A method for preparing low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod

Abstract

The application relates to a preparation method of low-oxygen ultrapure tin ingot (rod). The process method combines the chemical and physical properties of tin, and prepares the low-oxygen ultrapure tin ingot (rod) with the purity of more than 99.999995% and the oxygen content of less than 1PPm through the following process steps: raw material and auxiliary material preparation, raw material ingot preparation, ingredient preparation and furnace loading according to the forming requirement, high-vacuum and high-temperature deoxidization and impurity removal treatment, filling at a certain temperature and vacuum degree, secondary deoxidization and impurity removal treatment in a hydrogen atmosphere, directional solidification forming, demolding and packaging and the like. The preparation method of the low-oxygen ultrapure tin ingot (rod) integrates the impurity removal, deoxidization and forming of the ultrapure tin material, can effectively reduce the oxygen content and low-boiling-point impurity content in the ultrapure tin ingot (rod), and is complete in the whole preparation method process, high in intelligent degree, simple in operation, suitable for the preparation of ultrapure tin ingot (rod) with various specifications and size requirements, and can meet the development requirement of the high-end semiconductor industry in the quality and shape of the prepared ultrapure material. Meanwhile, the preparation method is also suitable for the forming process of low-oxygen ultrapure indium, antimony, gallium and the like.

Description

TECHNICAL FIELD

[0001] The application relates to the field of high-purity material forming, in particular to a preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod. BACKGROUND

[0002] Tin is an important strategic resource, China has rich tin reserves, and the annual output of refined tin is about 150,000 tons, accounting for more than 40% of the global output. Tin is a characteristic resource of China, and high-purity tin, as a new functional material, is widely used in alloy manufacturing in aerospace, semiconductor materials in electronic information and the like, and has become a key material supporting the development of human high-tech. With the rapid development of domestic and foreign electronic industry, atomic energy industry and aviation industry, the demand for high-purity tin is increasing, and the demand for tin materials is gradually increasing.

[0003] Ultra-pure tin is widely used in the semiconductor industry and the manufacture of superconducting alloys. Ultra-pure tin is a very promising functional material, which is widely used in national defense, aerospace, electronic industry and atomic energy industry, and is mainly used for preparing compound semiconductors, high-purity alloys, superconducting materials, solders and compound semiconductor dopants and extreme ultraviolet lithography technology light sources.

[0004] At present, ultra-pure tin is a key material for electronic industry technology, especially in the use of extreme ultraviolet lithography technology light source, which has strict requirements on the purity, oxygen content and shape size of the material. In the conventional preparation process, other impurities or high oxygen content are inevitably introduced, and the prepared high-purity tin cannot meet the use requirements of the downstream.

[0005] Therefore, it is necessary to study the preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod to meet the development needs of the high-end electronic information technology industry. However, there is no related preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod in the current available data. SUMMARY

[0006] To solve the above technical problems, the application provides a preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod, which integrates ultra-pure tin material impurity removal, deoxidization and forming, can effectively reduce the oxygen content and low-boiling-point impurity content in the ultra-pure tin ingot or ultra-pure tin rod, and the whole preparation method is complete in process, high in intelligent degree, simple in operation and suitable for the preparation of ultra-pure tin ingots or ultra-pure tin rods of various specifications and sizes. The quality and shape of the prepared ultra-pure material meet the development needs of the high-end semiconductor industry.

[0007] The technical scheme adopted by the application to solve the technical problems is that a preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod is performed according to the following steps:

[0008] S1, preparing high-purity tin material, high-purity tin ingot or high-purity tin rod forming device and forming mold;

[0009] S2. High-purity tin material is cast into small ingots under a high-purity argon atmosphere for later use. The size of the ingots is 50-100g / ingot, depending on the required forming specifications, to facilitate the use of counterweight in the next step.

[0010] S3. After the cast ingots are weighted according to the required tin ingot or tin rod weight, they are placed into a conical tube filled with high-purity quartz filler and vacuumed to 10. -4 Below Pa, the heating device is started and the deoxidation and impurity removal section is heated to 950-1050℃, and then deoxidation and impurity removal are carried out under high temperature and high vacuum.

