WO2019082973A1 - Bonded body, insulated circuit board with heat sink, and heat sink - Google Patents

Abstract

An aluminum alloy member (31) is configured from an aluminum alloy in which Mg concentration is within a range of 0.4-7.0 mass% and Si concentration is less than 1 mass%, and the aluminum alloy member (31) and a copper member (13B) are bonded with solid phase diffusion bonding. At the bonding interface between the aluminum alloy member (31) and the copper member (13B), a compound layer (40) is formed which is configured from: a first intermetallic compound layer (41) comprising a θ phase of a Cu and Al intermetallic compound, arranged on the side of the aluminum alloy member (31); a second intermetallic compound layer (42) comprising a γ2 phase of a Cu and Al intermetallic compound, arranged on the side of the copper member (13B); and a Cu-Al-Mg layer (43) formed between the first intermetallic compound layer (41) and the second intermetallic compound layer (42).

Description

Bonding body, insulated circuit board with heat sink, and heat sink

In the present invention, a heat sink is joined to a joined body in which an aluminum alloy member made of aluminum alloy and a copper member made of copper or copper alloy are joined, and an insulating circuit board having a circuit layer formed on one side of the insulating layer. The present invention relates to an insulated circuit board with a heat sink, and a heat sink in which a copper member layer is formed on a heat sink body.
Priority is claimed on Japanese Patent Application No. 2017-208318, filed Oct. 27, 2017, and Japanese Patent Application No. 2018-98468, filed Oct. 22, 2018, the present application The contents are incorporated herein.

In a semiconductor device such as an LED or a power module, a semiconductor element is bonded on a circuit layer made of a conductive material.
In the case of a power semiconductor element for large power control used to control a wind power generation, an electric car, a hybrid car, etc., the calorific value is large, and as a substrate mounting this, for example, aluminum nitride (AlN), alumina An insulating circuit board comprising a ceramic substrate made of (Al ₂ O ₃ ) or the like and a circuit layer formed by bonding a metal plate having excellent conductivity to one surface of the ceramic substrate has been widely used conventionally. It is done. In addition, what formed the metal layer in the other surface of the ceramic substrate as a board | substrate for power joules is also provided.

For example, in the power module shown in Patent Document 1, an insulating circuit board in which a circuit layer and a metal layer made of aluminum or aluminum alloy are formed on one surface and the other surface of a ceramic substrate, and a solder material on this circuit layer And a semiconductor element bonded via the semiconductor device.
A heat sink is bonded to the metal layer side of the insulated circuit board, and the heat transferred from the semiconductor element to the insulated circuit board is dissipated to the outside through the heat sink.
By the way, when a circuit layer and a metal layer are comprised with aluminum or aluminum alloy like the power module described in patent document 1, since the oxide film of Al is formed in the surface, a semiconductor element is made by a solder material. And heat sinks can not be joined.

Therefore, Patent Document 2 proposes an insulated circuit board in which the circuit layer and the metal layer have a laminated structure of an Al layer and a Cu layer. In this insulated circuit board, the Cu layer is disposed on the surface of the circuit layer and the metal layer, so that the semiconductor element and the heat sink can be favorably joined using a solder material. Therefore, the thermal resistance in the stacking direction is reduced, and heat generated from the semiconductor element can be efficiently transferred to the heat sink side.
In addition, as shown to this patent document 2, the thing of the structure which uses a heat sink as a heat sink and screws this heat sink to a cooling part by a fastening screw is also proposed.

Further, in Patent Document 3, one of the metal layer and the heat sink is made of aluminum or an aluminum alloy, and the other is made of copper or a copper alloy, and the metal layer and the heat sink are solid phase diffusion bonded. Insulated circuit boards with heat sinks have been proposed. In this insulated circuit board with a heat sink, the metal layer and the heat sink are in solid phase diffusion bonding, so the thermal resistance is small and the heat dissipation characteristics are excellent.

Further, Patent Document 4 proposes an insulated circuit board with a heat sink in which a heat sink made of an aluminum alloy having a Si concentration of 1 mass% to 25 mass% and a metal layer made of copper are solid phase diffusion bonded. In addition, a heat sink has been proposed in which a heat sink main body made of an aluminum alloy having a Si concentration of 1 mass% to 25 mass% and a metal member layer made of copper are solid phase diffusion bonded.

Patent No. 3171234 JP, 2014-160799, A JP, 2014-099596, A JP, 2016-208010, A

By the way, as described in Patent Document 2-4, when solid-phase diffusion bonding an aluminum member made of aluminum or an aluminum alloy and a copper member made of copper or a copper alloy, the aluminum member and the copper member An intermetallic compound layer composed of copper and aluminum is formed at the bonding interface of Here, as an intermetallic compound composed of copper and aluminum, there are a plurality of phases as shown in FIG. Therefore, the intermetallic compound layer formed at the bonding interface between the aluminum member and the copper member has a structure in which each phase such as θ phase, _{2 2} phase, ζ ₂ phase, δ phase, and γ ₂ phase is stacked. There is.
Here, since the _{2 2} phase, the ζ ₂ phase, and the δ phase are relatively hard, there is a problem that when the heating and cooling cycle is applied, the metal compound layer is cracked to increase the thermal resistance and decrease the bonding rate. there were.

The present invention has been made in view of the above-mentioned circumstances, and even when solid-phase diffusion bonding an aluminum member made of aluminum or an aluminum alloy and a copper member made of copper or a copper alloy, A joined body capable of suppressing formation of a relatively hard intermetallic compound layer at the interface, and suppressing rise in thermal resistance and decrease in bonding rate during cold thermal cycle load, insulation with a heat sink provided with this joined body It aims at providing a circuit board and a heat sink.

