PCB solder mask silicon-free ink spraying method and device

Abstract

The invention discloses a PCB (Printed Circuit Board) solder resist silicon-free ink spraying method and equipment. The PCB solder resist silicon-free ink spraying method comprises the following steps of S100, performing pretreatment on a PCB after hole plugging; s200, a diluent is used for cleaning spraying equipment for the first time, and silicon-free solder resist ink is used for spraying the first face of the PCB after pretreatment; s300, after the spraying equipment is cleaned for the second time by using a diluent, spraying is carried out on the second surface of the PCB by using silicon-free solder resist ink; s400, carrying out pre-drying, exposure, development and post-drying on the PCB after the two times of spraying; wherein the step S200 and the step S300 are carried out in a constant-temperature and constant-humidity dust-free environment, and the spraying parameters meet the conditions that the low-viscosity flow velocity of the printing ink is 27-33 s, the high-viscosity flow velocity of the printing ink is 50-56 s, the atomization rate of the spray gun in the step S200 is 500-600 per thousand, and the atomization rate of the spray gun in the step S300 is 400-500 per thousand.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of circuit board processing, in particular to a PCB solder mask no-silicon ink spraying method and equipment. BACKGROUND

[0002] In the PCB solder mask process, the traditional method usually uses silk screen ink to make the solder mask layer. However, the traditional silk screen ink contains silicon elements, which causes serious problems in the subsequent three-proofing paint coating process. Due to the presence of silicon elements, the three-proofing paint will shrink during coating, resulting in poor bonding between the solder mask layer and the three-proofing paint, which in turn affects the overall protection performance of the PCB board, causes customer quality complaints, and brings economic losses and reputation damage to the production enterprise.

[0003] To solve the above problems, the industry tries to switch to no-silicon ink. However, in actual application process, the existing process exposes two major defects: Cross-contamination risk: when switching from silicon-containing ink to no-silicon ink, the silk screen tool and pipeline equipment need to be thoroughly cleaned. However, due to the difficulty of cleaning, it is difficult to completely remove the residual silicon oil. These residual silicon oils will contaminate the subsequent use of no-silicon ink, affecting the performance of no-silicon ink and failing to achieve the expected solder mask effect.

[0004] Poor solder mask uniformity: the traditional manual silk screen method is difficult to accurately control the thickness of the ink during operation, and is prone to uneven ink thickness. Inconsistent ink thickness will cause star point copper exposure defects in the subsequent developing process, affecting the electrical performance and reliability of the PCB board.

[0005] To improve the problem of solder mask uniformity, the industry has tried to use spraying process. However, due to the lack of supporting cleaning control system and precise process parameters, the spraying process has new problems in application. On the one hand, the ink mixing life is short, which affects the solder mask quality; on the other hand, the spraying thickness is extremely large (> 5 μm), which cannot meet the needs of high-precision PCB manufacturing, limiting the application of PCB board in high-end electronic field. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a PCB solder mask no-silicon ink spraying method, which optimizes the spraying process flow, strictly controls the spraying environment and parameters, solves the cross-contamination risk and poor solder mask uniformity problems existing in the traditional process, improves the PCB solder mask quality, and meets the needs of high-precision PCB manufacturing.

[0007] The present application also proposes a CB solder mask no-silicon ink spraying equipment for applying the PCB solder mask no-silicon ink spraying method as described above.

[0008] The PCB solder mask non-silicon ink spraying method according to the first aspect of the present application comprises the following steps: S100, pre-treating a PCB board after plugging; S200, cleaning a spraying device with a diluent once, and spraying a first surface of the pre-treated PCB board with non-silicon solder mask ink; S300, cleaning the spraying device with the diluent again, and spraying a second surface of the PCB board with non-silicon solder mask ink; S400, pre-baking, exposing, developing and post-baking the PCB board after the two times of spraying; wherein, the steps S200 and S300 are performed in a constant-temperature and constant-humidity dust-free environment, and the spraying parameters meet: ink low viscosity flow rate 27-33 s, high viscosity flow rate 50-56 s, and the spraying gun atomization rate in the step S200 is 500-600 ‰, and the spraying gun atomization rate in the step S300 is 400-500 ‰.

