CN111778498A

CN111778498A - Coating structure and preparation method thereof

Info

Publication number: CN111778498A
Application number: CN202010634498.2A
Authority: CN
Inventors: 刘彬灿; 黄明起; 夏建文
Original assignee: Shenzhen Samcien Semiconductor Materials Co ltd
Current assignee: Shenzhen Samcien Semiconductor Materials Co ltd
Priority date: 2020-07-02
Filing date: 2020-07-02
Publication date: 2020-10-16
Anticipated expiration: 2040-07-02

Abstract

The invention discloses a film coating structure and a preparation method thereof. The coating structure comprises a silver layer, a palladium layer and a gold layer which are sequentially arranged on the conducting layer. The invention aims at the problem that the existing process deposits a layer of palladium on a nickel layer in a deposition mode, then deposits a layer of gold in a replacement mode, and due to the magnetism of the nickel layer, loss and attenuation are caused during high-frequency high-speed signal transmission, so that the high-frequency high-speed signal transmission cannot be met. The coating structure provided by the invention comprises the silver layer, the palladium layer and the gold layer, has no magnetism, does not influence the high-frequency and high-speed transmission of signals, can protect the conductive layer and provides good weldability, conductivity, corrosion resistance, friction resistance and the like. The cost of the silver layer is obviously reduced by replacing gold (noble metal), the palladium layer on the surface of the silver can effectively prevent the corrosion of the silver layer, and the gold layer can play a role in wetting and corrosion resistance.

Description

Coating structure and preparation method thereof

Technical Field

The invention belongs to the technical field of surface treatment, and particularly relates to a coating structure and a preparation method thereof.

Background

In the existing packaging process of electronic industrial parts, nickel palladium gold is widely applied to industry as a traditional surface treatment mode, and has the characteristics of excellent gold wire bonding performance, wear resistance, corrosion resistance and the like for the surface of a conductive layer.

With the development of science, people step into the 5G era, and meanwhile, the fact that electronic industrial component packaging such as semiconductor packaging, IC substrates, aluminum substrates, ceramic substrates, printed circuit boards and the like enters a high-frequency high-speed period is marked, nickel-palladium-gold is used as a traditional surface treatment process, and due to the magnetism of a nickel layer, loss and attenuation of signals can be caused during high-frequency high-speed transmission, so that the high-frequency high-speed development is limited by the existing surface treatment material at present.

The gold-palladium-gold plating layer has the same excellent bonding and welding performance as the nickel-palladium-gold plating layer, but because three layers of the laminated structure are all made of noble metals, the gold-palladium-gold plating layer has the defects of higher processing cost and difficulty in maintaining mass production.

CN102605359A discloses a novel surface treatment stack of chemical palladium-gold plating film, on a bonding pad (copper), firstly, a layer of metal palladium with a thickness of 0.06-0.12 μm is formed by a displacement method, then a layer of reduction type palladium with a thickness of 0.03-0.2 μm is deposited on the displacement type palladium layer for thickening the palladium plating layer, and finally, a layer of gold with a thickness of 0.03-0.2 μm is deposited on the palladium surface by a reduction method. Because the gold is deposited in a redox mode, the stability of the bath solution is poor, the control in the actual production and processing process is difficult, and the requirement of large-scale mass production is difficult to meet.

CN110241406A and CN110318047A disclose another surface treatment stack of chemical gold-palladium-gold plating film, which is to replace a layer of thin gold on a bonding pad (copper) by a replacement method, then deposit a layer of chemical palladium on the gold surface by the catalytic property of gold, and finally deposit a layer of chemical gold on the palladium by a replacement method, so as to form a chemical stack of gold-palladium-gold.

Therefore, there is a need in the art to develop a novel method for preparing a plated film, which has the advantages of better solderability, conductivity and corrosion resistance, no loss and attenuation of signals during high-frequency and high-speed transmission, and low production cost.

Disclosure of Invention

The invention aims to solve the problems that in the prior art, a layer of palladium is deposited on a nickel layer in a deposition mode, then a layer of gold is deposited in a replacement mode, and due to the magnetism of the nickel layer, loss and attenuation are caused during high-frequency high-speed signal transmission, so that the high-frequency high-speed signal transmission cannot be met. The coating film obtained by the method has no magnetism, does not influence high-frequency and high-speed transmission of signals, and has the advantages of better weldability, conductivity, wear resistance and the like.

