Method for plating indium on surface of copper back plate for recycling target material

Abstract

The invention discloses a method for plating indium on the surface of a copper back plate for recycling a target material. The method comprises the following steps: adjusting the pH value of a sodium chloride solution to 1-3.5 by using an acid solution to obtain an electrolyte; an inert cathode plate is used as a cathode, and a copper back plate is used as an anode; and controlling the electrolytic voltage to be 0.1-5V, carrying out an electrolytic reaction to obtain an indium-containing electrolyte and an indium layer deposited on the surface of the inert cathode plate, and finally recovering indium in the indium-containing electrolyte and the indium layer to obtain an indium hydroxide precipitate. By means of low-voltage selective electrolysis, efficient anode dissolution and cathode directional deposition of indium are achieved, physical mixing or chemical co-dissolution of copper and indium is avoided, the purity of recycled metal indium is high, corrosion to a copper backboard base body is small, operation is easy, automatic line production is facilitated, the recycling efficiency is high, the working voltage is low, energy consumption is small, cost is low, and toxic waste gas is avoided. The electrolyte can be recycled, the waste liquid amount is small, and pollution is avoided.

Description

Technical Field

[0001] This invention relates to the field of target material waste recycling technology, and in particular to a method for indium plating on the surface of a copper backing plate for recycling targets. Background Technology

[0002] With the rapid development of the semiconductor and display industries, magnetron sputtering technology has been widely used as a key thin-film deposition process. In this process, ceramic targets are typically bonded firmly to a copper backing plate using indium as a soldering material to form a complete sputtering target assembly. As production continues, a large amount of waste copper backing plates coated with indium are generated. Indium, due to its excellent conductivity, ductility, low melting point, and good bonding properties with ceramics and copper, has become the preferred material for this type of soldering. However, indium is a scarce and expensive metal; therefore, the efficient and economical recycling of waste copper backing plates has significant economic value and strategic importance.

[0003] In existing technologies, the recovery of indium plating on copper backplates is mainly divided into physical recovery and chemical recovery. Physical recovery employs mechanical scraping and mechanical turning methods. Mechanical scraping involves heating and softening the indium plating, followed by manual scraping with a scraper. However, due to the difficulty in precisely controlling the contact between the scraper and the copper plate surface, incomplete scraping occurs, resulting in high indium residue and low recovery rates. Furthermore, excessive scraping damages the copper substrate, generating a large amount of indium-contaminated copper shavings, making subsequent copper-indium separation difficult and causing damage to the copper plate itself. While mechanical scraping is simple to operate, it is labor-intensive and has low recovery efficiency. Mechanical turning, on the other hand, involves directly turning the copper plate surface with lathes or other equipment to remove the indium plating. Although this improves recovery efficiency, it also generates physically mixed copper-indium alloy debris, which is fine-grained. The tight bond between copper and indium makes subsequent efficient separation processes using chemical or physical methods extremely complex, costly, and difficult to guarantee the purity of the indium product. Chemical recovery employs acid leaching, utilizing indium's solubility in acidic solutions for chemical stripping. However, commonly used acidic solutions (such as hydrochloric acid and sulfuric acid) corrode the copper substrate to varying degrees while dissolving indium. Furthermore, acid leaching requires large quantities of acidic solutions, which not only damages the copper plate and contaminates the indium solution with copper ions but also increases the difficulty of solution purification and separation. It also necessitates the treatment of large amounts of waste acid, resulting in severe environmental pressure and high wastewater treatment costs.

