阅读说明：本技术 一种电镀液及其电镀方法和应用 (Electroplating solution and electroplating method and application thereof ) 是由 熊海平 王莉 章晓冬 刘江波 童茂军 于 2021-06-21 设计创作，主要内容包括：本发明涉及一种电镀液及其电镀方法和应用,所述电镀液按照质量浓度包括如下组分：五水硫酸铜75-300g/L,浓硫酸30-250g/L,氯离子0.03-0.12g/L和亚铁离子1-15g/L。本发明所述电镀液使用时添加剂的消耗量较低,阳极几乎不发生析氧,可解决不溶性阳极析氧的问题,且铜箔的断裂伸长率维持在较高水平,同时具有良好的盲孔填充效果。(The invention relates to an electroplating solution, an electroplating method and application thereof, wherein the electroplating solution comprises the following components in percentage by mass: 75-300g/L of blue vitriol, 30-250g/L of concentrated sulfuric acid, 0.03-0.12g/L of chloride ion and 1-15g/L of ferrous ion. The electroplating solution disclosed by the invention has the advantages that the consumption of additives is low when the electroplating solution is used, oxygen evolution hardly occurs at the anode, the problem of insoluble anode oxygen evolution can be solved, the elongation at break of the copper foil is maintained at a high level, and meanwhile, the electroplating solution has a good blind hole filling effect.)

1. The electroplating solution is characterized by comprising the following components in percentage by mass: 75-300g/L of blue vitriol, 30-250g/L of concentrated sulfuric acid, 0.03-0.12g/L of chloride ion and 1-15g/L of ferrous ion.

2. The electroplating bath as recited in claim 1 wherein the ferrous ion mass concentration is between 3 and 10 g/L.

3. The electroplating bath according to claim 1 or 2, wherein the supply of ferrous ions comprises any one or a combination of at least two of iron-containing inorganic salts and derivatives thereof, iron-containing organic salts and derivatives thereof, iron-containing oxides or iron-containing hydroxides.

4. The electroplating bath according to any one of claims 1-3, wherein the iron-containing inorganic salt comprises any one or a combination of at least two of ferrous sulfate, ferrous chloride, ferrous carbonate, ferrous nitrate, ferric ferrocyanide, potassium ferricyanide, potassium ferrate, or sodium ferrate;

preferably, the iron-containing inorganic salt derivative includes an iron-containing inorganic salt containing crystal water;

preferably, the iron-containing organic salt comprises any one of ferrous formate, ferrous acetate or ferrous lactate or a combination of at least two of them.

5. The electroplating bath according to claim 3, wherein the iron-containing oxide comprises ferrous oxide;

preferably, the iron-containing hydroxide comprises ferrous hydroxide;

preferably, the supply of chloride ions comprises a chloride salt and/or hydrochloric acid;

preferably, the chloride salt comprises potassium chloride and/or sodium chloride.

6. The electroplating bath as set forth in any one of claims 1 to 5 further comprising an electroplating additive;

preferably, the plating additive comprises any one of an accelerator, leveler or carrier, or a combination of at least two thereof;

preferably, the volume concentration of the accelerator in the electroplating solution is 1-5 mL/L;

preferably, the volume concentration of the leveling agent in the electroplating solution is 5-30 mL/L;

preferably, the carrier has a concentration of 5-20mL/L by volume in the electroplating solution.

7. A plating method of a plating solution according to any one of claims 1 to 6, comprising the steps of:

a printed wiring board with blind holes is subjected to electroless copper plating, pickling and then immersed in the plating solution according to any one of claims 1 to 6 for plating.

8. The plating method by an electroplating solution according to claim 7, wherein the current density is 1 to 5 ASD;

preferably, the electroplating time is 0.5-2 h;

preferably, the temperature of the electroplating is 23-30 ℃.

9. The plating method of a plating solution as recited in claim 7 or 8, characterized by comprising the steps of:

the printed circuit board with blind holes is subjected to electroless copper plating, pickling and then immersed in the electroplating solution of any one of claims 1 to 6, and electroplated at a current density of 1 to 5ASD for 0.5 to 2.0 hours at a temperature of 23 to 30 ℃ to complete the electroplating.

