A purification and regeneration method for tin stripping waste liquid

Abstract

The present invention discloses a method for purifying and regenerating tin stripping waste liquid, comprising the following steps: preparing a tin stripping waste liquid purification and regeneration additive, wherein the tin stripping waste liquid purification and regeneration additive comprises a hydrochloric acid solution, a soluble barium salt and a soluble tin salt; adding the tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, stirring, filtering, and obtaining a prefabricated tin stripping liquid; adding nitric acid, ferric nitrate and a copper protecting agent to the prefabricated tin stripping liquid to obtain a regenerated tin stripping liquid. The present application generates a barium sulfate precipitate by using the tin stripping waste liquid purification and regeneration additive with sulfate radicals in the tin stripping waste liquid, thereby removing sulfates in the waste liquid, forming a tin oxychloride colloid with nitric acid, and removing organic impurities in the tin stripping waste liquid by colloid adsorption, thereby removing the invalid copper protecting agent in the waste liquid, so as to achieve the purpose of deep purification and regeneration of the tin stripping liquid, and prevent sulfuric acid and the invalid copper protecting agent in the tin stripping liquid from being continuously enriched to a certain extent to affect the tin stripping effect, so that the copper surface of the circuit board after tin stripping by the regenerated tin stripping liquid is not easily oxidized.

Description

Technical Field

[0001] The invention belongs to the field of tin stripping liquid and a method for recycling the liquid after its application, and particularly relates to a method for purifying and regenerating tin stripping waste liquid. Background Art

[0002] Circuit boards are categorized as single-sided or double-sided, depending on whether they have single-sided or double-sided circuitry. However, with the advancement of technology, the circuit board fluids required for various machines have become increasingly complex, and single-sided and double-sided boards are no longer sufficient for higher-performance applications. Consequently, multi-layer circuit boards with complex circuitry have emerged. Multi-layer circuit boards consist of inner and outer layers. The outer layers are covered with an etch-resistant metal, and the pattern transfer is accomplished through etching and tin stripping. Most outer layers are produced using tin as a protective layer. After developing and etching to remove excess copper, tin stripping is performed using a tin stripping solution.

[0003] According to the chemical properties of tin, the tin stripping liquid for the tin protective layer is currently mainly a nitric acid-type tin stripping liquid. Chinese patent CN201610604761.7 discloses a method for stripping a tin stripping liquid and removing a tin-containing layer on a substrate. The tin stripping liquid of the application includes nitric acid, a chelating agent, a stabilizer and an antioxidant. The scheme reduces pollution to the environment. However, there is a disadvantage of nitric acid-type tin stripping liquid. Because it contains at least one of a carboxylic acid compound, a urea compound, and an amino acid, these compounds are easily decomposed during recycling. The regenerated tin stripping liquid is prone to produce hard crystalline particles during use. These particles easily clog the nozzle of the tin stripping equipment, causing the circuit board to be stripped of tin and need to be reworked and stripped again, which reduces production efficiency and causes the circuit board to be scrapped in batches. In order to solve this problem, hydrochloric acid is continuously added to maintain the stripping effect of the tin stripping liquid during the process of stripping the tin of the circuit board. However, the addition of hydrochloric acid reduces the precipitation and separation efficiency of tin ions and copper ions when the tin stripping liquid is regenerated, resulting in a high specific gravity of the regenerated liquid (greater than 1.2g / ml), which makes it easy for the circuit board to become red after stripping.

[0004] After 2018, the treatment method of nitric acid-type tin stripping waste liquid in the circuit board industry has changed. The traditional method of entrusting a third-party enterprise to carry out terminal treatment has gradually changed to recycling and reuse treatment within the circuit board factory. The preparation method of recycled tin stripping liquid mostly uses oxalic acid precipitation to separate the metallic copper and tin in the tin stripping waste liquid, and then adds nitric acid, ferric nitrate, ferric chloride, copper protectors (benzotriazole, methylbenzotriazole, etc.), and inhibitors (ammonium bicarbonate, urea) to prepare the recycled tin stripping liquid. However, production practice from 2018 to 2022 shows that the cycle life of nitric acid-type tin stripping waste liquid regenerated by these methods is relatively short. Generally, the tin stripping waste liquid needs to be outsourced for treatment after 1-3 months of recycling, and the tin stripping liquid must be purchased again. It is impossible to truly achieve the recycling and reuse of tin stripping waste liquid within the circuit board (PCB) factory.