[0011] S4. After deoxidation and impurity removal, the high-purity tin liquid flows into the molding die, where it is kept at a constant temperature of 1000-1050℃ and under high vacuum for 10 minutes. -4 High-purity molten tin is filtered through packing material and filled into a mold at Pa;

[0012] S5. Stop the vacuum system and introduce high-purity hydrogen through the gas inlet pipe. The hydrogen flow rate is controlled at 0.5-1L / min. After introducing hydrogen for 30-50 minutes, deoxidation and impurity removal are carried out again at a constant temperature of 1000-1050℃ in the forming section. The constant temperature time in the hydrogen atmosphere is 120-150 minutes.

[0013] S6. After deoxidation and impurity removal in a hydrogen environment, the temperature of the forming section is reduced to 280-350℃. The directional solidification device is started to solidify uniformly from top to bottom, with the moving speed controlled at 100-150mm / h. After the forming mold is completely removed from the heating zone and the molten tin is solidified, it is cooled to room temperature. The hydrogen inlet valve is closed, and the high-purity argon inlet valve is opened for 20-30 minutes. Then, the argon gas is stopped and the pressure is released. Under an inert gas atmosphere, the forming mold is removed and demolded to obtain low-oxygen ultrapure tin ingots or low-oxygen ultrapure tin rods.

[0014] In step S1, the high-purity quartz parts and high-purity graphite (or boron nitride) molds are required. The quartz parts are soaked in aqua regia, rinsed with high-purity water, and dried. The graphite (or boron nitride) molds are soaked in aqua regia, repeatedly washed with high-purity hot water, dried, and calcined at 1000-1100℃ in a vacuum.

[0015] In step S2, the high-purity tin ingot is cast in a high-purity argon atmosphere using a mold made of graphite or boron nitride material and then set aside for later use.

[0016] In step S3, during vacuuming, the extracted gas enters the exhaust gas system and undergoes rinsing treatment.

[0017] In steps S5 and S6, the gas generated during the process enters the exhaust gas system for treatment, and the exhaust gas is discharged into the air after being filtered through multiple stages of dust removal.

[0018] In steps S2 and S6, the argon is high-purity argon with a purity of at least 99.999%, and the argon flow rate is 0.5-1 L / min; in step S5, the hydrogen is high-purity hydrogen with a purity of at least 99.999%, and the hydrogen flow rate is 0.5-1 L / min.

[0019] 1. In steps S3, S4 and S5, the heating mode of the deoxidization and impurity removal section and the forming section is medium-frequency induction heating, and the heating rate is 15-20℃ / min.

[0020] 2. The directional solidification in step S6 is only started during cooling, and the stroke of the downward movement of the directional solidification device is determined according to the height of the forming mold, and the optimal stroke is the height of the mold plus 20-25 mm, and the heating mode of S6 is resistance heating, and the cooling rate is 2-5℃ / min.

[0021] The small ingot casting mold for the high-purity tin raw material can be a cuboid ingot, which is convenient to operate.

[0022] The size of the forming mold can be changed according to the corresponding size required.

[0023] The medium-frequency induction heating mode generates a strong electromagnetic force during heating and constant temperature, and the molten tin liquid is subjected to strong stirring due to the electromagnetic force, which is beneficial to improve the deoxidization and impurity removal effect.

[0024] The temperature control of the medium-frequency induction heating is controlled by a temperature sensor, and the signal of the temperature control sensor is transmitted to the PLC centralized control interface, and only the required process parameters need to be set on the operation interface.

[0025] The moving speed and stroke parameters of the directional solidification device are set on the PLC control interface.

[0026] The advantages of the present application are as follows: the preparation method of the low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod of the present application can effectively reduce the impurity content and oxygen content in the ultra-pure tin ingot or low-oxygen ultra-pure tin rod by using the process steps of medium-frequency induction heating deoxidization and impurity removal under vacuum, high-purity quartz filler filtration deoxidization, hydrogen atmosphere and deoxidization and forming under high temperature conditions; the whole preparation method has a complete process, high intelligent degree, simple operation, and is suitable for the preparation of ultra-pure tin ingots or low-oxygen ultra-pure tin rods of various specifications and sizes, and the prepared ultra-pure materials meet the needs of the development of high-end semiconductor industry in quality and shape. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The process flow chart of the preparation method of the low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod of the present application is shown in the figure. DETAILED DESCRIPTION

[0028] In order to deepen the understanding of the present application, the present application will be further described in detail below in conjunction with the drawings.

