An electroplating process for improving the lifespan of LED lamp beads

Abstract

The present invention relates to the field of electroplating, and particularly to an electroplating process for improving the lifespan of LED lamp beads. An electroplating process for improving the lifespan of LED lamp beads comprises the following steps: S1, pretreatment; S2, plating with alkaline copper: immersing the pretreated LED lamp bead substrate in an alkaline copper plating solution for electroplating; S3, plating with nickel: immersing the LED lamp bead substrate after plating with alkaline copper in a nickel plating solution for electroplating; S4, plating with palladium: immersing the LED lamp bead substrate after plating with nickel in a palladium plating solution for electroplating; S5, selectively plating silver on the functional area of the LED lamp bead using a silver plating mold; S6, post-treatment. In this application, plating with palladium is added between the steps of plating with nickel and plating with silver, that is, a palladium layer is added between the silver coating and the nickel coating. The nickel / palladium / silver coating structure has stronger stability, and the silver layer is not easily damaged, thereby improving the service life of the LED lamp beads.

Description

Technical Field

[0001] The present invention relates to the field of electroplating, and particularly to an electroplating process for improving the service life of LED lamp beads. Background Art

[0002] LED lamp beads have the advantages of small volume, large scattering angle, good luminous uniformity, high reliability, etc., and the luminous colors include various colors including white light. Therefore, they are widely used in various electronic products. The base materials of LED lamp beads are copper and its alloys and iron and its alloys. Since these materials are relatively active, they are prone to aging and oxidation after long-term use, and the LED light-emitting chips cannot be directly welded on them. Therefore, these base materials need to be electroplated on the surface to deposit a layer of metal with weaker activity to prevent the LED lamp beads from aging or being oxidized during use, which affects the service life of the LED lamp beads.

[0003] Currently, the electroplating process for LED brackets is a multi-layer electroplating process, and there are mainly two electroplating processes. One electroplating process is: degreasing → activation → plating alkaline copper → plating acid copper → plating nickel → plating silver → post-treatment, and its silver plating structure is copper / nickel / silver; another electroplating process is: degreasing → activation → plating alkaline copper → plating acid copper → plating alkaline copper → plating silver → post-treatment, and its silver plating structure is copper / silver.

[0004] During the research process, the applicant found that in the above electroplating process, the silver layers of the LED lead frames manufactured by the copper / nickel / silver silver plating structure and the copper / silver silver plating structure are easily damaged, and the service life of the LED lamp beads is relatively short. Summary of the Invention

[0005] In order to improve the service life of LED lamp beads, the present application provides an electroplating process for improving the service life of LED lamp beads.

[0006] In the first aspect, the present application provides an electroplating process for improving the service life of LED lamp beads, which is realized by the following technical solutions: An electroplating process for improving the service life of LED lamp beads includes the following steps:

[0007] S1. Pretreatment;

[0008] S2. Plating alkaline copper: Immerse the LED lamp bead base material after pretreatment into the alkaline copper plating solution, with a current density of 3 - 7 amperes per square decimeter, and electro-deposit for 3 - 7 s;

[0009] S3. Plating nickel: Immerse the LED lamp bead base material after plating alkaline copper into the nickel plating solution, with a current density of 4 - 8 amperes per square decimeter, and electro-deposit for 10 - 20 s;

[0010] S4. Plating palladium: Immerse the LED lamp bead base material after plating nickel into the palladium plating solution, with a current density of 0.6 - 2 amperes per square decimeter, and electro-deposit for 3 - 5 s;

[0011] S5. Selectively silver-plate the functional area of the LED lamp bead using a silver-plated mold: Put the palladium-plated LED lamp bead substrate into the silver-plated mold and place it in the silver-plating solution. With a current density of 20 - 50 amperes per square decimeter, perform electro-deposition for 1 - 3 s.

[0012] S6. Post-treatment.

[0013] By adopting the above technical solution, adding palladium plating between the nickel plating and silver plating steps, that is, adding a palladium layer between the silver layer and the nickel layer, the coating structure stability of nickel / palladium / silver is stronger, and the silver layer is not easily damaged, thereby improving the service life of the LED lamp bead. The electroplating process of the nickel / palladium / silver coating structure corresponds to twice the service life of the LED lamp bead compared to the electroplating processes of the copper / nickel / silver coating structure and the copper / silver coating structure.