[0009] The PCB solder mask non-silicon ink spraying method according to the first aspect of the present application comprises the following steps: S100, pre-treating a PCB board after plugging; S200, cleaning a spraying device with a diluent once, and spraying a first surface of the pre-treated PCB board with non-silicon solder mask ink; S300, cleaning the spraying device with the diluent again, and spraying a second surface of the PCB board with non-silicon solder mask ink; S400, pre-baking, exposing, developing and post-baking the PCB board after the two times of spraying; wherein, the steps S200 and S300 are performed in a constant-temperature and constant-humidity dust-free environment, and the spraying parameters meet: ink low viscosity flow rate 27-33 s, high viscosity flow rate 50-56 s, and the spraying gun atomization rate in the step S200 is 500-600 ‰, and the spraying gun atomization rate in the step S300 is 400-500 ‰.

[0010] According to some embodiments of the first aspect of the present application, in the steps S200 and S300, the environmental temperature is 19-23℃, and the humidity is 40-60%.

[0011] According to some embodiments of the first aspect of the present application, in the steps S200 and S300, the spraying speed is set to 3000-5000 mm / min, and the spraying wet film thickness is 60-90 μm.

[0012] According to some embodiments of the first aspect of the present application, in steps S200 and S300, the air pressure parameters for spraying satisfy: the gun pressure, the atomization pressure, the fan pressure, the air pump pressure and the ink pressure are all controlled within 4-7 bar.

[0013] According to some embodiments of the first aspect of the present application, after step S300, the following steps are further included: S310: performing trace test on the PCB board after spraying on both sides; Specifically, the following steps are included: uniformly taking 9 points on the PCB board to measure the oil thickness, and the oil thickness range is required to be ≤5 μm and the average thickness range of the ink on the front and back sides is required to be ≤5 μm.

[0014] According to some embodiments of the first aspect of the present application, in step S310, if the oil thickness range is >5 μm, the following actions are automatically triggered: S311: switching to a backup high-viscosity nozzle; S312: measuring the oil thickness distribution of 25 points of the same batch of PCB boards.

[0015] According to some embodiments of the first aspect of the present application, in steps S200 and S300, before spraying, the silicon-free solder mask ink is mixed and the viscosity is detected, and when the viscosity detection value is out of the range of 27-33 s for low-viscosity flow rate or 50-56 s for high-viscosity flow rate, the ink is automatically determined to be invalid and the use is stopped.

[0016] According to some embodiments of the first aspect of the present application, in steps S200 and S300, the complete cleaning of the spraying equipment with the diluent needs to satisfy: the diluent injection amount is 3-5 times of the pipeline volume, and the residual ink concentration in the pipeline after cleaning is ≤0.1%.

[0017] The PCB solder mask silicon-free ink spraying equipment according to the second aspect of the embodiments of the present application is used for the PCB solder mask silicon-free ink spraying method as described in any of the above, and includes a constant temperature and humidity module, an ink supply module, a spraying mechanism, a cleaning module and a detection module, wherein the constant temperature and humidity module is used to maintain the ambient temperature at 19-23℃ and the humidity at 40-60%; the ink supply module includes an oil storage tank and a diluent tank, and the oil storage tank and the diluent tank are both connected to the spraying pipeline through an automatic switching valve; the spraying mechanism at least includes a first spray gun and a second spray gun, and both are connected to the output end of the spraying pipeline and are respectively used for front and back spraying of the PCB board; the cleaning module is used to inject diluent into the spraying pipeline for cleaning when switching the spraying surface; and the detection module includes a thickness gauge, which is used to automatically scan at least 9 detection points on the PCB board after spraying and calculate the oil thickness range.

[0018] According to the PCB solder mask non-silicone ink spraying device provided by the embodiment of the present application, the following beneficial effects are achieved: the spraying device integrates a constant temperature and humidity module, an ink supply module, a spraying mechanism, a cleaning module and a detection module, and realizes automation and accurate control of the spraying process. The constant temperature and humidity module provides stable environmental conditions for spraying, ensuring stable performance of the ink; the automatic switching valve of the ink supply module facilitates switching between the use of ink and diluent; the double-spraying gun design improves spraying efficiency; the cleaning module effectively avoids cross contamination; the thickness gauge of the detection module can monitor the spraying quality in real time and timely find problems of uneven thickness. The modules work cooperatively, improving the spraying quality and production efficiency and meeting the needs of high-precision PCB manufacturing.

