Multilayer laminate, semiconductor device using the same, and manufacturing methods thereof

Abstract

The present invention suppresses warpage through low-temperature bonding when forming a multilayer assembly, such as when bonding a heat sink to an insulated circuit board.　A multilayer assembly according to the present invention comprises: a ceramic substrate; a first aluminum plate that is bonded to one surface of the ceramic substrate and contains aluminum or an aluminum alloy; a first intermediate metal layer that is bonded to the reverse side of the first aluminum plate from the ceramic substrate and contains any one of copper, nickel, silver, and gold; a first copper sintered layer bonded to the reverse side of the first intermediate metal layer from the first aluminum plate; and a first metal member that is bonded to the reverse side of the first copper sintered layer from the first intermediate metal layer and contains any one of aluminum, an aluminum alloy, copper, and a copper alloy.

Description

Technical Field

[0001] The present invention relates to a multi-layer bonded body in which a metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy is bonded to an aluminum plate joined to a ceramic substrate with a copper bonding material, which can be used as an insulating circuit board, a semiconductor device using the same, and a method for manufacturing these multi-layer bonded bodies and semiconductor devices. This application claims priority based on Japanese Patent Application No. 2022-114292 filed in Japan on July 15, 2022, and Japanese Patent Application No. 2023-110428 filed in Japan on July 5, 2023, the contents of which are incorporated herein by reference.

Background Art

[0002] An insulating circuit board on which electronic components such as LEDs and power elements are mounted is provided with a heat sink for dissipating heat generated by the electronic components.

[0003] In this case, a ceramic substrate is also known as an insulating circuit board. A circuit layer is formed on one surface of the ceramic substrate serving as an insulating layer, and a heat dissipation layer is formed on the other surface of the ceramic substrate. A heat sink having excellent thermal conductivity is joined to the heat dissipation layer via a brazing material, and an electronic component is mounted on the circuit layer via a soldering material, thereby obtaining an insulating circuit board with a heat sink.

[0004] In such an insulating circuit board with a heat sink, the aluminum plate of the insulating circuit board and the heat sink are joined at a high temperature such as 600°C.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] Conventionally, when joining an insulating circuit board and a heat sink at a high temperature, warping is likely to occur due to the difference in thermal expansion between the ceramic substrate with a low coefficient of thermal expansion and the heat sink during the cooling process. Therefore, it is desirable to join the insulating circuit board and the heat sink at a low temperature. Not only for heat sinks, but also when joining a copper plate for a circuit layer or the like to one aluminum plate of an insulating circuit board, if the heating temperature is high, warping due to the difference in thermal expansion may occur during cooling, resulting in a possible decrease in joinability.

[0007] Patent Document 1 discloses a power module using an insulating circuit board with copper plates joined to both sides of a ceramic substrate. In this power module, a heat dissipation base plate made of copper or the like is joined to the copper plate of the insulating circuit board with a joining material. In Patent Document 1, since copper plates are joined to both sides of an insulating substrate made of ceramics, a large warping may occur due to the difference in the coefficient of thermal expansion, resulting in a possible decrease in joinability.

[0008] Therefore, an object of the present invention is to suppress warping and improve joinability by joining at a low temperature when forming a multi-layer joined body, such as when joining a heat sink to an insulating circuit board.

Means for Solving the Problems

[0009] [Multi-layer joined body] The multi-layer joined body of the present invention includes a ceramic substrate, a first aluminum plate containing aluminum or an aluminum alloy joined to one surface of the ceramic substrate, a first intermediate metal layer joined to the surface of the first aluminum plate opposite to the ceramic substrate and containing any one of copper, nickel, silver, and gold, a first copper sintered layer joined to the surface of the first intermediate metal layer opposite to the first aluminum plate, and a first metal member joined to the surface of the first copper sintered layer opposite to the first intermediate metal layer and containing any one of aluminum, an aluminum alloy, copper, and a copper alloy.

[0010] In the multi-layer joined body of the present invention, the first metal member contains aluminum or an aluminum alloy, and a second intermediate metal layer containing any one of copper, nickel, silver, and gold may be formed between the first metal member and the first copper sintered layer.

[0011] In the multi-layer joined body of the present invention, a second aluminum plate made of aluminum or an aluminum alloy may be joined to the other surface of the ceramic substrate.

[0012] In the multi-layer joined body of the present invention, a third intermediate metal layer containing any one of copper, nickel, silver, and gold, which is joined to the surface of the second aluminum plate opposite to the ceramic substrate, a second copper sintered layer joined to the surface of the third intermediate metal layer opposite to the second aluminum plate, and a second metal member joined to the surface of the second copper sintered layer opposite to the second aluminum plate and containing any one of aluminum, an aluminum alloy, copper, and a copper alloy may be further provided.

[0013] In the multi-layer joined body of the present invention, the second metal member contains aluminum or an aluminum alloy, and a fourth intermediate metal layer containing any one of copper, nickel, silver, and gold may be formed between the second metal member and the second copper sintered layer.

[0014] In the present invention, the "first metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy" means that at least the joint surface of the first metal member on the side of the first copper sintered layer is not any one of aluminum, an aluminum alloy, copper, and a copper alloy, and the first metal member may be configured as a composite material or a laminated material, for example. Further, the "first metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy" also targets the case where the first metal member is any one of aluminum, an aluminum alloy, copper, and a copper alloy.

[0015] In the multi-layer laminate of the present invention, a first intermediate metal layer formed on the surface of a first aluminum plate and a first metal member are joined with a first copper sintered layer interposed therebetween. This first copper sintered layer is a copper sintered layer formed by sintering copper particles. This first copper sintered layer may be formed by sintering a copper paste, or may be formed by sintering a joining sheet formed by connecting a plurality of copper particles with a binder into a sheet shape, or may be formed by sintering a copper sintered sheet formed by partially sintering copper particles into a sheet shape.

[0016] The first copper sintered layer using the joining sheet is obtained by sintering a sheet-shaped first joining material formed by connecting a plurality of copper particles with a binder. Compared with the first copper sintered layer using a copper paste, since the amount of the binder is small, generation of voids due to volatilization of organic components during sintering is suppressed, which is preferable. Further, since the first intermediate metal layer is provided, the joinability between the first aluminum plate and the first copper sintered layer is good.

[0017] In the present invention, the "first intermediate metal layer containing any one of copper, nickel, silver, and gold" means that at least the joining surface of the first intermediate metal layer on the first copper sintered layer side is any one of copper, nickel, silver, and gold. The first intermediate metal layer may be composed of, for example, a plurality of plating layers or the like. Further, the "first intermediate metal layer containing any one of copper, nickel, silver, and gold" also includes the case where the first intermediate metal layer is any one of copper, nickel, silver, and gold.

[0018] In the multi-layer laminate of the present invention, preferably, a second intermediate metal layer is formed between the first metal member and the first copper sintered layer. When the first metal member contains aluminum or an aluminum alloy, it is preferable that the second intermediate metal layer contains any one of copper, nickel, silver, and gold.

[0019] In the present invention, the "second intermediate metal layer containing any one of copper, nickel, silver, and gold" means that at least the joint surface of the second intermediate metal layer on the side of the first copper sintered layer is made of any one of copper, nickel, silver, and gold, and the second intermediate metal layer may be composed of, for example, a plurality of plating layers or the like. Further, the "second intermediate metal layer containing any one of copper, nickel, silver, and gold" also includes the case where the second intermediate metal layer is made of any one of copper, nickel, silver, and gold.

[0020] When the first metal member contains copper or a copper alloy, it is preferable that the second intermediate metal layer does not contain nickel, but it may contain nickel.

[0021] In the present invention, the fact that the second intermediate metal layer contains nickel means that at least the joint surface of the second intermediate layer on the side of the first copper sintered layer is not nickel, and the second intermediate metal layer may be composed of, for example, a plurality of plating layers or the like. Further, the fact that the second intermediate metal layer contains nickel also includes the case where the second intermediate metal layer is nickel.

[0022] By interposing the first intermediate metal layer, the joinability between the first aluminum plate and the first copper sintered layer can be enhanced. Further, by forming the second intermediate metal layer, the joinability between the first metal member and the first copper sintered layer can be enhanced.

[0023] Preferably, in the multi-layer joined body of the present invention, the first aluminum plate and the second aluminum plate are made of aluminum having a purity of 99.99 mass% or more.

[0024] Since the first aluminum plate and the second aluminum plate are made of soft high-purity aluminum with a purity of 4N (99.99% by mass) or more as defined in JIS (Japanese Industrial Standards), the yield stress is low, so high bonding reliability with the ceramic substrate in the temperature cycle can be maintained, and high thermal conductivity and high electrical conductivity with the first metal member and the like can be exhibited. There is no upper limit on the purity of aluminum, and aluminum with a purity of 99.999% by mass or so-called 6N aluminum with a purity of 99.9999% by mass may also be used.

