Formula of environment-friendly renewable tin stripping liquid

Abstract

The invention discloses an environment-friendly renewable tin stripping water formula, and relates to the field of circuit board tin stripping treatment, the tin stripping water formula comprises nitric acid, sulfuric acid, ferric nitrate, ammonium chloride, a slow-release agent and water, and the tin stripping water formula is prepared from the following components by mass: 110-140 g / L of nitric acid, 180-210 g / L of sulfuric acid, 40-50 g / L of ferric nitrate, 12-18 g / L of ammonium chloride, 2-4 g / L of slow-release agent and the balance of water. According to the scheme, nitric acid and sulfuric acid are combined, so that the cost of an acid solution can be reduced, corrosion to underlying copper is reduced, in practical application, on the premise that the copper corrosion amount is controlled to be 0.5 mu m or below, the dosage of a slow-release agent can be reduced, the cost is further reduced, meanwhile, due to the fact that the dosage of the slow-release agent is reduced, organic complexes are greatly reduced, and the service life of the organic complexes is prolonged. Therefore, the treatment difficulty of the waste liquid is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of circuit board tin stripping treatment, and in particular to an environmentally friendly and renewable tin stripping water formula. Background Art

[0002] In the manufacturing process of printed circuit boards (PCBs), the tin stripping process is one of the key steps to remove the tin layer on the surface of the circuit board. Existing tin stripping solution formulas usually contain ingredients such as nitric acid, ferric nitrate, benzotriazole and thiourea. Although these formulas can effectively remove the tin layer, they also have the following problems:

[0003] 1. Severe corrosion to the copper layer: The existing tin stripping water will cause serious corrosion to the copper layer under the tin layer during the tin stripping process, which can easily cause the copper layer to become thinner and affect the performance of the circuit board.

[0004] 2. Large amount of slow-release agent: In order to prevent excessive corrosion of the copper layer, the existing formula needs to add a large amount of slow-release agent (such as benzotriazole and thiourea), which not only increases the material cost, but also increases the difficulty of waste liquid treatment.

[0005] 3. High cost: The cost of ingredients in existing formulas is relatively high, especially the large amount of nitric acid used, which leads to high overall costs.

[0006] 4. Difficulty in treating waste liquid: The existing waste liquid from tin stripping is highly oxidizing, and it is difficult to recover elemental tin through electrolysis, which makes it difficult to regenerate the waste liquid, which is not conducive to environmental protection and resource recycling. Summary of the invention

[0007] The purpose of the present invention is to provide an environmentally friendly and renewable tin stripping water formula that is easy to use.

[0008] The technical solution adopted by the present invention is as follows:

[0009] An environmentally friendly and renewable tin stripping water formula comprises nitric acid, sulfuric acid, ferric nitrate, ammonium chloride, a sustained-release agent and water. The tin stripping water formula is prepared according to the following mass components: 110-140 g / L nitric acid, 180-210 g / L sulfuric acid, 40-50 g / L ferric nitrate, 12-18 g / L ammonium chloride, 2-4 g / L sustained-release agent, and the balance is water.

[0010] In the above scheme, the combination of nitric acid and sulfuric acid can not only reduce the cost of acid solutions, but also reduce the corrosion of the underlying copper, compared with the traditional single nitric acid component. In practical applications, under the premise of ensuring that the copper corrosion amount is controlled below 0.5μm, the amount of slow-release agent can be reduced to further reduce the cost. At the same time, due to the reduction in the amount of slow-release agent, the organic complex is greatly reduced, thereby reducing the difficulty of waste liquid treatment; the setting of ferric nitrate can promote the dissolution of tin. During the tin stripping process, ferric nitrate reacts with tin to form soluble tin salts, making it easier for tin to fall off the substrate. Usually, the tin etching rate can reach more than 20um / min, thereby improving production efficiency; the setting of ammonium chloride can enhance the corrosion of the copper-tin alloy layer; the setting of the slow-release agent is used to protect the copper layer. Through the combination of the above schemes, in practical applications, the cost of tin stripping water can be reduced by about 1 / 3, and the waste liquid after use is easy to treat and reuse, which is more environmentally friendly and has excellent commercial significance.

[0011] It is worth mentioning that the scheme is regulated by mass components. In practical applications, the acid value of nitric acid is controlled to 2.0N and the acid value of sulfuric acid is controlled to 4.0N. If solution preparation is adopted, taking 1L tin stripping aqueous solution, concentrated nitric acid (usually with a mass fraction of 68% and a density of 1.41g / mL) (target 126g / L) and concentrated sulfuric acid (usually with a mass fraction of 98% and a density of 1.84g / mL) (target 196g / L) as an example, the actual volume of concentrated nitric acid to be added is: volume = 1.41g / mL × 0.68126g ≈ 131.5mL; the actual volume of concentrated sulfuric acid to be added is: volume = 1.84g / mL × 0.98196g ≈ 108.7mL; therefore, in the preparation process, first add 132mL of nitric acid to the water, and then add 110mL of concentrated sulfuric acid, and add other raw materials in the same way. After cooling, the volume is fixed to 1L.

[0012] Preferably, the sustained-release agent includes one or more of benzotriazole, thiourea, sodium molybdate, imidazole compounds, and phosphates.

