Method for removing wet film in selective process of printed circuit board and printed circuit board

Abstract

The invention relates to the field of printed circuit board manufacturing, and particularly discloses a method for removing a wet film in a selective process of a printed circuit board and the printed circuit board. The method comprises the following steps: S1, providing a printed circuit board with a wet film formed on the surface; s2, a primary bulking process; s3, a pressurized ultrasonic spraying and bulking process; s4, a preliminary film stripping process; s5, a first pressurized spraying film stripping process; s7, a multi-section type pressure difference pressurization spraying washing process; wherein a film stripping agent solution with the mass concentration of 10-20 kg / m < 3 > is adopted in the step S2, the step S3, the step S4 and the step S5; the film removing agent comprises the following components in percentage by mass: 15-55% of compound alkali, 1-10% of a polyether surfactant and the balance of water. The wet film on the surface of the printed current board can be rapidly and thoroughly removed, meanwhile, the oxidation blackening phenomenon cannot occur on the copper surface after film removal, the product quality is improved, factory benefits are improved, and the method has excellent application prospects.

Description

Technical Field

[0001] The present application relates to the field of manufacturing printed circuit boards, and more specifically, to a method for removing a dehumidifying film in a printed circuit board selection process and a printed circuit board. Background Art

[0002] Printed circuit boards (PCBs) are one of the important components of the electronics industry. Almost every electronic device uses printed circuit boards. It can replace complex wiring to achieve electrical connections between components in the circuit. It not only simplifies the assembly and welding of electronic products, reduces the wiring workload under traditional methods, and reduces the labor intensity of workers, but also reduces the size of the whole machine, reduces the cost of products, and improves the quality and reliability of electronic equipment. Among them, high-density interconnect boards (HDI), as a type of printed circuit board, have higher line density and finer line spacing per unit area. They are usually used to connect various components in tiny packages, such as high-speed chips, multi-pin count and fine-pitch components. At present, the selective plating process of high-density interconnect boards usually includes substrate pre-treatment (brushing), wet film application, exposure, development, de-washing, gold plating, and film stripping. The presence of wet film can be used as an anti-plating layer to protect the circuit pattern that does not need to be gold-plated during the gold plating process. After the gold plating is completed and the required circuit pattern is obtained, the film stripping operation can be performed.

[0003] The existing film stripping process usually uses a sodium hydroxide solution with a mass concentration of 3% as the film stripping liquid, and the film stripping process is completed through a swelling process, two film stripping processes, two water washing processes and drying. However, the film stripping process can only effectively remove the dry film, and the removal efficiency is low for the wet film that is more completely filled in the fine line gap, and there is a problem of unclean film stripping. Especially for circuit boards with thick copper and fine line patterns, it is more likely to cause incomplete film stripping and residues in the fine line spacing gaps, which seriously affects the subsequent process. In addition, the film stripping liquid will also attack the copper surface, causing large-scale oxidation and blackening of the copper surface, affecting product quality. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a method for removing a dehumidifying film in a printed circuit board selection process and a printed circuit board manufactured according to the method.

[0005] In a first aspect, the present application provides a method for removing a dehumidifying film in a printed circuit board selection process, which adopts the following technical solution: A method for removing a dehumidifying film in a printed circuit board selection process comprises the following steps: S1. providing a printed circuit board having a wet film formed on the surface; S2, a preliminary swelling process, which is to perform preliminary swelling on the wet film on the printed circuit board in S1; S3, pressurized ultrasonic spray bulking process, at a pressure of ≥ 2kg / m 2 , under the condition of ultrasonic frequency ≥ 20KHz, the wet film on the printed circuit board in S2 is deeply expanded; S4, a preliminary film stripping process, which is to initially strip the wet film on the printed circuit board in S3; S5, the first pressurized spray film removal process, at a pressure of ≥ 2kg / m 2 Under the condition of , the wet film on the printed circuit board in S4 is deeply stripped; S7, a multi-stage pressure difference pressurized spray washing process, in which the printed circuit board is washed with water under the condition that the pressure is first increased and then decreased, until the wet film residue within the line width and line spacing of the metal line is removed within 50μm and there is no excessive reaction on the surface of the metal line; Among them, the mass concentration of S2, S3, S4 and S5 is 10-20kg / m 3 The stripping agent solution comprises, by mass percentage, 15-55% of a composite alkali, 1-10% of a polyether surfactant, and the remainder of water.

