An electroplating tin solution, its preparation method and application

Abstract

The present invention discloses a tin plating solution, which comprises stannous methylsulfonate ions, an acid, a surfactant, a conductive salt, potassium ions, and a grain refiner, and the pH value ranges from 3.5 to 4.0. The grain refiner is 1-substituted imidazole p-toluenesulfonate. By adding a specific content of the grain refiner to the tin plating solution and simultaneously adjusting the pH value to range from 3.5 to 4.0, the present invention can promote the continuous nucleation of tin grains during the tin plating process, form a dense tin plating layer, and thus improve the tin plating performance.

Description

Technical Field

[0001] The present invention relates to the technical field of tin electroplating, and particularly to a tin electroplating solution, a preparation method thereof, and an application thereof. Background Art

[0002] Tin has the advantages of corrosion resistance, color change resistance, non-toxicity, easy soldering, softness, low melting point, and good ductility. In recent years, the tin plating layer has been widely used as an antioxidant protection layer in industries such as electronic components and semiconductor packages based on copper and copper alloys, and is usually formed by electroplating. Electroplating is a process of plating a layer of other metals or alloys on the surface of certain metals by using the electrolysis principle, and is a process of attaching a metal film to the surface of a metal or other material substrate by using electrolysis. Barrel plating is a means of placing the workpiece to be plated in a drum (horizontal drum or open basket), then immersing it in the plating solution, and performing electroplating after energization.

[0003] Metal deposition requires nucleation first. Nucleation refers to the active sites formed first on the cathode, and nucleation largely determines the density, flatness, and dendrite growth of the plating layer. Theoretically, nucleation is divided into continuous nucleation and instantaneous nucleation. Among them, continuous nucleation refers to the continuous formation of active sites on the cathode surface during the deposition process for nucleation, while instantaneous nucleation refers to the formation of some active sites on the cathode surface only in a short time at the beginning of the deposition process for nucleation. The higher the proportion of continuous nucleation, the better. However, the proportion of continuous nucleation during tin plating with the existing tin plating solution is not high, resulting in relatively large gaps between the tin crystals of the tin layer. Summary of the Invention

[0004] The purpose of the present invention is to provide a tin plating solution that can achieve more continuous nucleation and improve the density of the tin plating layer.

[0005] The present invention is achieved by the following technical solutions:

[0006] A tin electroplating solution includes the following components:

[0007] The concentration of stannous methylsulfonate ions is 1 - 100 g / L;

[0008] The concentration of acid is 10 - 200 g / L;

[0009] The concentration of surfactant is 1 - 15 g / L;

[0010] The concentration of conductive salt is 2 - 200 g / L;

[0011] The concentration of potassium ions is 21 - 70 g / L;

[0012] The concentration of grain refiner is 0.001 - 1 g / L;

[0013] The pH value range of the tin electroplating solution is 3.5 - 4.0;

[0014] The grain refiner is 1-substituted imidazole p-toluenesulfonate.

[0015] The 1-substituted imidazole p-toluenesulfonate is selected from at least one of 1-methylimidazole p-toluenesulfonate, 1-ethylimidazole p-toluenesulfonate, and 1-ethyl-3-methylimidazole p-toluenesulfonate.

[0016] Preferably, the grain refiner is selected from 1-ethylimidazole p-toluenesulfonate;

[0017] Preferably, the concentration range of the grain refiner is 0.01 - 0.5 g / L.

[0018] The acid is at least one of methanesulfonic acid, ethanesulfonic acid, citric acid, tartaric acid, acrylic acid, oxalic acid, phosphoric acid, sulfuric acid, boric acid, and nitric acid; preferably methanesulfonic acid.

[0019] Preferably, the surfactant is at least one of lauryl alcohol polyoxyethylene ether, tetradecylthiol polyoxyethylene ether, and octadecyl bis-ester quaternary ammonium salt; more preferably, a compound of lauryl alcohol polyoxyethylene ether / tetradecylthiol polyoxyethylene ether / octadecyl bis-ester quaternary ammonium salt, and the compounding ratio range is (10 - 15):1:(8 - 10).

[0020] In the formulation of the present invention, the surfactant can also be sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, polyoxyethylene (20) sorbitan monolaurate, etc.

[0021] The conductive salt is selected from at least one of alkyl sulfonates, gluconates, citrates, tartrates, acrylate salts, oxalates, phosphates, sulfates, and nitrates.

[0022] The potassium ions are derived from at least one of potassium hydroxide, potassium nitrate, and potassium sulfate.

[0023] The pH value is adjusted by a pH regulator, and the pH regulator is at least one of potassium hydroxide, sodium hydroxide, and methanesulfonic acid.

[0024] The dispersion medium of the electroplating tin solution is water.

[0025] A method for preparing an electroplating tin solution includes the following steps: mixing evenly according to the concentrations of each component with deionized water, and then adjusting the pH value to be between 3.5 and 4.0 by an acid or a pH regulator.

[0026] The application of the electroplating tin solution is for barrel electroplating tin.

