CN113416989B

CN113416989B - Silver plating process and silver plated part

Info

Publication number: CN113416989B
Application number: CN202110713560.1A
Authority: CN
Inventors: 杨照群
Original assignee: Suzhou Ruigang Environmental Protection Technology Co ltd
Current assignee: Suzhou Ruigang Environmental Protection Technology Co ltd
Priority date: 2021-06-25
Filing date: 2021-06-25
Publication date: 2022-11-01
Anticipated expiration: 2041-06-25
Also published as: CN113416989A

Abstract

The invention discloses a silver plating process, which comprises the steps of placing a pretreated workpiece in an electroplating solution containing solutes such as silver salt, complexing agent, rare earth salt and the like for electroplating to form a silver-rare earth alloy layer, and plating silver on the surface of the silver-rare earth alloy layer. The addition of rare earth elements improves the affinity between the silver coatings, so that the surface energy of the silver coating on the uppermost layer is reduced, the problem of color change of the silver coating at high temperature due to agglomeration is effectively prevented, and the base material or the inner coating can be prevented from alloying with the silver coating. The invention also discloses a silver-plated piece prepared by the silver plating process. The invention can be applied to the surface treatment of the 5G cavity, and ensures the conductivity and the weldability of the silver coating on the surface of the 5G cavity.

Description

Silver plating process and silver plated part

Technical Field

The invention belongs to the technical field of metal surface silver plating treatment, and particularly relates to a silver plating process and a silver plated part.

Background

The silver plating layer has good electrical conductivity, thermal conductivity, solderability, stability and reliable adhesive force of the matrix, and the cost of the silver is much lower than that of noble metals such as gold, platinum and the like, so the application is particularly wide. The liquid crystal display is mainly used for ornaments and tableware in the early period, and is increasingly applied to airplanes and electronic products at present. Generally, the chemical stability of silver is relatively good and is not easy to dissolve in common acid and alkali, but the silver has poor resistance to adverse effects of environmental conditions, especially poor sulfuration resistance, and the silver part surface is corroded by sulfides (mainly hydrogen sulfide and sulfur dioxide) contained in the air and then undergoes a chemical reaction with the sulfides to generate silver sulfide, so that the silver surface is discolored; silver sulfide has poor conductivity and is liable to cause unreliable electrical contact. Taking a 5G cavity as an example, in the prior art, the 5G cavity is a process of plating copper and then plating silver by adopting aluminum alloy, a base material generally needs to be welded after the silver plating, in order to ensure that the product does not discolor during actual welding, a manufacturer can perform a high-temperature simulation experiment on the cavity, the temperature is about 280 ℃, and silver atoms can agglomerate at high temperature due to the fact that the silver plating layer is thin and the surface energy is high, and the copper plating layer on the lower layer is exposed, so that the color of the plating layer is changed.

In Yangyu's analysis of cause of yellowing of silver coating by high-temperature baking, it is proposed to add a layer of nickel under the silver coating to effectively solve the problem of yellowing of the coating. However, the presence of nickel affects the dielectric loss of the 5G cavity, and so this approach needs improvement. In patent No. CN108193209A, a silver protective agent is proposed, which uses octadecyl mercaptan and trimethyl mercapto phosphate as main film forming agents, and mixes octadecyl mercaptan, trimethyl mercapto phosphate and emulsifier, and forms a layer of monomolecular self-assembled film through the action of the protective agent and the silver coating layer, so as to effectively protect silver, prevent corrosion and prevent the silver coating layer from discoloring at high temperature. However, the decomposition of the organic film at a high temperature of 280 ℃ is fast and cannot meet the production requirements, so the method still needs to be improved.

Therefore, it is necessary to provide a silver plating process capable of preventing discoloration of a silver plated layer at high temperatures.

