A copper alloy and use thereof

Abstract

The present application relates to a kind of copper alloys, comprising: B 0.001wt%-0.005wt%;P0.001wt%-0.003wt%;Sn 0.001wt%-0.006wt%;X 0.001wt%-0.009wt%;And Cu and impurity balance;Wherein, the X is selected from at least one of: Y, La, or Ce.The copper alloy of the present application realizes the hardness of HV95-HV110, the tensile strength of 280MPa-330Mpa, the conductivity of not less than 97%IACS and the thermal conductivity of not less than 388W / (m·k) by controlling the mass percentage of added element;In addition, after keeping 10min at 350 DEG C, the hardness of the copper alloy is higher than 98% of the original hardness of the copper alloy, which reflects excellent high-temperature softening resistance performance, at the same time, after keeping 10min at 350 DEG C for three times, the hardness of the copper alloy is higher than 90% of the original hardness of the copper alloy, which reflects excellent high-temperature stability, can meet the performance requirement of IGBT heat dissipation substrate.

Description

Technical Field

[0001] This invention relates to the field of copper alloy technology, and more particularly to a copper alloy and its applications. Background Technology

[0002] With the continuous advancement of high-current electronic devices, such as frequency converters, the demands on the performance of Insulated Gate Bipolar Transistor (IGBT) chips are also increasing, including improving their current handling capacity. However, the increased current handling capacity of IGBT chips leads to a gradual increase in the heat generated during operation. If this heat is not dissipated in time, it will seriously affect the normal operation of the IGBT chip and other electronic components on the circuit board, and in extreme cases, it may lead to short circuit events. Therefore, heat dissipation of IGBT chips is particularly critical.

[0003] Currently, IGBT chips are mainly cooled by using copper-based IGBT heat sinks. Typically, copper-based materials are chosen from tough copper or oxygen-free copper, which have high thermal and electrical conductivity and require a conductivity of 97% IACS or higher. However, in power modules that handle high currents, tough copper or oxygen-free copper cannot meet the heat resistance required for high-temperature soldering during the power module assembly stage. This can easily lead to softening, deformation, and warping of the heat sink, making it impossible to maintain the flatness of the heat sink surface. Consequently, the power module cannot be assembled, and in severe cases, insufficient heat dissipation may cause the IGBT chip to overheat and fail.

[0004] Therefore, there is an urgent need for a copper alloy that simultaneously possesses high thermal conductivity, high electrical conductivity, and high heat resistance. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a copper alloy and its applications.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention is to provide a copper alloy comprising:

[0008]

[0009]

[0010] Wherein, X is selected from at least one of Y, La, or Ce.

[0011] In this invention, 0.001wt%-0.005wt% of boron significantly improves the mechanical and processing properties of copper alloys, while having a negligible effect on the electrical conductivity of copper. In addition, boron can react with impurities in copper alloys, such as lead and bismuth, to form high-melting-point compounds. These compounds are uniformly distributed in the grains in the form of tiny spherical particles, thereby achieving grain refinement.

[0012] In this invention, 0.001wt%-0.003wt% of P can fully exert its degassing and deoxidizing effects. If the deoxidation effect is not good, it will lead to the oxidation of Sn during the casting process, resulting in some Sn existing in the form of oxides. This situation will have a negative impact on the heat resistance of tin-containing copper alloys. In addition, Cu3P and tin-phosphorus intermetallic compounds formed by P with Cu and Sn can improve the high-temperature softening resistance of the alloy. It is worth noting that although the addition of P can improve the performance of the alloy, it will also significantly reduce the electrical conductivity and thermal conductivity. For example, it will be impossible to obtain a copper alloy with at least 97% IACS conductivity.

[0013] In this invention, 0.001wt%-0.006wt% of Sn significantly improves the hardness and strength of copper alloys, while also enhancing their heat resistance. Due to the significant difference in the radius between Sn atoms and Cu atoms, Sn mainly exists in copper alloys through interstitial solid solution. Compared with substitutional solid solution, this solid solution method produces a higher degree of lattice distortion in the crystal, effectively pinning dislocations, hindering dislocation movement, and suppressing the formation of recrystallization nuclei. Consequently, it increases the recrystallization temperature and prevents the alloy grains from rapidly recrystallizing and growing under high-temperature conditions, thereby significantly improving the strength and heat resistance of copper alloys.