[0019] According to some embodiments of the second aspect of the present application, the detection module further comprises a viscosity flow rate detector arranged at the oil outlet end of the first spraying gun and the second spraying gun, for monitoring the viscosity of the ink in real time.

[0020] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0021] The present application will be further described below in conjunction with the accompanying drawings and embodiments, in which: Figure 1 A flowchart of the PCB solder mask non-silicone ink spraying method according to the embodiment of the present application is shown in FIG. 2. Figure 2 A flowchart of the trace test of the PCB solder mask non-silicone ink spraying method according to the embodiment of the present application is shown in FIG. 3. Figure 3 A schematic diagram of the PCB solder mask non-silicone ink spraying device according to the embodiment of the present application is shown in FIG. 4.

[0022] Reference signs: constant temperature and humidity module 100; ink supply module 200; ink storage tank 210; diluent tank 220; spraying module 300; first spraying gun 310; second spraying gun 320; cleaning module 400; detection module 500; thickness gauge 510; viscosity flow rate detector 520; pipeline 600. DETAILED DESCRIPTION

[0023] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, in which the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limiting the present application.

[0024] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, front, back, left, right and the like, is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0025] In the description of the present application, one or more is understood as one or more, more than two is understood as more than two, greater than, less than, more than, etc. are understood as not including the number, above, below, etc. are understood as including the number. If the first, second is described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0026] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting and the like should be broadly understood, and those skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution. In the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the description of the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner. In the description of the present application, the description of the terms "one embodiment", "some embodiments", "illustrative embodiment", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the description of the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0027] Referring to Figure 1 , the present application provides a PCB solder mask silicon-free ink spraying method, specifically comprising the following steps: S100: pretreating the PCB after the hole is plugged; S200: cleaning the spraying equipment with a diluent once, and spraying the first surface of the pretreated PCB with silicon-free solder mask ink; S300: the spraying equipment is cleaned twice with a diluent, and the second surface of the PCB is sprayed with a silicon-free solder resist ink; S400: the PCB after the two times of spraying is pre-baked, exposed, developed, and post-baked.

[0028] In specific embodiments, the purpose of the pre-treatment in step S100 is to remove impurities and oxides on the surface of the PCB after hole milling, to improve the cleanliness and roughness of the surface, and to enhance the adhesion of the ink to the surface. The specific method of pre-treatment can include conventional steps such as pickling, alkaline cleaning, washing, and drying, and appropriate adjustments can be made according to the material and surface state of the PCB.

[0029] Step S200 is performed in a constant temperature and humidity dust-free environment after the spraying equipment is cleaned once with a diluent, to avoid the influence of external environmental factors on the spraying quality. The constant temperature and humidity environment can ensure the stability of the viscosity and flowability of the ink, and the dust-free environment can prevent dust and other impurities from adhering to the surface of the PCB, affecting the quality of the solder resist layer. At the same time, the spraying parameters need to meet: low viscosity flow rate 27-33 s, high viscosity flow rate 50-56 s, and spray gun atomization rate 500-600 ‰. Suitable ink viscosity and spray gun atomization rate can ensure that the ink is uniformly sprayed on the first surface of the PCB, forming a solder resist layer with uniform thickness.

[0030] Step S300 uses a diluent to clean the spraying equipment twice, and then uses a silicon-free solder resist ink to spray the second surface of the PCB. After the first surface is sprayed, the spraying equipment is thoroughly cleaned with a diluent in a timely manner, which can effectively prevent ink residue from contaminating subsequent spraying and prevent cross-contamination. The second surface is also sprayed in a constant temperature and humidity dust-free environment, and the low viscosity flow rate and high viscosity flow rate of the ink in the spraying parameters are the same as those of the first surface, but the spray gun atomization rate is 400-500 ‰. Adjusting the spray gun atomization rate of the second surface can further optimize the spraying effect and ensure the quality consistency of the solder resist layers on both surfaces.

[0031] Optionally, the second cleaning in step S300 can be cancelled to improve the spraying efficiency.

