, an oxygen high concentration portion in which the oxygen concentration is higher than the oxygen concentration in the metal plate and 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.
Note that the oxygen concentration in the metal plate and the ceramic substrate is an oxygen concentration in a portion of the metal plate and the ceramic substrate that is away from the bonding interface by a certain distance (for example, 5 nm or more).

In addition, an additive element high concentration portion in which the concentration of the additive element is at least twice the concentration of the additive element in the metal plate is formed at the bonding interface between the metal plate and the ceramic substrate. Is preferred.
In this case, since the additive element high concentration portion in which the concentration of the additive element is at least twice the concentration of the additive element in the metal plate is formed at the bonding interface between the ceramic substrate and the metal plate. The additive element atoms present in the vicinity can improve the bonding strength between the ceramic substrate and the metal plate.
The concentration of the additive element in the metal plate is the concentration of the additive element in a portion of the metal plate that is away from the bonding interface by a certain distance (for example, 5 nm or more).

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

  When the mass ratio of the additive element atoms present at the bonding interface exceeds 30% by mass, a reaction product of Al and the additive element 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 the additive element atoms is less than 1% by mass, there is a possibility that the junction strength due to the additive element atoms cannot be sufficiently improved. Therefore, the mass ratio of additive element 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 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 configuration, 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 In the heat sink, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved, and the second metal plate and the heat sink near the interface The total concentration of the additive elements is preferably set within a range of 0.01% by mass to 5% by mass.

According to the power module substrate with a heat sink having this configuration, the second metal plate and the heat sink each include one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li. Since they are in solid solution, the respective joining interface side portions of the second metal plate and the heat sink are strengthened by solid solution.
Since the total concentration of the additive elements in the vicinity of the bonding interface between the second metal plate and the heat sink is 0.01% by mass or more, the bonding interface side portion between the second metal plate and the heat sink Can be solid solution strengthened. In addition, since the total concentration of the additive elements in the vicinity of the bonding interface between the second metal plate and the heat sink is 5% by mass or less, the strength of the bonding interface between the second metal plate and the heat sink is excessive. And the thermal strain can be absorbed by the second metal plate.

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, whereby 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 And one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are fixed to at least one of the joint surfaces of the metal plate, and a fixing layer containing the additive element is provided. A fixing step of forming, a stacking step of stacking the ceramic substrate and the metal plate via the fixing layer, and pressing and heating the stacked ceramic substrate and the metal plate in a stacking direction; and A heating step of forming a molten metal region at the interface with the metal plate and solidifying the molten metal region It includes a coagulation step of bonding the mix substrate and the metal plate, and in the fixing step, the interface between the ceramic substrate and the metal plate, said additional element, 0.01 mg / cm ² or more 10 mg / cm is interposed within the range of ² or less, in the heating step, by the additive element to diffuse toward the metal plate, the interface between the ceramic substrate and the metal plate, to form the molten metal area It is a feature.

According to the method for manufacturing a power module substrate having this configuration, at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate is selected from Zn, Ge, Mg, Ca, Ga, and Li. Alternatively, since a fixing step of fixing two or more kinds of additional elements and forming a fixing layer containing the additional elements is provided, the bonding interface between the metal plate and the ceramic substrate has Zn, Ge, Mg, Ca. One or two or more additive elements selected from, Ga and Li are present. Here, since elements such as Zn, Ge, Mg, Ca, Ga, and Li are elements that lower the melting point of aluminum, a molten metal region is formed at the interface between the metal plate and the ceramic substrate even under relatively low temperature conditions. Can be formed.
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.

  In the heating step, the ceramic substrate and the metal plate are diffused by diffusing one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li toward the metal plate. By forming the molten metal region at the interface and solidifying the molten metal region, it is configured to join the metal plate and the ceramic substrate, so there is no need to use a brazing material foil or the like, at a low cost, A power module substrate in which a metal plate and a ceramic substrate are securely bonded can be manufactured.

  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 amount of fixing of the additive element interposed at the interface between the ceramic substrate and the metal plate is 0.01 mg / cm ² or more, it is melted at the interface between the ceramic substrate and the metal plate. The metal region can be reliably formed, and the ceramic substrate and the metal plate can be firmly bonded.
Furthermore, since the fixed amount of the additive element interposed at the interface between the ceramic substrate and the metal plate is 10 mg / cm ² or less, it is possible to prevent the occurrence of cracks in the fixed layer, A molten metal region can be reliably formed at the interface with the metal plate. Furthermore, it is possible to prevent the additive element from excessively diffusing toward the metal plate and excessively increasing the strength of the metal plate near the interface. 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.

Furthermore, in the fixing step, the additive element is interposed in the interface between the ceramic substrate and the metal plate within a range of 0.01 mg / cm ² or more and 10 mg / cm ² or less. Among them, a power module substrate in which the total concentration of the additive elements in the vicinity of the interface with the ceramic substrate is within a range of 0.01% by mass to 5% by mass 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.