10. A method for addressing insoluble anodic oxygen evolution, the method comprising: use of the electroplating solution as claimed in any one of claims 1 to 6 for insoluble anodic copper electroplating.

Technical Field

The invention relates to the technical field of electroplating, in particular to electroplating solution and an electroplating method and application thereof.

Background

Within the printed circuit board (PCB or PWB) manufacturing industry, there are two common anodes used in acid copper electroplating, one being the traditional soluble anode, i.e. the phosphor copper ball anode; one is insoluble anode such as titanium plate or titanium mesh with surface processed by oxide layer. Compared to electrolytically soluble phosphor-copper anodes, insoluble anodes have at least two distinct advantages: firstly, no anode mud is generated in the production process, the anode mud in the anode bag and the anode fence does not need to be cleaned in a production stop process, and the phosphorus-copper ball anode does not need to be supplemented frequently, so that the production efficiency can be improved, and the production cost can be reduced; second, the use of insoluble anodes allows for electroplating with large current densities, increasing the capacity per unit time.

According to the electrochemistry and electrode reaction principle, after the anode in the electrolytic tank of the electroplated copper is replaced by an insoluble anode, the anode reaction formula is as follows: h₂O→1/2O₂+2e^-+2H⁺It can be seen that insoluble anodic oxygen evolution is almost an unavoidable phenomenon in the electroplating process. Two main hazards exist in the anodic oxygen evolution, firstly, the more the current density is, the more the generated oxygen is, the more the oxygen is, the great destructiveness of the oxygen which is greatly precipitated on the oxide treatment layer on the surface of the anode is, and the service life of the anode is influenced; secondly, the anodic oxygen evolution causes the additive, especially the accelerator, in the plating solution to be consumed in a large amount, and excessive decomposition products are generated, so that on one hand, the additive supplement amount is greatly increased, the maintenance cost of a liquid medicine supplier is increased, on the other hand, the decomposition products influence the service performance of the plating solution, and the service cycle of the plating solution is shortened.

CN111850625A discloses an electroplating solution for direct electrodeposition of iron on magnesium alloy surface and an electroplating process thereof, wherein the electroplating solution comprises the following components in concentration: 1-300g/L of water-soluble ferric salt/ferrous salt, 1-1000g/L of citric acid and/or citrate, 1-50g/L of sodium fluoride, 0.01-200g/L of surfactant, 0.1-500g/L of auxiliary coordination agent and 1-1000mL/L of ammonia water, and water is used as a solvent. The electroplating solution disclosed by the method can be used for electrodepositing iron on the surface of the magnesium alloy by one-step method, the prepared pure iron plating layer is compact and uniform, has good binding force, good biocompatibility, degradability and stable effect, can provide effective corrosion protection for a magnesium alloy matrix, can realize controllable preparation of plating layer morphology, grain size, thickness and the like, and is used for electroplating solution for directly electrodepositing iron on the surface of the magnesium alloy.

CN101792917A discloses a preparation method and an electroplating method of a normal-temperature environment-friendly sulfate trivalent chromium electroplating solution, which solves the problems of the prior artThe problems of poor stability of trivalent chromium electroplating solution, low harmful gas separation and deposition rate in the electroplating process, more components of the electroplating solution, sensitivity to impurities, poor corrosion resistance of the plating layer and the like. The disclosed normal-temperature environment-friendly sulfate trivalent chromium electroplating solution consists of main salt, a complexing stabilizer, a combined additive, a buffering agent and conductive salt. The disclosed plating solution can be operated at normal temperature, saves energy, has simple process and high deposition rate of 6A/dm²The deposition rate can reach 0.22 mu m.min^-1In the method, the anode adopted by the method is a titanium-based rare metal tantalum iridium titanium coating anode, the oxygen evolution overpotential of the anode is low, harmful hexavalent chromium is not generated, and the method has good corrosion resistance and high stability. The electroplating method disclosed in the patent has the advantage that the electroplated copper anode has a large amount of oxygen evolution, and the problem of oxygen evolution is overcome mainly by improving the anode material.

