JP2012164709A - Manufacturing method for substrate for power module, and substrate for power module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for a substrate for a power module, that can efficiently produce a substrate for a power module with high strength of an interface between a ceramic substrate and an aluminum layer composed of aluminum or an aluminum alloy and with excellent reliability, and provide the substrate for the power module.SOLUTION: The manufacturing method for a substrate for a power module includes: a fixture step of fixing Ag to a region where at least an aluminum layer 12 is formed on one surface of a ceramic substrate 11 and forming a fixture layer 24 including Ag; a molten aluminum filling step of disposing the ceramic substrate 11 on which the fixture layer 24 is formed in a mold 50, filling the mold 50 with molten aluminum M, and bringing the ceramic substrate 11 and the molten aluminum M into contact with each other; and a solidification step of solidifying the molten aluminum M in a state of being in contact with the ceramic substrate 11.

Description

  The present invention relates to a method for manufacturing a power module substrate used in a semiconductor device that controls a large current and a high voltage, and a power module substrate.

  Among semiconductor elements, a power element for supplying power has a relatively high calorific value, and as a substrate on which the power element is mounted, for example, as shown in Patent Documents 1-4, highly insulating AlN (aluminum nitride). 2. Description of the Related Art A power module substrate that includes a ceramic substrate made of the like and a circuit layer formed on one surface of the ceramic substrate is widely used. Here, in patent documents 1-4, the above-mentioned circuit layer is formed by making molten aluminum contact one side of a ceramic substrate.

In such a power module substrate, a semiconductor element as a power element is mounted on a circuit layer via a solder layer and used as a power module.
In order to efficiently dissipate the heat generated from the power module, for example, as shown in Patent Document 1, a heat sink provided on the other surface side of the ceramic substrate has been proposed.

Japanese Patent Laid-Open No. 2002-075651 JP 2002-329814 A JP 2005-252136 A JP 2007-092150 A

By the way, in the above-mentioned power module, a heat cycle is loaded at the time of use. Then, thermal stress acts on the interface between the ceramic substrate and the circuit layer due to the difference in thermal expansion coefficient between the ceramic substrate and aluminum, and there is a possibility that peeling or the like occurs at the interface between the ceramic substrate and the circuit layer.
In particular, recently, power modules have become smaller and thinner, and the usage environment has become severe, and the amount of heat generated from semiconductor elements tends to increase. It is necessary to dispose a substrate. In this case, since the power module substrate is constrained by the heat sink, a large shearing force acts on the interface between the circuit layer and the ceramic substrate during a heat cycle load. Therefore, it has been necessary to improve the interfacial strength between the ceramic substrate and the circuit layer as compared with the prior art.

By the way, as described in Patent Documents 1-4, when the circuit layer is formed by bringing molten aluminum into direct contact with the surface of the ceramic substrate, peeling at the interface between the circuit layer and the ceramic substrate is prevented. Therefore, it is necessary to ensure a sufficient contact time between the molten aluminum and the ceramic substrate. In addition, it is necessary to set the pressure at the time of filling molten aluminum into the mold on which the ceramic substrate is disposed, and to bring the ceramic substrate and molten aluminum into contact with each other at a high pressure.
For this reason, when the contact time and filling pressure of molten aluminum fluctuate, the interface strength between the ceramic substrate and the circuit layer is lowered. Further, there is a problem that the power module substrate cannot be produced efficiently.

  The present invention has been made in view of the above-described circumstances, and can efficiently produce a power module substrate having high interfacial strength between a ceramic substrate and an aluminum layer made of aluminum or an aluminum alloy and excellent reliability. An object of the present invention is to provide a power module substrate manufacturing method and a power module substrate.

  In order to solve the above problems and achieve the above object, a method for manufacturing a power module substrate according to the present invention includes a power module in which an aluminum layer made of aluminum or an aluminum alloy is formed on one surface of a ceramic substrate. A method of manufacturing a substrate for use, comprising: fixing step of fixing Ag to at least a region of the ceramic substrate on which one of the aluminum layers is formed, and forming a fixing layer containing Ag; Placing the ceramic substrate with the layer formed in a mold, filling the mold with molten aluminum, and contacting the ceramic substrate with the molten aluminum; and in contact with the ceramic substrate A solidifying step for solidifying the molten aluminum. There.

  According to the method for manufacturing a power module substrate having this configuration, a fixing layer containing Ag is formed at least in a region where an aluminum layer is formed on one surface of the ceramic substrate, and molten aluminum is applied to the ceramic substrate. Since it is made to contact, in the area | region in which the adhering layer was formed among ceramic substrates, the reactivity with molten aluminum becomes high and reaction of a ceramic substrate and molten aluminum will be promoted. For this reason, even if the contact time between the molten aluminum and the ceramic substrate is shortened or the molten aluminum filling pressure is lowered, the interface strength between the ceramic substrate and the aluminum layer can be improved, and the reliability is excellent. It is possible to produce a power module substrate.

Here, it is preferable that the fixed amount of Ag in the fixing step is in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .
When the fixing amount of Ag in the fixing step is less than 0.1 mg / cm ² , the effect of promoting the reaction between the ceramic substrate and molten aluminum may not be sufficiently achieved. Further, if the amount of Ag fixed in the fixing step exceeds 20 mg / cm ² , an excessive reaction product of Ag and Al is generated at the interface between the ceramic substrate and the aluminum layer, and the interface strength is reduced. There is a fear. Therefore, it is preferable that the fixing amount of Ag in the fixing step is in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .

Further, in the fixing step, one or two or more additive elements selected from Mg, Ca and Ni may be fixed in addition to Ag.
Since elements such as Ag and Mg, Ca, and Ni are elements having high reactivity with aluminum, interfacial strength can be improved by interposing them at the interface between the ceramic substrate and the aluminum layer. When an active element such as Mg or Ca is fixed, the oxidation loss can be suppressed by fixing together with Al.

Here, it is preferable that the total amount of Ag and the additional element fixed in the fixing step be in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .
In the case where the total amount of Ag and the additive element fixed in the fixing step is less than 0.1 mg / cm ² , there is a possibility that the effect of promoting the reaction between the ceramic substrate and the molten aluminum cannot be sufficiently achieved. is there. Further, when the total amount of Ag and the additive element in the fixing step exceeds 20 mg / cm ² , the reaction product of Ag, the additive element, and Al is excessive at the interface between the ceramic substrate and the aluminum layer. It may generate | occur | produce and interface strength may fall. Therefore, it is preferable that the total amount of Ag and the additional element in the fixing step be in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .

