A method for reducing carbon particles in copper ingots

Abstract

This invention provides a method for reducing carbon particles in copper ingots. The method includes the following steps: before smelting the copper ingot in a graphite crucible, pre-treating the surface of the graphite crucible with copper material. The method provided by this invention, by treating the copper ingot smelting equipment, solves the problem of carbon particle incorporation in copper ingots at its source. In stable production, the carbon particle content can be stably controlled below 260 particles / gram, and especially as low as 20 particles / gram. When the produced copper ingot is used as a wiring material for chips, the performance of the chip thin film is significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of metal casting technology and relates to a method for reducing carbon particles in copper ingots. Background Technology

[0002] Ultra-high purity (6N, ≥99.9999%) copper and copper alloys (copper-aluminum alloys, copper-manganese alloys) are wiring materials for integrated circuit chips. With the development of integrated circuit chips, the requirements for the quality of wiring materials are getting higher and higher, and carbon particles in copper and copper alloy ingots directly affect the quality of chip coating.

[0003] CN103938002A, CN105970009A, and other publications disclose smelting processes for copper and its alloys. In existing processes, ultra-high purity copper and copper alloy ingots are generally produced by smelting. Metallic copper or copper alloy raw materials are melted in a high-purity graphite crucible and then cast into a mold. During the production process, graphite particles attached to the high-purity graphite crucible can be mixed into the ingot, resulting in excessive carbon particle content in the ingot and thus affecting the quality of the ingot.

[0004] CN116607027A discloses a method for reducing particulate matter in high-purity copper alloy ingots. The specific process includes mixing and melting electrolytic copper and copper oxide, conducting a displacement reaction, adding metal raw materials for refining, and finally casting. This method optimizes the ingot smelting process, removing some carbon particles from the ingot, reducing the particulate matter content, and improving ingot quality. However, in actual production, the carbon particles in the ingot mainly originate from the graphite crucible. This method does not solve the problem of carbon particle incorporation at the source; optimizing the process from a technological perspective may actually make the steps more cumbersome and affect production efficiency.

[0005] Therefore, to address the shortcomings of existing technologies, there is a need to provide a method for reducing carbon particles in copper ingots. Summary of the Invention

[0006] The purpose of this invention is to provide a method for reducing carbon particles in copper ingots. This method solves the problem of carbon particle incorporation in copper ingots at the source, and the resulting ingots can improve the coating quality when used as target materials.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] This invention provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0009] Before smelting copper ingots in a graphite crucible, the surface of the graphite crucible is pretreated with copper material.

[0010] The method provided by this invention treats the graphite crucible used in smelting from the source of carbon particles appearing in the ingot, thereby reducing the amount of carbon particles entering the copper ingot and avoiding tedious optimization and control of smelting process parameters.

[0011] Preferably, the pretreatment includes furnace washing and furnace conditioning performed sequentially.

[0012] Preferably, the furnace cleaning method includes cleaning the surface of the graphite crucible and then melting the copper material in the graphite crucible.

[0013] The graphite crucible has a large number of tiny carbon particles adhering to its surface. During the production process, these particles enter the copper ingot along with the molten copper, causing the particulate matter content to exceed the standard. Before smelting, the graphite crucible is cleaned to remove the carbon particles adhering to its surface and carry them out with the molten copper.

[0014] The vacuum degree during furnace cleaning is <0.01Pa, for example, it can be 0.001Pa, 0.003Pa, 0.005Pa, 0.007Pa or 0.009Pa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0015] Preferably, the number of times the furnace is washed is ≥5 times, for example, 5 times, 6 times, 7 times, 8 times, 9 times or 10 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0016] Preferably, during the furnace cleaning process, the surface cleaning process includes removing copper deposits from the inner wall of the crucible.

[0017] Preferably, the furnace conditioning method includes melting copper material in a graphite crucible.

[0018] The process of maintaining the furnace does not involve cleaning the surface of the graphite crucible. During the melting of copper, a layer of copper volatiles will be deposited on the surface of the graphite crucible, forming a protective layer. This layer helps to prevent carbon particles in the graphite crucible from migrating and falling into the molten copper, thereby reducing the number of carbon particles.

