JP2014060215A - Substrate for power module with heat sink, power module with heat sink and manufacturing method of substrate for power module with heat sink - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate for a power module with a heat sink, which can reduce initial heat resistance and inhibit raise of heat resistance under heat cycle load; and to provide a power module with a heat sink equipped with the substrate for the power module with the heat sink, and a manufacturing method of the substrate for the power module with the heat sink.SOLUTION: In a substrate for a power module with a heat sink, a metal layer 13 and a heat sink 31 are composed of Al or an Al alloy; and a copper layer 40, which is composed of a junction material formed from Cu or a Cu alloy, is formed between the metal layer 13 and the heat sink 31. The metal layer 13 and the heat sink 31 are solid-phase diffusion bonded with the copper layer 40.

Description

  The present invention provides a power module substrate in which a circuit layer is disposed on one surface of an insulating layer and a metal layer is disposed on the other surface of the insulating layer, and on the other surface side of the power module substrate. The present invention relates to a power module substrate with a heat sink including a heat sink, a power module with a heat sink including the power module substrate with a heat sink, and a method for manufacturing the power module substrate with a heat sink.

Among various semiconductor elements, a power element for high power control used for controlling an electric vehicle, an electric vehicle or the like has a large amount of heat generation. Therefore, as a substrate on which the element is mounted, for example, AlN (nitriding) 2. Description of the Related Art Conventionally, a power module substrate in which a metal plate having excellent conductivity is joined as a circuit layer on a ceramic substrate (insulating layer) made of aluminum or the like has been widely used.
Such a power module substrate has a semiconductor element mounted as a power element on the circuit layer via a solder material to form a power module.

  For example, as shown in Patent Document 1, Al is used as the metal constituting the circuit layer and the metal layer, and Al (Al alloy) is used as the metal constituting the heat sink. And the board | substrate for power modules with a heat sink by which the heat sink was brazed or soldered to the surface of the metal layer is disclosed.

  In Patent Document 2, a circuit layer and a metal layer made of Al are joined to one surface and the other surface of a ceramic substrate, and a plate material made of Cu via solder on the metal layer side of the ceramic substrate. Is disclosed, and a power module substrate with a heat sink in which a heat sink is joined to the plate member via solder is disclosed.

JP 2008-16813 A JP 2007-250638 A

  By the way, in the power module substrate with a heat sink shown in Patent Document 1, a metal layer made of aluminum and a heat sink made of an aluminum alloy are joined. However, as the efficiency of the power module has been improved and the usage environment has become severe, it cannot be said that it is sufficient from the viewpoint of thermal resistance and heat dissipation, and furthermore, a power module with a heat sink having low thermal resistance and high heat dissipation. Substrates are required.

  Moreover, in the power module substrate with a heat sink shown in Patent Document 2, the metal layer and the Cu plate material, and the heat sink and the Cu plate material are joined via solder, and the effect of heat diffusion in the surface direction by the Cu plate material is Although it can be expected, the heat cycle load conditions have become severe, and there is a risk that the solder will crack and the thermal resistance will increase.

  The present invention has been made in view of the above-described circumstances, and is a power module substrate with a heat sink that can reduce the initial thermal resistance and suppress an increase in thermal resistance during a heat cycle load, and the power with the heat sink. It is an object of the present invention to provide a power module with a heat sink provided with a module substrate, and a method for manufacturing a power module substrate with a heat sink.

  In order to solve the above-described problems, a power module substrate with a heat sink according to the present invention is formed on an insulating layer, a circuit layer formed on one surface of the insulating layer, and the other surface of the insulating layer. A power module substrate with a heat sink comprising a metal layer and a heat sink disposed on the other surface side of the insulating layer, wherein the metal layer and the heat sink are made of Al or an Al alloy, A copper layer made of a bonding material composed of Cu or Cu alloy is formed between the layer and the heat sink, and the metal layer and the heat sink are solid-phase diffusion bonded to the copper layer. It is a feature.

According to the power module substrate with a heat sink of the present invention, the metal layer made of Al or Al alloy and the heat sink are solid-phase diffusion bonded to the copper layer made of the bonding material made of Cu or Cu alloy. The metal layer and the heat sink are firmly bonded by the copper layer. Therefore, when a heat cycle is applied, it is possible to suppress an increase in thermal resistance by suppressing the occurrence of peeling at the bonding interface between the metal layer and the copper layer and the bonding interface between the heat sink and the copper layer. Can be improved.
In addition, since a copper layer made of Cu or Cu alloy having good thermal conductivity is formed between the metal layer and the heat sink, the heat from the semiconductor element is spread and dissipated in the in-plane direction of the copper layer. The heat can be efficiently transferred to the heat sink, and the initial thermal resistance can be reduced.