In the fixing step, Ag is preferably fixed by plating, vapor deposition, CVD, sputtering, cold spray, or application of ink in which powder is dispersed.
In this case, Ag can be reliably fixed to one surface of the ceramic substrate. In addition, the amount of Ag adhered can be adjusted with high accuracy.

Furthermore, in the fixing step, it is preferable to form the fixing layer by applying an Ag paste.
In this case, a fixed layer containing Ag can be surely formed by applying and baking Ag paste. In addition, since Ag does not oxidize even when heated and fired in an air atmosphere, a fixed layer containing Ag can be easily formed. The Ag paste may be fired when the ceramic substrate is heated with the Ag paste applied.

A second aluminum layer made of aluminum or aluminum alloy may be formed on the other surface of the ceramic substrate.
In this case, a power module substrate is produced in which an aluminum layer is formed on one surface of the ceramic substrate and a second aluminum layer is formed on the other surface of the ceramic substrate. The second aluminum layer may be formed by bringing molten aluminum into contact with the other surface of the ceramic substrate in the same manner as the aluminum layer, or an aluminum plate may be joined by brazing or the like.

  The power module substrate of the present invention is a power module substrate manufactured by the above-described method for manufacturing a power module substrate, and in the aluminum layer, an Ag concentration at a position of 50 μm from the interface with the ceramic substrate, The concentration difference with the Ag concentration at a position of 100 μm from the interface with the ceramic substrate is 0.1% by mass or less, and the Ag concentration in the interface between the ceramic substrate and the aluminum layer is within the aluminum layer. It is characterized in that an Ag high concentration portion having an Ag concentration of 2 times or more is formed.

In the power module substrate having this configuration, an Ag high concentration portion in which the Ag concentration is twice or more the Ag concentration in the aluminum layer is formed at the interface between the ceramic substrate and the aluminum layer. The existing Ag atoms can improve the interface strength between the ceramic substrate and the aluminum layer.
The Ag concentration in the aluminum layer is the Ag concentration in a portion of the aluminum layer that is away from the interface by a certain distance (eg, 5 nm).

Here, when the ceramic substrate is composed of AlN, the mass ratio of Al, Ag, O, and N analyzed by energy dispersive X-ray analysis of the interface between the ceramic substrate and the aluminum layer is as follows: It is preferable that Al: Ag: O: N = 50 to 90% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less.
Further, when the ceramic substrate is made of Si ₃ N ₄ , Al, Si, Ag, O, and N of the interface between the ceramic substrate and the aluminum layer analyzed by an energy dispersive X-ray analysis method are used. The mass ratio is preferably Al: Si: Ag: O: N = 15 to 45 mass%: 15 to 45 mass%: 1 to 30 mass%: 1 to 10 mass%: 25 mass% or less.
Furthermore, when the ceramic substrate is made of Al ₂ O ₃ , the mass ratio of Al, Ag, and O obtained by analyzing the interface between the ceramic substrate and the aluminum layer by energy dispersive X-ray analysis is It is preferable that Al: Ag: O = 50 to 90% by mass: 1 to 30% by mass: 0 to 45% by mass.

  If the mass ratio of Ag atoms present at the interface with the aluminum layer of the ceramic substrate exceeds 30% by mass, a reaction product of Al and Ag will be generated excessively, and this reaction product may inhibit bonding. There is. On the other hand, if the mass ratio of Ag atoms is less than 1% by mass, there is a possibility that the interface strength due to Ag atoms cannot be sufficiently improved. Therefore, the mass ratio of Ag atoms at the interface between the ceramic substrate and the aluminum layer 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 interface, and the average value is calculated. In the measurement, the interface between the crystal grain boundary of the aluminum layer and the ceramic substrate is not measured, and only the interface between the crystal grain of the aluminum layer 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.

Moreover, in the board | substrate for power modules of this invention, it is good also as a structure which has the 2nd aluminum layer which consists of aluminum or an aluminum alloy in the other surface of the said ceramic substrate.
In this case, the aluminum layer is formed on one surface of the ceramic substrate, and the second aluminum layer is formed on the other surface of the ceramic substrate, and thus the warpage of the ceramic substrate is suppressed. In addition, for example, by arranging a semiconductor element using an aluminum layer as a circuit layer and arranging a heat sink on the second aluminum layer side, a power module including the heat sink can be configured.

  According to the present invention, a method for producing a power module substrate capable of efficiently producing a power module substrate having high interfacial strength between the ceramic substrate and an aluminum layer made of aluminum or an aluminum alloy and excellent in reliability, and A power module substrate can be provided.

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 a schematic diagram of the interface of the circuit layer of the board | substrate for power modules which is the 1st Embodiment of this invention, a metal layer, and a ceramic substrate. It is explanatory drawing which shows Ag density distribution of the circuit layer and metal layer of the board | substrate for power modules which is the 1st Embodiment of this invention. It is a flowchart of the manufacturing method of the board | substrate for power modules which is the 1st Embodiment of this invention. It is explanatory drawing of the manufacturing method of the board | substrate for power modules which is the 1st Embodiment of this invention. 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 a schematic diagram of the interface of the circuit layer and ceramic substrate of the board | substrate for power modules which are the 2nd Embodiment of this invention. It is explanatory drawing which shows Ag density distribution and Ca density | concentration distribution of the circuit layer of the board | substrate for power modules which is the 2nd Embodiment of this invention. It is a flowchart of 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 a schematic diagram of the interface of the circuit layer and ceramic substrate of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing which shows Ag density distribution of the circuit layer of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing which shows Ag density | concentration distribution of the metal layer of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is a flowchart of the manufacturing method of the board | substrate for power modules which is the 3rd Embodiment of this invention. It is explanatory drawing of the manufacturing method of the board | substrate for power modules which is the 3rd Embodiment of this invention. FIG. 17 is an enlarged explanatory view showing a bonding interface between the ceramic substrate and the metal layer in FIG. 16.

