Retreating and washing method for solder resist ink of printed circuit board and printed circuit board

Abstract

The invention provides a back washing method for solder resist ink of a printed circuit board and the printed circuit board. The printed circuit board solder resist ink back washing method comprises the following steps: obtaining a back washing circuit board; carrying out one-time ultrasonic immersion cleaning operation on the back-washed circuit board so as to enable the back-washed circuit board to be immersed in a stripping agent under the ultrasonic conditions that 36-42 vibrators are distributed on the ultrasonic sound production surface every 700mm * 600mm, the ultrasonic frequency is 35kHz-40kHz and the ultrasonic power is 50W-65W to obtain a pretreated circuit board; and carrying out secondary ultrasonic immersion cleaning operation on the pretreated circuit board, so that the pretreated circuit board is immersed in water under the ultrasonic condition. According to the back washing method for the solder resist ink of the printed circuit board, the problems that textures are poorly exposed, a copper surface is easy to damage and mechanical damage is caused can be well relieved, the operation steps are simple, and the generation amount of cleaning waste liquid can be well reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of printed circuit board processing, and particularly to a method for stripping and washing solder mask ink on a printed circuit board and a printed circuit board. Background Art

[0002] In the processing and production of PCBs (Printed Circuit Boards), the main process of the existing solder mask process is: pre-treatment before solder mask → screen printing → pre-baking → alignment exposure → development → QC inspection → the next solder mask process (stripping and washing of defective boards). When stripping and washing defective boards, in order to ensure the removal effect of the solder mask ink, the immersion time for through-holes is set relatively long, and it is still difficult to completely remove the ink in the plugged vias. Specifically, at present, the PCB is mostly immersed in the stripping agent under ultrasonic conditions and the residual ink is washed with a high-pressure water gun, and they all have the following problems:

[0003] 1. Insufficient immersion time results in ink residue;

[0004] 2. Excessive immersion time makes the PCB prone to poor texture exposure and the copper surface is easily damaged;

[0005] 3. Excessive or too strong ultrasonic time causes mechanical damage to the PCB.

[0006] For example, in the invention patent application with the application number CN202110631423.3, it reduces the ink residue by controlling the immersion time and ultrasonic time, and better alleviates the problems of poor texture exposure and easy damage to the copper surface. However, it is necessary to immerse the PCB in the stripping agent for soaking and cleaning once, and then still need to immerse it in the stripping agent for soaking and cleaning. The operation steps are relatively cumbersome and a large amount of cleaning waste liquid will be generated. Another example is the invention patent application with the application number CN202310953947.3. It reduces the ink residue by controlling the immersion time, ultrasonic time and ultrasonic intensity, and better alleviates the problems of poor texture exposure, easy damage to the copper surface and mechanical damage. However, similarly, it is necessary to immerse the PCB in the alkaline solution for soaking and cleaning once, and then still need to immerse it in the stripping agent for soaking and cleaning. The operation steps are relatively cumbersome and a large amount of cleaning waste liquid will be generated. Summary of the Invention

[0007] An object of the present invention is to overcome the deficiencies in the prior art and provide a method for stripping and washing solder mask ink on a printed circuit board and a printed circuit board that can better alleviate the problems of poor texture exposure, easy damage to the copper surface and mechanical damage, and has relatively simple operation steps and can better reduce the generation amount of cleaning waste liquid.

[0008] The object of the present invention is achieved by the following technical solutions:

[0009] A method for stripping and washing a solder mask ink on a printed circuit board, comprising the following steps:

[0010] Obtain the circuit board to be stripped and washed;

[0011] Perform a primary ultrasonic immersion cleaning operation on the circuit board to be stripped and washed, so that under the ultrasonic conditions where there are 36 to 42 vibrators distributed per 700mm * 600mm on the ultrasonic sound emitting surface, the ultrasonic frequency is 35kHz to 40kHz, and the ultrasonic power is 50W to 65W, the circuit board to be stripped and washed is immersed in the stripping agent to obtain a pretreated circuit board;

[0012] Perform a secondary ultrasonic immersion cleaning operation on the pretreated circuit board, so that under the ultrasonic conditions, the pretreated circuit board is immersed in water.

[0013] In one embodiment, perform a primary ultrasonic immersion cleaning operation on the circuit board to be stripped and washed under the condition that the temperature is 80°C to 90°C.

[0014] In one embodiment, perform a secondary ultrasonic immersion cleaning operation on the pretreated circuit board under the condition that the temperature is 50°C to 70°C.

[0015] In one embodiment, under the ultrasonic conditions where there are 36 to 42 vibrators distributed per 700mm * 600mm on the ultrasonic sound emitting surface, the ultrasonic frequency is 40kHz to 60kHz, and the ultrasonic power is 50W to 65W, the pretreated circuit board is immersed in water.

[0016] In one embodiment, under the ultrasonic conditions where there are 36 vibrators distributed per 700mm * 600mm on the ultrasonic sound emitting surface, the ultrasonic frequency is 40kHz, and the ultrasonic power is 60W, the pretreated circuit board is immersed in water.

[0017] In one embodiment, under the ultrasonic conditions where there are 36 vibrators distributed per 700mm * 600mm on the ultrasonic sound emitting surface, the ultrasonic frequency is 40kHz, and the ultrasonic power is 60W, the circuit board to be stripped and washed is immersed in the stripping agent.

[0018] In one embodiment, the circuit board to be stripped and washed is immersed in the stripping agent for 12min to 20min.