[0025] In the multi-layer bonded body of the present invention, the sizes of the first aluminum plate, the first copper sintered layer, and the first metal member, in other words, the sizes of these bonding surfaces are not limited. For example, 100 mm 2 or more and 10,000 mm 2 or less are preferable.

[0026] Since the thickness of the first copper sintered layer in the stacking direction is 50 μm or more and 1000 μm or less, the first aluminum and the first metal member can be well bonded.

[0027] Preferably, in the multi-layer bonded body of the present invention, a plurality of groove portions are formed on the surface of the first aluminum plate opposite to the ceramic substrate.

[0028] The presence of groove portions on the surface of the first aluminum plate that is bonded to the first metal member improves the volatilization of the binder during sintering and can reduce voids in the bonded portion. Therefore, the bondability with the first metal member via the first copper sintered layer becomes good. Note that, due to bonding, the unevenness of the groove portions may be smaller after bonding than before bonding.

[0029] In the multi-layer bonded body of the present invention, an insulating circuit board having the surface of the first metal member as an electronic component mounting surface can be formed.

[0030] When a multilayer bonded body in which a second aluminum plate is bonded to a surface of a ceramic substrate opposite to a first aluminum plate is used as an insulating circuit board, the surface of the first metal member may be used as an electronic component mounting surface, or the surface of the second aluminum plate may be used as an electronic component mounting surface.

[0031] In the insulating circuit board, since the first aluminum plate and the second aluminum plate are made of soft high-purity aluminum of 4N or more, high bonding reliability with the ceramic substrate in a temperature cycle can be maintained, and high thermal conductivity and high electrical conductivity can be exhibited as the entire insulating circuit board. There is no upper limit on the purity of aluminum, and aluminum of 99.999 mass% or so-called 6N aluminum of 99.9999 mass% may be used.

[0032] When the multilayer bonded body of the present invention is used as an insulating circuit board, when the surface of the first metal member is used as an electronic component mounting surface, the second aluminum plate can be used as a heat sink. When the surface of the second aluminum plate is used as an electronic component mounting surface, the first metal member can be used as a heat sink.

[0033] [Semiconductor device] A semiconductor device can be configured using the multilayer bonded body of the present invention.

[0034] The semiconductor device of the present invention includes an electronic component mounted on a surface of the first metal member opposite to the first copper sintered layer, a lead frame connected to the electronic component, and an insulating resin that seals the electronic component in a state where at least a surface of the tip of the lead frame and the second aluminum plate opposite to the ceramic substrate is exposed.

[0035] In the semiconductor device of the present invention, it may further include an electronic component mounted on the surface of the second aluminum plate opposite to the ceramic substrate, a lead frame connected to the electronic component, and an insulating resin for encapsulating the electronic component in a state where the surface of the first metal member excluding the joint surface of the tip of the lead frame and at least the first copper sintered layer is exposed.

[0036] In a semiconductor device using a multi-layer bonded body provided with a second metal member, it may further include an electronic component mounted on the surface of the first metal member opposite to the first copper sintered layer, a lead frame connected to the electronic component, and an insulating resin for encapsulating the electronic component in a state where the surface of the second metal member excluding the joint surface of the tip of the lead frame and at least the second copper sintered layer is exposed.

[0037] [Manufacturing method of multi-layer bonded body] The manufacturing method of the multi-layer bonded body of the present invention includes a first lamination step of laminating a brazing material and a first aluminum plate containing aluminum or an aluminum alloy on one surface of a ceramic substrate to form a first laminate, a first bonding step of bonding the first laminate by pressurizing and heating it in a laminated state to form a first bonded body, an intermediate metal layer forming step of forming a first intermediate metal layer containing any one of copper, nickel, silver, and gold on the surface of the first aluminum plate in the first bonded body opposite to the ceramic substrate, a second lamination step of sequentially laminating a first bonding material formed by connecting a plurality of copper particles with a binder into a sheet shape and a first metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy on the first intermediate metal layer to form a second laminate, and a second bonding step of sintering the first bonding material by heating the second laminate in a state of being pressurized in the lamination direction to form a first copper sintered layer, and bonding the first intermediate metal layer and the first metal member in the first aluminum plate with the first copper sintered layer.

[0038] In the method for manufacturing the multilayer joined body of the present invention, the first metal member contains aluminum or an aluminum alloy. In the intermediate metal layer forming step, further, a second intermediate metal layer containing any one of copper, nickel, silver, and gold is formed on one surface of the first metal member. In the second joining step, the second intermediate metal layer may be joined to the first copper sintered layer.

[0039] By joining the first intermediate metal layer and the first metal member using the first joining material, it is possible to suppress the generation of voids due to the heating of the organic components during joining and improve the joinability. The first joining material formed in a sheet shape by connecting a plurality of copper particles with a binder may be partially sintered when formed in a sheet shape.

[0040] In the method for manufacturing the multilayer joined body of the present invention, a plurality of groove portions may be formed on the surface of the first aluminum plate opposite to the ceramic substrate before the first laminating step.

[0041] In the method for manufacturing the multilayer joined body of the present invention, in the first laminating step, a second aluminum plate containing a brazing material and aluminum or an aluminum alloy is further laminated on the other surface of the ceramic substrate to form the first laminate. In the first joining step, the first laminate including the second aluminum plate is pressurized and heated to join the first aluminum plate to one surface of the ceramic substrate and the second aluminum plate to the other surface to form the first joined body.

[0042] In the method for manufacturing the multi-layer joined body of the present invention, in the intermediate metal layer forming step, further, on the surface of the second aluminum plate in the first joined body opposite to the ceramic substrate, a third intermediate metal layer containing any one of copper, nickel, silver, and gold is formed. In the second lamination step, on the third intermediate metal layer, further, a second joining material formed by connecting a plurality of copper particles with a binder in a sheet shape and a second metal member containing any one of aluminum, aluminum alloy, copper, and copper alloy are sequentially laminated. In the second joining step, the second joining material may be further sintered to form a second copper sintered layer, and the third intermediate metal layer and the second metal member may be joined by the second copper sintered layer.

[0043] In the method for manufacturing the multi-layer joined body of the present invention, when the second metal member contains aluminum or an aluminum alloy, in the intermediate metal layer forming step, further, on one surface of the second metal member, a fourth intermediate metal layer containing any one of copper, nickel, silver, and gold is formed. In the second joining step, the surface of the fourth intermediate metal layer in the second metal member may be joined to the second copper sintered layer.

[0044] [Method for manufacturing a semiconductor device] The present invention also provides a method for manufacturing a semiconductor device using the method for manufacturing the multi-layer joined body.

[0045] The method for manufacturing a semiconductor device of the present invention is a method for manufacturing a semiconductor device using the method for manufacturing the multi-layer joined body. After the second joining step, the method further includes a mounting step of mounting an electronic component on the first metal member and connecting a lead frame to the electronic component, and a resin encapsulation step of encapsulating the electronic component with an insulating resin in a state where the tip of the lead frame and at least the surface of the second aluminum opposite to the ceramic substrate are exposed from the insulating resin.

[0046] In the method for manufacturing a semiconductor device of the present invention, between the intermediate layer forming step and the second lamination step, a mounting step of mounting an electronic component on the second aluminum plate and connecting a lead frame to the electronic component, and a resin sealing step of sealing the electronic component with the insulating resin in a state where the tip of the lead frame and at least the surface of the first intermediate metal layer are exposed from the insulating resin may be further provided.

[0047] In the method for manufacturing a semiconductor device of the present invention, in the intermediate layer forming step, further, a third intermediate metal layer containing any one of copper, nickel, silver, and gold is formed on the surface of the second aluminum plate in the first joined body on the side opposite to the ceramic substrate, after the second joining step, a mounting step of mounting an electronic component on the first metal member and connecting a lead frame to the electronic component, a resin sealing step of sealing the electronic component with the insulating resin in a state where the tip of the lead frame and at least the surface of the third intermediate metal layer are exposed from the insulating resin, a second joining material formed in a sheet shape by connecting a plurality of copper particles with a binder on the third intermediate metal layer, and a second metal member containing any one of aluminum, aluminum alloy, copper, and copper alloy are sequentially laminated to form a third laminate, a third joining step of sintering the second joining material to form a second copper sintered layer and joining the third intermediate metal layer and the second metal member with the second copper sintered layer may be further provided by heating in a state where the secondary laminate is pressed in the lamination direction.

[0048] After the mounting step and the resin sealing step, a third joining step involving pressurization and heating is performed. In this third joining step, since joining is performed at a low temperature by the second copper sintered layer, the thermal influence on the electronic component, the insulating resin, etc. can be suppressed.

Advantages of the Invention

[0049] According to the present invention, when joining a heat sink to an insulating circuit board, etc., the first metal member can be joined at a low temperature by the copper sintered layer, so warpage can be suppressed and joinability can be improved.

