Circuit board thin tin etching solution and preparation method thereof

Abstract

The invention relates to the field of etching solutions, in particular to a thin tin etching solution for a circuit board and a preparation method of the thin tin etching solution. The thin tin etching liquid for the circuit board comprises a main agent and an auxiliary agent, the main agent comprises the following raw materials: 4-6% of inorganic acid, 15-20% of organic acid, 5-8% of an oxidant, 1-3% of a complexing agent, 2-3.5% of an auxiliary agent, 2.5-4% of a protective agent, 0.5-1% of a copper protection agent, 0.5-1.5% of a stabilizer, 3-5% of a carboxyl compound and the balance of deionized water. And the auxiliary agent comprises the following raw materials: 6-8% of inorganic acid, 10-14% of organic acid, 2-4% of an oxidizing agent, 1-3% of a carboxyl compound and the balance of deionized water. The thin tin etching solution for the circuit board prepared by the invention not only has excellent etching precision and good etching effect, avoids the phenomena of chamfering, trailing, tin dissolution and tin surface oxidation, but also has extremely high load capacity and self stability, and meets the performance requirements of the existing thin tin etching solution in the existing circuit board manufacturing field.

Description

Technical Field

[0001] The present application relates to the field of etching liquid, and in particular to a circuit board thin tin etching liquid and a preparation method thereof. Background Art

[0002] In the electronics manufacturing industry, circuit boards are the basic platform for assembling electronic components, and the etching process of thin tin layers is an indispensable part of manufacturing high-quality multi-layer circuit boards. Etching liquids are widely used in the manufacturing process of printed circuit boards (PCBs) to accurately remove unwanted metal layers to form the desired conductive line patterns. As electronic products develop towards miniaturization, lightness and high performance, higher requirements are placed on the fine line production of circuit boards, which not only requires the etching liquid to have good selectivity, uniformity and stability, but also to ensure good surface quality and no residue after etching.

[0003] Traditional thin tin etching solutions are mainly based on chemical components such as ferric chloride (FeCl3) solution or sulfuric acid-hydrogen peroxide mixture. Although these traditional etching solutions can meet basic etching needs, they have some limitations and challenges. For example, ferric chloride solution is prone to over-etching or side etching due to its high corrosiveness and difficult-to-control characteristics, affecting the accuracy and reliability of the final product. In addition, it may also cause environmental pollution and has high processing costs. On the other hand, although the sulfuric acid-hydrogen peroxide system provides better etching effects, it releases harmful gases during use, and due to its strong oxidizing properties, it may damage non-target materials such as polymer coatings on substrates.

[0004] However, the existing circuit board thin tin etching liquid still has the problems of insufficient etching precision, obvious shortcomings in etching effect, such as chamfering and tailing, as well as low load and poor self-stability. Therefore, in order to solve the above problems, the present application provides a circuit board thin tin etching liquid and a preparation method thereof, and the finally prepared etching liquid not only has excellent etching precision and good etching effect, but also avoids the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation, and has extremely high load and self-stability, meeting the performance requirements of the existing circuit board manufacturing field for the existing thin tin etching liquid. Summary of the invention

[0005] In order to solve the above problems, the first aspect of the present application provides a circuit board thin tin etching solution, including a main agent and an auxiliary agent; the main agent, in terms of mass percentage, comprises the following raw materials: 4-6% inorganic acid, 15-20% organic acid, 5-8% oxidant, 1-3% complexing agent, 2-3.5% auxiliary agent, 2.5-4% protective agent, 0.5-1% copper protecting agent, 0.5-1.5% stabilizer, 3-5% carboxyl compound, and deionized water to supplement the balance.

[0006] As a preferred solution, the auxiliary agent, in terms of mass percentage, comprises the following raw materials: 6-8% inorganic acid, 10-14% organic acid, 2-4% oxidant, 1-3% carboxyl compound, and the balance is made up of deionized water.

[0007] As a preferred solution, the dosage relationship between the main agent and the auxiliary agent is: etching is performed with the main agent, and as the etching progresses, the auxiliary agent is added at a mass percentage of 0.2 to 0.25% of the main agent for every 200 ppm increase in the concentration of the loaded tin ions.