[0014] In this application, the pre-treatment includes a degreasing step and an activation step. Degreasing removes the oil stains and other abnormalities on the surface of the LED lamp bead substrate, improves the adhesion between the subsequent coating and the substrate, and improves the quality of the coating. Activation can remove the oxide film on the surface of the LED lamp bead substrate, improve the adhesion between the coating and the substrate, and activation can neutralize the alkaline film remaining on the surface of the material. The activated LED lamp bead electroplated with alkaline copper has a leveling effect and at the same time improves the adhesion between the coating and the substrate.

[0015] In this application, the pH of the alkaline copper plating solution is 10 - 12.

[0016] In this application, the alkaline copper plating solution is composed of cuprous cyanide and sodium cyanide or potassium cyanide.

[0017] In the alkaline copper plating solution of this application, the concentration of cuprous cyanide is preferably 85 - 110 g / L. If the content of cuprous cyanide is too low, the content of copper ions is too low, affecting the electroplating efficiency and the leveling effect is poor, but if the content of copper ions is too high, it is easy to have poor coating in the high area. Sodium cyanide or potassium cyanide is a complexing agent for stabilizing the normal operation of the alkaline copper plating solution. CN - not only complexes copper ions but also exists alone in the plating solution in a free state. The content of free CN - in the plating solution is preferably 30 - 60 g / L. If the content of free CN - is too low, it cannot ensure fine crystal grains of the coating and at the same time affects the normal dissolution of the anode, but if the content of free CN - is too high, it will also affect the electroplating efficiency.

[0018] In this application, the thickness of the copper coating corresponding to the electroplating with alkaline copper is 25 - 35 micro-inches; preferably, the thickness of the copper coating corresponding to the electroplating with alkaline copper is 30 micro-inches.

[0019] Plating nickel on the alkaline copper coating can block the thermal migration of copper.

[0020] In this application, the composition of the nickel plating solution is as follows: nickel sulfamate 450 - 500 mL / L, nickel chloride 10 - 15 g / L, boric acid 35 - 45 g / L; preferably, the composition of the nickel plating solution is: nickel sulfamate 500 mL / L, nickel chloride 15 g / L, boric acid 40 g / L.

[0021] In this application, nickel sulfamate and nickel chloride can introduce nickel ions. However, if the nickel ion concentration is too low, it will affect the electroplating efficiency and the coating crystals will be coarse. But if the nickel ion concentration is too high, coating defects are likely to occur in the high-current area. The main function of nickel chloride is to increase conductivity and promote anode dissolution. However, if the concentration of nickel chloride is too high, it will reduce the ductility of the nickel layer, and the LED lamp beads are prone to cracking when bent. Boric acid acts as a buffer to prevent nickel deposition at a certain point and improves the uniformity of the nickel layer coating. If the concentration of boric acid is too high, it will cause changes in the coating crystals.

[0022] Preferably, the thickness of the nickel coating corresponding to the nickel plating is 35 - 45 microinches; more preferably, the thickness of the nickel coating corresponding to the nickel plating is 40 microinches.

[0023] Preferably, the composition of the palladium plating solution is as follows: palladium tetraammine chloride 9 - 14 g / L, conductive salt 30 - 60 g / L, polyethyleneimine 5 - 10 g / L, complexing agent 5 - 10 g / L, bromine compound 3 - 5 g / L, phosphoric acid 2 - 4 g / L.

[0024] By adopting the above technical solution, the addition of polyethyleneimine and bromine compound, through their combined action, improves the stability of the palladium plating solution and also improves the compactness of the palladium coating, thereby further enhancing the structural stability of the nickel / palladium / silver coating.

[0025] Preferably, the composition of the palladium plating solution is as follows: palladium tetraammine chloride 12 g / L, conductive salt 50 g / L, polyethyleneimine 7 g / L, complexing agent 7 g / L, bromine compound 4 g / L, phosphoric acid 3 g / L.

[0026] By adopting the above technical solution, the palladium plating solution with the above composition has better structural stability for the nickel / palladium / silver coating, and the LED lamp beads have a longer service life.

[0027] Preferably, the bromine compound is cetyltrimethylammonium bromide.

[0028] By adopting the above technical solution, the long carbon chain of cetyltrimethylammonium bromide improves the wettability of the palladium plating solution on the nickel plating layer, enhances the adhesion between the palladium plating layer and the nickel plating layer, thereby improving the structural stability of the nickel / palladium / silver coating and making the LED lamp beads have a longer service life.