[0027] The present invention has the following beneficial effects:

[0028] The present invention can promote the continuous nucleation of tin grains during the tin plating process and form a dense tin plating layer by adding a specific content of grain regulators (at least one of 1-methylimidazole p-toluenesulfonate, 1-ethylimidazole p-toluenesulfonate, 1-ethyl-3-methylimidazole p-toluenesulfonate) in the tin plating solution and adjusting the pH value range to 3.5 - 4.0, thereby improving the tin plating performance. Description of the Drawings

[0029] Figure 1 : SEM image of tin grains after electroplating in Example 1.

[0030] Figure 2 : SEM image of tin grains after electroplating in Comparative Example 1. Detailed Description of the Invention

[0031] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0032] The raw materials used in the present invention are commercially available products.

[0033] Preparation of the electroplating tin solutions for the examples and comparative examples: Mix evenly according to the concentrations of each component with deionized water, and then adjust the pH value with a pH regulator.

[0034] Equipment and current conditions for barrel plating tin in the examples and comparative examples:

[0035] Workpieces: 10MΩ, 1206 model resistors, 5000 pieces;

[0036] Steel balls: 0.5 - 0.7 nm in diameter; 1.5 kg;

[0037] Aluminum oxide balls: 10 mm in diameter, 300 g;

[0038] Drum: open drum, 4.5 L;

[0039] Rotation speed: 16 revolutions / min;

[0040] Nickel plating: 31 A; 120 min;

[0041] Tin plating: 17 A; 90 min.

[0042] Testing methods for each item:

[0043] (1)Solderability evaluation method: After electroplating 30 plated parts with the electroplated tin solutions of the examples and comparative examples respectively, take out 30 of the plated parts in this cage. According to the wetting balance method in the IPC / EIA / JEDEC J-STD-002C standard (Solderability Test Standard for Components), use the MALCOM SWB-2 wetting balance tester to conduct solderability tests on the above-mentioned plated parts in sequence, and record the number of qualified parts. Industrially, at least 60% of the qualified rate of the plated parts is required to meet the requirements.

[0044] Example 1:

[0045]

[0046] Example 2:

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[0048] Example 3:

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[0050] Example 4:

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[0052] Example 5:

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[0054] Example 6:

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[0056] Example 7:

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[0058] Example 8:

[0059]

[0060] Example 9:

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[0062] Example 10:

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[0064] Example 11:

[0065]

[0066] Example 12:

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[0068] Example 13:

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[0070] Example 14:

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[0072] Example 15:

[0073]

[0074] Comparative Example 1:

[0075]

[0076] Comparative Example 2:

[0077]

[0078] Comparative Example 3:

[0079]

Claims

1. A tin plating solution, characterized in that, It includes the following components: The ionic concentration of stannous methyl sulfonate is 1-100 g / L; The acid concentration is 10-200 g / L; The surfactant concentration is 1-15 g / L; The conductive salt concentration is 2-200 g / L; The potassium ion concentration is 21-70 g / L; The concentration of the grain refiner is 0.001-1 g / L; The pH value range of the tin electroplating solution is 3.5-4.0; The grain refiner is 1-substituted imidazole p-toluenesulfonate, and the 1-substituted imidazole p-toluenesulfonate is selected from at least one of 1-methylimidazole p-toluenesulfonate, 1-ethylimidazole p-toluenesulfonate, and 1-ethyl-3-methylimidazole p-toluenesulfonate.

2. The electroplating tin solution according to claim 1, wherein, The grain refiner is selected from 1-ethylimidazole p-toluenesulfonate.

3. The tin electroplating solution according to claim 1, characterized in that, The concentration range of the grain refiner is 0.01-0.5 g / L.

4. The electroplating tin solution according to claim 1, wherein, The acid is at least one of methanesulfonic acid, ethanesulfonic acid, citric acid, tartaric acid, acrylic acid, oxalic acid, phosphoric acid, sulfuric acid, boric acid, and nitric acid.

5. The electroplating tin solution according to claim 4, characterized in that, The acid is methanesulfonic acid.

6. The electroplating tin solution according to claim 1, characterized in that, The surfactant is at least one of lauryl alcohol polyoxyethylene ether, tetradecyl mercaptan polyoxyethylene ether, and octadecyl diester quaternary ammonium salt.

7. The electroplating tin solution according to claim 1, wherein The surfactant is a compound of lauryl alcohol polyoxyethylene ether / tetradecyl mercaptan polyoxyethylene ether / octadecyl diester quaternary ammonium salt, and the compounding ratio range is (10-15):1:(8-10).

8. The electroplating tin solution according to claim 1, wherein, The conductive salt is selected from at least one of alkyl sulfonates, gluconates, citrates, tartrates, acrylates, oxalates, phosphates, sulfates, and nitrates.

9. The electroplating tin solution according to claim 1, characterized in that, The potassium ions are derived from at least one of potassium hydroxide, potassium nitrate, and potassium sulfate; the pH value is adjusted by a pH regulator, and the pH regulator is at least one of potassium hydroxide, sodium hydroxide, and methanesulfonic acid.

10. The electroplating tin solution according to claim 1, characterized in that, The dispersion medium of the tin electroplating solution is water.

11. The preparation method of the tin electroplating solution according to any one of claims 1-10, characterized in that, It includes the following steps: Mix evenly according to the concentration of each component with deionized water, and then adjust the pH value to be between 3.5 and 4.0 through a pH regulator.

12. Use of the electroplating tin solution according to any one of claims 1-10, characterized in that, It is used for barrel tin electroplating.

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