A corrosion inhibitor for preventing corrosion discoloration of printed board assemblies during alkaline cleaning and a method for preparing the same

Abstract

The application provides a corrosion inhibitor for preventing corrosion discoloration of a printed board assembly during an alkaline cleaning process and a preparation method thereof. The corrosion inhibitor for preventing corrosion discoloration of a printed board assembly during an alkaline cleaning process comprises the following components in percentage by mass: 20-25% of sodium silicate, 5% of ammonium lactate, 1-3% of phosphate, 1-2% of organic amine, 2x10 ‑3 -5x10 ‑3 % of 5-methyl benzotriazole, 0.1% of fatty acid methyl ester ethoxylate sulfonate, and the rest is deionized water. The corrosion inhibitor for preventing corrosion discoloration of a printed board assembly during an alkaline cleaning process can prevent the tin-lead alloy solder joint on the printed circuit assembly from being easily corroded and oxidized during the alkaline cleaning process after welding.

Description

Technical Field

[0001] This invention relates to the field of chemical technology, and in particular to a corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, and its preparation method. Background Technology

[0002] Printed circuit components are constructed from a wide range of electroplated metals and alloys, commonly including tin-lead alloys, copper alloys, aluminum alloys, nickel alloys, stainless steel, and silver and gold plating. High-reliability printed circuit components require cleaning to remove flux residues after assembly and soldering. However, alkaline cleaning solutions can cause corrosion reactions with different types of metals, the extent of which depends on the alkalinity of the cleaning solution's alkalinity source, the washing temperature, and the contact time. In particular, corrosion and discoloration of tin-lead solder joints are very common in S-Sn63Pb tin-lead solder (according to GB3131) used in military and aerospace applications under alkaline cleaning conditions.

[0003] The interaction between cleaning agents and these alloys can cause changes in appearance, most notably corrosion and discoloration of the metal surfaces. In alkaline cleaning processes for printed circuit board assemblies, the most common alloys exhibiting corrosion and discoloration are tin-lead alloys and aluminum alloys.

[0004] However, through research and patent searches, it was found that there are currently no domestic patents or relevant literature available for reference regarding alkaline cleaning corrosion inhibitors (also known as brighteners) for tin-lead solder alloys. High-reliability electronic components must be cleaned after soldering (with a large proportion of alkaline water-based cleaning solutions), but the problem of corrosion and discoloration of tin-lead solder alloys during alkaline cleaning is difficult to solve.

[0005] Therefore, it is necessary to provide a new, multi-purpose corrosion inhibitor that can simultaneously provide corrosion protection for tin-lead alloys, aluminum alloys, and copper alloys on printed circuit components, preventing corrosion and discoloration during alkaline cleaning processes. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a corrosion inhibitor and protective agent to prevent corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, particularly to prevent corrosion and discoloration of tin-lead alloy solder joints and corrosion and oxidation discoloration of metals such as aluminum alloys.

[0007] This invention provides a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following components by weight percentage: sodium silicate 20-25%, ammonium lactate 5%, phosphate 1-3%, organic amine 1-2%, and 5-methylbenzotriazole 2×10⁻⁶. -3 -5×10 -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

[0008] Preferably, the sodium silicate is sodium metasilicate pentahydrate or polyether organic disilicate.

[0009] Preferably, the phosphate is potassium pyrophosphate or sodium tripolyphosphate.

[0010] Preferably, the organic amine is diethylene glycolamine or triethanolamine.

[0011] The present invention also provides a method for preparing a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following steps:

[0012] S1, provides diethylene glycolamine and 5-methylbenzotriazole, with 5-methylbenzotriazole added to diethylene glycolamine;

[0013] S2 provides sodium metasilicate pentahydrate, potassium pyrophosphate and deionized water. Sodium metasilicate pentahydrate and potassium pyrophosphate are added to deionized water to dissolve them.

[0014] S3, add the mixture obtained in step S1 to the solution obtained in step S2, and let it stand for 5-8 minutes at a temperature of 20-30℃.

[0015] S4, providing ammonium lactate and fatty acid methyl ester ethoxylate sulfonate, adding ammonium lactate and fatty acid methyl ester ethoxylate sulfonate to the solution obtained in step S3;

[0016] S5. Provide a stirrer, add the solution obtained in step S4 into the stirrer and stir for 8-15 minutes until the solution remains transparent, thus preparing a corrosion inhibitor for preventing the printed circuit board assembly from corroding and discoloring during alkaline cleaning.

[0017] Preferably, in step S5, the stirrer is a mechanical stirrer or an ultrasonic stirrer.

[0018] Preferably, the corrosion inhibitor is added to an alkaline diluted cleaning solution at a concentration-to-volume ratio of 0.3-1%, and the printed circuit board assembly is cleaned using the cleaning solution to prevent metal corrosion and discoloration of the printed circuit board assembly.