[0029] As Figure 1 shown, the present embodiment provides a preparation method of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod, which is carried out according to the following steps:

[0030] S1, preparing high-purity tin material, high-purity tin ingot or high-purity tin rod forming device and forming mold;

[0031] S2, casting the high-purity tin material into small ingots under a high-purity argon atmosphere for standby, the size of the ingots is 50-100 g per ingot according to the required specification size for easy weight matching for the next step;

[0032] S3, loading the cast small ingots into a conical tube with high-purity quartz filler after weight matching according to the weight of the required tin ingot or tin rod, and then vacuuming to 10 -4 Pa, and then starting the heating device to heat to 950-1050℃ for deoxidization and impurity removal, and then performing deoxidization and impurity removal under high temperature and high vacuum;

[0033] S4, after the deoxidization and impurity removal, the high-purity tin liquid flows into the forming mold, and the high-purity tin liquid is filled into the mold through the filler under the constant temperature of 1000-1050℃ and high vacuum of 10 -4 Pa in the forming section;

[0034] S5, stopping the vacuum system, and introducing high-purity hydrogen gas from the gas inlet pipe, the hydrogen flow is controlled at 0.5-1 L / min, and after 30-50 min of hydrogen introduction, deoxidization and impurity removal are performed again under the constant temperature of 1000-1050℃ in the forming section, and the constant temperature time in the hydrogen atmosphere is 120-150 min;

[0035] S6, after the deoxidization and impurity removal in the hydrogen atmosphere are completed, the temperature of the forming section is reduced to 280-350℃, the directional solidification device is started to move at a constant speed from top to bottom, and the moving speed is controlled at 30-50 mm / h, and after the forming mold is completely moved out of the heating zone, the tin liquid is solidified, and then the temperature is reduced to room temperature, the hydrogen inlet valve is closed, the high-purity argon inlet valve is opened for 20-30 min, and then the argon is stopped and depressurized, and after the inert gas atmosphere, the forming mold is taken out, and then demolding is performed, and thus the low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod is obtained.

[0036] In step S1, high-purity quartz pieces, high-purity graphite (or boron nitride material) molds are needed, the quartz pieces are sequentially soaked in aqua regia, washed with high-purity water, and dried; the graphite (or boron nitride material) molds are sequentially soaked in aqua regia, repeatedly washed with high-purity hot water, dried, and calcined at a high temperature of 1000-1100°C under vacuum.

[0037] In step S2, high-purity tin ingots are cast using graphite or boron nitride material molds under a high-purity argon atmosphere.

[0038] In step S3, when vacuum is drawn, the gas is drawn into the tail gas system and subjected to a rinse treatment.

[0039] In steps S5 and S6, the gas generated in the process is introduced into the tail gas system for treatment, and the tail gas is exhausted after multi-stage dust removal and filtration.

[0040] In steps S2 and S6, the argon is high-purity argon with a purity of at least 99.999%, and the argon flow rate is 0.5-1 L / min; in step S5, the hydrogen is high-purity hydrogen with a purity of at least 99.999%, and the hydrogen flow rate is 0.5-1 L / min.

[0041] The directional solidification in step S6 is only started when the temperature is lowered, and the travel of the directional solidification device downward is determined according to the height of the forming mold, and the optimal travel is the height of the mold plus 20-25 mm.

[0042] In the method for preparing low-oxygen ultra-pure tin ingots or low-oxygen ultra-pure tin rods of the present embodiment, all control systems are controlled by PLC, including temperature rising programs, gas flow rates, mutual switching of various control valves, speed and temperature control of directional condensation, etc.

[0043] In the method for preparing low-oxygen ultra-pure tin ingots or low-oxygen ultra-pure tin rods of the present embodiment, in steps S3, S4, and S5, the heating mode of the deoxidization and impurity removal section and the hydrogen deoxidization and impurity removal section is medium-frequency induction heating, and the heating rate is 15-20°C / min; and in step S6, the heating mode is resistance heating, and the cooling rate is 3-5°C / min.

