A tin plating process for electronic components

Abstract

The present invention relates to C25D3 / 32, and more particularly to a tin plating process for electronic components. The process comprises the following steps: (1) subjecting the surface of the electronic component to degreasing, ultrasonic treatment, oil removal, water washing, pickling activation, and water washing to obtain a clean surface of the electronic component for standby use; (2) preparing an electroplating solution; and (3) tin plating: placing the electronic component described in step (1) in the electroplating solution described in step (2) for electroplating, followed by water washing and drying to obtain a tin-plated electronic component. The tin plating layer prepared by the tin plating process for electronic components provided by the present invention has the advantages of low porosity, bright coating, thin coating, and high bonding strength.

Description

Technical Field

[0001] The present invention relates to C25D3 / 32, and in particular to a tin electroplating process for electronic components. Background Art

[0002] The tin ions are reduced from the electroplating solution to the surface of the substrate using electric current to form an electroplated tin layer. Compared with other electroplating methods, it has the advantages of high strength, good weldability, corrosion resistance, and non-toxicity. Therefore, it has gradually gained people's favor and is widely used in the field of electroplating technology.

[0003] Patent CN101705482A provides an alkyl sulfonic acid chemical tin plating solution and a tin plating process based on the chemical tin plating solution. The tin plating solution prepared by the mutual coordination of raw materials such as organic sulfonates, organic acids, and complexing agents has a high tin content, a thin coating, and good insulation.

[0004] Patent CN103352240B provides an electrotin plating process for SMD automotive electronic components. By coordinating different steps and using a specific tin plating solution, the soldering capacity is improved, the tin plating layer has good bonding strength with the weld, and has strong antioxidant ability.

[0005] However, the above-mentioned technology does not solve the problem of high porosity of the coating, poor electrochemical corrosion protection ability, and the substrate is easily damaged during use. Summary of the Invention

[0006] In order to solve the above technical problems, the first aspect of the present invention provides an electronic component electrotin plating process, comprising the following steps:

[0007] (1) The surface of the electronic component is subjected to degreasing, ultrasonic degreasing, water washing, pickling activation, and water washing to obtain a clean surface of the electronic component for standby use;

[0008] (2) preparing an electroplating solution;

[0009] (3) Tin plating: placing the electronic component described in step (1) in the electroplating solution described in step (2) for electroplating, and then washing and drying to obtain an electronic component with a tinned surface;

[0010] Preferably, the frequency of the fat removal ultrasound in step (1) is 200-500 Hz, and the ultrasound time is 2-4 minutes.

[0011] Preferably, the amount of degreasing powder used in the degreasing process is 40-50 g / L, the temperature is 40-70°C, and the current density is 2-5 A / dm 2 The degreasing powder was purchased from Guangdong Dazhi Environmental Protection Technology Co., Ltd., model: DC-3.

[0012] Preferably, the temperature during the pickling activation is 20-30° C. and the time is 0.5-2 min.

[0013] Preferably, the electroplating solution in step (2) comprises the following raw materials: 30-60 g / L of tin salt, 120-150 g / L of phosphate, 300-400 g / L of complexing agent, and 5-15 g / L of polyoxyethylene compound.

[0014] Preferably, the tin salt includes at least one of tin halide, tin sulfate, tin alkyl sulfonate, and tin aryl sulfonate.

[0015] More preferably, the tin salt is an alkyl sulfonate of tin.

[0016] Preferably, the alkyl chain length of the tin alkyl sulfonate is C1-C3 (C1-C3 refers to the alkyl chain length, for example, C1 contains a methyl group as the carbon chain).

[0017] Preferably, the complexing agent includes at least one of ethylenediaminetetraacetic acid, triethylenetetraaminehexaacetic acid, methanesulfonic acid, aminosulfonic acid, malic acid, thiourea, ethylenethiourea, and ethylenethiourea.

[0018] Preferably, the complexing agent comprises triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea, wherein the mass ratio of triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea is (2-4): (7-10): (2-4).

[0019] Preferably, the phosphate comprises sodium hypophosphite and / or sodium pyrophosphate.

[0020] More preferably, the phosphate is sodium hypophosphite.

[0021] Preferably, the polyoxyethylene compound includes at least one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, fatty alcohol polyoxyethylene ester, polyoxyethylene sorbitan fatty acid ester, and polyoxyethylene polyoxypropylene copolymer.

[0022] Further preferably, the polyoxyethylene compound includes polyoxyethylene sorbitan fatty acid ester.