In addition, a diffusion layer made of Al and Cu is formed at a bonding interface between the metal layer and the copper layer and a bonding interface between the heat sink and the copper layer, and the diffusion layer includes a plurality of intermetallic compounds. It is good also as a structure laminated | stacked along the said joining interface, and the oxide disperse | distributing to the joining interface of the said diffusion layer and the said copper layer in the layer form along the said joining interface.
Since a diffusion layer made of Cu and Al is formed at the bonding interface between the metal layer and the copper layer and the bonding interface between the heat sink and the copper layer, the Al (aluminum atom) in the metal layer and the copper layer Cu (copper atom), Al in the heat sink, and Cu in the copper layer are sufficiently interdiffused, and the metal layer and the copper layer, and the heat sink and the copper layer are firmly bonded.
In addition, since oxides are dispersed in layers along the bonding interface at the bonding interface between the diffusion layer and the copper layer, the oxide film formed on the surface of the bonding material is destroyed and solid phase diffusion bonding is performed. Is fully progressing.

Here, it is preferable that the average crystal grain size of the copper layer is in the range of 50 μm or more and 200 μm or less, and the average crystal grain size of the metal layer is 500 μm or more.
In this case, since the average crystal grain sizes of the metal layer and the copper layer are set to be relatively large, excessive strain is not accumulated in the metal layer and the copper layer, and the fatigue characteristics are good. Therefore, in the heat cycle load, the bonding reliability against the thermal stress generated between the metal layer and the copper layer is improved.

The thickness of the bonding material may be 0.05 mm or greater and 3.0 mm or less.
By setting the thickness of the bonding material in the above range, when transferring the heat generated from the semiconductor element to the heat sink side, the heat can be efficiently transferred by spreading in the in-plane direction of the copper layer. It is possible to reduce the thermal resistance.

A power module with a heat sink according to the present invention includes the above-described power module substrate with a heat sink, and a semiconductor element bonded to one side of the circuit layer.
According to the power module with a heat sink of the present invention, since the power module substrate with a heat sink as described above is provided, the initial thermal resistance is low, and an increase in the thermal resistance is suppressed even during a heat cycle load. The stability of the operation of the element can be improved.

  The method of manufacturing a power module substrate with a heat sink according to the present invention includes an insulating layer, a circuit layer formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, and the insulating layer. A power module substrate with a heat sink provided with a heat sink disposed on the other surface side of the layer, wherein a metal layer made of Al or an Al alloy is formed on the other surface of the insulating layer. A metal layer forming step to form, and a heat sink joining step of joining a heat sink made of Al or Al alloy with a bonding material made of Cu or Cu alloy interposed on the other surface side of the insulating layer, In the heat sink bonding step, the metal layer and the bonding material, and the heat sink and the bonding material are solid phase diffusion bonded.

  According to the method for manufacturing a power module substrate with a heat sink of the present invention, the metal layer composed of Al or Al alloy and the heat sink are solid-phase diffusion bonded via a bonding material composed of Cu or Cu alloy. Further, Al in the metal layer and the heat sink and Cu in the bonding material are interdiffused, and a power module substrate with a heat sink in which the metal layer and the heat sink are bonded by a copper layer made of Cu or Cu alloy can be obtained. .

Further, in the heat sink bonding step, to the heat sink and the metal layer in a state loaded with 3 kgf / cm ² or more 35 kgf / cm ² or less of a load, by holding less than 400 ° C. or higher 548 ° C., the metal The layer and the bonding material, and the heat sink and the bonding material are solid phase diffusion bonded.
With such a configuration, the metal layer and the bonding material, and the heat sink and the bonding material are reliably solid-phase diffusion bonded, and a copper layer is formed between the metal layer and the heat sink. Further, when solid phase diffusion bonding is performed in this manner, a gap is hardly generated between the metal layer and the copper layer and between the heat sink and the copper layer. Can improve heat conduction and reduce thermal resistance. Furthermore, since solid phase diffusion bonding can be performed at a low temperature compared to the case of bonding with a brazing material, the occurrence of warpage due to the difference in thermal expansion coefficient between the power module substrate and the heat sink is suppressed, and the thermal resistance is reduced. Can be reduced. In addition, the bonding interface formed by this solid phase diffusion bonding is firmly bonded, and when a heat cycle is applied, peeling is unlikely to occur and an increase in thermal resistance can be suppressed.

  According to the present invention, a power module substrate with a heat sink that can reduce an initial thermal resistance and suppress an increase in thermal resistance during a heat cycle load, a power module with a heat sink including the power module substrate with a heat sink, And the manufacturing method of the board | substrate for power modules with a heat sink can be provided.