[0005] The reason why nitric acid-based tin stripping liquid needs to be replaced after 1-3 months of regeneration is that after a certain number of cycles, the stripping speed will change, the stripping will not be clean, and the color of the copper surface after stripping will be uneven. In addition, after the copper surface of the circuit is treated with green oil solder mask in the next process, it will appear black, dark, stained, and other phenomena that do not meet quality indicators. The process before the circuit board is stripped is the palladium removal process. After the palladium is removed, a small amount of cleaning water mist will still remain on the surface of the circuit board. The sulfuric acid and other substances remaining in the cleaning water will enter the tin stripping process with the circuit board. After tin stripping, sulfuric acid and other substances will enter the tin stripping waste liquid. The current tin stripping waste liquid regeneration method does not carry out targeted treatment of these pollutants. As a result, sulfuric acid and other substances and the ineffective copper protection agent in the tin stripping liquid are continuously enriched to a certain extent, which will affect the tin stripping effect and easily form a colloidal center, causing tin ions to agglomerate and precipitate, resulting in clogging of the nozzle, uneven spray pressure, poor tin stripping, and organic matter leaving watermarks on the copper surface. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for purifying and regenerating tin stripping waste liquid.

[0007] The present invention discloses a method for purifying and regenerating tin stripping waste liquid, comprising the following steps:

[0008] preparing a tin stripping waste liquid purification and regeneration additive, wherein the tin stripping waste liquid purification and regeneration additive comprises a hydrochloric acid solution, a soluble barium salt and a soluble tin salt;

[0009] adding a tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, stirring, and filtering to obtain a prefabricated tin stripping liquid;

[0010] Nitric acid, ferric nitrate and copper protecting agent are added into the prefabricated tin stripping solution to obtain the regenerated tin stripping solution.

[0011] According to one embodiment of the present invention, the tin stripping waste liquid purification and regeneration additive includes a hydrochloric acid solution, a soluble barium salt and a soluble tin salt, and the mass concentration of the hydrochloric acid solution is 5%-10%;

[0012] Based on the total volume of the tin stripping waste liquid purification and regeneration additive, the molar concentration of barium ions in the barium salt is 0.5-1 mol / L, the molar concentration of tin ions in the tin salt is 0.5-3 mol / L, and the molar concentration ratio of barium ions to tin ions is 1:1-1:3.

[0013] According to one embodiment of the present invention, the barium salt is barium chloride.

[0014] According to one embodiment of the present invention, the tin salt is stannous chloride.

[0015] According to one embodiment of the present invention, before adding the tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, the following steps are also included:

[0016] Pre-treat the tin stripping waste liquid.

[0017] According to one embodiment of the present invention, pre-treatment of tin stripping waste liquid includes the following sub-steps:

[0018] Add oxalic acid to the tin stripping waste liquid to fully react;

[0019] Filter to obtain pretreated tin stripping waste liquid.

[0020] According to one embodiment of the present invention, the addition ratio of the tin stripping waste liquid purification and regeneration additive is 0.5L-1.5L / 1000L.

[0021] According to one embodiment of the present invention, the stirring time is 30-90 minutes.

[0022] According to one embodiment of the present invention, the stirring temperature is room temperature.

[0023] According to one embodiment of the present invention, based on the total volume of the regenerated tin stripping solution, the molar concentration of nitric acid in the regenerated tin stripping solution is 5.6 mol / L-6.2 mol / L.

[0024] The beneficial effects of the present application are: barium sulfate precipitate is generated by purifying the tin stripping waste liquid with the regeneration additive and the sulfate radical in the tin stripping waste liquid, thereby removing sulfate in the waste liquid, forming tin oxychloride colloid with nitric acid, and the colloid adsorbs and removes organic impurities in the tin stripping waste liquid, thereby removing the invalid copper protecting agent in the waste liquid, so as to achieve the purpose of deep purification of the regenerated tin stripping liquid, and prevent sulfuric acid and the invalid copper protecting agent in the tin stripping liquid from being continuously enriched to a certain extent, which will affect the tin stripping effect, so that the copper surface of the circuit board after the regenerated tin stripping liquid is not easily oxidized, keeps bright for a long time, and does not emit yellow smoke during the tin stripping process, and the regenerated tin stripping liquid is not easy to produce precipitation, and there will be no problems of nozzle clogging and uneven spray pressure. The tin stripping effect is consistent with that of the newly purchased tin stripping liquid, which greatly extends the recycling life of the nitric acid type tin stripping waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0026] Figure 1 The figure is a preparation flow chart of a purification and regeneration method for tin stripping waste liquid in an embodiment. DETAILED DESCRIPTION

[0027] The following diagrams illustrate various embodiments of the present invention. For clarity, many practical details are included in the following description. However, it should be understood that these practical details are not intended to limit the present invention. In other words, in some embodiments of the present invention, these practical details are not essential. Furthermore, to simplify the drawings, some commonly used structures and components are depicted in simplified schematic form.