[0013] Preferably, the sustained-release agent is benzotriazole and thiourea. The sustained-release agent can be freely combined and selected as needed, for example: a combination of benzotriazole + sodium molybdate; a combination of imidazole compounds + phosphates; a combination of thiourea + benzotriazole. The present application scheme preferably uses a combination of thiourea + benzotriazole, which can promote the dissolution of tin, improve the selectivity and efficiency of tin stripping, stabilize the chemical properties of the tin stripping agent, and extend its service life while ensuring the protection of the substrate.

[0014] Preferably, the tin stripping water formula is prepared according to the following mass components: 126g / L nitric acid, 196g / L sulfuric acid, 43g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.

[0015] Preferably, the tin stripping water formula is prepared according to the following mass components: 130g / L nitric acid, 200g / L sulfuric acid, 45g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.

[0016] Preferably, the tin stripping water formula is prepared according to the following mass components: 125g / L nitric acid, 195g / L sulfuric acid, 45g / L ferric nitrate, 14g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.

[0017] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0018] 1. Reduce copper layer corrosion: The tin stripping water formula of the present invention significantly reduces the corrosion of the copper layer under the tin layer during use, and the copper corrosion amount is controlled below 0.5 μm, thereby avoiding the occurrence of copper thinning.

[0019] 2. Reduce the amount of sustained-release agent: The amount of sustained-release agent (benzotriazole and thiourea) is reduced by 2 / 3 compared with the existing technology, which reduces material costs and alleviates the difficulty of waste liquid treatment.

[0020] 3. Reduce costs: By using sulfuric acid to replace part of nitric acid, the cost of tin stripping water is reduced by about 1 / 3 compared with the existing technology.

[0021] 4. Waste liquid regeneration: The oxidizing property of the waste liquid is greatly reduced, and the elemental tin can be recovered through electrolytic treatment to achieve the regeneration and recycling of the liquid medicine, thus reducing environmental pollution. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below through embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The groups and embodiments of the present invention generally shown can be arranged and designed in various different configurations.

[0023] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention.

[0024] It should be noted that relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0025] Example 1: An environmentally friendly and renewable tin stripping solution formula is prepared according to the following mass components: 126g / L nitric acid, 196g / L sulfuric acid, 43g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water. The formula significantly reduces the corrosion of the copper layer during use, and the copper corrosion amount is controlled below 0.5μm. The waste liquid can be electrolytically treated to recover elemental tin, thereby realizing the regeneration of the solution.

[0026] Example 2: The tin stripping water formula is prepared according to the following mass components: 130g / L nitric acid, 200g / L sulfuric acid, 45g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water. The cost of this formula is reduced by about 1 / 3 compared with the existing technology, and the difficulty of waste liquid treatment is significantly reduced.

[0027] Example 3: The tin stripping water formula is prepared according to the following mass components: 125g / L nitric acid, 195g / L sulfuric acid, 45g / L ferric nitrate, 14g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water. The amount of the sustained-release agent used in this formula is reduced by 2 / 3 compared with the prior art, and the content of organic complexes in the waste liquid is reduced by more than 50%.

[0028] During use, you only need to place the product to be detinned in the prepared detinning water, control the temperature between 25-50°, and take out the product after the detinning is completed.

[0029] When the tin stripping wastewater needs to be treated, it is only necessary to electrolyze the tin stripping wastewater first, control the electrolysis voltage to 1.5V-2.0V, and electrolyze the elemental tin; then regenerate the electrolyzed solution, adjust the pH value to 2.0-3.0, and add nitric acid, sulfuric acid and formula liquid to the initial concentration so that it can be recycled.

[0030] From the above, it can be seen that compared with traditional tin stripping water, the present application scheme not only reduces production costs and reduces corrosion to the copper layer, but also greatly reduces the oxidizing property of the waste liquid, which can be regenerated and recycled after electrolysis.

[0031] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An environmentally friendly and renewable tin stripping water formula, characterized in that: The tin stripping water formula includes nitric acid, sulfuric acid, ferric nitrate, ammonium chloride, a sustained-release agent and water. The tin stripping water formula is prepared according to the following mass components: nitric acid 110-140g / L, sulfuric acid 180-210g / L, ferric nitrate 40-50g / L, ammonium chloride 12-18g / L, sustained-release agent 2-4g / L, and the balance is water.

2. The environmentally friendly and renewable tin stripping water formula according to claim 1, characterized in that: The sustained-release agent includes one or more of benzotriazole, thiourea, sodium molybdate, imidazole compounds, and phosphates.

3. The environmentally friendly and renewable tin stripping water formula according to claim 2, characterized in that: The sustained-release agents are benzotriazole and thiourea.

4. The environmentally friendly and renewable tin stripping water formula according to claim 3, characterized in that: The tin stripping water formula is prepared according to the following mass components: 126g / L nitric acid, 196g / L sulfuric acid, 43g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.

5. The environmentally friendly and renewable tin stripping water formula according to claim 3, characterized in that: The tin stripping water formula is prepared according to the following mass components: 130g / L nitric acid, 200g / L sulfuric acid, 45g / L ferric nitrate, 15g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.

6. The environmentally friendly and renewable tin stripping water formula according to claim 3, characterized in that: The tin stripping water formula is prepared according to the following mass components: 125g / L nitric acid, 195g / L sulfuric acid, 45g / L ferric nitrate, 14g / L ammonium chloride, 1g / L benzotriazole, 2g / L thiourea, and the balance is water.