At present, in the PCB industry, except a passive method of isolating and separating out oxygen by using a diaphragm or an anode bag, no method for better solving the problem of anode oxygen separation exists, and most of the situations need to adopt a mode of adding a large amount of additives to maintain a production line.

In view of the foregoing, it is important to develop a plating solution that can reduce the use of additives and solve the problem of anodic oxygen evolution.

Disclosure of Invention

The invention aims to provide a plating solution, a plating method and application thereof, aiming at overcoming the defects of the prior art, the consumption of an accelerator is low when the plating solution is used, oxygen evolution hardly occurs at an anode, the problem of insoluble anode oxygen evolution can be solved, the elongation at break of a copper foil is maintained at a high level, and meanwhile, a good blind hole filling effect is achieved.

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

in a first aspect, the present invention provides an electroplating solution, comprising the following components by mass: 75-300g/L of blue vitriol, 30-250g/L of concentrated sulfuric acid, 0.03-0.12g/L of chloride ion and 1-15g/L of ferrous ion.

The invention provides an electroplating solution, when ferrous ions in an acidic copper plating solution reach a certain concentration, the anode reaction is as follows: fe²⁺→Fe³⁺+e^-Thereby avoiding the electrolysis of water to generate oxygen and fundamentally solving the problem of oxygen evolution of the anode. Therefore, on one hand, after the plating solution contains a certain amount of ferrous ions, no oxygen is generated on the anode, the oxide damage on the surface of the anode is reduced, and the service life of the anode is prolonged; on the other hand, the consumption of the additive is reduced, the production and maintenance cost is reduced, the generation of electrolytic waste is reduced, and the service life of the plating solution is prolonged.

The mass concentration of the copper sulfate pentahydrate is 75-300g/L, such as 75g/L, 100g/L, 120g/L, 150g/L, 180g/L, 200g/L, 220g/L, 250g/L, 280g/L and the like.

The mass concentration of the concentrated sulfuric acid is 30-250g/L, such as 40g/L, 50g/L, 60g/L, 70g/L, 75g/L, 100g/L, 120g/L, 140g/L, 160g/L, 180g/L, 200g/L, 220g/L and the like. The concentration of the concentrated sulfuric acid is 98%.

The mass concentration of the chloride ions is 0.03-0.12g/L, such as 0.04g/L, 0.06g/L, 0.08g/L, 0.1g/L and the like.

The mass concentration of the ferrous ions is 1-15g/L, such as 2g/L, 4g/L, 5g/L, 6g/L, 8g/L, 10g/L, 12g/L, 14g/L, 15g/L and the like.

Preferably, the mass concentration of the ferrous ions is 3-10g/L, such as 3g/L, 4g/L, 5g/L, 6g/L, 7g/L, 8g/L, 9g/L, and the like. Ferrous ions in the range can obtain better blind hole filling effect, and the oxygen evolution of the anode is less.

Preferably, the supply of ferrous ions comprises any one or a combination of at least two of iron-containing inorganic salts and derivatives thereof, iron-containing organic salts and derivatives thereof, iron-containing oxides or iron-containing hydroxides.

Preferably, the iron-containing inorganic salt comprises any one of ferrous sulfate, ferrous chloride, ferrous carbonate, ferrous nitrate, ferric ferrocyanide, potassium ferricyanide, potassium ferrate or sodium ferrate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: combinations of ferrous sulfate and ferrous chloride, ferrous carbonate, combinations of ferrous nitrate and ferric ferrocyanide, combinations of ferrous nitrate, ferric ferrocyanide, potassium ferricyanide, potassium ferrate and sodium ferrate, and the like.

The ferrocyanide provided by the invention comprises the Turnbull blue and/or Prussian blue.

Preferably, the iron-containing inorganic salt derivative includes an iron-containing inorganic salt containing crystal water.

