Heat sink integrated insulating circuit board

Abstract

To provide a heat sink integral type insulation circuit board which can suppress occurrence of peeling between a circuit layer and an insulation resin layer or internal peeling of the insulation resin layer by suppressing occurrence of stress in a direction perpendicular to a surface due to temperature change, and is excellent in reliability.SOLUTION: A heat sink integral type insulation circuit board includes a heat sink 20, an insulation resin layer 12, and a circuit layer 13, wherein the circuit layer 13 is composed of copper or a copper alloy, a top plate part 21 of the heat sink 20 has a clad structure having an aluminum layer 21a composed of aluminum or an aluminum alloy and a copper layer 21c, the insulation resin layer 12 is formed on a surface of the copper layer 21c, and a ratio ta / tc of a thickness ta of the aluminum layer 21a to a thickness tc of the copper layer 21c is 30 or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a heat sink-integrated insulating circuit board including a heat sink, an insulating resin layer formed on a top plate portion of the heat sink, and a circuit layer formed on one surface of the insulating resin layer. [Background technology]

[0002] In power modules, LED modules, and thermoelectric modules, power semiconductor elements, LED elements, and thermoelectric elements are bonded to an insulating circuit board having a circuit layer made of a conductive material formed on one side of an insulating layer. As the insulating layer, those using ceramics or insulating resin have been proposed. As an insulating circuit board having an insulating resin layer, for example, Patent Document 1 proposes a heat sink integrated insulating circuit board in which a heat sink and a circuit layer are insulated by an insulating resin sheet.

[0003] Patent Document 2 discloses a composite member in which a heat dissipating base substrate is bonded to at least one surface of a heat generating member via a heat conductive insulating adhesive film. In this patent document 2, the relationship between shear adhesive strength and thermal stress, and the relationship between fracture elongation and thermal strain are specified in order to suppress the occurrence of cracks in the heat conductive insulating adhesive film due to stress caused by expansion or contraction of the heat dissipating member and the heat generating member accompanying temperature changes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-204700 [Patent Document 2] JP 2019-041111 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in a heat sink-integrated insulating circuit board in which an insulating resin layer is formed on the top plate of a heat sink and a circuit layer is formed on this insulating resin layer, stress is generated in a direction perpendicular to the surface due to temperature changes, which can cause warping. When warping occurs in the heat sink-integrated insulating circuit board, there is a risk that the ends of the circuit layer may peel off from the insulating resin layer, and that this peeling may progress into the insulating resin layer. Here, in Patent Document 2, although the stress and strain within the plane are evaluated, the stress in the direction perpendicular to the plane is not taken into consideration, and therefore peeling of the circuit layer and internal peeling of the insulating resin layer are not addressed at all.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and has an object to provide a highly reliable heat sink-integrated insulated circuit board that can suppress the occurrence of peeling between the circuit layer and the insulating resin layer, or internal peeling of the insulating resin layer, by suppressing the occurrence of stress in a direction perpendicular to the surface due to temperature changes. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the inventors conducted intensive research and discovered that by optimizing the thickness ratio of the copper layer to the aluminum layer, it is possible to reduce stress in a direction perpendicular to the surface caused by temperature changes. In other words, the top plate of the heat sink has a clad structure in which copper and aluminum layers are laminated, and the thickness of the copper layer and the thickness of the aluminum layer are changed. By thermally calculating the stress in the direction perpendicular to the surface due to temperature changes, the optimum range of these thicknesses was determined.

[0008] The present invention has been made based on the above-mentioned findings, and a heatsink-integrated insulating circuit board of the present invention comprises a heatsink, an insulating resin layer formed on a top plate portion of the heatsink, and a circuit layer formed on one surface of the insulating resin layer, the circuit layer being made of copper or a copper alloy, the top plate portion of the heatsink having a clad structure including an aluminum layer made of aluminum or aluminum and a copper layer laminated on the aluminum layer, the insulating resin layer being formed on a surface of the copper layer, and a ratio ta / tc of a thickness ta of the aluminum layer to a thickness tc of the copper layer being such that 0.1 or more It is characterized by being 30 or less.

[0009] In the heatsink-integrated insulating circuit board of this configuration, the top plate of the heatsink has a clad structure in which a copper layer and an aluminum layer are laminated, and the ratio ta / tc of the thickness ta of the aluminum layer to the thickness tc of the copper layer is set to be 30 or less. This makes it possible to reduce stress in a direction perpendicular to the surface caused by temperature changes, and to suppress peeling between the circuit layer and the insulating resin layer, or internal peeling of the insulating resin layer.