Brief Description of the Drawings

[0050]

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Embodiments for Carrying Out the Invention

[0051] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0052] [Configuration of Multi-Layer Joined Body 10] As shown in FIG. 1, the multi-layer joined body 10 of the first embodiment includes a ceramics substrate 11, a first aluminum plate 12 laminated on one surface of the ceramics substrate 11, a first intermediate metal layer 13 joined to the surface of the first aluminum plate 12 opposite to the ceramics substrate 11, a first copper sintered layer 14 joined to the surface of the first intermediate metal layer 13 opposite to the first aluminum plate 12, and a first metal member 15 joined to the surface of the first copper sintered layer 14 opposite to the first intermediate metal layer 13.

[0053] In the example shown in FIG. 1, the first aluminum plate 12, the first intermediate metal layer 13, the first copper sintered layer 14, and the first metal member 15 are laminated in a separated state into a plurality (two in FIG. 1, denoted by reference numerals A and B). As a result, laminated portions having the same layer structure denoted by reference numerals A and B are constructed on the ceramic substrate 11. However, they may be constructed as a single laminated portion instead of a separated state. Of course, they may be constructed as three or more laminated portions. Further, since the two illustrated laminated portions differ only in size and have the same laminated structure of the same members, the reference numerals of the respective members may be attached only to one of the laminated portions denoted by A and B (the same applies hereinafter in FIG. 3 and the like).

[0054] The ceramic substrate 11 is an insulating material and is formed of, for example, aluminum nitride (AlN), silicon nitride (Si 3 N 4 ), aluminum oxide (Al 2 O 3 ), etc., and its plate thickness is, for example, 0.2 mm to 1.2 mm.

[0055] The first aluminum plate 12 is made of pure aluminum or an aluminum alloy having a purity of 99% by mass or more. In the JIS standard, pure aluminum in the 1000 series, particularly 1N90 (purity 99.9% by mass or more: so-called 3N aluminum) or 1N99 (purity 99.99% by mass or more: so-called 4N aluminum) can be used. Its thickness is set to, for example, 0.4 mm to 1.6 mm.

[0056] The first intermediate metal layer 13 contains any one of copper, nickel, silver, and gold, and is formed in a state of being adhered to the surface of the first aluminum plate 12 by plating or the like. The first aluminum plate 12 and the first copper sintered layer 14 are joined via the first intermediate metal layer 13. When the first intermediate metal layer 13 is made of silver or gold, a nickel film may be provided as an underlayer on the first aluminum plate 12, and the first intermediate metal layer 13 may be formed thereon.

[0057] The first copper sintered layer 14 joins the first intermediate metal layer 13 and the first metal member 15, and is formed by heating and sintering a first bonding material 310 formed by connecting a plurality of copper particles 311 with a binder (solvent) 312 into a sheet shape. The details will be described later.

[0058] The first metal member 15 is made of, for example, a copper plate (copper sheet) made of copper with a purity of 99.96 mass% or more (oxygen-free copper), copper with a purity of 99.90 mass% or more (tough pitch copper), or a copper alloy, or, for example, an aluminum plate with a purity of less than 99.90 mass%. In the JIS standard, it is formed by a pure aluminum plate of so-called 2N aluminum (such as A1050, etc.) with a purity of 99.0 mass% or more, or an aluminum plate made of an aluminum alloy such as A3003, A6063, A5052, etc. The thickness of this first metal member 15 is set to, for example, 0.5 mm to 1.5 mm.

[0059] (Details of the first copper sintered layer 14) The first copper sintered layer 14 is formed by pressurizing and heating the first bonding material 310. For example, the "bonding sheet" described in Japanese Patent Application Laid-Open No. 2021-116463 filed by the applicant of the present application can be used. As shown in FIG. 2, this first bonding material 310 is composed of a plurality of copper particles 311 of 90 mass% or more and 99 mass% or less, and a solvent 312 of 1 mass% or more and 10 mass% or less.

[0060] In this case, the copper particles 311 have an average particle diameter (BET diameter) of 50 nm or more and 300 nm or less, which is converted using a true sphere model based on the specific surface area according to JIS Z 8830. After adjusting the aqueous dispersion of copper citrate to a pH (2.0 or more and 7.5 or less), a hydrazine compound is added and mixed in an inert gas atmosphere, and this mixed solution is held at a predetermined temperature (60 °C or more and 80 °C or less) in an inert gas atmosphere for (1.5 hours or more and 2.5 hours or less) to reduce the eluted copper ions to generate them. Also, the copper particles 311 are covered with a film 313 of an organic substance (derived from citric acid), and oxidation is suppressed.

[0061] The solvent 312 as a binder that connects a plurality of copper particles 311 has a boiling point of 150°C or higher and is composed of one kind of organic solvent or polymer solvent, or a composition using two or more of these. For example, a diol compound or a triol compound can be used.

[0062] When the first bonding material 310 is composed of copper particles 311 and a solvent 312, its thickness t is not limited, but for example, it may be 50 μm or more and 1000 μm or less, or 500 μm or more. Note that the first bonding material 310 is not limited to a sheet formed with all of the plurality of copper particles 311 in an unsintered state. Among the plurality of copper particles 311, those in which a part is sintered and connected and the rest are formed in a sheet shape in an unsintered state can also be used.

[0063] The first bonding material 310 is stacked on the first intermediate metal layer 13 and heated in a state of being pressed in the stacking direction. Then, the solvent 312 in the first bonding material 310 and the film 313 around the copper particles 311 volatilize, and the copper particles 311 sinter with each other to form the first copper sintered layer 14. In the first copper sintered layer 14, any of nickel, copper, gold, and silver that constitutes the first intermediate metal layer 13 is included in the interface region.

[0064] In this multi-layer bonded body 10, a first aluminum plate 12, a first intermediate metal layer 13, a first copper sintered layer 14, and a first metal member 15 are sequentially bonded in a stacked state on a ceramic substrate 11, and it can be used as an insulating circuit board with the surface 15a of the first metal member 15 as an electronic component mounting surface. In this case, for example, a heat conductive grease or the like can be applied to the surface 11b of the ceramic substrate 11 on the side opposite to the first aluminum plate 12, brought into contact with a heat sink or the like (not shown) for heat dissipation, and fixed by screwing or the like.

[0065] [Configuration of the multi-layer bonded body 16] In this multi-layer joined body 10, the case where a metal plate made of aluminum or an aluminum alloy is used as the first metal member 15 is shown in FIG. 3. As in the multi-layer joined body 16 shown in FIG. 3, on the surface of the first metal member 15 joined to the first copper sintered layer 14, similar to the first intermediate metal layer 13 of the first aluminum plate 12, a second intermediate metal layer 17 containing any one of copper, nickel, silver, and gold is formed by plating or the like, and this second intermediate metal layer 17 is joined to the first copper sintered layer 14.

[0066] When this second intermediate metal layer 17 is composed of silver or gold, it is preferable to form a nickel film as an underlayer on the first metal member 15, and form the second intermediate metal layer 17 thereon.

[0067] In these multi-layer joined bodies 10 and 16, groove portions 131 (see FIGS. 7 and 8) may be formed on the surface of the member joined by the first copper sintered layer 14. Specifically, groove portions 131 may be formed on the surface of the first aluminum plate 12 where the first intermediate metal layer 13 is formed, and on the surface of the first metal member 15 on the side of the first copper sintered layer 14 (in the multi-layer joined body 16, on the surface of the first metal member 15 where the second intermediate metal layer 17 is formed). The groove portions 131 will be described later.

[0068] [Configuration of the multi-layer joined body 20] Furthermore, based on the multi-layer joined body 10 shown in FIG. 1, as shown in FIG. 4, a multi-layer joined body 20 in which a second aluminum plate 21 made of aluminum or an aluminum alloy is joined to the other surface 11b of the ceramic substrate 11 can also be formed. When this multi-layer joined body 20 is used as an insulating circuit board, the second aluminum plate 21 can be used as a heat sink.

[0069] This second aluminum plate 21 preferably has the same plate thickness as the first aluminum plate 12 or a plate thickness with a slight difference, but in order to increase the heat capacity as a heat sink, it may be thicker than the first aluminum plate 12 or formed with a larger area.

[0070] [Manufacturing method of the multi-layer joined body 20] A method for manufacturing the multilayer laminate 20 shown in Fig. 4 will be described.

[0071] Among the processes shown in the flowchart of Fig. 5, the processes in the range indicated by E are the processes for manufacturing the multilayer laminate 20. That is, the manufacturing method includes a first lamination step of laminating a first aluminum plate 12 and a second aluminum plate 21 on a ceramic substrate 11 via a brazing material 41 and a brazing material 42, respectively, to form a first laminate 50; a first joining step of joining the first laminate 50 by applying pressure and heat to form a first joined body 51; an intermediate metal layer forming step of forming a first intermediate metal layer 13 on the surface of the first aluminum plate 12 of the first joined body 51 opposite to the ceramic substrate 11; a second lamination step of sequentially laminating a first joining material 310 and a first metal member 15 on the first intermediate metal layer 13 to form a second laminate 52; and a second joining step of sintering the first joining material 310 to form a first copper sintered layer 14, thereby joining the first intermediate metal layer 13 and the first metal member 15. Hereinafter, these steps will be described in this order.