Preferably, the iron-containing organic salt comprises any one of ferrous formate, ferrous acetate or ferrous lactate, or a combination of at least two thereof, wherein typical but non-limiting combinations include: a combination of ferrous formate and ferrous acetate, a combination of ferrous acetate and ferrous lactate, a combination of ferrous formate, ferrous acetate and ferrous lactate, and the like.

Preferably, the iron-containing oxide comprises ferrous oxide.

Preferably, the iron-containing hydroxide comprises ferrous hydroxide.

Preferably, the supply of chloride ions comprises a chloride salt and/or hydrochloric acid. The supply of chloride ions according to the present invention requires a level of chemical purity above.

Preferably, the chloride salt comprises potassium chloride and/or sodium chloride.

Preferably, the electroplating bath further comprises an electroplating additive.

Preferably, the plating additive comprises any one of, or a combination of at least two of, an accelerator, a leveler, or a carrier, preferably a combination of an accelerator, a leveler, and a carrier.

Preferably, the accelerator is present in the plating solution at a volume concentration of 1-5mL/L, e.g., 1.0mL/L, 1.2mL/L, 1.5mL/L, 1.8mL/L, 2.0mL/L, 2.5mL/L, 3.0mL/L, 4.0mL/L, 5.0 mL/L, and the like.

Preferably, the leveler is present in the plating solution at a volume concentration of 5-30mL/L, such as 5mL/L, 10mL/L, 15mL/L, 20mL/L, 25mL/L, 30mL/L, and the like.

Preferably, the volume concentration of the carrier in the electroplating solution is 5-20mL/L, such as 5mL/L, 10mL/L, 15mL/L, 20mL/L, and the like.

In a second aspect, the present invention provides a plating method of the plating solution of the first aspect, comprising the steps of:

and (3) chemically plating copper and acid on the printed circuit board with the blind hole, and then immersing the printed circuit board into the electroplating solution of the first aspect for electroplating.

Preferably, the current density of the plating is 1 to 5ASD, such as 1.5ASD, 1.6ASD, 1.8ASD, 2.0ASD, 2.2ASD, 2.5ASD, 3ASD, 3.5ASD, 4ASD, 4.5ASD, etc., preferably 1 to 3ASD, and more preferably 1.8 ASD.

Preferably, the time of the electroplating is 0.5-2h, such as 0.5h, 1h, 1.5h, 2h, etc.

Preferably, the temperature of the plating is 23-30 deg.C, such as 24 deg.C, 25 deg.C, 26 deg.C, 27 deg.C, 28 deg.C, 29 deg.C, etc., preferably 23-25 deg.C.

As a preferable technical solution, the electroplating method comprises the steps of:

and (2) chemically plating copper on the printed circuit board with the blind hole, pickling, immersing into the electroplating solution of the first aspect, and electroplating for 0.5-2h at 23-30 ℃ and at the current density of 1-5ASD to finish electroplating.

In a third aspect, the present invention provides a method for addressing insoluble anodic oxygen evolution, the method comprising: the plating solution described in the first aspect is used for insoluble anodic electrolytic copper plating.

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

when the electroplating solution is used, the consumption of the electroplating additive is low, oxygen evolution hardly occurs at the anode, the problem of insoluble anode oxygen evolution can be solved, the elongation at break of the copper foil is maintained to be more than 22.2%, and meanwhile, the electroplating solution has a good blind hole filling effect, the aperture is 150 micrometers, the medium depth is 85 micrometers, and the diamond value is less than 5.95 micrometers.

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.

Example 1

This example provides an electroplating bath for insoluble anodic copper electroplating without oxygen evolution at the anode, said bath consisting of: 235g/L of blue vitriol, 50g/L of concentrated sulfuric acid, 0.07g/L of chloride ion (the chloride ion provider is sodium chloride), 3g/L of ferrous ion (the ferrous ion provider is CP-grade ferrous acetate, produced by Clematis yunnanensis biology), and the electroplating additive is a direct-current blind hole electroplating filling additive which is purchased from Guangdong-Tian-Tu-Tech-Sico Ltd and is provided with SkyPlate Cu 6382B accelerator, SkyPlate Cu 6382L leveler and SkyPlate Cu 6382C carrier, and the adding amounts of the three are 1mL/L, 25mL/L and 15mL/L respectively.