Disclosure of Invention

In view of the above-mentioned deficiencies of the prior art, the present invention aims to: the pretreated workpiece is placed in an electroplating solution containing solutes such as silver salt, complexing agent, rare earth salt and the like for electroplating to form a silver-rare earth alloy layer, and then silver is plated on the surface of the silver-rare earth alloy layer, and the addition of rare earth elements improves the affinity between the plating layers, so that the surface energy of the surface silver plating layer is reduced, and the problem of color change of the silver plating layer due to agglomeration at high temperature is effectively solved.

In order to achieve the purpose, the invention provides the following technical scheme:

a silver plating process comprises the following steps:

s1, preprocessing a workpiece to be plated;

s2, placing the pretreated workpiece into electroplating solution for electroplating, wherein the solute of the electroplating solution comprises silver salt, complexing agent, rare earth salt, cyanide, hydroxide and carbonate;

and S3, washing the workpiece obtained in the step S2, and then carrying out surface silver plating.

In the step S1, the pretreatment mainly comprises the working procedures of oil removal, water washing and the like, and aims to improve the binding force between a plating layer and a base material and obtain a good electroplating effect; when the workpiece has multiple layers of plating, the pretreatment also includes electroplating of the internal plating. In the step S2, a complexing agent is utilized to hinder the reduction process of silver ions on the active part of the cathode surface, the precipitation potential of the silver ions is reduced, and the codeposition of rare earth elements and the silver ions is realized, so that a silver-rare earth alloy layer is formed on the surface of a workpiece; the cyanide, the hydroxide and the carbonate are used for adjusting the pH value of the electroplating solution and improving the conductivity and the uniformity of the electroplating solution. And S3, electroplating a silver layer on the surface of the silver-rare earth alloy layer. Because the surface energy of the silver coating is high, the silver coating is easy to agglomerate and discolor at high temperature, and the beauty, the conductivity and the welding performance are influenced, in the invention, the rare earth element increases the affinity of the silver-rare earth alloy layer and the silver coating, reduces the surface energy of the silver coating, prevents the agglomeration of the silver coating at high temperature, simultaneously, the alloy formed by silver and the rare earth element is most similar to the property of the outer silver coating, and can prevent the silver coating from alloying with a substrate or an inner coating on the premise of good bonding force with the silver coating.

In the step S2, the working temperature of the electroplating solution is 25-60 ℃, the electroplating speed is reduced when the temperature is too low, and the complexing agent is decomposed when the temperature is too high, so that the performance of a coating is influenced; the current density is 3-8A/dm²The electroplating time is 10-60s, and a plating layer with uniform thickness is obtained with proper current density and electroplating time, so that the electroplating speed is accelerated as much as possible while the compactness of the plating layer is improved, and the working efficiency is improved.

The rare earth salt is selected from one or more of lanthanum nitrate, cerium nitrate, erbium nitrate, gadolinium chloride, samarium chloride and europium fluoride and is used for providing rare earth ions for electroplating solution; preferably, lanthanum nitrate or cerium nitrate is used, and as the reserves of rare earth cerium and lanthanum are large, the price is low, the raw materials are easy to purchase, and the production cost can be reduced.

The complexing agent is selected from one or more of 3-aminopyridine-2-formamide, 3,4, 5-trimethoxybenzamide and 2-amino-N-hydroxybenzamide, the complexing agents have strong complexing capability to rare earth elements, assist the deposition of the rare earth elements, do not react with metal ions in a solution to generate precipitates, and have the advantages of easiness in purchase and cost saving.

The silver salt is silver cyanide which is used as a complexing agent and a cathode surfactant, so that the plating layer is fine and uniform in crystallization.

The cyanide is potassium cyanide, the hydroxide is potassium hydroxide, the carbonate is potassium carbonate, the cathode polarization of the electrolyte is improved, and the crystal of the coating is fine.

In the electroplating solution, 40-45g/L of silver cyanide, 8-15g/L of potassium hydroxide, 40-45g/L of potassium carbonate, 40-45g/L of potassium cyanide, 10-50g/L of complexing agent and 1-15g/L of rare earth salt.