[0072] Fig. 5 shows the steps from mounting electronic components and the like on the manufactured multilayer laminate 20 and resin-sealing to manufacturing a semiconductor device after the steps indicated by E for manufacturing the multilayer laminate 20. The manufacturing method of this semiconductor device will be described later.

[0073] (First Lamination Step) As shown in Fig. 6, a first laminate 50 is formed by laminating a first aluminum plate 12 on one surface 11a of a ceramic substrate 11 and a second aluminum plate 21 on the other surface 11b via a brazing material 41 and a brazing material 42, respectively. As the brazing materials 41 and 42, Al-Si-based, Al-Ge-based, Al-Cu-based, Al-Mg-based, Al-Mn-based, or Al-Si-Mg-based brazing materials are used. These brazing materials 41 and 42 may be supplied as foils or as pastes.

[0074] As described above, when forming the groove portion 131 on the surface of the first aluminum plate 12 on the side of the first copper sintered layer 14, as shown in FIGS. 7 and 8 (a cross-sectional view taken along the line G-G), with respect to the rectangular surface 12a of the first aluminum plate 12, the groove portion 131 is formed from one side to the other side, and since the groove portions 131 are formed parallel to each other, the surface 12a of the first aluminum plate 12 is formed in a concavo-convex shape. The groove portion 131 is formed, for example, with a V-shaped cross section in a cross-sectional view.

[0075] Each groove portion 131 is formed with the same dimensions. For example, assuming that the pitch of the groove portion 131 is a [mm], the depth of the groove portion 131 is b [mm], the width of the groove portion 131 is c [mm], and the width of the flat portion 132 provided between the groove portions 131 is d [mm], a relationship of a > d > c ≧ b is set. Thereby, when the surface 12a of the first aluminum plate 12 is viewed in a plan view, the area s2 occupied by the flat portion 132 is set to be larger (s2 > s1) than the area s1 occupied by the groove portion 131.

[0076] The groove portion 131 is formed to have a size that remains as a groove even after the first intermediate metal layer 13 is formed on the surface of the first aluminum plate 12.

[0077] Similar groove portions 131 may be formed on the surface of the first metal member 15 on the side of the first copper sintered layer 14.

[0078] (First bonding step) After heating the first laminate 50 while applying pressure in the lamination direction and then cooling it, a first bonded body 51 (see FIG. 9) in which the first aluminum plate 12 is bonded to one surface 11a of the ceramic substrate 11 and the second aluminum plate 21 is bonded to the other surface 11b is formed.

[0079] At this time, the brazing materials 41 and 42 are melted by heating and further diffuse into the first aluminum plate 12 and the second aluminum plate 21, thereby firmly bonding them to the ceramic substrate 11. All the components of the brazing materials 41 and 42 may diffuse into the first aluminum plate 12 and the second aluminum plate 21, or may remain as layers.

[0080] The bonding conditions at this time are not necessarily limited, but it is preferable to hold in a vacuum atmosphere at a pressure in the stacking direction of 0.1 MPa to 3.4 MPa, a heating temperature of 610 °C or higher and 655 °C or lower for 1 minute or longer and 60 minutes or shorter.

[0081] (Intermediate metal layer forming step) As shown in FIG. 9, a first intermediate metal layer 13 is formed on the surface of the first aluminum plate 12 of the first joined body 51 opposite to the ceramic substrate 11 by plating or the like. It may be formed by a thin film forming technique other than plating, or may be formed by disposing a foil of any one of copper, nickel, silver, and gold on the surface of the first aluminum plate 12 and performing diffusion bonding.

[0082] (Second stacking step) As shown by the arrow in FIG. 9, a first joining material 310 is disposed on the first intermediate metal layer 13, and a first metal member 15 is placed on the first joining material 310 to form a second stacked body 52.

[0083] (Second bonding step) The first joining material 310 is sintered by heating the second stacked body 52 while applying pressure in the stacking direction. At this time, the pressure in the stacking direction is preferably 5 MPa or higher and 10 MPa or lower, and the heating temperature of 250 °C or higher and 300 °C or lower is held for 3 minutes or longer and 60 minutes or shorter.

[0084] By this heating and pressing, the solvent 312 of the first joining material 310 and the film 313 around the copper particles 311 are burned out, and further, a plurality of copper particles 311 are sintered to form a first copper sintered layer 14. Then, the first intermediate metal layer 13 and the first metal member 15 are joined to the first copper sintered layer 14, and the multilayer joined body 20 shown in FIG. 4 is formed.

[0085] The multilayer joined body 20 manufactured in this way can be used as an insulated circuit board with a heat sink having the surface 15a of the first metal member 15 as an electronic component mounting surface and the second aluminum plate 21 as a heat sink.

[0086] In this manufacturing method, first, a first aluminum plate 12 and a second aluminum plate 21 are joined to both surfaces of a ceramic substrate 11 in a first joining step. Then, in a second joining step, a first metal member 15 is joined onto the first aluminum plate 12 via a first copper sintered layer 14.

[0087] In this case, in the first joining step, since joining is performed using a brazing material 41, it is a high-temperature treatment. However, since aluminum plates 12 and 21 of the same type are joined to both surfaces of the ceramic substrate 11, warping after joining is less likely to occur. In particular, by using high-purity aluminum as the first aluminum plate 12 and the second aluminum plate 21, warping is less likely to occur, and by making the plate thicknesses the same or of the same degree, warping is even less likely to occur.

[0088] And in the subsequent second joining step, since members 13, 14, and 15 are joined only to one surface side (the first aluminum plate 12 side) of the ceramic substrate 11, although an imbalance occurs in the laminated structures on both sides via the ceramic substrate 11, since the heating temperature is suppressed and joining is performed at a low temperature of 250°C or higher and 300°C or lower, the occurrence of warping can be suppressed.

[0089] In this way, in this multilayer joined body (insulated circuit board with heat sink) 20, by using the first joining material 310, it is possible to perform good joining with warping suppressed, so it is also possible to increase the joining area between the first metal member 15 and the first aluminum plate 12.

[0090] That is, when joining these using a copper paste, since organic components may cause the generation of voids due to heating during joining, there are cases where it is restricted to increase the joining area of the first metal member 15 and the first aluminum plate 12 because a large amount of copper paste cannot be used. In contrast, in this embodiment, the first joining material 310 formed in a sheet shape is used, and since the organic components are reduced compared to the copper paste, the generation of voids in the second joining step can be suppressed.

[0091] In this case, the planar sizes of the first aluminum plate 12 and the first metal member 15, that is, the size of the surface (bonding surface) bonded by the first bonding material 310, are not particularly limited, but a first bonding material 310 with a size exceeding 100 mm 2 may be used for bonding. In particular, when using a bonding sheet formed by connecting a plurality of copper particles 311 with a binder to form a sheet shape as the first bonding material 310, or when using a copper sintered sheet in a state where the copper particles 311 are partially sintered into a sheet shape, the surface of the first copper sintered layer 14 bonded to the first metal member 15 can be made larger than when using a copper paste.

[0092] 100 mm 2 Even in the case of a larger area, by using a copper sintered sheet as the first bonding material 310 for bonding, voids associated with the volatilization of the binder can be reduced. The size of the bonding surface may be 200 mm 2 or more, and may be 500 mm 2 or more. Also, the upper limit of the bonding surface is not particularly limited, but may be 2000 mm 2 or less, and may be 1000 mm 2 or less.

[0093] The thickness of the first copper sintered layer 14 in the stacking direction is preferably, for example, 50 μm or more and 1000 μm or less, and may be 500 μm or more. In particular, when bonding using a copper sintered sheet in which the copper particles 311 are partially sintered into a sheet shape as the first bonding material 310, the thickness of the first copper sintered layer 14 in the stacking direction can be made thicker than when using a copper paste.

[0094] In the intermediate metal layer forming step, since the first intermediate metal layer 13 containing any one of copper, nickel, silver, and gold is formed on the surface of the first aluminum plate 12, in the second bonding step, the first aluminum plate 12 and the first copper sintered layer 14 can be firmly bonded through this first intermediate metal layer 13.

[0095] Furthermore, by forming the groove portions 131 on the surfaces of the first aluminum plate 12 and the first metal member 15 that face the first copper sintered layer 14, even if gas is generated from the organic components of the first bonding material 310 due to heating during bonding, it can flow out to the outside through the groove portions 131, so that the generation of voids can be further suppressed. As a result, the bonding property is further improved, and it can further contribute to the expansion of the bonding area.