In order to solve the above-described problems, the bonded body of the present invention is a bonded body in which an aluminum alloy member made of an aluminum alloy and a copper member made of copper or a copper alloy are bonded, and the aluminum alloy member is It is made of an aluminum alloy in which the Mg concentration is in the range of 0.4 mass% to 7.0 mass% and the Si concentration is less than 1 mass%, and the aluminum alloy member and the copper member are solid phase diffusion bonded And a compound layer formed by diffusion of metal atoms of the aluminum alloy member and Cu atoms of the copper member at a bonding interface between the aluminum alloy member and the copper member, and the compound layer is formed of the aluminum A first intermetallic compound layer formed of the θ phase of an intermetallic compound of Cu and Al disposed on the alloy member side, and gold of Cu and Al disposed on the copper member side A second intermetallic compound layer formed of gamma ₂ phase during compounds are those with Cu-Al-Mg layer formed between the first intermetallic compound layer and the second intermetallic compound layer, in configuration It is characterized by

According to the joined body of this configuration, a compound layer formed by diffusion of metal atoms of the aluminum alloy member and Cu atoms of the copper member is provided, and the compound layer is disposed on the aluminum alloy member side. a first intermetallic compound layer comprising a θ phase intermetallic compound of Cu and Al was, the copper member second intermetallic compound consisting of gamma ₂ phase intermetallic compound of disposed the Cu and Al in the side layer and Since the Cu-Al-Mg layer formed between the first intermetallic compound layer and the second intermetallic compound layer is formed, the Cu-Al-Mg layer is formed between Cu and Al. By suppressing the growth of the compound layer, relatively hard η ₂ phase, ζ ₂ phase and δ phase are not formed, and it is possible to suppress the occurrence of cracking of the compound layer when the thermal cycle is applied. .

Here, in the bonded body of the present invention, a magnesium oxide film may be formed on the bonding surface of the aluminum alloy member.
In this case, the diffusion of Al atoms can be suppressed by the magnesium oxide film, and the growth of the intermetallic compound can be suppressed more than necessary. Thereby, the occurrence of cracking of the compound layer can be further suppressed when the heating and cooling cycle is applied.

Further, in the bonded body of the present invention, the magnesium oxide film preferably has crystalline particles.
In this case, the strength of the magnesium oxide film is improved, and the bonding strength can be further improved.

The insulating circuit substrate with a heat sink according to the present invention comprises an insulating layer, a circuit layer formed on one side of the insulating layer, a metal layer formed on the other side of the insulating layer, and the insulation of the metal layer A heat sink provided with a heat sink disposed on the side opposite to the layer, wherein the bonding surface of the metal layer to the heat sink is made of copper or a copper alloy; The bonding surface with the metal layer is made of an aluminum alloy having an Mg concentration of 0.4 mass% or more and 7.0 mass% or less and an Si concentration of less than 1 mass%, and the heat sink and the metal layer And a solid-phase diffusion bonded compound layer formed by diffusion of metal atoms of the aluminum alloy and Cu atoms of the copper member at the bonding interface between the heat sink and the metal layer. The compound layer includes a first intermetallic compound layer composed of a θ phase of an intermetallic compound of Cu and Al disposed on the heat sink side, and an intermetallic compound of Cu and Al disposed on the metal layer side. a second intermetallic compound layer formed of gamma ₂ phase compound, and Cu-Al-Mg layer is formed between these first intermetallic compound layer and the second intermetallic compound layer, in that it is constituted It is characterized by

According to the insulating circuit substrate with a heat sink of this configuration, a compound layer formed by diffusion of metal atoms of the aluminum alloy and Cu atoms of the copper member is provided at the bonding interface between the heat sink and the metal layer, The compound layer includes a first intermetallic compound layer formed of the θ phase of an intermetallic compound of Cu and Al disposed on the heat sink side, and an intermetallic compound of Cu and Al disposed on the metal layer side. Since it is composed of the second intermetallic compound layer consisting of γ ₂ phase and the Cu-Al-Mg layer formed between the first intermetallic compound layer and the second intermetallic compound layer, Cu When the growth of the intermetallic compound layer of Cu and Al is suppressed by the -Al-Mg layer, relatively hard η ₂ phase, ζ ₂ phase, and δ phase are not formed, and the cold heat cycle is applied. Suppress the occurrence of compound layer cracking can do.

Here, in the insulating circuit substrate with a heat sink of the present invention, a magnesium oxide film may be formed on the bonding surface of the heat sink.
In this case, the diffusion of Al atoms can be suppressed by the magnesium oxide film, and the growth of the intermetallic compound can be suppressed more than necessary. Thereby, the occurrence of cracking of the compound layer can be further suppressed when the heating and cooling cycle is applied.

In the insulating circuit substrate with a heat sink according to the present invention, the magnesium oxide film preferably has crystalline particles.
In this case, the strength of the magnesium oxide film is improved, and the bonding strength can be further improved.

The heat sink according to the present invention is a heat sink comprising a heat sink body and a copper member layer made of copper or a copper alloy joined to the heat sink body, and the heat sink body has an Mg concentration of 0.4 mass% or more. The heat sink main body and the copper member layer are solid-phase diffusion bonded, and the heat sink main body and the copper member are made of an aluminum alloy having a Si concentration of less than 1 mass%, and the solid content is diffusion bonded. A compound layer formed by diffusion of metal atoms of the heat sink body and Cu atoms of the copper member layer is provided at a bonding interface with the layer, and the compound layer is formed of Cu disposed on the heat sink body side. a first intermetallic compound layer comprising a θ phase intermetallic compound of Al, from gamma ₂ phase intermetallic compound of the copper disposed member layer side has been Cu and Al That a second intermetallic compound layer, is characterized in that the Cu-Al-Mg layer is formed, in being configured between these first intermetallic compound layer and the second intermetallic compound layer.

According to the heat sink of this configuration, a compound layer formed by diffusion of metal atoms of the heat sink body and Cu atoms of the copper member layer is provided at the bonding interface between the heat sink body and the copper member layer, The compound layer includes a first intermetallic compound layer formed of the θ phase of an intermetallic compound of Cu and Al disposed on the heat sink main body side, and an intermetallic compound of Cu and Al disposed on the copper member layer side. a second intermetallic compound layer formed of gamma ₂ phase is a Cu-Al-Mg layer formed between these first intermetallic compound layer and the second intermetallic compound layer, a configuration and Therefore, the growth of the intermetallic compound layer of Cu and Al is suppressed by the Cu-Al-Mg layer, and the relatively hard η ₂ phase, ζ ₂ phase, and δ phase are not formed, and the cold thermal cycle is applied. Suppress the occurrence of cracks in the metal compound layer can do.