The additive element is fixed directly to at least one of the ceramic substrate bonding surface and the metal plate bonding surface. From the viewpoint of productivity, the additive element is fixed to the metal plate bonding surface. It is preferable to make it.
The additive element may be fixed to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate to form a plurality of additive element layers.

Here, in the fixing step, it is preferable that Al is fixed together with the additive element.
In this case, since Al is fixed together with the additive element, the fixed layer to be formed 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. Moreover, oxidation of oxidation active elements, such as Mg, Ca, Li, can be prevented. In order to fix Al together with the additive element, the additive element and Al may be vapor-deposited simultaneously, or sputtering may be performed using an alloy of the additive element and Al as a target. Alternatively, Al and an additive element may be stacked.

Further, the fixing step may include at least one of a bonding surface of the ceramic substrate and a bonding surface of the metal plate by plating, vapor deposition, CVD, sputtering, cold spray, or application of paste and ink in which powder is dispersed. It is preferable to fix the additive element on one side.
In this case, the additive element is 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 paste and ink in which powder is dispersed. Since it is firmly fixed to one side, the additive element can be reliably interposed at the bonding interface between the ceramic substrate and the metal plate. In addition, the amount of the additive element fixed can be adjusted with high accuracy, and the molten metal region can be reliably formed, and the ceramic substrate and the metal plate can be firmly bonded.
In addition, when using the paste containing the said additive element, 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. Further, the ceramic substrate and the metal plate are laminated in a state where the paste containing the additive element is applied, and when the laminated ceramic substrate and the metal plate are pressed and heated in the laminating direction, the addition is performed. It is good also as a structure which bakes the paste containing an element.

  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 additive element layer is formed by fixing one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li to at least one of the bonding surface of the heat sink and the bonding surface of the heat sink Element layer forming step, heat sink lamination step of laminating the second metal plate and the heat sink via the additive element layer, and pressing the laminated second metal plate and the heat sink in the laminating direction A heat sink heating step for forming a molten metal region at the interface between the second metal plate and the heat sink, and solidifying the molten metal region, thereby joining the second metal plate and the heat sink. A molten metal solidifying step, wherein in the heat sink heating step, the additive element of the additive element layer is added to the second metal plate and the heat sink. By diffusing toward the interface between the heat sink and the second metal plate, it is characterized by forming the molten metal region.

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 additional element layer forming step of fixing one or two or more additional elements selected from Zn, Ge, Mg, Ca, Ga and Li to form an additional element layer is provided. An additive element is present at the bonding interface between the metal plate and the heat sink. Since this additive element 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, the molten metal region is formed at the interface between the heat sink and the second metal plate by diffusing the additive element in the additive element layer toward the second metal plate and the heat sink. By solidifying the region, the second metal plate and the heat sink are joined together, so there is no need to use an Al-Si brazing foil that is difficult to manufacture, and the second A power module substrate with a heat sink in which the metal plate and the heat sink are securely bonded can be manufactured.
Further, since the additive element 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 is performed. There is no need to do etc.
Moreover, when the additive element is directly fixed to the joint surface of the heat sink and the joint 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 second metal plate 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 thermal strain caused by the difference in thermal expansion coefficient between the heat sink and the ceramic substrate is reduced with this second metal plate. It can be sufficiently relaxed and the occurrence of cracks in the ceramic substrate can be suppressed.

In addition, the additional element layer forming step includes plating, vapor deposition, CVD, sputtering, cold spraying, or bonding of the heat sink bonding surface and the second metal plate by application of paste or ink in which powder is dispersed. It is preferable to fix the additive element on at least one of the surfaces.
In this case, the additive element is selected from 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 is securely fixed to at least one, it is possible to reliably interpose the additive element at the bonding interface between the heat sink and the second metal plate. In addition, the amount of the additive element fixed can be adjusted with high accuracy, the molten metal region can be reliably formed, and the heat sink and the second metal plate can be firmly bonded.

Further, in the additive element layer forming step, it is preferable to fix Al together with the additive element.
In this case, since Al is fixed together with the additive element, the additive element layer to be formed contains Al, and in the heat sink heating process, the additive element layer is preferentially melted to form a molten metal region. It becomes possible to form reliably, and a heat sink and a 2nd metal plate can be joined firmly. Moreover, oxidation of oxidation active elements, such as Mg, Ca, Li, can be prevented. In order to fix Al together with the additive element, the additive element and Al may be vapor-deposited simultaneously, or sputtering may be performed using an alloy of the additive element and Al as a target. Alternatively, Al and an additive element may be stacked.

  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 the concentration distribution of the addition element of the circuit layer and metal layer of the board | substrate for power modules which is the 1st Embodiment of this invention. It is a schematic diagram 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 the concentration distribution of the addition element 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 the concentration distribution of the addition element 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 the metal layer of the board | substrate for power modules with a heat sink which is the 4th Embodiment of this invention, and the concentration distribution of the addition element of a heat sink. It is a flowchart 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 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 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 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. 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 concentration of the additive element gradually decreases as the distance from the bonding interface 30 in the stacking direction increases. Here, the total concentration of the additive elements in the vicinity of the bonding interface 30 between the circuit layer 12 and the metal layer 13 is set within a range of 0.01% by mass to 5% by mass.
Here, in the present embodiment, Ge is used as an additive element, 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 0.01 mass% or more and 5 mass% or less.