[0029] Preferably, the polyethyleneimine is hyperbranched, alkoxylated polyethyleneimine and / or ethylenediamine-capped polyethyleneimine.

[0030] By adopting the above technical solutions, the hyperbranched, alkoxylated polyethyleneimine is a modified polyethyleneimine, and its hyperbranched structure further improves the stability of the palladium plating solution; the polyethyleneimine capped with ethylenediamine has better complexing stability and improves the compactness of the palladium coating.

[0031] Preferably, the polyethyleneimine is formed by mixing hyperbranched, alkoxylated polyethyleneimine and polyethyleneimine capped with ethylenediamine in a mass ratio of 1:(0.6 - 0.8).

[0032] More preferably, the polyethyleneimine is formed by mixing hyperbranched, alkoxylated polyethyleneimine and polyethyleneimine capped with ethylenediamine in a mass ratio of 1:0.7.

[0033] By adopting the above technical solutions, the hyperbranched, alkoxylated polyethyleneimine and the polyethyleneimine capped with ethylenediamine are compounded. Especially when the mass ratio of the hyperbranched, alkoxylated polyethyleneimine to the polyethyleneimine capped with ethylenediamine is 1:0.7, the two act together to further improve the structural stability of the nickel / palladium / silver coating, thereby improving the lifespan of the LED lamp beads.

[0034] Preferably, the thickness of the palladium coating corresponding to the palladium plating is 0.5 - 1 microinch; more preferably, the thickness of the palladium coating corresponding to the palladium plating is 0.8 microinch.

[0035] LED lamp beads require metal materials with optimal electrical conductivity, thermal conductivity, and light reflection. Silver has a small resistivity, a large thermal conductivity coefficient, a large reflectivity within the visible light spectrum, and the cost of silver is lower than that of gold. In this application, the vacant positions of the silver plating mold correspond to the functional areas of the silver plating surface, and the masking strips of the silver plating mold correspond to the non-functional areas of the silver plating surface. Selective silver plating does not require subsequent silver removal steps, the post-treatment steps are simple, the cost is saved, and the waste of silver is avoided.

[0036] In this application, the silver plating solution is composed of silver cyanide and potassium cyanide or sodium cyanide.

[0037] Preferably, the thickness of the silver coating corresponding to the silver plating is 40 - 120 microinches.

[0038] In this application, the post-treatment includes an electrolytic cleaning step, an anti-oxidation step, a water washing step, and a drying step. Since silver is prone to discoloration in the atmosphere, after the LED lamp beads are electroplated and before encapsulation, they will be exposed to the air. After silver plating, an anti-oxidation step is required to protect the silver layer. The anti-oxidation step uses a protective water to form a nanoscale organic solid film on the surface of the silver layer, which shields the corrosive medium, thereby achieving the effect of protecting the silver coating.

[0039] In summary, this application has the following beneficial effects:

[0040] 1. This application adds palladium plating between the nickel plating and silver plating steps, that is, adds a palladium layer between the silver layer and the nickel layer. The nickel / palladium / silver coating structure has stronger stability, and the silver layer is not easily damaged, thereby improving the service life of the LED lamp beads. The electroplating process of the nickel / palladium / silver coating structure corresponds to twice the service life of the LED lamp beads compared to the electroplating processes of the copper / nickel / silver coating structure and the copper / silver coating structure.

[0041] 2. By adding polyethyleneimine and bromine compounds to the palladium plating solution, this application improves the stability of the palladium plating solution through their combined action, and can also improve the compactness of the palladium coating, thereby further enhancing the structural stability of the nickel / palladium / silver coating.

[0042] 3. By using cetyltrimethylammonium bromide, this application improves the wettability of the palladium plating solution on the nickel plating layer, enhances the adhesion between the palladium plating layer and the nickel plating layer, thereby improving the structural stability of the nickel / palladium / silver coating and making the LED lamp beads have a longer service life.

[0043] 4. By compounding hyperbranched, alkoxylated polyethyleneimine and ethylenediamine-capped polyethyleneimine, this application further improves the structural stability of the nickel / palladium / silver coating through their combined action, thereby increasing the service life of the LED lamp beads. Description of the Drawings

[0044] Figure 1 SEM image of the coating obtained by the electroplating process of Example 1.

