Clad material

Abstract

To provide a clad material that can suppress the problem of thermal warping in high-temperature environments when used in semiconductors. [Solution] In a clad material in which a first metal layer made of Cu or a Cu alloy and a second metal layer made of Al or an Al alloy are roll-bonded, the 0.2% yield strength of the second metal layer is 140 MPa or less, and the K value calculated by 0.2% yield strength of the second metal layer + the thickness ratio of the second metal layer when the total thickness of the first and second metal layers is 1 × 1872 is 315 or less, and it is preferable that the warpage in the thickness direction of a 100 mm wide × 100 mm long test piece is 1.0 mm or less when heated to 250°C.

Description

Technical Field

[0001] The present invention relates to a clad material.

Background Art

[0002] An aluminum (Al)-copper (Cu) clad material (hereinafter also referred to as "AlCu clad material" or simply "clad material") is suitably used as a material for wiring members for battery connection, wiring members for capacitors, and intermediate components for connecting a Cu portion on which a Si semiconductor power device chip is mounted and an Al portion such as a radiator, among other applications.

[0003] For example, in Patent Document 1, as an AlCu clad material, when the average crystal grain size of crystal grains in the central portion in the thickness direction of the Cu layer is defined as Dcc, and the average crystal grain size in the vicinity of the interface in the Cu layer at a position 0.5 μm away from the interface between the Cu layer and the intermetallic compound layer is defined as Dcs, there is an invention of a clad material in which Dcs ≦ 0.5×Dcc, and the average thickness of the intermetallic compound layer is 0.5 μm to 10 μm.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the clad material disclosed in the aforementioned Patent Document 1, fine crystal grains are formed at the interface portion between the intermetallic compound layer and the Cu layer or between the intermetallic compound layer and the Al layer so as to satisfy a predetermined grain size ratio with respect to the average crystal grain size at the central portion of the Cu layer or the Al layer. As a result, in the clad material of Patent Document 1, during diffusion annealing, the crystal grains constituting the intermetallic compound layer also have fine and random crystal orientations, and the continuous film of aluminum oxide that conventionally existed in the intermetallic compound is fragmented and dispersed, which is a useful technique in that excellent bonding strength can be obtained.

[0006] On the other hand, in recent years, with the practical application of silicon carbide (SiC) semiconductor power devices, which have superior switching performance and high-temperature operating characteristics compared to the aforementioned Si semiconductor power devices, the problem of thermal warping of cladding materials that occurs in high-temperature environments when semiconductors are used is becoming more pronounced. The objective of the present invention is to provide a clad material that can suppress the problem of thermal warping in high-temperature environments when used in semiconductors. [Means for solving the problem]

[0007] The inventors of the present invention have discovered that even with the same configuration as the clad material having the above-described laminated structure of Al and Cu, a clad material can be obtained in which the problem of thermal warping can be suppressed by adopting a specific layer configuration in which the ratio of the 0.2% yield strength of the Al layer to the thickness of the Al layer is within a predetermined range, thereby arriving at the present invention.

[0008] In other words, the clad material of the present invention is a clad material in which a first metal layer made of Cu or a Cu alloy and a second metal layer made of Al or an Al alloy are roll-bonded, wherein the 0.2% yield strength of the second metal layer is 140 MPa or less, and the K value calculated by (0.2% yield strength of the second metal layer + thickness ratio of the second metal layer when the total thickness of the first and second metal layers is 1 × 1872) is 315 or less.

[0009] The clad material of the present invention preferably exhibits a curvature of 1.0 mm or less in the thickness direction when a test piece measuring 100 mm in width and 100 mm in length is heated to 250°C.

[0010] In the clad material of the present invention, it is preferable that the thickness ratio of the second metal layer to the total thickness of the first metal layer and the second metal layer is 0.15 or less.

[0011] In the clad material of the present invention, it is preferable that the first metal layer is composed of pure Cu with a purity of 99.90% or higher.

[0012] In the clad material of the present invention, it is preferable that the second metal layer is composed of pure Al with a purity of 99.90% or higher.

[0013] In the clad material of the present invention, the total thickness of the first metal layer (thickness t1) and the second metal layer (thickness t2) is preferably 0.4 to 3.5 mm.

