A cyanide-free electroplating solution capable of electroplating both soft gold and hard gold

Abstract

The application discloses a cyanide-free electroplating solution capable of electroplating soft gold and hard gold, which comprises a gold sulfite, a complexing agent, a stabilizer, a hardness regulator, a conductive salt and a pH buffer. The cyanide-free electroplating solution provided by the application can be used to electroplate hard gold or soft gold plating layer by adjusting the content of the hardness regulator in the solution, and the cyanide-free electroplating solution is neutral and slightly acidic, does not contain toxic elements such as Tl, Pb and As, is environmentally friendly, and is suitable for wide application. In addition, the cyanide-free electroplating solution has a current efficiency greater than 98%, less side reactions in the electroplating process, and a dense gold plating layer.

Description

Technical Field

[0001] The invention relates to the technical field of cyanide-free electroplating, and in particular to a cyanide-free electroplating solution capable of electroplating soft gold and hard gold. Background Art

[0002] Gold plating is used as a decorative coating due to its strong resistance to discoloration. Furthermore, due to its excellent properties such as corrosion resistance, wear resistance, low contact resistance, and good solderability, it can also be used as a functional coating and is widely used in printed circuit boards, semiconductor electronic component manufacturing, and cutting-edge military equipment.

[0003] Commonly used gold electroplating processes include cyanide electroplating and cyanide-free electroplating. Regardless of whether it is cyanide electroplating or cyanide-free electroplating, the hardness of the gold plating layer can be divided into soft gold and hard gold. Soft gold plating is often used in the semiconductor field for gold bumps, wire bonding, etc., and the hardness is not greater than 100HV (usually after annealing). Hard gold plating is often used as decorative plating, connector functional plating, etc., and generally requires a hardness greater than 100HV. Existing public technology has developed different electroplating solution systems for soft gold and hard gold. For example, Chinese patent application CN101235524A discloses a soft gold electroplating solution system with the addition of grain adjusters such as Tl, Pb, and As. The hardness of the gold plating layer before annealing is 105-123HV, and after annealing at 300°C, the hardness is only 46-48HV. Chinese patent application CN112239875A develops a hard gold electroplating solution system, which improves the hardness of the gold plating layer by adding polyethyleneimine with a molecular weight of 300-1500, and the plating hardness is between 110-150HV.

[0004] Currently, there is no cyanide-free electroplating solution that can achieve gold plating with different hardness by adjusting a certain component in the electroplating solution. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a cyanide-free electroplating solution that can electroplate soft gold and hard gold.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A cyanide-free electroplating solution capable of electroplating soft gold and hard gold comprises a gold sulfite, a complexing agent, a stabilizer, a hardness regulator, a conductive salt and a pH buffer;

[0008] Wherein, the hardness regulator is a single long-chain alkyl quaternary ammonium salt compound, and its structural formula is shown in Formula I:

[0009]

[0010] n=4-8.

[0011] Furthermore, the hardness regulator is one of decanyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide.

[0012] Furthermore, when used for electroplating soft gold, the content of the hardness regulator is 0.1 mg / L-2 mg / L; when used for electroplating hard gold, the content of the hardness regulator is 3 mg / L-15 mg / L.

[0013] Furthermore, the gold sulfite is one of sodium gold sulfite, potassium gold sulfite or ammonium gold sulfite.

[0014] Furthermore, the content of the gold sulfite in the cyanide-free electroplating solution is 5 g / L-20 g / L, calculated as gold element.

[0015] Furthermore, the complexing agent includes a main complexing agent and an auxiliary complexing agent, the main complexing agent is one of sodium sulfite, potassium sulfite or ammonium sulfite, and the auxiliary complexing agent is one of ethylenediamine, propylenediamine or diethylenetriamine; the content of the main complexing agent is 15g / L-130g / L; the content of the auxiliary complexing agent is 10g / L-30g / L.

[0016] Furthermore, the stabilizer is EDTA-2Na; the content of the stabilizer is 20g / L-50g / L.

[0017] Furthermore, the conductive salt is one of sodium carbonate, potassium nitrate, sodium chloride or potassium chloride; and the content of the conductive salt is 10 g / L-80 g / L.