The present embodiment also provides an electroplating method, including the following steps:

a PCB with the thickness of 1.0 mm, drilled with blind holes with the aperture of 150 microns and the depth of 85 microns is subjected to electroless copper plating to obtain a copper layer with the thickness of 0.2 micron of bottom copper, and then is subjected to pickling (10% sulfuric acid solution at room temperature for 1.0 minute), a titanium mesh anode with a metal tantalum and iridium oxide layer attached to the surface is used in the blind hole copper electroplating solution for electroplating for 70 minutes at the temperature of 23 ℃, and the direct-current blind hole filling electroplating is completed, wherein no obvious oxygen evolution phenomenon occurs on the titanium anode in the electroplating process.

Example 2

This example provides an electroplating bath for insoluble anodic copper electroplating without oxygen evolution at the anode, said bath consisting of: 235g/L of blue vitriol, 60g/L of concentrated sulfuric acid, 0.07g/L of chloride ion (sodium chloride is provided as a chloride ion provider), 5g/L of ferrous ion (CP-grade ferrous hydroxide is provided as a ferrous ion provider, produced by Shiga chemical industry), and the additives are direct current blind hole electroplating filling additives which are purchased from Guangdong Sudoku Kogyo Co., Ltd and are provided with Skyplate Cu 6382B accelerator, Skyplate Cu 6382L leveler and Skyplate Cu 6382C carrier, and the adding amounts of the three are 1mL/L, 25mL/L and 15mL/L respectively.

The present embodiment also provides an electroplating method, including the following steps:

a PCB with the thickness of 1.0 mm, drilled with blind holes with the aperture of 150 microns and the depth of 85 microns is subjected to electroless copper plating to obtain a copper layer with the thickness of 0.2 micron of bottom copper, and then is subjected to pickling (10% sulfuric acid solution at room temperature for 1.0 minute), a titanium mesh anode with a metal tantalum and iridium oxide layer attached to the surface is used in the blind hole copper electroplating solution for electroplating for 50 minutes at the temperature of 23 ℃, and the direct-current blind hole filling electroplating is completed, wherein no obvious oxygen evolution phenomenon exists on the titanium anode in the electroplating process.

Example 3

This example provides an electroplating bath for insoluble anodic copper electroplating without oxygen evolution at the anode, said bath consisting of: 235g/L of blue vitriol, 50g/L of concentrated sulfuric acid, 0.07g/L of chloride ion (sodium chloride is provided as a chloride ion provider), 10g/L of ferrous ion (CP-grade ferrous sulfate is provided as a ferrous ion provider, produced by Xiong chemical industry), and the additives are direct current blind hole electroplating filling additives which are purchased from Guangdong Sudoku Kogyo Co., Ltd and are provided with Skyplate Cu 6382B accelerator, Skyplate Cu 6382L leveler and Skyplate Cu 6382C carrier, and the adding amounts of the three are 1mL/L, 25mL/L and 15mL/L respectively.

The present embodiment also provides an electroplating method, including the following steps:

a PCB with the thickness of 1.0 mm, drilled with blind holes with the aperture of 150 microns and the depth of 85 microns is subjected to electroless copper plating to obtain a copper layer with the thickness of 0.2 micron of bottom copper, and then is subjected to pickling (10% sulfuric acid solution at room temperature for 1.0 minute), a titanium mesh anode with a metal tantalum and iridium oxide layer attached to the surface is used in the blind hole electroplating copper plating solution, electroplating is carried out for 40 minutes at the temperature of 23 ℃, direct-current blind hole filling electroplating is completed, and the anode is subjected to anaerobic precipitation in the electroplating process.