[0019] In one embodiment, the pretreated circuit board is immersed in water for 25min to 38min.

[0020] In one embodiment, under the condition that the temperature is 80°C, the circuit board to be stripped and washed is immersed in the stripping agent for 15min.

[0021] In one embodiment, the pretreated circuit board is immersed in water for 30 min under the condition that the temperature is 60 °C.

[0022] A printed circuit board is processed by the method for stripping and washing the solder mask ink of the printed circuit board according to any one of the above embodiments.

[0023] Compared with the prior art, the present invention has at least the following advantages:

[0024] The method for stripping and washing the solder mask ink of the printed circuit board of the present invention enables 36 to 42 oscillators to be distributed per 700 mm * 600 mm on the ultrasonic sound-emitting surface, the ultrasonic frequency is 35 kHz to 40 kHz, and the ultrasonic power is 50 W to 65 W. Under the ultrasonic conditions, the stripped circuit board is immersed in the stripping agent, which not only increases the size of the ultrasonic sound-emitting surface to 700 mm * 600 mm, but also improves the design density of the oscillators, so that 36 to 42 oscillators are distributed on the ultrasonic sound-emitting surface. Combined with the ultrasonic frequency of 35 kHz to 40 kHz, it effectively ensures the coverage rate of the sound field in the hole wall at the end corresponding to the ultrasonic sound-emitting surface; combined with the ultrasonic power of 50 W to 65 W, even though the power of a single oscillator is low, the total power of all oscillators increases. On the basis of reducing the problem of mechanical damage to the stripped circuit board caused by the high power of a single oscillator, it preferably ensures the intensity of the sound field in the hole wall of the stripped circuit board, and then preferably combines with the stripping agent to quickly and effectively remove the solder mask ink of the stripped circuit board, reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink. Combined with soaking the pretreated circuit board in water under ultrasonic conditions, on the one hand, the ultrasonic wave effectively cleans and removes the stripping agent on the pretreated circuit board, and on the other hand, the stripping agent and water act on the pretreated circuit board again. At this time, the ink in the pretreated circuit board is washed out of the hole, and under ultrasonic conditions, the ink in the hole is further gently softened and stripped. Therefore, the effective removal of the solder mask ink can be effectively achieved by soaking in the stripping agent once and in water once, the operation steps are simplified, and the generation of cleaning waste liquid can be effectively reduced. Description of the Drawings

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a flowchart of the method for stripping and washing the solder mask ink of the printed circuit board according to an embodiment of the present invention. Detailed implementation manners

[0027] For ease of understanding the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present invention can be understood more thoroughly and comprehensively.

[0028] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only embodiments.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0030] The present application provides a method for stripping and washing a solder resist ink of a printed circuit board. The above method for stripping and washing a solder resist ink of a printed circuit board includes the following steps: obtaining a circuit board to be stripped and washed; performing a first ultrasonic immersion washing operation on the circuit board to be stripped and washed, so that under the ultrasonic condition that there are 36 to 42 vibrators distributed per 700 mm * 600 mm on the ultrasonic sound emitting surface, the ultrasonic frequency is 35 kHz to 40 kHz, and the ultrasonic power is 50 W to 65 W, the circuit board to be stripped and washed is immersed in a stripping agent to obtain a pretreated circuit board; performing a second ultrasonic immersion washing operation on the pretreated circuit board, so that under the ultrasonic condition, the pretreated circuit board is immersed in water.

[0031] The above-mentioned method for stripping solder mask ink of printed circuit boards is such that 36 to 42 vibrators are distributed per 700mm*600mm of the ultrasonic sounding surface, the ultrasonic frequency is 35kHz~40kHz, and the ultrasonic power is 50W~65W. Under ultrasonic conditions, the stripping circuit board is immersed in a stripping agent, so that the size of the ultrasonic sounding surface is increased to 700mm*600mm, and the design density of the vibrators is improved, so that 36 to 42 vibrators are distributed on the ultrasonic sounding surface. Combined with the ultrasonic frequency of 35kHz~40kHz, the coverage of the sound field in the hole wall at the end corresponding to the ultrasonic sounding surface is effectively ensured; combined with the ultrasonic power of 50W~65W, the power of a single vibrator is low, but the total power of all vibrators is increased, while reducing the mechanical damage of the stripping circuit board caused by the high power of a single vibrator. On the basis of solving the problem of mechanical damage, the intensity of the acoustic field in the hole wall of the stripping circuit board is better ensured, and then the stripping agent is better combined to quickly and effectively realize the effective removal of the solder mask ink of the stripping circuit board, reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the immersion time to ensure the cleaning and removal effect of the solder mask ink. Under ultrasonic conditions, the pretreated circuit board is immersed in water. On the one hand, the ultrasound is used to effectively clean and remove the stripping agent of the pretreated circuit board. On the other hand, the stripping agent and water are applied to the pretreated circuit board again. At this time, the ink in the pretreated circuit board is cleaned out of the hole, and under ultrasonic conditions, the ink in the hole is further gently softened and stripped. Therefore, the effective removal of the solder mask ink can be effectively achieved in one stripping agent and one water immersion, the operation steps are simplified, and the generation of cleaning waste liquid can be effectively reduced.

[0032] In order to better understand the stripping method of the printed circuit board solder mask ink of the present application, the stripping method of the printed circuit board solder mask ink of the present application is further explained below:

[0033] See also Figure 1 A method for stripping solder resist ink from a printed circuit board according to one embodiment of the present invention comprises the following steps:

[0034] S100: Obtain a de-cleaned circuit board.