[0010] In the heat sink-integrated insulating circuit board of the present invention, the insulating resin layer preferably contains an inorganic filler. In this case, since the thermal conductivity of the insulating resin layer is ensured, heat from the heat source mounted on the circuit layer can be efficiently transferred to the heat sink side, making it possible for the heat to be efficiently dissipated on the heat sink side.

[0011] In the heat sink integrated insulating circuit board of the present invention, the heat sink preferably includes heat dissipation fins. In this case, the heat dissipation characteristics of the heat sink are improved, and heat from a heat source mounted on the circuit layer can be efficiently dissipated on the heat sink side. Effect of the Invention

[0012] According to the present invention, by suppressing the generation of stress in a direction perpendicular to the surface due to temperature changes, peeling between the circuit layer and the insulating resin layer, or internal peeling of the insulating resin layer, can be suppressed, making it possible to provide a highly reliable heat sink-integrated insulating circuit board. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic explanatory diagram of a power module including a heat sink-integrated insulating circuit board according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a flow diagram illustrating an example of a method for manufacturing a heat sink-integrated insulating circuit board according to an embodiment of the present invention. [Diagram 3] 1A to 1C are schematic explanatory diagrams of a method for manufacturing a heat sink-integrated insulating circuit board according to an embodiment of the present invention. [Figure 4] 1A to 1C are schematic explanatory diagrams of a method for manufacturing a heat sink-integrated insulating circuit board according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a heat sink integrated insulating circuit board 10 according to an embodiment of the present invention and a power module 1 using this heat sink integrated insulating circuit board 10.

[0015] The power module 1 shown in FIG. 1 includes a heat sink integrated insulating circuit board 10 and a semiconductor element 3 joined to one surface (the upper surface in FIG. 1) of the heat sink integrated insulating circuit board 10 via a solder layer 2.

[0016] The semiconductor element 3 is made of a semiconductor material such as Si. The solder layer 2 that joins the heat sink-integrated insulating circuit board 10 and the semiconductor element 3 is made of, for example, a Sn-Ag-based, Sn-Cu-based, Sn-In-based, or Sn-Ag-Cu-based solder material (so-called lead-free solder material).

[0017] The insulating resin layer 12 prevents electrical connection between the circuit layer 13 and the heat sink 20, and is made of an insulating resin. In this embodiment, it is preferable to use a resin containing an inorganic filler in order to ensure the strength and thermal conductivity of the insulating resin layer 12. Here, the filler may be, for example, alumina, boron nitride, aluminum nitride, or the like. From the viewpoint of ensuring the thermal conductivity of the insulating resin layer 12, the content of the filler is preferably 70 mass% or more, and more preferably 80 mass% or more. As the thermosetting resin, an epoxy resin, a polyimide resin, a silicone resin, etc. can be used. Here, the epoxy resin can contain 70 mass% or more of a filler, and the silicone resin can contain 80 mass% or more of a filler.

[0018] In order to ensure sufficient insulation in the insulating resin layer 12, the thickness of the insulating resin layer 12 is preferably 50 μm or more, and more preferably 100 μm or more. On the other hand, in order to further ensure the heat dissipation properties of the heat sink-integrated insulating circuit board 10, the thickness of the insulating resin layer 12 is preferably 250 μm or less, and more preferably 150 μm or less.

[0019] As shown in Fig. 4, the circuit layer 13 is formed by bonding a metal piece 33 made of copper or a copper alloy having excellent conductivity to one surface (the upper surface in Fig. 4) of the insulating resin layer 12. The metal piece 33 constituting the circuit layer 13 is one punched out from a rolled sheet of oxygen-free copper. A circuit pattern is formed on this circuit layer 13, and one surface thereof (the upper surface in FIG. 1) serves as a mounting surface on which a semiconductor element 3 is mounted. Here, the thickness t of the circuit layer 13 is preferably within a range of 0.1 mm to 3.0 mm. By setting the thickness t of the circuit layer 13 to 0.1 mm or more, the heat generated by the semiconductor element 3 can be sufficiently spread. On the other hand, by setting the thickness t of the circuit layer 13 to 3.0 mm or less, the occurrence of problems such as deterioration in the accuracy of forming the circuit pattern and deterioration in manufacturing efficiency can be suppressed. In order to ensure heat dissipation, the thickness t of the circuit layer 13 is preferably 0.3 mm or more, and more preferably 0.5 mm or more, and more preferably 2.5 mm or less, and more preferably 2.0 mm or less.