[0096] [Configuration of semiconductor device 100] An electronic component 70 such as a power device can be mounted on the surface 15a of the first metal member 15 of the multilayer bonded body 20 shown in FIG. 4 to manufacture a semiconductor device 100 such as a power module shown in FIG. 10. In the semiconductor device 100 shown in FIG. 10, the electronic component 70 is bonded to the surface 15a of the first metal member 15, the tip of a lead frame 71 made of a copper alloy is bonded to the electronic component 70, and it is sealed with an insulating resin 72.

[0097] In this case, the insulating resin 72 entirely embeds the surface 21a of the second aluminum plate 21 on the side opposite to the ceramic substrate 11 and the ends of the lead frame 71 in an exposed state. In the illustrated example, a plurality of electronic components 70 are mounted, the lead frame 71 is connected to the electronic component 70 and a part of the first metal member 15 respectively, and the ends of each lead frame 71 are exposed in a state of protruding from the insulating resin 72. Reference numeral 73 indicates a soldering material.

[0098] [Manufacturing method of semiconductor device 100] The method for manufacturing this semiconductor device 100 will be described. As described after the manufacturing process of the multilayer bonded body 20 indicated by E in FIG. 5, after the second bonding process, there are a mounting process of mounting the electronic component 70 and the like, and a resin sealing process of sealing the electronic component 70 and the like with the insulating resin 72 after the mounting process. Hereinafter, these processes will be described.

[0099] (Mounting process) A film is formed on the surface of the first metal member 15 in the multilayer laminate 20 by nickel plating or the like, and an electronic component 70 is joined thereon using a solder material 73. As the solder material 73, a solder material such as Sn-Ag-Cu, Zn-Al, Sn-Ag, Sn-Cu, Sn-Sb, or Pb-Sn is used. Also, one end of a lead frame 71 is connected to the electronic component 70 using the solder material 73. This lead frame 71 is made of copper or a copper alloy and is formed in a narrow plate shape or the like.

[0100] When connecting a plurality of electronic components 70 to each other, etc., the electronic components 70 may be connected by wire bonding. Also, when connecting the lead frame 71 to the electronic component 70, it may be connected by the solder material 73 or by wire bonding. In this case, the bonding wire is embedded in the insulating resin 72 by the following resin encapsulation process.

[0101] (Resin Encapsulation Process) The entire body including the electronic component 70 is encapsulated with the insulating resin 72 in a state where the surface 21a of the second aluminum plate 21 in the multilayer laminate 20 opposite to the ceramic substrate 11 and the end portions of each lead frame 71 opposite to the electronic component 70 are exposed.

[0102] Specifically, as shown in FIG. 11, using an injection molding die 80, the multilayer laminate 20 is placed in the cavity 81 of the injection molding die 80 with the surface 21a of the second aluminum plate 21 in contact with the inner surface of the injection molding die 80. Also, the end portions of each lead frame 71 opposite to the electronic component 70 are placed in the gaps of the die or the like and held so as not to be exposed to the cavity 81.

[0103] With the multilayer laminate 20 arranged in the injection molding die 80 as shown in FIG. 11, it is fixed so as not to move in the cavity 81, and an insulating resin 72 such as an epoxy resin is injected into the cavity 81. After the insulating resin 72 has solidified, if the die 80 is opened, the semiconductor device 100 encapsulated with the insulating resin 72 can be taken out.

[0104] The semiconductor device 100 (see FIG. 10) manufactured in this way is used in a form such as applying a conductive grease or the like to the surface 21a exposed from the insulating resin 72 of the second aluminum plate 21 and fixing it in a state of being in contact with a cooler or the like.

[0105] In the multilayer laminate 20 shown in FIG. 4, a second intermediate metal layer 17 may be formed between the first metal member 15 and the first copper sintered layer 14 as shown in FIG. 3 in the intermediate metal layer forming step. Specifically, in the intermediate metal layer forming step shown in FIG. 5, the first intermediate metal layer 13 is formed on the first aluminum plate 12 and the second intermediate metal layer 17 is formed on the surface of the first metal member 15. In the second lamination step, the first metal member 15 is placed so that the second intermediate metal layer 17 on the surface of the first metal member 15 is in contact with the first bonding material 310 (see FIG. 9), and is joined in the second joining step. This is effective when the first metal member 15 contains aluminum or an aluminum alloy.

[0106] In the semiconductor device 100 shown in FIG. 10, an example is shown in which the surface 15a of the first metal member 15 in the multilayer laminate 20 shown in FIG. 4 is used as the electronic component mounting surface. However, it is also possible to use the surface 21a on the side opposite to the ceramic substrate 11 of the second aluminum plate 21 as the electronic component mounting surface.

[0107] [Configuration of Multilayer Laminate 40] FIG. 12 shows a multilayer laminate 40 in which the surface 21a on the side opposite to the ceramic substrate 11 of the second aluminum plate 21 is used as the electronic component mounting surface, contrary to FIG. 4. The reference numerals of each component are the same as those in FIG. 4 (the same applies hereinafter in FIGS. 13 and later). However, for easy comparison with FIG. 4, the first aluminum plate 12 and the like on one side of the ceramic substrate 11 are shown as one laminated portion, and the second aluminum plate 21 is separated into two, A and B. The laminated structure of this multilayer laminate 40 is the same as that of the multilayer laminate 20 shown in FIG. 4.

[0108] [Configuration of Multilayer Laminate 45] Figure 13 shows a multi-layer laminate 45 which is an application example of the multi-layer laminate 40 shown in Figure 12. In this multi-layer laminate 45, a first aluminum plate 12 is joined to one surface of a ceramic substrate 11, and a second aluminum plate 21 is joined to the other surface. A first intermediate metal layer 13 is formed on the surface of the first aluminum plate 12, and a third intermediate metal layer 18 is formed on the surface of the second aluminum plate 21. A first metal member 60 is joined to the first intermediate metal layer 13 of the first aluminum plate 12 via a first copper sintered layer 14. As the insulating circuit board, the second aluminum plate 21 corresponds to the circuit layer, and the first metal member 60 corresponds to the heat sink.

[0109] In the example shown in this Figure 13, the first intermediate metal layer 13 is formed by plating containing any one of copper, nickel, silver, and gold. In order to enhance the adhesion to electronic components as the circuit layer, the third intermediate metal layer 18 is also formed on the surface of the second aluminum plate 21 by plating containing any one of copper, nickel, silver, and gold.

[0110] The first aluminum plate 12 is shown as one laminated portion, but the second aluminum plate 21 constituting the circuit layer is shown separated into two, A and B, in the same manner as in Figure 1 etc. The first metal member 60 contains any one of aluminum, aluminum alloy, copper, and copper alloy, and is formed in the shape of a heat sink with fins in which a large number of pin-shaped or plate-shaped fins 62 stand upright parallel to each other on one side of a flat metal plate portion 61.

[0111] [Configuration of Semiconductor Device 110] Next, a semiconductor device 110 using this multi-layer laminate 45 will be described.

[0112] As shown in FIG. 14, in this semiconductor device 110, an electronic component 70 is joined via a solder material 73 onto a third intermediate metal layer 18 formed on a second aluminum plate 21 indicated by reference sign B of a multilayer laminate 45. A lead frame 71 is joined to the third intermediate metal layer 18 of the electronic component 70 and the second aluminum plate 21 indicated by reference sign A by the solder material 73. The electronic component 70 is sealed with an insulating resin 72 in a state where the ends of a first metal member (heat sink) 60 and each lead frame 71 are exposed. Specifically, the entirety of the first metal member 60 is exposed from the insulating resin 72 at the interface between the first intermediate metal layer 13 and the first copper sintered layer 14 on the surface of the first aluminum plate 12.

[0113] [Method for manufacturing semiconductor device 110] The method for manufacturing this semiconductor device 110 will be described with reference to the flowchart shown in FIG. 15. First, a first aluminum plate 12 and a second aluminum plate 21 are laminated on both surfaces of a ceramics substrate 11 via brazing materials 41 and 42 (see FIG. 6), respectively, to form a first laminate (first lamination step). The first laminate is pressurized and heated to be joined to form a first joined body 53 as shown in FIG. 16 (first joining step).

[0114] The steps up to this point are the same as those in the multilayer laminate 20 shown in FIG. 4. Note that a plurality of groove portions 131 may be formed on the surface of the first aluminum plate 12 opposite to the ceramics substrate.

[0115] Next, a first intermediate metal layer 13 containing any one of copper, nickel, silver, and gold is formed on the surface of the first aluminum plate 12 of the first joined body 53 by plating or the like (intermediate metal layer forming step). As described above, in the example shown in FIG. 16, in order to improve the joinability with the electronic component, a film of a third intermediate metal layer 18 containing any one of copper, nickel, silver, and gold is similarly formed on the surface of the second aluminum plate 21. When the first intermediate metal layer 13 or the third intermediate metal layer 18 is formed of silver or gold, a nickel film may be formed as an underlayer, and the first intermediate metal layer 13 or the third intermediate metal layer 18 may be formed thereon.