The workpiece to be plated is a 5G cavity, and in the step S1, the pretreatment step comprises the step of forming a copper plating layer on the surface of the substrate of the 5G cavity. Generally, the 5G cavity is made of an aluminum alloy material, and the activity of copper is between that of aluminum and that of silver, so that the compactness of a coating is improved.

The silver-plated piece is prepared by the silver plating process, and comprises a base material, and a silver-plated alloy layer and a silver-plated layer which are formed on the surface of the base material.

The silver-plated alloy layer comprises silver and rare earth elements, the mass percent of the rare earth elements is 0.8-5%, and the affinity is insufficient when the using amount of the rare earth elements is too small, so that the using performance is influenced; the excessive use amount can increase the cost and cause waste, and the production is generally controlled to be below 5 percent.

Compared with the prior art, the invention has the beneficial effects that:

1. the silver plating process comprises the steps of placing a pretreated workpiece in electroplating solution containing solutes such as silver salt, complexing agent, rare earth salt and the like for electroplating to form a silver-rare earth alloy layer, then plating silver on the surface of the silver-rare earth alloy layer, and adding rare earth elements to improve the affinity between the plating layers, so that the surface energy of the surface silver plating layer is reduced, and the problem of color change of the silver plating layer due to agglomeration at high temperature is effectively solved.

2. According to the silver plating process, the complexing agent is added into the plating solution of the silver-plated alloy, the complexing agent is utilized to hinder the reduction process of silver ions on the active part of the cathode surface, the precipitation potential of the silver ions is reduced, and the rare earth elements and the silver ions can be co-deposited.

3. According to the silver plating process, the copper plating layer, the silver plating alloy layer and the silver plating layer are formed on the surface of the 5G cavity base material, so that the silver plating layer is prevented from discoloring due to agglomeration at high temperature, and the copper plating layer and the silver plating layer are prevented from alloying.

Drawings

In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings required to be used in the description of the embodiments will be briefly introduced below, and it is apparent that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings may be obtained based on these drawings without inventive efforts.

Fig. 1 is a schematic structural diagram of a 5G chamber according to an embodiment of the present invention after silver plating.

Reference numerals: 1-5G cavity base material, 2-copper plating layer, 3-silver plating alloy layer and 4-silver plating layer.

Detailed Description

The technical solution in the specific embodiment of the present invention will be clearly and completely described below by taking the 5G cavity as an example, and it is obvious that the described embodiment is only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The first embodiment is as follows:

an electroplating process comprising the steps of:

s1, preprocessing a 5G cavity to be plated;

s2, placing the pretreated 5G cavity into electroplating solution for electroplating, wherein solutes of the electroplating solution comprise silver salt, complexing agent, rare earth salt, cyanide, hydroxide and carbonate;

and S3, washing the 5G cavity obtained in the step S2 with water, and then carrying out surface silvering.

In the step S1, the pretreatment is water washing and copper plating.

In the step S2, the working temperature of the plating solution is about 30 ℃ and the current density is 3A/dm²The plating time was 30s.

The silver salt is silver cyanide, the complexing agent is 3-aminopyridine-2-formamide, the rare earth salt is lanthanum nitrate, the cyanide, the hydroxide and the carbonate are respectively potassium cyanide, potassium hydroxide and potassium carbonate, and the specific content is as follows:

40g/L of silver cyanide;

8g/L of potassium hydroxide;

40g/L of potassium carbonate;

40g/L of potassium cyanide;

10g/L of 3-aminopyridine-2-formamide;

lanthanum nitrate 1g/L.

As shown in fig. 1, the surface of the 5G cavity substrate 1 is sequentially provided with a copper plating layer 2, a silver plating alloy layer 3, and a silver plating layer 4, where the copper plating layer 2 is about 8 μm thick, the silver plating alloy layer 3 is about 0.1 μm thick, and the silver plating layer 4 is about 1 μm thick, and in this embodiment, the silver plating alloy layer 3 is a silver-lanthanum alloy, and lanthanum content is about 0.8%.