[0023] Preferably, the polyoxyethylene sorbitan fatty acid ester.

[0024] Preferably, the electroplating solution further comprises the following raw materials: 0.8-1.2 g / L of polyethylene glycol, 2-3 g / L of carbon-carbon triple bond compounds, 2-3 g / L of propane sulfonic acid compounds, 3-7 g / L of stabilizer, and 2-4 g / L of auxiliary agent.

[0025] Preferably, the average molecular weight of the polyethylene glycol is 2000-4000.

[0026] Preferably, the carbon-carbon triple bond-containing compound includes at least one of 1-propargyloxy-2,3-dihydroxypropanediol, 3-hexyn-2,5-diol, 2,5-dimethyl-2,5-hexynediol, N,N-diethylpropargylamine, and butynediol.

[0027] More preferably, the carbon-carbon triple bond-containing compound includes N,N-diethylpropargylamine.

[0028] Preferably, the propane sulfonic acid compound includes at least one of sodium 3-(benzothiazole-2-mercapto)-propane sulfonate, sodium 3-mercapto-1-propane sulfonate, sodium N,N-dimethyl-dithiocarbonylpropane sulfonate, sodium polydisulfide propane sulfonate, propane sulfonic acid pyridinium salt, and hydroxypropane sulfonic acid pyridinium salt.

[0029] Preferably, the propane sulfonic acid compounds include sodium 3-(benzothiazole-2-mercapto)-propane sulfonate and pyridinium hydroxypropane sulfonate.

[0030] More preferably, the mass ratio of the N,N-diethylpropargylamine, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and pyridinium hydroxypropanesulfonate is (2-3):(1-2):(1-2).

[0031] Preferably, the stabilizer includes at least one of hydroquinone, catechol, resorcinol, ammonium methanesulfonate, ascorbic acid, hydroquinone stabilizers, hydrazine stabilizers, and pyrazolone stabilizers.

[0032] More preferably, the stabilizer comprises hydroquinone and ascorbic acid, wherein the mass ratio of the hydroquinone to ascorbic acid is (3-7): (2-4).

[0033] Preferably, the auxiliary agent includes succinic acid and trimethylacetic acid.

[0034] Preferably, the current density of the electroplating in step (3) is 0.5-5A / dm 2 ;

[0035] Preferably, the electroplating temperature in step (3) is 25-65°C;

[0036] Preferably, the electroplating time in step (3) is 5-20 minutes.

[0037] Beneficial effects:

[0038] 1) The present invention limits the current density, temperature, time and other parameters in the electrotin plating process, and uses an electrotin plating solution prepared with components such as tin salt, phosphate, complexing agent, and polyoxyethylene compound to perform an electrotin plating operation on the surface of a substrate. The prepared electrotin layer has the advantages of low porosity, bright coating, thin coating, and high bonding strength.

[0039] 2) Copper has a high potential and high chemical activity. The present invention uses triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea as a coordination system to form a stable complex system with copper ions, thereby enhancing electrochemical polarization, avoiding hydrolysis of tin ions, and improving the bonding strength between the tin plating layer and the copper substrate. In particular, when the mass ratio is (2-4): (7-10): (2-4), the nucleation rate is controlled and the generation of porosity is reduced.

[0040] 3) The present invention utilizes N,N-diethylpropargylamine, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate, and pyridinium hydroxypropanesulfonate as brighteners, thereby improving the brightness of the coating and increasing the degree of cathode polarization, thereby refining the grains, making the coating uniform and fine, and reducing porosity. In particular, when the mass ratio is (2-3):(1-2):(1-2), stress whiskers generated by the diffusion of tin and other metals are reduced, thereby improving the solderability and bonding strength of the tin plating.

[0041] 4) The present invention adds succinic acid and trimethylacetic acid as auxiliary agents, which work together with the polyoxyethylene compound of the present invention to avoid excessive foaming that hinders the heat dissipation reaction of the solution, maintain an appropriate electromigration speed, and make the prepared tin plating layer uniform without scars and whiskers.

[0042] 5) The present invention controls the nucleation deposition rate, increases the driving force of the replacement process and the ion diffusion rate, and changes the concentration polarization effect of the system by limiting the electroplating tin process, so that the prepared tin plating layer has higher corrosion resistance and solderability. DETAILED DESCRIPTION

[0043] Example

[0044] Example 1

[0045] An electronic component electrotin plating process comprises the following steps:

[0046] (1) The surface of the electronic component is subjected to degreasing, ultrasonic degreasing, water washing, pickling activation, and water washing to obtain a clean surface of the electronic component for standby use;

[0047] (2) preparing an electroplating solution;

[0048] (3) Tin plating: The electronic component described in step (1) is placed in the electroplating solution described in step (2) for electroplating, and then washed and dried to obtain an electronic component with a tinned surface.