[0032] Finally, step S400 pre-bakes, exposes, develops, and post-bakes the PCB after the two times of spraying. The purpose of pre-baking is to remove the solvent in the ink and make the ink preliminary solidify; the exposure process uses ultraviolet radiation to cause a chemical reaction of the photosensitive material in the ink, forming a latent image; development is to dissolve and remove the unexposed ink, exposing the pads and other parts that need to be soldered; post-baking further solidifies the ink, improving the hardness and chemical corrosion resistance of the solder resist layer.

[0033] It can be understood that after the first surface of the PCB is sprayed, the spraying equipment is thoroughly cleaned with a diluent, and then the second surface is sprayed. This operation mode can effectively remove the residual ink in the equipment, prevent cross contamination between the silicon-containing ink (if used before) or different batches of silicon-free ink, ensure the purity and performance stability of the silicon-free solder resist ink, and thus improve the solder resist quality. By strictly controlling the spraying environment to be a constant temperature and humidity dust-free environment, and accurately setting the spraying parameters, including the low viscosity flow rate, the high viscosity flow rate, and the spray gun atomization rate, the silicon-free solder resist ink can be uniformly sprayed on both surfaces of the PCB. Compared with the traditional manual silk screen printing method, the problem of uneven thickness is effectively avoided, the generation of star point copper exposure defects is reduced, and the electrical performance and reliability of the PCB are improved. The optimized spraying process of the present application effectively controls the spraying thickness range, which can meet the strict requirements of high-precision PCB manufacturing on the thickness of the solder resist layer. At the same time, the reasonable process flow and parameter setting prolong the mixing life of the ink, ensure the stability of the ink performance, and are conducive to improving the production efficiency and consistency of product quality. Since the problems of three-proofing paint coating shrinkage caused by silicon-containing ink in the traditional process and the process defects in the application process of silicon-free ink are solved, the PCB solder resist silicon-free ink spraying method provided by the present application can significantly improve the overall quality of the PCB.

[0034] In some applications, the PCB after the hole is put into the acid washing tank, the alkali washing tank in turn for cleaning, remove the impurities and oxides on the board surface, and then washed with water, finally put into the drying oven at 80℃ for 30 minutes, so that the board surface is completely dry. The dried PCB is placed in a constant temperature and humidity dust-free spraying room. Selecting a silicon-free solder resist ink, the low viscosity flow rate of the ink is measured by a viscometer to be 30s, and the high viscosity flow rate is 53s. The spray gun atomization rate is set to 550‰, and the first surface of the PCB is sprayed to ensure uniform coverage of the ink on the board surface. After the first surface is sprayed, the spraying equipment is immediately thoroughly cleaned with a special diluent, including the spray gun, pipeline and other parts, to ensure no ink residue. The cleaned equipment is reinstalled, and the constant temperature and humidity dust-free environment parameters are confirmed again. The low viscosity flow rate of the ink is maintained at 30s, the high viscosity flow rate is 53s, the spray gun atomization rate is adjusted to 450‰, and the second surface of the PCB is sprayed. Post-processing: the sprayed PCB is placed in a pre-drying oven at 75℃ for 20 minutes; then exposed to an exposure energy of 300mJ / cm²; then the PCB is placed in a developing solution for developing for 60 seconds; finally, the developed PCB is placed in a post-drying oven at 150℃ for 60 minutes to completely cure the solder resist layer.

[0035] In other applications, the PCB after the hole is plugged with plasma cleaning method for pretreatment, remove the board organic matter and micro-particle pollutants, and then drying treatment, drying temperature is 70 °C, time is 40 minutes. In a constant temperature and humidity dust-free spray room, select no silicon solder mask ink, measure the ink low viscosity flow rate is 28 s, high viscosity flow rate is 52 s. Set the spray gun atomization rate is 520 ‰, the first side of the PCB is sprayed. After spraying the first side, use the diluent matched with the ink to circulate the spray equipment, until the washing liquid is clear and colorless, to ensure that the equipment is clean. Keep the dust-free environment parameters unchanged, the ink low viscosity flow rate is 28 s, the high viscosity flow rate is 52 s, the spray gun atomization rate is adjusted to 420 ‰, the second side of the PCB is sprayed. According to the pre-baking (70 °C, 25 minutes), exposure (exposure energy 280 mJ / cm²), development (development time 55 seconds), post-baking (145 °C, 70 minutes) in order to post-processing of PCB, complete the production of solder mask layer.

