Tin plating solution for magnetic core inductor electroplating and preparation method thereof

Abstract

The present invention discloses a tin-plating solution for magnetic core inductor electroplating and a preparation method thereof, comprising the following components: (1) at least one hydroxycarboxylate; (2) at least two polycarboxylic acids; (3) at least one stannous ion source; (4) at least one salt substance; (5) at least one C10-C14 alkyl compound. The preparation method is to add hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water, stir and dissolve, add stannous ion source and continue to stir evenly; finally add C10-C14 alkyl compound to obtain the solution. The plating solution of this system has good stability, the coating has a white and bright appearance, a dense and uniform appearance, is resistant to steam corrosion, has few impurities, has excellent soldering performance, and is a low-foaming environmentally friendly tin-plating solution, which is convenient for cleaning the product after plating and has a longer shelf life. In addition, the materials used in the tin-plating solution are mostly food-grade materials or environmentally friendly materials, which are less harmful to the human body and less polluting to the environment, and employees do not need strict protection when operating.

Description

Technical Field

[0001] The invention relates to the field of preparation of tin plating solution, C25D3 / 32, and in particular to a tin plating solution for magnetic core inductor electroplating and a preparation method thereof. Background Art

[0002] Inductors are important electronic components that are widely used in various electronic circuits, making it easier to realize various electronic functions. The magnetic core is made of materials with a higher magnetic permeability than air, which can confine the magnetic field more tightly around the inductor and increase the inductance. The magnetic core inductor has important energy storage, filtering, and oscillation functions. After the inductor component is installed, the inductor component needs to be combined with the circuit through wave soldering before use. In order to improve the solderability of the inductor component, it is often necessary to electroplate it. The tin plating layer, as the outermost plating layer, protects the inner plating layer from oxidation, while also improving the excellent welding performance of the component.

[0003] Patent CN105648483 discloses a high-speed tin-plating solution and a preparation method thereof. Through the combination of three grain refiners, the grain size is controlled within 3 to 8 μm, the growth of tin whiskers is strictly limited, and a uniform coating can be produced at different current densities. At the same time, the use of a low-foaming surfactant reduces impurities in the coating while avoiding the use of a defoaming agent, thereby ensuring the anti-discoloration performance of the coating. However, the composition of the tin-plating solution is complex and also includes components such as solvents and antioxidants. Patent CN110306213 proposes a tin-plating solution for solar cells and a preparation method thereof. The tin-plating solution includes: methanesulfonic acid, stannous methanesulfonate, an accelerator, a stabilizer and water. The accelerator composed of palmitoyl methionine and an acetylene compound and the stabilizer composed of a reducing sugar compound and sodium citrate work synergistically to improve the stability of the tin-plating solution and the bonding force between the coating and the substrate. The final coating is flat, uniform and dense, meeting the requirements of solar photovoltaic modules. However, the preparation process of the tin plating solution is complicated, and it needs to be stirred evenly, filtered 2-5 times in a cycle, and then electrolyzed at a low current for 2-4 hours, which takes a long time. Therefore, it is of great significance to study a tin plating solution for magnetic core inductor electroplating with good stability and simple preparation process. The tin plating solution also has the characteristics of uniform and dense coating appearance, steam corrosion resistance, less impurities, and excellent solderability. Summary of the invention

[0004] In order to solve the above problems, the first aspect of the present invention provides a tin plating solution for magnetic core inductor electroplating, comprising:

[0005] (1) at least one hydroxycarboxylate;

[0006] (2) at least two polycarboxylic acids;

[0007] (3) at least one stannous ion source;

[0008] (4) at least one salt substance, wherein the anion of the salt substance is the same as the anion of the stannous ion source;

[0009] (5) at least one C10-C14 alkyl compound;

[0010] Wherein: the carboxylate ions of the hydroxycarboxylate are different from those of the polycarboxylic acid, and the number of hydroxyl groups of the hydroxycarboxylate is greater than or equal to the number of hydroxyl groups of the polycarboxylic acid.