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a power module substrate 10 and a power module 1 according to a first embodiment of the present invention.
The power module 1 includes a power module substrate 10 on which a circuit layer 12 is disposed, a semiconductor element 3 bonded to the surface of the circuit layer 12 via a solder layer 2, and a heat sink 40. Here, the solder layer 2 is made of, for example, a Sn-Ag-based, Sn-In-based, or Sn-Ag-Ag-based 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.

The circuit layer 12 is formed by bringing one surface of the ceramic substrate 11 into contact with solid aluminum made of aluminum or an aluminum alloy and solidifying it.
The metal layer 13 is formed by contacting and solidifying molten aluminum made of aluminum or an aluminum alloy on the other surface of the ceramic substrate 11.
In the present embodiment, the circuit layer 12 and the metal layer 13 are made of aluminum (so-called 4N aluminum) having a purity of 99.99% by mass or more.

  The heat sink 40 is for cooling the power module substrate 10 described above, and includes a top plate portion 41 joined to the power module substrate 10 and a flow path 42 for circulating a cooling medium (for example, cooling water). It has. The heat sink 40 (top plate portion 41) is preferably made of a material having good thermal conductivity, and is made of A6063 (aluminum alloy) in the present embodiment.

  When the interface 30 between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13 is observed with a transmission electron microscope, an Ag high concentration portion 32 in which Ag is concentrated is formed at the interface 30 as shown in FIG. Has been. In the Ag high concentration portion 32, the Ag concentration is higher than the Ag concentration in the circuit layer 12 and the metal layer 13. Specifically, the Ag concentration at the interface 30 is the circuit layer 12 and the metal layer 13. The concentration of Ag is not less than twice as high. Here, in this embodiment, the thickness H of the Ag high concentration portion 32 is 4 nm or less.

As shown in FIG. 2, the interface 30 observed here is the center between the interface side end of the lattice image of the circuit layer 12 and the metal layer 13 and the interface side end of the lattice image of the ceramic substrate 11. A reference plane S is assumed.
Further, the Ag concentration in the circuit layer 12 and the metal layer 13 is an Ag concentration in a portion of the circuit layer 12 and the metal layer 13 that is away from the interface 30 by a certain distance (5 nm in this embodiment).

  The mass ratio of Al, Ag, O, and N when this interface 30 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Ag: O: N = 50 to 90% by mass: 1 to 30. It is set in the range of mass%: 1-10 mass%: 25 mass% or less. In addition, the spot diameter at the time of performing the analysis by EDS is 1 to 4 nm, the interface 30 is measured at a plurality of points (for example, 100 points in the present embodiment), and the average value is calculated. Further, the interface 30 between the crystal grain boundaries of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11 is not measured, and only the interface 30 between the crystal grains of the circuit layer 12 and the metal layer 13 and the ceramic substrate 11 is measured. Yes.

Moreover, as a result of measuring the Ag concentration in the circuit layer 12 and the metal layer 13 by EPMA analysis (spot diameter of 30 μm), the concentration of Ag does not change in the thickness direction as shown in FIG. That is, Ag is uniformly distributed, and the concentration gradient from the interface 30 is not confirmed. The Ag concentration in the circuit layer 12 and the metal layer 13 was an average value measured at five points at each position from the interface of the ceramic substrate 11.
Thus, in this embodiment, Ag is concentrated only in the interface 30 portion of the ceramic substrate 11.

  Below, the manufacturing method of the board | substrate 10 for power modules which is this embodiment is demonstrated with reference to FIG.4 and FIG.5.

First, as shown in FIG. 5, an Ag paste is applied to one surface and the other surface of the ceramic substrate 11 by screen printing to form a first Ag paste layer 24a and a second Ag paste layer 25a. In addition, the thickness of the 1st Ag paste layer 24a and the 2nd Ag paste layer 25a is about 0.02-200 micrometers after drying.
After the first Ag paste layer 24a and the second Ag paste layer 25a are heated to 150 to 200 ° C. to remove the solvent, baking is performed at 400 to 500 ° C., and the resin in the first Ag paste layer 24a and the second Ag paste layer 25a is removed. By removing, the first Ag fired layer 24 and the second Ag fired layer 25 are formed. In this way, Ag is fixed to one surface and the other surface of the ceramic substrate 11 (fixing step S01). The amount of Ag fixed in the fixing step S01 is in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .

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

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

Next, the ceramic substrate 11 on which the first Ag fired layer 24 and the second Ag fired layer 25 are formed is placed in the cavity 51 of the mold 50. While the mold 50 is heated to 700 to 850 ° C., the molten aluminum M is filled into the cavity 51 from the molten metal supply port 52 through the supply path 53 (molten aluminum filling step S02). At this time, the filling pressure of the molten aluminum M is set to 1 × 10 ^{5 to 3.5} × 10 ⁶ Pa. The molten aluminum M is 4N aluminum having a purity of 99.99% by mass or more. The mold 50 is made of graphite, and a release agent such as BN is applied to the inner surface of the cavity 51.

Next, after holding for a predetermined time, the mold 50 is cooled, and the molten aluminum M filled in the cavity 51 is solidified (solidification step S03). At this time, it cools over 600 minutes to 600 degreeC.
And it removes from the casting_mold | template 50 and removes excess aluminum by cutting or an etching etc., and forms the circuit layer 12 and the metal layer 13 (finishing process S04).
In this way, the power module substrate 10 according to the present embodiment is produced.

  In the method for manufacturing the power module substrate 10 and the power module substrate 10 according to the present embodiment configured as described above, Ag is applied to one surface and the other surface of the ceramic substrate 11 in the fixing step S01. The first Ag fired layer 24 and the second Ag fired layer 25 are formed, and in the molten aluminum filling step S02, the ceramic substrate 11 placed in the cavity 51 of the mold 50 and the molten aluminum M are brought into contact with each other. Therefore, in the region of the ceramic substrate 10 where the first Ag fired layer 24 and the second Ag fired layer 25 are formed, the reactivity with aluminum is increased, and the reaction between the ceramic substrate 11 and the molten aluminum M is promoted. It will be. Therefore, even if the contact time between the molten aluminum M and the ceramic substrate 11 is shortened or the filling pressure of the molten aluminum M is lowered, the interface strength between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13 is improved. Therefore, the power module substrate 10 having excellent reliability can be produced.