[0036] Further, when performing the spraying operation in step S200 and step S300, the PCB is placed in a specially designed constant temperature and humidity spray room. Through the air conditioning system and humidification / dehumidification equipment in the room, the environmental temperature is accurately controlled in the range of 19 - 23 °C, and the humidity is in the range of 40 - 60%. For example, when the environmental temperature is lower than 19 °C, the air conditioning system starts the heating function to raise the temperature; when the temperature is higher than 23 °C, the cooling function is started to reduce the temperature. For humidity control, if the humidity is lower than 40%, the humidification equipment works to increase the humidity; if the humidity is higher than 60%, the dehumidification equipment starts to reduce the humidity. Under stable environmental conditions, the spraying operation of the no silicon solder mask ink is carried out according to the coating parameters and process. Accurate control of the environmental temperature and humidity in the range of 19 - 23 °C and 40 - 60% can ensure the stability of the viscosity and fluidity of the no silicon solder mask ink. Too high temperature will reduce the viscosity of the ink and increase the fluidity, which may cause the ink to splash during spraying, affecting the uniformity of spraying; too low temperature will increase the viscosity of the ink and reduce the fluidity, which is easy to cause the spray gun to be blocked. Reasonable control of humidity can avoid the ink from absorbing too much water or drying too fast during spraying, so as to ensure the adhesion of the ink to the PCB surface, improve the quality and stability of the solder mask layer, and reduce the spraying defects caused by environmental factors.

[0037] In the spraying process of step S200 and step S300, a spraying device equipped with a precise speed control system is used. By adjusting the control panel of the device, the spraying speed is set in the range of 3000-5000 mm / min. At the same time, according to the characteristics of the used non-silicon solder resist ink and the requirements of the PCB board, the spraying device is adjusted to make the wet film thickness reach 60-90 μm. For example, for some high-precision PCB boards with higher requirements for the thickness of the solder resist layer, the spraying speed can be set to 3500 mm / min and the wet film thickness can be set to 80 μm. In the spraying process, the spraying speed and the wet film thickness are monitored in real time by the sensors of the device to ensure that they are stable within the set range. Setting appropriate spraying speed and wet film thickness can further improve the uniformity and quality of the solder resist layer. Too fast spraying speed may cause the ink to fail to uniformly cover the board surface, resulting in missed coating or insufficient thickness; too slow spraying speed will increase the production cycle and reduce the production efficiency, and may also cause ink accumulation, making the wet film thickness exceed the required range. Appropriate wet film thickness is the key to ensure the performance of the solder resist layer, and too thin may not effectively block soldering and prevent short circuit, and too thick may cause difficulties in subsequent developing process, affecting the precision of the solder resist layer. Therefore, precise control of the spraying speed and the wet film thickness can meet the needs of high-precision PCB manufacturing and improve the product qualification rate.

[0038] Before the spraying operation of step S200 and step S300, the air pressure system of the spraying device is debugged and set. Professional air pressure adjusting device is used to accurately control the gun pressure, atomization pressure, fan pressure, air pump pressure and ink pressure in the range of 4-7 bar. For example, by adjusting the air pressure adjusting valve, the gun pressure is stabilized at 5 bar and the atomization pressure is stabilized at 6 bar, etc. In the spraying process, the pressure parameters are monitored in real time by the air pressure sensor, and if the pressure deviates from the set range, the adjusting device is adjusted in time to ensure the stability of the air pressure in the spraying process. Precise control of the spraying air pressure parameters is crucial to ensure the spraying quality. The gun pressure affects the initial spraying force of the ink, and appropriate gun pressure can make the ink smoothly spray out of the spray gun; the atomization pressure determines the atomization effect of the ink, and good atomization effect can make the ink uniformly dispersed on the PCB board surface; the fan pressure controls the shape and range of the ink spraying, ensuring the accuracy of the spraying area; the air pump pressure provides power support for the whole air pressure system; the ink pressure affects the stability of the ink supply. Controlling each air pressure parameter in the range of 4-7 bar can make the ink uniformly sprayed on the PCB board in the best atomization state and spraying force, improve the uniformity and quality of the solder resist layer, and reduce the spraying defects.