[0049] The frequency of the degreasing ultrasound in step (1) is 300 Hz, and the ultrasonic time is 3 min. The ultrasonic degreasing agent used in the degreasing ultrasound is purchased from Shenzhen Tianyue New Material Technology Co., Ltd.

[0050] The amount of degreasing powder used in the degreasing process is 45 g / L, the temperature is 50° C., and the current density is 3 A / dm 2 The degreasing powder was purchased from Guangdong Dazhi Environmental Protection Technology Co., Ltd., model: DC-3.

[0051] The acid cleaning activation temperature is 25°C and the time is 1 min. The acid cleaning agent is purchased from Guangdong Dazhi Environmental Protection Technology Co., Ltd., model: DC-A, with an activator dosage of 60 g / L.

[0052] The electroplating solution in step (2) comprises the following raw materials: 50 g / L of tin salt, 128 g / L of phosphate, 350 g / L of ligand, 10 g / L of polyoxyethylene compound, 1 g / L of polyethylene glycol, 2.5 g / L of carbon-carbon triple bond-containing compound, 2.5 g / L of propane sulfonic acid compound, 5 g / L of stabilizer, and 3 g / L of auxiliary agent.

[0053] The tin salt is an alkyl sulfonate of tin. The alkyl chain length of the alkyl sulfonate of the tin is C1 (C1 means a carbon chain containing a methyl group), specifically tin methanesulfonate (CAS No.: 53408-94-9).

[0054] The complexing agent comprises triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea, wherein the mass ratio of the triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea is 3:8:3.

[0055] The phosphate is sodium hypophosphite.

[0056] The polyoxyethylene compound includes polyoxyethylene sorbitan fatty acid ester. The polyoxyethylene sorbitan fatty acid ester is Tween-80.

[0057] The polyethylene glycol has an average molecular weight of 3000 and was purchased from Nantong Yixun Chemical Co., Ltd.

[0058] The carbon-carbon triple bond compound is N,N-diethylpropargylamine. The propane sulfonic acid compound includes sodium 3-(benzothiazole-2-mercapto)-propane sulfonate and pyridinium hydroxypropane sulfonate. The mass ratio of N,N-diethylpropargylamine, sodium 3-(benzothiazole-2-mercapto)-propane sulfonate, and pyridinium hydroxypropane sulfonate is 2.5:1.5:1.5. The N,N-diethylpropargylamine and sodium 3-(benzothiazole-2-mercapto)-propane sulfonate were purchased from Hubei Youshida Technology Co., Ltd. The propane sulfonic acid compound was purchased from Wuhan Songshi Technology Co., Ltd.

[0059] The stabilizer comprises hydroquinone and ascorbic acid, wherein the mass ratio of the hydroquinone to the ascorbic acid is 5:3.

[0060] The auxiliary agent includes succinic acid and trimethylacetic acid, and the mass ratio of the succinic acid to the trimethylacetic acid is 2:1.

[0061] The method for preparing the electroplating solution in step 3) comprises the following steps:

[0062] The preparation method of the electroplating solution comprises weighing, by mass, 50 g of tin salt, 128 g of phosphate, 350 g of a complexing agent, 10 g of a polyoxyethylene compound, 1 g of polyethylene glycol, 2.5 g of a carbon-carbon triple bond-containing compound, 2.5 g of a propane sulfonic acid compound, 5 g of a stabilizer, and 3 g of an auxiliary agent; uniformly mixing the weighed raw materials with 2 / 3 L of deionized water; and then adding the remaining deionized water to make up to volume.

[0063] The current density of the electroplating in step (3) is 3A / dm 2 ; The electroplating temperature in step (3) is 50°C; the electroplating time in step (3) is 15 minutes.

[0064] Example 2

[0065] A tin electroplating process for electronic components, the specific implementation method is the same as that of Example 1, except that the mass ratio of hydroquinone to ascorbic acid is 7:4.

[0066] Example 3

[0067] A tin plating process for electronic components, the specific implementation method is the same as that of Example 1, except that the electroplating solution in step (1) comprises the following raw materials: 30 g / L of tin salt, 120 g / L of phosphate, 300-40 g / L of complexing agent, 5 g / L of polyoxyethylene compound, 0.8 g / L of polyethylene glycol, 2 g / L of polycyclic compound containing thiol group, 2 g / L of propane sulfonic acid compound, 3 g / L of stabilizer, and 2 g / L of auxiliary agent.