[0019] The vacuum degree during furnace curing is <0.01Pa, for example, it can be 0.001Pa, 0.003Pa, 0.005Pa, 0.007Pa or 0.009Pa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the furnace is maintained for ≥5 times, for example, 5 times, 6 times, 7 times, 8 times, 9 times or 10 times, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, the method further includes: after the melting, cleaning the surface of the crucible and performing a second furnace conditioning.

[0022] After smelting, a thick layer of deposits tends to form on the surface of the graphite crucible. These deposits are easily detached and fall into the molten copper. After removing the deposits, a furnace maintenance process is then carried out to allow a new copper volatile coating to form on the surface of the graphite crucible.

[0023] Preferably, the melting process is performed 9-12 times, for example, 9, 10, 11 or 12 times.

[0024] Preferably, the second furnace conditioning process is performed at least once, for example, once, twice, three times, four times, or five times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the purity of the copper material is ≥6N.

[0026] Preferably, the copper ingot comprises ultra-high purity copper and / or copper alloys.

[0027] As a preferred embodiment of the method provided by the present invention, the method includes the following steps:

[0028] The graphite crucible is cleaned with copper material. The cleaning process involves cleaning the surface of the graphite crucible, then melting the copper material in the graphite crucible. The cleaning is repeated ≥5 times, with a vacuum degree <0.01 Pa during the cleaning. The graphite crucible is then maintained with copper material. Each maintenance process involves melting the copper material in the graphite crucible. The maintenance is repeated ≥5 times, with a vacuum degree <0.01 Pa during the maintenance. Finally, copper ingots are smelted in the graphite crucible. After every 9-12 smelting cycles, the crucible surface is cleaned, and the maintenance is repeated ≥1 time.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] The method provided by this invention addresses the issue of carbon particle incorporation in copper ingots at its source by processing the copper ingot smelting equipment. In stable production, the carbon particle content can be stably controlled below 260 particles / gram, and in particular, as low as 20 particles / gram. When the produced copper ingots are used as wiring materials for chips, the performance of the chip thin film is significantly improved. Detailed Implementation

[0031] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0032] Example 1

[0033] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0034] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The furnace cleaning process is repeated 5 times. After the furnace cleaning is completed, the graphite crucible is not cleaned, and then the furnace is cured. The curing process includes laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The curing process is repeated 5 times. During the furnace cleaning and curing processes, the vacuum degree is controlled to be below 0.01 Pa. After the curing is completed, copper ingots are smelted. After 10 heats, the above curing process is repeated once more.

[0035] Example 2

[0036] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0037] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The furnace cleaning process is repeated 8 times. After the furnace cleaning is completed, the graphite crucible is not cleaned. Instead, the furnace is cured. The curing process includes laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The curing process is repeated 8 times. During the furnace cleaning and curing processes, the vacuum degree is controlled to be below 0.01 Pa. After the curing process is completed, copper ingots are smelted. After 12 heats, the above curing process is repeated 2 more times.

[0038] Example 3

[0039] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0040] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The furnace cleaning process is repeated 5 times. During the furnace cleaning process, the vacuum degree is controlled to be below 0.01 Pa. After the furnace cleaning is completed, copper ingots are smelted in the graphite crucible. After 10 smeltings, the above-mentioned furnace conditioning process is repeated once more.

[0041] Example 4

[0042] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0043] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is not cleaned, but the furnace is then "cured". The curing process includes laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The curing process is repeated 5 times. During the curing process, the vacuum degree is controlled to be below 0.01 Pa. After the curing is completed, copper ingots are smelted. After 10 smeltings, the above curing process is repeated once more.

[0044] Example 5

[0045] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0046] After replacing the graphite crucible in the vacuum melting furnace, the furnace is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting it. The molten copper material is then poured into a mold. This process is repeated 5 times. After the furnace cleaning is completed, the graphite crucible is not cleaned. Instead, the furnace is then cured. The curing process involves laying copper material in the graphite crucible and melting it. The molten copper material is then poured into a mold. This process is repeated 5 times. During the furnace cleaning and curing processes, the vacuum degree is controlled to be below 0.01 Pa. After the curing is completed, the copper ingots are smelted.