[0014] In this invention, rare earth elements Y, La, or Ce can significantly improve the mechanical and heat resistance properties of copper alloys. Y can effectively refine the dendritic grid structure of copper alloy casting, resulting in a finer grain structure after annealing, thereby enhancing its mechanical and heat resistance properties. La or Ce have extremely low solid solubility in copper alloys, but they are very beneficial for improving the mechanical properties of copper alloys and have little effect on electrical conductivity. La or Ce can form high-melting-point compounds with impurities in copper alloys, such as lead and bismuth, which are uniformly distributed in the grains in the form of fine spherical particles, thereby refining the grains and further improving the high-temperature plasticity of the alloy.

[0015] Preferably, the mass ratio of P to Sn is 1:(1.0-4.0).

[0016] In this invention, both P and Sn have the effect of strengthening the matrix and enhancing the strength of the alloy. However, the addition of these two elements will also affect the conductivity of the copper alloy. P and Sn may also form tin-phosphorus intermetallic compounds. The formation of such compounds is beneficial to reducing the lattice distortion of the copper matrix, thereby optimizing the conductivity of the alloy. It is worth mentioning that tin-phosphorus intermetallic compounds belong to the category of compounds with high hardness, high wear resistance, and high melting point. Their presence has a positive impact on improving the hardness of the alloy and enhancing the alloy's resistance to high-temperature softening.

[0017] Preferably, the volume percentage of the tin-phosphorus intermetallic compound formed by P and Sn in the copper alloy is 0.015%-0.025%.

[0018] Although tin-phosphorus intermetallic compounds have a positive effect on improving the hardness and high-temperature softening resistance of copper alloys, their content does not increase proportionally. When the content of tin-phosphorus intermetallic compounds is too high, although the strength, hardness and high-temperature softening resistance of the alloy increase, its plasticity and conductivity will decrease rapidly, which will have a negative impact on subsequent machining and final use.

[0019] Preferably, the mass percentage of Y is not higher than 0.003%.

[0020] Preferably, the mass percentage of La is not higher than 0.003%.

[0021] Preferably, the mass percentage of Ce is not higher than 0.003%.

[0022] Excessive mass percentages of Y, La, or Ce may negatively affect the electrical and thermal conductivity of copper alloys; therefore, their mass percentages should not exceed 0.003%.

[0023] Preferably, the number of spot-like inclusions with a size ≥0.8μm within the grains and grain boundaries of the copper alloy is less than 20 per 1000μm. 2 .

[0024] Boron (B) and rare earth elements Y, La, or Ce have a synergistic effect: On the one hand, Y, La, or Ce have strong chemical reactivity and a much stronger affinity for oxygen than copper. The resulting oxides have high melting points and low densities, effectively deoxidizing the copper. Simultaneously, they can combine with hydrogen to form low-density hydrides, which float to the surface of the molten copper, decompose at high temperatures, and release hydrogen gas, or be oxidized and removed into the slag. On the other hand, Y, La, or Ce also significantly remove other harmful elements. They readily form high-melting-point compounds, most of which remain solid and are discharged from the liquid copper along with the slag, thus removing harmful impurities within the grains and grain boundaries. When B is added simultaneously, the slag removal rate increases by more than 8% compared to using rare earth elements or B alone. The number and size of large, spot-like inclusions within the grains and grain boundaries decrease, significantly improving the alloy's electrical and thermal conductivity, enhancing its processing plasticity, and reducing crack formation.

[0025] Preferably, the hardness of the copper alloy is HV95-HV110.

[0026] Preferably, the tensile strength of the copper alloy is 280MPa-330MPa.

[0027] Preferably, the conductivity of the copper alloy is not less than 97% IACS.

[0028] Preferably, the thermal conductivity of the copper alloy is not less than 388 W / (m·K).