[0019] Compared with related technologies, the corrosion inhibitor and protective agent and its preparation method provided by the present invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning have the following beneficial effects:

[0020] I. This invention provides a corrosion inhibitor and protective agent to prevent corrosion and discoloration of printed circuit board assemblies during alkaline cleaning. For soldered printed circuit board assemblies, the tin-lead alloy solder joints are prone to corrosion, oxidation, and discoloration during alkaline cleaning, and this agent provides corrosion inhibition and protection against corrosion.

[0021] Second, the corrosion inhibitor provided by this invention plays a role in inhibiting corrosion and preventing oxidation of other metal materials (aluminum alloy, copper alloy, nickel alloy, stainless steel, etc.) on printed circuit components.

[0022] Third, the corrosion inhibitor and protective agent provided by this invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning has good material compatibility with printed circuit boards and component assemblies. Attached Figure Description

[0023] Figure 1 This is a comparison chart showing the effects of related technologies and the addition of corrosion inhibitors on aluminum alloys after cleaning in alkaline cleaning solutions. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Literature review and research were conducted on metal corrosion inhibitors. Corrosion inhibitors are substances used on metal surfaces to provide protection. They adsorb onto the metal surface to form a monomolecular adsorption film, preventing the diffusion of water and dissolved oxygen from the water to the metal surface, thus inhibiting corrosion. Since the corrosion inhibition mechanism of corrosion inhibitors lies in film formation, the key to successful corrosion inhibition is to rapidly form a dense film (oxide film, precipitation film, adsorption film) on the metal surface.

[0026] There are many types of corrosion inhibitors. Based on their application mechanisms, these inhibitors were screened, selecting those that form precipitation films or adsorption films. Furthermore, they must be corrosion inhibitors suitable for use in alkaline environments. Five substances—benzotriazoles, phosphates, silicates, and ammonium salts—were selected to test their corrosion inhibition and protection effects on tin-lead alloys, copper, aluminum alloys, and nickel. The test conditions were alkaline solutions. Specific experimental procedures and data are shown in Table 1 below.

[0027] Table 1

[0028]

[0029]

[0030] Based on the experimental results in Table 1, further experiments were conducted at different concentrations of the effective chemical substances for tin-lead alloys to determine the appropriate concentration for use in alkaline cleaning processes. Specific experimental results are shown in Table 2.

[0031] Table 2

[0032]

[0033] Based on the above experimental results, it was preliminarily determined which type of corrosion inhibitor is effective against which type of metal alloy. The applicable concentration range was also determined. Corrosion inhibitors are generally used in combination for better corrosion inhibition; adding surfactants enhances the corrosion protection effect. Printed circuit board assemblies are composed of several alloys, so the corrosion inhibitors are not targeted at a single metal. Therefore, further compounding and testing are needed to determine the corrosion protection effect. Referring to the above experiments, the composition of the corrosion inhibitor was determined as follows:

[0034] A corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, characterized in that it comprises the following components by weight percentage: sodium silicate 20-25%, ammonium lactate 5%, phosphate 1-3%, organic amine 1-2%, and 5-methylbenzotriazole 2×10 -3 -5×10 -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

[0035] The sodium silicate is sodium metasilicate pentahydrate or polyether organic disilicate.

[0036] The phosphate is potassium pyrophosphate or sodium tripolyphosphate.

[0037] The organic amine is diethylene glycolamine or triethanolamine.

[0038] Sodium metasilicate pentahydrate and potassium pyrophosphate are inorganic precipitating corrosion inhibitors that inhibit the corrosion of metals such as tin-lead alloys and aluminum alloys. They function by forming a precipitate film on the metal surface. By inhibiting the anodic reaction of the metal, they enhance cathodic polarization by forming a precipitate film on the cathode, thereby preventing the formation of corrosion cells. Furthermore, sodium metasilicate pentahydrate and potassium pyrophosphate are also components in degreasing and cleaning formulations, thus having a good effect on cleaning flux after soldering of printed circuit board assemblies.

[0039] Among them, ammonium lactate, diethylene glycolamine, and 5-methylbenzotriazole belong to the adsorption-type corrosion inhibitors. Ammonium lactate has a corrosion inhibitory effect on tin-lead alloys. Diethylene glycolamine and 5-methylbenzotriazole have corrosion inhibitory effects on metals such as stainless steel and copper. They can adsorb onto the metal surface to form a monomolecular adsorption film, preventing the diffusion of water and dissolved oxygen from the water to the metal surface, thus playing a role in corrosion inhibition.