[0008] As a preferred solution, the inorganic acid is at least one of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and hydrofluoric acid.

[0009] As a preferred solution, the inorganic acid is nitric acid or hydrochloric acid.

[0010] As a preferred solution, the organic acid is oxalic acid.

[0011] As a preferred solution, the oxidant is at least one of ferric nitrate, ammonium persulfate, hydrogen peroxide, potassium iodate and potassium persulfate.

[0012] As a preferred solution, the oxidant is ferric nitrate.

[0013] As a preferred solution, the complexing agent is at least one of EDTA, DTPA, EGTA, NTA, CDTA and TTHA.

[0014] As a preferred solution, the complexing agent is a combination of EDTA, DTPA and TTHA.

[0015] As a preferred solution, the mass ratio of EDTA, DTPA and TTHA is (4-5): (1-1.5): (0.2-0.4).

[0016] As a preferred solution, the mass ratio of EDTA, DTPA and TTHA is (4-4.5): (1-1.2): (0.2-0.3).

[0017] As a preferred solution, the auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether.

[0018] As a preferred solution, the mass ratio of the isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether is (3-4): (1.2-1.6): (0.2-0.3).

[0019] As a preferred solution, the mass ratio of the isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether is (3.4-3.8): (1.4-1.5): (0.2-0.25).

[0020] As a preferred solution, the hydroxyl value of the isomeric C12-C13 fatty alcohol polyoxyethylene ether is 150-200 mgKOH / g.

[0021] As a preferred solution, the hydroxyl value of the isomeric C12-C13 fatty alcohol polyoxyethylene ether is 180-195 mgKOH / g.

[0022] As a preferred solution, the HLB value of the phenethylphenol polyoxyethylene ether is 12-18.

[0023] As a preferred solution, the HLB value of the phenethylphenol polyoxyethylene ether is 16-18.

[0024] As a preferred solution, the weight average molecular weight of the block polyether is 8000 to 12000 Da.

[0025] As a preferred solution, the weight average molecular weight of the block polyether is 10000-11000 Da.

[0026] In the present application, by adopting the combination formula of the above-mentioned auxiliary agents, the etching efficiency of the thin tin etching solution can be effectively improved, while the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation can be effectively avoided, the load capacity can be increased and good self-stability can be maintained. The joint action of the above-mentioned auxiliary agents can form a film layer system formed by superposition of different auxiliary phases in the etching solution system. The emergence of this system can not only effectively encapsulate and block the excessive free collision of active ingredients in the system during storage, reduce the probability of mutual contact, prevent the aggregation of insoluble particles, and avoid particle deposition, thereby obtaining excellent stability. On the other hand, the combination of the above-mentioned specific condition additives can fully utilize their film layer effect to form a good film layer effect on the etching surface, and can more easily penetrate into the fine structure of the metal surface and improve the rheological properties of the system, making the system and the etching process more stable. Finally, the film layer effect provides a good orderly carrying effect for the etching surface, avoiding the contact of too many active molecules per unit area with the etching surface, and thus effectively avoiding the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation of the etching solution during etching. Moreover, its higher film layer retention can greatly improve the system's preservation effect on the loaded ions, and in the process of reducing the free state, greatly increase its upper load limit.

[0027] As a preferred solution, the protective agent is at least one of benzotriazole, methylbenzotriazole, mercaptobenzothiazole, sodium stearate and imidazoline.

[0028] As a preferred solution, the protective agent is benzotriazole.

[0029] As a preferred solution, the copper protecting agent is at least one of zinc diethyl dithiocarbamate, 8-hydroxyquinoline, thiourea and 2-mercaptobenzimidazole.

[0030] As a preferred solution, the copper protecting agent is 8-hydroxyquinoline.

[0031] As a preferred solution, the stabilizer is at least one of polyvinyl pyrrolidone, polyacrylic acid and polyethylene oxide.

[0032] As a preferred solution, the stabilizer is a combination of polyvinyl pyrrolidone and polyethylene oxide.

[0033] As a preferred solution, the mass ratio of polyvinyl pyrrolidone to polyethylene oxide is (3-3.5): (0.6-1).