[0006] By adopting the above-mentioned technical scheme, the present application provides a method for efficiently removing wet film in the process of selecting printed circuit boards. This method effectively improves the bulkiness of the wet film through the preliminary bulking process and the pressurized ultrasonic spray bulking process, making the subsequent film stripping process more thorough. Specifically, under the action of high pressure and high-frequency ultrasound, the pressurized ultrasonic spray bulking process can make the film stripping agent penetrate into the wet film, making it fully expanded, making it easier to remove. The preliminary film stripping process and the first pressurized spray film stripping process further ensure the complete removal of the wet film, especially under high pressure conditions, and can effectively remove the residual wet film. Finally, the multi-stage pressure difference pressurized spray water washing process not only removes the remaining wet film residue, but also ensures that the surface of the metal circuit is clean and bright, meeting high-quality processing standards.

[0007] In addition, the stripping agent used in the preliminary bulking process, the pressurized ultrasonic spray bulking process, the preliminary stripping process and the first pressurized spray stripping process of the present application is a composite alkali as the main component, which is used to destroy the chain structure in the wet film and make the wet film fall off, thereby achieving the effect of stripping. At the same time, a polyether surfactant is used to dissolve the polymer segments in the wet film molecules to control the size of the film fragments, and the foam generated by the polyether surfactant can increase the contact area between the stripping agent and the wet film and foam the wet film, so that the molecular gap of the wet film is larger, and the contact area between the wet film layer and the selective stripping liquid is further increased, thereby improving the solubility.

[0008] In addition, since the film stripping method of the present application can effectively remove the wet film in S2, S3, S4 and S5, the possibility of film residues being carried to the later stage and contaminating the spray washing process due to poor film stripping effect is reduced, thereby reducing maintenance costs.

[0009] In summary, compared with the existing film stripping methods, the film stripping method of the present application can more easily and thoroughly remove the wet film on the printed circuit board, especially can effectively remove the wet film within the fine line spacing on the printed circuit board, which not only ensures the product quality, but also improves the film stripping speed. And compared with the conventional sodium hydroxide film stripping solution, the film stripping agent of the present application not only has a stronger film stripping effect, but also can effectively inhibit metal corrosion, improve the problem of large-area oxidation and blackening of the copper surface after film stripping, improve product quality, reduce the scrap rate of printed circuit boards, reduce production costs, and improve the factory efficiency of printed circuit boards.

[0010] Preferably, the stripping agent comprises, by mass percentage, 35% of a composite alkali, 10% of a polyether surfactant, and 55% of water.

[0011] Through the above-mentioned technical scheme, the present application further optimizes the ratio of each component in the stripping agent, and gives full play to the synergistic effect between the various components, so that the stripping agent has both a strong degree of alkalinity and the ability to penetrate the wet film, and can fully penetrate and dissolve the wet film, thereby improving the stripping effect of the stripping agent on the wet film, and ensuring the fluidity of the stripping agent, while reducing the possibility of metal corrosion due to the excessively high alkalinity of the stripping agent.

[0012] Preferably, the initial expansion in S2 is at a pressure of ≥2 kg / m 2 , and the ultrasonic frequency is ≥20KHz.

[0013] Through the above technical scheme, the present application further enables the preliminary swelling process to be carried out within a certain pressure range and ultrasonic frequency range, which can further increase the expansion degree of the wet film, making the subsequent deep swelling and film removal processes more thorough, and further reducing the possibility of wet film residue.

[0014] Preferably, in S2 and S3, the pressure range is 2-4 kg / m 2 , the ultrasonic frequency range is 20-40KHz.

[0015] Through the above technical solution, the present application further optimizes the pressure range and ultrasonic frequency range, so that the wet film can be fully expanded under high pressure and high frequency conditions, thereby reducing the adhesion between the wet film and the printed circuit board, making the wet film easier to be removed by subsequent processes, and improving the film removal efficiency and film removal effect. At the same time, this optimized combination of pressure and frequency parameters can also reduce the possibility of damage to the substrate due to excessive pressure or high frequency, ensuring the surface quality of the printed circuit board and the integrity of the metal wires.

[0016] Preferably, the initial removal of the wet film in S4 is performed at a pressure of ≥ 2 kg / m 2 under the conditions of.