[0045] Figure 2 SEM image of the coating obtained by the electroplating process of Comparative Example 1. Detailed Description of the Embodiments

[0046] The following further elaborates on this application in conjunction with the embodiments.

[0047] Preparation Examples

[0048] Preparation Example 1 provides an alkaline copper plating solution, and its preparation steps are as follows:

[0049] Mix 100 g of cuprous cyanide, 180 g of sodium cyanide, and 500 mL of deionized water evenly, and then add deionized water to make up to 1 L to obtain the alkaline copper plating solution.

[0050] Preparation Example 2 provides a nickel plating solution, and its preparation steps are as follows:

[0051] Mix 500 mL of nickel sulfamate, 15 g of nickel chloride, 40 g of boric acid, and 300 mL of deionized water evenly, and then add deionized water to make up to 1 L to obtain the nickel plating solution.

[0052] Preparation Examples 3 - 11 provide a palladium plating solution. The following takes Preparation Example 3 as an example for illustration.

[0053] The palladium plating solution provided in Preparation Example 3 was prepared as follows:

[0054] 9 g of palladium tetraammine chloride, 30 g of potassium chloride, 5 g of polyethyleneimine SP-018 (purchased from Wuhan Zhuochuang Yuanhang Chemical Co., Ltd.), 5 g of ethylenediamine, 3 g of ammonium bromide, 2 g of phosphoric acid, and 400 mL of deionized water were mixed evenly, and then deionized water was added to make up to 1 L to obtain the palladium plating solution.

[0055] Preparation Examples 4-5 were different from Preparation Example 3 only in that the amounts of the raw materials for preparing the palladium plating solution were different, as shown in Table 1 specifically.

[0056] Table 1 Amounts of the raw materials for preparing the palladium plating solutions in Preparation Examples 3-5

[0057]

[0058] Preparation Example 6 was different from Preparation Example 5 only in that ammonium bromide was replaced with cetyltrimethylammonium bromide in equal mass.

[0059] Preparation Example 7 was different from Preparation Example 6 only in that polyethyleneimine SP-018 was replaced with hyperbranched, alkoxylated polyethyleneimine (model number HP 20, purchased from Shenzhen Xianzhi Chemical Technology Co., Ltd.) in equal mass.

[0060] Preparation Example 8 was different from Preparation Example 6 only in that polyethyleneimine SP-018 was replaced with ethylenediamine-terminated polyethyleneimine (purchased from Wuhan Kemike Biopharmaceutical Technology Co., Ltd.) in equal mass.

[0061] Preparation Example 9 was different from Preparation Example 6 only in that polyethyleneimine SP-018 was replaced with a mixture of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine-terminated polyethyleneimine, and the mass ratio of hyperbranched, alkoxylated polyethyleneimine to ethylenediamine-terminated polyethyleneimine was 1:0.6.

[0062] Preparation Example 10 was different from Preparation Example 9 only in that the mass ratio of hyperbranched, alkoxylated polyethyleneimine to ethylenediamine-terminated polyethyleneimine was 1:0.8.

[0063] Preparation Example 11 was different from Preparation Example 9 only in that the mass ratio of hyperbranched, alkoxylated polyethyleneimine to ethylenediamine-terminated polyethyleneimine was 1:0.7.

[0064] Preparation Example 12 provided a silver plating solution, and its preparation steps were as follows:

[0065] 100 g of silver cyanide, 70 g of potassium cyanide, and 600 mL of deionized water were mixed evenly, and then deionized water was added to make up to 1 L to obtain the silver plating solution.

[0066] Preparation Example 13 provides an electrolytic stripping agent solution, and its preparation steps are as follows:

[0067] S1. At 30°C, 200 g of potassium hydroxide, 200 g of potassium carbonate, 300 g of glucose, and 300 g of basic lead carbonate are mixed evenly by dry mixing at a stirring speed of 100 rpm to obtain a powdery electrolytic stripping agent;

[0068] S2. Deionized water is added to the above electrolytic stripping agent to prepare a 20 wt% electrolytic stripping agent solution.

[0069] Preparation Example 14 provides a nickel strike solution, and its preparation steps are as follows:

[0070] 400 g of nickel sulfate, 40 g / L of nickel chloride, 40 g / L of boric acid, and 300 mL of deionized water are mixed evenly, and then deionized water is added to make up to 1 L to obtain a nickel strike solution.