Here, in the heat sink of the present invention, a magnesium oxide film may be formed on the bonding surface of the heat sink body.
In this case, the diffusion of Al atoms can be suppressed by the magnesium oxide film, and the growth of the intermetallic compound can be suppressed more than necessary. Thereby, the occurrence of cracking of the compound layer can be further suppressed when the heating and cooling cycle is applied.

In the heat sink of the present invention, preferably, the magnesium oxide film has crystalline particles.
In this case, the strength of the magnesium oxide film is improved, and the bonding strength can be further improved.

According to the present invention, even when solid-phase diffusion bonding an aluminum member made of aluminum or an aluminum alloy and a copper member made of copper or a copper alloy, a relatively hard intermetallic compound layer is formed at the bonding interface Can be suppressed, and it is possible to provide a bonded body capable of suppressing an increase in thermal resistance and a decrease in bonding rate during a thermal cycle load, and an insulated circuit board and a heat sink provided with this heat sink. Become.

It is a binary phase diagram of Cu and Al. It is a schematic explanatory drawing of the power module provided with the insulated circuit board with a heat sink which concerns on 1st embodiment of this invention. FIG. 3 is an enlarged cross-sectional view of a bonding interface between a heat sink and a metal layer (Cu layer) of the insulating circuit board with a heat sink shown in FIG. 2; It is a flowchart explaining the manufacturing method of the insulation circuit board with a heat sink concerning a first embodiment. It is a schematic explanatory drawing of the manufacturing method of the insulated circuit board with a heat sink which concerns on 1st embodiment. It is a schematic explanatory drawing of the heat sink which concerns on 2nd embodiment of this invention. FIG. 7 is an enlarged cross-sectional view of a bonding interface between a heat sink main body and a copper member layer of the heat sink shown in FIG. 6. It is a flowchart explaining the manufacturing method of the heat sink concerning a second embodiment. It is a schematic explanatory drawing of the manufacturing method of the heat sink which concerns on 2nd embodiment. It is a schematic explanatory drawing of the power module provided with the insulated circuit board with a heat sink which is other embodiment of this invention. It is a schematic explanatory drawing which shows the condition which performs solid phase diffusion bonding by a current-flow heating method. In Example 2, it is a photograph in which an observation result of a magnesium oxide film of the present invention example 16 is shown.

First Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
The power module 1 using the insulated circuit board 30 with a heat sink which is 1st embodiment of this invention in FIG. 2 is shown.
The power module 1 includes an insulated circuit board 30 with a heat sink, and a semiconductor element 3 joined to one surface (upper surface in FIG. 2) of the insulated circuit board 30 with a heat sink via a solder layer 2. .
The insulating circuit board 30 with a heat sink includes an insulating circuit board 10 and a heat sink 31 joined to the insulating circuit board 10.

Insulating circuit substrate 10 is provided on ceramic substrate 11 forming the insulating layer, circuit layer 12 disposed on one surface (upper surface in FIG. 2) of ceramic substrate 11, and on the other surface of ceramic substrate 11. And the metal layer 13.

The ceramic substrate 11 is made of a ceramic such as silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), or alumina (Al ₂ O ₃ ), which is excellent in insulation and heat dissipation. In the present embodiment, the ceramic substrate 11 is made of aluminum nitride (AlN) which is particularly excellent in heat dissipation. The thickness of the ceramic substrate 11 is set, for example, in the range of 0.2 to 1.5 mm, and in the present embodiment, it is set to 0.635 mm.

As shown in FIG. 5, the circuit layer 12 is formed by bonding an aluminum plate 22 made of aluminum or an aluminum alloy to one surface of the ceramic substrate 11. In the present embodiment, in the circuit layer 12, a rolled plate (aluminum plate 22) of aluminum (2N aluminum) having a purity of 99 mass% or more or aluminum (4N aluminum) having a purity of 99.99 mass% or more is bonded to the ceramic substrate 11. It is formed by being done. In addition, the thickness of the aluminum plate 22 used as the circuit layer 12 is set in the range of 0.1 mm or more and 1.0 mm or less, and is set to 0.6 mm in this embodiment.

As shown in FIG. 2, the metal layer 13 is laminated on an Al layer 13A disposed on the other surface of the ceramic substrate 11 and a surface of the Al layer 13A opposite to the surface to which the ceramic substrate 11 is joined. And the Cu layer 13B.
As shown in FIG. 5, the Al layer 13A is formed by bonding an aluminum plate 23A made of aluminum or an aluminum alloy to the other surface of the ceramic substrate 11. In the present embodiment, in the Al layer 13A, a rolled plate (aluminum plate 23A) of aluminum (2N aluminum) having a purity of 99 mass% or more or aluminum (4N aluminum) having a purity of 99.99 mass% or more is bonded to the ceramic substrate 11. It is formed by being done. The thickness of the aluminum plate 23A to be joined is set in the range of 0.1 mm or more and 3.0 mm or less, and in the present embodiment, it is set to 0.6 mm. As shown in FIG. 5, the Cu layer 13B is formed by bonding a copper plate 23B made of copper or a copper alloy to the other surface of the Al layer 13A. In the present embodiment, the Cu layer 13B is formed by bonding a rolled plate (copper plate 23B) of oxygen-free copper. The thickness of the Cu layer 13B is set in the range of 0.1 mm or more and 6 mm or less, and is set to 1 mm in the present embodiment.

The heat sink 31 is for dissipating the heat on the side of the insulating circuit board 10. In the present embodiment, as shown in FIG. 2, a flow path 32 through which a cooling medium flows is provided. The heat sink 31 is made of an aluminum alloy in which the Mg concentration is in the range of 0.4 mass% to 7.0 mass% and the Si concentration is less than 1 mass%. In addition, in this aluminum alloy, it is preferable that Si concentration is less than 1 mass%, and precipitation Si is absent. The Si-containing intermetallic compound may be precipitated.

Here, the heat sink 31 and the metal layer 13 (Cu layer 13B) are in solid phase diffusion bonding.
As shown in FIG. 3, a compound layer 40 is formed at the bonding interface between the metal layer 13 (Cu layer 13 </ b> B) and the heat sink 31. The compound layer 40 is formed by mutual diffusion of the metal atoms of the heat sink 31 and the Cu atoms of the metal layer 13 (Cu layer 13B).

