Method for reducing high-purity copper liquid oxide and preparation method of copper cast ingot

Abstract

The invention provides a method for reducing oxides in ultrahigh-purity molten copper and a preparation method of a copper ingot, and the method comprises the following steps: melting an ultrahigh-purity electrolytic copper sheet to obtain molten copper, carrying out first standing, removing floating oxides on the surface of the molten copper, heating the molten copper to a first temperature, carrying out second standing, and cooling to a second temperature, floating oxides on the surface of the molten copper are removed, and the ultrahigh-purity molten copper is obtained. According to the method provided by the invention, according to the melting characteristic of the copper oxide in the copper liquid, the temperature change of the copper liquid is regulated and controlled, so that the oxide forms a solid floating on the surface of the copper liquid to be removed, the method is simple and efficient, an impurity removal reagent does not need to be added, the content of the oxide in the copper liquid is controlled to be below 300 particles per gram, and the removal rate of the oxide is 70% or above, especially 97%.

Description

Technical Field

[0001] The invention belongs to the technical field of metal casting, and relates to a method for preparing a copper ingot, in particular to a method for reducing oxides in high-purity copper liquid and a method for preparing a copper ingot. Background Art

[0002] With the development of large-scale integrated circuits, semiconductor chips have also developed rapidly, and higher requirements have been placed on the materials needed for them. Ultra-high purity 6N (99.9999%) copper and copper alloys (copper aluminum, copper manganese, etc.) are the wiring materials of integrated circuit chips. The purity and quality of their materials directly affect the process performance of semiconductor chips. It is an important process for integrated circuit metallization to prepare sputtering targets using ultra-high purity copper or copper alloy ingots and then use physical vapor deposition methods to prepare thin films. The oxide inclusions in ultra-high purity copper or copper alloy ingots directly affect the quality of sputtering targets and chip coatings.

[0003] Ultra-high purity copper or copper alloy ingots are generally produced in a vacuum melting furnace. Ultra-high purity electrolytic copper and alloy raw materials are melted in a high purity graphite crucible and then cast into a mold. Due to oxidation, there are usually some copper oxides on the surface of ultra-high purity electrolytic copper, including CuO and Cu2O. In the process of melting ultra-high purity electrolytic copper to produce ingots, the copper oxides melt and enter the copper liquid, and then enter the casting mold with the copper liquid to cool and solidify together, producing oxide inclusions in the ingot, affecting the purity of the ingot, and then affecting the sputtering target and coating quality.

[0004] Therefore, how to effectively remove oxides from copper liquid and copper ingots to improve the purity of ultra-high purity copper liquid is a key issue.

[0005] For example, CN117000985A discloses an internal inclusion removal device and preparation method of an ultra-high purity copper or copper alloy ingot. By designing an inclusion removal device with a baffle, a slag plate and a slag step structure, the removal device is installed above the mold. During casting, the molten metal is poured into the buffer zone, and the molten metal and the slag plate are connected to form a molten metal surface layer. The impurities on the surface of the molten metal are blocked and inhibited from flowing out, reducing the inclusions and particulate matter on the surface of the copper liquid. However, this method is only applicable to impurity particles floating on the surface of the molten metal during casting, and cannot play a blocking role for oxides that are easily melted and enter the copper liquid, making it difficult to solve the problem of oxide inclusions. CN118064737A discloses a preparation method for a copper product ingot, wherein the raw material is melted under vacuum and kept warm and allowed to stand, and then a power reduction operation is performed for solidification. In the resulting ingot, inclusions are concentrated on the top of the ingot and removed after cutting. The copper raw material loss produced by this method is large and the cost is high.