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

one objective of the present invention is to provide a plating structure, which includes a silver layer, a palladium layer and a gold layer sequentially disposed on a conductive layer.

The coating structure comprises the silver layer, the palladium layer and the gold layer, has no magnetism, does not influence high-frequency and high-speed transmission of signals, can protect the conductive layer and provides good weldability, conductivity, corrosion resistance, friction resistance and the like. The cost of the silver layer is obviously reduced by replacing gold (noble metal), the palladium layer on the surface of the silver can effectively prevent the corrosion of the silver layer, and the gold layer can play a role in wetting and corrosion resistance.

Preferably, the silver layer has a thickness of 0.2 to 0.4 μm, such as 0.21 μm, 0.23 μm, 0.25 μm, 0.27 μm, 0.29 μm, 0.3 μm, 0.31 μm, 0.33 μm, 0.35 μm, 0.37 μm, or 0.39 μm.

Preferably, the palladium layer has a thickness of 0.05 to 0.2 μm, such as 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, or 0.19 μm.

Preferably, the gold layer has a thickness of 0.05 to 0.2 μm, such as 0.06 μm, 0.07 μm, 0.08 μm, 0.09 μm, 0.1 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, or 0.19 μm.

A second object of the present invention is to provide a method for preparing the plating structure according to the first object, the method comprising: and sequentially preparing a silver layer, a palladium layer and a gold layer on the conducting layer to obtain the coating structure.

According to the invention, a layer of chemical silver is replaced on the conductive layer in a replacement mode, then a layer of metal palladium is deposited in an oxidation reduction mode through autocatalysis of silver, so that corrosion of a silver layer can be effectively prevented, and finally a layer of gold is deposited in an oxidation reduction mode to play a role in wetting and resisting corrosion.

Compared with a gold-palladium-gold film coating structure, the invention has the advantages that the cost is obviously reduced by using silver to replace gold (noble metal); compared with a nickel-palladium-gold coating structure, the coating process is simpler in treatment, the operation temperature is lower, and the cost is indirectly reduced.

Preferably, the preparation method of the silver layer comprises the following steps: and carrying out displacement reaction on the conductive layer to obtain the silver layer.

Preferably, the preparation method of the silver layer comprises the following steps: and placing the conductive layer in a chemical silver solution to obtain the conductive layer with the surface covered with the silver layer.

Preferably, the chemical silver solution has a pH of 8.0 to 9.0, such as 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, or 8.9.

Preferably, the chemical silver solution has a temperature of 40 to 70 ℃, such as 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃ or 68 ℃.

Preferably, the conductive layer is placed in the chemical silver solution for 2-4 min, such as 2.5min, 3min or 3.5 min.

Preferably, after the silver layer is prepared on the conductive layer, a washing process is further included, preferably washing with pure water.

Preferably, the chemical silver solution comprises silver ions or complex silver ions, preferably the chemical silver solution further comprises any one or a combination of at least two of an amine complexing agent, an amine complexing agent and a polyhydroxy acid complexing agent, and further preferably the chemical silver solution consists of the silver ions or the complex silver ions, the amine complexing agent and the polyhydroxy acid complexing agent.

Preferably, the concentration of the silver ions or the complex silver ions in the chemical silver solution is 0.5-5 g/L, such as 1g/L, 1.5g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L or 4.5 g/L.

Preferably, the concentration of the amine complexing agent in the chemical silver solution is 1-20 g/L, such as 3g/L, 5g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L or 19 g/L.

Preferably, the concentration of the amino complexing agent in the chemical silver solution is 1-20 g/L, such as 3g/L, 5g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L or 19 g/L.

Preferably, the concentration of the polyhydroxy acid complexing agent in the chemical silver solution is 1-20 g/L, such as 3g/L, 5g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L or 19 g/L.

Preferably, the silver ions or complexed silver ions include any one of or a combination of at least two of silver ammine complex ions, silver sulfite complex ions and silver halide complex ions.