[0047] Example 6

[0048] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0049] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The furnace cleaning process is repeated 5 times. After the furnace cleaning is completed, the graphite crucible is not cleaned, and then the furnace is cured. The curing process includes laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The curing process is repeated 5 times. During the furnace cleaning and curing processes, the vacuum degree is controlled to be below 0.01 Pa. After the curing is completed, the copper ingots are smelted. After 15 heats, the above curing process is repeated once more.

[0050] Example 7

[0051] This embodiment provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0052] After replacing the graphite crucible in the vacuum melting furnace, the graphite crucible is first cleaned. The cleaning process includes cleaning the surface of the graphite crucible, then laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The furnace cleaning process is repeated 5 times. After the furnace cleaning is completed, the graphite crucible is not cleaned. Instead, the furnace is cured. The curing process includes laying copper material in the graphite crucible and melting the copper material. The molten copper material is then poured into a mold. The curing process is repeated 5 times. During the furnace cleaning and curing processes, the vacuum degree is not controlled to be below 0.01 Pa. After the furnace curing is completed, the copper ingots are smelted.

[0053] This embodiment provides a method for reducing carbon particles in copper ingots. Compared with Embodiment 1, the furnace cleaning and curing processes are carried out in an atmospheric atmosphere, while the rest are the same as in Embodiment 1.

[0054] Comparative Example 1

[0055] This comparative example provides a method for reducing carbon particles in copper ingots, the method comprising the following steps:

[0056] The surface of the graphite crucible is cleaned, and then copper ingots are smelted in the graphite crucible. The surface of the graphite crucible is cleaned before each smelting.

[0057] In the embodiments and comparative examples of the present invention, after 50 heats of melting in a graphite crucible, the number of carbon particles in the copper ingots produced in each heat was determined by a particle analyzer and the average value was calculated. The results are listed in Table 1.

[0058] Table 1

[0059] Average number of carbon particles (particles / gram) Example 1 30 Example 2 20 Example 3 180 Example 4 260 Example 5 160 Example 6 120 Example 7 360 Comparative Example 1 320

[0060] As can be seen from Table 1:

[0061] Using the methods provided in Examples 1 and 2, the number of carbon particles in the smelted copper ingot can be controlled to below 30 particles / g, resulting in extremely low carbon particle content and high ingot quality. Compared to Example 1, reducing furnace cleaning or curing allows more carbon particles to enter the molten copper from the crucible surface, significantly increasing the number of carbon particles in the smelted ingot. In Comparative Example 1, without furnace cleaning and curing, the average number of carbon particles in the smelted ingot reaches as high as 320 particles / g, which is 10 times higher than the carbon particle content in Example 1.

[0062] In summary, the method provided by this invention, by processing the copper ingot smelting equipment, solves the problem of carbon particle incorporation in copper ingots at the source. In stable production, the carbon particle content can be stably controlled below 260 particles / gram, especially as low as 20 particles / gram. When the produced copper ingots are used as wiring materials for chips, the performance of the chip thin film is significantly improved.

[0063] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method of reducing carbon particles in a copper ingot, characterized by, The method includes the following steps: The graphite crucible is cleaned with copper material. The cleaning process involves cleaning the surface of the graphite crucible, melting the copper material in the graphite crucible, and then casting the molten copper material into a mold. The number of cleaning cycles is ≥5, and the vacuum degree during cleaning is <0.01 Pa. Then, the graphite crucible is cured with copper material. The surface of the graphite crucible is not cleaned during each curing process. Each curing process involves melting the copper material in the graphite crucible, casting the molten copper material into a mold, and curing the furnace ≥5 times. The vacuum degree during curing is <0.01 Pa. Then, copper ingots are smelted in the graphite crucible. After every 9-12 smelting cycles, the surface of the graphite crucible is cleaned, and the furnace is cured again. The number of curing cycles is ≥1.

2. The method of claim 1, wherein, During the furnace cleaning process, the surface cleaning process includes removing copper deposits from the inner wall of the crucible.

3. The method of claim 1, wherein, The purity of the copper material is ≥6N.

4. The method of claim 1, wherein, The copper ingots comprise ultra-high purity copper and / or copper alloys.