[0017] Through the above technical solution, the present application further enables the initial film stripping process to be carried out under a certain pressure range, which can further destroy the wet film structure, making it easier to be removed by subsequent processes, reducing residues, and further improving the quality of the printed circuit board.

[0018] Preferably, the method further comprises: S6, a second pressurized spray film removal step, at a pressure of ≥ 2kg / m 2 Under the condition of , the wet film on the printed circuit board in step S5 is deeply stripped.

[0019] Through the above technical scheme, the second pressurized spray film removal process set in the present application can further improve the removal efficiency of the wet film, ensure the complete removal of the wet film, reduce the possibility of short circuits between metal circuits caused by wet film residues, and at the same time ensure the surface finish and flatness of the metal circuits.

[0020] Preferably, in S4, S5 and S6, the pressure range is 2-4 kg / m 2 .

[0021] Through the above technical solution, the present application further optimizes the pressure range in the film stripping stage, which not only ensures sufficient film stripping force, but also reduces the possibility of damage to the metal circuit due to excessive pressure.

[0022] Preferably, S7 includes three stages of spray washing, and the pressure of each stage is set to 1.5-2.5 kg / m 2 10-12kg / m 2 and 1.5-2.5kg / m 2 .

[0023] By adopting the above technical solution, the present application adopts three stages of spray water washing with different pressures to effectively remove the wet film residue on the printed circuit board. Specifically, the pressure of the first stage is set to 1.5-2.5kg / m 2 , which can gently remove the surface wet film and reduce the possibility of damage to the metal circuit; the second stage pressure is set to 10-12kg / m2 , and it is a swing water washing, which can deeply clean the wet film in the fine line spacing to ensure that the wet film residue is completely removed; the third stage pressure is set to 1.5-2.5kg / m 2 , which can further rinse away the residue and ensure a smooth surface for the metal circuit.

[0024] In a second aspect, the present application provides a printed circuit board, which adopts the following technical solution: A printed circuit board is prepared by the above-mentioned method for removing moisture film, wherein the line width and line spacing of the metal lines of the printed circuit board are both below 75 μm, the line thickness of the metal lines of the printed circuit board is below 18 μm, and after the selection process is completed, there is no dot-shaped wet film residue between the metal lines and the surface of the metal lines is bright.

[0025] In summary, this application has the following beneficial technical effects: 1. The method for removing the wet film in this application can completely remove the wet film covering the surface of the printed circuit board. Even if the line width and line spacing of the metal line are within 50μm, the wet film residue can be removed, meeting the process requirements and ensuring the product quality. 2. The dehumidification film removal method of the present application has a high film removal speed, which ensures product quality while also having high production efficiency, significantly improving the factory's production capacity; 3. Compared with conventional sodium hydroxide film stripping solution, the film stripping agent used in the method for stripping the wet film of the present application can not only remove the wet film more completely, but also improve the problem of large-area oxidation and blackening on the copper surface after film stripping, further improve product quality, reduce the scrap rate of printed circuit boards, reduce production costs, and improve factory efficiency; 4. The method of removing the dehumidification film in the present application reduces the situation where the nozzle of the water washing section is blocked due to the film residue being brought into the water washing section, reduces the maintenance cost of the production line, simplifies the operation process of the production line, and facilitates production. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a process flow chart of the method for removing the dehumidification film in the printed circuit board selection process of this application. DETAILED DESCRIPTION

[0027] The present application is further described in detail below with reference to examples and comparative examples.

[0028] Unless otherwise specified, the raw materials used in this application are all commercially available products, including: Compound alkali is a white powder, the main component of which is Ca(OH) 2 , the active ingredient content is 93%; The polyether surfactant is a commonly used polyether surfactant in the art. In the specific implementation of the present application, propylene glycol block polyether L-64 is used as an example for illustration, and its CAS number is 9003-11-6.