[0035] It can be understood that the stripped circuit board is a printed circuit board whose solder resist ink in the holes needs to be further removed based on the welding quality and reliability of the printed circuit board to be prepared, thereby ensuring the welding quality and reliability of the printed circuit board to reduce the short circuit and open circuit problems of the printed circuit board.

[0036] S200. Perform a primary ultrasonic immersion cleaning operation on the degreased and washed circuit board, so that 36 to 42 oscillators are distributed per 700mm * 600mm on the ultrasonic sound-emitting surface, the ultrasonic frequency is 35kHz to 40kHz, and the ultrasonic power is 50W to 65W. Under such ultrasonic conditions, immerse the degreased and washed circuit board in the stripping agent to obtain a pretreated circuit board.

[0037] It can be understood that the ultrasonic sound-emitting surface is the surface where the ultrasonic transducer directly contacts the stripping agent and emits sound waves. The ultrasonic transducer is the oscillator, that is, the ultrasonic sound-emitting surface is the surface where the oscillator directly contacts the stripping agent and emits sound waves, so that the specification of the ultrasonic sound-emitting surface is that 36 to 42 oscillators are distributed per 700mm * 600mm, and under the ultrasonic conditions of an ultrasonic frequency of 35kHz to 40kHz and an ultrasonic power of 50W to 65W, immerse the degreased and washed circuit board in the stripping agent. In this way, not only is the size of the ultrasonic sound-emitting surface increased to 700mm * 600mm, but also the design density of the oscillators is increased, so that 36 to 42 oscillators are distributed on the ultrasonic sound-emitting surface. Combined with the ultrasonic frequency of 35kHz to 40kHz, the coverage rate of the sound field in the hole wall at the end corresponding to the ultrasonic sound-emitting surface is effectively ensured; combined with the ultrasonic power of 50W to 65W, although the power of a single oscillator is relatively low, the total power of all oscillators increases. On the basis of reducing the problem of mechanical damage to the degreased and washed circuit board caused by the high power of a single oscillator, the intensity of the sound field in the hole wall of the degreased and washed circuit board is preferably ensured, and then combined with the stripping agent to quickly and effectively achieve the effective removal of the solder mask ink on the degreased and washed circuit board, reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink.

[0038] S300. Perform a secondary ultrasonic immersion cleaning operation on the pretreated circuit board, so that under ultrasonic conditions, the pretreated circuit board is immersed in water.

[0039] It can be understood that after taking the degreased and washed circuit board out of the stripping agent and immersing it in water, on the one hand, the ultrasonic wave is used to effectively clean and remove the stripping agent on the pretreated circuit board, and on the other hand, the stripping agent and water act on the pretreated circuit board again. At this time, the ink in the pretreated circuit board is washed out of the hole, and under ultrasonic conditions, the ink in the hole is further gently softened and stripped. Therefore, the effective removal of the solder mask ink can be effectively achieved by soaking in the primary stripping agent and the primary water once, simplifying the operation steps and effectively reducing the generation of cleaning waste liquid.

[0040] The above-described method for stripping and cleaning the solder mask ink of a printed circuit board enables 36 to 42 oscillators to be distributed per 700 mm * 600 mm on the ultrasonic sound-emitting surface. Under the ultrasonic conditions where the ultrasonic frequency is 35 kHz to 40 kHz and the ultrasonic power is 50 W to 65 W, the circuit board to be stripped and cleaned is immersed in the stripping agent. This not only increases the size of the ultrasonic sound-emitting surface to 700 mm * 600 mm but also improves the design density of the oscillators, resulting in 36 to 42 oscillators being distributed on the ultrasonic sound-emitting surface. Combined with the ultrasonic frequency of 35 kHz to 40 kHz, it effectively ensures the coverage rate of the sound field within the hole wall at the end corresponding to the ultrasonic sound-emitting surface. With the ultrasonic power of 50 W to 65 W, although the power of a single oscillator is relatively low, the total power of all oscillators increases. On the basis of reducing the problem of mechanical damage to the circuit board to be stripped and cleaned caused by the high power of a single oscillator, it better ensures the intensity of the sound field within the hole wall of the circuit board to be stripped and cleaned, and thus better combines with the stripping agent to quickly and effectively achieve the effective removal of the solder mask ink on the circuit board to be stripped and cleaned. This reduces the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink. In combination with immersing the pretreated circuit board in water under ultrasonic conditions, on the one hand, it effectively cleans and removes the stripping agent on the pretreated circuit board using ultrasound, and on the other hand, it enables the stripping agent and water to act on the pretreated circuit board again. At this time, the ink in the pretreated circuit board is cleaned and detached from the hole, and under ultrasonic conditions, the ink in the hole is further gently softened and stripped. Therefore, the effective removal of the solder mask ink can be effectively achieved by soaking in the stripping agent once and in water once, simplifying the operation steps and effectively reducing the generation of cleaning waste liquid.