[0039] Reference Figure 2It should be noted that after the two-side spraying in step S300 is completed, the PCB board is placed on a special trace spraying test platform. A high-precision thickness gauge is used to measure the oil thickness at 9 evenly selected points on the PCB board surface. For example, the measurement points can be selected in a 3x3 matrix manner to ensure that the measurement points can comprehensively cover different areas of the board surface. After the measurement is completed, the oil thickness range and the average thickness range of the ink on the front and back surfaces are calculated. The oil thickness range is required to be ≤5 μm and the average thickness range of the ink on the front and back surfaces is required to be ≤5 μm, if the measurement result meets the requirements, then the subsequent process is entered; if it does not meet the requirements, then the spraying in step S200 is re-entered, and if it fails again, it is NG processed. By performing trace spraying test on the PCB board after two-side spraying, 9 points are measured for oil thickness on the board surface and strict range requirements are set, which can timely find the thickness unevenness problem existing in the spraying process. The control of the oil thickness range and the average thickness range of the ink on the front and back surfaces can effectively ensure the thickness consistency of the solder resist layer on the entire PCB board surface, avoiding the electrical performance difference and reliability problem caused by uneven thickness. This is particularly important for high-precision PCB manufacturing, which can improve the quality and stability of the product and meet the application requirements of high-end electronic products.

[0040] Referring to Figure 2 Further, in the trace spraying test of step S310, if the oil thickness range is detected to be >5 μm, the equipment automatically triggers the following actions: first, the system automatically controls the spraying equipment to switch to a standby high-stick nozzle. The standby high-stick nozzle has different atomization characteristics and can better adapt to the requirements of ink spraying and improve the uniformity of ink distribution. After switching the nozzle, additional measurements are performed on the PCB boards of the same batch, and 16 additional points (a total of 25 points) are selected for oil thickness distribution measurement based on the original 9 points. By measuring more points, the oil thickness distribution of the PCB boards of the batch can be more comprehensively understood, potential problem areas can be timely discovered, and appropriate adjustment measures such as adjusting the spraying parameters can be taken to ensure that the quality of the PCB boards sprayed subsequently meets the requirements. When the oil thickness range exceeds the specified range, automatically switching to a standby high-stick nozzle can quickly adjust the spraying equipment, improve the ink spraying effect, and reduce the thickness unevenness caused by nozzle problems. Measuring the oil thickness distribution of 25 points can more accurately grasp the oil thickness of the entire batch of PCB boards and provide more detailed data support for subsequent production adjustment. This automated processing method can improve production efficiency, reduce manual intervention, while ensuring the consistency and stability of product quality, and reducing the rate of defective products.

[0041] It should be noted that before the spraying in steps S200 and S300, the silicon-free solder resist ink is poured into a special mixing device for thorough mixing. During the mixing process, the viscosity of the ink is monitored in real time using a visco-flow rate detector. The visco-flow rate detector detects the viscosity of the ink at set time intervals (e.g., every 5 minutes) and compares the detected value to the low visco-flow rate range of 27-33 s and the high visco-flow rate range of 50-56 s. When the detected value exceeds this range, the control system of the device automatically determines that the ink has failed and sends an alarm signal, stopping the operation of the spraying equipment to prevent the use of failed ink for spraying, which affects the quality of the solder resist layer. Mixing and detecting the viscosity of the silicon-free solder resist ink before spraying ensures that the performance of the ink used meets the requirements. The viscosity of the ink is one of the important factors affecting the quality of the spraying. Inappropriate viscosity can cause uneven spraying, ink flow or clogging of the spray gun, etc. By monitoring the viscosity in real time and automatically determining the failure of the ink and stopping its use when it exceeds the range, quality problems caused by the use of unqualified ink can be effectively avoided, the reliability and stability of the solder resist layer are improved, the number of defective products and rework is reduced, and the production cost is reduced.