Preferably, the amine complexing agent includes any one or a combination of at least two of ammonia, triammonium citrate, ammonium phosphate, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium ethylene carbonate, diethylenetriamine, aminopyridine of triethylenetetramine, aniline, and phenylenediamine.

Preferably, the amino complexing agent comprises any one of glycine, alpha-alanine, beta-alanine, cystine, ethylenediaminetetraacetic acid, aspartic acid, glutamic acid, nitrilotriacetic acid sulfamate and aromatic alanine or a combination of at least two thereof.

Preferably, the polyhydroxy acid complexing agent comprises any one or a combination of at least two of an acid, an alkali metal salt of the acid and an ammonium salt of the acid, preferably the acid is any one or a combination of at least two of citric acid, tartaric acid, gluconic acid, malic acid, lactic acid, 1-hydroxy-ethylidene-1, 1-diphosphonic acid, sulfosalicylic acid and phthalic acid.

Preferably, the preparation method of the palladium layer comprises the following steps: and depositing a layer of metal palladium on the silver layer in an oxidation-reduction mode to obtain a palladium layer.

Preferably, the preparation method of the palladium layer is as follows: and placing the conducting layer with the surface covered with the silver layer in a chemical palladium solution to obtain a pre-product, wherein the palladium layer in the pre-product covers the surface of the silver layer.

Preferably, the chemical palladium solution has a pH of 6.5 to 8.0, such as 6.6, 6.7, 6.8, 6.9, 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, or 7.9.

Preferably, the chemical palladium solution has a temperature of 40 to 70 ℃, such as 42 ℃, 45 ℃, 48 ℃, 50 ℃, 52 ℃, 55 ℃, 58 ℃, 60 ℃, 62 ℃, 65 ℃ or 68 ℃.

Preferably, the conductive layer with the surface covered with the silver layer is placed in the chemical palladium solution for 4-15 min, such as 5min, 6min, 8min, 10min, 12min or 14 min.

Preferably, after the pre-product is obtained, a washing process is also included, preferably washing with pure water.

Preferably, the chemical palladium solution comprises a palladium salt, preferably the chemical palladium solution further comprises any one or a combination of at least two of a main complexing agent, an auxiliary complexing agent, a reducing agent, a first stabilizing agent and a first pH buffer, and further preferably the chemical palladium solution consists of palladium ions or palladium complex ions, the main complexing agent, the auxiliary complexing agent, the reducing agent, the first stabilizing agent and the first pH buffer.

Preferably, the concentration of the palladium salt is 0.1-5 g/L, such as 0.2g/L, 0.5g/L, 0.8g/L, 1g/L, 1.5g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L or 4.5g/L, and the like.

Preferably, the concentration of the main complexing agent is 5-20 g/L, such as 6g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L or 19 g/L.

Preferably, the concentration of the auxiliary complexing agent is 5-25 g/L, such as 6g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L, 19g/L, 20g/L, 22g/L, 23g/L or 24 g/L.

Preferably, the concentration of the reducing agent is 1-25 g/L, such as 3g/L, 5g/L, 8g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L, 19g/L, 20g/L, 22g/L, 23g/L or 24 g/L.

Preferably, the concentration of the first stabilizer is 0.1-5 mg/L, such as 0.2mg/L, 0.5mg/L, 0.8mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L, 3mg/L, 3.5mg/L, 4mg/L or 4.5mg/L, and the like.

Preferably, the concentration of the first pH buffer is 0.5-5 g/L, such as 0.8g/L, 1g/L, 1.5g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L or 4.5g/L, and the like.

Preferably, the palladium salt comprises any one of palladium sulfate, palladium chloride, ammonium palladium chloride, tetraammine palladium dichloride and palladium ammonia sulfate or a combination of at least two of the foregoing.

Preferably, the main complexing agent is an amine compound, and preferably comprises any one or a combination of at least two of ammonia water, ethylenediamine, ethylamine and sodium ethylenediamine tetracetate.

Preferably, the auxiliary complexing agent comprises any one of sodium citrate, acrylic acid, succinic acid, oxalic acid and malic acid or a combination of at least two of the above.