[0028] It should be noted that all directional indications such as up, down, left, right, front, back, etc. in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the various components in a certain specific posture as shown in the accompanying drawings. If the specific posture changes, the directional indication will also change accordingly.

[0029] In addition, in the present invention, descriptions such as "first" and "second" are only used for descriptive purposes and do not specifically refer to the order or sequence, nor are they used to limit the present invention. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0030] Example 1

[0031] The tin stripping waste liquid purification and regeneration additive in this embodiment includes a hydrochloric acid solution, a soluble barium salt and a soluble tin salt. The mass concentration of the hydrochloric acid solution is 5%-10% based on the total volume of the tin stripping waste liquid purification and regeneration additive. The molar concentration of barium ions in the barium salt is 0.5-1mol / L, the molar concentration of tin ions in the tin salt is 0.5-3mol / L, and the molar concentration of barium ions to the molar concentration of tin ions is 1:1-1:3. Preferably, the barium salt is barium chloride and the tin salt is stannous chloride. In this embodiment, the soluble barium salt is analytically pure barium chloride dihydrate and the soluble tin salt is analytically pure stannous chloride dihydrate.

[0032] The barium ions in the tin stripping waste liquid purification and regeneration additive react with the sulfate radicals in the tin stripping waste liquid to form barium sulfate precipitates, thereby removing sulfates in the waste liquid. Stannous chloride and nitric acid form tin oxychloride colloids, which adsorb and remove organic impurities in the tin stripping waste liquid, thereby removing the invalid copper protecting agent in the waste liquid, so as to achieve the purpose of deep purification of the regenerated tin stripping liquid, and prevent sulfuric acid and the invalid copper protecting agent in the tin stripping liquid from being continuously enriched to a certain extent, which will affect the tin stripping effect. The copper surface of the circuit board after tin stripping with the regenerated tin stripping liquid is not easily oxidized, and the brightness time is long. No yellow smoke is emitted during the tin stripping process. In addition, the regenerated tin stripping liquid is not easy to produce precipitation, and there will be no problems such as nozzle clogging and uneven spray pressure. The tin stripping effect is consistent with that of the newly purchased tin stripping liquid, which greatly extends the life of the nitric acid type tin stripping waste liquid.

[0033] Example 2

[0034] Reference Figure 1 , Figure 1 The following is a flow chart of a method for purifying and regenerating tin stripping waste liquid in an embodiment. The method for purifying and regenerating tin stripping waste liquid comprises the following steps:

[0035] S1: Pre-treating the tin stripping waste liquid.

[0036] S2: Prepare the tin stripping waste liquid purification and regeneration additive according to the ratio in Example 1

[0037] S3: adding the tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, stirring, filtering, and obtaining a prefabricated tin stripping liquid.

[0038] S4: adding nitric acid, ferric nitrate and copper protecting agent into the above tin stripping solution to obtain a regenerated tin stripping solution.

[0039] Specifically, step S1 includes the following sub-steps:

[0040] S11: Add oxalic acid to the tin stripping waste liquid to fully react.

[0041] S12: Filter to obtain pretreated tin stripping waste liquid.

[0042] In step S11, oxalic acid reacts with copper ions and tin ions in the tin stripping waste liquid to generate precipitates, thereby removing the copper ions and tin ions in the waste liquid.

[0043] In step S3, the addition ratio of the tin stripping waste liquid purification and regeneration additive is 0.5L-1.5L / 1000L, the stirring time is 30-90 minutes, and the stirring temperature is room temperature. The barium ions in the tin stripping waste liquid purification and regeneration additive react with the sulfate radicals in the tin stripping waste liquid to generate barium sulfate precipitates, thereby removing sulfates in the waste liquid, and stannous chloride and nitric acid form tin oxychloride colloids, which adsorb and remove organic impurities in the tin stripping waste liquid, thereby removing the invalid copper protecting agent in the waste liquid, so as to achieve the purpose of deep purification of the regenerated tin stripping liquid, and prevent sulfuric acid and the invalid copper protecting agent in the tin stripping liquid from being continuously enriched to a certain extent, which will affect the tin stripping effect, so that the copper surface of the circuit board after the regenerated tin stripping liquid is not easily oxidized, keeps bright for a long time, and does not emit yellow smoke during the tin stripping process. In addition, the regenerated tin stripping liquid is not easy to produce precipitation, and there will be no problems of nozzle clogging and uneven spray pressure. The tin stripping effect is consistent with that of the newly purchased tin stripping liquid, which greatly extends the life of the nitric acid type tin stripping waste liquid recycling.