Examples 4 to 7

Examples 4 to 7 differ from example 1 in that the ferrous ion mass concentrations were 1g/L, 15g/L, 0.1g/L and 20g/L, respectively, and the rest was the same as example 1.

Comparative example 1

This comparative example differs from example 1 in that the plating solution does not include ferrous ions, i.e., no ferrous ion donor is added, and is otherwise the same as example 1.

Performance testing

The plating solutions described in examples 1 to 7 and comparative example 1 were subjected to the following tests:

(1) blind hole filling effect:

and after electroplating, taking a PCB section with the blind hole area of about 20mm multiplied by 15mm, carrying out rough grinding, fine grinding and polishing on the polished copper surface, observing the filling state of the blind hole by using an OLYMPUS BX53M type metallographic microscope, and taking a picture. The industry requires: for blind vias with a pore size of less than 150 microns and a depth of less than 75 microns, the Dimple depth (sample) should be less than 10 microns after filling.

(2) Addition amount of accelerator: before and after electroplating, samples are respectively taken from electroplating bath liquid, the content of the accelerator Cu 6382B is analyzed by an ECI QL-10EX CVS instrument, the difference between the front and the back is the consumption of the accelerator, the smaller the consumption of the additive is, the better the additive is, and the normal consumption of the Cu 6382B is 30-60 mL/KAH.

(3) Elongation at break of copper foil: a50-80 micrometer copper layer is electroplated on a clean stainless steel plate, the copper layer is stripped, then the copper layer is baked for 2 hours at 150 ℃ in an oven, then the copper foil is respectively cut into copper strips with the thickness of 13mm x150mm according to the longitudinal direction and the transverse direction, and the test is carried out by using a TH-8203S type fracture extensometer produced by Suzhou Tubo mechanical equipment Limited and according to IPC-TM-6502.18.1 standard. The elongation at break is required to be not less than 15 percent by the industry, and the product is qualified.

(4) Anodic oxygen evolution status: observing the bubble condition of the surface of the plating solution in the anode bag in the electroplating process, and sequentially dividing the anode bag into 0 level, 1 level, 2 level and 3 level according to the oxygen evolution quantity, wherein the 0 level has no oxygen evolution, and the 3 level has the most serious oxygen evolution;

(5) the crystallization conditions in the electroplating solution are divided into 0 grade, 1 grade and 2 grade according to the deepening condition of the degree, wherein the 0 grade has no crystallization, the 1 grade has slight crystallization and the 2 grade has large amount of crystallization.

The test results are summarized in table 1.

TABLE 1

The data in the table 1 are analyzed, so that the condition of the electroplating solution and the extensibility of the electroplated copper layer are not obviously affected after ferrous ions are added into the electroplating solution, and the elongation at break of the copper foil is maintained to be more than 22.2 percent; the anode of the electroplating solution of the invention hardly generates oxygen evolution condition in the electroplating process, the problem of insoluble anode oxygen evolution can be solved, the consumption of the used accelerator SkyPlate 6382B is obviously reduced, the consumption of the accelerator in the preferable range of the embodiments 1-3 is below 50mL/KAH, and simultaneously, the electroplating solution has good blind hole filling effect, the aperture is 150 microns, the medium depth is 85 microns, and the Dimple value is below 5.95 microns.

Analysis of comparative example 1 and example 1 shows that the consumption of the accelerator 6382B in comparative example 1 is too large, and the performance is inferior to that in example 1, which proves that the added ferrous ions can effectively improve the oxygen evolution condition of the anode, and greatly reduce the consumption of the accelerator.

Analysis of examples 4-7 shows that in example 6, due to the low ferrous ion addition, the anode has significant oxygen evolution, resulting in excessive accelerator consumption. The plating solution of example 7, in which filtered ferrous ions were added to the plating solution, was too high in the content of the main salt in the plating solution to form a supersaturated solution and thereby a large amount of crystals were precipitated, was not stable as in examples 4 to 5, and it was confirmed that the plating solution having a ferrous ion concentration in the range of 1 to 15g/L was more advantageous for the plating process.

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.