A PCB tin layer anti-corrosion soldering protective agent and preparation method thereof

Abstract

The present invention relates to a kind of PCB tin layer anticorrosive soldering protective agent and preparation method thereof, the raw material of the protective agent includes a film former, corrosion inhibitor, organic acid and auxiliary agent in a mass ratio of (0.02-0.04): (0.2-0.6): (0.1-0.3): (0.8-1.4), and other components; the preparation method is to press a formula, and a film former, corrosion inhibitor, a film former solubilizer, an organic acid, an auxiliary agent are added to water to obtain a PCB tin layer anticorrosive soldering protective agent. Compared with prior art, the present invention can provide a longer anticorrosive protection to the tin layer while ensuring the tin layer welding effect. In addition, the raw material is common and the amount used is small, the film former has biodegradability, is economically practical, green and environmentally friendly, and has obvious advantages in industrial application.

Description

Technical Field

[0001] The invention relates to the technical field of soldering protectants, and in particular to a PCB tin layer anti-corrosion soldering protectant and a preparation method thereof. Background Art

[0002] Tin coatings possess numerous excellent properties and are widely used as functional coatings in industries such as integrated circuits, aerospace, and automotive manufacturing. As applications continue to diversify and become more sophisticated, the functional reliability of tin coatings is increasingly demanded. However, their performance is susceptible to degradation due to production and environmental factors, manifesting itself in surface oxidation discoloration and reduced solderability. These defects not only hinder device soldering but also accelerate product failure and even lead to safety incidents.

[0003] To improve the reliability of the tin coating's surface properties, researchers have modified and protected the tin coating by improving the electroplating process and adding post-processing steps. For example, Patent CN115558963A achieves a low-porosity, highly bonded coating through innovative electroplating procedures. During post-plating processing, passivation techniques are used to form a phase film or adsorption film on the tin coating's surface, as described in Patent CN115896900A. However, evidence suggests that when the tin coating is used in soldering scenarios, the presence of solder resist in the surface passivation film seriously affects the functional application of the tin coating. Consequently, researchers have introduced copper protectants (azole OSPs) to protect and improve the reliability of the tin coating, as described in Patent CN110965064B. However, OSPs have a short shelf life and a short effective protection period for the tin surface, as described in Patent CN110564244A, making them unable to fundamentally address the reliability issues associated with the functional application of the tin coating. Therefore, improving the reliability of tin coating applications has become a challenge that must be addressed. Summary of the Invention

[0004] The present invention aims to address defects such as discoloration of the tin layer surface and decreased soldering performance while also overcoming the short protection time and low application reliability of the prior art tin layer. The invention provides a PCB tin layer anti-corrosion soldering agent and its preparation method. The agent provides long-term corrosion protection for the tin layer while ensuring soldering performance.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] One of the purposes of the present invention is to provide a PCB tin layer anti-corrosion soldering protective agent. The raw materials of the protective agent include a film-forming material, a corrosion inhibitor, an organic acid and an auxiliary agent in a mass ratio of (0.02-0.04):(0.2-0.6):(0.1-0.3):(0.8-1.4), and other components.

[0007] Furthermore, the raw materials of the protective agent are composed of the following components by weight: 0.02-0.04 wt% of film former, 0.2-0.6 wt% of corrosion inhibitor, 3 wt% of film former dissolving agent, 0.1-0.3 wt% of organic acid and 0.8-1.4 wt% of auxiliary agent, with the remainder being water. Preferably, the water is deionized water.

[0008] Furthermore, the raw materials of the protective agent are composed of the following components in mass fractions: 0.03wt% of film former, 0.4wt% of corrosion inhibitor, 3wt% of film former dissolving agent, 0.2wt% of organic acid, 1.1wt% of auxiliary agent and 95.27wt% of water.

[0009] Furthermore, the film-forming material is a natural resin of a tricyclic phenanthrene skeleton monocarboxylic acid containing two double bonds.

[0010] Furthermore, the film-forming material is rosin.

[0011] Furthermore, the corrosion inhibitor is 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA).

[0012] Furthermore, the film-forming material dissolving agent is styrene.

[0013] Furthermore, the organic acid is ascorbic acid.