[0041] It should be noted that the number of ultrasonic sound-emitting surfaces is two, and the two ultrasonic sound-emitting surfaces are arranged on the opposite side walls of the tank in which the circuit board to be stripped and cleaned is immersed. Further, the projection of the circuit board to be stripped and cleaned on the side wall of the tank corresponding to each ultrasonic sound-emitting surface is located within the ultrasonic sound-emitting surface. It can be understood that with the ultrasonic frequency of 35 kHz to 40 kHz, the bilateral ultrasonic sound-emitting surfaces are more focused on the ends of the corresponding holes of the circuit board to be stripped and cleaned for cleaning the solder mask ink, effectively ensuring the intensity of the sound field within the hole wall of the circuit board to be stripped and cleaned, and thus better combining with the stripping agent to quickly and effectively achieve the effective removal of the solder mask ink on the circuit board to be stripped and cleaned. This reduces the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink. It can also be understood that if the number of ultrasonic sound-emitting surfaces is single and the ultrasonic frequency is 35 kHz to 40 kHz, the loss of sound energy at the deeper position of the hole is relatively large, that is, the removal effect of the solder mask ink at the deeper position of the hole is relatively poor. As a result, it is difficult to effectively remove the solder mask ink at the deeper position of the hole even by extending the soaking time in the stripping agent.

[0042] In one embodiment, the stripping agent is an alkaline stripping agent. It should be noted that the stripping agent used in this application is a solder mask stripping agent commonly used for stripping and washing the solder mask ink of printed circuit boards. In particular, the alkaline stripping agent consists of 10% KOH / NaOH, 1% benzotriazole, and 0.5% nano-SiO₂. Further, the alkaline stripping agent is a conventional solder mask stripping agent for stripping and washing the solder mask ink of printed circuit boards, especially for stripping the solder mask ink of thick copper boards. Therefore, the preparation method of the stripping agent will not be elaborated in this application. It can also be understood that by using the alkaline stripping agent containing 10% KOH / NaOH, 1% benzotriazole, and 0.5% nano-SiO₂ and in combination with ultrasonic conditions, the washed circuit board is immersed in the alkaline stripping agent, effectively and rapidly achieving the effective removal of the solder mask ink on the washed circuit board.

[0043] In one embodiment, under the condition that the temperature is 80°C to 90°C, a primary ultrasonic immersion washing operation is performed on the washed circuit board. It can be understood that under the condition that the temperature is 80°C to 90°C, the washed circuit board is immersed in the stripping agent, further effectively shortening the stripping time of the solder mask ink on the washed circuit board, that is, effectively improving the stripping efficiency of the solder mask ink on the washed circuit board, and then rapidly and effectively achieving the effective removal of the solder mask ink on the washed circuit board.

[0044] In one embodiment, under the condition that the temperature is 50°C to 70°C, a secondary ultrasonic immersion washing operation is performed on the pretreated circuit board. It can be understood that under the condition that the temperature is 50°C to 70°C, the pretreated circuit board is immersed in water, which preferably ensures the further gentle and effective stripping of the solder mask ink on the pretreated circuit board, and then ensures that the effective removal of the solder mask ink can be achieved effectively with only one stripping agent and one immersion in water. The operation steps are simplified, and the generation of cleaning waste liquid can be effectively reduced.

[0045] In one embodiment, 36 to 42 oscillators are distributed per 700 mm * 600 mm on the ultrasonic sound-emitting surface. Under the ultrasonic conditions where the ultrasonic frequency is 40 kHz to 60 kHz and the ultrasonic power is 50 W to 65 W, the pre-treated circuit board is immersed in water. It can be understood that under the ultrasonic conditions where 36 to 42 oscillators are distributed per 700 mm * 600 mm on the ultrasonic sound-emitting surface, the ultrasonic frequency is 40 kHz to 60 kHz, and the ultrasonic power is 50 W to 65 W, immersing the pre-treated circuit board in water means increasing the size of the ultrasonic sound-emitting surface to 700 mm * 600 mm, and increasing the design density of the oscillators so that 36 to 42 oscillators are distributed on the ultrasonic sound-emitting surface. Combined with the ultrasonic frequency of 40 kHz to 60 kHz, it effectively ensures the coverage rate of the sound field within the hole wall at the end corresponding to the ultrasonic sound-emitting surface; combined with the ultrasonic power of 50 W to 65 W, even though the power of a single oscillator is relatively low, the total power of all oscillators increases. On the basis of reducing the problem of mechanical damage to the pre-treated circuit board caused by the high power of a single oscillator, it better ensures the intensity of the sound field within the hole wall of the pre-treated circuit board, and then better combines with water to gently and effectively achieve the softening and peeling of the solder mask ink on the pre-treated circuit board. Therefore, the effective removal of the solder mask ink can be effectively achieved by soaking in the first stripping agent and water once, simplifying the operation steps and effectively reducing the generation of cleaning waste liquid.

[0046] It should be noted that the number of ultrasonic sound-emitting surfaces is two, and the two ultrasonic sound-emitting surfaces are arranged on the opposite side walls of the tank in which the pre-treated circuit board is immersed. Further, the projection of the pre-treated circuit board on the side wall of the tank corresponding to each ultrasonic sound-emitting surface is located within the ultrasonic sound-emitting surface. It can be understood that combined with the ultrasonic frequency of 40 kHz to 60 kHz, the bilateral ultrasonic sound-emitting surfaces are more focused on the ends of the corresponding holes of the pre-treated circuit board for cleaning the solder mask ink, effectively ensuring the intensity of the sound field within the hole wall of the pre-treated circuit board, and then better combining with water to gently and effectively achieve the effective removal of the solder mask ink on the pre-treated circuit board. It can also be understood that if the number of ultrasonic sound-emitting surfaces is one, and combined with the ultrasonic frequency of 40 kHz to 60 kHz, the loss of sound energy at the deeper position of the hole is relatively large, that is, the removal effect of the solder mask ink at the deeper position of the hole is poor, and it is difficult to effectively remove the solder mask ink at the deeper position of the hole even if the soaking time in water is extended.

