PCB resin plug hole processing technology

Abstract

The application relates to the technical field of PCB processing, in particular to a PCB resin hole plugging processing technology, which comprises the following steps: S1, completely cleaning a PCB to be subjected to hole plugging by using a chemical cleaning agent; S2, selecting low-viscosity resin according to the application requirement of the PCB; S3, performing one-time resin filling, and performing high-frequency vibration on the via hole of the PCB during the filling process; S4, curing the low-viscosity resin plugged into the via hole of the PCB; and S5, performing two-time resin filling. The two-time resin hole plugging mode can prevent the problems of holes in the resin-plugged holes being hollow and having bubbles due to the fact that the through holes are deep, the viscosity is large, the resin flowability is influenced, and the resin cannot sufficiently flow and fill the PCB via hole, and can prevent the resin from overflowing when the PCB resin hole plugging is performed on a relatively thin PCB.

Description

Technical Field

[0001] This invention relates to the field of PCB processing technology, and in particular to a PCB resin via plugging process. Background Technology

[0002] As electronic products evolve towards miniaturization, multifunctionality, and high reliability, the design and manufacturing of printed circuit boards (PCBs) face increasingly stringent requirements. PCB resin via plugging, as a key process technology, plays a crucial role in the manufacturing of high-end PCBs such as multilayer boards and high-density interconnect (HDI) boards. In some high-frequency, high-speed PCB designs, special treatment is required for vias to reduce signal reflection and crosstalk. Resin plugging creates a relatively flat dielectric structure between the vias and surrounding traces, which is beneficial for stable signal transmission and reduces the impact of signal integrity issues. For PCBs that need to withstand harsh environmental conditions (such as high temperature, high humidity, and strong vibration), resin plugging prevents moisture, dust, and other impurities from entering the PCB through the vias, avoiding short circuits, corrosion, and other reliability risks, thus enhancing the long-term stability of the PCB. When PCBs use double-sided or multilayer surface mount components, the flat PCB surface after plugging promotes uniform solder paste printing, reduces insufficient or excessive solder paste due to via depressions, improves soldering quality, reduces soldering defect rates, and ensures high assembly yield of electronic devices.

[0003] When resin plugging is applied to thinner PCBs, resin overflow is likely to occur during subsequent lamination. Conversely, when resin plugging is applied to thicker PCBs, the via depth and resin flow characteristics can lead to voids and air bubbles within the vias. This project aims to develop a PCB resin plugging process to address these issues. Summary of the Invention

[0004] In view of at least one of the above technical problems, the present invention provides a PCB resin via plugging process, which solves the problem by adopting the following technical solution.

[0005] According to one aspect of the present invention, a PCB resin via plugging process is provided, comprising:

[0006] S1, use chemical cleaning agents to thoroughly clean the PCB to be plugged, remove contaminants inside the vias, and form a micro-etched surface on the inner wall of the vias;

[0007] S2, select a low viscosity resin according to the application requirements of the PCB;

[0008] S3, perform one resin filling. Use a diagonal filling method to fill the resin in two stages to print the low viscosity resin onto the PCB through the stencil. The low viscosity resin flows into the via through the opening on the stencil. During the filling process, the via on the PCB is subjected to high-frequency vibration.

[0009] During the two glue application processes, the PCB is tilted in opposite directions to facilitate the two glue application processes.

[0010] S4, based on the curing characteristics of low-viscosity resin, the low-viscosity resin inserted into the PCB via is cured;

[0011] S5, perform secondary resin filling, use diagonal filling method to fill the resin on the PCB in two stages, print the resin on the PCB through the stencil, let the resin flow into the via through the opening on the stencil, and fill the end of the via with resin.

[0012] The thickness of the adhesive filler is equal to the sum of the copper plating thickness in the subsequent process and the thickness to be ground.

[0013] S6, the resin filled with secondary resin is cured using the method in S4;

[0014] S7, Demolding and smoothing: Use grinding to smooth the cured resin end face;

[0015] S8, thicken the copper plating on the via;

[0016] S9, a solder mask is applied to the PCB, in which the resin-filled holes are not exposed, and the solder mask layer is flush with the resin surface after the first solder mask is formed.