[0011] By adding hydroxycarboxylates and polycarboxylic acids to the stannous methanesulfonate plating solution, the content of stannous ions in the plating solution can reach 5-15g / L, thereby achieving high-speed electroplating; however, during the research and development process, the researchers found that if the selection of hydroxycarboxylates and polycarboxylic acids is unreasonable, a large amount of carboxylate radicals will combine with hydrogen in the plating solution, reducing the electroplating efficiency. Therefore, the researchers tend to replace hydroxycarboxylates or polycarboxylic acids with other substances. However, this will bring about the problem of poor stability of the plating solution. For example, during the electroplating process, turbidity will appear after no more than 40 days of continuous plating, which seriously affects the service life of the plating solution.

[0012] Due to the development trend of environmental protection, the researchers are committed to using food-grade materials or environmentally friendly materials to achieve excellent tin plating while reducing harm to the human body and environmental pollution, and employees do not need strict protection during operation; the researchers found that when the carboxylate ions of hydroxycarboxylates and polycarboxylic acids are different; and the number of hydroxyl groups of hydroxycarboxylates is greater than or equal to the number of hydroxyl groups of polycarboxylic acids, combined with the salt substances of the present application, C10-C14 alkyl compounds work together to stabilize the pH of the plating solution at 3-5; the stability of the current during the electroplating process is ensured, and the core inductance will not be "burned" during the electroplating process; and when the hydroxycarboxylate is sodium gluconate, then when the polycarboxylic acid is citric acid or tartaric acid, there is no need to add an antioxidant, and the tin plating solution is continuously plated for more than 65 days during the electroplating process without turbidity.

[0013] The hydroxycarboxylate is selected from at least one of sodium gluconate, sodium citrate, sodium tartrate and sodium malate;

[0014] The polycarboxylic acid is selected from at least two of gluconic acid, citric acid, tartaric acid, and malic acid;

[0015] In a preferred embodiment, the hydroxycarboxylate is sodium gluconate, the first polycarboxylic acid is gluconic acid, and the second polycarboxylic acid is citric acid; or the hydroxycarboxylate is sodium gluconate, the first polycarboxylic acid is tartaric acid, and the second polycarboxylic acid is gluconic acid; or the hydroxycarboxylate is sodium gluconate, the first polycarboxylic acid is tartaric acid, and the second polycarboxylic acid is citric acid;

[0016] In a preferred embodiment, the hydroxycarboxylate is sodium tartrate, and the polycarboxylic acid is citric acid or malic acid;

[0017] The stannous ion source is stannous methanesulfonate;

[0018] The salt substance is sodium methanesulfonate and / or potassium methanesulfonate;

[0019] The C10-C14 alkyl compound is at least one selected from dodecyltrimethylammonium, dodecyltrimethylammonium chloride, dodecyldimethylbenzylammonium chloride, sodium dodecylbenzenesulfonate, dodecyltrimethylammonium chloride, trimethyltetradecylammonium, and tetradecylammonium chloride; preferably, the C10-C14 alkyl compound is a C10-C14 alkylbenzyl compound; more preferably, the C10-C14 alkylbenzyl compound is dodecyldimethylbenzylammonium chloride;

[0020] By adding C10-C14 alkyl compounds to the plating solution, the C10-C14 alkyl compounds are selectively adsorbed on the uneven surfaces of the electrode, thereby promoting uniform deposition of tin; however, if the selection of hydroxycarboxylates and polycarboxylic acids is unreasonable, the coating will have poor oxidation resistance and poor water vapor resistance; the reason is that hydroxycarboxylates and polycarboxylic acids affect the selective adsorption of C10-C14 alkyl compounds; the researchers found that when the polycarboxylic acid is citric acid or tartaric acid, the water vapor resistance of the coating is improved; especially when the C10-C14 alkyl compound is C10-C14 alkyl Benzyl compounds, at an electroplating temperature of 22-30°C, have a coating that is resistant to water vapor for 16 hours without changing color, have strong antioxidant capacity, and have a bright white appearance of the tinned layer; it is speculated that the chain head of the C10-C14 alkylbenzyl compound is adsorbed on the electrode surface, and the chain tail is free on the electrode surface, and the appropriate electroplating temperature increases the proportion of the chain head functional group in the adsorption, thereby making the selectivity more obvious and the grains finer; after the temperature rises, thermal motion increases the effect of hydroxycarboxylates and polycarboxylic acids on the selective adsorption of C10-C14 alkyl compounds, and at the same time, the selectivity of the C10-C14 alkylbenzyl compound itself is also reduced.