It is a schematic explanatory drawing of the power module with a heat sink which concerns on embodiment of this invention, the board | substrate for power modules with a heat sink, and the board | substrate for power modules. It is an enlarged view of the junction part of the metal layer of FIG. 1, and a heat sink. FIG. 3 is an enlarged explanatory diagram of a first diffusion layer at a bonding interface between a metal layer and a copper layer in FIG. 2. FIG. 3 is an enlarged explanatory diagram of a second diffusion layer at a bonding interface between the heat sink and the copper layer in FIG. 2. It is a flowchart explaining the manufacturing method of the power module with a heat sink which concerns on embodiment of this invention. It is a schematic explanatory drawing of the manufacturing method of the board | substrate for power modules with a heat sink which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 shows a power module 1 with a heat sink, a power module substrate 30 with a heat sink, and a power module substrate 10 according to an embodiment of the present invention.
The power module 1 with a heat sink includes a power module substrate 30 with a heat sink and a semiconductor element 3 bonded to one side (the upper side in FIG. 1) of the power module substrate 30 with a heat sink via a solder layer 2. I have.

The solder layer 2 is made of, for example, a Sn-Ag, Sn-Cu, Sn-In, or Sn-Ag-Cu solder material (so-called lead-free solder material). And the semiconductor element 3 are joined.
The semiconductor element 3 is an electronic component including a semiconductor, and various semiconductor elements are selected according to the required function. In this embodiment, an IGBT element is used.

The power module substrate 30 with a heat sink includes a power module substrate 10 and a heat sink 31 disposed on the other side (lower side in FIG. 1) of the power module substrate 10.
The heat sink 31 is for dissipating heat on the power module substrate 10 side. The heat sink 31 is preferably made of a material having good thermal conductivity, and is made of A6063 in this embodiment. The heat sink 31 is provided with a flow path 32 through which a cooling fluid flows.

  As shown in FIG. 1, the power module substrate 10 includes a ceramic substrate 11 (insulating layer), a circuit layer 12 formed on one surface of the ceramic substrate 11 (upper surface in FIG. 1), and the ceramic substrate 11. And a metal layer 13 formed on the other surface (the lower surface in FIG. 1).

  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 joining a metal plate to one surface (the upper surface in FIG. 1) of the ceramic substrate 11. As the metal plate, a pure aluminum plate, an aluminum alloy plate, a pure copper plate, a copper alloy plate, or the like can be used. In the present embodiment, the circuit layer 12 is formed by bonding an aluminum plate 22 made of an Al (so-called 4NAl) rolled plate having a purity of 99.99% or more to the ceramic substrate 11.

  The metal layer 13 is formed by joining a metal plate made of aluminum or an aluminum alloy to the other surface (the lower surface in FIG. 1) of the ceramic substrate 11. In the present embodiment, the metal layer 13 is formed by joining an aluminum plate 23 made of a rolled plate of Al (so-called 4NAl) having a purity of 99.99% or more to the ceramic substrate 11.

The metal layer 13 of the power module substrate 10 and the heat sink 31 are joined by solid phase diffusion bonding via the copper layer 40.
The copper layer 40 joins the power module substrate 10 and the heat sink 31. The copper layer 40 is constituted by a bonding material 50 made of an oxygen-free copper rolled plate. The thickness of the bonding material 50 is preferably set to 0.05 mm or more and 3.0 mm or less.

A first diffusion layer 41 (diffusion layer) is formed at the bonding interface between the metal layer 13 and the copper layer 40, as shown in FIG. Similarly, a second diffusion layer 42 (diffusion layer) is also formed at the bonding interface between the heat sink 31 and the copper layer 40.
The first diffusion layer 41 is formed by interdiffusion of Al (aluminum atoms) in the metal layer 13 and Cu (copper atoms) in the copper layer 40. The first diffusion layer 41 has a concentration gradient in which the Al concentration gradually decreases and the Cu concentration increases as it goes from the metal layer 13 to the copper layer 40.

  The second diffusion layer 42 is formed by mutual diffusion of Al (aluminum atoms) of the heat sink 31 and Cu (copper atoms) of the copper layer 40. The second diffusion layer 42 has a concentration gradient in which the Al concentration gradually decreases and the Cu concentration increases as it goes from the heat sink 31 to the copper layer 40.