[0018] Furthermore, the pH buffer is one of citric acid, tartaric acid, dilute sulfuric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate.

[0019] Furthermore, during the electroplating process, the pH of the cyanide-free electroplating solution is 6.0-7.0, the temperature is 40-65°C, and the current density ranges from 2-6 mA / cm 2 .

[0020] The beneficial effects of the present invention are:

[0021] (1) The cyanide-free electroplating solution provided by the present invention can selectively electroplate hard gold or soft gold coatings by simply adjusting the content of the hardness modifier therein.

[0022] (2) The cyanide-free electroplating solution provided by the present invention is neutral and slightly acidic, does not contain toxic elements such as Tl, Pb, and As, and is environmentally friendly and has wide applicability.

[0023] (3) The cyanide-free electroplating solution provided by the present invention has a current efficiency greater than 98%, has few side reactions during the electroplating process, and produces a dense gold coating. DETAILED DESCRIPTION

[0024] The present invention will be further described below. It should be noted that this embodiment is based on the technical solution and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to this embodiment.

[0025] Example 1

[0026] This embodiment provides a cyanide-free electroplating solution capable of electroplating soft gold and hard gold, comprising sodium gold sulfite, a primary complexing agent, an auxiliary complexing agent, a stabilizer, a hardness regulator, a conductive salt, and a pH buffer.

[0027] The sodium gold sulfite has a gold element content of 10 g / L; the main complexing agent is sodium sulfite, with a content of 15 g / L; the auxiliary complexing agent is ethylenediamine, with a content of 10 g / L; the stabilizer is EDTA-2Na, with a content of 50 g / L; the hardness regulator is dodecyltrimethylammonium bromide, with a content of 15 mg / L; the conductive salt is sodium chloride, with a content of 10 g / L; and tartaric acid is used as a pH buffer to adjust the pH of the plating solution to about 6.5.

[0028] During the electroplating process, the temperature of the cyanide-free electroplating solution was 50°C and the current density was 4 mA / cm 2 The resulting coating is bright, with a current efficiency of 98.0% and a deposition rate of 120 mg·A / min. The micro-Vickers hardness of the coating before annealing is 155 HV, and after annealing at 300°C for 30 minutes, the micro-Vickers hardness of the coating is 136 HV.

[0029] Example 2

[0030] This embodiment provides a cyanide-free electroplating solution capable of electroplating soft gold and hard gold, comprising potassium gold sulfite, a primary complexing agent, an auxiliary complexing agent, a stabilizer, a hardness regulator, a conductive salt, and a pH buffer.

[0031] The potassium gold sulfite has a gold element content of 5 g / L; the main complexing agent is potassium sulfite, with a content of 40 g / L; the auxiliary complexing agent is propylene diamine, with a content of 15 g / L; the stabilizer is EDTA-2Na, with a content of 30 g / L; the hardness regulator is tetradecyltrimethylammonium bromide, with a content of 3 mg / L; the conductive salt is potassium nitrate, with a content of 20 g / L; and citric acid is used to adjust the pH of the cyanide-free electroplating solution to about 6.3.

[0032] During the electroplating process, the temperature of the cyanide-free electroplating solution was 40°C and the current density was 5 mA / cm 2The resulting coating is bright, with a current efficiency of 98.7% and a deposition rate of 121 mg·A / min. The micro-Vickers hardness of the coating before annealing is 142 HV, and after annealing at 300°C for 30 minutes, the micro-Vickers hardness of the coating is 121 HV.

[0033] Example 3

[0034] This embodiment provides a cyanide-free electroplating solution capable of electroplating soft gold and hard gold, comprising sodium gold sulfite, a primary complexing agent, an auxiliary complexing agent, a stabilizer, a hardness regulator, a conductive salt, and a pH buffer.

[0035] The sodium gold sulfite has a gold element content of 12 g / L; the main complexing agent is sodium sulfite, with a content of 55 g / L; the auxiliary complexing agent is diethylenetriamine, with a content of 30 g / L; the stabilizer is EDTA-2Na, with a content of 25 g / L; the hardness regulator is octadecyltrimethylammonium bromide, with a content of 2 mg / L; the conductive salt is sodium carbonate, with a content of 30 g / L; and dilute sulfuric acid is used as a pH buffer to adjust the pH of the cyanide-free electroplating solution to about 6.0.