[0020] The heatsink-integrated insulating circuit board 10 includes a heatsink 20, an insulating resin layer 12 formed on one surface (upper surface in FIG. 1) of a top plate portion 21 of the heatsink 20, and a circuit layer 13 formed on one surface (upper surface in FIG. 1) of the insulating resin layer 12. The semiconductor element 3 described above is bonded to one surface (upper surface in FIG. 1) of the circuit layer 13.

[0021] The heat sink 20 includes a top plate portion 21 and heat dissipation fins 25 protruding from the other surface of the top plate portion 21 (the lower surface in FIG. 1). The heat sink 20 is configured such that the top plate portion 21 spreads heat in the planar direction and dissipates the heat to the outside via the heat dissipation fins 25 .

[0022] As shown in FIG. 1, the top plate 21 of the heat sink 20 has a clad structure in which a copper layer 21c and an aluminum layer 21a are laminated, and an insulating resin layer 12 is formed on the surface of the copper layer 21c. The copper layer 21c is made of pure copper or a copper alloy, and in this embodiment, is made of oxygen-free copper. The aluminum layer 21a is made of pure aluminum or an aluminum alloy, and in this embodiment, it is made of an A6063 alloy. In addition to A6063, aluminum alloys such as A3003 can be used. As pure aluminum, 2N-Al with a purity of 99 mass% or more, 3N-Al with a purity of 99.9 mass% or more, 4N-Al with a purity of 99.99 mass% or more, etc. can be used.

[0023] The ratio ta / tc of the thickness ta of the aluminum layer 21a constituting the top plate portion 21 to the thickness tc of the copper layer 21c is set to be equal to or less than 30. If the ratio ta / tc exceeds 30, peeling occurs at the end of the interface between the metal (copper layer 21c) and the resin due to thermal stress caused by the difference in linear expansion of the members during heat treatment. Here, the ratio ta / tc of the thickness ta of the aluminum layer 21a to the thickness tc of the copper layer 21c is preferably equal to or less than 20, and more preferably equal to or less than 10. There is no particular lower limit to the ratio ta / tc of the thickness ta of the aluminum layer 21a to the thickness tc of the copper layer 21c, but it is preferably equal to or greater than 0.1, and more preferably equal to or greater than 0.5.

[0024] In this embodiment, the thickness tc of the copper layer 21c constituting the top plate portion 21 is preferably within a range of 0.1 mm to 3.0 mm. By making the thickness tc of the copper layer 21c 0.1 mm or more, it is possible to prevent the copper layer 21c from turning into an intermetallic compound and deteriorating heat dissipation when a clad structure is formed in which the aluminum layer 21a and the copper layer 21c are laminated by solid-phase diffusion bonding. On the other hand, by making the thickness tc of the copper layer 21c 3.0 mm or less, it is possible to prevent problems from occurring in terms of the workability of copper. Here, the thickness tc of the copper layer 21c is more preferably 0.3 mm or more, and even more preferably 0.5 mm or more, and more preferably 3.0 mm or less, and even more preferably 2.0 mm or less.

[0025] In this embodiment, the thickness ta of the aluminum layer 21a constituting the top plate portion 21 is preferably within a range of 0.1 mm to 5.0 mm. By setting the thickness ta of the aluminum layer 21a to 0.1 mm or more, problems occurring on the processed surface of the fin can be suppressed. On the other hand, by setting the thickness ta of the aluminum layer 21a to 5.0 mm or less, deterioration of heat dissipation can be suppressed. Here, the thickness ta of the aluminum layer 21a is more preferably 1.0 mm or more, and even more preferably 2.0 mm or more. Also, the thickness ta of the aluminum layer 21a is more preferably 4.0 mm or less, and even more preferably 3.0 mm or less.

[0026] The heat dissipating fins 25 are connected to the aluminum layer 21a, and in this embodiment, the heat dissipating fins 25 are also made of the same material (A6063 alloy) as the aluminum layer 21a. The heat dissipating fins 25 may have a pin fin structure or a comb structure. It is preferable that the volume ratio of the heat dissipating fins 25 in the area where the heat dissipating fins 25 are formed is within a range of 10% to 40%.

[0027] Next, a method for manufacturing the heat sink-integrated insulating circuit board 10 according to this embodiment will be described with reference to FIGS.