Example two:

unlike the first embodiment, in this embodiment, the complexing agent is 3,4, 5-trimethoxybenzamide, the rare earth salt is cerium nitrate, and the solute content in the plating solution is:

42g/L of silver cyanide;

12g/L of potassium hydroxide;

42g/L of potassium carbonate;

42g/L of potassium cyanide;

15g/L of 3,4,5-trimethoxy benzamide;

3g/L of cerium nitrate.

In the step S2, the working temperature of the plating solution is about 45 ℃ and the current density is 5A/dm²The plating time was 20s.

In this example, the silver-plated alloy layer 3 of the 5G chamber obtained was a silver-cerium alloy with a cerium content of about 1.5%.

Example three:

unlike the first embodiment, in this embodiment, the complexing agent is 2-amino-N-hydroxybenzamide, the rare-earth salt is europium fluoride, and the solute content in the plating solution is:

45g/L of silver cyanide;

15g/L of potassium hydroxide;

45g/L of potassium carbonate;

45g/L of potassium cyanide;

10g/L of 2-amino-N-hydroxybenzamide;

europium fluoride 1g/L.

In the step S2, the working temperature of the electroplating solution is about 60 ℃, and the current density is 8A/dm²The plating time was 10s.

In this example, the silver-plated alloy layer 3 of the resulting 5G cavity was a silver-europium alloy in which the europium content was about 0.8%.

Example four:

different from the first embodiment, in the present embodiment, the complexing agent is 2-amino-N-hydroxybenzamide, the rare-earth salt is gadolinium chloride, and the solute content in the electroplating solution is:

40g/L of silver cyanide;

15g/L of potassium hydroxide;

43g/L of potassium carbonate;

42g/L of potassium cyanide;

30g/L of 2-amino-N-hydroxybenzamide;

5g/L of gadolinium chloride.

In the step S2, the working temperature of the electroplating solution is about 60 ℃, and the current density is 5A/dm²The plating time was 20s.

In this example, the silver-plated alloy layer 3 of the 5G cavity obtained is a silver-gadolinium alloy, in which the gadolinium content is about 2%.

Example five:

in this embodiment, the complexing agent is 3,4, 5-trimethoxybenzamide, the rare earth salt is samarium chloride, and the solute content in the plating solution is:

40g/L of silver cyanide;

15g/L of potassium hydroxide;

45g/L of potassium carbonate;

42g/L of potassium cyanide;

50g/L of 3,4, 5-trimethoxy benzamide;

and 15g/L of samarium chloride.

In the step S2, the working temperature of the plating solution is about 25 ℃ and the current density is 6A/dm²The plating time was 60 seconds.

In this embodiment, the silver-plated alloy layer 3 of the obtained 5G cavity is a silver-samarium alloy, wherein the content of samarium is about 5%.

In the first to fifth embodiments, different rare earth elements are respectively used for forming alloys with silver, the specific solute content of the electroplating solution in the step S2 in each embodiment is described in detail, the thickness of the formed plating layer is measured, the thickness of the plating layer is ensured to meet the electroplating standard, and the mass ratio of the rare earth elements in the obtained silver-plated alloy layer is also measured. Next, a high temperature resistance test is performed on the 5G cavity obtained in the first to fifth embodiments, and the 5G cavity without the plating layer 5G cavity and with the nickel plating layer as the intermediate layer, so as to determine whether the silver plating process provided by the present invention has an obvious effect on solving the problem of discoloration of the silver plating layer due to agglomeration at a high temperature, and the test results are shown in table 1 below.

