Method for preparing PCB (Printed Circuit Board) fine circuit through high-efficiency pulse electrolytic chemical synergy etching

Abstract

The invention relates to the technical field of printed circuit board fine circuit preparation, in particular to a method for preparing a PCB fine circuit through efficient pulse electrolytic chemical synergy etching, according to the method for preparing the PCB fine circuit through etching, high pulse peak current density is generated through one-way pulse current, use of reverse pulse current is avoided, and the circuit quality is improved. And meanwhile, the current control is simplified. Moreover, through the synergistic effect of the high pulse peak current density and the limited duty ratio, under the high pulse peak current density, the electrolytic etching speed can be increased, the electrolytic etching time can be greatly shortened, the corrosion effect of chemical etching on the circuit is relatively weakened, and the side corrosion of the circuit is small. Due to the fact that the electrolytic etching speed is high, the electrolytic etching time is short, electrolytic etching is used as a leading part, and chemical etching is used as a supplement part, a corrosion inhibitor does not need to be used in the electrolytic etching solution, and the method has the advantages of being simple in process, low in preparation cost, high in etching speed, good in etching uniformity, high in production efficiency and good in circuit quality and reliability.

Description

Technical Field

[0001] The invention relates to the technical field of fine circuit preparation of printed circuit boards, and in particular to a method for preparing fine circuits of PCBs by high-efficiency pulse electrolytic chemical coordinated etching. Background Art

[0002] As electronic devices continue to miniaturize and become more functional, this has driven printed circuit boards (PCBs) toward finer and more complex circuit designs. The production of fine circuits is a crucial part of PCB manufacturing, which is directly related to the performance and reliability of electronic equipment. From the early 200μm / 200μm line width and line spacing to today's 50μm / 50μm, or even smaller, this progress has significantly improved the integration and reliability of electronic equipment. In the traditional chemical etching process, the side etching phenomenon is becoming increasingly prominent when making PCB circuits, the stability of the etching solution is difficult to control, and the high copper content in the etching waste liquid makes recycling and treatment challenging. These problems not only affect the quality of the circuit, but also increase environmental pollution and production costs. Therefore, the industry urgently needs to innovate PCB circuit manufacturing technology to improve circuit quality, reduce environmental impact, and reduce costs.

[0003] The electrolytic etching technology, based on electrochemical principles, effectively improves the quality of PCB circuits and recycles copper resources through anodic oxidation and cathodic reduction reactions. It is an effective method that complies with the concept of environmental protection and sustainable production. The Chinese patent application with patent number 202411062830.7 discloses "a circuit board electrolytic etching solution and its preparation method and application". This method uses methanesulfonic acid electrolytic etching solution, adds compound additives, combines characteristic pulse current, and has an anode current density of 0.5 to 2A / dm 2 , which can effectively reduce the circuit side corrosion. The patent application technology uses a pulsed reverse current, which allows the circuit board to be etched to act as both an anode for electrolytic copper stripping and a cathode for copper deposition during the etching process. This bidirectional current action will lead to a waste of resources, because the simultaneous stripping and deposition of copper during circuit preparation may reduce the overall efficiency and increase the consumption of electricity and materials.

[0004] The Chinese patent application with patent application number 201810601061.1 discloses "A technology for electrolytic etching of PCB fine circuits and associated copper recovery". This method uses copper chloride and hydrochloric acid as the basic electrolyte, recovers metallic copper in the electrolyte while making fine circuits, and reduces materials and waste.

[0005] However, in the above existing fine line manufacturing technologies, the current density used is usually less than 3A / dm 2Under such conditions, the electrolytic etching speed is slow, resulting in low production efficiency, increased costs and unnecessary consumption of resources. In addition, the electrolytic etching solution for preparing fine circuits of PCB in the prior art usually needs to add corrosion inhibitors to prevent or slow down the corrosion of the anode, but the corrosion inhibitors are mostly organic matter, which is easy to pollute the environment and also cause the defect of high raw material cost. Summary of the invention

[0006] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a method for preparing PCB fine circuits by efficient pulse electrolytic chemical synergistic etching. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical synergistic etching has the advantages of fast etching speed, high production efficiency, low preparation cost, and no need to use corrosion inhibitors. It can efficiently, high-quality and quickly manufacture PCB fine circuits, while improving the quality and reliability of the fine circuits.

[0007] In order to achieve the purpose of the above invention, the technical solution adopted by the present invention is as follows:

[0008] The present invention provides a method for preparing fine circuits of PCB by efficient pulse electrolytic chemical coordinated etching, wherein copper ions, iron ions, hydrochloric acid and water are used to prepare an electrolytic etching solution, a circuit board to be etched is used as an anode, a titanium plate or a stainless steel plate is used as a cathode, a high pulse peak current density is generated by a unidirectional pulse current, and the circuit board to be etched is etched to prepare fine circuits of PCB;

[0009] The unidirectional pulse current is a forward pulse current, and the forward pulse current density is 5A / dm 2 ~500A / dm 2 The duty cycle of the forward pulse current is 0.1 to 0.95, and the duration of each forward pulse stage is 10 ms to 1000 ms.

[0010] The circuit board to be etched is a circuit pattern board whose surface is protected by a dry film.