[0047] In one embodiment, 36 oscillators are distributed per 700mm * 600mm of the ultrasonic sound - emitting surface. Under the ultrasonic conditions where the ultrasonic frequency is 40kHz and the ultrasonic power is 60W, the pre - treated circuit board is immersed in water, which preferably ensures the gentle and effective softening and peeling of the solder mask ink on the pre - treated circuit board. Further, the pre - treated circuit board is immersed in water under a negative pressure environment of - 0.5bar to - 1bar. It can be understood that immersing the pre - treated circuit board in water under a negative pressure environment of - 0.5bar to - 1bar reduces the liquid vaporization threshold during ultrasonic cleaning, makes cavitation bubbles easier to generate and have stronger collapse energy, and reduces the attenuation of sound energy in the middle part of the holes, effectively improving the removal efficiency and effect of the solder mask ink on the pre - treated circuit board.

[0048] In one embodiment, 36 oscillators are distributed per 700mm * 600mm of the ultrasonic sound - emitting surface. Under the ultrasonic conditions where the ultrasonic frequency is 40kHz and the ultrasonic power is 60W, the post - washed circuit board is immersed in the stripping agent, which preferably ensures the removal efficiency and effect of the solder mask ink on the post - washed circuit board. Further, the post - washed circuit board is immersed in the stripping agent under a negative pressure environment of - 0.5bar to - 1bar. It can be understood that immersing the pre - treated circuit board in water under a negative pressure environment of - 0.5bar to - 1bar reduces the liquid vaporization threshold during ultrasonic cleaning, makes cavitation bubbles easier to generate and have stronger collapse energy, and reduces the attenuation of sound energy in the middle part of the holes, effectively improving the removal efficiency and effect of the solder mask ink on the post - washed circuit board. Further, the post - washed circuit board is immersed in the stripping agent under a negative pressure environment of - 0.5bar.

[0049] In one embodiment, the post - washed circuit board is immersed in the stripping agent for 12min to 20min. Further, under the condition of a temperature of 80°C, the post - washed circuit board is immersed in the stripping agent for 15min, which preferably ensures the removal efficiency and effect of the solder mask ink on the post - washed circuit board.

[0050] In one embodiment, the pre - treated circuit board is immersed in water for 25min to 38min. Further, under the condition of a temperature of 60°C, the pre - treated circuit board is immersed in water for 30min, which preferably ensures the removal efficiency and effect of the solder mask ink on the pre - treated circuit board.

[0051] In one embodiment, the ultrasonic sound emission surfaces provided on the opposite side walls of the tank for soaking the degreasing circuit board are symmetrically arranged about the central axis, that is, all the oscillators forming one ultrasonic sound emission surface and all the oscillators forming the other ultrasonic sound emission surface are symmetrically arranged about the central axis. Further, the opposite two plate surfaces of the circuit board are arranged in one-to-one correspondence with the two ultrasonic sound emission surfaces. It can be understood that the two ultrasonic sound emission surfaces simultaneously perform ultrasonic treatment on the two end portions of any hole respectively. Thus, combined with the setting of ultrasonic parameters, the stripping agent is better combined to quickly and effectively achieve the effective removal of the solder resist ink on the degreasing circuit board, reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder resist ink.

[0052] Further, the plate surface of the degreasing circuit board is inclined at an angle of 15° to 75° with respect to the horizontal plane. Further, during the process of soaking the degreasing circuit board in the stripping agent, the angle at which the plate surface of the degreasing circuit board is inclined with respect to the horizontal plane changes uniformly with time. Further, at the initial stage of soaking the degreasing circuit board in the stripping agent, the plate surface of the degreasing circuit board is inclined at an angle of 15° with respect to the horizontal plane. Then, the change amount of the inclination angle is 60° divided by the total soaking time of the degreasing circuit board in the stripping agent until the angle at which the degreasing circuit board is inclined with respect to the horizontal plane is 75°. It can be understood that due to the attenuation of the sound pressure of ultrasonic cleaning at the position where the distance between the hole wall facing the ultrasonic sound emission surface and the ultrasonic sound emission surface is relatively far, the residual rate of the degreasing of the solder resist ink at the position where the distance between the hole wall facing the ultrasonic sound emission surface and the ultrasonic sound emission surface is relatively far is relatively high. Therefore, inclining the plate surface of the degreasing circuit board at an angle of 15° to 75° with respect to the horizontal plane causes standing waves to be formed in the hole by the two-sided sound waves, significantly enhancing the sound pressure at the bottom of the hole and having a strong cavitation effect. And at the initial stage of soaking the degreasing circuit board in the stripping agent, the plate surface of the degreasing circuit board is inclined at an angle of 15° with respect to the horizontal plane. Then, the change amount of the inclination angle is 60° divided by the total soaking time of the degreasing circuit board in the stripping agent until the angle at which the degreasing circuit board is inclined with respect to the horizontal plane is 75°. In this way, each part of the inner wall of the hole is uniformly facing the ultrasonic sound emission surface during the change of the inclination angle, optimizing the discharge of solder resist ink debris, the enhancement of the sound field intensity, and the staged transformation cooperation of the cavitation movement path. Especially for the cleaning of the solder resist ink on the degreasing circuit board with a small aperture and a large aspect ratio of hole height, the cleaning efficiency and effect of the solder resist ink on the degreasing circuit board are further improved.