In addition, since the amount of Ag fixed in the fixing step S01 is in the range of 0.1 mg / cm ² or more and 20 mg / cm ² or less, the effect of promoting the reaction by Ag can be reliably achieved, and Ag It can suppress that the reaction material of Al and Al produces | generates excessively. Therefore, the interface strength between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13 can be improved.

Further, in the fixing step S01, an Ag paste is applied to form a first Ag paste layer 24a and a second Ag paste layer 25a, and the first Ag paste layer 24a and the second Ag paste layer 25a are fired to thereby fire the first Ag fired layer. 24 and the second Ag fired layer 25 are formed. Therefore, the Ag amount in the first Ag fired layer 24 and the second Ag fired layer 25 can be adjusted with high accuracy.
Moreover, since Ag does not oxidize even if it heats and bakes by air | atmosphere atmosphere, the 1st Ag baking layer 24 and the 2nd Ag baking layer 25 can be formed easily.

  Furthermore, in this embodiment, since the circuit layer 12 is formed on one surface of the ceramic substrate 11 and the metal layer 13 is formed on the other surface at the same time, the occurrence of warpage in the ceramic substrate 11 is prevented. Can do.

  Further, in the present embodiment, since the filling temperature of the molten aluminum M is set to 700 to 850 ° C. in the molten aluminum filling step S02, the molten metal M is sufficiently filled in the cavity 51 because the molten metal flow is ensured. And can be easily taken out from the mold 50 without being in close contact with the mold 50.

  As described above, the power module substrate 10 according to the present embodiment is produced by the fixing step S01, the molten aluminum filling step S02, the solidification step S03, and the finishing step S04. Here, the Ag of the first Ag fired layer 24 and the second Ag fired layer 25 fixed to the ceramic substrate 11 easily diffuses into the molten aluminum M. Therefore, in the power module substrate 10 after production, the circuit layer 12 and the metal layer 13, as shown in FIG. 3, the Ag concentration distribution in the thickness direction is not confirmed.

  Then, when the interface between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13 is observed in detail with an electron microscope, the Ag high-concentration portion in which the Ag concentration is at least twice the Ag concentration in the circuit layer 12 and the metal layer 13 32 is formed. The thickness H of the Ag high concentration portion 32 is 4 nm or less. Thus, an Ag high concentration portion 32 in which the Ag concentration is twice or more the Ag concentration in the circuit layer 12 and the metal layer 13 is formed at the interface 30 between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13. Therefore, the presence of Ag atoms in the interface 30 can improve the interface strength between the ceramic substrate 11 made of AlN, the circuit layer 12 and the metal layer 13.

  The mass ratio of Al, Ag, O, and N obtained by analyzing the interface 30 between the ceramic substrate 11 and the circuit layer 12 and the metal layer 13 by energy dispersive X-ray analysis is Al: Ag: O: N = 50˜. 90% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less, so that an excessive reaction product of Ag and Al can be prevented, and the ceramic substrate 11 and the circuit layer 12 and the interface strength with the metal layer 13 are improved. Therefore, the reliability at the time of heat cycle load can be improved.

  In the power module 1 according to the present embodiment, the circuit layer 12 is formed on one surface of the ceramic substrate 11, the metal layer 13 is formed on the other surface, and the other surface side of the metal layer 13 is formed. Since the heat sink 40 is provided, the thermal stress caused by the difference in thermal expansion coefficient between the heat sink 40 and the ceramic substrate 11 can be relieved by the metal layer 13, and the occurrence of cracks in the ceramic substrate 11 can be prevented. Can do. Therefore, insulation between the semiconductor element 3 disposed on the circuit layer 12 and the heat sink 40 can be ensured.

Next, a second embodiment of the present invention will be described. FIG. 6 shows a power module substrate 110 and a power module 101 according to the second embodiment of the present invention.
The power module 101 includes a power module substrate 110, a semiconductor element 103 bonded to one surface (the upper surface in FIG. 6) of the power module substrate 110 via a solder layer 102, and the power module substrate 110. And a heat sink 140 disposed on the other surface (the lower surface in FIG. 6) side. Here, the solder layer 102 is made of, for example, Sn—Ag, Sn—In, or Sn—Ag—Ag solder material. In the present embodiment, a Ni film (not shown) is provided between the circuit layer 112 and the solder layer 102.

The power module substrate 110 according to the present embodiment includes a ceramic substrate 111 and a circuit layer 112 disposed on one surface of the ceramic substrate 111.
The ceramic substrate 111 prevents electrical connection between the one surface side and the other surface side, and is made of highly insulating Si ₃ N ₄ (silicon nitride). 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 0.32 mm.

The circuit layer 112 is formed by contacting and solidifying molten aluminum made of aluminum or an aluminum alloy on one surface of the ceramic substrate 111.
In the present embodiment, the circuit layer 112 is made of aluminum (so-called 4N aluminum) having a purity of 99.99% by mass or more.

  The heat sink 140 is for cooling the power module substrate 110 on which the semiconductor element 103 is mounted. In the present embodiment, the heat dissipation plate is made of A6063 (aluminum alloy) having good thermal conductivity. The heat sink 140 is directly bonded to the other surface of the ceramic substrate 111 as shown in FIG.

When the interface 130 between the ceramic substrate 111 and the circuit layer 112 is observed with a transmission electron microscope, an Ag high concentration portion 132 in which Ag is concentrated is formed on the interface 130 as shown in FIG. In the Ag high concentration portion 132, the Ag concentration is higher than the Ag concentration in the circuit layer 112. Specifically, the Ag concentration at the interface 130 is more than twice the Ag concentration in the circuit layer 112. It is said that. Here, in this embodiment, the thickness H of the Ag high concentration portion 132 is 4 nm or less.
Further, the high Ag concentration portion 132 contains Ca, and the Ca concentration at the interface 130 is higher than the Ca concentration in the circuit layer 112.

Note that the interface 130 observed here is, as shown in FIG. 7, the center between the interface side end of the lattice image of the circuit layer 112 and the interface side end of the lattice image of the ceramic substrate 111 as a reference plane S. To do.
Further, the Ag concentration and the Ca concentration in the circuit layer 112 are the Ag concentration and the Ca concentration in a part of the circuit layer 112 that is away from the interface 130 by a certain distance (5 nm in this embodiment).