FIG. 3 is an enlarged explanatory view of the first diffusion layer 41. The first diffusion layer 41 is composed of an intermetallic compound composed of Al and Cu. In the present embodiment, a plurality of intermetallic compounds are stacked along the bonding interface. Here, the thickness t of the first diffusion layer 41 is set in the range of 1 μm to 80 μm, preferably in the range of 5 μm to 80 μm.
In the present embodiment, as shown in FIG. 3, a structure in which three types of intermetallic compounds are stacked is formed, and in order from the metal layer 13 side to the copper layer 40 side, a θ phase 43, a η2 phase 44, The ζ2 phase 45 is set.
In addition, the oxide 46 is dispersed in layers along the bonding interface at the bonding interface between the first diffusion layer 41 and the copper layer 40. In the present embodiment, the oxide 46 is an aluminum oxide such as alumina (Al ₂ O ₃ ). The oxide 46 is dispersed in a state of being divided at the interface between the first diffusion layer 41 and the copper layer 40, and there is a region where the first diffusion layer 41 and the copper layer 40 are in direct contact. ing.

FIG. 4 is an enlarged explanatory view of the second diffusion layer 42. The second diffusion layer 42 is composed of an intermetallic compound composed of Al and Cu. In the present embodiment, a plurality of intermetallic compounds are stacked along the bonding interface. Here, the thickness t of the second diffusion layer 42 is set in the range of 1 μm to 80 μm, preferably in the range of 5 μm to 80 μm.
In the present embodiment, as shown in FIG. 3, a structure in which three kinds of intermetallic compounds are laminated is formed, and in order from the heat sink 31 side to the copper layer 40 side, the θ phase 43, η2 phase 44, ζ2 Phase 45.

In addition, the oxide 46 is dispersed in layers along the bonding interface at the bonding interface between the second diffusion layer 42 and the copper layer 40. In the present embodiment, the oxide 46 is dispersed in a state of being divided at the interface between the second diffusion layer 42 and the copper layer 40, and the second diffusion layer 42 and the copper layer 40 are in direct contact with each other. There is also an area.
Further, in the present embodiment, the average crystal grain size of the copper layer 40 is in the range of 50 μm or more and 200 μm or less, and the average crystal grain size of the metal layer 13 and the heat sink 31 is 500 μm or more.

Next, the manufacturing method of the power module 1 with a heat sink, the power module substrate 30 with a heat sink, and the power module substrate 10 according to the present embodiment will be described with reference to FIGS.
First, as shown in FIG. 6, aluminum plates 22 and 23 are laminated on one surface and the other surface of the ceramic substrate 11 via a brazing material. Then, the ceramic substrate 11 and the aluminum plates 22 and 23 are joined by cooling after pressing and heating, thereby forming the circuit layer 12 and the metal layer 13 (circuit layer and metal layer forming step S11). The brazing temperature is set to 640 ° C to 650 ° C.
In this way, the power module substrate 10 is obtained.

Next, as illustrated in FIG. 6, the bonding material 50 and the heat sink 31 are sequentially arranged on the other surface side of the power module substrate 10. And with respect to what laminated | stacked this board | substrate 10 for power modules, the joining material 50, and the heat sink 31, a load was loaded from one side and the other side (in FIG. 6, upper side and lower side), and it puts in a vacuum heating furnace Deploy. In this embodiment, the metal layer 13 and the bonding material 50, the load applied to the contact surface between the heat sink 31 and the bonding material 50 is a 3 kgf / cm ² or more 35 kgf / cm ² or less. Then, the heating temperature of the vacuum heating is set to 400 ° C. or more and less than 548 ° C. and held for 5 minutes or more and 240 minutes or less to perform solid phase diffusion bonding, and the metal layer 13 and the bonding material 50, and the heat sink 31 and the bonding material 50 are combined. The copper layer 40 is formed by bonding (heat sink bonding step S12). In the present embodiment, the surfaces of the metal layer 13 and the bonding material 50 and the heat sink 31 and the bonding material 50 to be bonded are solid-phase diffusion bonded after the scratches on the surfaces have been removed and smoothed in advance. ing.

  In addition, the more desirable temperature range of vacuum heating comprises the metal (4NAl) which comprises the aluminum plate 23, the metal (Cu) which comprises the joining material 50, and the metal (A6063) which comprises the heat sink 31, and the joining material 50. The eutectic temperature of the metal (Cu) is in the range from the lowest eutectic temperature (not including the eutectic temperature) to the eutectic temperature of −5 ° C.

In this way, the power module substrate 30 with a heat sink according to the present embodiment is obtained.
Then, the semiconductor element 3 is placed on one side (surface) of the circuit layer 12 via a solder material, and soldered in a reduction furnace (semiconductor element joining step S13).
Thus, the power module 1 with a heat sink which is this embodiment is produced.