  The concentration of the additive element in the vicinity of the bonding interface 30 between the circuit layer 12 and the metal layer 13 is an average value measured at five points from the bonding interface 30 by an EPMA analysis (spot diameter of 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.

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 additive element high concentration portion 32 in which the additive element (Ge) is concentrated is formed. In the additive element high concentration portion 32, the additive element concentration (Ge concentration) is twice the additive element concentration (Ge concentration) in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). That's it. The thickness H of the additive element high concentration portion 32 is 4 nm or less.
Further, in the high concentration portion 32 of the additive element, 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 center between the interface side end of the reference surface S is defined as a reference plane S. The concentration (Ge concentration) of the additive element in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) is the same as that of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). Of these, it is the concentration (Ge concentration) of the additive element in a portion away from the bonding interface 30 by a certain distance (in this embodiment, 5 nm or more).
The oxygen concentration in the ceramic substrate 11 is the oxygen concentration in the crystal grains in a portion of the ceramic substrate 11 that is away from the bonding interface 30 by a certain distance (5 nm or more in this embodiment).

  The mass ratio of Al, additive element (Ge), O, and N when this bonding interface 30 is analyzed by energy dispersive X-ray analysis (EDS) is Al: additive element (Ge): O: N = It is set in the range of 50 to 90% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% 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 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 more additives selected from Zn, Ge, Mg, Ca, Ga and Li are added to the respective joint surfaces of the metal plates 22 and 23 by sputtering. The elements are fixed to form the fixing layers 24 and 25.
Here, in the present embodiment, Ge is used as an additive element, and the additive element amount (Ge amount) in the fixed layers 24 and 25 is set to 0.01 mg / cm ² or more and 10 mg / cm ² or less.

(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 (additive element: 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 are formed by the diffusion of the additive element (Ge) of the fixing layers 24 and 25 toward the metal plates 22 and 23. , 25 is formed by increasing the concentration of the additive element (Ge concentration) in the vicinity of 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, the additive element (Ge) in the molten metal regions 26 and 27 is further diffused toward the metal plates 22 and 23. As a result, the concentration of the additive element (Ge concentration) in the portions that were the molten metal regions 26 and 27 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. Will go. 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, the power module 1, and the power module substrate manufacturing method according to the present embodiment configured as described above, an additive element (Ge) is fixed to the joint surfaces of the metal plates 22 and 23. Since the fixing step S01 is provided, the additive element (Ge) is interposed in the bonding interface 30 between the metal plates 22 and 23 and the ceramic substrate 11. Here, since Ge is an element that lowers the melting point of aluminum, the molten metal regions 26 and 27 can be formed at the interface between the metal plates 22 and 23 and the ceramic substrate 11 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 24 containing the additive element (Ge) formed on the joining surfaces of the metal plates 22 and 23. , 25 are diffused toward the metal plates 22 and 23 to form the molten metal regions 26 and 27, and the additive element (Ge) in the molten metal regions 26 and 27 is diffused into the metal plate 22. The ceramic substrate 11 and the metal plates 22 and 23 can be firmly bonded even when bonded under relatively low temperature and short time bonding conditions. It becomes.

Further, 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), the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) are connected to each other. The additive element is in solid solution, and the total concentration of the additive element on the bonding interface 30 side of each of the circuit layer 12 and the metal layer 13 is set within a range of 0.01% by mass to 5% by mass. In this embodiment, Ge is used as an additive element, and the Ge concentration in the vicinity of the junction interface 30 between the circuit layer 12 and the metal layer 13 is set within a range of 0.01 mass% to 5 mass%. Therefore, the portion of the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) on the bonding interface 30 side is solid-solution strengthened, and the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23) Can prevent the occurrence of cracks .
In addition, the additive element (Ge) is sufficiently diffused toward the metal plates 22 and 23 in the heating step S03, and the metal plates 22 and 23 and the ceramic substrate 11 are firmly bonded.

  In the present embodiment, the ceramic substrate 11 is made of AlN, and the additive element (Ge) 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 additive element high concentration portion 32 is formed, and the concentration (Ge concentration) of the additive element in the additive element high concentration portion 32 is in the circuit layer 12 (metal plate 22) and the metal layer 13 (metal plate 23). Since the concentration of the additive element (Ge concentration) is twice or more, the additive element atom (Ge atom) existing in the vicinity of the interface can improve the bonding strength between the ceramic substrate and the metal plate. . Further, since the thickness of the high concentration portion 32 of additive element is 4 nm or less, the generation of cracks in the high concentration portion 32 of additive element due to stress when a thermal cycle is applied is suppressed.

  Furthermore, in this embodiment, the mass ratio of Al, additive element (Ge), O, and N obtained by analyzing the bonding interface 30 by the energy dispersive X-ray analysis method is Al: additive element (Ge): O: N = 50. ~ 90% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less, so that it is possible to prevent the additive element from being excessively present at the bonding interface 30 and inhibiting the bonding, The effect of improving the bonding strength by the additive element atoms (Ge 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 30 and to suppress generation of cracks when a thermal cycle is loaded.