[0004] Existing methods for recycling indium plating on copper backplates suffer from problems such as cumbersome operation, high labor intensity, low recycling purity, difficulty in separating copper and indium, high cost, and easy environmental pollution. These methods are difficult to meet the needs of industrial-scale recycling and therefore need to be improved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for indium plating on the copper backing surface of recycled targets, thereby solving problems such as low recycling efficiency, easy pollution, difficulty in separating copper and indium, inability to scale up recycling, and high recycling costs in existing technologies.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: a method for indium plating on the surface of a copper backplate of a recycled target material, comprising the following steps:

[0007] S1, Electrolyte preparation step: Dissolve sodium chloride in water to obtain sodium chloride solution, adjust the pH of sodium chloride solution to 1~3.5 using acidic solution, and obtain electrolyte after uniform mixing;

[0008] S2, the step of preparing the electrolysis environment: an inert cathode plate made of metal or graphite is placed horizontally at the bottom of the electrolytic cell, and the electrolyte obtained in step S1 is injected into the electrolytic cell.

[0009] S3, Step 1: Install the copper backplate to be treated. Set the copper backplate with the indium plating layer on its surface horizontally, so that the side of the copper backplate with the indium plating layer faces the inert cathode plate. Move the copper backplate horizontally downward until the indium plating layer of the copper backplate penetrates below the surface of the electrolyte, and ensure that the distance between each point on the plane of the indium plating layer and the surface of the inert cathode plate is equal.

[0010] S4, Connect the circuit and electrolysis steps, connect the inert cathode plate to the negative terminal of the power supply, connect the copper back plate to the positive terminal of the power supply, control the electrolysis voltage to 0.1~5V to carry out the electrolysis reaction, and obtain an indium-containing electrolyte and an indium layer deposited on the surface of the inert cathode plate.

[0011] In a further technical solution, the following steps are included after step S4:

[0012] S5, Indium recovery step, ammonia is added to the indium-containing electrolyte for neutralization, and the mixture is stirred and precipitated to obtain indium hydroxide precipitate;

[0013] The indium layer on the surface of the inert cathode plate is peeled off, dissolved in hydrochloric acid, sulfuric acid or nitric acid, and finally neutralized with ammonia water. After stirring and precipitation, indium hydroxide precipitate is obtained.

[0014] In a further technical solution, in step S1, the concentration of the sodium chloride solution is 20~200g / L.

[0015] In a further technical solution, the inert cathode plate is one of stainless steel cathode plates, titanium plates, graphite plates, and precious metal coated plates.

[0016] In a further technical solution, the inert cathode plate is a stainless steel cathode plate, and a stainless steel rod is welded to the corner of the stainless steel cathode plate. The stainless steel rod is set perpendicular to the stainless steel cathode plate. In step S2, the upper end of the stainless steel rod extends out of the electrolyte surface. In step S4, the upper end of the stainless steel rod is electrically connected to the negative terminal of the power supply.

[0017] In a further technical solution, the projection of the copper back plate in the vertical direction is located within the inert cathode plate.

[0018] In a further technical solution, the thickness t of the inert cathode plate is 1~20mm.

[0019] In a further technical solution, in step S2, the liquid level height h of the electrolyte in the electrolytic cell is 22~300mm;

[0020] In step S3, the indium plating layer of the copper back plate penetrates 0.1 to 10 mm below the surface of the electrolyte.

[0021] In a further technical solution, in step S4, the electrolysis reaction time is 0.5 to 24 hours.

[0022] In a further technical solution, in step S1, the acidic solution is sulfuric acid.

[0023] The advantages of this invention compared to existing technologies are as follows: by using low-voltage electrolysis and a weakly acidic chlorine-containing electrolyte, the indium plating layer on the surface of the copper backplate can be effectively dissolved without corroding the copper substrate, achieving selective stripping of indium. After the dissolved indium ions migrate to the cathode, they are reduced to high-purity elemental indium on the surface of the inert cathode plate and deposited. This avoids the mechanical mixture of copper and indium generated by physical scraping or turning, as well as the copper-indium co-dissolution contamination caused by chemical acid leaching, thereby directly obtaining high-purity metallic indium and simplifying subsequent refining processes.