[0034] As a preferred solution, the carboxyl compound is a combination of malonic acid, adipic acid and citric acid.

[0035] As a preferred solution, the mass ratio of malonic acid, adipic acid and citric acid is (5-6): (2-3): (4-4.5).

[0036] As a preferred solution, the mass ratio of malonic acid, adipic acid and citric acid is 5.5:2.5:4.2.

[0037] As a preferred solution, in the main agent, the mass ratio of the inorganic acid, the organic acid, the oxidant, the auxiliary agent and the carboxyl compound is (4.5-5.5): (16-18): (6-7): (2.5-3): (3.5-4).

[0038] As a preferred solution, the mass ratio of the auxiliary agent: inorganic acid, organic acid, oxidant and carboxyl compound is (7-7.5): (11-12.5): (2.2-3): (1.1-1.5).

[0039] The second aspect of the present application provides a method for preparing the above-mentioned circuit board thin tin etching solution, which specifically includes the following steps: S1: adding the raw materials required for the main agent and the auxiliary agent into different mixing containers respectively, stirring at 35-45°C and 60-100rpm for 40-60min to obtain the main agent and the auxiliary agent; S2: when using, adding the auxiliary agent to the main agent according to the concentration of the loaded tin ions.

[0040] The beneficial effects of this application are:

[0041] 1. The thin tin etching solution for circuit boards provided in the present application not only has excellent etching accuracy and good etching effect, avoids the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation, but also has extremely high loading capacity and self-stability, meeting the performance requirements of the existing circuit board manufacturing field for the existing thin tin etching solution.

[0042] 2. A circuit board thin tin etching solution provided in the present application adopts a combination of composite additives, which can effectively improve the etching efficiency of the thin tin etching solution while effectively avoiding the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation, thereby increasing its own load capacity and maintaining good self-stability. The combined action of the above-mentioned additives can form a film layer system in the etching solution system formed by the superposition of different additive phases. The emergence of this system can not only effectively wrap and block the excessive free collision of active ingredients in the system during storage, but also reduce the probability of mutual contact, prevent the aggregation of insoluble particles, and avoid particle deposition, thereby obtaining excellent stability.

[0043] 3. A circuit board thin tin etching solution provided in the present application adopts a combination of composite additives, which can fully utilize its film layer effect to form a good film layer effect on the etching surface, and can more easily penetrate into the fine structure of the metal surface and improve the rheological properties of the system, making the system and the etching process more stable. Finally, the film layer effect provides a good orderly carrying effect for the etching surface, avoiding the contact of too many active molecules per unit area with the etching surface, and thus effectively avoiding the occurrence of chamfering, tailing, tin dissolution and tin surface oxidation of the etching solution during etching. Moreover, its higher film layer retention can greatly improve the system's preservation effect on the loaded ions, and in the process of reducing the free state, greatly increase its load upper limit. DETAILED DESCRIPTION

[0044] The following will further explain and demonstrate the technical solutions in the above invention content of this application in the form of specific implementation schemes. The following embodiments are only practical examples used to illustrate and explain the contents of the technical solutions in the specification, and should not limit the scope of the claims to be protected by this application. All technical products based on the technical solutions described in the invention content of this application should be included in the scope to be protected by this application.

[0045] In the following examples, unless otherwise specified, the raw materials are all commercially available products, or can be prepared by methods well known to those skilled in the art.

[0046] Example 1

[0047] Embodiment 1 A first aspect provides a circuit board thin tin etching solution, comprising a main agent and an auxiliary agent.

[0048] The main agent, calculated by mass percentage, includes: 4.8% inorganic acid, 17.2% organic acid, 6.6% oxidant, 2.1% complexing agent, 2.8% auxiliary agent, 2.9% protective agent, 0.8% copper protecting agent, 0.7% stabilizer, 3.8% carboxyl compound, and the balance is supplemented by deionized water.

[0049] The auxiliary agent, in terms of mass percentage, includes: 7.4% inorganic acid, 12.1% organic acid, 2.6% oxidant, 1.2% carboxyl compound, and the balance is made up of deionized water.

[0050] The dosage relationship between the main agent and the auxiliary agent is: the main agent is used for etching, and as the etching progresses, the auxiliary agent is added at a mass percentage of 0.22% of the main agent for every 200 ppm increase in the concentration of the loaded tin ions.