And this compound layer 40 is, as shown in FIG. 3, a first intermetallic compound layer 41 consisting of the θ phase of an intermetallic compound of Cu and Al disposed on the heat sink 31 side, and a metal layer 13 (Cu layer 13B) A second intermetallic compound layer 42 composed of a γ ₂ phase of an intermetallic compound of Cu and Al disposed on the side, and between the first intermetallic compound layer 41 and the second intermetallic compound layer 42 And the formed Cu—Al—Mg layer 43.

In the present embodiment, the Cu-Al-Mg layer 43 is made of Cu ₆ Al ₅ Mg ₂ which is an intermetallic compound of Cu, Al and Mg, or CuAl ₂ Mg, Cu ₃ Al ₇ Mg ₆ , CuAlMg, etc. It is done.
Further, Mg of the Cu—Al—Mg layer 43 is a diffusion of Mg contained in the aluminum alloy constituting the heat sink 31. For this reason, a Mg-depleted Mg-depleted layer is formed in the vicinity of the bonding interface of the heat sink 31.

Here, the thickness of the compound layer 40 is set in the range of 10 μm to 70 μm, preferably in the range of 15 μm to 40 μm.
The thickness of the Cu-Al-Mg layer 43 is set in the range of 1 μm to 45 μm, preferably in the range of 2.5 μm to 30 μm.

A magnesium oxide film may be formed on the bonding surface of the heat sink 31 at the bonding interface between the heat sink 31 and the metal layer 13 (Cu layer 13B). The magnesium oxide film is formed by reacting an alumina film formed on the surface of the heat sink 31 with Mg of the heat sink 31 (aluminum alloy).
This magnesium oxide film is composed of MgO or MgAl ₂ O ₄ . The magnesium oxide film preferably has crystalline particles. The reaction of the alumina film with Mg is sufficiently progressed by the presence of the crystalline particles, since the amorphous particles of the alumina film react with Mg to form crystalline particles. Become.

Next, a method of manufacturing the insulated circuit board 30 with a heat sink according to the present embodiment will be described with reference to FIGS. 4 and 5.

(Aluminum sheet lamination process S01)
First, as shown in FIG. 5, an aluminum plate 22 to be the circuit layer 12 is laminated on one surface of the ceramic substrate 11 through the brazing foil 26 of Al—Si system.
Further, it is laminated on the other surface of the ceramic substrate 11 through the aluminum plate 23A to be the Al layer 13A and the brazing material foil 26 of Al-Si system. In the present embodiment, an Al-8 mass% Si alloy foil having a thickness of 10 μm is used as the brazing material foil 26 of the Al-Si system.

(Circuit layer and Al layer forming step S02)
Then, it is placed in a vacuum heating furnace in a state of being pressurized (pressure 1 to 35 kgf / cm ² (0.1 to 3.5 MPa)) in the stacking direction and heated to bond the aluminum plate 22 and the ceramic substrate 11. The circuit layer 12 is formed. Further, the ceramic substrate 11 and the aluminum plate 23A are joined to form an Al layer 13A.
Here, the pressure in the vacuum heating furnace is in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, the heating temperature is in the range of 600 ° C. to 650 ° C., and the holding time at the heating temperature is 15 minutes to 180 minutes It is preferable to set in the range of

(Cu layer (metal layer) forming step S03)
Next, a copper plate 23B to be the Cu layer 13B is stacked on the other surface side of the Al layer 13A.
And it arranges in a vacuum heating furnace and heats in the state pressurized (pressure 3-35kgf / cm ² (0.3-3.5MPa)) in the lamination direction, solid phase diffusion of Al layer 13A and copper plate 23B Bonding to form a metal layer 13.
Here, the pressure in the vacuum heating furnace is in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, the heating temperature is in the range of 400 ° C. to 548 ° C., and the holding time at the heating temperature is 5 minutes to 240 minutes It is preferable to set in the range of
The respective bonding surfaces of the Al layer 13A and the copper plate 23B to be subjected to solid phase diffusion bonding are smoothed by removing the flaws of the surfaces in advance.

(Metal layer / heat sink bonding step S04)
Next, the metal layer 13 (Cu layer 13B) and the heat sink 31 are stacked, and in the vacuum heating furnace in a state in which pressure (pressure 5 to 35 kgf / cm ² (0.5 to 3.5 MPa)) is applied in the stacking direction. The metal layer 13 (Cu layer 13B) and the heat sink 31 are solid phase diffusion bonded by arranging and heating. The bonding surfaces of the metal layer 13 (Cu layer 13B) and the heat sink 31 to be bonded by solid phase diffusion bonding are smoothed by removing the flaws of the surfaces in advance.
Here, the pressure in the vacuum heating furnace is in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, the heating temperature is in the range of 400 ° C. to 520 ° C., and the holding time at the heating temperature is 30 minutes to 240 minutes It is preferable to set in the range of

In this metal layer / heat sink bonding step S04, the Cu atoms in the Cu layer 13B and the Al atoms and Mg atoms in the heat sink 31 mutually diffuse, and as shown in FIG. 3, the first intermetallic compound layer 41 and Cu—Al A compound layer 40 composed of the -Mg layer 43 and the second intermetallic compound layer 42 is formed.
A magnesium oxide film may be formed on the surface portion of the heat sink 31 at the bonding interface between the heat sink 31 and the metal layer 13 (Cu layer 13B). Further, in the case of the magnesium oxide film, the reaction between the alumina film and Mg is promoted by the high heating temperature of the metal layer / heat sink bonding step S04 and the long holding time, and the amorphous to crystalline state is obtained. Will change.
In this manner, the heat sink equipped insulated circuit board 30 according to the present embodiment is manufactured.

(Semiconductor element bonding step S05)
Next, the semiconductor element 3 is stacked on one surface (surface) of the circuit layer 12 via a solder material, and soldered in a reduction furnace.
As described above, the power module 1 according to the present embodiment is manufactured.