[0044] In the method for preparing low-oxygen ultra-pure tin ingots or low-oxygen ultra-pure tin rods of the present embodiment, in steps S3, S4, and S5, a three-stage deoxidization and impurity removal process is adopted, which combines high-temperature deoxidization and impurity removal under high vacuum and medium-frequency induction heating, removal of oxide films by quartz filler under high vacuum, and re-deoxidization under a hydrogen atmosphere. The deoxidization under a hydrogen atmosphere needs to control the temperature and the flow rate of hydrogen, and also has a certain effect on the impurity removal of high-purity tin products. If only one or two of the above deoxidization and impurity removal processes are used in the process, the purity and oxygen content of the ultra-pure tin will be affected.

[0045] The effects of the present application will be verified below in combination with examples and comparative examples, the relevant examples are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0046] The following examples and comparative examples all use high-purity tin with a purity of 99.99999% as raw material.

[0047] Example One

[0048] S1, the graphite casting ingot mold size required in the preparation process is 50x20x15mm, first immersed in aqua regia for 24h, then repeatedly washed with pure water heating, dried, and calcined at 10 -3 pa, temperature 1100℃ for 3h. The treated mold is used to cast ingots into 50-100g / ingot small ingots under high-purity argon atmosphere for easy subsequent weight matching.

[0049] S2, the high-purity quartz tube, quartz filler, high-purity graphite mold (8 φ25x80mm) required in the process are sequentially treated by soaking in aqua regia for 24h, washing with high-purity water, drying, and calcining at 10 -3 pa and temperature 1100℃ for 3h.

[0050] S3, the cast small ingots are weighed 8 times, each weighing 400-405g, and the weighed 8 high-purity tin materials are respectively loaded into 8 conical tubes containing high-purity quartz filler, each conical tube corresponds to a graphite mold. The treated graphite mold, quartz support tube, and quartz conical tube containing the material are sequentially loaded into the inner and outer tubes of the ingot casting device, and finally the furnace cover is sealed. Start the vacuum system to vacuum to 10 -4 Pa below, then start the heating device to deoxidize and remove impurities to 1000℃, then deoxidize and remove impurities under high temperature and high vacuum, the constant temperature time of this stage is 2h;

[0051] S4, after vacuum and intermediate frequency induction heating deoxidization and impurity removal, the high-purity tin liquid flows into the forming mold, and the high-purity tin liquid is filled into the graphite mold through the filler under the constant temperature of 1000℃ and high vacuum of 10 -4 Pa in the forming section;

[0052] S5, stop the vacuum system, according to the set program, close the valve on the vacuum system, first continuously introduce high-purity argon for 20min through the gas inlet pipe, then switch the valve to introduce high-purity hydrogen, the hydrogen flow is controlled at 0.6L / min, and the deoxidization and impurity removal process is carried out again under the constant temperature of 1000℃ and hydrogen atmosphere, the constant temperature time of this process under hydrogen atmosphere is 2h;

[0053] S6, after the deoxidation and impurity removal in the hydrogen environment, the temperature of the forming section is reduced to 280-350°C through a set control program, and the directional solidification device is started to move at a uniform speed from top to bottom, the moving distance is 80mm, and the moving speed is controlled at 30-50mm / h, and the forming mold is completely moved out of the heating zone.

[0054] S7, after the tin liquid is solidified, the temperature is reduced to room temperature, the hydrogen inlet valve is closed, the high-purity argon inlet valve is opened for 20 minutes, then the argon is stopped and the pressure is released, and the forming mold is taken out after the inert gas atmosphere, and the demolding is performed, and the low-oxygen ultra-pure tin rod is obtained, that is, the preparation of the low-oxygen ultra-pure tin rod is completed.

[0055] The tin rod prepared in Example 1 is detected for quality and oxygen content:

[0056] 1, the prepared 8 tin rods are weighed respectively, the weight is in the range of 398-403g, and each tin rod is dense without shrinkage hole, has metal luster, and no visible oxide.