[0011] The invention discloses a method for preparing fine circuits of PCB by high-efficiency pulse electrolytic chemical synergistic etching. By adopting unidirectional pulse current to generate high pulse peak current density, the use of reverse pulse current is avoided, and current control is also simplified. In addition, the high pulse peak current density is synergistically acted with a limited duty cycle. 2 ~500A / dm 2), the electrolytic etching rate is fast, and a large amount of copper layers can be quickly peeled off, while the copper layer protected by the dry film will not be etched due to the considerable electrochemical resistance, so under this electric field selectivity condition, the electric field only etches the copper layer not protected by the dry film, and the copper layer protected by the dry film is left, gradually forming a circuit. In addition, since chemical etching is non-selective and easily causes side corrosion to the circuit, the present invention can accelerate the electrolytic etching speed by using a high pulse peak current density, and can greatly shorten the electrolytic etching time, relatively weaken the corrosion effect of chemical etching on the circuit, and the circuit side corrosion is small. Since the electrolytic etching speed is fast, the electrolytic etching time is short, and electrolytic etching is used as the leading factor and chemical etching is used as a supplement, therefore, there is no need to use a corrosion inhibitor in the electrolytic etching solution, and therefore, the method for preparing PCB fine circuits by etching of the present invention can improve production efficiency and reduce preparation costs on the one hand, and can manufacture PCB fine circuits efficiently, with high quality and quickly on the other hand, while improving the quality and reliability of fine circuits.

[0012] Since the electric field distribution may be non-uniform, some copper layers or copper particles may not be etched during the etching process, and these remaining copper layers or copper particles form an "island" system. In this regard, the electrolytic etching solution system provided by the present invention contains high concentrations of iron ions and copper ions, and thus has a strong chemical etching ability, which can quickly assist in chemically etching the copper layers or copper particles remaining after electrolytic etching, effectively deal with the non-uniformity that may occur during the electrolytic etching process, and help the copper etching of the circuit board to form fine circuits. Therefore, through the synergy of chemical etching, the uniformity and efficiency of etching are further improved.

[0013] The invention discloses a method for preparing fine circuits of PCB by high-efficiency pulse electrolytic chemical synergistic etching. The method comprises unidirectional pulse waveform electrolytic etching, and an electrolytic etching solution prepared by copper ions, iron ions, hydrochloric acid and water is used. The method can generate 5A / dm 2 ~500A / dm 2 The high pulse peak current density is used for electrolytic etching to prepare PCB fine circuits, which has the advantages of high efficiency and high quality. For the preparation of fine circuits with a line width and line spacing of 50μm, the etching factor can reach about 7.77. Therefore, the method of etching to prepare PCB fine circuits in this application has a very broad application prospect.

[0014] Furthermore, in the electrolytic etching solution, the concentration of the copper ions is 10 g / L to 90 g / L.

[0015] Furthermore, in the electrolytic etching solution, the concentration of the iron ions is 10 g / L to 90 g / L.

[0016] The concentrations of copper ions and iron ions defined in the present invention can effectively handle the non-uniformity that may occur during electrolytic etching, and help to form fine circuits by copper etching of circuit boards. Therefore, through the synergy of chemical etching, the uniformity and efficiency of etching are further improved.

[0017] Furthermore, in the electrolytic etching solution, the concentration of the hydrochloric acid is 0.5 mol / L to 1.5 mol / L, wherein the concentration of the hydrochloric acid can make the electrolytic etching solution have sufficient hydrogen ions, thereby having good conductivity.

[0018] Furthermore, the copper ion is at least one of anhydrous copper chloride, dihydrated copper chloride or copper sulfate; wherein anhydrous copper chloride, dihydrated copper chloride or copper sulfate can dissolve copper ions well, and anhydrous copper chloride and / or copper sulfate have the characteristics of easy availability of raw materials and low cost. And / or

[0019] The iron ion is at least one of ferric chloride, ferric oxide and ferric sulfate. Among them, ferric chloride can dissolve iron ions well, and ferric oxide can generate iron ions under the action of hydrochloric acid. Moreover, ferric chloride and ferric oxide have the characteristics of easy availability of raw materials and low cost.

[0020] Furthermore, during the etching process, the temperature of the electrolytic etching solution is 20° C. to 45° C. This temperature can increase the ion mass transfer rate in the electrolytic etching solution, accelerate the ion exchange between circuits, and thus accelerate the etching speed, shortening the time for preparing fine PCB circuits.

[0021] Further, preferably, the duty cycle of the forward pulse current is 0.2-0.8. In the present invention, in the electrolytic etching of the pulse current, the appropriate duty cycle not only helps to improve the current efficiency, but also promotes the rapid exchange of cupric ions or cuprous ions during the off time, thereby timely updating the electrolytic etching solution between the circuits, thereby enhancing the efficiency of circuit etching. In addition, the duty cycle can also provide a certain amount of time to timely exchange and process a large amount of electrolytic etching products generated instantly between the circuits, prevent them from hindering the etching process, and improve the circuit etching factor.

[0022] Further, preferably, the duration of each forward pulse phase is 40 ms to 500 ms.

[0023] Furthermore, the time for etching the circuit board to be etched to prepare the PCB fine circuit is 85s to 200s. Since the present application uses a unidirectional pulse current to generate a high pulse peak current density for electrolytic etching, and simultaneously cooperates with the electrolytic etching solution for chemical etching, it has the advantages of fast etching speed and short circuit preparation time.

[0024] Furthermore, during the process of etching to prepare fine PCB circuits, the electrolytic etching solution is stirred.