  The mass ratio of Al, Si, Ag, O, and N when the interface 130 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Si: Ag: O: N = 15 to 45% by mass. 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less. In addition, the spot diameter at the time of analyzing by EDS is 1 to 4 nm, the interface 130 is measured at a plurality of points (for example, 100 points in the present embodiment), and the average value is calculated. In addition, the interface 130 between the crystal grain boundary of the circuit layer 112 and the ceramic substrate 111 is not a measurement target, and only the interface 130 between the crystal grain of the circuit layer 112 and the ceramic substrate 111 is a measurement target.

Further, as a result of measuring the Ag concentration in the circuit layer 112 by EPMA analysis (spot diameter of 30 μm), the concentration of Ag and Ca does not change in the thickness direction as shown in FIG. That is, Ag and Ca are uniformly distributed, and a concentration gradient from the interface 130 is not recognized. The Ag concentration and the Ca concentration in the circuit layer 112 were average values measured at five points at each position from the interface 130 of the ceramic substrate 111.
Thus, in this embodiment, Ag and Ca are concentrated only in the interface 130 portion of the ceramic substrate 111.

  Below, the manufacturing method of the board | substrate 110 for power modules which is this embodiment is demonstrated with reference to FIG. 9, FIG.

First, Ag and Ca are fixed to one surface of the ceramic substrate 111 by sputtering to form a first Ag layer 124, and Ag and Ca are fixed to the other surface of the ceramic substrate 111 by sputtering to form a second Ag layer 125. Form (fixing step S101). Here, the total amount of Ag and Ca in the first Ag layer 124 and the second Ag layer 125 is 0.1 mg / cm ² or more and 20 mg / cm ² or less.

Next, the ceramic substrate 111 is placed in the cavity 151 of the mold 150 so that one surface thereof faces the molten metal supply port 152 side. In a state where the mold 150 is heated to 700 to 850 ° C., the molten aluminum M is filled into the cavity 151 from the molten metal supply port 152 through the supply path 153 (molten aluminum filling step S102). At this time, the filling pressure of the molten aluminum M is set to 1 × 10 ^{5 to 3.5} × 10 ⁶ Pa. The molten aluminum M is 4N aluminum having a purity of 99.99% by mass or more.
And after hold | maintaining for predetermined time, the casting_mold | template 150 is cooled and the molten aluminum M with which the cavity 151 was filled is solidified (solidification process S103).

Next, the ceramic substrate 111 is placed in the cavity 151 of the mold 150 so that the other surface faces the molten metal supply port 152 side. While heating the mold 150 to 700-850 ° C., from the melt feed port 152 through the supply passage 153 to fill the second molten aluminum _{M 2} in the cavity 151 (second molten aluminum filling step S104). At this time, the filling pressure of the second molten aluminum M ₂ is set to 1 × 10 ^{5 to 3.5} × 10 ⁶ Pa. The second molten aluminum _{M 2} is an A6063 (aluminum alloy).
Then, after a predetermined time holding the mold 150 is cooled, to solidify the second molten aluminum _{M 2} filled in the cavity 151 (the second coagulation step S105).

Then, the ceramic substrate 111 is taken out from the mold 150, and excess aluminum is removed by cutting or etching to form the circuit layer 112 and the heat sink 140 (finishing step S106).
Thus, the power module substrate 110 and the heat sink 140 according to the present embodiment are produced.

  In the manufacturing method of the power module substrate 110 and the power module substrate 110 according to the present embodiment configured as described above, Ag and Ca are contained on one surface of the ceramic substrate 111 in the fixing step S101. Since the first Ag layer 124 is formed and the ceramic substrate 111 placed on the mold 150 is brought into contact with the molten aluminum M in the molten aluminum filling step S102, the reactivity between the molten aluminum M and the ceramic substrate 111 is achieved. As a result, the interface strength between the ceramic substrate 111 and the circuit layer 112 can be improved.

Similarly, the second Ag layer 125 containing Ag and Ca is formed on the other surface of the ceramic substrate 111 by the fixing step S101, and the ceramic substrate 111 placed on the mold 150 is formed by the second molten aluminum filling step S104. Since the second molten aluminum M ₂ is brought into contact with the second molten aluminum M ₂ , the reactivity between the second molten aluminum M ₂ and the ceramic substrate 111 is increased, and the interface strength between the ceramic substrate 111 and the heat sink 140 is improved. Is possible.

In addition, since the total amount of Ag and Ca fixed in the fixing step S101 is 0.1 mg / cm ² or more and 20 mg / cm ² or less, the reaction between the ceramic substrate 111 and aluminum by Ag and Ca is promoted. It is possible to suppress the generation of excessive reaction products of Ag and Ca and Al. Therefore, the interface strength between the ceramic substrate 111 and the circuit layer 112 and the heat sink 140 can be improved.
Furthermore, since the fixing step S101 is configured to fix Ag and Ca to one surface and the other surface of the ceramic substrate 111 by sputtering, the Ag amount and the Ca amount in the first Ag layer 124 and the second Ag layer 125 are accurately determined. It can be adjusted well.

  Furthermore, in this embodiment, the step of forming the circuit layer 112 on one surface of the ceramic substrate 111 and the step of forming the heat sink 140 on the other surface of the ceramic substrate 111 are separate steps. The layer 112 and the heat sink 140 can be made of different aluminum materials.

  In addition, as described above, the power module substrate 110 according to the present embodiment includes the fixing step S101, the molten aluminum filling step S102, the solidification step S103, the second molten aluminum filling step S104, the second solidification step S105, and the finishing step S106. Is produced. Here, since Ag and Ca of the first Ag layer 124 fixed to the ceramic substrate 111 easily diffuse into the molten aluminum M, the thickness direction of the circuit layer 112 in the power module substrate 110 after production The Ag concentration distribution and Ca concentration distribution are not confirmed.

However, when the interface 130 between the ceramic substrate 111 and the circuit layer 112 is observed in detail with an electron microscope, an Ag high-concentration portion 132 in which the Ag concentration is at least twice the Ag concentration in the circuit layer 112 is formed. Note that the thickness H of the Ag high concentration portion 132 is 4 nm or less. In the Ag high concentration portion 132, Ca is also concentrated.
Thus, since the Ag high concentration part 132 in which Ag and Ca are concentrated is formed at the interface 130 between the ceramic substrate 111 and the circuit layer 112, the Ag atoms and Ca atoms are present in the interface 130. The interface strength between the ceramic substrate 111 made of Si ₃ N ₄ and the circuit layer 112 can be improved.
Similarly, Ag and Ca are concentrated at the interface between the ceramic substrate 111 and the heat sink 140, and the interface strength between the ceramic substrate 111 and the heat sink 140 can be improved.