  In addition, a fixing step S01 for fixing the additive element (Ge) to the bonding surface of the metal plate to form the fixing layers 24 and 25 is provided. In the heating step S03, the additive element (Ge) of the fixing layers 24 and 25 is added. Since the molten metal regions 26 and 27 are formed at the interface between the ceramic substrate 11 and the metal plates 22 and 23 by diffusing toward the metal plates 22 and 23, it is difficult to manufacture an Al—Si type solder. There is no need to use a 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.

In the present embodiment, since the Ge amount interposed at the interface between the ceramic substrate 11 and the metal plates 22 and 23 is 0.01 mg / cm ² or more in the fixing step S01, the ceramic substrate 11 and the metal plate 22, It is possible to reliably form the molten metal regions 26 and 27 at the interface between the ceramic substrate 11 and the ceramic substrate 11 and the metal plates 22 and 23.

Furthermore, since the amount of Ge interposed at the interface between the ceramic substrate 11 and the metal plates 22 and 23 is 10 mg / cm ² or less, it is possible to prevent cracks from occurring in the fixing layers 24 and 25, and the ceramic substrate The molten metal regions 26 and 27 can be reliably formed at the interface between the metal plate 11 and the metal plates 22 and 23. Further, it is possible to prevent the additive element (Ge) from excessively diffusing toward the metal plates 22 and 23 and excessively increasing the strength of the metal plates 22 and 23 in the vicinity of the interface. Therefore, when the cooling cycle is applied to the power module substrate 10, the thermal stress can be absorbed by the circuit layer 12 and the metal layer 13 (metal plates 22 and 23), and cracking of the ceramic substrate 11 can be prevented. .

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. One or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li are 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 concentration of the added element gradually decreases as the distance from the bonding interface 130 in the stacking direction increases. Here, the concentration of the additive element in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 is set within a range of 0.01% by mass to 5% by mass.
Here, in this embodiment, Mg is used as an additive element, and the Mg concentration in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 is set to 0.01 mass% or more and 5 mass% or less.

  The concentration of the additive element in the vicinity of the bonding interface 130 between the circuit layer 112 and the metal layer 113 is an average value measured at 5 points from the bonding interface 130 by EPMA analysis (spot diameter 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 additive element high concentration portion 132 in which the additive element (Mg) is concentrated is formed. In the additive element high concentration portion 132, the additive element concentration (Mg concentration) is twice the additive element concentration (Mg concentration) in the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123). That's it. The thickness H of the additive element 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 center between the interface side end of the reference plane is defined as a reference plane S. The concentration (Mg concentration) of the additive element in the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123) is the same as the circuit layer 112 (metal plate 122) and the metal layer 113 (metal plate 123). This is the concentration (Mg concentration) of the additive element in a portion away from the bonding interface 130 by a certain distance (5 nm in this embodiment).

  The mass ratio of Al, additive element (Mg), and O when this bonding interface 130 is analyzed by energy dispersive X-ray analysis (EDS) is Al: additive element (Mg): O = 50 to 90 mass. %: 1 to 30% by mass: 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 FIGS.

(Fixing step S101)
First, as shown in FIG. 11, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are fixed to one surface and the other surface of the ceramic substrate 111 by vapor deposition. Then, the fixing layers 124 and 125 are formed.
Here, in this embodiment, Mg is used as an additive element, and the amount of additive element (Mg amount) in the fixing layers 124 and 125 is set to 0.01 mg / cm ² or more and 10 mg / cm ² or less.

(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, Mg in the fixing 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 the additive element (Mg) in the molten metal region is further diffused toward the metal plates 122 and 123. Then, the additive element concentration (Mg concentration) of 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 manufacturing method of the power module substrate 110 and the power module 101 and the power module substrate 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 ( The metal plate 123) forms a molten metal region by diffusing Mg of the fixing layers 124 and 125 formed on one surface and the other surface of the ceramic substrate 111 toward the metal plates 122 and 123. Since the Mg in the molten metal region is further diffused and solidified in the metal plates 122 and 123, the ceramic substrate 111 and the metal plate 122, even if bonded under relatively low temperature and short time bonding conditions. 123 can be firmly bonded to each other.

  In addition, at the bonding interface 130 between the ceramic substrate 111 and the circuit layer 112 and the metal layer 113, the additive element (Mg) is dissolved in the circuit layer 112 and the metal layer 113, and the circuit layer 112 and the metal layer 113 respectively. Since the additive element concentration (Mg concentration) on the bonding interface 130 side is set within a range of 0.01 mass% or more and 5 mass% or less, the bonding interface 130 side portion of the circuit layer 112 and the metal layer 113 is fixed. The melt strengthening can prevent cracks in the circuit layer 112 and the metal layer 113.