Preferably, the reducing agent comprises any one of formic acid, hypophosphite, ascorbic acid and dimethylamine borane, or a combination of at least two thereof.

Preferably, the first stabilizer comprises any one of bismuth nitrate, thiourea, 4-dimethylaminopyridine and 2-mercaptobenzothiophene or a combination of at least two of the foregoing.

Preferably, the first pH buffer comprises any one of borax, boric acid, sodium dihydrogen phosphate and disodium hydrogen phosphate or a combination of at least two thereof.

Preferably, the preparation method of the gold layer comprises the following steps: and depositing a layer of gold on the surface of the pre-product in an oxidation-reduction mode to obtain a gold layer.

Preferably, the preparation method of the gold layer comprises the following steps: and placing the pre-product in a chemical gold solution to obtain a coating structure.

Preferably, the chemical gold solution has a pH of 6.0 to 7.0, such as 6.1, 6.2, 6.3, 6.4, 6.5, 6.6, 6.7, 6.8, or 6.9.

Preferably, the temperature of the chemical gold solution is 70 to 80 ℃, such as 71 ℃, 72 ℃, 73 ℃, 74 ℃, 75 ℃, 76 ℃, 77 ℃, 78 ℃ or 79 ℃ and the like.

Preferably, the time for placing the pre-product in the chemical gold solution is 0.5-20 min, such as 0.6min, 1min, 5min, 8min, 10min, 12min, 15min, 18min or 19 min.

Preferably, after the coating structure is obtained, a washing and drying process is also included, and the washing process is preferably carried out by pure water.

Preferably, the drying temperature is 60-90 ℃, such as 62 ℃, 65 ℃, 68 ℃, 70 ℃, 72 ℃, 75 ℃, 78 ℃, 80 ℃, 82 ℃, 85 ℃ or 88 ℃.

Preferably, the chemical gold solution comprises a gold salt, preferably the chemical gold solution further comprises any one or a combination of at least two of a complexing agent, an accelerator, a second stabilizer and a second pH buffer, and further preferably the chemical gold solution consists of a gold salt, a complexing agent, an accelerator, a second stabilizer and a second pH buffer.

Preferably, the concentration of the gold salt in the chemical gold solution is 0.1-5 g/L, such as 0.2g/L, 0.5g/L, 0.8g/L, 1g/L, 1.5g/L, 2g/L, 2.5g/L, 3g/L, 3.5g/L, 4g/L or 4.5 g/L.

Preferably, the concentration of the complexing agent in the chemical gold solution is 5-20 g/L, such as 6g/L, 7g/L, 9g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L or 19 g/L.

Preferably, the concentration of the accelerator in the chemical gold solution is 1-25 mg/L, such as 3mg/L, 5mg/L, 8mg/L, 10mg/L, 11mg/L, 13mg/L, 15mg/L, 17mg/L, 19mg/L, 20mg/L, 22mg/L, 23mg/L or 24 mg/L.

Preferably, the concentration of the second stabilizer in the chemical gold solution is 0.1-5 mg/L, such as 0.2mg/L, 0.5mg/L, 0.8mg/L, 1mg/L, 1.5mg/L, 2mg/L, 2.5mg/L, 3mg/L, 3.5mg/L, 4mg/L or 4.5 mg/L.

Preferably, the concentration of the second pH buffer in the chemical gold solution is 1-25 g/L, such as 3g/L, 5g/L, 8g/L, 10g/L, 11g/L, 13g/L, 15g/L, 17g/L, 19g/L, 20g/L, 22g/L, 23g/L or 24 g/L.

Preferably, the gold salt includes any one of gold potassium cyanide, gold potassium citrate, gold chlorite chloride and tetrachloro acid hydrate or a combination of at least two thereof.

Preferably, the complexing agent comprises any one of, or a combination of at least two of, acetohydroxamic acid, benzohydroxamic acid, salicylhydroxamic acid, and acetohydroxamic acid.

Preferably, the accelerator comprises any one of lanthanum sulfate, cerium sulfate and thallium sulfate or a combination of at least two thereof.

Preferably, the second stabilizer includes any one of 2, 2-dipyridyl amine, 2, 4-dimethylpyridine, 2, 4-dimethylpiperidine and pyridine-2, 3-dicarboxylic acid or a combination of at least two thereof.