[0053] Further, the surface of the pre-treated circuit board is inclined at an angle of 15° to 75° with respect to the horizontal plane. Further, during the process of immersing the pre-treated circuit board in water, the angle of inclination of the pre-treated circuit board with respect to the horizontal plane changes uniformly with time. Further, at the initial stage when the pre-treated circuit board is immersed in water, the pre-treated circuit board is inclined at an angle of 15° with respect to the horizontal plane. Then, the change amount of the inclination angle is 60° divided by the total time of immersing the stripping circuit board in the stripping agent until the angle of inclination of the pre-treated circuit board with respect to the horizontal plane reaches 75°. It can be understood that during ultrasonic cleaning, at the position where the distance from the hole wall facing the ultrasonic sound generating surface to the ultrasonic sound generating surface is relatively far, due to the attenuation of the sound pressure of ultrasonic cleaning, the stripping residue rate of the solder resist ink at the position where the distance from the hole wall facing the ultrasonic sound generating surface to the ultrasonic sound generating surface is relatively far is relatively high. Therefore, inclining the surface of the pre-treated circuit board at an angle of 15° to 75° with respect to the horizontal plane enables standing waves to be formed by the sound waves on both sides in the hole, significantly enhancing the sound pressure at the bottom of the hole and having a strong cavitation effect. And at the initial stage when the pre-treated circuit board is immersed in water, the surface of the pre-treated circuit board is inclined at an angle of 15° with respect to the horizontal plane. Then, the change amount of the inclination angle is 60° divided by the total time of immersing the pre-treated circuit board in water until the angle of inclination of the pre-treated circuit board with respect to the horizontal plane reaches 75°. In this way, each part of the inner wall of the hole uniformly faces the ultrasonic sound generating surface during the change of the inclination angle, optimizing the cooperation of the discharge of solder resist ink debris, the enhancement of the sound field intensity, and the staged transformation of the cavitation movement path. Especially for the cleaning of the solder resist ink on the pre-treated circuit board with a relatively small aperture and a relatively large aspect ratio of hole height, the cleaning efficiency and effect of the solder resist ink on the pre-treated circuit board are further improved.

[0054] In one embodiment, before the step of performing an ultrasonic immersion cleaning operation on the stripped circuit board and after the step of obtaining the stripped circuit board, the method for stripping the solder mask ink of the printed circuit board further includes the following steps: performing laser micro-hole processing on the stripped circuit board to form micro-holes at the center of the solder mask ink on the stripped circuit board. Further, the center of the solder mask ink is an area surrounded by a diameter of 0.005 mm to 0.02 mm with the axis of the hole filled with the solder mask ink as the center. That is, the aperture of the micro-holes formed at the center of the solder mask ink on the stripped circuit board is 0.005 mm to 0.02 mm. Further, the laser micro-hole processing of the stripped circuit board is specifically operated as follows: using an ultraviolet laser to drill holes at the center of the solder mask ink on the stripped circuit board. It can be understood that for the through-holes of the holes filled with the solder mask ink of the circuit board with a high aspect ratio of the hole height, the time for through-holes is relatively long. Therefore, it is necessary to extend the soaking time of the stripping agent. However, the extension of the soaking time of the stripping agent will cause problems such as poor texture exposure and easy damage to the copper surface. Therefore, further using an ultraviolet laser to drill holes at the center of the solder mask ink on the stripped circuit board, that is, quickly realizing the through-holes of the holes filled with the solder mask ink in a mechanical manner. In this way, on the basis of reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink, the cleaning efficiency and effect of the solder mask ink on the stripped circuit board are further improved.

[0055] It should be noted that for printed circuit boards with a high aspect ratio of hole height, the set ultrasonic frequency is generally relatively low, such as 28 kHz, which can better ensure the sound energy intensity at the deeper position of the hole to ensure the cleaning and removal effect of the solder mask ink at the deeper position of the hole. If the set ultrasonic frequency is relatively high, it is easy to cause serious residue of the solder mask ink at the deeper position of the holes in the circuit board with a high aspect ratio of hole height. Therefore, those skilled in the art rarely set a relatively high ultrasonic frequency, such as 40 kHz. In this application, the ultrasonic frequency for immersing the stripping circuit board in the stripping agent is 35 kHz to 40 kHz, and the ultrasonic frequency for immersing the pre-treatment circuit board in water is 40 kHz to 60 kHz. This actually results in a poor treatment effect on the solder mask ink at the deeper position of the holes. However, further combined with 36 to 42 oscillators distributed per 700 mm * 600 mm, an ultrasonic power of 50 W to 65 W, and the number of ultrasonic sound emission surfaces being two, with the two ultrasonic sound emission surfaces being oppositely arranged on the opposite side walls of the tank in which the stripping circuit board is immersed, enabling the two ultrasonic sound emission surfaces to simultaneously perform ultrasonic cleaning on the two end walls of the hole. In this way, the influence of setting a relatively high ultrasonic frequency on the treatment effect of the solder mask ink at the deeper position of the holes is reduced, and on the basis of reducing the problems of mechanical damage, poor texture exposure, and copper surface damage of the stripping circuit board, the coverage rate of the sound field inside the hole wall at the end corresponding to the ultrasonic sound emission surface of the hole is increased, ensuring the intensity of the sound field inside the hole wall of the stripping circuit board, and then better combining with the stripping agent to quickly and effectively achieve the effective removal of the solder mask ink on the stripping circuit board.