[0014] Furthermore, the auxiliary agent includes triethanolamine and sodium dodecylbenzenesulfonate, preferably, consists of triethanolamine and sodium dodecylbenzenesulfonate, and the mass ratio between the two is 8:3.

[0015] The second object of the present invention is to provide a method for preparing the PCB tin layer anti-corrosion soldering protective agent as described above, which is characterized by comprising the following steps: adding a film former, a corrosion inhibitor, a film former dissolving agent, an organic acid, and an additive to water according to a formula to obtain the PCB tin layer anti-corrosion soldering protective agent.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] (1) The present invention provides a PCB tin layer anti-corrosion soldering protective agent. The rosin in the protective agent not only has a soldering effect, but also adheres to the surface of the tin layer in liquid form after being dissolved by styrene. It can also cooperate with ascorbic acid to remove metal oxides on the surface of the tin layer to expose the pure tin layer. Ascorbic acid can not only inhibit the discoloration of rosin, but its own carboxyl group can also be deoxidized to carbonyl, which reacts with the amino group in the auxiliary agent triethanolamine to generate Schiff Base with an imine group (-C=N-). The Schiff Base and the corrosion inhibitor APBIA will form a film covering the surface of the tin layer in the form of complexed tin ions. The protective film is formed by the mutual cooperation between the components to ensure that the protective agent can provide a longer-term anti-corrosion protection for the tin layer while ensuring the soldering effect of the tin layer.

[0018] (2) The film-forming material used in the present invention is biodegradable, and its components are stable in both normal and high temperature environments, which can improve the storage stability of the protective agent. In addition, the raw materials are common and the amount used is small, making it economical, practical, green and environmentally friendly, and having obvious advantages in industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The soldering effect diagram of Example 1 and the blank sample after 20h of wet heat aging

[0020] Figure 2 Soldering effect diagram of Example 1 and blank sample after dry heat aging for 15 hours

[0021] Figure 3 The appearance of Example 1 and the blank sample in neutral salt spray for 96 hours DETAILED DESCRIPTION

[0022] The present invention is described in detail below with reference to the accompanying drawings and specific examples. This example is implemented based on the technical solution of the present invention, and provides detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following examples. In the following examples, unless otherwise specified, the raw materials or processing techniques used are conventional commercially available raw materials or conventional processing techniques in the field.

[0023] In the following embodiments and comparative examples, the sample parameters used are fresh bright tin-plated sheets with C194 copper-iron alloy as the base, a 1 μm middle nickel-plated layer, and a 1.2 μm tin-plated layer.

[0024] A method for implementing a PCB tin layer anti-corrosion soldering protective agent comprises the following steps: a sample is alkali washed, water washed, acid washed, water washed, immersed in the protective agent, taken out and dried, and the protective film layer is obtained on the surface of the sample.

[0025] The evaluation methods for the protective agent include:

[0026] After dry heat aging at 175°C, the sample is taken out and placed vertically in a soldering furnace for tinning. Under the premise of a qualified tinning rate, the longer the dry heat aging time, the better the effect of the protective agent (according to the grid method, the tinned part of the sample is 100%, and the tinning rate reaches 95% to be qualified, that is, the protective agent is effective, otherwise it is ineffective);

[0027] After the sample is aged at 85℃ and 85% RH, it is taken out and placed vertically in the soldering furnace for tinning. Under the premise of qualified tinning rate, the longer the aging time, the better the effect of the protective agent. (Based on the grid method, the tinned part of the sample is 100%, and the tinning rate reaches 95% to be qualified, that is, the protective agent is effective; otherwise, it is ineffective).

[0028] According to GB / T 10125-2021, set the spray mode to continuous. After the neutral salt spray, remove the sample and observe the surface rust spots. The longer the rust spots appear, the better the protective agent is.

[0029] In the following comparative examples and examples, the film-forming agent is rosin; the corrosion inhibitor is 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA); the film-forming agent dissolving agent is styrene; and the organic acid is ascorbic acid. The additive is composed of triethanolamine and sodium dodecylbenzenesulfonate in a mass ratio of 8:3.