Preferably, the second pH buffer is any one of 2-morpholinoethanesulfonic acid, bis (2-hydroxyethylamino) trimethylolmethane, piperazine-1, 4-diethylsulfonic acid, and citric acid-sodium citrate buffer, or a combination of at least two thereof.

Preferably, the conductive layer further comprises a process of degreasing, washing and microetching before preparing the silver layer.

Before the chemical deposition of the silver, the palladium and the gold, the conductivity and the mechanical property between the conductive layer and the silver layer can be improved by a series of pretreatment (surface cleaning and coarsening) of the conductive layer.

The specific composition of the conductive layer is not limited in the present invention, and can be selected by those skilled in the art according to the actual situation, and the present invention includes but is not limited to copper, tungsten or silver.

Preferably, the washing is washing with pure water.

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

the coating film is a silver coating, a palladium coating and a gold coating, has no magnetism, does not influence high-frequency and high-speed transmission of signals, can protect a conductive layer and provides good weldability, conductivity, corrosion resistance and friction resistance, and has lower production cost.

Detailed Description

The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention. In the embodiment of the invention, the normal temperature is 25 ℃.

Example 1

The test substrate in this example was a copper clad laminate, and the test samples were prepared according to the process flow in table 1:

TABLE 1

Serial number	Name of procedure	Temperature/. degree.C	Time/min
				1	Oil removal	40	4
2	Pure water washing	At normal temperature	0.5
				3	Micro etching	25	2
4	Pure water washing	At normal temperature	0.5
				5	Pre-impregnation	40	1
6	Preparation of silver layer	50	3
				7	Pure water washing	At normal temperature	0.5
8	Preparation of the Palladium layer	52	10
				9	Pure water washing	At normal temperature	0.5
10	Preparation of gold layer	80	8
				11	Pure water washing	At normal temperature	0.5

Table 1 process flow 6 the process for preparing the silver layer is: placing the copper-clad plate obtained in the process flow 5 in a chemical silver solution to obtain a silver layer, wherein the pH value of the chemical silver solution is 8.5, the concentration of silver ammonia complex ions in the chemical silver solution is 3g/L, the concentration of citric acid triamine is 10g/L, the concentration of glycine is 8g/L, and the concentration of citric acid is 10 g/L;

table 1 process flow 8 the process for preparing the palladium layer is: placing the product obtained in the process flow 7 in a chemical palladium solution to obtain a palladium layer, wherein the pH value of the chemical palladium solution is 7, the concentration of palladium sulfate in the chemical palladium solution is 3g/L, the concentration of sodium ethylene diamine tetracetate is 12g/L, the concentration of sodium citrate is 10g/L, the concentration of formic acid is 15g/L, the concentration of bismuth nitrate is 2mg/L, and the concentration of boric acid is 1 g/L;

table 1 process flow 10 the procedure for preparing the gold layer is: and (3) placing the product obtained in the process flow 9 into a chemical gold solution to obtain a gold layer, wherein the pH value of the chemical gold solution is 6.5, the concentration of potassium gold cyanide in the chemical gold solution is 3g/L, the concentration of acetohydroxamic acid is 15g/L, the concentration of lanthanum sulfate is 12mg/L, the concentration of 2, 2-dipyridine amine is 3mg/L, and the concentration of 2-morpholine ethanesulfonic acid is 10 g/L.

Example 2

The test substrate in this example was a copper clad laminate, and the test samples were prepared according to the process flow in table 2:

TABLE 2

Serial number	Name of procedure	Temperature/. degree.C	Time/min
				1	Oil removal	35	5
2	Pure water washing	At normal temperature	0.5
				3	Micro etching	23	2
4	Pure water washing	At normal temperature	0.5
				5	Pre-impregnation	35	1
6	Preparation of silver layer	40	4
				7	Pure water washing	At normal temperature	0.5
8	Preparation of the Palladium layer	40	15
				9	Pure water washing	At normal temperature	0.5
10	Preparation of gold layer	70	8
				11	Pure water washing	At normal temperature	0.5