[0051] The inorganic acid is nitric acid; the organic acid is oxalic acid; and the oxidant is ferric nitrate.

[0052] The complexing agent is a combination of EDTA, DTPA and TTHA, and the mass ratio of the three is 4.2:1.1:0.2.

[0053] The auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether, and the mass ratio of the three is 3.5:1.4:0.22.

[0054] The isomeric C12-C13 fatty alcohol polyoxyethylene ether has a hydroxyl value of 190 mgKOH / g and was purchased from the E-1302 model product sold by Hai'an Guoyun Chemical Company in China.

[0055] The HLB value of phenylethylphenol polyoxyethylene ether is 17, and the corresponding HLB value product was purchased from Haian Guoyun Chemical Company in China.

[0056] The weight average molecular weight of the block polyether is 11000 Da, and the epoxy block polyether L series with the corresponding weight average molecular weight is purchased from BASF, Germany.

[0057] The protective agent is benzotriazole; the copper protecting agent is 8-hydroxyquinoline.

[0058] The stabilizer is a composition of polyvinyl pyrrolidone K90 and polyethylene oxide, and the mass ratio of the two is 3.4:0.8. Polyethylene oxide is purchased from a standard industrial grade product sold by Hubei Huada Fine Chemical Co., Ltd., China.

[0059] The carboxyl compound is a composition of malonic acid, adipic acid and citric acid, and the mass ratio of the three is 5.5:2.5:4.2.

[0060] The second aspect of the present embodiment provides a method for preparing the above-mentioned circuit board thin tin etching solution, which specifically includes the following steps: S1: adding the raw materials required for the main agent and the auxiliary agent into different mixing containers respectively, stirring at 40°C and 80rpm for 55 minutes to obtain the main agent and the auxiliary agent; S2: when using, adding the auxiliary agent to the main agent according to the concentration of the loaded tin ions.

[0061] Example 2

[0062] The specific implementation of this embodiment is basically the same as that of Embodiment 1, except that the circuit board thin tin etching solution includes a main agent and an auxiliary agent.

[0063] The main agent, in terms of mass percentage, includes the following raw materials: 5.4% inorganic acid, 16.2% organic acid, 6% oxidant, 2.1% complexing agent, 2.5% auxiliary agent, 2.9% protective agent, 0.8% copper protecting agent, 0.7% stabilizer, 3.5% carboxyl compound, and the balance is supplemented by deionized water.

[0064] The auxiliary agent, in terms of mass percentage, is composed of 7% inorganic acid, 11% organic acid, 2.2% oxidant, 1.5% carboxyl compound, and the balance is supplemented by deionized water.

[0065] The complexing agent is a combination of EDTA, DTPA and TTHA, and the mass ratio of the three is 5:1:0.4.

[0066] The auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether, and the mass ratio of the three is 3:1.6:0.3.

[0067] The stabilizer is a composition of polyvinyl pyrrolidone K90 and polyethylene oxide, and the mass ratio of the two is 3:1.

[0068] The carboxyl compound is a composition of malonic acid, adipic acid and citric acid, and the mass ratio of the three is 6:2:4.5.

[0069] Example 3

[0070] The specific implementation of this embodiment is basically the same as that of Embodiment 1, except that the circuit board thin tin etching solution includes a main agent and an auxiliary agent.

[0071] The main agent, calculated by mass percentage, includes the following raw materials: 4.5% inorganic acid, 17.8% organic acid, 7% oxidant, 2.1% complexing agent, 3% auxiliary agent, 2.9% protective agent, 0.8% copper protecting agent, 0.7% stabilizer, 4% carboxyl compound, and the balance is supplemented by deionized water.

[0072] The auxiliary agent, calculated by mass percentage, includes: 7.5% inorganic acid, 12.5% ​​organic acid, 3% oxidant, 1.1% carboxyl compound, and the balance is supplemented by deionized water.

[0073] The complexing agent is a combination of EDTA, DTPA and TTHA, and the mass ratio of the three is 4:1.5:0.2.

[0074] The auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether, and the mass ratio of the three is 4:1.2:0.2.