[0057] 2, one of the tin rods is randomly selected for full-element impurity content detection, the purity of the tin rod reaches 99.999996%, the contents of impurity elements S, Se, Zn, Cd, Pb and Bi are obviously reduced, and the contents are all <0.005PPm, reaching the detection lower limit of the GDMS detection equipment; at the same time, the oxygen content in the tin rod is <1PPm, which can meet the use requirements of customers.

[0058] Example 2

[0059] The difference between this example and Example 1 is that in step S2, four 50x40x20mm cuboid graphite forming molds are selected; in step S3, four portions of high-purity tin 260-265g are weighed and respectively put into four quartz conical tubes filled with fillers; in step S6, the moving distance is 50mm during directional solidification. The others are the same as Example 1.

[0060] The tin ingot formed in Example 1 is tested:

[0061] 1, the prepared 4 tin ingots are weighed respectively, the weight is in the range of 258-263g, and each tin ingot is dense without shrinkage hole, has metal luster, and no visible oxide.

[0062] 2, one of the tin ingots is randomly selected for full-element impurity content detection, the purity of the tin rod reaches 99.999997%, the contents of impurity elements S, Se, Zn, Cd, Pb and Bi are obviously reduced, and the contents are all <0.005PPm, reaching the detection lower limit of the GDMS detection equipment; at the same time, the oxygen content in the tin ingot or tin rod is <1PPm, which can meet the use requirements of customers.

[0063] Comparative Example 1

[0064] In the process of Example 1, the deoxidization and impurity removal process under high vacuum and medium frequency induction heating in S3 was changed to deoxidization under high vacuum and resistance heating, and the rest of the process remained unchanged.

[0065] The tin rods prepared in the above-mentioned Comparative Example 1 process were tested:

[0066] 1. The prepared 8 tin rods were weighed, with a weight in the range of 399-404 g, and each tin rod had a dense surface without shrinkage, a metallic luster, and no visible oxide.

[0067] 2. One of the tin rods was randomly selected for full-element impurity content detection, and the purity of the tin rod was 99.99999%, which did not change much compared to the raw material input. The impurity elements S, Se, Zn, Cd, Pb, Bi, etc. did not change significantly, the impurity content changed by 1-2 PPb, and the oxygen content in the tin rod was ≤5 PPm. The impurity content and oxygen content were different compared to Example 1, and the prepared product did not achieve the expected effect.

[0068] Comparative Example 2

[0069] In the process of Example 1, the high-temperature hydrogenation impurity removal process under hydrogen atmosphere in S5 was omitted, and a direct forming process under vacuum high temperature (or inert gas protection) was used instead, and the rest of the process remained unchanged.

[0070] The tin rods prepared in the above-mentioned Comparative Example 1 process were tested:

[0071] 1. The prepared 8 tin rods were weighed, with a weight in the range of 400-403 g, and each tin rod had a dense surface without shrinkage, a metallic luster, and a small amount of gray-black visible material on the upper end surface and surface of the cylindrical ingot.

[0072] 2. One of the tin rods was randomly selected for full-element impurity content detection, and the purity of the tin rod was 99.99999%, which did not change much compared to the raw material input. The impurity elements S, Se, Zn, Cd, Pb, Bi, etc. did not change significantly, the impurity content changed by 1-2 PPb, and the oxygen content in the tin rod was ≤5 PPm. The impurity content and oxygen content were different compared to Example 1, and the prepared product did not achieve the expected effect.

[0073] One of the tin rods was randomly selected for full-element impurity content detection, and the purity of the tin rod was 99.99999%, and the impurity elements S, Se, Zn, Cd, Pb, Bi, etc. changed significantly. However, the oxygen content in the tin rod was ≤5 PPm, which was different compared to Example 1, and the prepared product did not achieve the expected effect.

[0074] Comparative Example Three

[0075] In the process of Example One, the filler in the quartz tapered tube in S3 is omitted, and the weighed raw material ingot is directly placed into the empty quartz tapered tube. After high vacuum and medium frequency induction heating for deoxidization and impurity removal, the ingot is directly flowed into the forming mold, and the rest of the process remains unchanged.

[0076] The tin rods prepared in the process of Comparative Example One are tested:

[0077] 1. The eight prepared tin rods are weighed respectively, with a weight in the range of 402-404 g, and each tin rod has a dense surface without shrinkage holes, a metallic luster, and a small amount of black substance visible to the naked eye on the upper end surface and the surface of the cylindrical ingot.