[0028] (Top plate forming process S01) First, the top plate portion 21 having a clad structure in which the aluminum layer 21a and the copper layer 21c are laminated is formed. In this embodiment, as shown in Fig. 3, aluminum plate 31a and copper plate 31c are laminated, and pressure and heat are applied in the lamination direction to solid-state diffusion bond aluminum plate 31a and copper plate 31c to form clad structure top plate portion 21. In this embodiment, as shown in Fig. 3, aluminum plate 31a is bonded to copper plate 31c with heat dissipation fins 25 formed thereon. Here, the conditions for solid-phase diffusion bonding of the aluminum plate 31a and the copper plate 31c are preferably a heating temperature in the range of 400°C or higher and lower than 548°C, a pressure load in the range of 0.1 MPa or higher and 3.5 MPa or lower, and a holding time in the range of 5 minutes or higher and 240 minutes or lower.

[0029] (Resin composition disposing step S02) Next, as shown in Fig. 4, a resin composition 32 containing an inorganic filler, a resin, and a curing agent is disposed on one surface (the upper surface in Fig. 4) of the top plate portion 21 (copper layer 21c) of the heat sink 20. In this embodiment, the resin composition 32 is in the form of a sheet.

[0030] (Metal piece placement process S03) Next, on one surface of the resin composition 32 (the upper surface in FIG. 4), a plurality of metal pieces 33 which will become the circuit layer 13 are arranged in a circuit pattern.

[0031] (Pressure and heating process S04) Next, a pressure device is used to pressurize and heat the heat sink 20, the resin composition 32, and the metal piece 33 in the stacking direction, thereby hardening the resin composition 32 to form the insulating resin layer 12 and bonding the top plate portion 21 (copper layer 21c) of the heat sink 20 to the insulating resin layer 12, and the insulating resin layer 12 to the metal piece 33.

[0032] In the pressurizing and heating step S04, the heating temperature is preferably in the range of 120° C. to 350° C., and the holding time at the heating temperature is preferably in the range of 10 minutes to 180 minutes. Also, the pressurizing load in the stacking direction is preferably in the range of 1 MPa to 30 MPa. Here, the lower limit of the heating temperature is more preferably 150° C. or more, and even more preferably 170° C. or more. On the other hand, the upper limit of the heating temperature is more preferably 250° C. or less, and even more preferably 200° C. or less. The lower limit of the holding time at the heating temperature is more preferably 30 minutes or more, and even more preferably 60 minutes or more, while the upper limit of the holding time at the heating temperature is more preferably 120 minutes or less, and even more preferably 90 minutes or less. The lower limit of the pressure load in the stacking direction is more preferably 5 MPa or more, and even more preferably 8 MPa or more, while the upper limit of the pressure load in the stacking direction is more preferably 15 MPa or less, and even more preferably 10 MPa or less.

[0033] The heat sink-integrated insulating circuit board 10 of this embodiment is manufactured by the steps described above.

[0034] According to the heatsink-integrated insulating circuit board 10 of this embodiment configured as described above, the top plate 21 of the heatsink 20 has a clad structure in which the copper layer 21c and the aluminum layer 21a are laminated, and the ratio ta / tc of the thickness ta of the aluminum layer 21a to the thickness tc of the copper layer 21c is set to be 30 or less. This makes it possible to reduce stress in a direction perpendicular to the surface caused by temperature changes, and to suppress peeling between the circuit layer 13 and the insulating resin layer 12 or internal peeling of the insulating resin layer 12.

[0035] In this embodiment, since the insulating resin layer 12 contains an inorganic filler, the thermal conductivity of the insulating resin layer 12 is ensured, and heat from the semiconductor element 3 mounted on the circuit layer 13 can be efficiently transferred to the heat sink 20.

[0036] Furthermore, in this embodiment, since the heat sink 20 is equipped with heat dissipation fins 25, the heat dissipation characteristics of the heat sink 20 are improved, and heat from the semiconductor element 3 mounted on the circuit layer 13 can be efficiently dissipated on the heat sink 20 side.

[0037] Although the embodiment of the present invention has been described above, the present invention is not limited to this, and can be modified as appropriate without departing from the technical concept of the invention. In this embodiment, a heat sink-integrated insulating circuit board is manufactured by the method for manufacturing a heat sink-integrated insulating circuit board shown in FIGS. 2 to 4, but the present invention is not limited to this. For example, in this embodiment, the top plate portion of the clad structure is described as being formed by solid-state diffusion bonding of a copper plate and an aluminum plate, but this is not limited to this, and the top plate portion of the clad structure may also be formed by plating a copper layer on the surface of an aluminum plate.