[0014] In the clad material of the present invention, it is preferable that the cross-sectional Vickers hardness of the second metal layer is 60 HV or less. [Effects of the Invention]

[0015] This invention provides a cladding material that can suppress the problem of thermal warping in high-temperature environments when semiconductors are used, and therefore is a useful technology for, for example, the manufacture of SiC semiconductor power devices. [Brief explanation of the drawing]

[0016] [Figure 1] A schematic cross-sectional view showing an example of the clad material of the present invention. [Modes for carrying out the invention]

[0017] Figure 1 shows an example of a schematic cross-sectional view of the clad material of the present invention. The clad material 1 of the present invention is formed by rolling and joining a first metal layer 2 made of Cu or a Cu alloy and a second metal layer 3 made of Al or an Al alloy, the 0.2% yield strength of the second metal layer is 140 MPa or less, and the K value calculated by (0.2% yield strength of the second metal layer + thickness ratio of the second metal layer when the total thickness of the first and second metal layers is 1 × 1872) is 315 or less. The characteristics are described below.

[0018] The clad material of the present invention can suppress thermal warping in high-temperature environments by 12% or more, even with the same thickness ratio of the second metal layer (Al layer), by adjusting the 0.2% yield strength of the second metal layer made of Al or an Al alloy, as well as adjusting the thickness ratio of the first and second metal layers. The clad material of the present invention is tempered to have a 0.2% yield strength of 140 MPa or less for the second metal layer. The clad material of the present invention suppresses thermal warping by intentionally yielding the second metal layer using thermal stress, that is, by reducing the rigidity of the second metal layer in the high-temperature environment used for semiconductors, thereby causing the second metal layer to be pulled by the first metal layer. For the same reasons as above, the clad material according to the embodiment of the present invention preferably has a 0.2% yield strength of 100 MPa or less for the second metal layer, more preferably 80 MPa or less, even more preferably 60 MPa or less, and still more preferably 50 MPa or less.

[0019] The clad material of the present invention has a K value of 315 or less, calculated by the 0.2% yield strength of the second metal layer + the thickness ratio of the second metal layer when the total thickness of the first and second metal layers is 1 × 1872. In addition to adjusting the 0.2% yield strength of the second metal layer as described above, the clad material of the present invention can ensure an excellent thermal warping suppression effect by also adjusting the thickness ratio of the first and second metal layers in order to reduce the rigidity of the second metal layer in the high-temperature environment when used in semiconductors. Furthermore, for the same reasons as above, the clad material according to the embodiment of the present invention preferably has a K value of 270 or less, more preferably 250 or less, and even more preferably 200 or less.

[0020] SiC semiconductor power devices are required to operate in high-temperature environments of around 250°C for applications such as engine peripherals, underground resource drilling, and space exploration equipment. The clad material according to the embodiment of the present invention is preferable because it can suppress thermal warping in the high-temperature environment described above by reducing the warping in the thickness direction of a 100 mm wide x 100 mm long test piece to 1.0 mm or less when heated to 250°C. Furthermore, for the same reasons as above, the clad material according to the embodiment of the present invention is more preferably 0.8 mm or less, and even more preferably 0.5 mm or less, when a 100 mm wide x 100 mm long test piece is heated to 250°C.

[0021] In the clad material according to the embodiment of the present invention, the thickness ratio of the second metal layer is preferably 0.15 or less, where the total thickness of the first metal layer and the second metal layer is taken as 1. Thereby, the clad material of the present invention reduces the rigidity of the second metal layer in a high-temperature environment during use of a semiconductor, secures a more excellent thermal warpage suppression effect, and by increasing the thickness ratio of the first metal layer, the effect of improving electrical conductivity and thermal conduction (heat dissipation) performance can also be expected. For the same reason as described above, in the clad material according to the embodiment of the present invention, the thickness ratio of the second metal layer is preferably 0.13 or less, more preferably 0.10 or less, and even more preferably 0.08 or less. Note that if the thickness ratio of the second metal layer is too small, there is a risk that the inherent connectivity of the clad material with the Al member will be impaired. For this reason, in the clad material according to the embodiment of the present invention, the thickness ratio of the second metal layer is preferably 0.01 or more, and more preferably 0.03 or more.

[0022] In the clad material of the present invention, the first metal layer and the second metal layer described above are roll-bonded, whereby electrical conductivity and thermal conduction (heat dissipation) performance as a connection material for wiring members, heat radiators and the like can be secured. In the clad material according to the embodiment of the present invention, Cu or a Cu alloy is applied as the first metal layer from the viewpoint of improving electrical conductivity and thermal conduction (heat dissipation) performance. Among them, it is preferable to use pure Cu with a purity of 99.90% or more, typified by C1020 and C1100 specified in JIS H 3100.