[0025] The uniformity of the distribution of the electrolytic etching solution can be improved by stirring, and the stirring method includes at least one of mechanical stirring, spray stirring, air flow stirring, circulating pumping, magnetic stirring, and ultrasonic stirring. The flow rate of air flow stirring is set to 2L / min to 10L / min. Since a large amount of etching products will be generated during the electrolytic etching process, these etching products can be removed in time by stirring to avoid hindering the etching process and affecting the etching factor.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The present invention provides a method for preparing fine circuits of PCB by high-efficiency pulse electrochemical synergistic etching, which avoids the use of reverse pulse current by using unidirectional pulse current to generate high pulse peak current density, and simplifies current control. In addition, the high pulse peak current density and the limited duty cycle work together to achieve a high pulse peak current density (5A / dm 2 ~500A / dm 2 ), the electrolytic etching rate is fast, and a large amount of copper layers can be quickly peeled off, while the copper layer protected by the dry film will not be etched due to the considerable electrochemical resistance, so under this electric field selectivity condition, the electric field only etches the copper layer not protected by the dry film, and the copper layer protected by the dry film is left, gradually forming a circuit. In addition, since chemical etching is non-selective and easily causes side corrosion to the circuit, the present invention can accelerate the electrolytic etching speed by using a high pulse peak current density, and can greatly shorten the electrolytic etching time, relatively weaken the corrosion effect of chemical etching on the circuit, and the circuit side corrosion is small. Since the electrolytic etching speed is fast, the electrolytic etching time is short, and electrolytic etching is used as the leading factor and chemical etching is used as a supplement, therefore, there is no need to use a corrosion inhibitor in the electrolytic etching solution, and therefore, the method for preparing PCB fine circuits by etching of the present invention can improve production efficiency and reduce preparation costs on the one hand, and can manufacture PCB fine circuits efficiently, with high quality and quickly on the other hand, while improving the quality and reliability of fine circuits.

[0028] (2) The present invention provides a method for preparing fine circuits of PCB by high-efficiency pulse electrolytic chemical synergistic etching. The pulse current provides a high-efficiency electrolytic etching speed. However, due to the unevenness of the electric field distribution, some copper layers or copper particles may remain unetched during the etching process. These residual copper layers or copper particles form an "island" system. In this regard, the present invention provides an electrolytic etching solution system containing high concentrations of iron ions and copper ions, thereby having a strong chemical etching ability, and can quickly assist in chemically etching the copper layers or copper particles remaining after electrolytic etching, effectively dealing with the unevenness that may occur during the electrolytic etching process, and helping to form fine circuits by copper etching of the circuit board. Therefore, through the synergy of chemical etching, the uniformity and efficiency of etching are further improved.

[0029] (3) The present invention discloses a method for preparing fine circuits of PCB by high-efficiency pulse electrolytic chemical synergistic etching, which adopts unidirectional pulse waveform electrolytic etching, and is matched with an electrolytic etching solution composed of copper ions, iron ions, hydrochloric acid and water, without using a corrosion inhibitor, and can use 5A / dm 2 ~500A / dm 2 The high pulse peak current density is used for electrolytic etching to prepare PCB fine circuits, which has the advantages of high efficiency and high quality. For the preparation of fine circuits with a line width and line spacing of 50μm, the etching factor can reach about 7.77 and the etching time is 120s. Therefore, the method of etching to prepare PCB fine circuits in this application has a very broad application prospect.

[0030] (4) The present invention provides a method for preparing fine circuits of PCB by efficient pulse electrochemical synergistic etching. In the electrolytic etching of pulse current, by limiting the duty cycle of the forward pulse current to 0.1 to 0.95, it not only helps to improve the current efficiency, but also promotes the rapid exchange of cupric ions or cuprous ions during the off time, thereby timely updating the electrolytic etching solution between circuits and enhancing the efficiency of circuit etching. In addition, the duty cycle can also provide a certain amount of time to timely exchange and process the large amount of electrolytic etching products generated instantly between the circuits, preventing them from hindering the etching process and improving the circuit etching factor.

[0031] (5) The method of the present invention for preparing fine circuits of PCB by efficient pulse electrolytic chemical synergistic etching does not require additional complex processing steps or special electrolytic etching equipment, nor does it require the use of corrosion inhibitors. It can simplify the production process and reduce the preparation cost. At the same time, it improves the etching speed, etching uniformity, production efficiency and simplicity of preparation, providing an efficient and economical solution for the preparation of fine circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1 It is a waveform diagram of the unidirectional pulse current of Example 1 of the present invention.

[0034] Figure 2 Schematic diagram of the waveform of the bidirectional pulse current of comparative example 2.

[0035] Figure 3 These are metallographic microscope observation images of samples with line widths and line spacings of 200μm, 150μm, 100μm, and 70μm etched by unidirectional pulse current.

[0036] Figure 4 These are metallographic microscope observation images of samples of Example 1 with line widths and line spacings of 200 μm, 150 μm, 100 μm, and 70 μm etched with an electrolyte free of iron ions.

[0037] Figure 5 These are metallographic microscope observation images of samples with bidirectional pulse current etching line widths and line spacings of 200μm, 150μm, 100μm, and 70μm.

[0038] Figure 6 These are metallographic microscope observation images of samples with an etching line width and line spacing of 200 μm when the unidirectional pulse current has different duty ratios in Examples 2 to 4.