[0071] Preparation Example 15 provides an acid copper plating solution, and its preparation steps are as follows:

[0072] 180 g of copper sulfate, 60 g of sulfuric acid, 164.85 mg of sodium chloride, 0.35 mL of acid copper 380 crystal fining agent, 0.17 mL of acid copper 380 brightening agent, 0.12 mL of acid copper 380 leveling agent, and 500 mL of deionized water are mixed evenly, and then deionized water is added to make up to 1 L to obtain a nickel strike solution;

[0073] Among them, the acid copper 380 crystal fining agent, the acid copper 380 brightening agent, and the acid copper 380 leveling agent are all purchased from Atotech (China) Chemical Co., Ltd.

[0074] In this application, the alkaline copper plating solution, the nickel plating solution, and the silver plating solution include but are not limited to those prepared in the above preparation examples, as long as they are suitable for the electroplating process of the LED lamp bead life. In addition, the electrolytic stripping agent solution used for electrolytic degreasing also includes but is not limited to those prepared in the above preparation examples.

[0075] Preparation of Comparative Examples

[0076] Preparation of Comparative Examples 1-4 provides a palladium plating solution.

[0077] The difference between Preparation of Comparative Example 1 and Preparation Example 3 is only that: polyethyleneimine SP-018 is replaced with ethylenediamine in equal mass.

[0078] The difference between Preparation of Comparative Example 2 and Preparation Example 3 is only that: ammonium bromide is replaced with potassium chloride in equal mass.

[0079] The difference between Preparation of Comparative Example 3 and Preparation Example 3 is only that: polyethyleneimine SP-018 is replaced with ammonium bromide in equal mass.

[0080] Prepare Comparative Example 4, which is different from Preparation Example 3 only in that: ammonium bromide is replaced with polyethyleneimine SP-018 in equal mass.

[0081] Example

[0082] Example 1 provides an electroplating process for improving the lifespan of LED lamp beads. The following takes Example 1 as an illustration.

[0083] The electroplating process for improving the lifespan of LED lamp beads provided by Example 1 has the following steps:

[0084] S1. Pretreatment

[0085] S11. Electro-degreasing: Use the LED lamp bead substrate as the cathode, a 364 stainless steel plate as the anode, an aqueous solution of degreasing powder with a mass fraction of 10wt% (purchased from Zhongshan Jindun Washing Materials Co., Ltd.) as the electrolyte, and pass an electric current at a density of 2 amperes per square decimeter at 50°C for 10 s to remove the oil stains on the surface of the LED lamp bead substrate;

[0086] S12. Three-stage water washing: Wash three times with deionized water to remove the residue of the degreasing powder aqueous solution;

[0087] S13. Activation: Immerse the electro-degreased LED lamp bead substrate in 10wt% sulfuric acid for 5 s;

[0088] S14. Three-stage water washing: Wash three times with deionized water to remove the residue of sulfuric acid;

[0089] S2. Alkaline copper plating

[0090] S21. Immerse the pretreated LED lamp bead substrate in the alkaline copper plating solution (from Preparation Example 1), and electro-deposit at a current density of 3 amperes per square decimeter at 50°C for 7 s;

[0091] S22. Three-stage water washing: Wash three times with deionized water to remove the residue of the alkaline copper plating solution;

[0092] S3. Nickel plating

[0093] S31. Immerse the LED lamp bead substrate after alkaline copper plating in the nickel plating solution (from Preparation Example 2), and electro-deposit at a current density of 4 amperes per square decimeter at 50°C for 20 s;

[0094] S32. Three-stage water washing: Wash three times with deionized water to remove the residue of the nickel plating solution;

[0095] S4. Palladium plating

[0096] S41. Immerse the LED lamp bead substrate after nickel plating in the palladium plating solution (from Preparation Example 3), and electro-deposit at a current density of 0.6 amperes per square decimeter at 40°C for 5 s;

[0097] S42. Three - stage water washing: Wash three times with deionized water to remove the residue of the palladium plating solution;

[0098] S5. Selectively silver - plate the functional area of the LED lamp bead using a silver - plating mold