Table 2 process flow 6 the process for preparing the silver layer is: placing the copper-clad plate obtained in the process flow 5 in a chemical silver solution to obtain a silver layer, wherein the pH value of the chemical silver solution is 9, the concentration of silver sulfite complex ions in the chemical silver solution is 5g/L, the concentration of ammonium phosphate is 20g/L, the concentration of alpha-alanine is 20g/L, and the concentration of sulfosalicylic acid is 20 g/L;

table 2 process flow 8 the process for preparing the palladium layer is: placing the product obtained in the process flow 7 in a chemical palladium solution to obtain a palladium layer, wherein the pH of the chemical palladium solution is 6.5, the concentration of palladium chloride in the chemical palladium solution is 5g/L, the concentration of ethylenediamine is 20g/L, the concentration of succinic acid is 25g/L, the concentration of ascorbic acid is 25g/L, the concentration of thiourea is 5mg/L, and the concentration of sodium dihydrogen phosphate is 5 g/L;

table 2 process flow 10 the process for preparing the gold layer is: and (3) placing the product obtained in the process flow 9 into a chemical gold solution to obtain a gold layer, wherein the pH value of the chemical gold solution is 6, the concentration of potassium gold citrate in the chemical gold solution is 5g/L, the concentration of benzohydroxamic acid is 20g/L, the concentration of cerium sulfate is 25mg/L, the concentration of 2, 4-lutidine is 5mg/L, and the concentration of citric acid-sodium citrate buffer solution is 25 g/L.

Example 3

The test substrate in this example was a copper clad laminate, and the test samples were prepared according to the process flow in table 3:

TABLE 3

Serial number	Name of procedure	Temperature/. degree.C	Time/min
				1	Oil removal	45	3
2	Pure water washing	At normal temperature	0.5
				3	Micro etching	27	1
4	Pure water washing	At normal temperature	0.5
				5	Pre-impregnation	45	1
6	Preparation of silver layer	70	2
				7	Pure water washing	At normal temperature	0.5
8	Preparation of the Palladium layer	70	4
				9	Pure water washing	At normal temperature	0.5
10	Preparation of gold layer	80	20
				11	Pure water washing	At normal temperature	0.5

Table 3 process flow 6 the process for preparing the silver layer is: placing the copper-clad plate obtained in the process flow 5 in a chemical silver solution to obtain a silver layer, wherein the pH value of the chemical silver solution is 8, the concentration of silver sulfite complex ions in the chemical silver solution is 0.5g/L, the concentration of ammonium acetate is 1g/L, the concentration of cystine is 1g/L, and the concentration of gluconic acid is 1 g/L;

table 3 process flow 8 the process for preparing the palladium layer is: putting the product obtained in the process flow 7 into a chemical palladium solution to obtain a palladium layer, wherein the pH value of the chemical palladium solution is 8, the concentration of palladium tetraammine dichloride in the chemical palladium solution is 0.1g/L, the concentration of ethylamine is 5g/L, the concentration of oxalic acid is 5g/L, the concentration of dimethylamine borane is 1g/L, the concentration of 2-mercaptobenzothiophene is 0.1mg/L, and the concentration of disodium hydrogen phosphate is 0.5 g/L;

table 3 process flow 10 the procedure for preparing the gold layer was: and (3) placing the product obtained in the process flow 9 into a chemical gold solution to obtain a gold layer, wherein the pH of the chemical gold solution is 7, the concentration of aurous chloride in the chemical gold solution is 0.1g/L, the concentration of salicylhydroxamic acid is 5g/L, the concentration of thallium sulfate is 1mg/L, the concentration of pyridine-2, 3 dihydroxy acid is 0.1mg/L, and the concentration of bis (2-hydroxyethylamino) trimethylolmethane is 1 g/L.

Comparative example 1

A nickel layer, a palladium layer and a gold layer were deposited on the experimental substrate in example 1, the thickness of the palladium layer and the gold layer being the same as in example 1, and the thickness of the nickel layer being the same as the thickness of the silver layer in example 1.