[0024] Because the electrolysis process has very low corrosivity to the copper substrate, the surface damage of the treated copper backplate is minimal. After simple cleaning, the copper backplate can be directly reused for target bonding or used as high-grade copper material for regeneration and smelting, which improves the resource utilization value and economy of the entire target assembly.

[0025] Recovery can be achieved by controlling the parallelism and voltage value between the copper backplate and the inert cathode plate. The control method is simple and reliable, requires low skill from operators, facilitates automated continuous recovery operations, enables batch automated recovery, and improves recovery efficiency.

[0026] The recycling process uses only electrolyte as a consumable and a small amount of sulfuric acid. The inert cathode plate can be reused for a long time. The electrolysis voltage is low, the energy consumption is low, and the recycling cost is low. The entire recycling process is carried out at room temperature or low temperature, and no toxic or harmful gases are generated. The electrolyte system is stable and can be recycled for a long time. Only periodic replenishment and small-scale treatment are required. The amount of waste liquid generated is far less than that of the one-time acid leaching method. It does not produce complex indium copper shavings or heavy metal sludge, and is environmentally friendly and pollution-free. Attached Figure Description

[0027] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0028] Figure 1 This is a schematic diagram of the electrolysis process of the present invention;

[0029] Figure 2 This is a schematic diagram of the copper backplate before electrolysis in Embodiment 1 of the present invention;

[0030] Figure 3 This is a schematic diagram of the copper backplate after electrolysis according to Embodiment 1 of the present invention;

[0031] Figure 4 This is the EDS spectrum of the surface of sample 1 of the present invention;

[0032] Figure 5 This is the EDS spectrum of the surface of sample 2 of the present invention;

[0033] Figure 6 This is the EDS spectrum of the surface of sample 3 of the present invention;

[0034] Figure 7 This is the EDS spectrum of the surface of sample 4 of the present invention.

[0035] In the picture:

[0036] 1 Electrolytic cell, 2 Electrolyte, 3 Copper backplate, 31 Indium plating, 4 Stainless steel cathode plate, 41 Stainless steel rod. Detailed Implementation

[0037] The following are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention.

[0038] Example 1

[0039] A method for indium plating on the surface of a copper backing plate for recycling targets, such as Figures 1 to 4 As shown, it includes the following steps:

[0040] S1, Electrolyte preparation step 2: Dissolve sodium chloride in water to obtain a sodium chloride solution with a concentration of 60 g / L, adjust the pH value of the sodium chloride solution to 2 using an acidic solution, and then mix them evenly to obtain electrolyte 2.

[0041] Specifically, the acidic solution is sulfuric acid.

[0042] Sodium chloride provides a high concentration of chloride ions. It can react with indium ions Formation of stable complex ions This method significantly improves the solubility and reaction rate of indium and inhibits indium salt hydrolysis. By precisely adjusting the pH to a weakly acidic state (pH=2) using sulfuric acid, an ideal electrochemical window is created that effectively dissolves indium while greatly inhibiting corrosion of the copper substrate. This ensures efficient and preferential dissolution of indium while maximally protecting the copper backing plate, achieving source separation of copper and indium and laying the chemical foundation for obtaining high-purity indium products. The raw materials used are inexpensive and readily available, resulting in low costs.

[0043] S2, preparing the electrolysis environment step: place an inert cathode plate made of metal or graphite horizontally at the bottom of the electrolytic cell 1, and inject the electrolyte 2 obtained in step S1 into the electrolytic cell 1. The liquid level height h of the electrolyte 2 is 22~300mm.