In the present embodiment, the ceramic substrate 111 is made of Al ₂ O ₃ , and an additive element (Mg) is added to the bonding interface 130 between the metal plates 122 and 123 to be the circuit layer 112 and the metal layer 113 and the ceramic substrate 111. ) Is formed, and the additive element concentration (Mg concentration) of the additive element high concentration portion 132 is equal to the additive element concentration (Mg concentration) in the circuit layer 112 and the metal layer 113. Since it is set to be twice or more, it is possible to improve the bonding strength between the ceramic substrate 111 and the metal plates 122 and 123 by the additive element atoms (Mg atoms) existing in the vicinity of the interface. In addition, since the thickness of the high concentration portion 132 of additive element is 4 nm or less, the generation of cracks in the high concentration portion 132 of additive element due to stress when a thermal cycle is applied is suppressed.

  Furthermore, in the present embodiment, the mass ratio of Al, additive element (Mg), and O analyzed by energy dispersive X-ray analysis of the bonding interface 130 is Al: additive element (Mg): O = 50 to 90 mass%. : 1 to 30% by mass: 45% by mass or less, so that it is possible to prevent the reaction between Al and the additive element (Mg) from being excessively generated at the bonding interface 130 and hinder the bonding, and added. The effect of improving the bonding strength by element atoms (Mg atoms) can be sufficiently achieved.

  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. One or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li are dissolved in (metal plate 223).
More specifically, a concentration gradient layer 233 is formed in the vicinity of the junction interface 230 between the circuit layer 212 and the metal layer 213 so that the concentration of the additive element gradually decreases as the distance from the junction interface 230 in the stacking direction increases. Here, the concentration of the additive element in the vicinity of the bonding interface 230 between the circuit layer 212 and the metal layer 213 is set in a range of 0.01% by mass to 5% by mass.
Here, in this embodiment, Zn is used as an additive element, and the Zn concentration in the vicinity of the junction interface 230 between the circuit layer 212 and the metal layer 213 is set to 0.01 mass% or more and 5 mass% or less.

  Note that the concentration of the additive element in the vicinity of the bonding interface 230 between the circuit layer 212 and the metal layer 213 is an average value measured at five 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 additive element high concentration portion 232 in which the additive element (Zn) is concentrated is formed. In the additive element high concentration portion 232, the additive element concentration (Zn concentration) is more than twice the additive element concentration (Zn concentration) in the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223). Has been. The thickness H of the additive element high concentration portion 232 is 4 nm or less.
Further, in the additive element 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 center between the interface side end of the reference surface S is defined as a reference plane S. Further, the additive element concentration (Zn concentration) in the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223) is the junction of the circuit layer 212 (metal plate 222) and the metal layer 213 (metal plate 223). This is the additive element concentration (Zn concentration) at a part away from the interface 230 by a certain distance (5 nm in this embodiment).
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 in this embodiment).

  The mass ratio of Al, Si, additive element (Zn), O, and N when the bonding interface 230 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Si: additive element (Zn): O: N = 15 to 45% by mass: 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% 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 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.

(Plating step S201)
First, as shown in FIG. 16, plating layers 224 and 225 containing an additive element (Zn) are formed on the surfaces of the metal plates 222 and 223, respectively. In addition, the thickness of this plating layer 224,225 is set in the range of 1 micrometer-5 micrometers. In the present embodiment, the plating layers 224 and 225 serve as fixed layers for the additive elements.

(Lamination process S202)
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. At this time, the metal plates 222 and 223 are arranged so that the plating layers 224 and 225 face the ceramic substrate 211 side, respectively.

(Heating step S203)
Next, in a state where the metal plate 222, the ceramic substrate 211, and the metal plate 223 are pressed in the stacking direction (pressure 1 to 35 kgf / cm ² ), they are placed in a vacuum heating furnace and heated. By diffusing the additive element (Zn) toward the metal plates 222 and 223, a molten metal region is formed 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 S204)
Next, the temperature is kept constant in a state where the molten metal region is formed, and the additive element (Zn) in the molten metal region is further diffused toward the metal plates 222 and 223. Then, the concentration (Zn concentration) of the additive element in 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 S205)
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, a fixed layer 226 containing an additive element (Zn) is interposed between the metal layer 213 and the top plate portion 241. In the present embodiment, the fixing layer 226 is formed by performing sputtering or plating on the other surface of the metal layer 213.
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 S206)
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, the molten metal region is formed between the metal layer 213 and the top plate portion 241 of the heat sink 240 by diffusing the additive element (Zn) of the fixed layer 226 toward the metal layer 213 and the top plate portion 241. Form. 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 S207)
Then, by cooling, a molten metal region formed between the metal layer 213 and the top plate portion 241 of the heat sink 240, a molten metal formed between the top plate portion 241 and the corrugated fin 246, and between the bottom plate portion 245 and the corrugated fin 246. By solidifying the region, the metal layer 213 and the top plate portion 241, the top plate portion 241 and the corrugated fin 246, and the bottom plate portion 245 and the corrugated fin 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 made of metal. A molten metal region is formed by diffusing the additive element (Zn) of the plating layers 224 and 225 formed on the plates 222 and 223 toward the metal plates 222 and 223, and the additive element (Zn) in the molten metal region is formed. Is bonded to the metal plates 222 and 223 by further diffusing and solidifying them, so that 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 to do.