Performance testing

The products obtained in the examples and comparative examples were subjected to the following performance tests:

(1) coating thickness by using an X-RAY thickness gauge;

(2) passing through a 255 ℃ lead-free tin furnace, and testing the tin coating rate;

(3) 3M-610 adhesive tape is used for a cohesive force test, the phenomenon of plating throwing is not found and is marked as excellent, and the phenomenon of plating throwing is found and is marked as poor;

(4) testing the tensile force value of the gold wire after the wire bonding of the gold wire bonding machine;

(5) a 48H salt spray test was performed.

The performance test results are shown in table 4:

TABLE 4

As can be seen from Table 4 of the present invention, the coating structure obtained in the examples of the present invention meets the ICP standard. The comparative example 1 has poorer performance than the example 1, so that the silver layer is used for replacing the nickel layer to effectively reduce the surface roughness and improve the signal insertion loss capability.

The present invention is illustrated in detail by the examples described above, but the present invention is not limited to the details described above, i.e., it is not intended that the present invention be implemented by relying on the details described above. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A film coating structure is characterized by comprising a silver layer, a palladium layer and a gold layer which are sequentially arranged on a conductive layer.

2. The plating structure according to claim 1, wherein the thickness of the silver layer is 0.2 to 0.4 μm;

preferably, the thickness of the palladium layer is 0.05-0.2 μm;

preferably, the thickness of the gold layer is 0.05-0.2 μm.

3. A method for producing a coating structure according to claim 1 or 2, comprising: and sequentially preparing a silver layer, a palladium layer and a gold layer on the conducting layer to obtain the coating structure.

4. The method of claim 3, wherein the silver layer is prepared by a method comprising: performing a displacement reaction on the conductive layer to obtain a silver layer;

preferably, the preparation method of the silver layer comprises the following steps: placing the conductive layer in a chemical silver solution to obtain a conductive layer with a silver layer covered on the surface;

preferably, the pH value of the chemical silver solution is 8.0-9.0;

preferably, the temperature of the chemical silver solution is 40-70 ℃;

preferably, the conductive layer is placed in the chemical silver solution for 2-4 min;

5. The method of claim 3 or 4, wherein the chemical silver solution comprises silver ions or complexed silver ions, preferably the chemical silver solution further comprises any one or a combination of at least two of an amine complexing agent, an amino complexing agent and a polyhydroxy acid complexing agent, and further preferably the chemical silver solution consists of silver ions or complexed silver ions, an amine complexing agent, an amino complexing agent and a polyhydroxy acid complexing agent;

preferably, the concentration of silver ions or complex silver ions in the chemical silver solution is 0.5-5 g/L;

preferably, in the chemical silver solution, the concentration of the amine complexing agent is 1-20 g/L;

preferably, in the chemical silver solution, the concentration of the amino complexing agent is 1-20 g/L;

preferably, the concentration of the polyhydroxy acid complexing agent in the chemical silver solution is 1-20 g/L;

preferably, the silver ions or complexed silver ions include any one of or a combination of at least two of silver ammine complex ions, silver sulfite complex ions and silver halide complex ions;

preferably, the amine complexing agent comprises any one or a combination of at least two of ammonia water, triammonium citrate, ammonium phosphate, ammonium sulfate, ammonium nitrate, ammonium acetate, ammonium ethylene glycol carbonate, diethylenetriamine, aminopyridine of triethylenetetramine, aniline and phenylenediamine;

preferably, the amino complexing agent comprises any one or a combination of at least two of glycine, alpha-alanine, beta-alanine, cystine, ethylene diamine tetraacetic acid, aspartic acid, glutamic acid, nitrilotriacetic acid sulfamate and aromatic amino acid;

6. The method of any of claims 3-5, wherein the palladium layer is prepared by a method comprising: depositing a layer of metal palladium on the silver layer in an oxidation-reduction mode to obtain a palladium layer;

preferably, the preparation method of the palladium layer is as follows: placing the conducting layer with the surface covered with the silver layer in a chemical palladium solution to obtain a pre-product, wherein the palladium layer in the pre-product covers the surface of the silver layer;

preferably, the pH of the chemical palladium solution is 6.5-8.0;

preferably, the temperature of the chemical palladium solution is 40-70 ℃;

preferably, the conducting layer with the surface covered with the silver layer is placed in a chemical palladium solution for 4-15 min;