[0030] The inventors used a natural resin of a tricyclic phenanthrene skeleton monocarboxylic acid containing two double bonds as a film-forming material. The natural resin itself has the effects of corrosion resistance and fluxing, is not easily corroded and oxidized by the environment, and can remove oxides under heating. The R group is C 19 H 29 , the reaction formula is:

[0031] SnO2+4RCOOH→Sn(RCOO)4+2H2O ①

[0032] SnO+2RCOOH→Sn(RCOO)2+H2O ②

[0033] The film-forming dissolving agent can completely dissolve the natural resin under sufficient stirring, turning it from a solid into a small molecule soluble in water. In addition, the ascorbic acid in the component provides a carboxyl group, which is deoxygenated to a carbonyl group. It can undergo a condensation reaction with the amine group in the auxiliary agent triethanolamine to form a Schiff Base with an imine group (-C=N-). Since the protective agent is alkaline and the Schiff Base contains an electron-rich imine double bond, it can stably coordinate with Sn ions. In addition, APBIA can also coordinate with Sn ions, both of which can form a stable protective film to prevent further corrosion of the metal. The coordination expression is as follows:

[0034] SnO2+4Schiff Base→Sn(R-Salen)4+2H2O ①

[0035] SnO+2Schiff Base→Sn(R-Salen)2+H2O ②

[0036] 2APBIA+SnO→Sn(APBIA)2+H2O ③

[0037] 4APBIA+SnO2→Sn(APBIA)4+2H2O ④

[0038] Through emulsification and dispersion of additives, the protective film is evenly applied to the surface of the tin layer. Simultaneously, ascorbic acid inhibits the yellowing discoloration of the rosin on the surface of the tin layer. Through the interaction between the components, the high-temperature resistant film completely covers the tin layer, inhibiting or slowing the growth of tin whiskers caused by stress within the tin layer. This achieves corrosion protection, soldering, and whisker growth inhibition, thereby reducing the failure of the solderable tin layer caused by quality defects caused by the process and production environment or improper storage during the tin plating process.

[0039] Example 1

[0040] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.4wt% of APBIA, 0.2wt% of organic acid, and 1.1wt% of additives.

[0041] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0042] Example 2

[0043] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.02 wt% of rosin, 0.4 wt% of APBIA, 0.2 wt% of organic acid, and 1.1 wt% of additives.

[0044] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0045] Example 3

[0046] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.04wt% of rosin, 0.4wt% of APBIA, 0.2wt% of organic acid, and 1.1wt% of additives.

[0047] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0048] Example 4

[0049] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.2wt% of APBIA, 0.2wt% of organic acid, and 1.1wt% of additives.

[0050] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0051] Example 5

[0052] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.6wt% of APBIA, 0.2wt% of organic acid, and 1.1wt% of additives.

[0053] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0054] Example 6

[0055] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.4wt% of APBIA, 0.1wt% of organic acid, and 1.1wt% of additives.

[0056] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0057] Example 7

[0058] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.4wt% of APBIA, 0.3wt% of organic acid, and 1.1wt% of additives.

[0059] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0060] Example 8

[0061] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then APBIA, organic acid, and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03wt% of rosin, 0.4wt% of APBIA, 0.2wt% of organic acid, and 0.8wt% of additives.

[0062] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The samples showed effective protection for 20 hours under damp heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. See Table 1 for the specific results.

[0063] Example 9

[0064] Rosin was added to styrene to obtain a rosin solution, which was then added to deionized water while stirring. APBIA, an organic acid, and an additive were then added while continuing to stir to obtain a protective agent containing 0.03wt% rosin, 0.4wt% APBIA, 0.2wt% organic acid, and 1.4wt% additive. The above-mentioned samples were immersed in the protective agent, removed from the solution, dried, and then subjected to dry heat, wet heat, and salt spray tests. The samples showed effective protection for 20 hours under wet heat aging, 15 hours under dry heat aging, and 96 hours under neutral salt spray. The results are shown in Table 1.

[0065] Comparative Example 1

[0066] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring to obtain a protective agent. The rosin content in the protective agent was 0.03 wt%.

[0067] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection for 9 hours under damp heat aging, 3 hours under dry heat aging, and 24 hours under neutral salt spray.

