A method for preparing a high-density powder injection molded copper radiator

Abstract

The present invention relates to a preparation method of a high-density powder injection molded copper heat sink, which comprises pre-oxidizing a coarse copper powder, mixing it with a certain proportion and specification of fine copper powder and copper alloy powder, and then kneading it with a binder to prepare a feed, and then performing injection molding and degreasing, and then using a vacuum sintering furnace to successively perform hydrogen atmosphere sintering, vacuum sintering and pressure sintering to obtain a high-density, high-performance powder injection molded copper heat sink component sintered part. Compared with the preparation method of powder injection molding in the prior art, the preparation method proposed by the present invention realizes a variety of sintering densification promoting mechanisms such as pre-oxidation activation sintering, fine powder activation sintering, liquid phase sintering, vacuum and pressure sintering combined, which can significantly improve the sintering density and comprehensive performance of the material, and can meet the performance requirements of high-performance, complex structure copper heat sinks for high heat flux semiconductors.

Description

Technical Field

[0001] The invention relates to the technical field of powder metallurgy, and in particular to a method for preparing a high-density powder injection-molded copper radiator. Background Art

[0002] With the continuous development of semiconductor devices, their miniaturization and high power characteristics have been significantly enhanced, which has further increased the heat flux density. As the temperature rises, semiconductor devices are prone to problems such as increased failure rate and reduced service life. Metal copper has excellent thermal conductivity and is an ideal material for high heat flux power semiconductor heat sinks. In order to further improve the heat dissipation capacity of copper heat sinks, the number of fins and the complexity of the shape of the heat sink should be increased as much as possible in terms of structural design to maximize the specific surface area of ​​the heat sink, thereby improving the heat exchange efficiency between the heat sink surface and the cooling medium.

[0003] However, with the increasing complexity of the fin structure of the radiator, traditional processes are often no longer able to meet the performance requirements of copper radiators. For example, for the currently commonly used pin-fin radiators, the traditional forging process makes it difficult to prepare radiators with a pin-fin spacing of ≤1.5mm. For example, although the powder injection molding technology can solve the forming problem of complex structure radiators, for copper-based powder injection molding parts, if pure copper powder is used for simple solid-phase sintering, the density is difficult to exceed 95%. The presence of a large number of pores in the material leads to serious losses in thermal conductivity and mechanical properties, and the sealing of the components often does not meet the application requirements of liquid cooling. Therefore, in the prior art, the degree of densification of copper radiator parts prepared by powder injection molding technology is low, resulting in a decrease in their overall performance, which limits the wide application of the product. Summary of the invention

[0004] The purpose of the present invention is to provide a method for preparing a high-density powder injection molded copper heat sink, which overcomes the problem that powder injection molding in the prior art is difficult to prepare a high-density copper-based heat sink, and can effectively improve the material density and comprehensive performance.

[0005] To this end, the present invention provides a method for preparing a high-density powder injection molded copper heat sink, which comprises the following steps:

[0006] S1. Pre-oxidizing the crude copper powder, and then uniformly mixing it with the fine copper powder and the copper alloy powder to prepare a raw material powder; wherein the particle size of the fine copper powder is smaller than that of the crude copper powder;

[0007] S2, mixing the raw material powder and the binder uniformly, and then sequentially performing injection molding and degreasing to prepare a green body;

[0008] S3, sintering the green body, wherein the sintering includes sequentially sintering in a hydrogen atmosphere, vacuum sintering, and pressure sintering; cooling after the sintering is completed, thus preparing a copper radiator component.

[0009] According to the technical solution of the present invention, the use of the above-mentioned raw material powder can promote sintering densification from multiple aspects. Specifically, the coarse copper powder can generate new ecological atoms under subsequent reducing conditions after pre-oxidation, realize activated sintering, and then promote sintering densification; the sintering activity of fine copper powder is relatively high, which is beneficial to promote sintering densification; the melting point of copper alloy powder is lower than that of pure copper. By using low-melting-point copper alloy powder, a small amount of liquid phase can be produced during the sintering process, thereby promoting sintering densification.

[0010] Furthermore, in step S1, in the raw material powder, the mass fraction of the fine copper powder is 15-45%, and the mass fraction of metals other than copper in the copper alloy powder is 0-2%.

[0011] In some embodiments, in the raw material powder, the mass fraction of metal other than copper in the copper alloy powder is greater than 0 and less than or equal to 2%.

[0012] Furthermore, the particle size of the crude copper powder is 325-800 meshes.

[0013] Furthermore, the particle size of the fine copper powder is less than or equal to 600 mesh.

[0014] Furthermore, in step S1, the pre-oxidation is performed under air atmosphere.