[0075] The stabilizer is a composition of polyvinyl pyrrolidone K90 and polyethylene oxide, and the mass ratio of the two is 3.5:0.6.

[0076] The carboxyl compound is a composition of malonic acid, adipic acid and citric acid, and the mass ratio of the three is 5:3:4.

[0077] Comparative Example 1

[0078] The specific implementation method of this comparative example is basically the same as that of Example 1, except that: the main agent, in terms of mass percentage, the raw materials are: 5.5% inorganic acid, 18.5% organic acid, 6.6% oxidant, 2.1% complexing agent, 1.1% auxiliary agent, 2.9% protective agent, 0.8% copper protecting agent, 0.7% stabilizer, 1.6% carboxyl compound, and deionized water to make up the balance.

[0079] The auxiliary agent, calculated by mass percentage, includes: 7.4% inorganic acid, 12.1% organic acid, 2.6% oxidant, 0.4% carboxyl compound, and the balance is supplemented by deionized water.

[0080] Comparative Example 2

[0081] The specific implementation method of this comparative example is basically the same as that of Example 1, except that: the main agent, in terms of mass percentage, the raw materials are: 4.8% inorganic acid, 17.2% organic acid, 6.6% oxidant, 2.1% complexing agent, 4.5% auxiliary agent, 2.9% protective agent, 0.8% copper protecting agent, 0.7% stabilizer, 1.2% carboxyl compound, and the balance is supplemented by deionized water.

[0082] The auxiliary agent, calculated by mass percentage, includes: 7.4% inorganic acid, 12.1% organic acid, 2.6% oxidant, and the balance is made up of deionized water.

[0083] Comparative Example 3

[0084] The specific implementation of this comparative example is basically the same as that of Example 1, except that the carboxyl compound is a combination of malonic acid, adipic acid and citric acid, and the mass ratio of the three is 1:1:0.5.

[0085] Comparative Example 4

[0086] The specific implementation of this comparative example is basically the same as that of Example 1, except that the complexing agent is EDTA; the stabilizer is a composition of polyvinyl pyrrolidone K90 and polyethylene oxide, and the mass ratio of the two is 8:0.6.

[0087] Comparative Example 5

[0088] The specific implementation of this comparative example is basically the same as that of Example 1, except that the auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether, and the mass ratio of the three is 8:1:0.1.

[0089] Comparative Example 6

[0090] The specific implementation of this comparative example is basically the same as that of Example 1, except that the auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether, and the mass ratio of the three is 1:1.5:1.

[0091] Performance Evaluation

[0092] The etching solutions prepared in the embodiments and comparative examples were used for performance testing. The test target was a copper-based thin tin film circuit board with a copper thickness of 5000A, a tin thickness of 300A, an etching temperature of 35°C, and an etching time of 160 to 190 seconds.

[0093] After etching is completed, check whether there are chamfers and tailing phenomena. If there are, it is recorded as unqualified, otherwise it is qualified. 50 samples are tested in each group, and the qualified rate is recorded in Table 1.

[0094] After etching is completed, check whether there is tin dissolution and tin surface oxidation. If there is, it is recorded as unqualified, otherwise it is qualified. 50 samples are tested in each group, and the qualified rate is recorded in Table 1.

[0095] The highest tin loading during the etching process was recorded as an integer in units of 1000 and the results were recorded in Table 1.

[0096] The CD-loss (single side, μm) in the etching results was recorded, and the average value of 10 tests was recorded in Table 1.

[0097] The etching solutions prepared in the embodiments and comparative examples were subjected to stability tests. The test environment temperature was 60±2°C and the relative humidity was 75±2%. The etching solutions were kept at a constant temperature and humidity for 72 hours. After completion, the etching solutions were taken out to observe whether stratification, segregation, and suspended impurities occurred. If so, they were recorded as unqualified, otherwise, they were qualified. 50 samples were tested in each group, and the qualified rate was recorded in Table 1.