[0044] In step S4, based on the total volume of the regenerated tin stripping solution, the molar concentration of nitric acid in the regenerated tin stripping solution is 5.6 mol / L-6.2 mol / L.

[0045] In order to further understand the content, features and effects of the present invention, the following embodiments are given as examples and described in detail with reference to the accompanying drawings:

[0046] Example 1

[0047] A hydrochloric acid solution with a mass concentration of 5% is added to a reactor, and then barium chloride dihydrate and stannous chloride dihydrate are added in a molar ratio of barium to tin of 1:1, and stirred to dissolve. The molar concentration of barium ions in the prepared tin stripping waste liquid purification and regeneration additive is 0.5 mol / L; the tin stripping waste liquid purification and regeneration additive is added to the pretreated tin stripping waste liquid at a ratio of 1.5L / 1000L, stirred for reaction for 30 minutes, and then filtered to obtain a prefabricated tin stripping liquid after deep purification; a certain amount of nitric acid, ferric nitrate and copper protecting agent are added to the deeply purified tin stripping liquid to prepare a regenerated tin stripping liquid with a nitric acid molar concentration of 5.6 mol / L, and the regenerated tin stripping liquid is compared with a new tin stripping liquid with a nitric acid molar concentration of 5.6 mol / L to test the tin stripping effect. The test result table shows that the regenerated tin stripping liquid is consistent with the new tin stripping liquid in tin stripping speed, copper surface condition after tin stripping, tin stripping liquid appearance, and specific gravity indicators. The regenerated tin stripping liquid has been recycled and used in a certain A electronics factory for two years without any abnormality.

[0048] Example 2

[0049] A hydrochloric acid solution with a mass concentration of 8% is added to a reactor, and then barium chloride dihydrate and stannous chloride dihydrate are added in a molar ratio of barium to tin of 1:2, and stirred to dissolve. The molar concentration of barium ions in the prepared tin stripping waste liquid purification and regeneration additive is 1 mol / L; the tin stripping waste liquid purification and regeneration additive is added to the pretreated tin stripping waste liquid at a ratio of 1L / 1000L, stirred for reaction for 30 minutes, and then filtered to obtain a prefabricated tin stripping liquid after deep purification; a certain amount of nitric acid, ferric nitrate and copper protecting agent are added to the deeply purified tin stripping liquid to prepare a regenerated tin stripping liquid with a nitric acid molar concentration of 6 mol / L, which is compared with a new tin stripping liquid with a nitric acid molar concentration of 6 mol / L to test the tin stripping effect. The test result table shows that the regenerated tin stripping liquid is consistent with the new tin stripping liquid in tin stripping speed, copper surface condition after tin stripping, tin stripping liquid appearance, and specific gravity. The regenerated tin stripping liquid has been recycled and used in a certain B electronics factory for four years without any abnormality.

[0050] Example 3

[0051] A hydrochloric acid solution with a mass concentration of 10% is added to a reactor, and then barium chloride dihydrate and stannous chloride dihydrate are added in a molar ratio of barium to tin of 1:3, and stirred to dissolve. The molar concentration of barium ions in the prepared tin stripping waste liquid purification and regeneration additive is 1.5 mol / L; the tin stripping waste liquid purification and regeneration additive is added to the pretreated tin stripping waste liquid at a ratio of 0.5 L / 1000 L, stirred for reaction for 90 minutes, and then filtered to obtain a prefabricated tin stripping liquid after deep purification; a certain amount of nitric acid, ferric nitrate and copper protecting agent are added to the deeply purified tin stripping liquid to prepare a regenerated tin stripping liquid with a nitric acid molar concentration of 6.2 mol / L, and the regenerated tin stripping liquid is compared with a new tin stripping liquid with a nitric acid molar concentration of 6.2 mol / L to test the tin stripping effect. The test result table shows that the regenerated tin stripping liquid is consistent with the new tin stripping liquid in tin stripping speed, copper surface condition after tin stripping, tin stripping liquid appearance, and specific gravity. The regenerated tin stripping liquid has been recycled and used in a certain C electronics factory for three years without any abnormality.