[0021] Preferably, the mass concentration of the hydroxycarboxylate is 50-100 g / L;

[0022] Preferably, the mass concentration of the polycarboxylic acid is 9-18 g / L;

[0023] Preferably, the mass concentration ratio of the first polycarboxylic acid to the second polycarboxylic acid is 0.6-1.3:1;

[0024] Preferably, the mass concentration of the stannous ion source is 5-15 g / L;

[0025] Preferably, the mass concentration of the salt substance is 30-100 g / L; more preferably 30-50 g / L;

[0026] Preferably, the mass concentration of the C10-C14 alkyl compound is 1-5 g / L.

[0027] The pH of the tin plating solution is 3-5.

[0028] The electroplating conditions of the tin plating solution are: temperature 22-30° C., current 1-100A, preferably 8-30A, and time 60-100min.

[0029] During the plating process, the researchers not only focus on the stability of the plating solution, the environmental friendliness of the materials, and the oxidation resistance of the plating, but also, due to the particularity of the magnetic core inductor, the tinned product must not easily grow whiskers to avoid short circuits. This system selects C10-C14 alkyl benzyl compounds, and tins the nickel plating layer under the action of salt substances, carboxylic acid compounds, etc., and only very few Sn-Ni intermetallic compounds are generated. In particular, when the C10-C14 alkyl benzyl compound is dodecyl dimethyl benzyl ammonium chloride, the wet heat storage reaches 330 days, and no micro-convexity appears on the surface of the tinned layer, which significantly prolongs the incubation period of whiskers and the shelf life of the product. This system is a low-foaming environmentally friendly tinning solution, which is convenient for cleaning the product after plating.

[0030] A second aspect of the present invention provides a method for preparing a tin plating solution for magnetic core inductor electroplating, comprising the following steps:

[0031] (1) adding hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water and stirring to dissolve;

[0032] (2) adding stannous ion source and continuing to stir evenly;

[0033] (3) Add a C10-C14 alkyl compound to obtain.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] (1) The materials used are mostly food-grade materials or environmentally friendly materials, which are less harmful to the human body and less polluting to the environment, and employees do not need strict protection when operating;

[0036] (2) The tin plating layer of this system has a bright white surface and excellent soldering performance;

[0037] (3) This system is a low-foaming, environmentally friendly tin plating solution, which is convenient for cleaning the product after plating and prolongs the shelf life of the product. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 : EDS image of the plated part obtained in Example 3;

[0039] Figure 2 : SEM image of the plated layer obtained in Example 1;

[0040] Figure 3 : SEM image of the plated layer obtained in Example 2;

[0041] Figure 4 : SEM image of the coating of the plated part obtained in Example 3. DETAILED DESCRIPTION

[0042] Embodiment 1: A tin plating solution for magnetic core inductor electroplating, comprising:

[0043] (1) Hydroxycarboxylate with a mass concentration of 100 g / L;

[0044] (2) two polycarboxylic acids at a mass concentration of 18 g / L;

[0045] (3) a stannous ion source having a mass concentration of 15 g / L;

[0046] (4) a salt substance with a mass concentration of 50 g / L;

[0047] (5) a C10-C14 alkyl compound at a mass concentration of 5 g / L;

[0048] The hydroxycarboxylate is sodium gluconate;

[0049] The two polycarboxylic acids are tartaric acid and citric acid, and the mass concentration ratio is 1:1;

[0050] The stannous ion source is stannous methanesulfonate;

[0051] The salt substance is sodium methanesulfonate;

[0052] The C10-C14 alkyl compound is dodecyl dimethyl benzyl ammonium chloride (CAS No.: 8001-54-5);

[0053] The electroplating conditions of the tin plating solution are: temperature 25° C., current 15 A, and time 80 min.