Sample(s)	Temperature (. Degree.C.)	Results of high temperature resistance test
			Without protective means	280	Color change after 1min
Nickel intermediate layer	280	Color change begins after 10min
			Example 1	280	Color change after 12min
Example 2	280	Color change begins after 13min
			Example 3	280	Color change after 12min
Example 4	280	Color change after 12min
			Example 5	280	Color change begins after 13min

TABLE 1

The electroplating process with the nickel-plated layer as the middle layer comprises the following steps:

s1, direct current electrodeposition copper plating treatment, water washing and pretreatment;

s2, carrying out chemical nickel plating treatment on the pretreated plated part, and washing with water;

s3, direct current deposition silver plating

In the step S2, the pH value of the chemical plating solution is kept between 8 and 10, the working temperature is about 90 ℃, the working time is 1min, and the chemical plating solution comprises the following components:

45g/L of nickel chloride;

11g/L of sodium hypophosphite;

50g/L of ammonium chloride;

80g/L sodium citrate;

ammonium citrate 20g/L.

The thickness of the obtained coating is 8 μm of copper plating, 0.5 μm of nickel plating and 1 μm of silver plating.

The test result shows that the influence of the addition of the silver-rare earth alloy intermediate coating on the high-temperature resistance of the silver coating is better than that of the nickel intermediate coating, the welding work is facilitated, and the dielectric loss of the 5G cavity is influenced by the existence of the nickel intermediate coating. Meanwhile, the electroplating time of the silver alloy plating layer is far shorter than that of the nickel plating layer, so that the working hours can be reduced, the working efficiency can be improved, and the cost can be saved.

The silver plating process and the silver plated part provided by the invention are described in detail, the structure and the working principle of the invention are explained by applying specific examples, and the performance test is carried out on the obtained sample, which shows that the invention has obvious effect on solving the problem that the silver plated layer is discolored due to agglomeration at high temperature. The above description of the embodiments is only intended to facilitate the understanding of the method and the core idea of the present invention. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

Claims

1. A silver plating process is characterized by comprising the following steps:

s1, preprocessing a workpiece to be plated;

s2, placing the pretreated workpiece into electroplating solution for electroplating to form a silver-rare earth alloy layer, wherein the mass percent of rare earth elements in the silver-rare earth alloy layer is 0.8-5%, and solutes of the electroplating solution comprise silver salt, complexing agent, rare earth salt, cyanide, hydroxide and carbonate;

s3, washing the workpiece obtained in the step S2 with water, and then carrying out surface silver plating;

the workpiece to be plated is a 5G cavity, and in the step S1, the pretreatment step comprises the step of forming a copper plating layer on the surface of the substrate of the 5G cavity.

2. The silver plating process according to claim 1, wherein the working temperature of the plating solution in step S2 is 25 to 60 ℃ and the current density is 3 to 8A/dm²The electroplating time is 10-60s.

3. The silver plating process according to claim 1, wherein the rare earth salt is selected from one or more of lanthanum nitrate, cerium nitrate, erbium nitrate, gadolinium chloride, samarium chloride and europium fluoride.

4. The silver plating process according to claim 1, wherein the complexing agent is selected from one or more of 3-aminopyridine-2-formamide, 3,4, 5-trimethoxybenzamide, and 2-amino-N-hydroxybenzamide.

5. A silver plating process according to claim 1, wherein the silver salt is silver cyanide.

6. A silver plating process according to claim 5, wherein the cyanide is potassium cyanide, the hydroxide is potassium hydroxide and the carbonate is potassium carbonate.

7. The silver plating process according to claim 6, wherein the plating solution contains 40-45g/L of silver cyanide, 8-15g/L of potassium hydroxide, 40-45g/L of potassium carbonate, 40-45g/L of potassium cyanide, 10-50g/L of complexing agent and 1-15g/L of rare earth salt.

8. A silver-plated article, characterized by being prepared by the silver-plating process according to any one of claims 1 to 7, and comprising a base material, and a copper-plated layer, a silver-plated alloy layer and a silver-plated layer formed on the surface of the base material, wherein the silver-plated alloy layer comprises silver and rare earth elements, and the mass percentage of the rare earth elements is 0.8 to 5%.