[0029] In the specific implementation of the present application, the effective lengths of the preliminary bulking process and the pressurized ultrasonic spray bulking process of the film stripping equipment are both 2000mm, and the tank capacity is 700L; the effective lengths of the preliminary film stripping process, the first pressurized spray film stripping process, and the second pressurized spray film stripping process are both 20000mm, and the tank capacity is 700L; the effective lengths of the three-stage pressurized spray water washing processes in the multi-stage pressure difference pressurized spray water washing process are all 600mm, and the tank capacity is 100L; Ultrasonic vibrators are provided in the preliminary bulking process and the pressurized ultrasonic spray bulking process; The preliminary bulking process, the pressurized ultrasonic spray bulking process, the preliminary film stripping process, the first pressurized spray film stripping process, the second pressurized spray film stripping process and the multi-stage pressure difference pressurized spray water washing process are all provided with nozzles, and the nozzle shape is fan-shaped; Before the film stripping process begins, water and film stripping agent are added to the tanks corresponding to the initial bulking process, the pressurized ultrasonic spray bulking process, the initial film stripping process, the first pressurized spray film stripping process, and the second pressurized spray film stripping process, so that a mass concentration of 10-20kg / m 3 After the stripping starts, the printed circuit board goes through the above steps in sequence, the stripping solution is sprayed onto the surface of the printed circuit board by the nozzle, and the stripping solution after spraying flows back to the tank along the printed circuit board, so as to realize the recycling of the stripping solution; In the specific implementation of the present application, in order to highlight the effect of the stripping agent component, only 15 kg / m 3 The stripping agent solution is used as an example for explanation, and the other mass concentrations can be conventionally deduced based on the effects of the present application.

[0030] Preparation Example 1 The stripping agent is prepared by the following method: 350 g of composite alkali, 50 g of propylene glycol block polyether L-64 and 600 g of water were mixed evenly to obtain a film stripping agent.

[0031] Preparation Example 2 The stripping agent is prepared by the following method: 350 g of composite alkali, 10 g of propylene glycol block polyether L-64 and 640 g of water were uniformly mixed to obtain a film stripping agent.

[0032] Preparation Example 3 The stripping agent is prepared by the following method: Mix 350 g of composite alkali, 100 g of propylene glycol block polyether L-64 type and 550 g of water evenly to obtain a film stripper.

[0033] Preparation Example 4 The film stripper is prepared by the following method: Mix 150 g of composite alkali, 50 g of propylene glycol block polyether L-64 type and 800 g of water evenly to obtain a film stripper.

[0034] Preparation Example 5 The film stripper is prepared by the following method: Mix 550 g of composite alkali, 50 g of propylene glycol block polyether L-64 type and 400 g of water evenly to obtain a film stripper.

[0035] Example 1.1 A method for removing a wet film in a chemical conversion process of a printed circuit board, comprising the following steps: S1. Provide a printed circuit board with a wet film formed on its surface; S2. Preliminary swelling process, under the conditions of a pressure of 2 kg / m 2 and an ultrasonic frequency range of 20 kHz, use the film stripper solution prepared from the film stripper obtained in Preparation Example 1 to preliminarily swell the wet film on the printed circuit board in S1; S3. Pressurized ultrasonic spray swelling process, under the conditions of a pressure of 2 kg / m 2 and an ultrasonic frequency of 20 KHz, use the film stripper solution prepared from the film stripper obtained in Preparation Example 1 to deeply swell the wet film on the printed circuit board in S2; S4. Preliminary film stripping process, under the condition of a pressure of 2 kg / m 2 , use the film stripper solution prepared from the film stripper obtained in Preparation Example 1 to preliminarily remove the wet film on the printed circuit board in S3; S5. First pressurized spray film stripping process, under the condition of a pressure of 2 kg / m 2 , use the film stripper solution prepared from the film stripper obtained in Preparation Example 1 to deeply remove the wet film on the printed circuit board in S4; S6. Second pressurized spray film stripping process, under the condition of a pressure of 2 kg / m 2 , use the film stripper solution prepared from the film stripper obtained in Preparation Example 1 to deeply remove the wet film on the printed circuit board in S5; S7. Multi-stage pressure difference pressurized spray water washing process, pass the printed circuit board in S6 through pressurized water washing under a pressure of 1.5 kg / m 2 , swing high-pressure water washing under a pressure of 10 kg / m 2 and pressurized water washing under a pressure of 1.5 kg / m 2Pressurized water washing under pressure until the wet film residue within the line width and line spacing of the metal line within 50μm is removed and there is no excessive reaction on the surface of the metal line; S8. Use hot air to blow away the moisture on the surface of the printed circuit board, and obtain the printed circuit board after drying.