[0039] Figure 7 These are metallographic microscope observation images of samples with an etching line width and line spacing of 150 μm when the unidirectional pulse current has different duty ratios in Examples 2 to 4.

[0040] Figure 8 These are metallographic microscope observation images of samples with an etching line width and line spacing of 100 μm when the unidirectional pulse current has different duty ratios in Examples 2 to 4.

[0041] Fig. 9 These are metallographic microscope observation images of samples with etched line width and line spacing of 70 μm at different duty ratios of unidirectional pulse current in Examples 2 to 4.

[0042] Fig.10 These are metallographic microscope observation images of samples with etched line width and line spacing of 50 μm at different duty ratios of unidirectional pulse current in Examples 2 to 4.

[0043] Fig.11 These are metallographic microscope observation pictures of samples with a line width and line spacing of 200 μm densely etched with different pulse currents in Example 3, Example 5 and Example 6 respectively.

[0044] Fig.12 These are metallographic microscope observation pictures of samples with a line width and line spacing of 150 μm densely etched with different pulse currents in Example 3, Example 5 and Example 6 respectively.

[0045] Fig.13 These are metallographic microscope observation pictures of samples with a line width and line spacing of 100 μm densely etched with different pulse currents in Example 3, Example 5 and Example 6 respectively.

[0046] Fig.14 These are metallographic microscope observation pictures of samples with a line width and line spacing of 70 μm densely etched with different pulse currents in Example 3, Example 5 and Example 6 respectively.

[0047] Fig.15 These are metallographic microscope observation pictures of samples with a line width and line spacing of 50 μm densely etched with different pulse currents in Example 3, Example 5 and Example 6 respectively.

[0048] Fig.16 Metallographic microscope observation images of samples with a line width and line spacing of 200 μm etched at different pulse current working times in Example 3, Example 7 and Example 8 respectively.

[0049] Fig.17 These are metallographic microscope observation pictures of samples with a line width and line spacing of 150 μm etched at different pulse current working times in Example 3, Example 7 and Example 8 respectively.

[0050] Fig.18 These are metallographic microscope observation pictures of samples with a line width and line spacing of 100 μm etched at different pulse current working times in Example 3, Example 7 and Example 8 respectively.

[0051] Fig.19 These are metallographic microscope observation pictures of samples with a line width and line spacing of 70 μm etched at different pulse current working times in Example 3, Example 7 and Example 8, respectively.

[0052] Fig. 20 These are metallographic microscope observation pictures of samples with a line width and line spacing of 50 μm etched at different pulse current working times in Example 3, Example 7 and Example 8, respectively. DETAILED DESCRIPTION

[0053] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] The terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. In the present invention, the singular forms "a", "said" and "the" used in the embodiments and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0055] In an embodiment of the present invention, a method for preparing fine circuits of a PCB by efficient pulse electrolytic chemical coordinated etching is provided, wherein an electrolytic etching solution is prepared by using copper ions, iron ions, hydrochloric acid and water, a circuit board to be etched is used as an anode, a titanium plate or a stainless steel plate is used as a cathode, and a high pulse peak current density is generated by a unidirectional pulse current to etch the circuit board to be etched to prepare fine circuits of the PCB;

[0056] The unidirectional pulse current is a forward pulse current, and the forward pulse current density is 5A / dm 2 ~500A / dm 2 The duty cycle of the forward pulse current is 0.1 to 0.95, and the duration of each forward pulse stage is 10 ms to 1000 ms.

[0057] The circuit board to be etched is a circuit pattern board whose surface is protected by a dry film.

[0058] In the embodiment, a method for preparing fine circuits of PCB by high-efficiency pulse electrochemical synergistic etching is provided. By using a unidirectional pulse current to generate a high pulse peak current density, the use of a reverse pulse current is avoided, and current control is also simplified. In addition, the high pulse peak current density is synergistically acted with a limited duty cycle. 2 ~500A / dm 2 ), the electrolytic etching rate is fast, and a large amount of copper layers can be quickly peeled off, while the copper layer protected by the dry film will not be etched due to the considerable electrochemical resistance, so under this electric field selectivity condition, the electric field only etches the copper layer not protected by the dry film, and the copper layer protected by the dry film is left, gradually forming a circuit. In addition, since chemical etching is non-selective and easily causes side corrosion to the circuit, the present invention can accelerate the electrolytic etching speed by using a high pulse peak current density, and can greatly shorten the electrolytic etching time, relatively weaken the corrosion effect of chemical etching on the circuit, and the circuit side corrosion is small. Since the electrolytic etching speed is fast, the electrolytic etching time is short, and electrolytic etching is used as the leading factor and chemical etching is used as a supplement, therefore, there is no need to use a corrosion inhibitor in the electrolytic etching solution, and therefore, the method for preparing PCB fine circuits by etching of the present invention can improve production efficiency and reduce preparation costs on the one hand, and can manufacture PCB fine circuits efficiently, with high quality and quickly on the other hand, while improving the quality and reliability of fine circuits.