  The mass ratio of Al, Si, Ag, O, and N obtained by analyzing the interface 130 between the ceramic substrate 111 and the circuit layer 112 by energy dispersive X-ray analysis is Al: Si: Ag: O: N = 15 to 45% by mass: 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less, so that an excessive reaction product of Ag and Al can be prevented, The interface strength between the ceramic substrate 111 and the circuit layer 112 is improved. Therefore, the reliability at the time of heat cycle load can be improved.

Next, a third embodiment of the present invention will be described. FIG. 11 shows a power module substrate 210 and a power module 201 according to the third embodiment of the present invention.
The power module 201 includes a power module substrate 210, a semiconductor element 203 bonded to one surface (upper surface in FIG. 11) of the power module substrate 210 via a solder layer 202, and the power module substrate 210. And a heat sink 240 disposed on the other surface (lower surface in FIG. 11) side. Here, the solder layer 202 is made of, for example, a Sn—Ag, Sn—In, or Sn—Ag—Ag solder material. In this embodiment, a Ni film (not shown) is provided between the circuit layer 212 and the solder layer 202.

The power module substrate 210 according to this embodiment includes a ceramic substrate 211, a circuit layer 212 disposed on one surface of the ceramic substrate 211, and a metal layer 213 disposed on the other surface. Yes.
The ceramic substrate 211 prevents electrical connection between the one surface side and the other surface side, and is made of Al ₂ O ₃ (alumina) having high insulation properties. 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 0.635 mm.

The circuit layer 212 is formed by contacting and solidifying molten aluminum made of aluminum or an aluminum alloy on one surface of the ceramic substrate 211.
In the present embodiment, the circuit layer 212 is made of aluminum (so-called 4N aluminum) having a purity of 99.99% by mass or more.

  As shown in FIG. 16, the metal layer 213 is formed by joining a metal plate 223 made of aluminum or an aluminum alloy to the other surface of the ceramic substrate 211. In this embodiment, the metal layer 213 is formed by joining a metal plate 223 made of a rolled plate of aluminum (so-called 4N aluminum) having a purity of 99.99 mass% or more to the ceramic substrate 211.

The heat sink 240 is for cooling the power module substrate 210 on which the semiconductor element 203 is mounted, and includes a top plate portion 241 and a flow path 242 for circulating a cooling medium (for example, cooling water). . The heat sink 240 (top plate portion 241) 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 215 made of aluminum, an aluminum alloy, or a composite material containing aluminum (for example, AlSiC) is provided between the top plate portion 241 of the heat sink 240 and the metal layer 213. .

  When the interface 230 between the ceramic substrate 211 and the circuit layer 212 is observed with a transmission electron microscope, an Ag high concentration portion 232 in which Ag is concentrated is formed at the interface 230 as shown in FIG. In the Ag high concentration portion 232, the Ag concentration is higher than the Ag concentration in the circuit layer 212. Specifically, the Ag concentration at the interface 230 is twice or more the Ag concentration in the circuit layer 212. It is said that. Here, in the present embodiment, the thickness H of the Ag high concentration portion 232 is set to 4 nm or less.

Note that the interface 230 observed here is, as shown in FIG. 12, the center between the interface side end of the lattice image of the circuit layer 212 and the interface side end of the lattice image of the ceramic substrate 211 as a reference plane S. To do.
The Ag concentration in the circuit layer 212 is the Ag concentration in a portion of the circuit layer 212 that is away from the interface 230 by a certain distance (5 nm in this embodiment).

  The mass ratio of Al, Ag, and O when the interface 230 is analyzed by energy dispersive X-ray analysis (EDS) is Al: Ag: O = 50 to 90 mass%: 1 to 30 mass%: 0. It is set within a range of ˜45 mass%. In addition, the spot diameter at the time of analyzing by EDS is 1 to 4 nm, the interface 230 is measured at a plurality of points (for example, 100 points in the present embodiment), and the average value is calculated. Further, the interface 230 between the crystal grain boundary of the circuit layer 212 and the ceramic substrate 211 is not measured, and only the interface 230 between the crystal grain of the circuit layer 212 and the ceramic substrate 211 is measured.

Further, as a result of measuring the Ag concentration in the circuit layer 212 by EPMA analysis (spot diameter of 30 μm), the Ag concentration does not change in the thickness direction as shown in FIG. That is, Ag is distributed uniformly and no concentration gradient from the interface 230 is observed. The Ag concentration in the circuit layer 212 was an average value measured at five points at each position from the interface 230 of the ceramic substrate 211.
Thus, in the present embodiment, Ag is concentrated only in the interface 230 portion of the ceramic substrate 211.

Further, as a result of measuring the Ag concentration in the metal layer 213 by EPMA analysis (spot diameter of 30 μm), as shown in FIG. 14, in the vicinity of the bonding interface 236 between the metal layer 213 and the ceramic substrate 211, the bonding direction from the bonding interface 236 A concentration gradient layer 237 is formed in which the Ag concentration gradually decreases as they are separated from each other. Here, the Ag concentration in the vicinity of the bonding interface 236 of the metal layer 213 is set within a range of 0.05 mass% or more and 5 mass% or less.
The Ag concentration in the vicinity of the bonding interface 236 of the metal layer 213 is an average value measured at five points at a position 50 μm from the bonding interface 236 by EPMA analysis (spot diameter of 30 μm). In addition, the graph of FIG. 14 is obtained by performing line analysis in the stacking direction in the central portion of the metal layer 213 (metal plate 223) and using the concentration at the above-described 50 μm position as a reference.

  Below, the manufacturing method of the board | substrate 210 for power modules which is this embodiment is demonstrated with reference to FIG.15 and FIG.17.

First, Ag is fixed to one surface of the ceramic substrate 211 by sputtering to form a first Ag layer 224, and Ag is fixed to the other surface of the ceramic substrate 211 by sputtering to form a second Ag layer 225 (adhesion). Step S201). Here, the Ag amount in the first Ag layer 224 and the second Ag layer 225 is 0.1 mg / cm ² or more and 20 mg / cm ² or less.