[0006] Therefore, in the prior art, there is a lack of a method for effectively removing oxide inclusions in copper liquid. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for reducing oxides in high-purity copper liquid and a method for preparing copper ingots, so as to effectively reduce oxide inclusions in copper liquid and improve the purity of copper liquid and copper ingots.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for reducing ultra-high purity copper liquid oxides, the method comprising the following steps:

[0010] The ultra-high purity electrolytic copper sheet is melted to obtain copper liquid, and the copper liquid is allowed to stand for a first time to remove oxides floating on the surface of the copper liquid. The copper liquid is then heated to a first temperature, allowed to stand for a second time, and then cooled to a second temperature to remove oxides floating on the surface of the copper liquid to obtain ultra-high purity copper liquid.

[0011] The method provided by the present invention first melts the electrolytic copper sheet to form a copper liquid, and the copper oxide on the surface does not melt. After standing, the oxide floats on the surface of the copper liquid in the form of a solid, removes part of the oxide, and then heats the copper liquid and stands, melts the oxide that has not been removed, and then cools the copper liquid, and the oxide that has not been removed in the previous step re-aggregates and solidifies, and the particles grow to form a solid floating on the surface of the copper liquid, and then the residual oxide is further removed to obtain a high-purity copper liquid. The method provided by the present invention is based on the melting characteristics of CuO and Cu2O in the copper liquid, and the copper oxide is removed by regulating the temperature change of the copper liquid to form a solid floating on the surface of the copper liquid. The method is simple and efficient, and does not require the addition of any impurity removal agent.

[0012] The ultra-high purity has a purity of ≥99.9999%.

[0013] Preferably, the melting temperature is 1100-1120°C, for example, it can be 1100°C, 1102°C, 1105°C, 1108°C, 1110°C, 1112°C, 1115°C, 1118°C or 1120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0014] Preferably, the first standing time is 10-20 min, for example, 10 min, 12 min, 15 min, 18 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0015] Preferably, the first temperature is 1230-1300°C, for example, it can be 1230°C, 1235°C, 1240°C, 1245°C, 1250°C, 1255°C, 1260°C, 1265°C, 1270°C, 1275°C, 1280°C, 1285°C, 1290°C, 1295°C or 1300°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0016] Preferably, the second standing time is 10-20 min, for example, 10 min, 12 min, 15 min, 18 min or 20 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0017] Preferably, the second temperature is 1100-1120°C, for example, it can be 1100°C, 1102°C, 1105°C, 1108°C, 1110°C, 1112°C, 1115°C, 1118°C or 1120°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0018] In the present invention, the copper liquid is first heated to 1230-1300° C. and then cooled to 1100-1120° C., so that the oxide particles not removed in the previous step can be re-melted, and then re-aggregated and solidified in the cooling process, and float on the surface of the copper liquid. In particular, oxide particles with small initial particles are difficult to remove in one step, and aggregate to form larger particles in the repeated heating and cooling process, so that the molten oxide residues in the copper liquid are precipitated to obtain high-purity copper liquid.

[0019] Preferably, the method for removing oxides floating on the surface of molten copper comprises: tilting the smelting container to pour the oxides floating on the surface into a collection container.

[0020] Preferably, the method further comprises: repeatedly heating the copper liquid to the first temperature, cooling it to the second temperature after a second standing, and removing oxides floating on the surface of the copper liquid, and repeating this at least twice.

[0021] Preferably, the method is carried out at a vacuum degree below 0.01 Pa.

[0022] In a second aspect, the present invention provides a method for preparing an ultra-high purity copper ingot, the preparation method comprising the following steps:

[0023] (1) removing oxides from the ultra-high purity electrolytic copper sheet by the method described in the first aspect to obtain an ultra-high purity copper solution;

[0024] (2) heating the ultra-high purity copper liquid, allowing it to stand, and casting to obtain an ultra-high purity copper ingot;

[0025] Alternatively, the ultra-high purity copper liquid is heated, and then high purity metal is added, the mixture is allowed to stand, and then cast to obtain an ultra-high purity copper alloy ingot.

[0026] The preparation method provided by the present invention melts the electrolytic copper sheet and then removes the copper oxide in the copper liquid state to obtain high-purity copper liquid for casting, thereby effectively reducing the oxide inclusions in the ingot and improving the purity of the ingot.