[0036] Example 1.2 A method for removing a dehumidifying film in a printed circuit board selection process comprises the following steps: S1. providing a printed circuit board having a wet film formed on the surface; S2, initial expansion process, at a pressure of 4kg / m 2 , under the condition of an ultrasonic frequency range of 40 kHz, using a stripping agent solution prepared by the stripping agent prepared in Preparation Example 1 to preliminarily expand the wet film on the printed circuit board in S1; S3, pressurized ultrasonic spray bulking process, at a pressure of 4kg / m 2 , under the condition of an ultrasonic frequency of 40 KHz, using a stripping agent solution prepared by the stripping agent prepared in Preparation Example 1 to deeply expand the wet film on the printed circuit board in S2; S4, initial film stripping process, at a pressure of 4kg / m 2 Under the conditions of , the stripper solution prepared by the stripper prepared in Preparation Example 1 is used to preliminarily strip the wet film on the printed circuit board in S3; S5, the first pressurized spray film removal process, at a pressure of 4kg / m 2 Under the conditions of , the stripper solution prepared by the stripper prepared in Preparation Example 1 is used to deeply strip the wet film on the printed circuit board in S4; S6, the second pressurized spray film removal process, at a pressure of 4kg / m 2 Under the conditions of , the stripper solution prepared by the stripper prepared in Preparation Example 1 is used to deeply strip the wet film on the printed circuit board in S5; S7, multi-stage pressure difference pressurized spray washing process, the printed circuit board in S6 is sequentially subjected to 2.5kg / m 2 Pressure water washing under pressure, 12kg / m 2 Swing high pressure water washing under pressure and 2.5kg / m 2 Pressurized water washing under pressure until the wet film residue within the line width and line spacing of the metal line within 50μm is removed and there is no excessive reaction on the surface of the metal line; S8. Use hot air to blow away the moisture on the surface of the printed circuit board, and obtain the printed circuit board after drying.

[0037] Example 2 A method for removing dehumidification film in a printed circuit board selection process, which is different from Example 1.1 in that the stripping agent prepared in Preparation Example 1 in S2, S3, S4, S5 and S6 is replaced by the stripping agent prepared in Preparation Example 2, and the rest is the same as Example 1.1.

[0038] Example 3 A method for removing dehumidification film in a printed circuit board selection process, which is different from Example 1.1 in that the stripping agent prepared in Preparation Example 1 in S2, S3, S4, S5 and S6 is replaced by the stripping agent prepared in Preparation Example 3, and the rest is the same as Example 1.1.

[0039] Example 4 A method for removing dehumidification film in a printed circuit board selection process, which is different from Example 1.1 in that the stripping agent prepared in Preparation Example 1 in S2, S3, S4, S5 and S6 is replaced by the stripping agent prepared in Preparation Example 4, and the rest is the same as Example 1.1.

[0040] Example 5 A method for removing dehumidification film in a printed circuit board selection process, which is different from Example 1.1 in that the stripping agent prepared in Preparation Example 1 in S2, S3, S4, S5 and S6 is replaced by the stripping agent prepared in Preparation Example 5, and the rest is the same as Example 1.1.

[0041] Comparative Example 1 The difference from Example 1.1 is that the stripping agent prepared in Preparation Example 1 is replaced by a commonly used sodium hydroxide stripping liquid, and the rest is the same as Example 1.1.

[0042] Comparative Example 2 The difference from Example 1.1 is that the composite alkali in the stripping agent prepared in Preparation Example 1 is replaced by sodium hydroxide, and the rest is the same as Example 1.1.

[0043] Comparative Example 3 The difference from Example 1.1 is that the propylene glycol block polyether L-64 in the stripping agent prepared in Preparation Example 1 is replaced by benzotriazole, and the rest is the same as Example 1.1.

[0044] Comparative Example 4 The difference from Example 1.1 is that the propylene glycol block polyether L-64 in the stripping agent prepared in Preparation Example 1 is replaced by sodium alkylbenzene sulfonate, and the rest is the same as Example 1.1.

[0045] Comparative Example 5 The difference from Example 1.1 is that the propylene glycol block polyether L-64 in the stripping agent prepared in Preparation Example 1 is replaced by dimethyl dioctadecyl ammonium chloride, CAS No. 61789-80-8, and the rest is the same as Example 1.1.