In this embodiment, the ceramic substrate 211 is made of Si ₃ N ₄ , and an additive element (Zn) is added to the bonding interface 230 between the metal plates 222 and 223 to be the circuit layer 212 and the metal layer 213 and the ceramic substrate 211. ) Is formed, and the additive element concentration (Zn concentration) of the additive element high concentration portion 232 is equal to the additive element concentration (Zn concentration) in the circuit layer 212 and the metal layer 213. Since it is set to be twice or more, it is possible to improve the bonding strength between the ceramic substrate 211 and the metal plates 222 and 223 by the additive element atoms (Zn atoms) existing in the vicinity of the interface. In addition, since the thickness of the high concentration element portion 232 is 4 nm or less, the generation of cracks in the high concentration element portion 232 due to stress when a thermal cycle is applied is suppressed.

  Furthermore, in this embodiment, the mass ratio of Al, Si, additive element (Zn), O, and N obtained by analyzing the bonding interface 230 by the energy dispersive X-ray analysis method is Al: Si: additive element (Zn): O. : N = 15 to 45% by mass: 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less. Therefore, Al and an additive element (Zn) It is possible to prevent the reaction product from being excessively generated and hinder the bonding, and to sufficiently exert the effect of improving the bonding strength by the additive element atom (Zn atom). 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 this embodiment, since the plating layers 224 and 225 formed on the metal plates 222 and 223 are fixed layers, the additive element (Zn) is reliably interposed between the ceramic substrate 211 and the metal plates 222 and 223. be able to.

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, at the bonding interface 330 between the metal layer 313 (second metal plate 323) and the heat sink 340, Zn, Ge is added to the metal layer 313 (second metal plate 323) and the heat sink 340. , Mg, Ca, Ga, and Li are dissolved in one or more additive elements.
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. The concentration gradient layers 333 and 334 gradually decrease in addition element concentration as they are separated from the bonding interface 330 in the stacking direction. The additive element 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 0.01% by mass to 5% by mass.

Here, in this embodiment, Ge is used as an additive element, and the Ge concentration in the vicinity of the bonding interface 330 between the metal layer 313 and the heat sink 340 is set to 0.01 mass% or more and 5 mass% or less.
The concentration of the additive element in the vicinity of the bonding interface 330 between the metal layer 313 and the heat sink 340 is an average value measured at 50 points from the bonding interface 330 by EPMA analysis (spot diameter: 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.

(Additive element layer forming step S301 / adhering step S311)
First, as shown in FIG. 21, the first Ge layer 324 is formed by fixing Ge as an additive element to one surface of the first metal plate 322 to be the circuit layer 312 by sputtering, and the first metal layer 313 is formed. On one surface of the second metal plate 323, Ge is fixed by sputtering to form a second Ge layer 325 (fixing step S311).
Further, the Ge layer 326 is formed on the other surface of the second metal plate 323 to be the metal layer 313 by adhering Ge as an additive element by sputtering (additive element layer forming step S301).
Here, in this embodiment, the Ge amount in the first Ge layer 324, the second Ge layer 325, and the Ge layer 326 is set to 0.08 mg / cm ² or more and 2.7 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 Ge plate 322 of the first metal plate 322 and the surface of the second metal plate 323 on which the second Ge layer 325 is formed 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 Ge layer 326 is formed faces the heat sink 340.
That is, the first Ge layer 324 is interposed between the first metal plate 322 and the ceramic substrate 311, the second Ge layer 325 is interposed between the second metal plate 323 and the ceramic substrate 311, and the second metal A Ge 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 Ge of the first Ge layer 324 is diffused toward the first metal plate 322, thereby forming a first molten metal region 327 at the interface between the first metal plate 322 and the ceramic substrate 311. Further, the Ge of the second Ge layer 325 is diffused toward the second metal plate 323, thereby forming a second molten metal region 328 at the interface between the second metal plate 323 and the ceramic substrate 311 (ceramic substrate). Heating 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 Ge layer 326 of the second metal plate 323 and the heat sink 340 by diffusion of Ge of the Ge layer 326 toward the second metal plate 323 and the heat sink 340. This is formed by increasing the Ge 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, Ge in the molten metal region 329 further diffuses toward the second metal plate 323 and the heat sink 340. As a result, the Ge 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, Ge in the first molten metal region 327 further diffuses toward the first metal plate 322. Further, Ge in the second molten metal region 328 further diffuses toward the second metal plate 323. As a result, the Ge 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. It will follow. 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.

  The present embodiment configured as described above includes the Ge layer forming step S301 for forming the Ge layer 326 between the second metal plate 323 to be the metal layer 313 and the heat sink 340. Ge is present at the bonding interface 330 between the second metal plate 323 and the heat sink 340. Since Ge 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.

  In the present embodiment, since the bonding step S311 for fixing Ge to the bonding surface of the first metal plate 322 and the ceramic substrate 311 and the bonding surface of the second metal plate 323 and the ceramic substrate 311 is provided. Ge 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.