[0099] S51. Put the palladium - plated LED lamp bead substrate into a silver - plating mold (the vacant positions of the silver - plating mold correspond to the functional areas of the silver - plating surface, and the masking strips of the silver - plating mold correspond to the non - functional areas of the silver - plating surface), place it in a silver - plating solution (from Preparation Example 12), and perform electro - deposition at 40 °C with a current density of 20 amperes per square decimeter for 3 s;

[0100] S52. Three - stage water washing: Wash three times with deionized water to remove the residue of the silver - plating solution;

[0101] S6. Post - treatment

[0102] S61. Electrolytic cleaning: Use the silver - plated LED lamp bead substrate as the cathode, a 364 stainless steel plate as the anode, and an electrolytic stripping agent solution (from Preparation Example 13) as the electrolyte. Pass an electric current at 40 °C with a current density of 1 ampere per square decimeter for 10 s to clean the silver - plated LED lamp bead substrate;

[0103] S62. Three - stage water washing: Wash three times with deionized water to remove the residue of the electrolytic stripping agent solution;

[0104] S63. Anti - oxidation: Immerse the electrolytically cleaned LED lamp bead substrate in an anti - oxidant solution PET - 880 (purchased from METALOR) for 15 s;

[0105] S64. Three - stage water washing: Wash three times with deionized water to remove the anti - oxidant solution PET - 880;

[0106] S65. Dry.

[0107] Example 2 - 3 is different from Example 1 only in that: the current density and electro - plating time in each step of the electro - plating process are different, as shown in Table 2 specifically.

[0108] Table 2 Current density and electro - plating time in each step of Examples 1 - 3

[0109]

[0110] Examples 4 - 15 are different from Example 3 only in that: the sources of the palladium plating solution are different, as shown in Table 3 specifically.

[0111] Table 3 Sources of the palladium plating solution in Examples 3 - 15

[0112]

[0113] Comparative example

[0114] The electroplating process for improving the lifespan of LED lamp beads provided by Comparative Example 1 has the following steps:

[0115] S1. Pretreatment

[0116] S11. Electro-degreasing: Using the LED lamp bead substrate as the cathode, a 364 stainless steel plate as the anode, and an aqueous solution of degreasing powder with a mass fraction of 10 wt% (purchased from Zhongshan Jindun Washing Materials Co., Ltd.) as the electrolyte, passing an electric current at a density of 2 amperes per square decimeter at 50 °C for 10 s to remove the oil stains on the surface of the LED lamp bead substrate;

[0117] S12. Three-stage water washing: Washing three times with deionized water to remove the residue of the degreasing powder aqueous solution;

[0118] S13. Activation: Immersing the electro-degreased LED lamp bead substrate in 10 wt% sulfuric acid for 5 s;

[0119] S14. Three-stage water washing: Washing three times with deionized water to remove the residue of sulfuric acid;

[0120] S2. Bottom nickel plating

[0121] S21. Immersing the activated LED lamp bead substrate in the bottom nickel plating solution (from Preparation Example 14), electro-depositing at a current density of 4 amperes per square decimeter at 50 °C for 20 s;

[0122] S22. Three-stage water washing: Washing three times with deionized water to remove the residue of the bottom nickel plating solution;

[0123] S3. Alkaline copper plating

[0124] S31. Immersing the bottom nickel-plated LED lamp bead substrate in the alkaline copper plating solution (from Preparation Example 1), electro-depositing at a current density of 3 amperes per square decimeter at 50 °C for 7 s;

[0125] S32. Three-stage water washing: Washing three times with deionized water to remove the residue of the alkaline copper plating solution;

[0126] S4. Acid copper plating

[0127] S41. Immersing the alkaline copper-plated LED lamp bead substrate in the acid copper plating solution (from Preparation Example 15), electro-depositing at a current density of 5 amperes per square decimeter at 20 °C for 60 s;

[0128] S42. Three-stage water washing: Washing three times with deionized water to remove the residue of the acid copper plating solution;

[0129] S5. Nickel plating

[0130] S51. Immersing the acid copper-plated LED lamp bead substrate in the nickel plating solution (from Preparation Example 2), electro-depositing at a current density of 4 amperes per square decimeter at 50 °C for 20 s;

[0131] S52. Three - stage water washing: Wash three times with deionized water to remove the residue of nickel plating solution.

[0132] S6. Selectively silver - plate the functional area of the LED lamp bead using a silver - plating mold.