[0059] In the embodiment, a method for preparing fine circuits of PCB by high-efficiency pulse electrolytic chemical synergistic etching is provided, wherein unidirectional pulse waveform electrolytic etching is combined with an electrolytic etching solution prepared by copper ions, iron ions, hydrochloric acid and water, and 5A / dm can be used without using a corrosion inhibitor. 2 ~500A / dm 2 The high pulse peak current density is used for electrolytic etching to prepare PCB fine circuits, which has the advantages of high efficiency and high quality. For the preparation of fine circuits with a line width and line spacing of 50μm, the etching factor can reach about 7.77. Therefore, the method of etching to prepare PCB fine circuits in this application has a very broad application prospect.

[0060] In the embodiment, a pulse current is used to provide an efficient electrolytic etching speed. However, due to the unevenness of the electric field distribution, some copper layers or copper particles may not be etched during the etching process. These residual copper layers or copper particles form an "island" system. In this regard, the electrolytic etching solution system provided by the present invention contains high concentrations of iron ions and copper ions, and thus has a strong chemical etching ability, and can quickly assist in chemically etching the copper layer or copper particles remaining after electrolytic etching, effectively dealing with the unevenness that may occur during the electrolytic etching process, and helping to form fine circuits by copper etching of the circuit board. Therefore, through the synergy of chemical etching, the uniformity and efficiency of etching are further improved.

[0061] In some embodiments, in the electrolytic etching solution, the concentration of the copper ions is 5 g / L to 100 g / L.

[0062] In some embodiments, in the electrolytic etching solution, the concentration of the iron ions is 5 g / L to 100 g / L.

[0063] The concentration of copper ions and the concentration of iron ions defined in the present invention can effectively handle the non-uniformity that may occur during the electrolytic etching process, and contribute to the copper etching of the circuit board to form fine circuits. Therefore, through the synergy of chemical etching, the uniformity and efficiency of etching are further improved. In addition, through the synergy of iron ions and copper ions, the high pulse peak current density can be further improved, which is further conducive to the improvement of the electrolytic etching speed.

[0064] In some embodiments, the concentration of hydrochloric acid in the electrolytic etching solution is 0.2 mol / L to 2 mol / L. The concentration of hydrochloric acid can make the electrolytic etching solution have sufficient hydrogen ions and thus have good conductivity.

[0065] In some embodiments, the copper ion is at least one of anhydrous copper chloride, dihydrated copper chloride or copper sulfate; wherein anhydrous copper chloride, dihydrated copper chloride or copper sulfate can dissolve copper ions well, and anhydrous copper chloride, dihydrated copper chloride and copper sulfate have the characteristics of easy availability of raw materials and low cost. And / or

[0066] The iron ion is at least one of ferric chloride, ferric oxide, and ferric sulfate. Among them, ferric chloride can dissolve iron ions well, and ferric oxide can generate iron ions under the action of hydrochloric acid. Moreover, ferric chloride and ferric oxide have the characteristics of easy availability of raw materials and low cost.

[0067] In some embodiments, during the etching process, the temperature of the electrolytic etching solution is 15° C. to 65° C. This temperature can increase the ion mass transfer rate in the electrolytic etching solution, accelerate the ion exchange between circuits, and thus accelerate the etching speed, shortening the time for preparing fine PCB circuits.

[0068] In some embodiments, preferably, the duty cycle of the forward pulse current is 0.2-0.8. In the present invention, in the electrolytic etching of the pulse current, the appropriate duty cycle not only helps to improve the current efficiency, but also promotes the rapid exchange of cupric ions or cuprous ions during the off time, thereby timely updating the electrolytic etching solution between the circuits, thereby enhancing the efficiency of circuit etching. In addition, the duty cycle can also provide a certain amount of time to timely exchange and process the large amount of electrolytic etching products generated instantly between the circuits, prevent them from hindering the etching process, and improve the circuit etching factor.

[0069] In some embodiments, preferably, the duration of each forward pulse phase is 40 ms to 500 ms.

[0070] In some embodiments, the time for etching the circuit board to be etched to prepare the PCB fine circuit is 85s to 200s. Since the present application uses a unidirectional pulse current to generate a high pulse peak current density for electrolytic etching, and simultaneously cooperates with the electrolytic etching solution for chemical etching, it has the advantages of fast etching speed and short circuit preparation time.

[0071] In some embodiments, during the etching process for preparing fine circuits on a PCB, the electrolytic etching solution is stirred.

[0072] The uniformity of the distribution of the electrolytic etching solution can be improved by stirring, and the stirring method includes at least one of mechanical stirring, spray stirring, air flow stirring, circulating pumping, magnetic stirring, and ultrasonic stirring. The flow rate of air flow stirring is set to 2L / min to 10L / min. Since a large amount of etching products will be generated during the electrolytic etching process, these etching products can be removed in time by stirring to avoid hindering the etching process and affecting the etching factor.

[0073] The following describes the invention in conjunction with specific embodiments.

[0074] Example 1

[0075] A method for preparing fine circuits of PCB by efficient pulse electrolytic chemical synergistic etching, wherein an electrolytic etching solution is prepared by using anhydrous cupric chloride, ferric chloride, hydrochloric acid and water, a circuit board to be etched is used as an anode, a stainless steel plate is used as a cathode, and a high pulse peak current density is generated by a unidirectional pulse current to etch the circuit board to be etched to prepare fine circuits of PCB. In this embodiment, the temperature of the electrolytic etching solution is 25°C, and the time for etching the circuit board to be etched to prepare fine circuits of PCB is 85s.

