Smelting method of low-gas high-purity gold

Abstract

The invention discloses a smelting method of low-gas high-purity gold, which comprises the following steps of: 1, cleaning the high-purity gold before vacuum magnetic suspension smelting; 2, under the conditions that the vacuum degree is 1 * 10 <-5 >-1 * 10 <-2 > Pa and the temperature is 1100-1500 DEG C, primary vacuum magnetic suspension smelting is carried out for 10-60 min; thirdly, after smelting in the second step is finished, low-gas high-purity gold ingots are taken out after complete cooling; according to the smelting and purifying method for the low-gas high-purity gold, low-melting-point metal impurities, high-melting-point metal impurities and gas elements in the high-purity gold can be removed through cleaning and one-time vacuum magnetic levitation smelting; in the purification process, secondary pollution of the crucible to metal is avoided, and operation is easy and convenient.

Description

Technical Field

[0001] The present invention relates to the technical field of noble metal purification methods, and in particular to a melting method for low-gas high-purity gold. Background Art

[0002] High-purity gold has many advantages such as low resistance, low electromigration, high thermal stability, oxidation resistance, and corrosion resistance. It can form an ohmic contact with semiconductors and can adhere well to the silicon substrate. Therefore, it is widely used in the metallization system of semiconductor chips, the bonding wires of chips, the internal lead materials, advanced packaging, and welding materials. In addition, high-purity gold is also used in cutting-edge technology fields such as LED lighting, photovoltaic energy, and aerospace. The application forms include gold-based alloys, gold-based evaporation materials, high-purity gold sputtering targets, etc.

[0003] The purity of gold is closely related to the solderability, semiconductor properties, and stability of materials. When the impurities exceed the standard, the resistance, electromigration, adhesion to the silicon substrate, bondability, and film-forming properties of the gold material will be damaged. For example, the current quality requirements for gold powder used in semiconductors are as follows: the total content of metal impurities is less than 10 mg·kg-1, the contents of alkali metal elements K, Na, and Li impurities are less than 0.1 mg·kg-1, and in addition, the contents of Fe, Ni, and Cr are less than 1 mg·kg-1; the total content of non-metal impurities is less than 100 mg·kg-1, and the content of a single non-metal impurity is less than 50 mg·kg-1.

[0004] High-purity gold used in the semiconductor industry also has special requirements for interstitial element impurities such as C, H, O, and N. It is required that the total content of interstitial element impurities C, H, O, and N should be less than 100 mg·kg-1, and the content of a single interstitial element impurity is less than 50 mg·kg-1.

[0005] Gold has excellent gas absorption properties, which has an important impact on the metallurgy and materials science applications of gold. Molten gold can absorb a large amount of hydrogen, and the absorption amount can reach 37 to 46 times its own volume. Gold can also absorb oxygen, and the absorption amount is about 33 to 48 times its own volume. In the metallurgical process, this property of gold will affect its purity and performance. As the temperature increases, the gas absorption capacity of gold increases. At high temperatures, gold is more likely to react with gases and absorb more gases. The increase in gas pressure will also increase the gas absorption amount of gold. In a high-pressure gas environment, gold will absorb more gases. Gas absorption will cause the volume of gold to expand, which may cause internal stress and affect its mechanical properties and processing properties. The absorption of gases may affect the electronic structure of gold, thereby affecting its electrical conductivity.