[0056] It should also be noted that even if the ultrasonic sound emission surfaces are relatively arranged on the opposite side walls of the tank in which the stripping circuit board is immersed, if ultrasonic immersion cleaning in water is not further combined, it is still relatively difficult to effectively clean and remove the solder mask ink inside the holes of the stripping circuit board in a short soaking time by changing the ultrasonic parameters in the stripping agent. Therefore, it requires at least two immersions in the stripping agent and two flushes with a high-pressure gun. In this way, the operation steps are relatively cumbersome, and a large amount of cleaning waste liquid will be generated.

[0057] It should also be noted that if the ultrasonic generating surfaces are only relatively arranged on the opposite side walls of the tank in which the stripping circuit board is immersed, and the ultrasonic generating surfaces are relatively arranged on the opposite side walls of the tank in which the pre-treatment circuit board is immersed, combined with the setting of the ultrasonic parameters when immersed in the stripping agent and the setting of the ultrasonic parameters when immersed in water, for circuit boards with relatively small aperture and relatively large aspect ratio of hole height, the treatment effect of the solder mask ink still needs to be further improved. Therefore, in this application, all the oscillators forming one ultrasonic generating surface and all the oscillators forming the other ultrasonic generating surface are arranged in central axis symmetry, and in combination with the adjustment and change of the inclination angle of the stripping circuit board when immersed in the stripping agent and the adjustment and change of the inclination angle of the pre-treatment circuit board when immersed in water, the effective cleaning treatment of the solder mask ink on the circuit board with relatively small aperture and relatively large aspect ratio of hole height is better ensured. In addition, laser drilling is further combined with the center of the solder mask ink on the stripping circuit board, which further reduces the problem of poor texture exposure and easy damage to the copper surface, and improves the removal effect and efficiency of the solder mask ink on the stripping circuit board.

[0058] This application also provides a printed circuit board, which is processed by the method for stripping the solder mask ink of the printed circuit board in any of the above embodiments. Further, in this embodiment, the method for stripping the solder mask ink of the printed circuit board includes the following steps: obtaining a stripping circuit board; performing a primary ultrasonic immersion cleaning operation on the stripping circuit board, so that under the ultrasonic conditions where 36 to 42 oscillators are distributed per 700 mm * 600 mm on the ultrasonic generating surface, the ultrasonic frequency is 35 kHz to 40 kHz, and the ultrasonic power is 50 W to 65 W, the stripping circuit board is immersed in the stripping agent to obtain a pre-treated circuit board; performing a secondary ultrasonic immersion cleaning operation on the pre-treated circuit board, so that under the ultrasonic conditions, the pre-treated circuit board is immersed in water.

[0059] The above printed circuit board is processed by the method for stripping the solder mask ink of the printed circuit board, effectively improving the processing qualification rate of the printed circuit board.

[0060] Compared with the prior art, the present invention has at least the following advantages:

[0061] The stripping and cleaning method of the solder mask ink of the present invention immerses the stripping and cleaning circuit board in the stripping agent under the ultrasonic conditions where there are 36 to 42 oscillators distributed per 700 mm * 600 mm on the ultrasonic sound generating surface, the ultrasonic frequency is 35 kHz to 40 kHz, and the ultrasonic power is 50 W to 65 W. Even if the size of the ultrasonic sound generating surface is increased to 700 mm * 600 mm, and the design density of the oscillators is increased so that there are 36 to 42 oscillators distributed on the ultrasonic sound generating surface, combined with the ultrasonic frequency of 35 kHz to 40 kHz, it effectively ensures the coverage rate of the sound field in the hole wall at the end corresponding to the ultrasonic sound generating surface of the hole; combined with the ultrasonic power of 50 W to 65 W, even if the power of a single oscillator is low, but the total power of all oscillators increases. On the basis of reducing the problem of mechanical damage to the stripping and cleaning circuit board caused by the high power of a single oscillator, it preferably ensures the intensity of the sound field in the hole wall of the stripping and cleaning circuit board, and then preferably combines with the stripping agent to quickly and effectively achieve the effective removal of the solder mask ink of the stripping and cleaning circuit board, reducing the problems of poor texture exposure and easy damage to the copper surface caused by extending the soaking time to ensure the cleaning and removal effect of the solder mask ink. In cooperation with the ultrasonic conditions, the pretreated circuit board is immersed in water. On the one hand, the ultrasonic wave effectively cleans and removes the stripping agent on the pretreated circuit board. On the other hand, the stripping agent and water act on the pretreated circuit board again. At this time, the ink in the pretreated circuit board is cleaned and detached from the hole, and under the ultrasonic conditions, the ink in the hole is further gently softened and stripped. Therefore, the effective removal of the solder mask ink can be effectively achieved by soaking in the stripping agent and water once, simplifying the operation steps, and effectively reducing the generation of cleaning waste liquid.

[0062] The following are some specific examples. If % is mentioned, it means by weight percentage. It should be noted that the following examples do not exhaust all possible situations, and the materials used in the following examples can be obtained from commercial channels without special instructions.

[0063] Example 1

[0064] The hole depth is 1.6 mm, the hole diameter is 0.2 mm, and the board thickness of the stripping and cleaning circuit board ≤ 1.6 mm;

[0065] The alkaline stripping agent contains 10% KOH / NaOH, 1% benzotriazole and 0.5% nano-SiO2.