[0042] In steps S200 and S300, when the spraying equipment needs to be cleaned, the injection amount of the diluent is accurately controlled by the control system of the equipment. According to the volume of the pipeline, the volume of the diluent to be injected is calculated to ensure that the injection amount of the diluent is 3-5 times the volume of the pipeline. For example, if the volume of the pipeline is 1 L, 300-500 ml of diluent is injected. After injecting the diluent, the diluent is circulated in the pipeline using the circulating system in the equipment to clean the residual ink. After cleaning is completed, a professional ink concentration detector is used to detect the concentration of the residual ink in the pipeline to ensure that the concentration of the residual ink is ≤0.1%. If the concentration exceeds this value, continue to inject the diluent for cleaning until the requirements are met. Accurate control of the injection amount of the diluent to be 3-5 times the volume of the pipeline can ensure that there is enough diluent to thoroughly clean the ink in the pipeline, effectively removing residual ink and avoiding cross-contamination. At the same time, controlling the concentration of the residual ink in the pipeline to be within the strict range of ≤0.1% can further ensure the purity of the silicon-free ink and prevent the residual ink from affecting the performance of the subsequent silicon-free ink for spraying. This helps to improve the quality of the solder resist layer, reduce quality problems caused by cross-contamination, and improve the reliability and stability of the product.

[0043] Reference Figure 3The application further provides a PCB solder mask silicon-free ink spraying device which is composed of multiple modules. The constant temperature and humidity module 100 precisely controls the environmental temperature in the spraying chamber to be 19-23℃ and the humidity to be 40-60% through air conditioning systems, humidifiers and dehumidifiers. In the ink supply module 200, the oil storage tank 210 stores silicon-free solder mask ink, and the diluent tank 220 stores diluent. Both of them are connected with the spraying pipeline 600 through automatic switching valves. When the ink is needed, the automatic switching valve opens the channel of the oil storage tank 210; when the equipment is cleaned, the automatic switching valve switches to the channel of the diluent tank 220. The first spraying gun 310 and the second spraying gun 320 of the spraying mechanism are respectively connected with the output end of the spraying pipeline 600, and can independently control the spraying of the front and back surfaces of the PCB. The cleaning module 400 injects diluent into the spraying pipeline 600 through the control system to clean when switching the spraying surface. The thickness gauge 510 of the detection module 500 is installed on the workbench of the spraying equipment, and automatically scans at least 9 detection points on the surface of the PCB after spraying and transmits the measurement data to the control system for calculation to obtain the thickness range.

[0044] It can be understood that the spraying device integrates the constant temperature and humidity module 100, the ink supply module 200, the spraying mechanism, the cleaning module 400 and the detection module 500, realizes the automation and precise control of the spraying process. The constant temperature and humidity module 100 provides stable environmental conditions for spraying, ensures the stable performance of the ink; the automatic switching valve design of the ink supply module 200 facilitates the switching of the ink and the diluent; the double spraying gun design improves the spraying efficiency; the cleaning module 400 effectively avoids cross contamination; the thickness gauge 510 of the detection module 500 can monitor the spraying quality in real time and find the uneven thickness problem in time. The modules work together to improve the spraying quality and production efficiency, and meet the needs of high-precision PCB manufacturing.

[0045] Further, with reference to Figure 3In some embodiments, the detection module 500 additionally includes a viscosity flow rate detector 520. The viscosity flow rate detector 520 is arranged at the oil outlet end of the first spray gun 310 and the second spray gun 320, respectively, so that it can be in real-time contact with the sprayed ink. The viscosity flow rate detector 520 monitors the viscosity of the ink in real time through the built-in sensor and transmits the monitoring data to the control system of the equipment. The control system judges the viscosity of the ink according to the preset viscosity range, and if the viscosity exceeds the range, an alarm signal is sent to prompt the operator to adjust or replace the ink. The addition of the viscosity flow rate detector 520 in the detection module 500 can monitor the viscosity of the ink in real time and timely detect the change of the viscosity of the ink. The viscosity of the ink is one of the key factors affecting the quality of spraying, and abnormal changes in the viscosity may cause uneven spraying, ink flow or clogging of the spray gun, etc. By monitoring the viscosity in real time and sending an alarm when it exceeds the range, the operator can take timely measures such as adjusting the ink formula, replacing the ink, etc., to ensure the stability of the ink performance, thereby improving the quality and stability of the solder resist layer and reducing quality defects and production accidents caused by the viscosity problem of the ink.