[0038] Furthermore, in the present embodiment, a power module is configured by mounting a semiconductor element on a heat sink-integrated insulating circuit board, but the present invention is not limited to this. For example, an LED module may be configured by mounting an LED element on a circuit layer of a heat sink-integrated insulating circuit board, or a thermoelectric module may be configured by mounting a thermoelectric element on a circuit layer of a heat sink-integrated insulating circuit board.

[0039] In addition, in the present embodiment, the insulating resin layer is described as containing an inorganic filler, but this is not limited thereto, and the insulating resin layer may not contain an inorganic filler. Furthermore, in the present embodiment, the heat sink is described as having heat dissipation fins, but the present invention is not limited to this, and the heat sink may have a structure that does not have heat dissipation fins. EXAMPLES

[0040] The results of experiments carried out to confirm the effects of the present invention will be described below.

[0041] A sheet material of the resin composition shown in Table 1 was placed on the top plate of a heat sink (50 mm x 50 mm, thickness is shown in Table 1) having a structure shown in Table 1, and a metal piece forming a circuit layer shown in Table 1 was placed on the sheet material of the resin composition. The laminated heat sink, the sheet material of the resin composition, and the metal piece were heated while being pressurized in the stacking direction, the resin composition was cured to form an insulating resin layer, and the top plate of the heat sink and the insulating resin layer, and the insulating resin layer and the metal piece were bonded to obtain a heat sink integrated insulating circuit board. The pressurizing pressure in the stacking direction was 1 MPa, the heating temperature was 530°C, and the holding time at the heating temperature was 60 minutes. In addition, in Table 1, "Al2O3, BN" indicates that a filler made of alumina and BN mixed at a volume ratio of 1:4 was used. The heat sink-integrated insulating circuit board thus obtained was evaluated for the following items.

[0042] (Fracture after heat treatment) The obtained heat sink-integrated insulating circuit board was subjected to a heat treatment at 300℃ for 10 minutes, and the fracture state of the insulating resin layer was confirmed. The heat sink-integrated insulating circuit board after the heat treatment was cut along the diagonal of the rectangle when viewed from above, and the cross section was observed. If the fracture length in the insulating resin layer was 2% or more of the diagonal length of the insulating resin layer, it was marked as "X", and if it was less than 2%, it was marked as "O".

[0043] [Table 1]

[0044] In Comparative Example 1, in which the top plate was made only of aluminum, fracture of the insulating resin layer was confirmed after the heat treatment. In Comparative Example 2, in which the top plate portion had a laminated structure of an aluminum layer and a copper layer and the ratio ta / tc of the thickness ta of the aluminum layer to the thickness tc of the copper layer exceeded 30, fracture of the insulating resin layer was confirmed after heat treatment.

[0045] In contrast, in Examples 1 to 14 of the present invention, in which the top plate portion has a laminated structure of an aluminum layer and a copper layer and the ratio ta / tc of the thickness ta of the aluminum layer to the thickness tc of the copper layer is 30 or less, breakage of the insulating resin layer after heat treatment could be sufficiently suppressed.

[0046] From the above, it has been confirmed that according to the present invention, by suppressing the generation of stress in a direction perpendicular to the surface due to temperature changes, peeling between the circuit layer and the insulating resin layer, or internal peeling of the insulating resin layer, can be suppressed, and a highly reliable heat sink-integrated insulating circuit board can be provided. [Explanation of symbols]

[0047] 10. Heat sink integrated insulating circuit board 12 Insulating resin layer 13 circuit layer 20 Heat sink 21 Top plate 21c copper layer 21a Aluminum layer 25 Heat dissipation fin

Claims

1. a heat sink, an insulating resin layer formed on a top plate portion of the heat sink, and a circuit layer formed on one surface of the insulating resin layer; The circuit layer is made of copper or a copper alloy, a top plate portion of the heat sink having a clad structure including an aluminum layer made of aluminum or an aluminum alloy and a copper layer laminated on the aluminum layer, and the insulating resin layer is formed on a surface of the copper layer; 1. A heat sink-integrated insulating circuit board, comprising: a ratio ta / tc of a thickness ta of said aluminum layer to a thickness tc of said copper layer, said ratio being 0.1 or more and 30 or less.

2. 2. The heat sink-integrated insulating circuit board according to claim 1, wherein the insulating resin layer contains a filler made of an inorganic material.

3. 3. The heat sink integrated insulating circuit board according to claim 1, wherein the heat sink is provided with heat dissipation fins.

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