[0046] Comparative Example 6 The difference from Example 1.1 is that the existing film stripping method is used, and the rest is the same as Example 1.1, specifically, I. Providing a printed circuit board with a wet film formed on the surface; II. Soaking and swelling the wet film on the printed circuit board in I; III. The wet film on the printed circuit board in II is stripped by immersion and spraying without pressure in turn; IV. Wash the printed circuit board in III by non-pressurized spray water, 1.5kg / m 2 Pressurized water washing under pressure; V. Use hot air to blow away the moisture on the surface of the printed circuit board, and obtain the printed circuit board after drying.

[0047] Comparative Example 7 The difference from Example 1.1 is that in S2 and S3, only the pressure is 2 kg / m 2 The preliminary leavening and deep leavening were carried out under the conditions of , and the rest was the same as in Example 1.1.

[0048] Comparative Example 8 The difference from Example 1.1 is that in S2 and S3, preliminary swelling and deep swelling are only performed under the condition of an ultrasonic frequency range of 20 kHz, and the rest is the same as Example 1.1.

[0049] Detection experiment 56 test boards with a size of 400×500 mm were made, and these test boards were evenly divided into 4 groups. Each group of test boards had line patterns with line widths and line spacings of 50 / 50μm, 75 / 75μm, 100 / 100μm, and 125 / 125μm, respectively, and the 14 test boards in each group were used to test the film stripping processes of Examples 1.1-5 and Comparative Examples 1-8, respectively. Each group of test boards was produced according to the normal production process of printed circuit boards, i.e., pretreatment → wet film pasting → exposure → development → stripping → gold treatment → film stripping → inspection, wherein the film stripping process was compared and tested according to the methods of the above-mentioned embodiments and comparative examples, and the temperature during film stripping was 51°C, and the processes used in the other processes were exactly the same. After the film stripping was completed, each group of printed circuit boards was inspected, and the corresponding film stripping time and film stripping effect of each group were recorded in Table 1.

[0050] Table 1 Detection experiment results

[0051] As can be seen from Table 1, Examples 1.1-5 of the present application can completely remove the wet film on the surface of the printed circuit board in 8-13 minutes, and there is no residue even for fine line spacing, and there is no large-area oxidation blackening on the copper surface. The only difference between Examples 2-5 and 1.1 is that the selective film stripping liquid prepared in different preparation examples is used. As can be seen from Table 1, when Example 3 further optimizes the ratio between the composite alkali and the polyether, the removal effect of the film stripper on the wet film on the surface of the printed circuit board can be further improved, and the copper surface is bright and free of oxidation blackening. In addition, although the copper surface of Example 5 is bright and free of oxidation blackening, there is a slight tendency of oxidation blackening, and the film stripping efficiency is also worse than that of Example 3. Therefore, if the ratio between the components in the film stripper is not optimized, not only will the wet film on the surface of the printed circuit board fail to be effectively removed, but the metal will also be corroded.

[0052] The difference between Comparative Example 1 and Example 1 is that the stripping agent is replaced with a conventional sodium hydroxide stripping solution. It can be seen from Table 1 that when the stripping time is 16-18 minutes, the wet film on the printed circuit board cannot be completely removed, there is still a small amount of dot-shaped residual film between the line spacing, and there is a large area of ​​oxidation and blackening on the copper surface, which reduces the quality of the product.

[0053] The difference between Comparative Example 2 and Example 1 is that the composite alkali in the stripping agent is replaced with sodium hydroxide. As can be seen from Table 1, Comparative Example 2 still cannot remove the wet film on the printed circuit board when the stripping time is 15-17 minutes, and there is still a small amount of dot-shaped residual film between the lines. In addition, after stripping, the copper surface has a large area of ​​oxidation and blackening, which reduces the quality of the product.

[0054] The difference between Comparative Example 3 and Example 1 is that the polyether surfactant in the stripping agent is replaced with benzotriazole. As can be seen from Table 1, when the stripping time of Comparative Example 3 is 12-14 minutes, the wet film on the printed circuit board cannot be completely removed, there is still a trace amount of residual film in the form of dots between the lines, and the copper surface is slightly oxidized and blackened after stripping.

[0055] The difference between Comparative Example 4-5 and Example 1 is that the polyether surfactant in the stripping agent is replaced with other commonly used surfactants. It can be seen from Table 1 that Comparative Example 4-5 still cannot completely remove the wet film on the printed circuit board when the stripping time is 13-15 minutes, there is still a trace amount of residual film in the form of dots between the lines, and the copper surface is slightly oxidized and blackened after stripping.