[0044] Specifically, in this embodiment, the inert cathode plate is a stainless steel cathode plate 4, and the thickness of the stainless steel cathode plate 4 is 1~20mm. Since the electrolyte 2 is an acidic sodium chloride solution, and the stainless steel cathode plate 4 has sufficient resistance to pitting corrosion and uniform corrosion in this environment, it can ensure that it is not rapidly corroded or dissolved during the electrolysis process, avoiding the introduction of impurity ions such as iron, chromium, and nickel to contaminate the electrolyte and the subsequently recovered indium; and the surface of the stainless steel cathode plate 4 is easy to process into a smooth and flat plane, which can form a uniform electric field with the anode, so that the indium plating layer can be uniformly and completely dissolved and deposited; since indium is soft and has a low melting point, the adhesion of the indium layer electrodeposited on the surface of the stainless steel cathode plate 4 is relatively weak, and it is easy to completely peel off by physical methods such as scraping, bending, and vibration, which facilitates recycling.

[0045] Of course, the inert cathode plate is not limited to the stainless steel cathode plate 4. Other inert conductive materials that are stable in the electrolyte 2 can also be used, including but not limited to titanium plates, graphite plates or precious metal coated plates. Precious metal coated plates are substrates with precious metals on their surfaces to ensure that the cathode itself does not participate in the reaction, maintain the purity of the electrolyte 2, and facilitate the deposition and recovery of indium.

[0046] Specifically, a stainless steel rod 41 is welded to the corner of the stainless steel cathode plate 4. The stainless steel rod 41 is perpendicular to the stainless steel cathode plate 4, and its upper end extends beyond the surface of the electrolyte 2. This provides a reliable, convenient, and isolated electrical connection from the electrolyte 2. The vertically welded stainless steel rod 41 acts as a conductive rod, ensuring good overall conductivity of the stainless steel cathode plate 4. It also avoids problems such as solution leakage, poor contact, or interference with the electric field that may occur if perforations are made on the surface of the stainless steel cathode plate 4 or clamping devices are used. This improves the reliability and durability of the connection, reduces potential failure points, and facilitates installation and maintenance in industrial applications.

[0047] S3, Install the copper backplate 3 to be processed. The copper backplate 3, with its surface coated with an indium layer 31, is horizontally positioned so that the side of the copper backplate 3 with the indium layer 31 faces the inert cathode plate. The vertical projection of the copper backplate 3 lies within the inert cathode plate. The copper backplate 3 is then moved horizontally downwards until the indium layer 31 penetrates 1 mm below the surface of the electrolyte 2, ensuring that the distance between each point on the plane of the indium layer 31 and the surface of the inert cathode plate is equal. The area of ​​the copper backplate 3 is equal to or smaller than the area of ​​the inert cathode plate, thereby ensuring that the indium layer 31 can be completely deposited on the inert cathode plate, improving the recovery rate.

[0048] S4, Connect the circuit and electrolysis steps: Connect the upper end of the stainless steel rod 41 to the negative terminal of the power supply, and connect the copper back plate 3 to the positive terminal of the power supply. Control the electrolysis voltage at 0.5V and perform the electrolysis reaction for 20 hours to obtain an indium-containing electrolyte and an indium layer deposited on the surface of the inert cathode plate. Apply a low DC voltage to drive the electrochemical reaction, using the copper back plate 3 as the anode. Under the action of the electric field, the metallic indium in the indium-plated layer 31 undergoes an oxidation reaction and enters the electrolyte in ionic form. These indium ions migrate to the surface of the cathode (inert cathode plate), are reduced to metallic indium, and deposited. .

[0049] S5, In the indium recovery step, ammonia is added to the indium-containing electrolyte for neutralization, and the mixture is stirred and precipitated to obtain indium hydroxide precipitate. During the electrolysis process, trace amounts of copper ions will dissolve, but the amount of copper ions dissolved is far lower than the copper ion loss in the prior art. The copper ions in electrolyte 2 will remain in electrolyte 2 in the form of copper ammonia complex after being neutralized by ammonia, so they will not cause pollution to the indium hydroxide precipitate.

[0050] The indium layer on the surface of the inert cathode plate is peeled off by light scraping to avoid damaging the copper back plate 3. Then it is dissolved with hydrochloric acid, sulfuric acid or nitric acid, and finally neutralized with ammonia water. After stirring and precipitation, indium hydroxide precipitate is obtained.