[0068] Comparative Example 1

[0069] A tin electroplating process for electronic components, the specific implementation method is the same as that of Example 1, except that the mass ratio of N,N-diethylpropargylamine, sodium 3-(benzothiazole-2-mercapto)-propanesulfonate and pyridinium hydroxypropanesulfonate is 2.5:1.5:4.

[0070] Comparative Example 2

[0071] A tin electroplating process for electronic components, the specific implementation method is the same as that of Example 1, except that the mass ratio of triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea is 3:8:6.

[0072] Performance Testing

[0073] 1. Porosity test: The porosity of the coating was determined by the filter paper method: the filter paper was immersed in a mixed test solution composed of 10 g / L potassium ferrocyanide, 60 g / L sodium chloride, and 10 g / L potassium ferrocyanide in water as the solvent, and the filter paper was tightly attached to the surface of the sample prepared in the above embodiment and comparative example. There should be no bubbles between the filter paper and the sample, and the filter paper was kept wet for 20 minutes. After that, the filter paper was peeled off and rinsed with distilled water. Then, the filter paper was placed on a glass plate and dried. The number of blue spots per unit area was observed. Porosity (%) = number of blue spots (pieces) / test area (cm 2 ).

[0074] 2. Electroplated tin layer thickness test: A copper sheet (4 cm × 4 cm × 0.1 cm) was electroplated according to the above-mentioned electroplating tinning process, and the thickness of the tinned layer on the copper sheet was measured using an optical thickness gauge.

[0075] 3. Adhesion Test: A bending test was conducted in accordance with GB / T 5270-2005. The specimens used in the above examples and comparative examples were repeatedly bent 180° along an axis with a diameter equal to the thickness of the specimen until the base metal of the specimen was broken. The coating was observed to see if it peeled or fell off.

[0076] Table 1 Performance test results

[0077] Porosity% Tin layer thickness μm Binding force Example 1 0.21 1.19 No peeling, no shedding Example 2 0.25 1.22 No peeling, no shedding Example 3 0.29 1.24 No peeling, no shedding Comparative Example 1 0.35 1.32 Peeling, shedding Comparative Example 2 0.39 1.35 Peeling, shedding

Claims

1. A tin plating process for electronic components, characterized in that: The following steps are involved: (1) The surface of the electronic component is subjected to degreasing, ultrasonic degreasing, water washing, pickling activation, and water washing to obtain a clean surface of the electronic component for standby use; (2) preparing an electroplating solution; (3) Tin plating: placing the electronic component described in step (1) in the electroplating solution described in step (2) for electroplating, and then washing and drying to obtain an electronic component with a tinned surface; The electroplating solution in step (2) comprises the following raw materials: 30-60 g / L of tin salt, 120-150 g / L of phosphate, 300-400 g / L of complexing agent, 5-15 g / L of polyoxyethylene compound, 0.8-1.2 g / L of polyethylene glycol, 2-3 g / L of carbon-carbon triple bond-containing compound, 2-3 g / L of propane sulfonic acid compound, 3-7 g / L of stabilizer, and 2-4 g / L of auxiliary agent; The tin salt includes tin methanesulfonate; The complexing agent comprises triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea; the mass ratio of triethylenetetraaminehexaacetic acid, methanesulfonic acid and thiourea is (2-4): (7-10): (2-4); The polyoxyethylene compounds include polyoxyethylene sorbitan fatty acid esters; The carbon-carbon triple bond-containing compound includes N,N-diethylpropargylamine; the propane sulfonic acid compound includes sodium 3-(benzothiazole-2-mercapto)-propane sulfonate and pyridinium hydroxypropane sulfonate; the mass ratio of N,N-diethylpropargylamine, sodium 3-(benzothiazole-2-mercapto)-propane sulfonate and pyridinium hydroxypropane sulfonate is (2-3):(1-2):(1-2); The stabilizer includes hydroquinone and ascorbic acid; The auxiliary agents include succinic acid and trimethylacetic acid.

2. The electronic component electrotin plating process according to claim 1, characterized in that: The frequency of the defatting ultrasound in step (1) is 200-500 Hz, and the ultrasound time is 2-4 minutes.

3. The electronic component electrotin plating process according to claim 1, characterized in that: The electroplating time in step (3) is 5-20 minutes.