[0066] Example 2

[0067] The hole depth is 2.0 mm, the hole diameter is 0.2 mm, and the board thickness of the stripping and cleaning circuit board is 2.0 mm;

[0068] The alkaline stripping agent contains 10% KOH / NaOH, 1% benzotriazole and 0.5% nano-SiO2.

[0069] Example 3

[0070] The hole depth is 1.0 mm, the hole diameter is 0.1 mm, and the board thickness of the circuit board to be stripped and washed is 1.0 mm

[0071] The alkaline stripper contains 10% KOH / NaOH, 1% benzotriazole and 0.5% nano-SiO2.

[0072] Example 4

[0073] The hole depth is 1.6 mm, the hole diameter is 0.15 mm, and the board thickness of the circuit board to be stripped and washed is 1.6 mm

[0074] The alkaline stripper contains 10% KOH / NaOH, 1% benzotriazole and 0.5% nano-SiO2.

[0075] Example 5

[0076] The hole depth is 3.2 mm, the hole diameter is 0.25 mm, and the board thickness of the circuit board to be stripped and washed is 3.2 mm

[0077] The alkaline stripper contains 10% KOH / NaOH, 1% benzotriazole and 0.5% nano-SiO2.

[0078] The alkaline strippers in Examples 1-5 and the corresponding circuit boards to be stripped and washed are processed by the stripping and washing method of the solder mask ink of the present application. The number of circuit boards to be stripped and washed in each example is 1000, and the stripping and washing qualification rate of the printed circuit boards obtained after the combined treatment is calculated;

[0079] 1. The stripping and washing method of the solder mask ink of the present application is all the steps recorded above, but does not include laser micro-hole processing, and all parameters take the extreme values and intermediate values within the above ranges. Each parameter is tested with a single variable, and finally the stripping and washing qualification rate of all printed circuit boards is 100%;

[0080] 2. The stripping and washing method of the solder mask ink of the present application is all the steps recorded above, including laser micro-hole processing, and all parameters take the extreme values and intermediate values within the above ranges. Each parameter is tested with a single variable, and finally the stripping and washing qualification rate of all printed circuit boards is 100%. Moreover, compared with the experimental group without laser micro-hole processing, on the basis of achieving the same stripping and washing qualification rate of the printed circuit boards, the soaking time in the stripper can be reduced by 1 min to 3 min.

[0081] The above embodiments merely illustrate several implementation manners of the present invention. The description thereof is relatively specific and detailed, but shall not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several variations and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A method for stripping and cleaning solder mask ink on a printed circuit board, characterized in that, It includes the following steps: Obtain a degreased circuit board; Perform a primary ultrasonic immersion cleaning operation on the degreased circuit board, so that under the ultrasonic conditions where there are 36 to 42 vibrators distributed per 700mm * 600mm on the ultrasonic sound generating surface, the ultrasonic frequency is 35kHz to 40kHz, and the ultrasonic power is 50W to 65W, the degreased circuit board is immersed in the stripping agent to obtain a pretreated circuit board; Perform a secondary ultrasonic immersion cleaning operation on the pretreated circuit board, so that under the ultrasonic conditions, the pretreated circuit board is immersed in water.

2. The stripping and cleaning method of the solder mask ink for printed circuit boards according to claim 1, characterized in that Perform a primary ultrasonic immersion cleaning operation on the degreased circuit board under the condition that the temperature is 80°C to 90°C.

3. The stripping and washing method of the solder mask ink for printed circuit boards according to claim 1, characterized in that, Perform a secondary ultrasonic immersion cleaning operation on the pretreated circuit board under the condition that the temperature is 50°C to 70°C.

4. The stripping method of the solder resist ink for printed circuit boards according to claim 1, characterized in that, Under the ultrasonic conditions where there are 36 to 42 vibrators distributed per 700mm * 600mm on the ultrasonic sound generating surface, the ultrasonic frequency is 40kHz to 60kHz, and the ultrasonic power is 50W to 65W, the pretreated circuit board is immersed in water.

5. The stripping and washing method of the solder mask ink for printed circuit boards according to claim 1 or 4, characterized in that Under the ultrasonic conditions where there are 36 vibrators distributed per 700mm * 600mm on the ultrasonic sound generating surface, the ultrasonic frequency is 40kHz, and the ultrasonic power is 60W, the pretreated circuit board is immersed in water.

6. The stripping and washing method of the solder mask ink for printed circuit boards according to claim 1, wherein, Under the ultrasonic conditions where there are 36 vibrators distributed per 700mm * 600mm on the ultrasonic sound generating surface, the ultrasonic frequency is 40kHz, and the ultrasonic power is 60W, the degreased circuit board is immersed in the stripping agent.

7. The stripping and washing method of the solder mask ink for printed circuit boards according to claim 1, characterized in that, The degreased circuit board is immersed in the stripping agent for 12min to 20min.

8. The stripping method of the solder resist ink for printed circuit boards according to claim 1, wherein The pretreated circuit board is immersed in water for 25min to 38min.

9. The stripping method of the solder mask ink for printed circuit boards according to claim 1, characterized in that, Under the condition that the temperature is 80°C, the degreased circuit board is immersed in the stripping agent for 15min; and / or, Under the condition that the temperature is 60°C, the pretreated circuit board is immersed in water for 30min.

10. A printed circuit board, characterized in that, It is processed by the method for degreasing the solder resist ink of the printed circuit board according to any one of claims 1 to 9.

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