According to the power module substrate 30 with heat sink that is the present embodiment configured as described above, the heat sink 31 composed of the metal layer 13 composed of 4NAl and A6063 is bonded to the copper layer 40 by solid phase diffusion bonding. Therefore, when a heat cycle is applied, it is possible to suppress the occurrence of peeling at the bonding interface between the metal layer 13 and the copper layer 40 and the bonding interface between the heat sink 31 and the copper layer 40, thereby increasing the thermal resistance. It can suppress and can improve joint reliability.
In addition, a copper layer 40 made of Cu having good thermal conductivity is formed between the metal layer 13 and the heat sink 31, and heat from the semiconductor element 3 is spread in the in-plane direction of the copper layer 40 to improve efficiency. Therefore, it is possible to reduce the initial thermal resistance.

  Furthermore, the first diffusion layer 41 and the second diffusion layer 42 made of Cu and Al are formed at the bonding interface between the metal layer 13 and the copper layer 40 and at the bonding interface between the heat sink 31 and the copper layer 40. Al (aluminum atom) in the metal layer 13 and Cu (copper atom) in the copper layer 40 and Al in the heat sink 31 and Cu in the copper layer 40 are sufficiently interdiffused, The copper layer 40 and the heat sink 31 and the copper layer 40 are firmly bonded.

Moreover, since the 1st diffused layer 41 and the 2nd diffused layer 42 are set as the structure which laminated | stacked the several intermetallic compound along the said joining interface, it can suppress that a brittle diffused layer grows large. Further, when Al in the metal layer 13 and Cu in the copper layer 40 are interdiffused, an intermetallic compound suitable for each composition is formed in layers from the metal layer 13 side to the copper layer 40 side. For this reason, the characteristics in the vicinity of the bonding interface can be stabilized. Furthermore, since Al in the heat sink 31 and Cu in the copper layer 40 are interdiffused, an intermetallic compound suitable for each composition is formed in layers from the heat sink 31 side to the copper layer 40 side. The characteristics in the vicinity of the bonding interface can be stabilized.
Specifically, the first diffusion layer 41 and the second diffusion layer 42 are in order of the three phases of the θ phase 43, the η2 phase 44, and the ζ2 phase 45 from the metal layer 13 and the heat sink 31 side to the copper layer 40 side. Since the intermetallic compound is laminated, the volume fluctuation inside the first diffusion layer 41 and the second diffusion layer 42 is reduced, and the internal strain is suppressed.

  Further, since the oxides 46 are dispersed in layers along the bonding interface between the first diffusion layer 41 and the copper layer 40, and the second diffusion layer 42 and the copper layer 40, the metal layer 13 and the heat sink The oxide film formed on the surface of 31 is reliably destroyed, and the mutual diffusion of Cu and Al is sufficiently advanced, so that the metal layer 13 and the copper layer 40 and the heat sink 31 and the copper layer 40 are surely formed. It is joined to.

  Furthermore, since the average thickness of the first diffusion layer 41 and the second diffusion layer 42 is in the range of 1 μm to 80 μm, preferably in the range of 5 μm to 80 μm, the Al in the metal layer 13 and the copper layer 40 Cu in the heat sink 31 and Cu in the copper layer 40 are sufficiently interdiffused, and the metal layer 13 and the copper layer 40 and the heat sink 31 and the copper layer 40 are firmly bonded. In addition, the first diffusion layer 41 and the second diffusion layer 42 that are fragile compared to the metal layer 13, the heat sink 31, and the copper layer 40 are prevented from growing more than necessary, and the characteristics of the bonding interface are stabilized. become.

  Furthermore, in this embodiment, the average crystal grain size of the copper layer 40 is in the range of 50 μm or more and 200 μm or less, and the average crystal grain size of the metal layer 13 and the heat sink 31 is 500 μm or more. The average crystal grain size of the heat sink 31 and the copper layer 40 is set to be relatively large. Therefore, excessive strain is not accumulated in the metal layer 13, the heat sink 31, and the copper layer 40, and the fatigue characteristics are improved. Therefore, in the heat cycle load, the bonding reliability against the thermal stress generated between the power module substrate 10 and the heat sink 31 is improved.