[0051] Of course, methods for extracting indium ions from indium-containing electrolytes include, but are not limited to, the method used in this embodiment. Alternatively, extraction methods in the prior art can be used to purify the indium to obtain metallic indium with a purity greater than or equal to 5N.

[0052] Example 2

[0053] The steps in this embodiment are basically the same as those in Embodiment 1, except that in step S4, the electrolysis voltage is controlled at 1.5V for 5 hours for electrolysis reaction.

[0054] Example 3

[0055] The steps in this embodiment are basically the same as those in Embodiment 1, except that in step S4, the electrolysis voltage is controlled to be 3V to carry out the electrolysis reaction for 1 hour.

[0056] The same piece of waste copper back plate 3 with indium plating 31 was divided into four pieces. The indium plating 31 of the four copper back plates 3 was recycled using Examples 1, 2, 3 and 4 respectively. The copper back plate 3 after the indium recycling step in Example 1 was marked as Sample 1, the copper back plate 3 after the indium recycling step in Example 2 was marked as Sample 2, the copper back plate 3 after the indium recycling step in Example 3 was marked as Sample 3, and the copper back plate 3 after the indium recycling step in Example 4 was marked as Sample 4. The side of Sample 1, Sample 2, Sample 3 and Sample 4 with the original indium plating layer was detected using an EDS spectrometer.

[0057] The EDS spectrum of sample 1 is as follows: Figure 4 As shown, a total of carbon, oxygen, sulfur, chlorine and copper elements were detected. The normalized mass ratio of carbon was 10.53%, oxygen was 13.45%, sulfur was 0.57%, chlorine was 1.77%, and copper was 73.68%. No indium was detected.

[0058] The EDS spectrum of sample 2 is as follows Figure 5 As shown, a total of carbon, oxygen, sulfur, chlorine and copper elements were detected. The normalized mass ratio of carbon was 10.93%, oxygen was 10.51%, sulfur was 0.93%, chlorine was 0.64%, and copper was 76.99%. No indium was detected.

[0059] The EDS spectrum of sample 3 is as follows: Figure 6As shown, a total of carbon, oxygen, chlorine, and copper elements were detected. The normalized mass ratio of carbon was 5.87%, that of oxygen was 16.92%, that of chlorine was 10.06%, and that of copper was 67.14%. No indium was detected.

[0060] The EDS spectrum of sample 4 is as follows: Figure 7 As shown, a total of carbon, oxygen, chlorine, and copper elements were detected. The normalized mass ratio of carbon was 12.58%, that of oxygen was 6.57%, that of chlorine was 0.67%, and that of copper was 80.17%. No indium was detected.

[0061] Therefore, the presence of metallic indium was detected in samples 1, 2, 3, and 4. During electrolysis, the higher the electrolysis voltage and the shorter the electrolysis time, the higher the electrolysis efficiency, and the corresponding recovery efficiency also increases. This invention uses low-voltage electrolysis with a weakly acidic chlorine-containing electrolyte 2, which can effectively dissolve the indium plating layer 31 on the surface of the copper backplate 3 without corroding the copper substrate. This achieves selective stripping of indium. The dissolved indium ions migrate to the cathode and are reduced to high-purity elemental indium on the surface of the inert cathode plate and deposited. This avoids the mechanical mixture of copper and indium generated by physical scraping or turning, as well as the copper-indium co-dissolution contamination caused by chemical acid leaching, thereby directly obtaining high-purity metallic indium and simplifying subsequent refining processes.

[0062] Because the electrolysis process has very low corrosiveness to the copper substrate, the surface damage of the treated copper backplate 3 is minimal. After simple cleaning, the copper backplate 3 can be directly reused for target bonding or used as a high-grade copper material for regeneration and smelting, which improves the resource utilization value and economy of the entire target assembly.