[0036] During the electroplating process, the temperature of the cyanide-free electroplating solution was 55°C and the current density was 2 mA / cm 2 The resulting coating is bright, with a current efficiency of 98.7% and a deposition rate of 121 mg·A / min. The micro-Vickers hardness of the coating before annealing is 95 HV, and after annealing at 300°C for 30 minutes, the micro-Vickers hardness of the coating is 78 HV.

[0037] Example 4

[0038] This embodiment provides a cyanide-free electroplating solution capable of electroplating soft gold and hard gold, comprising ammonium gold sulfite, a primary complexing agent, an auxiliary complexing agent, a stabilizer, a hardness regulator, a conductive salt, and a pH buffer.

[0039] The ammonium gold sulfite has a gold element content of 20 g / L; the main complexing agent is ammonium sulfite, with a content of 130 g / L; the auxiliary complexing agent is ethylenediamine, with a content of 20 g / L; the stabilizer is EDTA-2Na, with a content of 20 g / L; the hardness regulator is hexadecyltrimethylammonium bromide, with a content of 0.1 mg / L; the conductive salt is potassium chloride, with a content of 80 g / L; and the pH of the cyanide-free electroplating solution is adjusted to about 7.0 with citric acid.

[0040] During the electroplating process, the temperature of the cyanide-free electroplating solution was 65°C and the current density was 6 mA / cm 2 The resulting coating is bright, with a current efficiency of 99.5% and a deposition rate of 122 mg·A / min. The micro-Vickers hardness of the coating before annealing is 86 HV, and after annealing at 300°C for 30 minutes, the micro-Vickers hardness of the coating is 72 HV.

[0041] The cyanide-free electroplating solutions prepared in Examples 1-4 and their properties are shown in Table 1.

[0042]

[0043]

[0044] * Annealing at 300℃ for 30min.

[0045] Those skilled in the art can make various corresponding changes and modifications based on the above technical solutions and concepts, and all of these changes and modifications should be included in the scope of protection of the claims of the present invention.

Claims

1. A cyanide-free electroplating solution for electroplating soft gold, characterized in that: The invention comprises a gold sulfite salt, a complexing agent, a stabilizer, a hardness regulator, a conductive salt and a pH buffer; the hardness regulator is one of decanyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide or octadecyltrimethylammonium bromide; the content of the hardness regulator is 0.1 mg / L-2 mg / L; The content of the gold sulfite in the cyanide-free electroplating solution is 5g / L-20g / L, calculated as gold element; The complexing agent includes a main complexing agent and an auxiliary complexing agent, wherein the content of the main complexing agent is 15g / L-130g / L; the content of the auxiliary complexing agent is 10g / L-30g / L; the main complexing agent is one of sodium sulfite, potassium sulfite or ammonium sulfite, and the auxiliary complexing agent is one of ethylenediamine, propylenediamine or diethylenetriamine; The stabilizer content is 20g / L-50g / L; The content of the conductive salt is 10 g / L-80 g / L.

2. The cyanide-free electroplating solution according to claim 1, wherein The gold sulfite salt is one of sodium gold sulfite, potassium gold sulfite or ammonium gold sulfite.

3. The cyanide-free electroplating solution according to claim 1, wherein The stabilizer is EDTA-2Na.

4. The cyanide-free electroplating solution according to claim 1, wherein The conductive salt is one of sodium carbonate, potassium nitrate, sodium chloride or potassium chloride.

5. The cyanide-free electroplating solution according to claim 1, wherein The pH buffer is one of citric acid, tartaric acid, dilute sulfuric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, disodium hydrogen phosphate or dipotassium hydrogen phosphate.

6. The cyanide-free electroplating solution according to claim 1, wherein During the electroplating process, the temperature of the cyanide-free electroplating solution is 40-65°C, and the current density range is 2-6 mA / cm 2 .

7. The cyanide-free electroplating solution according to claim 1, wherein During the electroplating process, the pH of the cyanide-free plating solution is 6.0-7.0.

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