[0056] The difference between Comparative Example 6 and Example 1 is that the existing film stripping process is used for film stripping. As can be seen from Table 1, when the film stripping time of Comparative Example 6 is 12 minutes, there are still trace dot-like residues in places with larger line widths and line spacings. When the film stripping time is 13-15 minutes, there are a small amount of dot-like residues in places with fine line widths and line spacings. Its film stripping time and film stripping effect are significantly worse than those of Example 1.

[0057] The difference between Comparative Example 7-8 and Example 1 is that the expansion stage does not use the method of simultaneous pressurized spray expansion and ultrasonic expansion. It can be seen from Table 1 that Comparative Example 7-8 can remove the wet film at the place with larger line width and line spacing when the film stripping time is 10 minutes, but there are still trace dot-like residues at the place with fine line width and line spacing at 12 minutes, and its film stripping effect is worse than that of Example 1.

[0058] Therefore, the above experimental results show that the method of removing the wet film in the printed circuit board selection process of the present application can not only completely remove the wet film covering the surface of the printed circuit board, but also has a high film removal speed, while improving the problem of large-area oxidation and blackening on the copper surface after film removal. It has both high product quality and high production efficiency, greatly improves the factory's production capacity, reduces production costs, and improves factory benefits.

[0059] The embodiments of this specific implementation method are all preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, all equivalent changes made based on the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for removing a dehumidifying film in a printed circuit board selection process, characterized in that: The following steps are involved: S1. providing a printed circuit board having a wet film formed on the surface; S2, a preliminary swelling process, which is to perform preliminary swelling on the wet film on the printed circuit board in S1; S3, pressurized ultrasonic spray bulking process, at a pressure of ≥ 2kg / m 2 , under the condition of ultrasonic frequency ≥ 20KHz, the wet film on the printed circuit board in S2 is deeply expanded; S4, a preliminary film stripping process, which is to initially strip the wet film on the printed circuit board in S3; S5, the first pressurized spray film removal process, at a pressure of ≥ 2kg / m 2 Under the condition of , the wet film on the printed circuit board in S4 is deeply stripped; S7, a multi-stage pressure difference pressurized spray washing process, in which the printed circuit board is washed with water under the condition that the pressure is first increased and then decreased, until the wet film residue within the line width and line spacing of the metal line is removed within 50μm and there is no excessive reaction on the surface of the metal line; Among them, the mass concentration of S2, S3, S4 and S5 is 10-20kg / m 3 The stripping agent solution comprises, by mass percentage, 15-55% of a composite alkali, 1-10% of a polyether surfactant, and the remainder of water.

2. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 1, characterized in that: The stripping agent comprises, by mass percentage, 35% of a composite alkali, 10% of a polyether surfactant, and 55% of water.

3. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 1, characterized in that: The initial expansion in S2 is at a pressure of ≥2kg / m 2 , and the ultrasonic frequency is ≥20KHz.

4. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 3, characterized in that: In S2 and S3, the pressure range is 2-4kg / m 2 , the ultrasonic frequency range is 20-40KHz.

5. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 1, characterized in that: The initial removal of the wet film in S4 is performed at a pressure of ≥ 2 kg / m 2 under the conditions of.

6. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 5, characterized in that: The method further comprises: S6, a second pressurized spraying film removal step, at a pressure of ≥2kg / m 2 Under the condition of , the wet film on the printed circuit board in step S5 is deeply stripped.

7. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 6, characterized in that: In S4, S5 and S6, the pressure range is 2-4 kg / m 2 .

8. The method for removing a dehumidifying film in a printed circuit board selection process according to claim 1, characterized in that: The S7 includes three stages of spray water washing, and the pressure of each stage is set to 1.5-2.5 kg / m 2 10-12kg / m 2 and 1.5-2.5kg / m 2 .

9. A printed circuit board, characterized in that: According to the method for removing moisture film in the selective process of printed circuit boards according to any one of claims 1 to 8, the line width and line spacing of the metal lines of the printed circuit boards are both below 75 μm, the line thickness of the metal lines of the printed circuit boards is below 18 μm, and after the selective process is completed, no dot-like wet film remains between the metal lines and the surface of the metal lines is bright.

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