According to the insulated circuit board 30 with a heat sink according to the present embodiment configured as described above, the Al atom of the aluminum alloy that constitutes the heat sink 31 at the bonding interface between the heat sink 31 and the metal layer 13 (Cu layer 13B) And Mg atoms and Cu atoms of the metal layer 13 (Cu layer 13B) are mutually diffused to form a compound layer 40. The compound layer 40 is formed of Cu disposed on the heat sink 31 side. A first intermetallic compound layer 41 composed of the θ phase of the intermetallic compound of Al, and a second intermetallic compound composed of γ ₂ phase of the intermetallic compound of Cu and Al disposed on the metal layer 13 (Cu layer 13B) side Since the compound layer 42 and the Cu-Al-Mg layer 43 formed between the first intermetallic compound layer 41 and the second intermetallic compound layer 42, the Cu-Al-Mg layer is formed. By 43 It suppressed the growth of intermetallic compounds, relatively hard eta _2-phase, zeta _2-phase, no δ-phase is formed, it is possible to suppress the occurrence of cracking of the compound layer 40 at the time loaded with thermal cycle.

Further, in the present embodiment, since the thickness of the compound layer 40 is 10 μm or more, Cu atoms and Al atoms are sufficiently interdiffused, and the heat sink 31 and the metal layer 13 (Cu layer 13B) Solid phase diffusion bonding can be ensured.
Furthermore, in the present embodiment, since the thickness of the compound layer 40 is 70 μm or less, the intermetallic compound does not grow more than necessary, and the occurrence of cracking or the like in the compound layer 40 can be suppressed. .

Further, in the present embodiment, since the thickness of the Cu—Al—Mg layer 43 is 1 μm or more, the growth of the intermetallic compound can be reliably suppressed.
Furthermore, in the present embodiment, since the thickness of the Cu-Al-Mg layer 43 is 45 μm or less, the growth of the intermetallic compound is not inhibited more than necessary, and the heat sink 31 and the metal layer 13 (Cu layer 13B Solid phase diffusion bonding).

Further, in the present embodiment, when the magnesium oxide film is formed on the bonding surface of the heat sink 31, the diffusion of Al atoms can be suppressed by the magnesium oxide film, and the intermetallic compound grows more than necessary. Can be suppressed. Thereby, the occurrence of cracking of the compound layer 40 can be further suppressed when the thermal cycling is applied.
Furthermore, when the magnesium oxide film has crystalline granules, the strength of the magnesium oxide film is improved, and the bonding strength between the heat sink 31 and the metal layer 13 (Cu layer 13B) is further improved. It becomes possible.

Second Embodiment
Next, a heat sink according to a second embodiment of the present invention will be described. FIG. 6 shows a heat sink 101 according to a second embodiment of the present invention.
The heat sink 101 includes a heat sink main body 110 and a copper member layer 117 made of copper or a copper alloy laminated on one surface (upper side in FIG. 6) of the heat sink main body 110. In the present embodiment, as shown in FIG. 9, the copper member layer 117 is configured by bonding a copper plate 127 made of a rolled plate of oxygen free copper.

The heat sink body 110 is provided with a flow path 111 through which the cooling medium flows. The heat sink body 110 is made of an aluminum alloy in which the Mg concentration is in the range of 0.4 mass% to 7.0 mass%, and the Si concentration is less than 1 mass%. In this aluminum alloy, the Si concentration is less than 1 mass%, and Si is considered to be solid-solved in the matrix phase.

Here, the heat sink body 110 and the copper member layer 117 are bonded by solid phase diffusion.
As shown in FIG. 7, a compound layer 140 containing Al and Cu is formed at the bonding interface between the heat sink main body 110 and the copper member layer 117. The compound layer 140 is formed by mutual diffusion of the metal atoms of the heat sink body 110 and the Cu atoms of the copper member layer 117.

Then, as shown in FIG. 7, the compound layer 140 includes the first intermetallic compound layer 141 composed of the θ phase of the intermetallic compound of Cu and Al disposed on the heat sink main body 110 side, and the copper member layer 117 side. Formed between the first intermetallic compound layer 141 and the second intermetallic compound layer 142, and the second intermetallic compound layer 142 composed of the γ ₂ phase of the intermetallic compound of Cu and Al disposed in And a Cu-Al-Mg layer 143.

In the present embodiment, the Cu-Al-Mg layer 143 is made of Cu ₆ Al ₅ Mg ₂ which is an intermetallic compound of Cu, Al and Mg, or CuAl ₂ Mg, Cu ₃ Al ₇ Mg ₆ , CuAlMg, etc. It is done.
Further, Mg of the Cu—Al—Mg layer 143 is a diffusion of Mg contained in the aluminum alloy constituting the heat sink main body 110. For this reason, in the vicinity of the bonding interface of the heat sink body 110, a Mg-depleted Mg-depleted layer is formed.

In the present embodiment, the magnesium oxide film 112 is formed on the surface portion of the heat sink body 110 at the bonding interface between the heat sink body 110 and the copper member layer 117.
The magnesium oxide film 112 is formed by the reaction of the alumina film formed on the surface of the heat sink body 110 with Mg of the heat sink body 110 (aluminum alloy).

Here, the magnesium oxide film 112 is made of MgO or MgAl ₂ O ₄ .
The magnesium oxide film preferably has crystalline particles. The reaction of the alumina film with Mg is sufficiently progressed by the presence of the crystalline particles, since the amorphous particles of the alumina film react with Mg to form crystalline particles. Become.

Next, a method of manufacturing the heat sink 101 according to the present embodiment will be described with reference to FIGS. 8 and 9.

(Heat sink heat treatment step S101)
First, heat treatment is performed on the heat sink main body 110 to be bonded, and the magnesium oxide film 112 is formed on the surface of the heat sink main body 110. The heat treatment conditions at this time are as follows: atmosphere: vacuum or nitrogen atmosphere in a range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, heat treatment temperature: 250 ° C. to 400 ° C., holding time at heat treatment temperature: 10 minutes to 30 minutes It is said below.

(Heat sink body / copper member layer bonding step S102)
Next, as shown in FIG. 9, the heat sink body 110 and the copper plate 127 to be the copper member layer 117 are laminated, and pressure is applied in the laminating direction (pressure 5 to 35 kgf / cm ² (0.5 to 3.5 MPa)) The copper plate 127 and the heat sink main body 110 are solid phase diffusion bonded by placing and heating in a vacuum heating furnace in the above state. The bonding surfaces of the copper plate 127 and the heat sink main body 110 to be subjected to solid phase diffusion bonding are smoothed by removing the flaws of the surfaces in advance.
Here, the pressure in the vacuum heating furnace is in the range of 10 ⁻⁶ Pa to 10 ⁻³ Pa, the heating temperature is in the range of 450 ° C. to 520 ° C., and the holding time at the heating temperature is 30 minutes to 240 minutes It is preferable to set in the range of

In this heat sink main body / copper member layer bonding step S102, the Cu atoms in the copper plate 127 and the Al atoms and Mg atoms in the heat sink main body 110 mutually diffuse, and as shown in FIG. A compound layer 140 composed of the Al—Mg layer 143 and the second intermetallic compound layer 142 is formed.
Thus, the heat sink 101 according to the present embodiment is manufactured.