[0116] After the intermediate metal layer forming step, an electronic component 70 is joined using a solder material 73 on the second aluminum plate 21, and one end of a lead frame 71 is connected to the electronic component 70 (mounting step).

[0117] Next, as shown in FIG. 17, with the first intermediate metal layer 13 on the surface of the first aluminum plate 12 opposite to the ceramic substrate 11 and the ends of the respective lead frames 71 opposite to the electronic component 70 exposed, the entire assembly including the electronic component 70 is encapsulated with an insulating resin 72 (resin encapsulation step).

[0118] Next, as shown by the arrow in FIG. 17, a first bonding material 310 and a first metal member 60 are sequentially laminated on the first intermediate metal layer 13 exposed from the insulating resin 72 to form a second laminate 54 (second lamination step). In this case, since the first metal member 60 is formed as a finned heat sink having a plurality of fins 62 on one side of a metal plate portion 61, the surface 61a of the metal plate portion 61 opposite to the fins 62 is brought into contact with the first bonding material 310.

[0119] As described above, this first bonding material 310 is composed of a plurality of copper particles 311 of 90% by mass or more and 99% by mass or less, and a solvent (binder) 312 of 1% by mass or more and 10% by mass or less, and the copper particles 311 are covered with an organic film 313.

[0120] An intermediate metal layer (second intermediate metal layer) containing any one of copper, nickel, silver, and gold may be formed on the surface of the first metal member 60 that contacts the first bonding material 310 (in the case of FIG. 17, the surface 61a of the metal plate portion 61 opposite to the fins 62). In particular, when the first metal member 60 is formed of aluminum or an aluminum alloy, forming the intermediate metal layer can enable good bonding in the subsequent second bonding step.

[0121] Furthermore, a plurality of groove portions (groove portions 131 shown in FIGS. 7 and 8) may be formed on the surface 61a of the first metal member 60 that contacts the first bonding material 310.

[0122] Then, by pressing and heating the second laminate 54 in the lamination direction to sinter the copper particles 311 of the first bonding material 310, the first metal member 60 and the first intermediate metal layer 13 are joined via the first copper sintered layer 14 (second bonding step), and the semiconductor device 110 shown in FIG. 14 is formed. At this time, the pressing force is preferably 5 MPa or more and 10 MPa or less, and the heating temperature is maintained at 250° C. or more and 300° C. or less for 3 minutes or more and 60 minutes or less.

[0123] In this manufacturing method, after the mounting step and the resin sealing step, a second bonding step involving pressing and heating is performed. In this second bonding step, bonding is performed by the first copper sintered layer 14, and the heating temperature is suppressed. Since bonding is performed at a low temperature of 250° C. or more and 300° C. or less, the thermal influence on the electronic component 70, the insulating resin 72, etc. can be suppressed.

[0124] [Configuration of the multi-layer bonded body 30] It is also possible to join a second metal member to the second aluminum plate 21 of the multi-layer bonded body 20 shown in FIG. 4 via a copper sintered layer.

[0125] FIG. 18 shows such a multi-layer bonded body 30, in which a second metal member 65 is joined to the second aluminum plate 21 via a third intermediate metal layer 18 and a second copper sintered layer 19. The third intermediate metal layer 18 contains any one of copper, nickel, silver, and gold. The second copper sintered layer 19 is formed by sintering copper particles 311 with each other, similar to the first copper sintered layer 14.

[0126] In the case of the multi-layer bonded body 30 shown in FIG. 18, the second metal member 65, similar to the first metal member 60 in FIG. 13 etc., contains any one of aluminum, aluminum alloy, copper, and copper alloy, and is formed in the shape of a finned heat sink having a plurality of fins 62 on one side of a flat metal plate portion 61.

[0127] That is, in the multi-layer laminate 20 shown in FIG. 4, the second aluminum plate 21 can be used as a heat sink. However, in the multi-layer laminate 30 shown in FIG. 18, the second aluminum plate 21 is used as a metal plate for heat transfer, and a second metal member 65 as a heat sink is further joined to the second aluminum plate 21.

[0128] [Method for manufacturing the multi-layer laminate 30] When manufacturing this multi-layer laminate 30, as shown in the range of reference symbol E in FIG. 5, through a first lamination step and a first joining step, the first aluminum plate 12 and the second aluminum plate 21 are brazed and joined to the ceramic substrate 11 to form a first laminate 51.

[0129] Next, by an intermediate metal layer forming step, a first intermediate metal layer 13 and a third intermediate metal layer 18 are respectively formed on each surface of the first aluminum plate 12 and the second aluminum plate 21 on the side opposite to the ceramic substrate 11. Next, as shown in FIG. 19, a first metal member 15 is disposed on the first intermediate metal layer 13 via a first joining material 310, and a second metal member 65 is disposed on the third intermediate metal layer 18 via a second joining material 320 (second lamination step) to form a second laminate 55.

[0130] Similar to the first joining material 310, the second joining material 320 is composed of a plurality of copper particles 311 of 90% by mass or more and 99% by mass or less, and a solvent 312 of 1% by mass or more and 10% by mass or less (see FIG. 2).

[0131] Then, while the second laminate 55 is being pressed at a pressure of 5 MPa or more and 10 MPa or less in the lamination direction, it is held at a heating temperature of 250°C or more and 300°C or less for 3 minutes or more and 60 minutes or less to sinter the copper particles 311 of the first joining material 310 and the second joining material 320, thereby forming a first copper sintered layer 14 and a second copper sintered layer 19, and joining the first intermediate metal layer 13 on the surface of the first aluminum plate 12 to the first metal member 15, and the third intermediate metal layer 18 on the surface of the second aluminum plate 21 to the second metal member 65 respectively (second joining step).

[0132] The multilayer laminate 30 manufactured in this way can be used as an insulated circuit board with a heat sink, having the surface 15a of the first metal member 15 as the surface for mounting electronic components and the second metal member 65 as the heat sink.

[0133] In the multilayer laminate 30, when the second metal member 65 is formed of a material containing aluminum or an aluminum alloy, as shown in the multilayer laminate 90 of FIG. 20, a fourth intermediate metal layer 22 may be formed on one surface of the second metal member 65, that is, the surface of the metal plate portion 61 (between the second metal member 65 and the second copper sintered layer 19).

[0134] The fourth intermediate metal layer 22 contains any one of copper, nickel, silver, and gold, and can enhance the bonding property between the second metal member 65 and the second copper sintered layer 19. A groove portion 131 may be formed on the surface of the metal plate portion 61 of the second metal member 65 that is joined to the second copper sintered layer 19.

[0135] [Configuration of semiconductor device 120] The multilayer laminate 30 can also be a semiconductor device 120 shown in FIG. 21. This semiconductor device 120, with respect to the semiconductor device 100 shown in FIG. 10, has a third intermediate metal layer 18 containing any one of copper, nickel, silver, and gold formed on the surface 21a exposed from the insulating resin 72 of the second aluminum plate 21, and a second metal member 65 in the shape of a heat sink with fins containing any one of aluminum, an aluminum alloy, copper, and a copper alloy is joined to this third intermediate metal layer 18 via a second copper sintered layer 19.

[0136] [Manufacturing method of semiconductor device 120] When manufacturing this semiconductor device 120, as shown in FIG. 22, a first aluminum plate 12 and a second aluminum plate 21 are laminated on a ceramic substrate 11 via brazing materials 41 and 42 (first lamination step), and a first joined body is formed by applying pressure and heat (first joining step). With respect to this first joined body, first intermediate metal layers 13 and third intermediate metal layers 18 are formed on at least the surfaces of the first aluminum plate 12 and the second aluminum plate 21 opposite to the ceramic substrate 11 (intermediate metal layer forming step), and a first metal member 15 is laminated on the first intermediate metal layer 13 via a first joining material 310 (second lamination step).

[0137] Next, by applying pressure and heat, the first joining material 310 is sintered, and the first intermediate metal layer 13 and the first metal member 15 are joined by a first copper sintered layer 14 (second joining step).

[0138] Thereafter, an electronic component 70 and a lead frame 71 are joined to the surface of the first metal member 15 with a solder material 73 (mounting step), and the electronic component 70 etc. are encapsulated with an insulating resin 72 in a state where the surface of the third intermediate metal layer 18 and the end of the lead frame 71 are exposed (resin encapsulation step).

[0139] By the steps up to here, a structure similar to the semiconductor device 100 shown in FIG. 10 is manufactured. The difference from the semiconductor device 100 is that a third intermediate metal layer 18 is formed on the surface 21a of the second aluminum plate 21 exposed from the insulating resin 72.

[0140] Next, as shown by the arrow in FIG. 23, a second joining material 320 and a second metal member 65 are sequentially laminated on this third intermediate metal layer 18 to form a third laminate 56 (third lamination step).