[0027] Preferably, the terminal temperature of the heating is 1200-1300°C, for example, it can be 1200°C, 1210°C, 1220°C, 1230°C, 1240°C, 1250°C, 1260°C, 1270°C, 1280°C, 1290°C or 1300°C, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0028] Preferably, the standing time is 100-150 min, for example, 100 min, 110 min, 120 min, 130 min, 140 min or 150 min, but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] As a preferred technical solution of the preparation method provided by the present invention, the preparation method comprises the following steps:

[0030] (1) placing an ultra-high purity electrolytic copper sheet in a crucible, evacuating the vacuum to below 0.01 Pa, heating to 1100-1120° C. for melting, standing for 10-20 min to allow the oxides in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxides on the surface of the copper liquid into a collection container;

[0031] (2) then heating the copper liquid to 1230-1300° C., standing for 10-20 min, and then cooling the copper liquid to 1100-1120° C., so that the oxide in the copper liquid floats on the surface of the copper liquid, tilting the crucible, and pouring the oxide on the surface of the copper liquid into a collection container. This step is performed at least 3 times to obtain ultra-high purity copper liquid;

[0032] (3) heating the ultra-high purity copper liquid to 1200-1300° C., standing for 100-150 min, and casting the copper liquid in a mold to obtain an ultra-high purity copper ingot;

[0033] Alternatively, the high-purity copper liquid is heated to 1200-1300° C., high-purity metal is added, and the mixture is allowed to stand for 100-150 minutes; and then cast in a mold to obtain an ultra-high-purity copper alloy ingot.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] The method provided by the present invention is based on the melting characteristics of copper oxides in copper liquid. By adjusting the temperature change of the copper liquid, the oxides are formed into solids and float on the surface of the copper liquid for removal. The method is simple and efficient, and no impurity removal reagent needs to be added. The oxide content in the copper liquid is controlled to be below 300 particles / gram, especially below 30 particles / gram, and the oxide removal rate is above 70%, especially above 97%. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0037] Example 1

[0038] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid, the method comprising the following steps:

[0039] (1) placing an ultra-high purity electrolytic copper sheet in a high purity graphite crucible of a vacuum melting furnace, evacuating the vacuum to 0.01 Pa, heating to 1100° C., melting the electrolytic copper sheet to obtain a copper liquid, standing for 15 minutes to allow oxide residues in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxides floating on the surface of the copper liquid into a mold for collecting oxides;

[0040] (2) raising the temperature of the copper liquid to 1300° C., standing for 15 minutes, then reducing the power of the smelting furnace to reduce the temperature of the copper liquid to 1100° C., allowing the oxide residue in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxide floating on the surface of the copper liquid into a mold for collecting the oxide;

[0041] (3) Repeat step (2) twice to obtain ultra-high purity copper liquid.

[0042] This embodiment also provides a method for preparing an ultra-high purity copper ingot, the preparation method comprising the following steps:

[0043] The ultra-high purity copper liquid obtained by the above method is heated to 1250° C. and allowed to stand for 120 minutes. The mold tray is rotated to the ingot casting mold position, the crucible is tilted, and the copper liquid is cast into the ingot casting mold to obtain an ultra-high purity copper ingot.

[0044] Example 2

[0045] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid, the method comprising the following steps:

[0046] (1) placing an ultra-high purity electrolytic copper sheet in a high purity graphite crucible of a vacuum melting furnace, evacuating the vacuum to 0.01 Pa, heating to 1110° C., melting the electrolytic copper sheet to obtain a copper liquid, standing for 20 minutes to allow oxide residues in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxides floating on the surface of the copper liquid into a mold for collecting oxides;

[0047] (2) raising the temperature of the copper liquid to 1260° C., standing for 10 minutes, then reducing the power of the smelting furnace to reduce the temperature of the copper liquid to 1110° C., allowing the oxide residue in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxide floating on the surface of the copper liquid into a mold for collecting the oxide;

[0048] (3) Repeat step (2) twice to obtain ultra-high purity copper liquid.