[0054] A method for preparing a tin plating solution for magnetic core inductor electroplating, comprising the following steps:

[0055] (1) adding hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water and stirring to dissolve;

[0056] (2) adding stannous ion source and continuing to stir evenly;

[0057] (3) Add a C10-C14 alkyl compound to obtain.

[0058] Embodiment 2: A tin plating solution for magnetic core inductor electroplating, comprising:

[0059] (1) Hydroxycarboxylate with a mass concentration of 50 g / L;

[0060] (2) two polycarboxylic acids at a mass concentration of 9 g / L;

[0061] (3) a stannous ion source having a mass concentration of 5 g / L;

[0062] (4) a salt substance with a mass concentration of 30 g / L;

[0063] (5) a C10-C14 alkyl compound at a mass concentration of 1 g / L;

[0064] The hydroxycarboxylate is sodium gluconate;

[0065] The two polycarboxylic acids are tartaric acid and citric acid, and the mass concentration ratio is 1:1;

[0066] The stannous ion source is stannous methanesulfonate;

[0067] The salt substance is sodium methanesulfonate;

[0068] The C10-C14 alkyl compound is dodecyl dimethyl benzyl ammonium chloride;

[0069] The electroplating conditions of the tin plating solution are: temperature 25° C., current 15 A, and time 80 min.

[0070] A method for preparing a tin plating solution for magnetic core inductor electroplating, comprising the following steps:

[0071] (1) adding hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water and stirring to dissolve;

[0072] (2) adding stannous ion source and continuing to stir evenly;

[0073] (3) Add a C10-C14 alkyl compound to obtain.

[0074] Embodiment 3: A tin plating solution for magnetic core inductor electroplating, comprising:

[0075] (1) Hydroxycarboxylate with a mass concentration of 75 g / L;

[0076] (2) two polycarboxylic acids at a mass concentration of 13.5 g / L;

[0077] (3) a stannous ion source having a mass concentration of 10 g / L;

[0078] (4) a salt substance with a mass concentration of 45 g / L;

[0079] (5) a C10-C14 alkyl compound at a mass concentration of 3 g / L;

[0080] The hydroxycarboxylate is sodium gluconate;

[0081] The two polycarboxylic acids are tartaric acid and citric acid, and the mass concentration ratio is 1:1;

[0082] The stannous ion source is stannous methanesulfonate;

[0083] The salt substance is sodium methanesulfonate;

[0084] The C10-C14 alkyl compound is dodecyl dimethyl benzyl ammonium chloride;

[0085] The electroplating conditions of the tin plating solution are: temperature 25° C., current 15 A, and time 80 min.

[0086] A method for preparing a tin plating solution for magnetic core inductor electroplating, comprising the following steps:

[0087] (1) adding hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water and stirring to dissolve;

[0088] (2) adding stannous ion source and continuing to stir evenly;

[0089] (3) Add a C10-C14 alkyl compound to obtain.

[0090] Comparative Example 1: A tinning solution for magnetic core inductor electroplating

[0091] The difference from Example 3 is that tartaric acid is replaced by gluconic acid.

[0092] A method for preparing a tin plating solution for magnetic core inductor electroplating, same as Example 3.

[0093] Comparative Example 2: A tin plating solution for magnetic core inductor electroplating

[0094] The difference from Example 3 is that citric acid is replaced by gluconic acid.

[0095] A method for preparing a tin plating solution for magnetic core inductor electroplating, same as Example 3.

[0096] Comparative Example 3: A tin plating solution for magnetic core inductor electroplating

[0097] The difference from Example 3 is that the electroplating temperature is 45°C.

[0098] A method for preparing a tin plating solution for magnetic core inductor electroplating, same as Example 3.

[0099] Comparative Example 4: A tin plating solution for magnetic core inductor electroplating

[0100] The difference from Example 3 is that the C10-C14 alkyl compound is dodecyltrimethylammonium chloride (CAS No.: 112-00-5).