[0141] Finally, by applying pressure and heat to this third laminate 56, copper particles of the second joining material 320 are sintered to form a second copper sintered layer 19, and the third intermediate metal layer 18 on the surface of the second aluminum plate 21 and the second metal member 65 are joined by this second copper sintered layer 19 (third joining step). By this third joining step, the semiconductor device 120 shown in FIG. 21 is manufactured.

[0142] In the manufacturing method of this semiconductor device 120 as well, after the mounting process and the resin sealing process, a third bonding process involving pressurization and heating is performed. In this third bonding process, bonding is achieved by the second copper sintered layer 19, and the heating temperature is suppressed. Since bonding is performed at a low temperature of 250°C or higher and 300°C or lower, the thermal influence on the electronic component 70, the insulating resin 72, etc. can be suppressed.

[0143] The present invention is not limited to the above embodiments.

[0144] The first aluminum plate 12 and the second aluminum plate 21 bonded to the ceramic substrate 11 are formed of a material containing aluminum or an aluminum alloy, and preferably have a configuration made of aluminum or an aluminum alloy. However, the first metal members 15, 60 and the second metal member 65 may be formed of a material containing any one of aluminum, an aluminum alloy, copper, and a copper alloy.

[0145] In order to improve the bondability with the copper sintered layers 14, 19, an intermediate metal layer 13, 18 containing any one of copper, nickel, silver, and gold is formed on the surfaces of the first aluminum plate 12 and the second aluminum plate 21. When the first metal members 15, 60 and the second metal member 65 are also formed of a material containing aluminum or an aluminum alloy, an intermediate metal layer (second intermediate metal layer 17) containing any one of copper, nickel, silver, and gold may be formed on the bonding surface with the copper sintered layers 14, 19.

[0146] In addition, when the first metal members 15, 60 and the second metal member 65 are formed of a material containing copper or a copper alloy, an intermediate metal layer containing any one of copper, nickel, silver, and gold may be formed on the bonding surface with the copper sintered layer.

[0147] Furthermore, groove portions 131 may be formed on the surfaces of the first aluminum plate 12 and the second aluminum plate 21 joined to the copper sintered layer, and on the surfaces of the first metal members 15, 60 and the second metal member 65, respectively. In this case, even if gas is generated from the organic components of the joining materials 310 and 320 due to heating during joining, it flows out to the outside through the groove portions 131, so that the generation of voids can be further suppressed.

Example

[0148] An experiment was conducted to confirm the effects of the present invention.

[0149] (1) Manufacture of the first joined body First, aluminum plates were laminated on both sides of a ceramic substrate via brazing materials, and heated in a state of being pressurized in the lamination direction, thereby forming a first aluminum plate 12 on one surface of the ceramic substrate 11 and a second aluminum plate 21 on the other surface to manufacture a first joined body.

[0150] (1-1) Materials for the first joined body Ceramic substrate: Si 3 N 4 (Thickness 0.32 mm) First aluminum plate and second aluminum plate: 4N aluminum (thickness 0.6 mm, length 30 mm, width 40 mm) Brazing material: Brazing material foil made of Al-7.5 mass% Si alloy (thickness 0.02 mm)

[0151] (1-2) Manufacturing conditions for the first joined body Joining pressure: 0.2 MPa Heating temperature: 650 °C Holding time: 30 minutes Joining atmosphere: Vacuum

[0152] (2) Manufacture of the second joined body Next, on the surface of the first aluminum plate 12 opposite to the ceramic substrate 11, a first intermediate metal layer 13 made of a plating film of any one of copper, nickel, silver, and gold (Examples 1 to 9) is formed by plating, and the first metal member 15 is laminated via the first bonding material 310 on the first intermediate metal layer 13 and heated to form a first copper sintered layer 14, thereby joining the first metal member 15 to manufacture a second joined body (sample).

[0153] In Comparative Example 1, the first intermediate metal layer 13 was not formed. In Comparative Example 2, a chromium plating (Cr plating) film was formed as the first intermediate metal layer 13. Otherwise, the second joined body (sample) was manufactured in the same manner as in Examples 1 to 9.

[0154] The first metal member 15 is formed in a rectangular shape from an aluminum plate or a copper plate, with a length of 30 mm and a width of 40 mm. The first intermediate metal layer (plating film) of each example is as described in Table 1. When the first intermediate metal layer 13 is composed of chromium, gold, or silver, a nickel plating film is formed as an underlayer on the surface of the first aluminum plate 12.

[0155] (2-1) Groove portion In Example 8 among the second joined bodies as samples, the groove portion 131 is formed on the first intermediate metal layer 13 forming surface of the first aluminum plate 12. For this groove portion 131, the pitch (interval between the deepest parts) a of the groove portion 131 shown in FIG. 7 is 1.5 [mm], the depth b of the groove portion 131 is 0.3 [mm], the width c of the groove portion 131 is 0.5 [mm], and the width d of the flat portion 132 provided between the groove portions 131 is 1.0 [mm]. Twenty groove portions 131 are formed extending from one edge to the other edge on the surface joined to the first copper sintered layer 14.

[0156] (2-2) Regarding the joining surface of the first metal member 15 with the first copper sintered layer 14 The first metal member 15 is made of an aluminum alloy (JIS 6063 series) or a copper alloy (JIS 1020 series). On the surface that is joined to the first copper sintered layer 14, as the second intermediate metal layer 17, there are two types prepared: one with a nickel plating film provided by surface treatment (Examples 2 to 4, Comparative Example 2), and one without a plating film (second intermediate metal layer) (Examples 1, 5 to 9, Comparative Example 1). The materials of the first metal member 15 and the second intermediate metal layer in each example are as described in Table 1.

[0157] (2-3) Regarding the first bonding material The first bonding material is a Cu sintered material composed of copper particles. By sintering the copper particles upon heating, the first intermediate metal layer 13 and the first metal member 15 (or the second intermediate metal layer 17 on its surface) are joined. In Examples 1 to 7 and 9, a bonding material formed in a sheet shape where copper particles 311 are connected by a solvent 312 was used, and in Example 8 and Comparative Examples 1 and 2, a paste-like bonding material was used.

[0158] (2-4) Manufacturing conditions of the second bonded body Pressing pressure: 5 MPa Heating temperature: 300 °C Holding time: 15 minutes Bonding atmosphere: Vacuum Sheet-like bonding material: Thickness 300 μm, longitudinal and transverse dimensions are the same as those of the aluminum plate

[0159] (2-5) Regarding resin encapsulation Regarding Example 9, before the second bonding step, the surface of the first aluminum plate of the first bonded body on the side opposite to the ceramic substrate was sealed with an insulating resin while being exposed.

[0160] (3) Bonding rate evaluation (3-1) Evaluation method The bonding interface between the first aluminum and the first metal member in the second bonded body was observed with an ultrasonic flaw detector, and the ultrasonic image of the bonding interface was processed and evaluated.

[0161] As an evaluation method, the bonding rate was calculated from the following formula (1). Bonding rate (%) = [((bonded area) - (peeled area)) / (bonded area)] × 100

[0162] In the ultrasonic flaw detection image (binary image), the bonded parts are shown in black, while the peeled parts (unbonded parts) are shown in white. Therefore, the total area of these white parts was taken as the peeled area.

[0163] Those with a bonding rate of 90% or more were considered qualified. Among them, those with a bonding rate of 97% or more were rated as 'A', and those with a bonding rate of 90% or more but less than 97% were rated as 'B'. Also, those with a bonding rate of 0% or more but less than 90% were considered unqualified (NG) and marked as 'C'.

[0164] These results are shown in Table 1.

[0165] In Table 1, for the first intermediate metal layer, the copper plating film is denoted as 'Cu plating film', the nickel plating film as 'Ni plating film', the gold plating film as 'Au plating film', the silver plating film as 'Ag plating film', the chromium plating film as 'Cr plating', and those without the first intermediate metal layer are denoted as 'no plating'. As for the form of the bonding material, the sheet-like bonding material is denoted as'sheet', and the paste-like bonding material is denoted as 'paste'.

[0166]

Table 1

[0167] (3-2) Evaluation As shown in Table 1, in the second bonded bodies of Examples 1 to 9, the bonding state was good in all cases. It was confirmed that there was no or little unbonded part at the bonding interface and it was difficult to peel off.

[0168] In Examples 1 to 7 and 9, the copper particles 311 of the sheet-like bonding material are sintered to form a copper sintered layer, and void generation is suppressed between the first aluminum plate and the first metal member, and the first aluminum plate and the first metal member are joined in a good joining state. Further, in Example 8, although a copper paste was used, since the groove portion was formed in the first aluminum plate, the joining state was good in all cases.

[0169] Regarding Example 9 in which the second joining step was carried out after sealing with an insulating resin, as a result of visual appearance inspection, no thermal influence (discoloration, deformation, etc.) on the insulating resin was confirmed.