[0078] 2. One of the tin rods is randomly selected for full element impurity content detection, and the purity of the tin rod is 99.99999%+, which does not reach 99.999995% and above. The contents of impurity elements S, Se, Zn, Cd, Pb, Bi, etc. in the tin rod change significantly, but the oxygen content in the tin rod is ≤5PPm, which is different from that of Example One. The prepared product does not achieve the expected effect.

[0079] Comparative Example Four

[0080] In the process of Example One, the directional condensation forming process under constant temperature in S6 is omitted, and instead, after the completion of the S5 step, the power is directly turned off for natural cooling and solidification treatment; the rest of the process remains unchanged.

[0081] 1. The eight prepared tin rods are weighed respectively, with a weight in the range of 400-403 g, and each tin rod has a metallic luster without visible oxides, but the upper end surface of the tin rod is uneven with shrinkage holes.

[0082] 2. One of the tin ingots or tin rods is randomly selected for full element impurity content detection, and the purity of the tin rod reaches 99.999995%, and the contents of impurity elements S, Se, Zn, Cd, Pb, Bi, etc. in the tin rod are significantly reduced, all reaching the lower limit of GDMS detection equipment detection; at the same time, the oxygen content in the tin ingot or tin rod is <1PPm, and the purity and oxygen content meet the requirements, but cannot meet the use requirements for special appearance requirements.

[0083] In the above embodiment, the chemical and physical properties of tin and part of impurities in tin are combined, and the intermediate frequency induction heating deoxidization and impurity removal of high-purity tin, filtering and slagging under high temperature and high vacuum for secondary deoxidization, deoxidization and impurity removal under hydrogen atmosphere and high temperature, and directional condensation forming treatment are combined, forming a complete low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod preparation process. The preparation process is simple, easy to operate, high in intelligent control degree, strong in preparation operation flexibility, obvious in purification effect of part of impurities in high-purity tin, and can prepare low-oxygen ultra-pure tin with different specifications and size requirements, so that the oxygen content is less than 1PPm. It can meet the special requirements of the development of high-end semiconductor material industry. At the same time, the preparation method is also suitable for low-oxygen ultra-pure indium, antimony, gallium and other material forming process.

[0084] In the above embodiment, the intermediate frequency induction heating method is adopted, which can generate strong electromagnetic force in the process of heating and constant temperature. The melted tin liquid is subjected to strong stirring under the action of electromagnetic force, which can achieve two effects, which is beneficial to the deoxidization of high-purity tin and the reduction of S, Se, As, Zn, Cd, Pb and Bi impurities in high-purity tin.

[0085] In the above embodiment, no reagent is added in the whole forming process of the ultra-pure tin ingot or ultra-pure tin rod, and high-purity argon gas and high-purity hydrogen gas are used, and the demolding and packaging process in the later stage are carried out in argon atmosphere, which further ensures that the purity of the prepared ultra-pure tin rod can reach 99.999995% or above.

[0086] The above embodiment should not limit the present application in any way, and any technical solution obtained by equivalent replacement or equivalent conversion falls within the protection scope of the present application.