[0049] This embodiment also provides a method for preparing an ultra-high purity copper ingot, the preparation method comprising the following steps:

[0050] The ultra-high purity copper liquid obtained by the above method is heated to 1200° C. and allowed to stand for 150 minutes. The mold tray is rotated to the ingot casting mold position, the crucible is tilted, and the copper liquid is cast into the ingot casting mold to obtain an ultra-high purity copper ingot.

[0051] Example 3

[0052] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid, the method comprising the following steps:

[0053] (1) placing an ultra-high purity electrolytic copper sheet in a high purity graphite crucible of a vacuum melting furnace, evacuating the vacuum to 0.01 Pa, heating to 1120° C., melting the electrolytic copper sheet to obtain a copper liquid, standing for 10 minutes to allow oxide residues in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxides floating on the surface of the copper liquid into a mold for collecting oxides;

[0054] (2) raising the temperature of the copper liquid to 1230° C., leaving it to stand for 20 minutes, then reducing the power of the smelting furnace to reduce the temperature of the copper liquid to 1120° C., allowing the oxide residue in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxide floating on the surface of the copper liquid into a mold for collecting the oxide;

[0055] (3) Repeat step (2) twice to obtain ultra-high purity copper liquid.

[0056] This embodiment also provides a method for preparing an ultra-high purity copper ingot, the preparation method comprising the following steps:

[0057] The ultra-high purity copper liquid obtained by the above method is heated to 1300°C, high purity aluminum is added, and the mixture is allowed to stand for 150 minutes. The mold tray is rotated to the ingot casting mold position, the crucible is tilted, and the copper liquid is cast into the ingot casting mold to obtain an ultra-high purity copper-aluminum ingot.

[0058] Example 4

[0059] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, in step (1), the electrolytic copper sheet is heated to 1130° C. for melting, and the rest is the same as Example 1.

[0060] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0061] Example 5

[0062] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, the temperature of the copper liquid is increased to 1220° C. in step (2), and the rest is the same as Example 1.

[0063] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0064] Example 6

[0065] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, the temperature of the copper liquid is increased to 1350° C. in step (2), and the rest is the same as Example 1.

[0066] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0067] Example 7

[0068] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, the temperature of the copper liquid is cooled to 1130° C. in step (2), and the rest is the same as Example 1.

[0069] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0070] Example 8

[0071] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, the temperature of the copper liquid is cooled to 1090° C. in step (2), and the rest is the same as Example 1.

[0072] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0073] Example 9

[0074] This embodiment provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, step (3) is not repeated, and the rest is the same as Example 1.

[0075] This embodiment also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Embodiment 1.

[0076] Comparative Example 1

[0077] This comparative example provides a method for preparing an ultra-high purity copper ingot, the preparation method comprising the following steps:

[0078] The ultra-high purity electrolytic copper sheet is heated to 1250°C, left to stand for 120 minutes, the mold tray is rotated to the ingot casting mold position, the crucible is tilted, and the copper liquid is cast into the ingot casting mold to obtain an ultra-high purity copper ingot.

[0079] That is, the preparation method, compared with Example 1, does not perform the oxide reduction operation, and the rest is the same as Example 1.

[0080] Comparative Example 2

[0081] This comparative example provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, step (2) and step (3) are not performed, and the rest are the same as Example 1.

[0082] This comparative example also provides a method for preparing an ultra-high purity copper ingot. Compared with Example 1, the copper liquid obtained by the above method is the same as Example 1 in other aspects.

[0083] Comparative Example 3

[0084] This comparative example provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, no standing is performed in step (2), and the rest is the same as Example 1.

[0085] This comparative example also provides a method for preparing an ultra-high purity copper ingot, using the ultra-high purity copper liquid obtained by the above method, and the rest is the same as that of Example 1.

[0086] Comparative Example 4

[0087] This comparative example provides a method for reducing oxides in ultra-high purity copper liquid. Compared with Example 1, step (1) is not performed, and the rest is the same as Example 1, that is, the ultra-high purity electrolytic copper sheet is directly used in step (2).