[0068] Comparative Example 2

[0069] APBIA was added to deionized water while stirring to obtain a protective agent, wherein the content of APBIA in the protective agent was 0.4 wt %.

[0070] The above samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples were effectively protected for 8 hours under damp heat aging, 4 hours under dry heat aging, and 24 hours under neutral salt spray.

[0071] Comparative Example 3

[0072] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then an organic acid was added while continuing to stir to obtain a protective agent. The protective agent contained 0.03 wt% of rosin and 0.2 wt% of organic acid.

[0073] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection time of 11 hours under damp heat aging, 4 hours under dry heat aging, and 24 hours under neutral salt spray.

[0074] Comparative Example 4

[0075] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then an auxiliary agent was added while continuing to stir to obtain a protective agent. The protective agent contained 0.03 wt% of rosin and 1.1 wt% of auxiliary agent.

[0076] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection for 13 hours under damp heat aging, 6 hours under dry heat aging, and 24 hours under neutral salt spray.

[0077] Comparative Example 5

[0078] APBIA was added to deionized water while stirring, and then an organic acid was added while continuing to stir to obtain a protective agent. The content of APBIA in the protective agent was 0.4 wt % and the content of the organic acid was 0.2 wt %.

[0079] The above samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples were effectively protected for 12 hours under damp heat aging, 6 hours under dry heat aging, and 48 hours under neutral salt spray.

[0080] Comparative Example 6

[0081] APBIA was added to deionized water while stirring, and then an auxiliary agent was added while continuing to stir to obtain a protective agent. The content of APBIA in the protective agent was 0.4 wt %, and the content of the auxiliary agent was 1.1 wt %.

[0082] The above samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples were effectively protected for 13 hours under damp heat aging, 8 hours under dry heat aging, and 48 hours under neutral salt spray.

[0083] Comparative Example 7

[0084] The organic acid is added to deionized water while stirring, and then the auxiliary agent is added while continuing to stir to obtain a protective agent. The organic acid content in the protective agent is 0.2 wt % and the auxiliary agent content is 1.1 wt %.

[0085] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection for 11 hours under damp heat aging, 7 hours under dry heat aging, and 24 hours under neutral salt spray.

[0086] Comparative Example 8

[0087] After adding rosin to styrene to obtain a rosin solution, the solution was added to deionized water while stirring, and then organic acid and additives were added while continuing to stir to obtain a protective agent. The protective agent contained 0.03 wt% of rosin, 0.2 wt% of organic acid, and 1.1 wt% of additives.

[0088] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection for 14 hours under damp heat aging, 10 hours under dry heat aging, and 72 hours under neutral salt spray.

[0089] Comparative Example 9

[0090] APBIA was added to deionized water while stirring, and then organic acid and auxiliary agent were added while stirring to obtain a protective agent. The protective agent contained 0.4 wt % of APBIA, 0.2 wt % of organic acid and 1.1 wt % of auxiliary agent.

[0091] The samples were immersed in the protective agent, removed and dried, and then subjected to dry heat, damp heat, and salt spray tests. The specific results are shown in Table 1. The samples showed effective protection time of 16 hours under damp heat aging, 12 hours under dry heat aging, and 72 hours under neutral salt spray.

[0092] As shown in Table 1, in Examples 1-9, the rosin in the protective agent not only acts as a flux but also adheres to the tin layer surface in liquid form after being dissolved in styrene. It also synergizes with ascorbic acid to remove metal oxides from the tin layer surface, exposing the pure tin layer. Ascorbic acid not only inhibits discoloration of the rosin, but its carboxyl groups can also be deoxygenated to carbonyl groups, which react with the amine groups in the auxiliary agent triethanolamine to form a Schiff Base with an imine group (-C=N-). Both the Schiff Base and the corrosion inhibitor APBIA complex the tin ions to form a film covering the tin layer surface. The protective film is formed through the interaction of the components. Variations in component concentration within a reasonable range have little impact on the tested sample results. The rosin content in the protective agent is 0.02-0.04wt%, the APBIA content is 0.2-0.6wt%, the organic acid content is 0.1-0.3wt%, and the additive content is 0.8-1.4wt%. The effective protection time of the sample under the wet heat aging state is 20h, the effective protection time under the dry heat aging state is 15h, and the effective protection time under the neutral salt spray state is 96h. Figure 1-3 .