[0170] On the other hand, in the second joined bodies of Comparative Examples 1 and 2, the joining rate was less than 90% in both cases, and unjoined and peeled portions at the interface were confirmed.

Industrial Applicability

[0171] When joining a heat sink to an insulating circuit board, etc., since the first metal member can be joined at a low temperature by the copper sintered layer, warpage can be suppressed and the joining property can be improved.

Explanation of Signs

[0172] 10, 16, 20, 30, 40, 45, 90 Multi-layer joined body 11 Ceramic substrate 12 First aluminum plate 13 First intermediate metal layer 14 First copper sintered layer 15, 60 First metal member 17 Second intermediate metal layer 18 Third intermediate metal layer 21 Second aluminum plate 41, 42 Brazing material 50 First laminate 51, 53 First joined body 52, 54, 55 Second laminate 56 Third laminate 65 Second metal member 70 Electronic component 71 Lead frame 72 Insulating resin 73 Solder material 80 Mold for injection molding 81 Cavity 100, 110, 120 Semiconductor device 131 Groove portion 132 Flat portion 310 First bonding material 320 Second bonding material

Claims

1. A ceramic substrate, a first aluminum plate containing aluminum or an aluminum alloy, joined to one surface of the ceramic substrate, a first intermediate metal layer joined to the surface of the first aluminum plate opposite to the ceramic substrate and containing any one of copper, nickel, silver, and gold, a first copper sintered layer joined to the surface of the first intermediate metal layer opposite to the first aluminum plate, and a first metal member joined to the surface of the first copper sintered layer opposite to the first intermediate metal layer and containing any one of aluminum, an aluminum alloy, copper, and a copper alloy, characterized in that it is a multi-layer joined body.

2. The first metal member contains aluminum or an aluminum alloy, and a second intermediate metal layer containing any one of copper, nickel, silver, and gold is formed between the first metal member and the first copper sintered layer, characterized in that it is the multi-layer joined body according to Claim 1.

3. A second aluminum plate made of aluminum or an aluminum alloy is joined to the other surface of the ceramic substrate, characterized in that it is the multi-layer joined body according to Claim 1 or 2.

4. a third intermediate metal layer joined to the surface of the second aluminum plate opposite to the ceramic substrate and containing any one of copper, nickel, silver, and gold, a second copper sintered layer joined to the surface of the third intermediate metal layer opposite to the second aluminum plate, and a second metal member joined to the surface of the second copper sintered layer opposite to the second aluminum plate and containing any one of aluminum, an aluminum alloy, copper, and a copper alloy, further characterized in that it is the multi-layer joined body according to Claim 3.

5. The second metal member contains aluminum or an aluminum alloy, and a fourth intermediate metal layer containing any one of copper, nickel, silver, and gold is formed between the second metal member and the second copper sintered layer, characterized in that it is the multi-layer joined body according to Claim 4.

6. A semiconductor device using the multi-layer joined body according to Claim 3, an electronic component mounted on the surface of the first metal member opposite to the first copper sintered layer, a lead frame connected to the electronic component, and an insulating resin for encapsulating the electronic component in a state where at least the surface of the tip of the lead frame and the second aluminum plate opposite to the ceramic substrate are exposed, characterized in that it is a semiconductor device.

7. A semiconductor device using the multi-layer bonded body according to claim 3, an electronic component mounted on the surface of the second aluminum plate opposite to the ceramic substrate, a lead frame connected to the electronic component, an insulating resin for encapsulating the electronic component in a state where the surface of the first metal member except the joint surface of the tip of the lead frame and at least the first copper sintered layer is exposed, characterized by comprising a semiconductor device.

8. A semiconductor device using the multi-layer bonded body according to claim 4, an electronic component mounted on the surface of the first metal member opposite to the first copper sintered layer, a lead frame connected to the electronic component, an insulating resin for encapsulating the electronic component in a state where the surface of the second metal member except the joint surface of the tip of the lead frame and at least the second copper sintered layer is exposed, characterized by comprising a semiconductor device.

9. A first lamination step of forming a first laminate by laminating a brazing material and a first aluminum plate containing aluminum or an aluminum alloy on one surface of a ceramic substrate, a first joining step of joining the first laminate by pressurizing and heating in a laminated state to form a first joined body, an intermediate metal layer forming step of forming a first intermediate metal layer containing any one of copper, nickel, silver, and gold on the surface of the first aluminum plate of the first joined body opposite to the ceramic substrate, a second lamination step of sequentially laminating a first joining material formed by connecting a plurality of copper particles with a binder in a sheet shape and a first metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy on the first intermediate metal layer to form a second laminate, A method for manufacturing a multi-layer bonded body, comprising: a second joining step of sintering the first joining material by heating the second laminate in a state of being pressurized in the lamination direction to form a first copper sintered layer, and joining the first intermediate metal layer and the first metal member with the first copper sintered layer.

10. The first metal member contains aluminum or an aluminum alloy, In the intermediate metal layer forming step, further, a second intermediate metal layer containing any one of copper, nickel, silver, and gold is formed on one surface of the first metal member, The method for manufacturing a multi-layer bonded body according to claim 9, wherein in the second joining step, the second intermediate metal layer is joined to the first copper sintered layer.

11. The method for manufacturing a multi-layer bonded body according to claim 9, characterized in that a plurality of groove portions are formed on the surface of the first aluminum plate opposite to the ceramic substrate before the first lamination step.

12. In the first lamination step, a second aluminum plate containing a brazing material and aluminum or an aluminum alloy is further laminated on the other surface of the ceramic substrate to form the first laminate. The method for manufacturing a multi-layer bonded body according to any one of claims 9 to 11, characterized in that in the first bonding step, the first laminate including the second aluminum plate is pressurized and heated to bond the first aluminum plate to one surface of the ceramic substrate and the second aluminum plate to the other surface to form the first bonded body.

13. In the intermediate metal layer forming step, a third intermediate metal layer containing any one of copper, nickel, silver, and gold is further formed on the surface of the second aluminum plate in the first bonded body opposite to the ceramic substrate. In the second lamination step, a second bonding material formed by connecting a plurality of copper particles with a binder in a sheet shape and a second metal member containing any one of aluminum, an aluminum alloy, copper, and a copper alloy are sequentially laminated on the third intermediate metal layer to form the second laminate. The method for manufacturing a multi-layer bonded body according to claim 12, characterized in that in the second bonding step, the second bonding material is further sintered to form a second copper sintered layer, and the third intermediate metal layer and the second metal member are bonded by the second copper sintered layer.

14. The second metal member contains aluminum or an aluminum alloy. In the intermediate metal layer forming step, a fourth intermediate metal layer containing any one of copper, nickel, silver, and gold is further formed on one surface of the second metal member. The method for manufacturing a multi-layer bonded body according to claim 13, characterized in that the fourth intermediate metal layer is bonded to the second copper sintered layer in the second bonding step.

15. A method for manufacturing a semiconductor device using the method for manufacturing a multi-layer bonded body according to claim 12, after the second bonding step, a mounting step of mounting an electronic component on the first metal member and connecting a lead frame to the electronic component. A method for manufacturing a semiconductor device, further comprising a resin encapsulation step of encapsulating the electronic component with an insulating resin in a state where the tip of the lead frame and at least the surface of the second aluminum plate opposite to the ceramic substrate are exposed from the insulating resin.

16. A method for manufacturing a semiconductor device using the method for manufacturing a multi-layer bonded body according to claim 12, between the intermediate metal layer forming step and the second lamination step, a mounting step of mounting an electronic component on the second aluminum plate and connecting a lead frame to the electronic component; A method for manufacturing a semiconductor device, further comprising a resin encapsulation step of encapsulating the electronic component with the insulating resin in a state where the tip of the lead frame and at least the surface of the first intermediate metal layer are exposed from the insulating resin.

17. A method for manufacturing a semiconductor device using the method for manufacturing a multi-layer bonded body according to claim 12, in the intermediate metal layer forming step, further forming a third intermediate metal layer containing any one of copper, nickel, silver, and gold on the surface of the second aluminum plate in the first bonded body opposite to the ceramic substrate; after the second bonding step, a mounting step of mounting an electronic component on the first metal member and connecting a lead frame to the electronic component; a resin encapsulation step of encapsulating the electronic component with an insulating resin in a state where the tip of the lead frame and at least the surface of the third intermediate metal layer are exposed from the insulating resin; a third lamination step of sequentially laminating a second bonding material formed by connecting a plurality of copper particles with a binder in a sheet shape and a second metal member containing any one of aluminum, aluminum alloy, copper, and copper alloy on the third intermediate metal layer to form a third laminate; a third bonding step of sintering the second bonding material to form a second copper sintered layer by heating the third laminate in a pressurized state in the lamination direction, and bonding the third intermediate metal layer and the second metal member with the second copper sintered layer; A method for manufacturing a semiconductor device, further comprising the steps.

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