7. The method according to any one of claims 3 to 6, wherein the chemical palladium solution comprises a palladium salt, preferably the chemical palladium solution further comprises any one or a combination of at least two of a primary complexing agent, a secondary complexing agent, a reducing agent, a first stabilizing agent and a first pH buffer, further preferably the chemical palladium solution consists of palladium ions or palladium complex ions, a primary complexing agent, a secondary complexing agent, a reducing agent, a first stabilizing agent and a first pH buffer;

preferably, the concentration of the palladium salt is 0.1-5 g/L;

preferably, the concentration of the main complexing agent is 5-20 g/L;

preferably, the concentration of the auxiliary complexing agent is 5-25 g/L;

preferably, the concentration of the reducing agent is 1-25 g/L;

preferably, the concentration of the first stabilizer is 0.1-5 mg/L;

preferably, the concentration of the first pH buffering agent is 0.5-5 g/L;

preferably, the palladium salt comprises any one of palladium sulfate, palladium chloride, ammonium palladium chloride, palladium tetraammine dichloride and palladium ammonium sulfate or a combination of at least two of the palladium salt and the ammonium palladium chloride;

preferably, the main complexing agent is an amine compound, preferably comprising any one or a combination of at least two of ammonia water, ethylenediamine, ethylamine and sodium ethylenediamine tetracetate;

preferably, the auxiliary complexing agent comprises any one or a combination of at least two of sodium citrate, acrylic acid, succinic acid, oxalic acid and malic acid;

preferably, the reducing agent comprises any one of formic acid, hypophosphite, ascorbic acid and dimethylamine borane, or a combination of at least two thereof;

preferably, the first stabilizer comprises any one or a combination of at least two of bismuth nitrate, thiourea, 4-dimethylaminopyridine and 2-mercaptobenzothiophene;

8. The method according to any of claims 3 to 7, wherein the gold layer is prepared by a method comprising: depositing a layer of gold on the surface of the pre-product in an oxidation-reduction mode to obtain a gold layer;

preferably, the preparation method of the gold layer comprises the following steps: placing the pre-product in a chemical gold solution to obtain a coating structure;

preferably, the pH value of the chemical gold solution is 6.0-7.0;

preferably, the temperature of the chemical gold solution is 70-80 ℃;

preferably, the time for placing the pre-product in a chemical gold solution is 0.5-20 min;

preferably, after the coating structure is obtained, the process of washing and drying is also included, and pure water washing is preferably adopted;

preferably, the drying temperature is 60-90 ℃.

9. The method according to any one of claims 3 to 8, wherein the chemical gold solution comprises a gold salt, preferably the chemical gold solution further comprises any one or a combination of at least two of a complexing agent, an accelerator, a second stabilizer and a second pH buffer, further preferably the chemical gold solution consists of a gold salt, a complexing agent, an accelerator, a second stabilizer and a second pH buffer;

preferably, the concentration of the gold salt in the chemical gold solution is 0.1-5 g/L;

preferably, in the chemical gold solution, the concentration of a complexing agent is 5-20 g/L;

preferably, the concentration of the accelerator in the chemical gold solution is 1-25 mg/L;

preferably, the concentration of the second stabilizer in the chemical gold solution is 0.1-5 mg/L;

preferably, the concentration of the second pH buffering agent in the chemical gold solution is 1-25 g/L;

preferably, the gold salt includes any one of gold potassium cyanide, gold potassium citrate, gold chlorite chloride and tetrachloro acid hydrate or a combination of at least two thereof;

preferably, the complexing agent comprises any one of or a combination of at least two of acetohydroxamic acid, benzohydroxamic acid, salihydroxamic acid and acetylhydroxamic acid;

preferably, the accelerator comprises any one of lanthanum sulfate, cerium sulfate and thallium sulfate or a combination of at least two of the same;

preferably, the second stabilizer comprises any one of 2, 2-dipyridyl amine, 2, 4-dimethylpyridine, 2, 4-dimethylpiperidine and pyridine-2, 3 dicarboxylic acid or a combination of at least two thereof;

10. The method according to any one of claims 3 to 9, wherein the conductive layer further comprises a degreasing and microetching process before the silver layer is formed;

preferably, the washing is washing with pure water.