[0076] In this embodiment, the unidirectional pulse current is a forward pulse current, wherein the waveform diagram of the forward pulse current in this embodiment is as follows: Figure 1 In this embodiment, the forward pulse current density is 10A / dm 2 , the duty cycle of the forward pulse current is 0.95, and the time of each forward pulse stage is 42ms.

[0077] In this embodiment, in the electrolytic etching solution, the concentration of copper ions is 30 g / L, the concentration of iron ions is 30 g / L, and the concentration of hydrochloric acid is 0.8 mol / L.

[0078] In this embodiment, during the process of etching and preparing fine circuits of PCB, air flow stirring operation is also used to enhance convection. In this embodiment, the flow rate is 6L / min.

[0079] Example 2

[0080] A method for preparing fine circuits of PCB by efficient pulse electrolytic chemical synergistic etching, wherein copper sulfate, ferric chloride, hydrochloric acid and water are used to prepare an electrolytic etching solution, a circuit board to be etched is used as an anode, a stainless steel plate is used as a cathode, a high pulse peak current density is generated by a unidirectional pulse current, and the circuit board to be etched is etched to prepare fine circuits of PCB. In this embodiment, the temperature of the electrolytic etching solution is 25°C, and the time for etching the circuit board to be etched to prepare fine circuits of PCB is 120s.

[0081] In this embodiment, the unidirectional pulse current is a forward pulse current, wherein the waveform diagram of the forward pulse current in this embodiment is as follows: Figure 1 In this embodiment, the forward pulse current density is 10A / dm 2 , the duty cycle of the forward pulse current is 0.8, and the time of each forward pulse stage is 40ms.

[0082] In this embodiment, in the electrolytic etching solution, the concentration of copper ions is 25 g / L, the concentration of iron ions is 43 g / L, and the concentration of hydrochloric acid is 1.2 mol / L.

[0083] In this embodiment, during the process of etching and preparing fine circuits of PCB, air flow stirring operation is also used to enhance convection. In this embodiment, the flow rate is 6L / min.

[0084] Example 3

[0085] A method for preparing fine circuits of PCB by efficient pulse electrolytic chemical synergistic etching, wherein copper sulfate, ferric chloride, hydrochloric acid and water are used to prepare an electrolytic etching solution, a circuit board to be etched is used as an anode, a stainless steel plate is used as a cathode, a high pulse peak current density is generated by a unidirectional pulse current, and the circuit board to be etched is etched to prepare fine circuits of PCB. In this embodiment, the temperature of the electrolytic etching solution is 25°C, and the time for etching the circuit board to be etched to prepare fine circuits of PCB is 120s.

[0086] In this embodiment, the unidirectional pulse current is a forward pulse current, wherein the waveform diagram of the forward pulse current in this embodiment is as follows: Figure 1 In this embodiment, the forward pulse current density is 10A / dm 2 , the duty cycle of the forward pulse current is 0.5, and the duration of each forward pulse stage is 40ms.

[0087] In this embodiment, in the electrolytic etching solution, the concentration of copper ions is 25 g / L, the concentration of iron ions is 43 g / L, and the concentration of hydrochloric acid is 1.2 mol / L.

[0088] In this embodiment, during the process of etching and preparing fine circuits of PCB, air flow stirring operation is also used to enhance convection. In this embodiment, the flow rate is 6L / min.

[0089] Example 4

[0090] A method for preparing fine circuits of PCB by efficient pulse electrolytic chemical synergistic etching, wherein copper sulfate, ferric chloride, hydrochloric acid and water are used to prepare an electrolytic etching solution, a circuit board to be etched is used as an anode, a stainless steel plate is used as a cathode, a high pulse peak current density is generated by a unidirectional pulse current, and the circuit board to be etched is etched to prepare fine circuits of PCB. In this embodiment, the temperature of the electrolytic etching solution is 25°C, and the time for etching the circuit board to be etched to prepare fine circuits of PCB is 200s.

[0091] In this embodiment, the unidirectional pulse current is a forward pulse current, wherein the waveform diagram of the forward pulse current in this embodiment is as follows: Figure 1 In this embodiment, the forward pulse current density is 10A / dm2 , the duty cycle of the forward pulse current is 0.2, and the duration of each forward pulse stage is 40ms.

[0092] In this embodiment, in the electrolytic etching solution, the concentration of copper ions is 25 g / L, the concentration of iron ions is 43 g / L, and the concentration of hydrochloric acid is 1.2 mol / L.

[0093] In this embodiment, during the process of etching and preparing fine circuits of PCB, air flow stirring operation is also used to enhance convection. In this embodiment, the flow rate is 6L / min.

[0094] Example 5

[0095] A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching. The difference between this embodiment and embodiment 3 is that the forward pulse current density is 5A / dm 2 , the remaining conditions and parameters are the same as those in Example 3.

[0096] Example 6

[0097] A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching. The difference between this embodiment and embodiment 3 is that the forward pulse current density is 15A / dm 2 , the remaining conditions and parameters are the same as those in Example 3.

[0098] Example 7

[0099] A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching. The difference between this embodiment and embodiment 3 is that the time of each positive pulse stage is 100ms, and the other conditions and parameters are the same as those in embodiment 3.

[0100] Example 8

[0101] A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching. The difference between this embodiment and embodiment 3 is that the time of each positive pulse stage is 500ms, and the other conditions and parameters are the same as those in embodiment 3.