Next, the ceramic substrate 211 is installed in the cavity 251 of the mold 250 so that one surface thereof faces the molten metal supply port 252 side. In a state where the mold 250 is heated to 700 to 850 ° C., the molten aluminum M is filled into the cavity 251 from the molten metal supply port 252 through the supply path 253 (molten aluminum filling step S202). At this time, the filling pressure of the molten aluminum M is set to 1 × 10 ^{5 to 3.5} × 10 ⁶ Pa. The molten aluminum M is 4N aluminum having a purity of 99.99% by mass or more.
And after hold | maintaining for predetermined time, the casting_mold | template 250 is cooled and the molten aluminum M with which the cavity 251 was filled is solidified (solidification process S203).

Next, the metal plate 223 is joined to the other surface of the ceramic substrate 211 (metal plate joining step S204).
First, the above-described ceramic substrate 211 is taken out from the mold 250 and a metal plate 223 is laminated on the other surface of the ceramic substrate 211. The metal plate 223 is a rolled plate of 4N aluminum having a purity of 99.99% by mass or more.
Then, the ceramic substrate 211 and the metal plate 223 are charged in the stacking direction (pressure 1 to 35 kgf / cm ² ) and charged in a vacuum heating furnace to be heated, and the interface between the metal plate 223 and the ceramic substrate 211. A molten metal region 227 is formed on the substrate. Here, in the molten metal region 227, as shown in FIG. 17, the Ag concentration in the vicinity of the second Ag layer 225 of the metal plate 223 increases due to the diffusion of Ag in the second Ag layer 225 toward the metal plate 223. It is formed by lowering the melting point.

When the pressure is less than 1 kgf / cm ² , there is a possibility that the ceramic substrate 211 and the metal plate 223 cannot be bonded well. Moreover, when the above-mentioned pressure exceeds 35 kgf / cm < ² >, there exists a possibility that the metal plate 223 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 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.

  Next, Ag in the molten metal region 227 further diffuses toward the metal plate 223 side. As a result, the Ag concentration in the portion that was the molten metal region 227 gradually decreases and the melting point increases, and solidification proceeds while the temperature is kept constant. Thereby, the ceramic substrate 211 and the metal plate 223 are joined. In other words, the metal plate 2223 and the ceramic substrate 211 are joined by so-called liquid phase diffusion bonding (Transient Liquid Phase Diffusion Bonding).

Then, excess aluminum on one surface side of the ceramic substrate 211 is removed by cutting or etching to form the circuit layer 212 (finishing step S205).
In this way, the power module substrate 210 according to the present embodiment is produced.

  In the manufacturing method of the power module substrate 210 according to the present embodiment configured as described above, the first Ag layer 224 containing Ag is formed on one surface of the ceramic substrate 211 by the fixing step S201, Since the ceramic substrate 211 installed in the mold 250 and the molten aluminum M are brought into contact with each other by the molten aluminum filling step S202, the reactivity between the molten aluminum M and the ceramic substrate 211 is caused by Ag present in the interface 230. As a result, the interface strength between the ceramic substrate 211 and the circuit layer 212 can be improved.

  In addition, since the metal layer 213 is formed by bonding the ceramic substrate 211 and the metal plate 223 by liquid phase diffusion bonding, the metal plate 223 and the ceramic substrate 211 can be firmly bonded. it can. Further, Ag dissolves in the metal layer 213, whereby the strength of the metal layer 213 in the vicinity of the bonding interface 236 with the ceramic substrate 211 can be improved.

Further, since the amount of Ag fixed in the fixing step S201 is 0.1 mg / cm ² or more and 20 mg / cm ² or less, the reaction between the ceramic substrate 211 and aluminum by Ag can be promoted, and Ag and It can suppress that the reaction material of Al produces | generates excessively. Therefore, the interface strength between the ceramic substrate 211 and the circuit layer 212 can be reliably improved.
Furthermore, since the fixing step S201 is configured to fix Ag to one surface and the other surface of the ceramic substrate 211 by sputtering, the fixing amount of Ag in the first Ag layer 224 and the second Ag layer 225 is accurately adjusted. can do.

  Furthermore, in the present embodiment, the step of forming the circuit layer 212 on one surface of the ceramic substrate 211 and the step of forming the metal layer 213 on the other surface of the ceramic substrate 211 are separate steps. The circuit layer 212 and the metal layer 213 can be made of different aluminum materials.

  Further, in the power module substrate 210 according to the present embodiment, the Ag concentration distribution is not recognized in the thickness direction in the circuit layer 212, and the Ag concentration distribution is recognized in the thickness direction in the metal layer 213. This is because Ag is easily diffused into the molten aluminum M because the circuit layer 212 is formed by bringing the molten aluminum M into contact with the ceramic substrate 211. On the other hand, in the metal layer 213, since the molten metal region 227 is formed only in the vicinity of the bonding interface 236 with the ceramic substrate 211, Ag diffuses inside the metal plate 223, so that a concentration gradient of Ag is formed. It is done.

Here, when the interface 230 between the ceramic substrate 211 and the circuit layer 212 is observed in detail with an electron microscope, an Ag high-concentration portion 232 in which the Ag concentration is twice or more the Ag concentration in the circuit layer 212 is formed. . Note that the thickness H of the Ag high concentration portion 232 is set to 4 nm or less.
Thus, since the Ag high concentration portion 232 in which Ag is concentrated is formed at the interface 230 between the ceramic substrate 211 and the circuit layer 212, the Ag atoms intervene in the interface 230, so that Al ₂ O ₃ The interface strength between the ceramic substrate 211 and the circuit layer 212 can be improved.

  Moreover, the mass ratio of Al, Ag, and O which analyzed the interface 230 of the ceramic substrate 211 and the circuit layer 212 by the energy dispersive X-ray analysis method is Al: Ag: O = 50-90 mass%: 1-30 mass. %: 0 to 45% by mass, it is possible to prevent the reaction product of Ag and Al from being generated excessively, and the interface strength between the ceramic substrate 211 and the circuit layer 212 is improved. Therefore, the reliability at the time of heat cycle load can be improved.

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 circuit layer has been described as being composed of aluminum (4N aluminum) having a purity of 99.99% by mass or more, but is not limited thereto, and for example, aluminum (2N aluminum) having a purity of 99% by mass or more It may be.