[0093] Compared with Example 1, the protection time of the sample of Comparative Example 1 in dry heat, humid heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 1 lacks APBIA, organic acid, and additives, and rosin alone cannot completely remove surface oxides. In addition, rosin itself is prone to yellowing and discoloration, and its wetting uniformity is insufficient.

[0094] Compared with Example 1, the protection time of the sample of Comparative Example 2 in dry heat, wet heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 2 lacks rosin, organic acid, and additives. APBIA alone cannot remove the surface oxide of the tin layer and cannot complex with the tin ions.

[0095] Compared with Example 1, the protection time of the sample of Comparative Example 3 in dry heat, wet heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 3 lacks APBIA, additives, and complexes, and cannot complex with tin ions to form a film.

[0096] Compared with Example 1, the protection time of the sample of Comparative Example 4 in dry heat, wet heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 4 lacks APBIA and organic acid, and cannot completely remove oxides. It also lacks complexes and cannot form a film with tin ions.

[0097] Compared with Example 1, the protection time of the sample of Comparative Example 5 in dry heat, wet heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 5 lacks rosin and additives, cannot completely remove oxides, and lacks wetting and uniformity.

[0098] Compared with Example 1, the protection time of the sample of Comparative Example 6 in dry heat, wet heat, and salt spray environments is not as good as that of Example 1. This is because Comparative Example 6 lacks rosin and organic acid, and APBIA alone cannot remove the surface oxide of the tin layer and cannot complex with the tin ions.

[0099] Compared with Example 1, the protection time of the sample of Comparative Example 7 in dry heat, wet heat and salt spray environments is not as good as that of Example 1. This is because Comparative Example 7 lacks rosin, APBIA, film-forming materials and complexes, and cannot form a protective film.

[0100] Compared with Example 1, the protection time of the sample of Comparative Example 8 in dry heat, wet heat and salt spray environments is not as good as that of Example 1. This is because there is a lack of APBIA and a complex in the sample, which cannot form a complex with tin ions to form a membrane.

[0101] Compared with Example 1, the protection time of the sample of Comparative Example 9 in dry heat, wet heat and salt spray environments is not as good as that of Example 1. This is because there is a lack of rosin and the main film-forming material in the sample.

[0102] Table 1 Protection of the samples in the blank control, Examples 1-9 and Comparative Examples 1-9

[0103]

[0104]

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other manner. Any person skilled in the art may utilize the above-disclosed technical content to modify or modify the present invention into equivalent embodiments. However, any simple modifications, equivalent variations, and modifications to the above embodiments that do not depart from the technical content of the present invention and are based on the technical essence of the present invention remain within the scope of protection of the present invention.

Claims

1. A PCB tin layer anti-corrosion soldering protective agent, characterized in that: The raw materials of the protective agent are composed of the following components in mass fractions: 0.02-0.04wt% of a film former, 0.2-0.6wt% of a corrosion inhibitor, 3wt% of a film former dissolving agent, 0.1-0.3wt% of an organic acid, 0.8-1.4wt% of an auxiliary agent, and the rest being water; The film-forming material is rosin; The corrosion inhibitor is 2-(4-aminophenyl)-5-aminobenzimidazole; The film-forming material dissolving agent is styrene; The organic acid is ascorbic acid; The auxiliary agents include triethanolamine and sodium dodecylbenzenesulfonate.

2. A PCB tin layer anti-corrosion soldering protective agent according to claim 1, characterized in that, The raw materials of the protective agent are composed of the following components in mass fractions: 0.03wt% of a film former, 0.4wt% of a corrosion inhibitor, 3wt% of a film former dissolving agent, 0.2wt% of an organic acid, 1.1wt% of an auxiliary agent and 95.27wt% of water.

3. A method for preparing a PCB tin layer anticorrosion soldering protective agent according to any one of claims 1 to 2, characterized in that: The method comprises the following steps: adding a film-forming material, a corrosion inhibitor, a film-forming material dissolving agent, an organic acid and an additive into water according to a formula to obtain a PCB tin layer anti-corrosion and flux protection agent.

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