[0133] S61. Put the nickel - plated LED lamp bead substrate into a silver - plating mold (the vacant positions of the silver - plating mold correspond to the functional areas of the silver - plated surface, and the masking strips of the silver - plating mold correspond to the non - functional areas of the silver - plated surface), place it in the silver - plating solution (from Preparation Example 12), and perform electro - deposition at 40°C with a current density of 20 amperes per square decimeter for 3 s.

[0134] S62. Three - stage water washing: Wash three times with deionized water to remove the residue of silver - plating solution.

[0135] S7. Post - treatment

[0136] S71. Electrolytic cleaning: Use the silver - plated LED lamp bead substrate as the cathode, a 364 stainless steel plate as the anode, and an electrolytic stripping agent solution (from Preparation Example 13) as the electrolyte. Pass an electric current at 40°C with a current density of 1 ampere per square decimeter for 10 s to clean the silver - plated LED lamp bead substrate.

[0137] S72. Three - stage water washing: Wash three times with deionized water to remove the residue of the electrolytic stripping agent solution.

[0138] S73. Anti - oxidation: Immerse the electrolytically cleaned LED lamp bead substrate in the anti - oxidant solution PET - 880 for 15 s.

[0139] S74. Three - stage water washing: Wash three times with deionized water to remove the anti - oxidant solution PET - 880.

[0140] S75. Dry.

[0141] Performance detection test

[0142] For the electroplated LED lamp beads of Examples 1 - 15 and Comparative Example 1 of this application, the following performance detections are carried out.

[0143] 1. Service life: Turn on the electroplated LED lamp bead, light it in an environment with a temperature of 85°C and an air relative humidity of 85%, record the time when the LED lamp bead starts to turn black, and the test results are shown in Table 4.

[0144] 2. Adhesion between the coating and the substrate: Test the adhesion between the coating and the substrate of the electroplated LED lamp bead through a cross - cut test. The specific test method is as follows: Draw a "well" shape on the test sample, then stick it with 3M tape, and then observe under a microscope magnified 20 times to check if there is peeling. If there is no peeling, it is recorded as qualified; if there is peeling, it is unqualified. The test results are shown in Table 4.

[0145] 3. Ductility: The ductility of the plating layer of the electroplated LED lamp beads was tested by bending. The specific test method was as follows: Bend the electroplated LED lamp beads to 180°, then compact them with a pair of needle-nose pliers, and then observe under a microscope magnified 50 times to check for peeling or flaking. If there is no peeling and no flaking, it is recorded as qualified; if there is peeling or flaking, it is recorded as unqualified. The test results are shown in Table 4.

[0146] Table 4 Test Data

[0147] Service life Bonding strength Ductility Example 1 2000h Qualified Qualified Example 2 2200h Qualified Qualified Example 3 2300h Qualified Qualified Example 4 2500h Qualified Qualified Example 5 2600h Qualified Qualified Example 6 2800h Qualified Qualified Example 7 3100h Qualified Qualified Example 8 3000h Qualified Qualified Example 9 3500h Qualified Qualified Example 10 3400h Qualified Qualified Example 11 3600h Qualified Qualified Example 12 2000h Qualified Qualified Example 13 2100h Qualified Qualified Example 14 2000h Qualified Qualified Example 15 2200h Qualified Qualified Comparative Example 1 1000h Qualified Qualified

[0148] The present application will be described in detail below in conjunction with the data in Table 4.

[0149] From the test data of Example 1 and Comparative Example 1, the lifespan of the LED lamp beads with palladium plating added between the nickel plating and silver plating steps is twice that of the LED lamp beads without palladium plating.

[0150] From the test data of Examples 3 and 12 - 15, the addition of polyethyleneimine and bromine compounds increased the service life of the LED lamp beads. This is because the combined action of polyethyleneimine and bromine compounds improved the stability of the palladium plating solution and also enhanced the compactness of the palladium plating layer, thereby further improving the structural stability of the nickel / palladium / silver plating layer.

[0151] From the test data of Examples 5 and 6, ammonium bromide was used in Example 5, and cetyltrimethylammonium bromide was used in Example 6. The time when the electroplated LED lamp beads in Example 6 started to turn black was longer than that in Example 5. This is because cetyltrimethylammonium bromide improved the wettability of the palladium plating solution on the nickel plating layer and enhanced the adhesion between the palladium plating layer and the nickel plating layer, resulting in a longer lifespan of the LED lamp beads.