[0088] The oxide contents of the ingots obtained in the examples and comparative examples were measured, and the results are listed in Table 1.

[0089] Table 1

[0090]

[0091] “ / ” in the table means no data.

[0092] As can be seen from Table 1, the method for removing oxides provided by the present invention controls the temperature of the copper liquid to form solids that float on the surface of the copper liquid for removal, and controls the content of oxide particles in the copper liquid to be less than 300 particles / gram, especially less than 30 particles / gram. The oxide removal rate is high, the prepared copper ingot has high purity, and no impurity removal agent needs to be added. The method is simple and efficient.

[0093] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is 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 in the protection scope of the present invention.

Claims

1. A method for reducing oxides in ultra-high purity copper liquid, characterized in that: The method comprises the following steps: The ultra-high purity electrolytic copper sheet is melted to obtain copper liquid, and the copper liquid is allowed to stand for a first time to remove oxides floating on the surface of the copper liquid. The copper liquid is then heated to a first temperature, allowed to stand for a second time, and then cooled to a second temperature to remove oxides floating on the surface of the copper liquid to obtain ultra-high purity copper liquid.

2. The method according to claim 1, characterized in that The melting temperature is 1100-1120°C.

3. The method according to claim 1 or 2, characterized in that: The first standing time is 10-20 minutes.

4. The method according to any one of claims 1 to 3, characterized in that: The first temperature is 1230-1300°C.

5. The method according to any one of claims 1 to 4, characterized in that: The second standing time is 10-20 minutes.

6. The method according to any one of claims 1 to 5, characterized in that: The second temperature is 1100-1120°C.

7. The method according to any one of claims 1 to 6, characterized in that: The method is carried out at a vacuum degree below 0.01 Pa; Preferably, the method further comprises: repeatedly heating the copper liquid to the first temperature, cooling it to the second temperature after a second standing, and removing the floating oxides on the surface of the copper liquid, and repeating at least twice; Preferably, the method for removing oxides floating on the surface of molten copper comprises: tilting the smelting container to pour the oxides floating on the surface into a collection container.

8. A method for preparing an ultra-high purity copper ingot, characterized in that: The preparation method comprises the following steps: (1) removing oxides from an ultra-high purity electrolytic copper sheet by the method described in any one of claims 1 to 7 to obtain an ultra-high purity copper solution; (2) heating the ultra-high purity copper liquid, allowing it to stand, and casting to obtain an ultra-high purity copper ingot; Alternatively, the ultra-high purity copper liquid is heated, and then high purity metal is added, the mixture is allowed to stand, and then cast to obtain an ultra-high purity copper alloy ingot.

9. The preparation method according to claim 8, characterized in that: The end point temperature of the heating is 1200-1300°C; Preferably, the standing time is 100-150 min.

10. The preparation method according to claim 8 or 9, characterized in that: The preparation method comprises the following steps: (1) placing an ultra-high purity electrolytic copper sheet in a crucible, evacuating the vacuum to below 0.01 Pa, heating to 1100-1120° C. for melting, standing for 10-20 min to allow the oxides in the copper liquid to float on the surface of the copper liquid, tilting the crucible, and pouring the oxides on the surface of the copper liquid into a collection container; (2) then heating the copper liquid to 1230-1300° C., standing for 10-20 min, and then cooling the copper liquid to 1100-1120° C., so that the oxide in the copper liquid floats on the surface of the copper liquid, tilting the crucible, and pouring the oxide on the surface of the copper liquid into a collection container. This step is performed at least 3 times to obtain ultra-high purity copper liquid; (3) heating the ultra-high purity copper liquid to 1200-1300° C., standing for 100-150 min, and casting the copper liquid in a mold to obtain an ultra-high purity copper ingot; Alternatively, the high-purity copper liquid is heated to 1200-1300° C., high-purity metal is added, and the mixture is allowed to stand for 100-150 minutes; and then cast in a mold to obtain an ultra-high-purity copper alloy ingot.

Images