[0006] The currently commonly used method for metal degassing is vacuum induction melting. For example, Patent CN102628107A discloses a method for secondary purification of copper by vacuum induction - electron beam melting. The method is as follows: In a vacuum environment, electrolytic copper of 4N is refined by conventional vacuum induction melting and electron beam melting successively. When performing electron beam melting, the required vacuum degree is 30 - 90 Pa, and when the induction melting temperature is 1290 - 1330 °C, the refining time is maintained for 30 minutes. This method combines vacuum induction melting and electron beam melting to perform secondary purification of copper, obtaining copper with a purity of up to 99.999%, and minimizing copper loss as much as possible to improve the quality of copper. Patent CN112095030A discloses a method for integrally preparing high - purity nickel - based superalloy by vacuum induction melting - electron beam refining. The method includes the following steps: pretreatment of raw materials, charging into the furnace, vacuum induction melting, and electron beam refining to obtain the refined alloy. This method couples vacuum induction melting and electron beam refining, uses the vacuum induction method to melt the superalloy master alloy, and then uses electron beam refining to further purify the superalloy, reducing the degree of segregation, and making full use of the advantages of induction melting and electron beam refining to improve the metallurgical quality of the superalloy ingot, ultimately achieving the high - purity preparation of the alloy. In addition, vacuum induction melting usually uses crucibles, which are prone to causing secondary pollution of high - purity manganese at high temperatures. The principle of levitation melting is to generate a high - frequency magnetic field in the induction coil through high - frequency current, causing the metal sample (conductor) to generate an induced current, thereby generating a magnetic field opposite to the direction of the coil magnetic field, generating a repulsive force to suspend the metal in space, and there will be no crucible pollution during melting. Levitation melting can provide a new degassing method for low - gas high - purity gold, reducing the introduction of impurities while removing gases. Summary of the Invention

[0007] The object of the present invention is to provide a melting method for low - gas high - purity gold in view of the above - mentioned situation. This method realizes crucible - free melting, avoids secondary pollution of the metal by the crucible during the purification process, and is simple to operate and widely applicable.

[0008] The specific scheme of the present invention is as follows: A melting method for low - gas high - purity gold includes the following steps: Step 1: Before performing vacuum magnetic levitation melting, clean the high - purity gold. Step 2: Under the conditions of a vacuum degree of 1×10⁻⁵ - 1×10⁻² Pa and a temperature of 1100 - 1500 °C, perform primary vacuum magnetic levitation melting for 10 - 60 minutes. Step 3: After the melting in Step 2 is completed, take out the low - gas high - purity gold ingot after complete cooling.

[0009] Further, in the present invention, the purity of the high - purity gold is 4N - 5N.

[0010] Further, in the present invention, the cleaning agent used for cleaning the high-purity gold in step one is pure water and / or ethanol.

[0011] The present invention is a method for smelting and purifying low-gas high-purity gold. Through cleaning and one-time vacuum magnetic levitation smelting, low-melting-point metal impurities, high-melting-point metal impurities, and gas elements in the high-purity gold can be removed; secondary pollution of the metal by the crucible is avoided during the purification process, and the operation is simple. Specific embodiments

[0012] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative work belong to the protection scope of the present invention.

[0013] The present invention is a method for smelting low-gas high-purity gold, including the following steps: Step one: Before vacuum magnetic levitation smelting, clean the high-purity gold; further, in the present invention, the purity of the high-purity gold is 4N to 5N; further, the cleaning agent used for cleaning the high-purity gold in the present invention is pure water and / or ethanol; Step two: Under the conditions of a vacuum degree of 1×10-5 to 1×10-2 Pa and a temperature of 1100 to 1500 °C, perform one-time vacuum magnetic levitation smelting for 10 to 60 minutes; Step three: After the smelting in step two is completed, take out the low-gas high-purity gold ingot after complete cooling.

[0014] The present invention is a method for smelting and purifying low-gas high-purity gold. Through cleaning and one-time vacuum magnetic levitation smelting, low-melting-point metal impurities, high-melting-point metal impurities, and gas elements in the high-purity gold can be removed; secondary pollution of the metal by the crucible is avoided during the purification process, and the operation is simple.

[0015] The following specifically illustrates the solution of the present invention in combination with specific embodiments and comparative examples.

[0016] Example 1 This example provides a method for smelting and purifying low-gas high-purity gold, including the following steps: First, clean the high-purity gold sheet with a purity of 4N using pure water; secondly, under the conditions of a vacuum degree of 1×10 ‐4 Pa and a temperature of 1200 °C, perform vacuum magnetic levitation smelting for 40 minutes. After cooling, take out the low-gas high-purity gold ingot.