According to the heat sink 101 according to the present embodiment configured as described above, the copper member layer 117 is formed by joining the copper plate 127 made of a rolled sheet of oxygen-free copper on one surface side of the heat sink body 110 Therefore, the heat can be spread in the surface direction by the copper member layer 117, and the heat dissipation characteristics can be significantly improved. In addition, other members and the heat sink 101 can be joined well by using solder or the like.

Then, in the present embodiment, as shown in FIG. 7, at the bonding interface between the heat sink main body 110 and the copper member layer 117, at the bonding interface between the heat sink main body 110 and the copper member layer 117 The compound layer 140 is formed by diffusion of Mg atoms and Cu atoms constituting the copper member layer 117. The compound layer 140 is an intermetallic compound of Cu and Al disposed on the heat sink main body 110 side. a first intermetallic compound layer 141 made of θ phase, and the second intermetallic layer 142 consisting of gamma ₂ phase intermetallic compound of disposed the Cu and Al in the copper member layer 117 side, these first metal Since the Cu—Al—Mg layer 143 formed between the intermetallic compound layer 141 and the second intermetallic compound layer 142, the intermetallic compound is formed of the Cu—Al—Mg layer 143. The growth of suppression, relatively hard eta _2-phase, zeta _2-phase, no δ-phase is formed, it is possible to suppress the occurrence of cracking of the compound layer 140 in the case loaded with thermal cycle.

Furthermore, in the present embodiment, since the magnesium oxide film 112 is formed on the surface of the heat sink body 110, diffusion of Al atoms can be suppressed by the magnesium oxide film 112, and the intermetallic compound is more than necessary. Growth can be further suppressed.
Further, when the magnesium oxide film 112 has crystalline particles, the strength of the magnesium oxide film 112 is improved, and the bonding strength between the heat sink main body 110 and the copper member layer 117 is improved. Become.

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, in the first embodiment, although the metal layer 13 is described as having the Al layer 13A and the Cu layer 13B, the present invention is not limited to this, and as shown in FIG. Or you may comprise by a copper alloy. In the insulating circuit substrate 230 with a heat sink shown in FIG. 10, a copper plate is joined to the other surface (lower side in FIG. 10) of the ceramic substrate 11 by DBC method or active metal brazing method, and is made of copper or copper alloy. A metal layer 213 is formed. The metal layer 213 and the heat sink 31 are solid phase diffusion bonded. In the insulating circuit board 210 shown in FIG. 10, the circuit layer 212 is also made of copper or a copper alloy.

In the first embodiment, the circuit layer is described as being formed by bonding an aluminum plate having a purity of 99 mass%, but the present invention is not limited to this. Pure aluminum having a purity of 99.99 mass% or more It may be composed of other aluminum or other metal such as aluminum alloy, copper or copper alloy. Also, the circuit layer may have a two-layer structure of an Al layer and a Cu layer. The same applies to the insulating circuit board 210 shown in FIG.

Further, in the metal layer / heat sink bonding step S04 of the first embodiment, the metal layer 13 (Cu layer 13B) and the heat sink 31 are stacked and placed in a vacuum heating furnace in a state of being pressurized in the stacking direction. In the heat sink main body / copper member layer bonding step S102 of the second embodiment, the heat sink main body 110 and the copper plate 127 to be the copper member layer 117 are stacked, and pressure is applied in the stacking direction (pressure 5 to 35 kgf). Although the configuration has been described in which the inside of the vacuum heating furnace is placed and heated in a state of 0.5 cm ³ / cm ² (0.5 to 3.5 MPa), the present invention is not limited thereto. As shown in FIG. Even when solid-phase diffusion bonding is performed on the alloy member 301 (heat sink 31, heat sink body 110) and the copper member 302 (metal layer 13, copper member layer 117), the electric heating method is applied. There.

When conducting heating, as shown in FIG. 11, an aluminum alloy member 301 and a copper member 302 are laminated, and these laminated bodies are laminated by a pair of electrodes 312 and 312 via carbon plates 311 and 311. The pressure is applied in the direction, and the aluminum alloy member 301 and the copper member 302 are energized. Then, the carbon plates 311 and 311, the aluminum alloy member 301, and the copper member 302 are heated by Joule heat, and the aluminum alloy member 301 and the copper member 302 are solid phase diffusion bonded.

In the above-described electric heating method, since the aluminum alloy member 301 and the copper member 302 are directly heated by electric current, the temperature rising rate can be made relatively fast, for example, 30 to 100 ° C./min. Diffusion bonding can be performed. As a result, the influence of oxidation on the bonding surface is small, and bonding can be performed even in, for example, an air atmosphere. Further, depending on the resistance value or specific heat of the aluminum alloy member 301 and the copper member 302, it is also possible to join the aluminum alloy member 301 and the copper member 302 in a state where a temperature difference occurs, thereby reducing the difference in thermal expansion. Thermal stress can also be reduced.

Here, in the electric heating method described above, pressure load by the pair of electrodes 312 and 312 is preferably in the range of 30 kgf / cm ² or more 100 kgf / cm ² or less (3 MPa or 10MPa or less).
In the case of applying the electric heating method, the surface roughness of the aluminum alloy member 301 and the copper member 302 is 0.3 μm or more and 0.6 μm or less in arithmetic average roughness Ra, or 1. in the maximum height Rz. It is preferable to set it in the range of 3 micrometers or more and 2.3 micrometers or less. In normal solid phase diffusion bonding, the surface roughness of the bonding surface is preferably small, but in the case of electric heating, if the surface roughness of the bonding surface is too small, the interfacial contact resistance decreases and the bonding interface is Since it becomes difficult to heat locally, it is preferable to set it in the above-mentioned range.