Claims

1. A process for the production of low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod, characterized by: The preparation method is carried out according to the following steps: S1, preparing high-purity tin material, high-purity tin ingot or high-purity tin rod forming device and forming mold; S2, the high-purity tin material is cast into small ingots under high-purity argon atmosphere for standby, the size of the ingot is 50-100g / ingot according to the required size of the formed specification, facilitating the next step of weight matching; S3, the cast ingot is loaded into a conical tube with high purity quartz filler according to the weight of the shaped tin ingot or shaped tin rod, and vacuumed to 10 -4 Pa, and then the heating device is started. After the temperature is raised to 950-1050°C in the deoxidization and impurity removal section, the heating rate is 15-20°C / min. The deoxidization and impurity removal treatment is carried out at high temperature and high vacuum. S4, after the deoxidation and impurity removal, the high purity tin liquid flows into the forming mold, and the constant temperature is 1000-1050℃ and the high vacuum is 10 -4 The high purity tin liquid is filled into the mold through the filler filtration under the pressure of Pa. S5, stop the vacuum system, close all valves on the vacuum system, introduce high-purity hydrogen into the gas inlet pipe, control the hydrogen flow at 0.5-1L / min, after 30-50min of hydrogen introduction, carry out deoxidization and impurity removal treatment again at a constant temperature of 1000-1050℃ in the forming section, the constant temperature time in the hydrogen atmosphere is 120-150min; S6, after the deoxidization and impurity removal in the hydrogen environment is completed, the temperature of the forming section is reduced to 280-350℃, the directional solidification device is started, and the forming mold is uniformly directionally solidified from top to bottom at a moving speed controlled at 30-50mm / h, after the forming mold is completely moved out of the heating zone, the tin liquid is solidified, and then cooled to room temperature, the hydrogen inlet valve is closed, the high-purity argon inlet valve is opened for 20-30min, then the argon is stopped and depressurized, after the forming mold is taken out in the inert gas atmosphere, demolding is carried out, and low-oxygen ultra-pure tin ingots or low-oxygen ultra-pure tin rods are obtained, In steps S3, S4 and S5, a process combining high vacuum degree, medium-frequency induction heating, high-temperature impurity removal and deoxidization, quartz filler filtering to remove oxide film and high-temperature deoxidization in hydrogen atmosphere is used for three-stage deoxidization and impurity removal treatment.

2. The method for preparing low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod according to claim 1, characterized in that: In step S1, high-purity quartz parts, high-purity graphite or boron nitride material molds are used, the quartz parts are sequentially soaked in aqua regia, washed with high-purity water and dried; the graphite or boron nitride material molds are sequentially soaked in aqua regia, repeatedly washed with high-purity hot water, dried and vacuum calcined at 1000-1100℃.

3. The method of claim 1, wherein the low-oxygen ultra-pure tin ingot or rod is prepared by the steps of: In step S2, the high-purity tin material ingot is cast in a graphite or boron nitride material mold under high-purity argon atmosphere for standby. ​ 4. The method of claim 1, wherein the low-oxygen ultra-pure tin ingot or rod is prepared by the steps of: In steps S5 and S6, the gas generated in the process is introduced into the tail gas system for treatment. ​ 5. The method for preparing low-oxygen ultra-pure tin ingot or low-oxygen ultra-pure tin rod according to any one of claims 1-4, characterized in that: In steps S2 and S6, the argon is high-purity argon with a purity of at least 99.999%, and the argon flow is 0.5-1L / min; in step S5, the hydrogen is high-purity hydrogen with a purity of at least 99.999%, and the hydrogen flow is 0.5-1L / min.

6. The method of claim 1, wherein the low-oxygen ultrapure tin ingot or rod is prepared by the steps of: In step S6, the directional solidification is only started during cooling, and the travel of the directional solidification device downward is determined according to the height of the forming mold, and the optimal travel is the mold height plus 20-25mm. ​ 7. The method of claim 2, wherein the low-oxygen ultra-pure tin ingot or rod is prepared by the steps of: The small ingot casting mold used for high-purity tin preparation is a cuboid ingot, which is convenient to operate. ​ 8. The method of claim 3, wherein the low-oxygen ultra-pure tin ingot or rod is prepared by the steps of: The size of the forming mold is replaced according to the required corresponding size. ​ 9. The method of claim 1, wherein the low-oxygen ultrapure tin ingot or rod is prepared by the steps of: The medium-frequency induction heating method generates strong electromagnetic force during heating and constant temperature, and the melted tin liquid is strongly stirred under the action of electromagnetic force, which is beneficial to improve the deoxidization and impurity removal effect. ​ 10. The method of claim 1, wherein the low-oxygen ultrapure tin ingot or rod is prepared by the steps of: The temperature control of the medium frequency induction heating is controlled by a temperature sensor, and the signal of the temperature sensor is transmitted to a PLC centralized control interface, and only the required process parameters need to be set on the operation interface. ​ 11. The method of claim 6, wherein the low-oxygen ultrapure tin ingot or rod is prepared by the steps of: The moving speed and stroke parameters of the directional solidification device are set on the PLC control interface. ​

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