[0102] Example 9

[0103] A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching. The difference between this embodiment and embodiment 1 is that a titanium plate is used as a cathode, the temperature of the electrolytic etching solution is 45°C, and the forward pulse current density is 20A / dm 2The duty cycle of the forward pulse current is 0.95, and the duration of each forward pulse stage is 20ms. In the electrolytic etching solution, the concentration of copper ions is 35g / L, the concentration of iron ions is 53g / L, and the concentration of hydrochloric acid is 0.24mol / L. The flow rate of air flow stirring is 5L / min.

[0104] Example 10

[0105] A method for preparing fine circuits of PCB by efficient pulse electrolytic chemical coordinated etching, the difference between this embodiment and embodiment 1 is that the temperature of the electrolytic etching solution is 35°C, the time of each positive pulse stage is 1000ms; in the electrolytic etching solution, the concentration of copper ions is 45g / L, the concentration of iron ions is 30g / L, and the concentration of hydrochloric acid is 0.7mol / L. The flow rate of air flow stirring is 7L / min.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that the electrolytic etching solution used in this comparative example does not contain iron ions. In this example, the concentration of copper ions in the electrolytic etching solution is 30 g / L, and the concentration of hydrochloric acid is 0.8 mol / L.

[0108] The electrolyte of this comparative example does not contain iron ions, and the other conditions and parameters are the same as those of Example 1.

[0109] Comparative Example 2

[0110] The difference between this comparative example and Example 1 is that this comparative example adopts a bidirectional pulse current, wherein the forward pulse current density is 10A / dm 2 , reverse pulse current density is -10A / dm 2 The duty cycle of the forward pulse current is 0.95, the time of each forward pulse stage is 40ms, the time of each reverse pulse stage is 2ms, and the time for etching the circuit board to be etched to prepare the PCB fine circuit is 125s.

[0111] This comparative example has no duty cycle, and the other conditions and parameters are the same as those in Example 1.

[0112] Among them, the waveform diagram of the bidirectional pulse current of this comparative example is as follows: Figure 2 shown.

[0113] Experimental testing

[0114] (I) Effect of electrolyte formula on etching factor

[0115] The methods for preparing fine PCB circuits of Example 1 and Comparative Example 1 were respectively used to etch circuit boards with different line widths and line spacings, including four samples with the same line width and line spacing, namely: 200μm, 150μm, 100μm, and 70μm. Each value of each sample was measured three times and the average value was taken. The effects of unidirectional pulse current and bidirectional pulse current on the etching factor were respectively detected.

[0116] Combination Figure 3 and Figure 4 By comparing the circuit board samples etched with and without iron ion electrolytes, it can be found that the insufficient chemical etching ability of the electrolyte will lead to a large difference in the upper and lower widths of the circuit board, which is not conducive to the precise formation of the circuit. By adding iron ions to the electrolyte, its chemical etching effect can be enhanced, assisting the etching process, thereby reducing the width difference of the circuit, which is conducive to the formation of precise circuits and improving etching efficiency.

[0117] (II) Effect of pulse current on etching factor

[0118] The methods for preparing fine PCB circuits of Example 1 and Comparative Example 2 were respectively used to etch circuit boards with different line widths and line spacings, including four samples with the same line width and line spacing, namely: 200 μm, 150 μm, 100 μm, and 70 μm. Each value of each sample was measured three times and the average value was taken. The effects of unidirectional pulse current and bidirectional pulse current on the etching factor were respectively detected.

[0119] Combination Figure 3 and Figure 5 By comparing the circuit board samples etched by unidirectional pulse and positive and negative bidirectional pulse, it can be found that the lower line width of the unidirectional pulse electrolytic etching is shorter, and the difference between the upper and lower line widths is small, while the lower line width of the positive and negative bidirectional pulse electrolytic etching is relatively longer, and the difference between the upper and lower line widths is large, which is not conducive to line forming. The main reason is that the reverse current stage of the positive and negative bidirectional pulse will deposit some copper on the line, resulting in low efficiency of electrolytic etching circuit preparation, long etching time, and unnecessary resource and energy consumption.

[0120] (III) Effect of different duty ratios of unidirectional pulse current on etching factor

[0121] The methods for preparing PCB fine circuits of Examples 2 to 4 were respectively used to etch circuit boards with different line widths and line spacings, including five samples with the same line width and line spacing, namely: 200μm, 150μm, 100μm, 70μm, and 50μm. Each value of each sample was measured six times and the average value was taken. The effects of different duty ratios of unidirectional pulse current on the etching factor were respectively detected, and the specific test results are as follows.

[0122] Table 1 Test results of 200μm line width and line spacing samples with different duty ratios of unidirectional pulse current

[0123]

[0124] in, Figure 5 In the middle circuit diagram, the unevenness of the upper part of the circuit is caused by the deformation of the dry film during grinding and slicing, which covers the copper circuit.