[0152] From the test data of Examples 6, 7, and 8, polyethyleneimine SP - 018 was used in Example 6, hyperbranched and alkoxylated polyethyleneimine was used in Example 7, and ethylenediamine - terminated polyethyleneimine was used in Example 8. The service life of the LED lamp beads in Example 7 was longer than that in Example 6. This is because the hyperbranched structure of hyperbranched and alkoxylated polyethyleneimine further improved the stability of the palladium plating solution, thereby increasing the service life of the LED lamp beads; the service life of the LED lamp beads in Example 8 was longer than that in Example 6. This is because ethylenediamine - terminated polyethyleneimine enhanced the compactness of the palladium plating layer, thereby increasing the service life of the LED lamp beads.

[0153] From the test data of Examples 7, 8, and 9, the compounding of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine-terminated polyethyleneimine further improves the structural stability of the nickel / palladium / silver coating, thereby increasing the service life of the LED lamp beads.

[0154] This specific embodiment is only an interpretation of the present application and is not a limitation thereof. After reading this specification, those skilled in the art can make modifications to this embodiment that do not contribute creatively as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. An electroplating process for improving the lifespan of LED lamp beads, characterized in that, It includes the following steps: S1. Pretreatment; S2. Alkaline copper plating: Immerse the pretreated LED lamp bead substrate into the alkaline copper plating solution, with a current density of 3 - 7 amperes per square decimeter, and perform electrodeposition for 3 - 7 s; S3. Nickel plating: Immerse the LED lamp bead substrate after alkaline copper plating into the nickel plating solution, with a current density of 4 - 8 amperes per square decimeter, and perform electrodeposition for 10 - 20 s; S4. Palladium plating: Immerse the LED lamp bead substrate after nickel plating into the palladium plating solution, with a current density of 0.6 - 2 amperes per square decimeter, and perform electrodeposition for 3 - 5 s; The composition of the palladium plating solution is: 9 - 14 g / L of tetraamminepalladium chloride, 30 - 60 g / L of conductive salt, 5 - 10 g / L of polyethyleneimine, 5 - 10 g / L of complexing agent, 3 - 5 g / L of cetyltrimethylammonium bromide, 2 - 4 g / L of phosphoric acid; The polyethyleneimine is composed of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine - terminated polyethyleneimine mixed in a mass ratio of 1:(0.6 - 0.8); S5. Selective silver plating on the functional area of the LED lamp bead using a silver plating mold: Put the LED lamp bead substrate after palladium plating into the silver plating mold and place it in the silver plating solution, with a current density of 20 - 50 amperes per square decimeter, and perform electrodeposition for 1 - 3 s; S6. Post - treatment.

2. The electroplating process for improving the lifespan of LED lamp beads according to claim 1, characterized in that, The composition of the palladium plating solution is: 12 g / L of tetraamminepalladium chloride, 50 g / L of conductive salt, 7 g / L of polyethyleneimine, 7 g / L of complexing agent, 4 g / L of cetyltrimethylammonium bromide, 3 g / L of phosphoric acid. The polyethyleneimine is composed of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine - terminated polyethyleneimine mixed in a mass ratio of 1:0.

7.

3. The electroplating process for improving the lifespan of LED lamp beads according to claim 1, characterized in that The thickness of the palladium plating corresponding to the palladium coating is 0.5 - 1 micro - inch; The thickness of the nickel plating corresponding to the nickel coating is 35 - 45 micro - inches.

4. A plating process for improving the lifespan of LED lamp beads according to claim 1, characterized in that, The thickness of the silver plating corresponding to the silver coating is 40 - 120 micro - inches.

5. A palladium plating solution, characterized in that, The composition of the palladium plating solution is: 9 - 14 g / L of tetraamminepalladium chloride, 30 - 60 g / L of conductive salt, 5 - 10 g / L of polyethyleneimine, 5 - 10 g / L of complexing agent, 3 - 5 g / L of cetyltrimethylammonium bromide, 2 - 4 g / L of phosphoric acid; The polyethyleneimine is composed of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine - terminated polyethyleneimine mixed in a mass ratio of 1:(0.6 - 0.8).

6. The palladium plating solution according to claim 5, characterized in that, The polyethyleneimine is composed of hyperbranched, alkoxylated polyethyleneimine and ethylenediamine - terminated polyethyleneimine mixed in a mass ratio of 1:0.7.

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