[0046] The embodiments of the present application are described in detail above with reference to the drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the scope of knowledge possessed by those skilled in the art without departing from the purpose of the present application.

Claims

1. A method for spraying silicone-free solder resist ink onto PCBs, characterized in that, Includes the following steps: S100: Pre-processing of the PCB board after hole plugging; S200: Clean the spraying equipment once with a thinner, and spray the first side of the pretreated PCB board with a silicone-free solder resist ink; S300: The spraying equipment is cleaned twice with a thinner, and the second side of the PCB board is sprayed with a silicone-free solder resist ink; S400: Pre-baking, exposure, development, and post-baking are performed on the PCB board after two spraying processes; Steps S200 and S300 are carried out in a dust-free environment with constant temperature and humidity, and the spraying parameters meet the following requirements: low viscosity ink flow rate 27-33s, high viscosity ink flow rate 50-56s, and the atomization rate of the spray gun in step S200 is 500-600‰, and the atomization rate of the spray gun in step S300 is 400-500‰.

2. The PCB solder resist silicone-free ink spraying method according to claim 1, characterized in that, In steps S200 and S300, the ambient temperature is 19-23℃ and the humidity is 40-60%.

3. The PCB solder resist silicone-free ink spraying method according to claim 2, characterized in that, In steps S200 and S300, the spraying speed is set to 3000-5000 mm / min, and the wet film thickness is 60-90 μm.

4. The PCB solder resist silicone-free ink spraying method according to claim 3, characterized in that, In steps S200 and S300, the spraying air pressure parameters are as follows: the gun opening pressure, atomization pressure, fan-shaped pressure, air pump pressure and ink pressure are all controlled at 4-7 bar.

5. The PCB solder resist silicone-free ink spraying method according to claim 1, characterized in that, Following step S300, the following steps are also included: S310: Perform a spray mark test on the PCB board after spraying on both sides; Specifically, the steps include: uniformly taking 9 points on the PCB board surface to measure the ink thickness, requiring the ink thickness range to be ≤5μm and the average ink thickness range on the front and back sides to be ≤5μm.

6. The PCB solder resist silicone-free ink spraying method according to claim 5, characterized in that, In step S310, if the oil thickness difference is >5μm, the following action will be automatically triggered: S311: Switch to the backup high-viscosity nozzle; S312: Add 25 points to measure the oil thickness distribution of the PCB boards in the same batch.

7. The PCB solder resist silicone-free ink spraying method according to claim 1, characterized in that, In steps S200 and S300, the silicone-free solder resist ink is mixed and its viscosity is tested before spraying. When the viscosity value exceeds the range of 27-33s for low viscosity flow rate or 50-56s for high viscosity flow rate, the ink is automatically determined to be ineffective and its use is stopped.

8. The PCB solder resist silicone-free ink spraying method according to claim 1, characterized in that, In steps S200 and S300, the thorough cleaning of the spraying equipment with diluent must meet the following requirements: the amount of diluent injected is 3-5 times the volume of the pipe, and the concentration of residual ink in the pipe after cleaning is ≤0.1%.

9. A PCB solder resist silicone-free ink spraying device, used for applying the PCB solder resist silicone-free ink spraying method as described in any one of claims 1 to 8, characterized in that, include: The system includes a constant temperature and humidity module, an ink supply module, a spraying mechanism, a cleaning module, and a detection module. The constant temperature and humidity module maintains an ambient temperature of 19-23°C and a humidity of 40-60%. The ink supply module includes an oil storage tank and a thinner tank, both connected to the spraying pipeline via an automatic switching valve. The spraying mechanism includes at least a first spray gun and a second spray gun, both connected to the output end of the spraying pipeline, used for spraying the front and back sides of the PCB board, respectively. The cleaning module injects thinner into the spraying pipeline for cleaning when switching spraying surfaces. The detection module includes a thickness gauge, which automatically scans at least nine detection points on the PCB board surface after spraying and calculates the ink thickness range.

10. The PCB solder resist silicone-free ink spraying equipment according to claim 9, characterized in that, The detection module also includes a viscosity flow rate detector, which is installed at the oil outlet of the first spray gun and the second spray gun to monitor the ink viscosity in real time.

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