  Further, in the heat sink heating step S303, the molten metal region 329 is formed by diffusing Ge of the Ge 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, Ge in the molten metal region 329 is further solidified by diffusing toward the second metal plate 323 and the heat sink 340, and 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 Ge of the first Ge layer 324 and the second Ge 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, the Ge in the first molten metal region 327 and the second molten metal region 328 is further replaced with 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, since the Ge layer forming step S301 is configured to form the Ge layer 326 by fixing Ge to the joint surface of the second metal plate 323 by sputtering, the Ge layer forming step S301 is formed between the heat sink 340 and the second metal plate 323. It becomes possible to interpose Ge reliably. In addition, the amount of Ge adhered can be adjusted with high accuracy, and the molten metal region 329 can be reliably formed, 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). Ge as an additive element is dissolved in 340, and the Ge concentration on the bonding interface 330 side of each of the second metal plate 323 (metal layer 313) and the heat sink 340 is 0.01 mass% or more and 5 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 the second metal plate 323 (metal layer 313) and heat sink The generation of cracks at 340 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 bonding interface between the top plate portion 441 of the heat sink 440 and the second metal plate 423 (metal layer 413), the second metal plate 423 (metal layer 413) and the top plate portion 441 have Zn, Ge, Mg , Ca, Ga, and Li, one or more additive elements selected from a solid solution. In the present embodiment, Mg is dissolved as an additive element.
Further, at the bonding interface between the first metal plate 422 (circuit layer 412) and the ceramic substrate 411 and at the bonding interface between the first metal plate 423 (metal layer 413) and the ceramic substrate 411, Zn, Ge, One or more additive elements selected from Mg, Ca, Ga, and Li are in solid solution, and Mg is in solid solution in this embodiment.

  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, Mg is fixed to one surface of the first metal plate 422 to be the circuit layer 412 by sputtering to form the first Mg layer 424, and the second metal plate to be the metal layer 413 is formed. A second Mg layer 425 is formed on one surface of 423 by fixing Mg by sputtering. Further, Mg is fixed to the other surface of the second metal plate 423 by sputtering to form an Mg layer 426.
Here, in this embodiment, the amount of Mg in the first Mg layer 424, the second Mg layer 425, and the Mg 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 Mg plate 422 of the first metal plate 422 and the surface of the second metal plate 423 on which the second Mg layer 425 is formed face the ceramic substrate 411. A metal plate 422 and a second metal plate 423 are stacked.
Furthermore, the top plate portion 441 is laminated on the surface side of the second metal plate 423 where the Mg 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. As Mg in the first Mg layer 424 diffuses toward the first metal plate 422, a first molten metal region 427 is formed at the interface between the first metal plate 422 and the ceramic substrate 411. Mg in the second Mg layer 425 diffuses toward the second metal plate 423, thereby forming a second molten metal region 428 at the interface between the second metal plate 423 and the ceramic substrate 411. Furthermore, Mg in the Mg layer 426 diffuses toward the second metal plate 423 and the top plate portion 441, thereby forming a molten metal region 429 between 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. Mg in the first molten metal region 427 diffuses toward the first metal plate 422, and Mg in the second molten metal region 428 diffuses toward the second metal plate 423. Then, the Mg concentration in the portions that were the first molten metal region 427 and the second molten metal region 428 gradually decreased and the melting point increased, and solidification proceeded while maintaining the temperature constant. 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. Mg in the molten metal region 429 diffuses toward the second metal plate 423 and the top plate portion 441. Then, the Mg 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). The molten metal region 429 is formed by diffusing this Mg, and the Mg in the molten metal region 429 is further diffused, 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, although it demonstrated as what uses Ge, Mg, Zn as an additional element, it is not limited to this, One type or two or more types selected from Zn, Ge, Mg, Ca, Ga, and Li An additive element may be used.
Furthermore, although it demonstrated as what fixes an addition element by sputter | spatter, application | coating of a paste, and plating, it is not limited to this, By application | coating of vapor deposition, CVD, cold spray, or the ink in which the powder is disperse | distributed, The additive element may be fixed.

  Further, in the fixing step, Al may be fixed together with the additive element. 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 additive element 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. It has been done. Here, the metal layer 513 may be configured by joining the stacked metal plates 513A and 513B via an additive element 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, an additive element is fixed to a bonding surface of an aluminum plate (4N aluminum) to be a circuit layer and a metal layer to form a fixing layer, and the metal plate and the ceramic substrate are stacked and pressurized and heated (temperature: 650). C., pressure: 4 kgf / cm ² , time: 30 minutes), and the metal plate and the ceramic substrate were joined.