In this embodiment, the bonding material 50 is laminated between the metal layer 13 and the heat sink 31, and the metal layer 13 and the bonding material 50 and the heat sink 31 and the bonding material 50 are 3 kgf / cm. while loaded with ² or more 35 kgf / cm ² or less of the load, are subjected to solid phase diffusion bonding was maintained at less than 400 ° C. or higher 548 ° C.. Since solid phase diffusion bonding is performed under such conditions, solid phase diffusion can be performed in a state in which the metal layer 13 and the bonding material 50 and the heat sink 31 and the bonding material 50 are sufficiently adhered to each other. And the copper layer 40, and the heat sink 31 and the copper layer 40 are securely solid-phase diffusion bonded. Further, when solid phase diffusion bonding is performed in this manner, it is difficult for a gap to be formed between the metal layer 13 and the copper layer 40 and between the heat sink 31 and the copper layer 40, so the metal layer 13, the copper layer 40, and the heat sink 31. The thermal conductivity at the bonding interface between the copper layer 40 and the copper layer 40 can be improved, and the thermal resistance can be reduced.

  Furthermore, since solid phase diffusion bonding can be performed at a low temperature compared to the case of bonding with a brazing material, the occurrence of warpage due to the difference in thermal expansion coefficient between the power module substrate 10 and the heat sink 31 is suppressed, Thermal resistance can be reduced. In addition, the bonding interface formed by this solid phase diffusion bonding is firmly bonded, and when a heat cycle is applied, peeling is unlikely to occur and an increase in thermal resistance can be suppressed.

  Moreover, in this embodiment, since the preferable thickness of the joining material 50 is 0.05 mm or more and 3.0 mm or less, the heat which generate | occur | produces from the semiconductor element 3 is spread in the surface direction of the copper layer 40, and it is efficient. Therefore, it is possible to reduce the initial thermal resistance.

In the present embodiment, the load at the time of solid phase diffusion bonding, since there is a 3 kgf / cm ² or more 35 kgf / cm ² or less, the metal layer 13 and the copper layer 40, and the heat sink 31 and the copper layer 40 Can be satisfactorily bonded, and cracking of the ceramic substrate 11 can be suppressed.

  In the present embodiment, the preferred temperature for solid phase diffusion bonding is 400 ° C. or more and less than 548 ° C. Therefore, the diffusion between Al and Cu is promoted, and solid phase diffusion bonding can be sufficiently performed in a short time. It is possible to suppress the occurrence of a liquid phase between Al and Cu and the formation of bumps at the bonding interface or the variation in thickness.

  In addition, since a more preferable heating temperature in the solid phase diffusion bonding is in a range from the eutectic temperature (not including the eutectic temperature) to the eutectic temperature of −5 ° C., a liquid phase is not formed, and a compound of aluminum and copper Is not generated, the reliability of solid phase diffusion bonding is improved, and the diffusion rate during solid phase diffusion bonding is high, so that solid phase diffusion bonding can be performed in a relatively short time.

  In addition, when solid-phase diffusion bonding is performed, if there are scratches on the surfaces to be bonded, gaps may occur during solid-phase diffusion bonding, but the bonding between the metal layer 13 and the bonding material 50 and the heat sink 31 and the bonding material 50 may occur. Since the surfaces to be processed are solid-phase diffusion bonded after the scratches on the surfaces have been removed and smoothed in advance, it is possible to perform bonding while suppressing the formation of a gap at each bonding interface.

  In the present embodiment, the metal layer 13 and the heat sink 31 are bonded by solid phase diffusion bonding via the bonding material 50, and no solder is interposed between the metal layer 13 and the heat sink 31. In addition, it is possible to improve the bonding reliability during a heat cycle load, and to suppress an increase in thermal resistance. Moreover, since the solder which is inferior in heat conductivity compared with aluminum and copper is not interposed, the heat conductivity in the junction part of the metal layer 13 and the heat sink 31 can be improved.

  Since the power module with heat sink 1 according to this embodiment includes the power module substrate 30 with heat sink as described above, the initial thermal resistance is low, and an increase in thermal resistance is suppressed even during a heat cycle load. It is possible to improve the stability of the operation of the semiconductor element.

  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.

  In the above embodiment, the circuit layer and the metal layer formed on one surface and the other surface of the ceramic substrate have been described as a rolled sheet of pure aluminum having a purity of 99.99%. However, the present invention is not limited to this. In other words, it may be 99% pure aluminum (2NAl), aluminum alloy, or the like. The circuit layer may be a pure copper plate or a copper alloy plate in addition to a pure aluminum plate or an aluminum alloy plate.

  In the above embodiment, the heat sink is made of A6063 (Al—Mg—Si). However, the heat sink may be made of pure aluminum or another Al alloy.

  Moreover, although said embodiment demonstrated the case where the copper layer was comprised with the copper plate of oxygen-free copper, it is not limited to this, You may be comprised with the copper plate of other pure copper or copper alloy. .

In the above embodiment, the ceramic substrate made of AlN is used as the insulating layer. However, the present invention is not limited to this, and a ceramic substrate made of Si ₃ N ₄ or Al ₂ O ₃ is used. Alternatively, the insulating layer may be made of an insulating resin.