[0017] Example 2 This embodiment provides a method for smelting and purifying low-gas high-purity gold, which includes the following steps: First, clean the high-purity gold sheet with a purity of 4N5 using ethanol; Second, perform vacuum magnetic levitation smelting for 60 minutes under the conditions of a vacuum degree of 1×10 ‐3 Pa and a temperature of 1300°C. After cooling, take out the low-gas high-purity gold ingot.

[0018] Example 3 This embodiment provides a method for smelting and purifying low-gas high-purity gold, which includes the following steps: First, clean the high-purity gold with a purity of 5N using pure water; Second, perform vacuum magnetic levitation smelting for 20 minutes under the conditions of a vacuum degree of 1×10 ‐5 Pa and a temperature of 1500°C. After cooling, take out the low-gas high-purity gold ingot.

[0019] Example 4 This embodiment provides a method for smelting and purifying low-gas high-purity gold. Referring to the purification method described in Example 1, the difference is only that: the temperature of vacuum magnetic levitation smelting is 1500°C. That is, the purification method includes the following steps: First, clean the high-purity gold sheet with a purity of 4N using pure water; Second, perform vacuum magnetic levitation smelting for 20 minutes under the conditions of a vacuum degree of 1×10 ‐4 Pa and a temperature of 1500°C, and then take out the low-gas high-purity gold ingot after cooling.

[0020] Example 5 This embodiment provides a method for purifying metallic manganese. Referring to the purification method described in Example 1, the difference is only that the temperature of vacuum magnetic levitation smelting is 1300°C. That is, the purification method includes the following steps: First, clean the high-purity gold with a purity of 4N using pure water; Second, perform vacuum magnetic levitation smelting for 40 minutes under the conditions of a vacuum degree of 1×10 ‐4 Pa and a temperature of 1300°C. After cooling, take out the low-gas high-purity gold ingot.

[0021] Comparative Example 1 This comparative example provides a method for purifying metallic gold. Referring to the purification method described in Example 1, the difference is only that: replace vacuum magnetic levitation smelting with vacuum induction smelting.

[0022] Test the impurity content in the high-purity gold ingots obtained from the above examples and comparative examples. The test method is as follows: Use glow discharge mass spectrometry (GDMS) to detect the metal impurity content in the high-purity gold ingots except for carbon, nitrogen, and oxygen; Use a gas detector to detect the content of carbon, nitrogen, and oxygen impurities in the high-purity gold ingots. List the test results of the impurity content of the above examples and comparative examples in Table 1.

[0023] It can be obtained from Table 1 that: As can be seen from Examples 1-5, the purification method of low-gas high-purity gold according to the present invention removes low-melting-point metal impurities, high-melting-point metal impurities and gas elements in high-purity gold through vacuum magnetic levitation melting, and avoids secondary pollution of the metal by the crucible during the purification process, resulting in low impurity content after purification; Comparing Example 1 with Comparative Example 1 shows that: since vacuum induction melting is used in Comparative Example 1 and a high-purity graphite crucible is used, it is very easy to introduce impurity elements and at the same time cause an increase in the C content.

[0024] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific implementation of the present invention is only limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, without departing from the concept of the present invention, several simple deductions or substitutions can be made, which should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A smelting method for low-gas high-purity gold, characterized in that, It includes the following steps: Step 1: Before vacuum magnetic levitation melting, clean the high-purity gold; Step 2: Under the conditions of a vacuum degree of 1×10 ‐5 ~1×10 ‐2 Pa and a temperature of 1100 - 1500 °C, perform vacuum magnetic levitation melting once, with a time of 10 - 60 min; Step 3: After the melting in Step 2 is completed, take out the low-gas high-purity gold ingot after it has completely cooled.

2. The smelting method of low-gas high-purity gold according to claim 1, characterized in that: The purity of the high-purity gold is 4N to 5N.

3. A smelting method for low-gas high-purity gold according to claim 1, characterized in that: The cleaning agent used for cleaning the high-purity gold in Step 1 is pure water and / or ethanol.

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