In addition, although it is also possible to use the above-mentioned electric heating method for metal layer / heat sink joining process S04 of 1st embodiment, since the ceramic substrate 11 is an insulator in that case, for example, jig etc. which consist of carbon etc. It is necessary to short-circuit the carbon plates 311, 311. The bonding conditions are the same as the bonding of the aluminum alloy member 301 and the copper member 302 described above.
The surface roughness of the metal layer 13 (Cu layer 13B) and the heat sink 31 is the same as in the case of the aluminum alloy member 301 and the copper member 302 described above.

Below, the result of the confirmation experiment performed in order to confirm the effect of this invention is demonstrated.

Example 1
On one side of the aluminum alloy plate (50 mm × 50 mm, thickness 5 mm) shown in Table 1, a copper plate (40 mm × 40 mm, thickness 5 mm) made of oxygen free copper was solid phaseed by the method described in the above embodiment. Diffusion bonded. In the invention examples 6 and 7, the heat treatment was performed on the aluminum alloy plate, and then solid phase diffusion bonding was performed with the copper plate.
In Inventive Example 1-7 and Comparative Example 1-3, the aluminum plate and the metal plate are pressed in the stacking direction with a load of 15 kgf / cm ² (1.5 MPa), and the condition of 500 ° C. × 180 min in a vacuum heating furnace Solid phase diffusion bonding was performed.

(Structure of compound layer)
The cross-section of the solid-phase diffusion bonded aluminum alloy plate-metal plate assembly was observed, and the structure of the compound layer formed at the bonding interface was evaluated as follows. The evaluation results are shown in Table 1.

(Layer structure)
The electron diffraction pattern was analyzed using a transmission electron microscope (Fita Titan ChemiSTEM, accelerating voltage 200 kV), the composition was analyzed using energy dispersive X-ray analysis (NSS7 manufactured by Thermo Scientific Co., Ltd.), and the formed layer was Were determined. The electron diffraction pattern was obtained by irradiation with an electron beam narrowed to about 1 nm (NBD method).

(Cool cycle test)
Next, a thermal cycle test was performed on the thus-produced bonded body. Using a TSA-72 ES manufactured by ESPEC Co., Ltd., a heat cycle was carried out 2500 times at a temperature of -50 ° C for 45 minutes and at 175 ° C for 45 minutes on a test piece (power module with a heat sink) .
Then, the thermal resistance and bonding rate in the stacking direction of the bonded body before the thermal cycle test, and the thermal resistance and bonding rate in the stacking direction of the bonded body after the thermal cycle test were evaluated as follows.

(Evaluation of bonding rate)
The bonding rate of the bonding portion between the aluminum plate and the metal plate of the bonded body was evaluated using an ultrasonic flaw detector, and calculated from the following equation. Here, the initial bonding area is the area to be bonded before bonding, that is, the area of the aluminum plate. Since peeling is indicated by a white portion in the ultrasonic flaw detection image, the area of this white portion is regarded as a peeling area. The evaluation results are shown in Table 1.
Bonding ratio (%) = {(initial bonding area)-(peeling area)} / (initial bonding area) x 100

(Measurement of thermal resistance)
The heater chip (13 mm × 10 mm × 0.25 mm) was soldered to the surface of the metal plate, and the aluminum alloy plate was brazed to the cooler. Next, the heater chip was heated at a power of 100 W, and the temperature of the heater chip was measured using a thermocouple. Moreover, the temperature of the cooling medium (ethylene glycol: water = 9: 1) which distribute | circulates a cooler was measured. Then, a value obtained by dividing the difference between the temperature of the heater chip and the temperature of the cooling medium by the power was taken as the thermal resistance.
In addition, the heat resistance was evaluated by the ratio with this comparative example 1 on the basis of the thermal resistance before the heat cycle test of the comparative example 1 as a reference. The evaluation results are shown in Table 1.

In Comparative Example 1 in which the Si concentration of the aluminum alloy plate is 6.0 mass% and the Mg concentration is 12.7 mass%, the θ phase and the Mg-Si phase exist in the compound layer, and the bonding after the cold thermal cycle is performed. The rate was low and the thermal resistance increased.
In Comparative Example 2 in which the Mg concentration of the aluminum alloy plate is 0.1 mass%, η ₂ phase, ζ ₂ phase, and δ phase, which are intermetallic compounds of Cu and Al, are formed in the compound layer, and the thermal cycle is The subsequent bonding rate was low, and the thermal resistance increased.
In Comparative Example 3 in which the Mg concentration of the aluminum alloy plate was 10.3 mass%, the bonding ratio after the cold thermal cycle was low, and the thermal resistance was large. The thick Cu-Al-Mg phase in the compound layer inhibits the growth of the intermetallic compound more than necessary, the thickness of the intermetallic compound layer becomes uneven, and the hardness of the aluminum alloy plate increases. It is presumed that the stress load on the interface is increased, which causes a crack.

On the other hand, according to the example of the present invention, the Cu-Al-Mg phase was properly formed in the compound layer, and the bonding ratio was high before and after the thermal cycle, and the thermal resistance could be suppressed small. .

From the above, according to Invention Example 1-7, the aluminum member made of aluminum alloy and the copper member made of copper or copper alloy are solid phase diffusion bonded, and a relatively hard intermetallic compound layer is formed at the bonding interface. It has been confirmed that a conjugate can be provided that can be inhibited from being formed.

Example 2
On one side of the aluminum alloy plate (10 mm × 10 mm, thickness 3 mm) shown in Table 2, a copper plate (2 mm × 2 mm, thickness 1 mm) made of oxygen free copper was solid phase by the method described in the above embodiment. Diffusion bonded. The aluminum plate and the metal plate were pressed in the stacking direction with a load of 15 kgf / cm ² (1.5 MPa), and solid phase diffusion bonding was performed at the temperature and holding time shown in Table 2.

The layer structure of the compound layer formed at the bonding interface was confirmed in the same manner as in Example 1 for the obtained bonded body. As a result, each of Invention Examples 11 to 22 had a layer structure of “θ / Cu—Al—Mg / γ ₂ ”.
Further, the presence or absence of a magnesium oxide film, the presence or absence of particles in the magnesium oxide film, and bonding strength (shear strength) were evaluated as follows.