[0101] A method for preparing a tin plating solution for magnetic core inductor electroplating, same as Example 3.

[0102] Comparative Example 5: A tin plating solution for magnetic core inductor electroplating

[0103] The difference from Example 3 is that the C10-C14 alkyl compound is sodium dodecylbenzenesulfonate (CAS No.: 25155-30-0).

[0104] A method for preparing a tin plating solution for magnetic core inductor electroplating, same as Example 3.

[0105] Performance Test:

[0106] 1. EDS detection: EDS detection of the plated piece obtained in Example 3 shows that the content of Sn is 91.93%, with high purity, and the impurity content of Ni and Fe is low ( Figure 1 ).

[0107] 2. Microstructure of coating: Use SEM to observe whether the coating crystals are fine and uniform.

[0108] The plated layer obtained in Example 1 is fine and uniform ( Figure 2 ); The coating obtained in Example 2 is fine and uniform ( Figure 3 ); Example 3 obtained coating fine, uniform ( Figure 4 ); the coatings obtained in Comparative Examples 1, 2, and 5 are fine and uniform; the coatings obtained in Comparative Examples 3 and 4 are rough.

[0109] 3. Plating solution stability: During the electroplating process, observe whether the tin plating solution becomes turbid after 65 days.

[0110] The plated parts obtained in Examples 1-3 were not turbid for 65 days; the plated parts obtained in Comparative Examples 1-3 were turbid after 65 days; and the plated parts obtained in Comparative Examples 4 and 5 were not turbid for 65 days.

[0111] 4. Water vapor test: The plated parts obtained in the examples and comparative examples were placed in a water vapor environment, and observation and recording were made as to whether the coating changed after 16 hours.

[0112] The coatings of the plated parts obtained in Examples 1-3 did not change; the coatings of the plated parts obtained in Comparative Examples 1-5 changed color.

[0113] 5. Wet heat storage time: The plated parts obtained in the examples and comparative examples were placed at 55°C and 85% RH for 330 days, and the plated layers were observed by SEM.

[0114] The tin-plated layers of the plated parts obtained in Examples 1-3 had no micro-protrusions or whiskers on their surfaces; the tin-plated layers of the plated parts obtained in Comparative Examples 1-5 had micro-protrusions or whiskers on their surfaces.

Claims

1. A tin plating solution for magnetic core inductor electroplating, characterized in that: The components include: (1) at least one hydroxycarboxylate; (2) at least two polycarboxylic acids; (3) at least one stannous ion source; (4) at least one salt substance, wherein the anion of the salt substance is the same as the anion of the stannous ion source; (5) at least one C10-C14 alkyl compound; The hydroxycarboxylate is sodium gluconate; The polycarboxylic acids include tartaric acid and citric acid; The stannous ion source is stannous methanesulfonate; The salt substance is sodium methanesulfonate and / or potassium methanesulfonate; The C10-C14 alkylbenzyl compound is dodecyldimethylbenzylammonium chloride; The mass concentration of the hydroxycarboxylate is 50-100 g / L; The mass concentration of the polycarboxylic acid is 9-18 g / L; The pH of the tin plating solution is 3-5.

2. The tin plating solution for magnetic core inductor electroplating according to claim 1, characterized in that: The hydroxycarboxylate has a different carboxylate ion from the polycarboxylic acid, and the number of hydroxyl groups in the hydroxycarboxylate is greater than or equal to the number of hydroxyl groups in the polycarboxylic acid.

3. The tin plating solution for magnetic core inductor electroplating according to claim 1, characterized in that: The electroplating conditions of the tin plating solution are: temperature 22-30° C., current 1-100A, and time 60-100min.

4. A method for preparing a tin plating solution for magnetic core inductor electroplating according to any one of claims 1 to 3, characterized in that: The steps include: (1) adding hydroxycarboxylate, salt substance and polycarboxylic acid into deionized water and stirring to dissolve; (2) adding stannous ion source and continuing to stir evenly; (3) Add a C10-C14 alkyl compound to obtain.

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