[0015] Furthermore, in step S1, the coarse copper powder and the fine copper powder are atomized copper powder.

[0016] Further, in step S1, the copper alloy includes one or a combination of two or more selected from the following group: copper-zinc alloy (CuZn), copper-tin alloy (CuSn), copper-chromium alloy (CuCr), copper-zirconium alloy (CuZr), copper-manganese alloy (CuMn), and copper-manganese-nickel alloy (CuMnNi).

[0017] According to the technical solution of the present invention, in step S2, the type of binder is not limited, and commonly used binders in the art may be used, such as but not limited to paraffin, polyethylene glycol, polypropylene, polyethylene, stearic acid, ethylene-vinyl acetate copolymer (EVA), etc.

[0018] Furthermore, in step S2, the degreasing is one or a combination of two or more of solvent degreasing, catalytic degreasing, and low-temperature degreasing under a hydrogen atmosphere.

[0019] Further, in step S3, the green body is placed in a sintering furnace for sintering, and hydrogen atmosphere sintering is performed before the temperature is raised to 700°C; vacuum sintering is performed after the temperature is raised to 700°C, and the maximum temperature of the vacuum sintering is greater than or equal to the melting point of the copper alloy powder and less than or equal to 1080°C; after the vacuum sintering is completed, the temperature is maintained unchanged and pressure sintering is performed in an inert gas atmosphere.

[0020] According to the technical solution of the present invention, through hydrogen atmosphere sintering, vacuum sintering and pressure sintering, it is possible to further compress the internal pores of the material and improve the density of the material under high-temperature metal softening conditions by utilizing the effect of external gas pressure.

[0021] Furthermore, in the vacuum sintering step, when the temperature is raised to 100° C. from the maximum temperature, the temperature is raised to the maximum temperature at a rate of 1 to 2° C. / min.

[0022] Furthermore, in the pressure sintering step, the pressure of the inert gas is greater than 1 bar, and the flow rate of the inert gas is greater than 1 m / s. 3 / min, the pressure and heat preservation time is 20 to 40 minutes.

[0023] Furthermore, the inert gas includes one or a combination of two or more selected from the following group: helium, neon, and argon.

[0024] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0025] Compared with the conventional preparation technology of powder injection molding, the preparation method proposed in the present invention realizes the activation sintering effect of pre-oxidized coarse copper powder, the activation sintering effect of fine copper powder, and the liquid phase sintering effect of low melting point alloy powder. It also adopts a variety of mechanisms to promote sintering densification, such as hydrogen atmosphere sintering, vacuum sintering and pressure sintering. It can significantly improve the sintering densification, the material density reaches more than 98%, and the thermal conductivity is ≥300W / (m·K), which can meet the performance requirements of high heat flux semiconductors for high-performance, complex structure copper heat sinks.

[0026] Furthermore, the preparation method of the present invention is particularly suitable for producing various copper-based parts, because the density and physical properties of the products prepared by the present invention are greatly improved. DETAILED DESCRIPTION

[0027] The exemplary embodiments of the present disclosure will be described in more detail below. It should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0028] Example 1

[0029] S1. Screen 325-800 mesh atomized pure copper powder as raw material for crude copper powder, use a mesh belt furnace, use air as atmosphere, keep warm at 400 ° C for 2h, and pre-oxidize the surface. Take 800 mesh atomized pure copper powder as raw material for fine copper powder, mix the fine copper powder with the pre-oxidized crude copper powder in a mass ratio of 1:2 to obtain a first powder mixture. Take 500 mesh CuZr8 alloy powder, mix the CuZr8 alloy powder with the first powder mixture in a mass ratio of 1:19 to prepare a raw material powder. In the raw material powder, the mass fraction of Zr element is 0.4%.

[0030] S2. The raw material powder is mixed with an injection molding binder (paraffin 50wt.%, polypropylene 25wt.%, polyethylene 23wt.%, stearic acid 2wt.%) in a volume ratio of 3:2 to prepare a feed material. The feed material is injection molded into a radiator green body using an injection molding machine and a matching mold. The radiator green body is catalytically degreased to prepare a green body.

[0031] S3. Place the green body in a vacuum sintering furnace for sintering. First, introduce 1L / min of hydrogen atmosphere and heat to 700℃ at a rate of 3℃ / min. After 700℃, vacuum sintering is performed with a vacuum degree of ≤50Pa. Continue to heat to 950℃ at a rate of 3℃ / min, then heat to 1050℃ at a rate of 1.5℃ / min, and keep warm for 90min. Then maintain the temperature at 1050℃ for more than 1min. 3 / min, high-pressure argon is injected into the furnace until the pressure reaches 5 bar, and then the temperature is kept at 30 minutes. After the sintering is completed, the temperature is cooled to obtain high-density and high-performance copper radiator parts, with a density of more than 98% and a thermal conductivity of ≥300W / (m·K).