(Existence of magnesium oxide film / presence of amorphous oxide film / presence of granular material)
Measurement was performed at a magnification of 60000 using a transmission electron microscope (Titanium ChemiSTEM manufactured by FEI, acceleration voltage 200 kV), Cu, Al, Mg and O were measured by energy dispersive X-ray analysis (NSS7 manufactured by Thermo Scientific Co.) The elemental mapping of was obtained. A region in which Mg and O are present in the same region in the region in which Cu and Al are present is referred to as a magnesium oxide layer. And the presence or absence of the granular body in a magnesium oxide film was confirmed. The observation results of the magnesium oxide film of Inventive Example 16 are shown in FIG.
In addition, an electron diffraction pattern was obtained by a nanobeam diffraction method (NBD method) using an electron beam narrowed to 1 nm. When the electron diffraction pattern had a halo pattern, the amorphous oxide film was judged to be "present".

(Joining strength)
The shear strength (shear strength) was measured by the share test. When the aluminum alloy plate is horizontally fixed with the copper plate on top, and the copper plate is pressed horizontally from the side with a shear tool (share speed 0.1 mm / sec), the bond between the copper plate and the aluminum alloy plate is broken The strength and location of failure (fracture mode) were confirmed. In addition, intensity | strength carried out the shear strength test of 20 times, and made it the average value. The evaluation results are shown in Table 2.

It was confirmed that the bonding strength is further improved by the high bonding temperature and the long holding time. The alumina film formed on the surface of the aluminum alloy plate and the Mg of the aluminum alloy plate react to form a magnesium oxide film, and it is presumed that the proportion of crystalline particles is increased in this magnesium oxide film. Be done.

According to the present invention, even when solid-phase diffusion bonding an aluminum member made of aluminum or an aluminum alloy and a copper member made of copper or a copper alloy, a relatively hard intermetallic compound layer is formed at the bonding interface Can be suppressed, and it is possible to provide a bonded body capable of suppressing an increase in thermal resistance and a decrease in bonding rate during a thermal cycle load, and an insulated circuit board and a heat sink provided with this heat sink. Become.

10, 210 Insulated Circuit Board 11 Ceramics Board 13, 213 Metal Layer 13B Cu Layer (Copper Member)
31 Heatsink (Aluminum alloy member)
40 compound layer 41 first intermetallic compound layer 42 second intermetallic compound layer 43 Cu-Al-Mg layer 101 heat sink 110 heat sink main body (aluminum alloy member)
117 Copper Member Layer 140 Compound Layer 141 First Intermetallic Compound Layer 142 Second Intermetallic Compound Layer 143 Cu-Al-Mg Layer

Claims (9)

1. A joined body in which an aluminum alloy member made of an aluminum alloy and a copper member made of copper or a copper alloy are joined,
   The aluminum alloy member is made of an aluminum alloy having a Mg concentration of 0.4 mass% or more and 7.0 mass% or less and a Si concentration of less than 1 mass%, and the aluminum alloy member and the copper member Solid phase diffusion bonding,
   The bonding interface of the aluminum alloy member and the copper member is provided with a compound layer formed by diffusion of metal atoms of the aluminum alloy member and Cu atoms of the copper member,
   This compound layer is composed of a first intermetallic compound layer consisting of a θ phase of an intermetallic compound of Cu and Al disposed on the aluminum alloy member side, and an intermetallic compound of Cu and Al disposed on the copper member side. a second intermetallic compound layer formed of gamma ₂ phase compound, and Cu-Al-Mg layer is formed between these first intermetallic compound layer and the second intermetallic compound layer, in that it is constituted Characteristic junction body.
2. The joined body according to claim 1, wherein a magnesium oxide film is formed on a joining surface of the aluminum alloy member.
3. The joined body according to claim 2, wherein the magnesium oxide film has crystalline particles.
4. An insulating layer, a circuit layer formed on one side of the insulating layer, a metal layer formed on the other side of the insulating layer, and a surface of the metal layer opposite to the insulating layer A heat sink and an insulated circuit board having the heat sink,
   The bonding surface of the metal layer to the heat sink is made of copper or a copper alloy,
   The bonding surface of the heat sink to the metal layer is made of an aluminum alloy in which the Mg concentration is in the range of 0.4 mass% to 7.0 mass% and the Si concentration is less than 1 mass%,
   Solid phase diffusion bonding of the heat sink and the metal layer;
   The bonding interface between the heat sink and the metal layer includes a compound layer formed by diffusion of metal atoms of the aluminum alloy and Cu atoms of the copper member,
   The compound layer includes a first intermetallic compound layer formed of the θ phase of an intermetallic compound of Cu and Al disposed on the heat sink side, and an intermetallic compound of Cu and Al disposed on the metal layer side. wherein a second intermetallic compound layer formed of gamma ₂ phase, and Cu-Al-Mg layer is formed between these first intermetallic compound layer and the second intermetallic compound layer, in that it is constituted An insulated circuit board with a heat sink.
5. The insulating circuit board with a heat sink according to claim 4, wherein a magnesium oxide film is formed on a bonding surface of the heat sink.
6. The said magnesium oxide film | membrane has a crystalline granular material, The insulated circuit board with a heat sink of Claim 5 characterized by the above-mentioned.
7. A heat sink comprising: a heat sink body; and a copper member layer made of copper or a copper alloy joined to the heat sink body,
   The heat sink body is made of an aluminum alloy in which the Mg concentration is in the range of 0.4 mass% or more and 7.0 mass% or less, and the Si concentration is less than 1 mass%,
   The heat sink body and the copper member layer are bonded by solid phase diffusion bonding,
   The bonding interface between the heat sink body and the copper member layer is provided with a compound layer formed by diffusion of metal atoms of the heat sink body and Cu atoms of the copper member layer,
   This compound layer is composed of a first intermetallic compound layer composed of a θ phase of an intermetallic compound of Cu and Al disposed on the heat sink main body side, and an intermetallic compound of Cu and Al disposed on the copper member layer side. a second intermetallic compound layer formed of gamma ₂ phase compound, and Cu-Al-Mg layer is formed between these first intermetallic compound layer and the second intermetallic compound layer, in that it is constituted Heatsink characterized by
8. The heat sink according to claim 7, wherein a magnesium oxide film is formed on a bonding surface of the heat sink body.
9. The heat sink according to claim 8, wherein the magnesium oxide film has crystalline particles.

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