  Moreover, although said heat sink demonstrated the case where the heat sink was not provided with the radiation fin, you may provide the radiation fin.

(Example)
Below, the result of the confirmation experiment performed in order to confirm the effect of this invention is demonstrated.
According to the procedure described in the flow chart of FIG. 5, solid phase diffusion bonding was performed under the conditions of a load of 9 kgf / cm ² , a temperature of 540 ° C., and 90 minutes to produce power modules with heat sinks of Invention Examples 1 to 4.
The ceramic substrate was made of AlN, and had a size of 40 mm × 40 mm and a thickness of 0.635 mm.
In the inventive example 1-3, the circuit layer is composed of a 4NAl rolled plate, and has a size of 37 mm × 37 mm and a thickness of 0.6 mm. In Invention Example 4, an oxygen-free copper plate having a size of 37 mm × 37 mm and a thickness of 0.6 mm was used.
The metal layer was composed of a 4NAl rolled plate, and was 37 mm × 37 mm and having a thickness of 0.6 mm.
The joining material was formed of an oxygen-free copper rolled plate, and a 37 mm × 37 mm member was used. The thickness of the bonding material was set as shown in Table 1.
The heat sink was composed of a rolled plate of A6063 alloy, and a 50 mm × 50 mm, 5 mm thick one was used.
Further, the solid phase diffusion bonding was performed in a range where the pressure in the vacuum heating furnace was 10 ⁻⁶ Pa or more and 10 ⁻³ Pa or less.
As the semiconductor element, an IGBT element having a size of 12.5 mm × 9.5 mm and a thickness of 0.25 mm was used.

Moreover, the following power module with a heat sink was produced as the prior art example 1.
An aluminum plate (37 mm × 37 mm, thickness 0.6 mm) as a circuit layer, a ceramic substrate (40 mm × 40 mm, thickness 0.635 mm) made of AlN, and an aluminum plate (37 mm × 37 mm, thickness) as a metal layer 0.6 mm) is placed through a brazing foil of Al-10% by mass Si, charged in a stacking direction at a pressure of 5 kgf / cm ² , and placed in a vacuum heating furnace at 30 ° C. at 30 ° C. Bonding was performed by partial heating to produce a power module substrate. Next, the power module substrate and a heat sink (A6063 alloy rolled plate, 50 mm × 50 mm, thickness 5 mm) were joined via Sn—Ag—Cu solder. And the IGBT element (12.5 mm x 9.5 mm, thickness 0.25 mm) was soldered using Sn-Ag-Cu solder, and the power module with a heat sink was created.

Next, as a conventional example 2, the following power module with a heat sink was produced.
An aluminum plate (37 mm × 37 mm, thickness 0.6 mm) as a circuit layer, a ceramic substrate (40 mm × 40 mm, thickness 0.635 mm) made of AlN, and an aluminum plate (37 mm × 37 mm, thickness) as a metal layer 0.6 mm) is placed through a brazing foil of Al-10% by mass Si, charged in a stacking direction at a pressure of 5 kgf / cm ² , and placed in a vacuum heating furnace at 30 ° C. at 30 ° C. Bonding was performed by partial heating to produce a power module substrate. Next, the power module substrate and a heat sink (A6063 alloy rolled plate, 50 mm × 50 mm, thickness 5 mm) were joined together through a brazing foil of Al-10 mass% Si. And the IGBT element (12.5 mm x 9.5 mm, thickness 0.25 mm) was soldered using Sn-Ag-Cu solder, and the power module with a heat sink was created.

(Measurement of average crystal grain size)
After performing cross-section polisher (SM-09010 manufactured by JEOL Ltd.), ion etching is performed on the cross-section of the obtained laminated plate with an ion acceleration voltage of 5 kV, a processing time of 14 hours, and a protrusion amount from the shielding plate of 100 μm. The average crystal grain size of the copper plate and the aluminum plate in the vicinity of the bonding interface was measured. The average crystal grain size was measured according to the cutting method described in JIS H 0501.
(Measurement method of oxide)
Using a cross section polisher (SM-09010, manufactured by JEOL Ltd.), a scanning electron microscope (Carl Zeiss) was used for the ion-etched section with an ion acceleration voltage of 5 kV, a processing time of 14 hours, and a protrusion amount from the shielding plate of 100 μm. When an In-Lens image was taken with an acceleration voltage of 1 kV and a WD of 2.5 mm using an NTTRA ULTRA 55), a white contrast dispersed in layers along the interface between Cu and the intermetallic compound layer was obtained. Further, when an ESB image was taken under the same conditions, the location was darker than Al. Furthermore, oxygen was concentrated in the said location from EDS analysis. From the above, it was confirmed that the oxide was dispersed in a layered manner along the interface at the interface between Cu and the intermetallic compound layer.
The average crystal grain size and the oxide were measured at the bonding interface between the metal layer and the bonding material.