[0040] Fatty acid methyl ester ethoxylate sulfonate is an anionic surfactant with low foaming, emulsifying, and dispersing surface activities. Surfactants can improve the film-forming rate of corrosion inhibitors on metal surfaces, playing a synergistic role and enhancing the efficiency of corrosion inhibitors.

[0041] The combination of several chemical substances is important, and the concentration in practical applications is also crucial. If the concentration of sodium metasilicate pentahydrate is too high (greater than 3%), it will form a large amount of white precipitate on metal and non-metal surfaces.

[0042] The following specific embodiments illustrate in detail the corrosion inhibitor and protective agent provided by the present invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning.

[0043] Example 1

[0044] This invention provides a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following components by weight percentage: 20% sodium metasilicate pentahydrate, 5% ammonium lactate, 3% pyrophosphate, 1% diethylene glycolamine, and 5×10⁻⁶ methylbenzotriazole. -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

[0045] Based on Example 1, the method of use and performance of the corrosion inhibitor and protective agent of the present invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning are described in detail.

[0046] First, the printed circuit board (PCB) assemblies are assembled and welded according to the PCB assembly manufacturing process. In order to conduct multiple sets of data testing, the number of PCB assemblies used for testing is 4.

[0047] The manufacturing process for two of the printed circuit board (PCB) assemblies is as follows: PCB bare board - SMT (reflow soldering); the manufacturing process for the other two PCB assemblies is as follows: PCB bare board - manual soldering. The solder used is S-Sn63Pb tin-lead solder. Copper alloys, aluminum alloys, nickel alloys, stainless steel alloys, and other metal components with silver and gold plating were also prepared for verification.

[0048] The soldered printed circuit board assemblies, copper alloys, aluminum alloys, nickel alloys, and stainless steel alloys were subjected to immersion tests. Test conditions are shown in Table 3. After cleaning, the oxidation, corrosion, and discoloration of the tin-lead alloy solder joints and the metal materials listed in the test table were inspected. Data are shown in Table 4 below.

[0049] Table 3

[0050] Cleaning solution KYZEN-4625B 20％ 9.6 60℃ 30min Diethylene glycolamine CAS: 929-06-6 30％ 11.1 60℃ 30min

[0051] Table 4

[0052]

[0053] The experiment shows that in alkaline solutions, tin-lead solder alloys, copper, aluminum and other metals all exhibit oxidation, corrosion and discoloration.

[0054] The corrosion inhibitor used in Example 1 was added to the alkaline test solution at a concentration (volume ratio) of 0.3-1% of sodium metasilicate pentahydrate, based on multiple test results. The alkaline test solution with the added corrosion inhibitor was then visually evaluated using a 5x optical magnifying glass, as shown in Table 5 below.

[0055] Table 5

[0056]

[0057]

[0058] Test boards A, B, C, and D of the printed circuit board assembly were cleaned in a cleaning solution containing a corrosion inhibitor, and ionic residue tests were performed. The test conditions are shown in Table 6.

[0059] Table 6

[0060]

[0061] Table 7

[0062]

[0063] As can be seen from Table 5, the corrosion inhibitor of Example 1 can be used to prevent corrosion and discoloration of metal materials in printed circuit board assemblies during alkaline cleaning.

[0064] Tables 6 and 7 demonstrate that the cleaning agent containing the corrosion inhibitor of Example 1 meets the high reliability requirements for ionic residues in printed circuit board assemblies after soldering and cleaning.

[0065] In summary, the corrosion inhibitor provided by this invention for preventing corrosion and discoloration of printed circuit board (PCB) assemblies during alkaline cleaning effectively addresses the problem of corrosion and discoloration of alloy solder joints and other materials (aluminum alloy, copper alloy, nickel alloy, stainless steel, etc.) on PCB assemblies after soldering during alkaline cleaning. Furthermore, the addition of this corrosion inhibitor improves the cleaning effect of the cleaning agent without affecting the electrochemical reliability of the PCB assembly.

[0066] Example 2

[0067] Based on the corrosion inhibitor and protective agent provided in the first embodiment of this application for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, the second embodiment of this application proposes another corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning. The second embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the second embodiment will not affect the separate implementation of the first embodiment.

[0068] This invention provides a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following components by weight percentage: 25% sodium polyether disilicate, 5% ammonium lactate, 1% sodium tripolyphosphate, 2% triethanolamine, and 2×10⁻⁶ methylbenzotriazole. -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

[0069] Example 3

[0070] Based on the corrosion inhibitor provided in the first embodiment of this application for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, the third embodiment of this application proposes another corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning. The third embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the third embodiment will not affect the separate implementation of the first embodiment.