[0023] Further, in the clad material according to the embodiment of the present invention, Al or an Al alloy is applied as the second metal layer from the viewpoint of achieving both thermal conduction (heat dissipation) performance and weight reduction. When an Al alloy is applied, for example, A3003, A5052 and the like specified in JIS H 4000 are preferably selected. However, pure Al is suitably applied as the second metal layer, and among others, it is preferable to apply pure Al with a purity of 99.90% or more, typified by A1050 and A1100 specified in JIS H 4000.

[0024] Furthermore, in the context of using the clad material according to the embodiment of the present invention as a wiring material for battery connections, a wiring material for capacitors, and an intermediate component for connecting a Cu part on which a Si semiconductor power device chip is mounted with an Al part such as a heat sink, it is preferable that the total thickness of the thickness t1 of the first metal layer and the thickness t2 of the second metal layer be in the range of 0.4 to 3.5 mm.

[0025] Furthermore, in the clad material according to the embodiment of the present invention, from the viewpoint of reducing the rigidity of the second metal layer in the high-temperature environment when used in semiconductors, it is preferable that the cross-sectional Vickers hardness of the second metal layer be 60 HV or less, and preferably 20 HV or more. Furthermore, the 0.2% yield strength and Vickers hardness of the clad material can be adjusted by the degree of processing during the finish rolling process in the conventional clad material manufacturing method, which involves pressure welding, diffusion annealing, and finish rolling. [Examples]

[0026] Clad materials representing the present invention and comparative examples were prepared, and their properties were investigated. Specifically, first, pure Cu materials (C1100, C1020) for the first metal layer and Al or Al alloy materials (A1050, A1100, A3003, A5052) for the second metal layer were prepared, as shown in Table 1. Then, to obtain a clad material with the configuration shown in Table 1, a material was subjected to pressure welding and diffusion annealing to form a two-layer structure of a first metal layer 2 / second metal layer 3 as shown in Figure 1, and then finished rolling was performed with the degree of processing adjusted. From each of the clad materials obtained as Examples 1-4 of the present invention and Comparative Examples 1 and 2 above, test specimens measuring 100 mm in width and 100 mm in length were taken and heated to 250°C, after which the thermal warping (displacement in the thickness direction) was measured. The results are shown in Table 1.

[0027] [Table 1]

[0028] Both the clad materials in Comparative Example 1 and Comparative Example 2 had a K value exceeding 315, calculated by multiplying the 0.2% yield strength of the second metal layer by the thickness ratio of the second metal layer (where the total thickness of the first and second metal layers is 1) by 1872. Furthermore, the clad material in Comparative Example 2 had a 0.2% yield strength of the second metal layer exceeding 140 MPa. As a result, both the clad materials in Comparative Example 1 and Comparative Example 2 exhibited thermal warping of over 1.0 mm in test specimens heated to 250°C.

[0029] In contrast, the clad materials of Examples 1 to 5 of the present invention all had a 0.2% yield strength of 140 MPa or less for the second metal layer. Furthermore, by setting the K value, calculated by the 0.2% yield strength of the second metal layer + the thickness ratio of the second metal layer when the total thickness of the first and second metal layers is set to 1 × 1872, to 315 or less for all of the clad materials of Examples 1 to 5 of the present invention, the thermal warping of the test specimens heated to 250°C was less than 1.0 mm, and in particular, the clad material of Example 5 of the present invention was confirmed to have a thermal warping of less than 0.5 mm. [Explanation of Symbols]

[0030] 1. Clad material 2 First metal layer (Cu) 3 Second metal layer (Al)

Claims

1. A clad material in which a first metal layer made of Cu or a Cu alloy and a second metal layer made of Al or an Al alloy are roll-joined, wherein the 0.2% yield strength of the second metal layer is 140 MPa or less, and the K value calculated by (0.2% yield strength of the second metal layer + thickness ratio of the second metal layer when the total thickness of the first and second metal layers is 1 × 1872) is 315 or less.

2. The clad material according to claim 1, wherein the curvature in the thickness direction of a test piece measuring 100 mm in width and 100 mm in length is 1.0 mm or less when heated to 250°C.

3. The clad material according to claim 1 or claim 2, wherein the thickness ratio of the second metal layer to the total thickness of the first metal layer and the second metal layer is 0.15 or less.

4. The clad material according to claim 1, wherein the first metal layer is composed of pure Cu with a purity of 99.90% or higher.

5. The clad material according to claim 1, wherein the second metal layer is composed of pure Al with a purity of 99.90% or higher.

6. The clad material according to claim 1 or claim 2, wherein the total thickness of the thickness t1 of the first metal layer and the thickness t2 of the second metal layer is 0.4 to 3.5 mm.

7. The clad material according to claim 1 or claim 2, wherein the cross-sectional Vickers hardness of the second metal layer is 60 HV or less.

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