[0052] In the above test, the tin-plated accompanying plate of the circuit board wet process electroplating process was used for testing. The test results are shown in Table 1.

[0053] Table 1 Performance test results of recycled tin stripping solution

[0054]

[0055] The test results in Table 1 show that the recycled tin stripping liquid is consistent with the new tin stripping liquid in terms of tin stripping speed, copper surface condition after tin stripping, tin stripping liquid appearance, and specific gravity index, indicating that the tin stripping waste liquid purified by the tin stripping waste liquid purification and regeneration additive in this application has excellent performance in terms of tin stripping speed, copper surface condition after tin stripping, and tin stripping liquid appearance.

[0056] In summary, the barium ions in the tin stripping waste liquid purification and regeneration additive in the present application react with the sulfate ions in the tin stripping waste liquid to form barium sulfate precipitates, thereby removing sulfates in the waste liquid, and stannous chloride and nitric acid form tin oxychloride colloid, which adsorbs and removes organic impurities in the tin stripping waste liquid, thereby removing the invalid copper protecting agent in the waste liquid, so as to achieve the purpose of deep purification of the regenerated tin stripping liquid, and prevent sulfuric acid and the invalid copper protecting agent in the tin stripping liquid from continuously enriching to a certain extent, which will affect the tin stripping effect, so that the copper surface of the circuit board after the regenerated tin stripping liquid is not easily oxidized, and the brightness time is long, and no yellow smoke is emitted during the tin stripping process. In addition, the regenerated tin stripping liquid is not easy to produce precipitation, and there will be no problems of nozzle clogging and uneven spray pressure. The tin stripping effect is consistent with that of the newly purchased tin stripping liquid, which greatly extends the recycling life of the nitric acid type tin stripping waste liquid.

[0057] The above is merely an embodiment of the present invention and is not intended to limit the present invention. It will be apparent to those skilled in the art that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be included within the scope of the claims of the present invention.

Claims

1. A method for purifying and regenerating tin stripping waste liquid, characterized in that: The following steps are involved: preparing a tin stripping waste liquid purification and regeneration additive, wherein the tin stripping waste liquid purification and regeneration additive comprises a hydrochloric acid solution, a soluble barium salt, and a soluble tin salt; adding the tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, stirring, and filtering to obtain a prefabricated tin stripping liquid; adding nitric acid, ferric nitrate and a copper protecting agent into the prefabricated tin stripping solution to obtain a regenerated tin stripping solution; The tin stripping waste liquid is a nitric acid type tin stripping waste liquid; In the tin stripping waste liquid purification and regeneration additive, the mass concentration of the hydrochloric acid solution is 5%-10%; based on the total volume of the tin stripping waste liquid purification and regeneration additive, the molar concentration of barium ions in the barium salt is 0.5-1 mol / L, the molar concentration of tin ions in the tin salt is 0.5-3 mol / L, the molar concentration of the barium ions to the molar concentration of the tin ions is 1:1-1:3, the tin salt is stannous chloride, and the addition ratio of the tin stripping waste liquid purification and regeneration additive is 0.5L-1.5L / 1000L.

2. The method for purifying and regenerating tin stripping waste liquid according to claim 1, wherein: The barium salt is barium chloride.

3. The method for purifying and regenerating tin stripping waste liquid according to claim 1, wherein: Before adding the tin stripping waste liquid purification and regeneration additive to the tin stripping waste liquid, the method further comprises the following steps: Pre-treat the tin stripping waste liquid.

4. The method for purifying and regenerating tin stripping waste liquid according to claim 3, wherein: The pretreatment of tin stripping waste liquid includes the following sub-steps: Add oxalic acid to the tin stripping waste liquid to fully react; Filter to obtain pretreated tin stripping waste liquid.

5. The method for purifying and regenerating tin stripping waste liquid according to claim 1, wherein: The stirring time is 30-90 minutes.

6. The method for purifying and regenerating tin stripping waste liquid according to claim 1, characterized in that: The stirring temperature is room temperature.

7. The method for purifying and regenerating tin stripping waste liquid according to claim 1, characterized in that: Based on the total volume of the regenerated tin stripping solution, the molar concentration of nitric acid in the regenerated tin stripping solution is 5.6 mol / L-6.2 mol / L.

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