[0071] This invention provides a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following components by weight percentage: sodium metasilicate pentahydrate 23%, ammonium lactate 5%, sodium tripolyphosphate 2%, diethylene glycolamine 1.5%, and 5-methylbenzotriazole 3×10⁻⁶. -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

[0072] The present invention also provides a method for preparing a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, comprising the following steps:

[0073] S1, provides diethylene glycolamine and 5-methylbenzotriazole, with 5-methylbenzotriazole added to diethylene glycolamine;

[0074] S2 provides sodium metasilicate pentahydrate, potassium pyrophosphate and deionized water. Sodium metasilicate pentahydrate and potassium pyrophosphate are added to deionized water to dissolve them.

[0075] S3, add the mixture obtained in step S1 to the solution obtained in step S2, and let it stand for 5-8 minutes at a temperature of 20-30℃.

[0076] S4, providing ammonium lactate and fatty acid methyl ester ethoxylate sulfonate, adding ammonium lactate and fatty acid methyl ester ethoxylate sulfonate to the solution obtained in step S3;

[0077] S5. Provide a stirrer, add the solution obtained in step S4 into the stirrer and stir for 8-15 minutes until the solution remains transparent, thus preparing a corrosion inhibitor for preventing the printed circuit board assembly from corroding and discoloring during alkaline cleaning.

[0078] In step S5, the stirrer is a mechanical stirrer or an ultrasonic stirrer.

[0079] Please see Figure 1 Figure 1 shows a comparison of the effects of related technologies and the addition of corrosion inhibitors on aluminum alloys after cleaning with alkaline cleaning solutions. Figure 2 shows the effect after cleaning with existing alkaline cleaning solutions; Figure 3 shows the effect after cleaning with alkaline cleaning solutions after adding the corrosion inhibitor from Example 1. The corrosion inhibitor is provided and added to an alkaline diluted cleaning solution at a concentration-to-volume ratio of 0.3-1%. Using this cleaning solution to clean printed circuit board assemblies can prevent metal corrosion and discoloration of the printed circuit board assemblies.

[0080] Compared with related technologies, the corrosion inhibitor and protective agent and its preparation method provided by the present invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning have the following beneficial effects:

[0081] I. This invention provides a corrosion inhibitor and protective agent to prevent corrosion and discoloration of printed circuit board assemblies during alkaline cleaning. For soldered printed circuit board assemblies, the tin-lead alloy solder joints are prone to corrosion, oxidation, and discoloration during alkaline cleaning, and this agent provides corrosion inhibition and protection against corrosion.

[0082] Second, the corrosion inhibitor provided by this invention plays a role in inhibiting corrosion and preventing oxidation of other metal materials (aluminum alloy, copper alloy, nickel alloy, stainless steel, etc.) on printed circuit components.

[0083] Third, the corrosion inhibitor and protective agent provided by this invention for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning has good material compatibility with printed circuit boards and component assemblies.

[0084] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, characterized in that, Including the following components by weight percentage: sodium silicate 20-25%, ammonium lactate 5%, phosphate 1-3%, organic amine 1-2%, 5-methylbenzotriazole 2×10 -3 -5×10 -3 %, fatty acid methyl ester ethoxylate sulfonate 0.1%, the remainder is deionized water.

2. The corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning according to claim 1, characterized in that, The sodium silicate is sodium metasilicate pentahydrate or polyether organic disilicate.

3. The corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning according to claim 1, characterized in that, The phosphate is potassium pyrophosphate or sodium tripolyphosphate.

4. The corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning according to claim 1, characterized in that, The organic amine is diethylene glycolamine or triethanolamine.

5. A method for preparing a corrosion inhibitor for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning, characterized in that, Includes the following steps: S1, provides diethylene glycolamine and 5-methylbenzotriazole, with 5-methylbenzotriazole added to diethylene glycolamine; S2 provides sodium metasilicate pentahydrate, potassium pyrophosphate and deionized water. Sodium metasilicate pentahydrate and potassium pyrophosphate are added to deionized water to dissolve them. S3, add the mixture obtained in step S1 to the solution obtained in step S2, and let it stand for 5-8 minutes at a temperature of 20-30℃. S4, providing ammonium lactate and fatty acid methyl ester ethoxylate sulfonate, adding ammonium lactate and fatty acid methyl ester ethoxylate sulfonate to the solution obtained in step S3; S5. Provide a stirrer, add the solution obtained in step S4 into the stirrer and stir for 8-15 minutes until the solution remains transparent, thus preparing a corrosion inhibitor for preventing the printed circuit board assembly from corroding and discoloring during alkaline cleaning.

6. The method for preparing the corrosion inhibitor and protective agent for preventing corrosion and discoloration of printed circuit board assemblies during alkaline cleaning according to claim 5, characterized in that, In step S5, the stirrer is a mechanical stirrer or an ultrasonic stirrer.

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