[0032] Example 2

[0033] S1. Take 400-mesh atomized pure copper powder as the raw material of crude copper powder, use a mesh belt furnace, use air as the atmosphere, keep warm at 400°C for 2h, and perform surface pre-oxidation. Take 200-mesh atomized pure copper powder as the raw material of fine copper powder, mix the fine copper powder with the pre-oxidized crude copper powder in a mass ratio of 1:3 to obtain a first powder mixture. Take 300-mesh CuMn30 alloy powder, mix the CuMn30 alloy powder with the first powder mixture in a mass ratio of 1:19 to prepare a raw material powder. In the raw material powder, the mass fraction of Mn element is 1.5%.

[0034] S2. The raw material powder is mixed with an injection molding binder (polyethylene glycol 40wt.%, EVA 35wt.%, polyethylene 20wt.%, stearic acid 5wt.%) in a volume ratio of 3:2 to prepare a feed material. The feed material is injection molded into a radiator green body using an injection molding machine and a matching mold. The radiator green body is subjected to low-temperature thermal degreasing (500°C, 1h) under hydrogen conditions to prepare a green body.

[0035] S3. Place the green body in a vacuum sintering furnace for sintering. First, introduce 1L / min of hydrogen atmosphere and heat to 700℃ at a rate of 4℃ / min. After 700℃, vacuum sintering is performed with a vacuum degree of ≤50Pa. Continue to heat to 900℃ at a rate of 3℃ / min, then heat to 1000℃ at a rate of 1℃ / min and keep warm for 90min. Then maintain the temperature at 1000℃ for more than 1.5m 3 / min, high-pressure argon gas is injected into the furnace until the pressure reaches 8 bar, and then the temperature and pressure are maintained for 20 minutes. After sintering, it is cooled to obtain high-density and high-performance copper radiator parts.

[0036] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a high-density powder injection molded copper heat sink, characterized in that: The following steps are involved: S1, pre-oxidizing the crude copper powder, and then uniformly mixing it with the fine copper powder and the copper alloy powder to prepare a raw material powder; wherein the particle size of the fine copper powder is smaller than that of the crude copper powder, the particle size of the crude copper powder is 325-800 mesh, and the particle size of the fine copper powder is less than or equal to 600 mesh; S2, mixing the raw material powder and the binder uniformly, and then sequentially performing injection molding and degreasing to prepare a green body; S3, sintering the green body, wherein the sintering includes sequentially sintering in a hydrogen atmosphere, vacuum sintering, and pressure sintering; cooling after the sintering is completed, thus preparing a copper radiator component.

2. The preparation method according to claim 1, characterized in that In step S1, in the raw material powder, the mass fraction of the fine copper powder is 15-45%, and the mass fraction of metals other than copper in the copper alloy powder is 0-2%.

3. The preparation method according to claim 1, characterized in that: In step S1, the pre-oxidation is performed under air atmosphere.

4. The preparation method according to claim 1, characterized in that: The coarse copper powder and the fine copper powder are atomized copper powder.

5. The preparation method according to claim 1, characterized in that: In step S1, the copper alloy includes one or a combination of two or more selected from the following group: copper-zinc alloy, copper-tin alloy, copper-chromium alloy, copper-zirconium alloy, copper-manganese alloy, and copper-manganese-nickel alloy.

6. The preparation method according to claim 1, characterized in that: In step S3, the green body is placed in a sintering furnace for sintering, and hydrogen atmosphere sintering is performed before the temperature is raised to 700°C; vacuum sintering is performed after the temperature is raised to 700°C, and the maximum temperature of the vacuum sintering is greater than or equal to the melting point of the copper alloy powder and less than or equal to 1080°C; after the vacuum sintering is completed, the temperature is maintained unchanged and pressure sintering is performed in an inert gas atmosphere.

7. The preparation method according to claim 6, characterized in that: In the vacuum sintering step, when the temperature is raised to 100° C. from the maximum temperature, the temperature is raised to the maximum temperature at a rate of 1 to 2° C. / min.

8. The preparation method according to claim 6, characterized in that: In the pressure sintering step, the pressure of the inert gas is greater than 1 bar, and the flow rate of the inert gas is greater than 1 m / s. 3 / min, the pressure and heat preservation time is 20~40min.

9. The preparation method according to claim 6, characterized in that: The inert gas includes one or a combination of two or more selected from the following group: helium, neon, and argon.