[0029] Preferably, after the copper alloy is held at 350°C for 10 minutes, the hardness of the copper alloy is higher than 98% of the original hardness of the copper alloy.

[0030] The heat resistance of a material refers to the change in its room temperature mechanical properties after being heated to different temperatures under certain heat preservation conditions. Generally, the hardness of copper alloys is maintained above 80% (i.e., the ratio of room temperature hardness after heat preservation treatment to the original hardness) as the benchmark for judging whether the material has softened. For copper alloys used in IGBT heat sink substrates, in order to meet the assembly requirements under high-temperature welding conditions, it is appropriate to use the ratio of residual hardness after holding at 350℃ for 10 minutes to the original hardness to evaluate its heat resistance. When the heat resistance of the material is poor, the grains in the structure are prone to grow rapidly, which leads to a decrease in the hardness and strength of the material, and in turn, softening, deformation and warping of the heat sink substrate, making it impossible to maintain surface flatness, thus making it impossible to successfully complete the assembly of the power module. In severe cases, insufficient heat dissipation may cause the IGBT chip temperature to be too high and fail.

[0031] Preferably, after the copper alloy is held at 350°C for 10 minutes three times consecutively, the hardness of the copper alloy is higher than 90% of the original hardness of the copper alloy.

[0032] The assembly process of high-current power modules requires three high-temperature treatment steps. These steps are crucial to the thermal stability of the copper alloy used in the IGBT heat sink substrate, because any softening of the substrate will lead to the failure of the power module assembly.

[0033] A second aspect of the present invention is to provide an application of the copper alloy as described above in an IGBT heat sink substrate.

[0034] The present invention adopts the above technical solution and has the following technical effects compared with the prior art:

[0035] The copper alloy of this invention achieves a hardness of HV95-HV110, a tensile strength of 280MPa-330MPa, an electrical conductivity of not less than 97% IACS, and a thermal conductivity of not less than 388W / (m·k) by controlling the added elements and their mass percentages. Furthermore, after being held at 350°C for 10 minutes, the hardness of the copper alloy is 98% higher than its original hardness, demonstrating excellent high-temperature softening resistance. Simultaneously, after being held at 350°C for 10 minutes three times consecutively, the hardness of the copper alloy is 90% higher than its original hardness, demonstrating excellent high-temperature stability, thus meeting the performance requirements of IGBT heat dissipation substrates. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0038] The present invention will be further described below with reference to specific embodiments, but these are not intended to limit the scope of the invention.

[0039] Example

[0040] This embodiment provides a copper alloy, comprising:

[0041]

[0042] Wherein, X is selected from at least one of Y, La, or Ce, and the mass percentage of Y, La, or Ce is not higher than 0.003%.

[0043] Examples 1-14

[0044] The copper alloys corresponding to Examples 1-14 are shown in the table below:

[0045]

[0046]

[0047] Comparative Examples 1-15

[0048] Comparative Examples 1-15 provide another copper alloy, the composition of which is shown in the table below:

[0049]

[0050] It should be noted that: Comparative Example 1 is a C11000 alloy, and Examples 1-14 and Comparative Examples 2-15 are based on Comparative Example 1 with the addition of at least one of B, P, Sn, Y, La, or Ce. That is, "Cu and impurities" in Examples 1-14 and Comparative Examples 2-15 should be regarded as the composition of Comparative Example 1.

[0051] Application Examples

[0052] Examples 1-14 and Comparative Examples 1-15 were used to prepare copper alloy strips, and the prepared copper alloy strips were tested: 25μm × 40μm (1000μm) 2 The following table shows the results regarding the number of inclusions ≥0.8 μm in a rectangle, the volume percentage of tin-phosphorus intermetallic compounds, hardness, room temperature tensile strength, electrical conductivity, thermal conductivity, and high-temperature softening resistance in a 20 mm × 20 mm area:

[0053]

[0054]

[0055] Note: "Tin-phosphorus intermetallic compound / %" is the volume percentage of the tin-phosphorus intermetallic compound formed by P and Sn in the copper alloy; "High-temperature softening resistance - single test" is the ratio of the hardness of the copper alloy after being held at 350°C for 10 minutes to the "hardness (room temperature)"; "High-temperature softening resistance - three consecutive tests" is the ratio of the hardness of the copper alloy after being held at 350°C for 10 minutes, naturally cooled to room temperature, and the above process repeated twice (a total of three times) to the "hardness (room temperature)".