[0098] Table 1 Performance test results

[0099]

[0100]

[0101] It can be seen from the embodiments and comparative examples of the present application and the data results in Table 1 that embodiments 1 and 2 of the present application have obvious advantages over comparative examples 1 to 6 in terms of etching effect, anti-chamfering and tailing effect, anti-tin dissolution and tin surface oxidation effect, etching accuracy and self-stability. This is mainly due to the combined effect of the functional additives specified in the present application and other matching technical solutions. Comparative examples 1 to 6 did not fully adopt the technical solutions specified in the present application, resulting in obvious disadvantages in the above-mentioned performance tests. This further proves the necessity of the technical solutions specified in the present application for the technical effects of the present application and solving technical problems.

Claims

1. A circuit board thin tin etching solution, characterized in that: The invention comprises a main agent and an auxiliary agent; the main agent, in terms of mass percentage, comprises the following raw materials: 4-6% inorganic acid, 15-20% organic acid, 5-8% oxidant, 1-3% complexing agent, 2-3.5% auxiliary agent, 2.5-4% protective agent, 0.5-1% copper protecting agent, 0.5-1.5% stabilizer, 3-5% carboxyl compound, and the balance is supplemented by deionized water; The auxiliary agent, in terms of mass percentage, comprises: 6-8% inorganic acid, 10-14% organic acid, 2-4% oxidant, 1-3% carboxyl compound, and the balance is supplemented by deionized water; The dosage relationship between the main agent and the auxiliary agent is: during etching, the main agent is used for etching, and as the concentration of the loaded tin ions increases by 200ppm, 0.2 to 0.25% of the main agent mass percentage of the auxiliary agent is added; The inorganic acid is at least one of nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid and hydrofluoric acid; The organic acid is oxalic acid; The auxiliary agent is a composition of isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether; The mass ratio of the isomeric C12-C13 fatty alcohol polyoxyethylene ether, phenethylphenol polyoxyethylene ether and block polyether is (3-4): (1.2-1.6): (0.2-0.3); The stabilizer is a composition of polyvinyl pyrrolidone and polyethylene oxide; The mass ratio of polyvinyl pyrrolidone to polyethylene oxide is (3-3.5): (0.6-1); The carboxyl compound is a combination of malonic acid, adipic acid and citric acid; The mass ratio of malonic acid, adipic acid and citric acid is (5-6): (2-3): (4-4.5).

2. The circuit board thin tin etching solution according to claim 1, characterized in that: In the main agent, the mass ratio of inorganic acid, organic acid, oxidant, auxiliary agent and carboxyl compound is (4.5-5.5): (16-18): (6-7): (2.5-3): (3.5-4).

3. The circuit board thin tin etching solution according to claim 2, characterized in that: The complexing agent is at least one of EDTA, DTPA, EGTA, NTA, CDTA and TTHA.

4. The circuit board thin tin etching solution according to claim 3, characterized in that: The complexing agent is a composition of EDTA, DTPA and TTHA; the mass ratio of EDTA, DTPA and TTHA is (4-5): (1-1.5): (0.2-0.4).

5. The circuit board thin tin etching solution according to claim 4, characterized in that: The hydroxyl value of the isomeric C12-C13 fatty alcohol polyoxyethylene ether is 150-200 mgKOH / g.

6. The circuit board thin tin etching solution according to claim 5, characterized in that: The HLB value of the phenethylphenol polyoxyethylene ether is 12-18.

7. The circuit board thin tin etching solution according to claim 6, characterized in that: The weight average molecular weight of the block polyether is 8000-12000 Da.

8. The circuit board thin tin etching solution according to claim 7, characterized in that: The protective agent is at least one of benzotriazole, methylbenzotriazole, mercaptobenzothiazole, sodium stearate and imidazoline.

9. The circuit board thin tin etching solution according to claim 8, characterized in that: The copper protecting agent is at least one of zinc diethyl dithiocarbamate, 8-hydroxyquinoline, thiourea and 2-mercaptobenzimidazole.

10. A method for preparing a circuit board thin tin etching solution according to any one of claims 1 to 9, characterized in that: The specific steps include: S1: Add the raw materials required for the main agent and the auxiliary agent into different mixing containers respectively, stir at 35-45°C and 60-100 rpm for 40-60 min to obtain the main agent and the auxiliary agent; S2: When using, add the auxiliary agent to the main agent according to the concentration of the loaded tin ions.

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