[0125] Table 2 Test results of 150μm line width and line spacing samples etched with different duty ratios of unidirectional pulse current

[0126]

[0127]

[0128] Table 3 Test results of 100μm line width and line spacing samples with different duty ratios of unidirectional pulse current

[0129]

[0130] Table 4 Test results of 70μm line width and line spacing samples etched with different duty ratios of unidirectional pulse current

[0131]

[0132] Table 5 Test results of 50μm line width and line spacing samples etched with different duty ratios of unidirectional pulse current

[0133]

[0134]

[0135] From the test data results in Tables 1 to 5, we can see that Figures 6 to 10 In unidirectional pulse electrolytic etching, the adjustment of the duty cycle has a significant impact on the etching effect. When the duty cycle decreases, the difference in the upper and lower line widths of the circuit decreases, and the etching is more uniform. This is because during the period when the current is turned off, the timely replenishment and exchange of the circuit surface with the electrolyte helps to remove the etching products. However, a duty cycle that is too low will lead to a decrease in the average current density, a slow etching speed, and an increase in chemical corrosion, thereby increasing the side corrosion of the circuit. Therefore, choosing a suitable duty cycle is crucial to optimizing the electrolytic etching process.

[0136] (IV) Effect of different pulse current densities of unidirectional pulse current on electrolytic etching

[0137] The methods for preparing PCB fine circuits of Example 3, Example 5 and Example 6 were respectively used to etch circuit boards with different line widths and line spacings, including five samples with the same line width and line spacing, namely: 200μm, 150μm, 100μm, 70μm, and 50μm. Each value of each sample was measured six times and the average value was taken. The effects of different pulse current densities of unidirectional pulse current on electrolytic etching were detected respectively, and the specific test results are as follows.

[0138] Table 6 Test results of samples with different pulse current densities and line width and line spacing of 200 μm

[0139]

[0140] Table 7 Test results of samples with different pulse current densities and line width and line spacing of 150 μm

[0141]

[0142]

[0143] Table 8 Test results of samples with different pulse current densities and line width and line spacing of 100 μm

[0144]

[0145] Table 9 Test results of samples with different pulse current densities and line widths of 70 μm

[0146]

[0147] Table 10 Test results of samples with different pulse current densities and line widths of 50 μm

[0148]

[0149]

[0150] From the test data results in Tables 6 to 10, we can see that Figures 11 to 15 When the pulse current density is too large, if the convection intensity cannot meet the requirements for timely removal of etching products between circuits, it will hinder etching and cause incomplete circuit etching. When the pulse current density is too small, it will also lead to reduced etching efficiency, relatively enhance chemical corrosion, and cause more side corrosion of the circuits.

[0151] (V) Effect of unidirectional pulse current and different pulse current working time on electrolytic etching

[0152] The methods for preparing PCB fine circuits of Example 3, Example 7 and Example 8 were respectively used to etch circuit boards with different line widths and line spacings, including five samples with the same line width and line spacing, namely: 200μm, 150μm, 100μm, 70μm, and 50μm. Each value of each sample was measured six times and the average value was taken. The effects of different pulse current working times of unidirectional pulse current on electrolytic etching were respectively detected, and the specific test results are as follows.

[0153] Table 11 Test results of samples with different pulse current working time and etching line width and line spacing of 200μm

[0154]

[0155] Table 12 Test results of samples with different pulse current working time and etched line width and line spacing of 150μm

[0156]

[0157]

[0158] Table 13 Test results of samples with different pulse current working time and etching line width and line spacing of 100μm

[0159]

[0160] Table 14 Test results of samples with different pulse current working time and etched line width and line spacing of 70μm

[0161]

[0162] Table 15 Test results of samples with different pulse current working time and etching line width and line spacing of 50μm

[0163]

[0164] From the test data results in Tables 11 to 15, it can be seen that Figures 16 to 20 Under the same duty cycle, the longer the pulse working time, the less complete the etching. This is mainly because the shutdown time is insufficient to meet the timely processing of the etching products between the lines, which hinders the etching process. Even if the etching factor becomes higher, it will cause the lower line to become wider and wider, which is not conducive to line formation.

[0165] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching, characterized in that: An electrolytic etching solution is prepared by using copper ions, iron ions, hydrochloric acid and water, the circuit board to be etched is used as the anode, and the titanium plate or the stainless steel plate is used as the cathode. A high pulse peak current density is generated by a unidirectional pulse current to etch the circuit board to be etched to prepare a PCB fine circuit; The unidirectional pulse current is a forward pulse current, and the forward pulse current density is 5A / dm 2 ~500A / dm 2 The duty cycle of the forward pulse current is 0.1 to 0.95, and the duration of each forward pulse stage is 10 ms to 1000 ms.

2. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: In the electrolytic etching solution, the concentration of the copper ions is 5 g / L to 100 g / L.

3. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: In the electrolytic etching solution, the concentration of the iron ions is 5 g / L to 100 g / L.

4. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: In the electrolytic etching solution, the concentration of the hydrochloric acid is 0.2 mol / L to 2 mol / L.

5. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: The copper ion is at least one of anhydrous copper chloride, copper chloride dihydrate or copper sulfate; and / or The iron ion is at least one of ferric chloride, ferric oxide and ferric sulfate.

6. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: During the etching process, the temperature of the electrolytic etching solution is 15°C to 65°C.

7. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: The duty cycle of the forward pulse current is 0.2-0.

8.

8. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: The duration of each positive pulse phase is 40ms to 500ms.

9. The method for preparing PCB fine circuits by efficient pulse electrolytic chemical coordinated etching as claimed in claim 1, characterized in that: The time for etching the circuit board to be etched to prepare the PCB fine circuit is 85s to 200s.

10. The method for preparing PCB fine circuits by high-efficiency pulse electrolytic chemical coordinated etching according to claim 1, characterized in that: During the etching process for preparing fine circuits on the PCB, the electrolytic etching solution is stirred.

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