(Heat cycle test)
The heat cycle test uses TSB-51 manufactured by Espec Co., Ltd., and the test piece (power module with heat sink) is in a liquid phase (−40 ° C. × 5 minutes ← → 125 ° C. × 5). 3000 cycles of minutes were performed.
And the thermal resistance (initial thermal resistance) of the power module with a heat sink before a heat cycle test and the thermal resistance of the power module with a heat sink after a heat cycle test were measured.

(Thermal resistance evaluation)
The thermal resistance was measured as follows. A heater chip was used as a semiconductor element, the heater chip was heated with 100 W of power, and the temperature of the heater chip was measured using a thermocouple. Further, the temperature of the cooling medium (ethylene glycol: water = 9: 1) flowing through the heat sink was measured. And the value which divided the temperature difference of a heater chip | tip and the temperature of a cooling medium with electric power was made into thermal resistance.
The results of the above evaluation are shown in Table 1.

In Invention Examples 1 to 4, it was confirmed that the power module with a heat sink had a low initial thermal resistance, a small increase in thermal resistance after the heat cycle test, and high reliability.
In Conventional Example 1, the initial thermal resistance was low, but cracks occurred in the solder in the heat cycle test, and the increase in thermal resistance after the heat cycle test was large.
In Conventional Example 2, warpage occurred when the power module substrate and the heat sink were joined by brazing, cracks were generated at the joint, and the initial thermal resistance was increased. Also, the increase in thermal resistance after the heat cycle test was large.

DESCRIPTION OF SYMBOLS 1 Power module 3 with a heat sink Semiconductor element 10 Power module substrate 11 Ceramic substrate 12 Circuit layer 13 Metal layer 30 Power module substrate with heat sink 31 Heat sink 40 Copper layer 41 First diffusion layer (diffusion layer)
42 Second diffusion layer (diffusion layer)
46 Oxide

Claims (7)

An insulating layer, a circuit layer formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, a heat sink disposed on the other surface side of the insulating layer, A power module substrate with a heat sink comprising:
The metal layer and the heat sink are made of Al or Al alloy,
Between the metal layer and the heat sink, a copper layer made of a bonding material composed of Cu or Cu alloy is formed,
A substrate for a power module with a heat sink, wherein the metal layer and the heat sink are solid-phase diffusion bonded to the copper layer. A diffusion layer made of Al and Cu is formed at the bonding interface between the metal layer and the copper layer and the bonding interface between the heat sink and the copper layer.
The diffusion layer has a structure in which a plurality of intermetallic compounds are laminated along the bonding interface,
2. The power module substrate with a heat sink according to claim 1, wherein an oxide is dispersed in a layered manner along the bonding interface at a bonding interface between the diffusion layer and the copper layer.   The heat sink according to claim 1 or 2, wherein an average crystal grain size of the copper layer is in a range of 50 µm or more and 200 µm or less, and an average crystal grain size of the metal layer is 500 µm or more. Power module board.   4. The power module substrate with a heat sink according to claim 1, wherein a thickness of the bonding material is 0.05 mm or more and 3.0 mm or less. 5.   A power module with a heat sink, comprising: the power module substrate with a heat sink according to any one of claims 1 to 4; and a semiconductor element bonded to one side of the circuit layer. . An insulating layer, a circuit layer formed on one surface of the insulating layer, a metal layer formed on the other surface of the insulating layer, a heat sink disposed on the other surface side of the insulating layer, A method for manufacturing a power module substrate with a heat sink comprising:
A metal layer forming step of forming a metal layer composed of Al or an Al alloy on the other surface of the insulating layer;
A heat sink joining step for joining a heat sink made of Al or Al alloy with a bonding material made of Cu or Cu alloy interposed on the other surface side of the insulating layer, and
In the heat sink bonding step, the metal layer and the bonding material, and the heat sink and the bonding material are solid-phase diffusion bonded, and a method for manufacturing a power module substrate with a heat sink. In the heat sink joining step,
With respect to the heat sink and the metal layer in a state loaded with 3 kgf / cm ² or more 35 kgf / cm ² or less of a load, by holding less than 400 ° C. or higher 548 ° C., the bonding material and the metal layer, and wherein The method for manufacturing a power module substrate with a heat sink according to claim 6, wherein the heat sink and the bonding material are solid phase diffusion bonded.

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