[0063] Recovery can be completed by controlling the parallelism and voltage value between the copper back plate 3 and the inert cathode plate. The control method is simple and reliable, requires low skill from operators, facilitates automated continuous recovery operations, enables batch automated recovery, and improves recovery efficiency.

[0064] The recycling process uses only electrolyte 2 as a consumable and a small amount of sulfuric acid. The inert cathode plate can be reused for a long time. The electrolysis voltage is low, the energy consumption is small, and the recycling cost is low. The entire recycling process is carried out at room temperature or low temperature, and no toxic or harmful gases are generated. The electrolyte system is stable and can be recycled for a long time. Only periodic replenishment and small-scale treatment are required. The amount of waste liquid generated is far less than that of the one-time acid leaching method. It will not produce complex indium copper shavings or heavy metal sludge, making it environmentally friendly and pollution-free.

Claims

1. A method for indium plating on the surface of a copper backing plate for recycling target materials, characterized in that: Includes the following steps, S1, Prepare electrolyte (2) Step: Dissolve sodium chloride in water to obtain sodium chloride solution, adjust the pH of sodium chloride solution to 1~3.5 using acidic solution, and mix evenly to obtain electrolyte (2). S2, prepare the electrolysis environment step, place an inert cathode plate made of metal or graphite horizontally at the bottom of the electrolytic cell (1), and inject the electrolyte (2) obtained in step S1 into the electrolytic cell (1). S3, Install the copper backplate (3) to be treated. Set the copper backplate (3) with the indium plating layer (31) on its surface horizontally, so that the side of the copper backplate (3) with the indium plating layer (31) faces the inert cathode plate. Move the copper backplate (3) down in parallel until the indium plating layer (31) of the copper backplate (3) penetrates below the liquid surface of the electrolyte (2), and ensure that the distance between each point on the plane of the indium plating layer (31) and the surface of the inert cathode plate is equal. S4, Connect the circuit and electrolysis steps, connect the inert cathode plate to the negative terminal of the power supply, connect the copper back plate (3) to the positive terminal of the power supply, control the electrolysis voltage to 0.1~5V to carry out the electrolysis reaction, and obtain an indium-containing electrolyte and an indium layer deposited on the surface of the inert cathode plate.

2. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: The following steps are also included after step S4. S5, Indium recovery step, ammonia is added to the indium-containing electrolyte for neutralization, and indium hydroxide precipitate is obtained by stirring and precipitation. The indium layer on the surface of the inert cathode plate is peeled off, dissolved in hydrochloric acid, sulfuric acid or nitric acid, and finally neutralized with ammonia water. After stirring and precipitation, indium hydroxide precipitate is obtained.

3. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: In step S1, the concentration of the sodium chloride solution is 20~200g / L.

4. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: The inert cathode plate is one of stainless steel cathode plate (4), titanium plate, graphite plate and precious metal plate.

5. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 4, characterized in that: The inert cathode plate is a stainless steel cathode plate (4). A stainless steel rod (41) is welded to the corner of the stainless steel cathode plate (4). The stainless steel rod (41) is set perpendicular to the stainless steel cathode plate (4). In step S2, the upper end of the stainless steel rod (41) extends out of the liquid surface of the electrolyte (2). In step S4, the upper end of the stainless steel rod (41) is electrically connected to the negative electrode of the power supply.

6. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: The projection of the copper back plate (3) in the vertical direction is located within the inert cathode plate.

7. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: The thickness of the inert cathode plate is t, which is 1~20mm.

8. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: In step S2, the liquid level height h of the electrolyte (2) in the electrolytic cell (1) is 22~300mm; in step S3, the indium plating layer (31) of the copper back plate (3) penetrates 0.1~10mm below the liquid level of the electrolyte (2).

9. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: In step S4, the electrolysis reaction time is 0.5 to 24 hours.

10. The method for indium plating on the surface of a copper backing plate for recycling target material according to claim 1, characterized in that: In step S1, the acidic solution is sulfuric acid.

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