Moreover, although it demonstrated as what fixes Ag by application | coating of Ag paste or sputtering, it is not limited to this, such as plating, vapor deposition, CVD, sputtering, cold spray, or ink in which powder is dispersed Ag may be fixed by means such as coating.
Furthermore, in addition to Ag, one or two or more additive elements selected from Mg, Ca, and Ni may be fixed.

Further, the structure and material of the heat sink are not limited to this embodiment.
Furthermore, in the third embodiment, the ceramic substrate and the metal plate are joined using a vacuum heating furnace. However, the present invention is not limited to this, and the N ₂ atmosphere, Ar atmosphere, and He atmosphere are used. The ceramic substrate and the metal plate may be joined with each other.

A confirmation experiment conducted to confirm the effectiveness of the present invention will be described.
Ag and an additive element were fixed on both surfaces of a 40 mm square ceramic substrate made of AlN having a thickness of 0.635 mm by sputtering. This ceramic substrate was placed in a graphite mold and filled with molten aluminum made of 4N aluminum at a temperature of 800 ° C. The filling pressure was 3 × 10 ⁵ Pa. Then, the mold was cooled to 600 ° C. in 15 minutes to solidify the molten aluminum. Then, it took out from the casting_mold | template and formed the circuit layer and metal layer of 36 mm square and thickness 0.6mm by cutting.
Here, the adhesion amount of Ag and additive elements by sputtering was changed as shown in Table 1.

The power module substrate thus formed is made of 4N aluminum on the metal layer side, and a 50 mm × 60 mm, 5 mm thick aluminum equivalent to the top plate of the heat sink through a buffer layer having a thickness of 0.9 mm. The plate (A6063) was joined. The buffer layer and the aluminum plate were joined using a brazing material foil of Al-10.5 mass% Si with a thickness of 50 μm under the conditions of a temperature of 610 ° C. and a pressure of 10 kgf / cm ² .

The test piece was loaded 2000 times with a thermal cycle of −40 ° C. ← → 110 ° C., and the bonding rate was determined. The results are shown in Table 1.
In addition, the joining rate was computed with the following formula | equation. Here, the initial bonding area is an area to be bonded before bonding.
Bonding rate = (initial bonding area-peeling area) / initial bonding area

In the comparative example in which molten aluminum was brought into contact with the ceramic substrate without fixing Ag and the additive element, the bonding rate was as low as 63.5%.
On the other hand, in Inventive Example 1-13, it is confirmed that the bonding rate is improved as compared with the comparative example. In particular, in Inventive Example 1-11 in which the adhesion amount of Ag is 20 mg / cm ² or less, or the Ag and additive elements are 20 mg / cm ² or less, the joining rate is 70% or more, and the joining reliability is increased. Is confirmed to be improved.

1, 101, 201 Power module 10, 110, 210 Power module substrate 11, 111, 211 Ceramic substrate 12, 112, 212 Circuit layer (aluminum layer)
13, 213 Metal layer (second aluminum layer)

Claims (12)

A method for producing a power module substrate in which an aluminum layer made of aluminum or an aluminum alloy is formed on one surface of a ceramic substrate,
An adhering step of adhering Ag to at least an area where the aluminum layer is formed on one surface of the ceramic substrate, and forming an adhering layer containing Ag;
Placing the ceramic substrate on which the fixed layer is formed in a mold, filling the mold with molten aluminum, and contacting the ceramic substrate with the molten aluminum;
And a solidifying step for solidifying the molten aluminum in contact with the ceramic substrate. ^{2. The} method for manufacturing a power module substrate according to claim 1, wherein the fixing amount of Ag in the fixing step is in the range of 0.1 mg / cm ^{2 to} 20 mg / cm ² .   3. The power module substrate according to claim 1, wherein, in the fixing step, one or more additive elements selected from Mg, Ca, and Ni are fixed in addition to Ag. 4. Manufacturing method. 4. The power module substrate according to claim 3, wherein the total amount of Ag and the additional element in the fixing step is within a range of 0.1 mg / cm ^{2 to} 20 mg / cm ^2. Manufacturing method.   In the fixing step, Ag is fixed by plating, vapor deposition, CVD, sputtering, cold spray, or application of ink in which powder is dispersed. The manufacturing method of the board | substrate for power modules as described in a term.   The method for manufacturing a power module substrate according to any one of claims 1 to 4, wherein in the fixing step, the fixing layer is formed by applying an Ag paste.   The method for manufacturing a power module substrate according to any one of claims 1 to 6, wherein a second aluminum layer made of aluminum or an aluminum alloy is formed on the other surface of the ceramic substrate. A power module substrate manufactured by the method for manufacturing a power module substrate according to any one of claims 1 to 7,
In the aluminum layer, a concentration difference between an Ag concentration at a position of 50 μm from the interface with the ceramic substrate and an Ag concentration at a position of 100 μm from the interface with the ceramic substrate is 0.1% by mass or less,
A power module substrate, wherein an Ag high concentration portion having an Ag concentration of at least twice as high as an Ag concentration in the aluminum layer is formed at an interface between the ceramic substrate and the aluminum layer.   The ceramic substrate is made of AlN, and the mass ratio of Al, Ag, O, and N obtained by analyzing the interface between the ceramic substrate and the aluminum layer by energy dispersive X-ray analysis is Al: Ag: O: 9. The power module substrate according to claim 8, wherein N = 50 to 90% by mass: 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 , and the mass ratio of Al, Si, Ag, O, N analyzed by energy dispersive X-ray analysis at the interface between the ceramic substrate and the aluminum layer is Al : Si: Ag: O: N = 15 to 45% by mass: 15 to 45% by mass: 1 to 30% by mass: 1 to 10% by mass: 25% by mass or less The board | substrate for power modules as described. The ceramic substrate is made of Al ₂ O ₃ , and the mass ratio of Al, Ag, and O obtained by analyzing the interface between the ceramic substrate and the aluminum layer by energy dispersive X-ray analysis is Al: Ag: O. The power module substrate according to claim 8, wherein: 50 to 90% by mass: 1 to 30% by mass: 0 to 45% by mass.   12. The power module substrate according to claim 8, further comprising a second aluminum layer made of aluminum or an aluminum alloy on the other surface of the ceramic substrate.

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