[0056] As shown in the table above: Comparing Example 3 and Example 4, element B significantly improves the hardness, tensile strength, and heat resistance of the copper alloy, while having a negligible effect on the electrical conductivity of copper; comparing Example 5 and Comparative Example 4, element P can improve the alloy's performance, but it also significantly reduces electrical and thermal conductivity; comparing Example 9 and Comparative Example 2, element Sn can improve the alloy's performance, but its effect on electrical and thermal conductivity is very significant; comparing Example 9 and Example 10, element P and element Sn have a synergistic effect. The addition ratio of these elements has a positive impact on improving the hardness of the alloy and enhancing its resistance to high-temperature softening. Comparative Example 14 and Comparative Example 12 show that rare earth elements Y, La, or Ce can significantly improve mechanical properties and heat resistance, while having no significant effect on electrical conductivity and thermal conductivity. Comparative Example 11 and Comparative Example 15 show that element B and rare earth elements Y, La, or Ce have a synergistic effect, reducing the number and size of large spot-like inclusions in the grains and grain boundaries, thereby significantly improving its mechanical properties and heat resistance.

[0057] In summary, the copper alloy of the present invention achieves a hardness of HV95-HV110, a tensile strength of 280MPa-330MPa, an electrical conductivity of not less than 97% IACS, and a thermal conductivity of not less than 388W / (m·k) by controlling the added elements and their mass percentages. Furthermore, after being held at 350°C for 10 minutes, the hardness of the copper alloy is 98% higher than its original hardness, demonstrating excellent high-temperature softening resistance. Simultaneously, after being held at 350°C for 10 minutes three times consecutively, the hardness of the copper alloy is 90% higher than its original hardness, demonstrating excellent high-temperature stability, and can meet the performance requirements of IGBT heat dissipation substrates.

[0058] The above description is merely a preferred embodiment of the present invention and does not limit the implementation and protection scope of the present invention. Those skilled in the art should realize that any equivalent substitutions and obvious changes made based on the content of this specification should be included within the protection scope of the present invention.

Claims

1. A copper alloy, characterized in that, It consists of the following elements: B 0.001wt%-0.005wt%; P 0.001wt%-0.003wt%; Sn 0.001wt%-0.006wt%; X 0.001wt%-0.009wt%; and; Cu and impurity balance; Wherein, X is selected from at least one of Y, La, or Ce; The copper alloy has a conductivity of not less than 97% IACS; after being held at 350°C for 10 minutes, the hardness of the copper alloy is higher than 98% of its original hardness; after being held at 350°C for 10 minutes three times consecutively, the hardness of the copper alloy is higher than 90% of its original hardness.

2. The copper alloy according to claim 1, characterized in that, The mass ratio of P to Sn is 1:(1.0-4.0).

3. The copper alloy according to claim 1 or 2, characterized in that, The volume percentage of the tin-phosphorus intermetallic compound formed by P and Sn in the copper alloy is 0.015%-0.025%.

4. The copper alloy according to claim 1, characterized in that, The mass percentage of Y is no higher than 0.003%.

5. The copper alloy according to claim 1, characterized in that, The mass percentage of La is no higher than 0.003%.

6. The copper alloy according to claim 1, characterized in that, The mass percentage of Ce is no higher than 0.003%.

7. The copper alloy according to claim 1, characterized in that, The number of spot-like inclusions with a size ≥0.8μm within the grains and grain boundaries of the copper alloy is less than 20 per 1000μm. 2 .

8. The copper alloy according to claim 1, characterized in that, The copper alloy has a hardness of HV95-HV110; a tensile strength of 280MPa-330MPa; and a thermal conductivity of not less than 388W / (m·k).

9. The application of a copper alloy as described in any one of claims 1-8 in an IGBT heat sink substrate.

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