Then, various test pieces in which the adhering additive element was changed were produced, and the concentration of the additive element in the vicinity of the joining interface (position 50 μm from the joining interface) was 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 Tables 1 and 2. In addition, the joining rate was computed with the following formula | equation. Here, the initial bonding area is an area to be bonded before bonding.
Bonding rate = (initial bonding area-peeling area) / initial bonding area

In Comparative Example 1 in which the total amount of fixed elements added to the fixed layer was 10.35 mg / cm ² , the bonding rate after 2000 cycles of the thermal cycle (−45 ° C. to 125 ° C.) was 65.9%. there were. This is presumably because the amount of additive elements is large and the metal plate becomes too hard, and thermal stress due to the thermal cycle is applied to the joint interface.

In Comparative Example 2 where the fixed amount of the additive element in the fixed layer was 0.009 mg / cm ² , the joining rate after 2000 cycles of the cooling and heating cycle (−45 ° C. to 125 ° C.) was 59.8%. . This is considered to be because the amount of additive elements present at the interface is small and the molten metal region could not be sufficiently formed at the interface between the metal plate and the ceramic substrate.

  On the other hand, in Example 1-43 of this invention, all the joining rates after 2000 times of a cooling-heat cycle (-45 degreeC-125 degreeC) were 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 (19)

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,
In the metal plate, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga, and Li are dissolved, and in the vicinity of the interface between the metal plate and the ceramic substrate. The power module substrate, wherein the total concentration of the additive elements is set within a range of 0.01% by mass to 5% by mass. 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. 2. 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.   An additive element high concentration portion in which the concentration of the additive element is at least twice the concentration of the additive element in the metal plate is formed at the bonding interface between the metal plate and the ceramic substrate. The power module substrate according to claim 1 or 2. The ceramic substrate is made of AlN;
The mass ratio of Al, the additive element, and O, N analyzed by energy dispersive X-ray analysis of the joint interface including the high concentration part of the additive element is Al: additive element: O: N = 50 to 90 mass%. The power module substrate according to claim 3, wherein: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less. The ceramic substrate is made of Si ₃ N ₄ ;
The mass ratio of Al, Si, the additive element, and O and N obtained by analyzing the joint interface including the high concentration portion of the additive element by energy dispersive X-ray analysis is Al: Si: additive element: O: N = 15. The power module substrate according to claim 3, wherein the power module substrate is set to ˜45 mass%: 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, the additive element, and O obtained by analyzing the bonding interface including the high concentration portion of the additive element by energy dispersive X-ray analysis is Al: additive element: O = 50 to 90 mass%: 1 to 30. The power module substrate according to claim 3, wherein the mass percentage is 45% by mass or less.   A power module substrate with a heat sink, comprising: the power module substrate according to any one of claims 1 to 6; 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,
In the second metal plate and the heat sink, one or more additive elements selected from Zn, Ge, Mg, Ca, Ga and Li are dissolved, and the second metal plate and The power module substrate with a heat sink according to claim 7, wherein the total concentration of the additive elements in the vicinity of the interface of the heat sink is set in a range of 0.01% by mass or more and 5% by mass or less.   The power module substrate with a heat sink according to claim 8, wherein the thickness of the second metal plate is set to be larger than the thickness of the first metal plate.   The power module substrate with a heat sink according to claim 8 or 9, wherein the second metal plate is configured by laminating a plurality of metal plates.   A power module comprising: the power module substrate according to claim 1; 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,
One or more additional elements selected from Zn, Ge, Mg, Ca, Ga and Li are fixed to at least one of the bonding surface of the ceramic substrate and the bonding surface of the metal plate, and the additional element A fixing step of forming a fixing layer containing:
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, the additive element is interposed in the interface between the ceramic substrate and the metal plate within a range of 0.01 mg / cm ² or more and 10 mg / cm ² or less,
In the heating step, the molten metal region is formed at the interface between the ceramic substrate and the metal plate by diffusing the additive element toward the metal plate. Method.   13. The method for manufacturing a power module substrate according to claim 12, wherein in the fixing step, Al is fixed together with the additive element.   The fixing step may be performed on 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 a paste and ink in which powder is dispersed. The method for manufacturing a power module substrate according to claim 12 or 13, wherein the additive element is fixed. 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
One or more additional elements selected from Zn, Ge, Mg, Ca, Ga and Li are fixedly added to at least one of the bonding surface of the second metal plate and the bonding surface of the heat sink. An additive element layer forming step for forming an element layer;
A heat sink lamination step of laminating the second metal plate and the heat sink via the additive element 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 the interface between the second metal plate and the heat sink by diffusing the additive element of the additive element layer toward the second metal plate and the heat sink. A method of manufacturing a power module substrate with a heat sink, characterized by comprising:   The method for manufacturing a power module substrate with a heat sink according to claim 15, wherein the ceramic substrate bonding step and the heat sink bonding step are performed simultaneously.   The method of manufacturing a power module substrate with a heat sink according to claim 15 or 16, wherein the second metal plate is configured by laminating a plurality of metal plates.   The additive element layer forming step includes plating, vapor deposition, CVD, sputtering, cold spraying, or application of paste and ink in which powder is dispersed to form 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 15 to 17, wherein an additive element is fixed to at least one of them.   The method for manufacturing a power module substrate with a heat sink according to any one of claims 15 to 18, wherein in the additive element layer forming step, Al is fixed together with the additive element.

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