[0017] S10, secondary solder mask, includes exposure of the resin-filled vias to protect the resin and thickened copper plating at the resin-filled vias.

[0018] The present invention is further configured such that, during the process of thoroughly cleaning the PCB to be plugged with a chemical cleaning agent, ultrasonic cleaning is simultaneously used as an auxiliary process.

[0019] The present invention is further configured such that the viscosity range of the low viscosity resin is 100-1000 cps.

[0020] The present invention is further configured such that, during the process of printing low-viscosity resin onto the PCB through a stencil using a diagonal glue-filling method in two stages, the tilt angle of the PCB is 30°-120°.

[0021] The present invention is further configured such that the high-frequency vibration of the PCB vias during the filling process is generated by an ultrasonic generator with a frequency of 20-40kHz.

[0022] The present invention is further configured such that the aperture of the stencil used in the secondary resin filling process is smaller than the aperture of the via, and the difference between the aperture of the stencil and the aperture of the via is equal to the thickness of the thickened copper plating.

[0023] The present invention is further configured such that the perforated plate used in the secondary resin filling process has tangential wiping holes for venting during the filling process.

[0024] The present invention is further configured such that the stencils for primary resin filling and secondary resin filling are made using film.

[0025] The present invention is further configured such that the perforated plates for primary resin filling and secondary resin filling are made of aluminum plate.

[0026] The present invention is further configured such that the low viscosity resin inserted into the PCB via is cured by a photocuring method.

[0027] The present invention has the following technical effects:

[0028] This invention uses a two-stage resin plugging method to prevent the formation of voids and air bubbles in the PCB vias due to the high viscosity of the resin caused by the deep vias and its fluidity characteristics. It also prevents resin overflow when plugging thinner PCBs. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a process step diagram of the present invention. Detailed Implementation

[0031] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0032] Example 1

[0033] In this embodiment of the invention, such as Figure 1 As shown, a PCB resin via plugging process is provided, including:

[0034] S1, use chemical cleaning agents to thoroughly clean the PCB to be plugged, remove contaminants inside the vias, and form a micro-etched surface on the inner wall of the vias;

[0035] During the thorough cleaning of the PCB to be plugged using chemical cleaning agents, ultrasonic cleaning is simultaneously employed as an auxiliary process. This combined chemical and ultrasonic cleaning process provides deep cleaning of the drilled PCB. Chemical cleaning uses alkaline or acidic cleaning agents, with the pH value of the alkaline cleaning agent controlled between 8 and 10, and the pH value of the acidic cleaning agent controlled between 2 and 4. This thoroughly removes drill debris, oil, and other impurities that may affect resin adhesion. Furthermore, micro-etching creates a certain degree of roughness on the copper hole wall surface, increasing the contact area between the resin and the hole wall, thereby improving the adhesion between the resin and the hole wall and preventing quality problems such as resin shedding during subsequent use, as well as preventing resin overflow. Ultrasonic cleaning utilizes the powerful impact force generated by cavitation to effectively remove fine contaminants inside the hole, ensuring a highly clean hole wall and providing an ideal adhesion base for subsequent resin filling.

[0036] S2, select a low viscosity resin according to the application requirements of the PCB;

[0037] PCB application requirements include adhesion, insulation, chemical resistance, curing speed, and flexibility. Epoxy resin and acrylic resin can be used, each with different properties. Epoxy resin has good adhesion, insulation, and chemical resistance, making it suitable for PCBs with high reliability requirements. Acrylic resin has a fast curing speed and good flexibility, making it suitable for PCBs with high production efficiency requirements. The resin main agent and curing agent should be mixed evenly according to the specified ratio, with a significant amount of diluent added to adjust the resin viscosity. The mixing process requires strict control of the stirring speed and time to ensure thorough and uniform mixing of all components. Low-speed stirring (e.g., 300-500 rpm) is recommended. To prevent the introduction of excessive air bubbles, the stirring time is 5-10 minutes. The viscosity of the resin directly affects the quality of the plugging. If the resin viscosity is too high, the resin has poor fluidity and is difficult to flow into the hole, which can easily lead to incomplete filling and voids. If the viscosity is too low, the resin is not easy to retain in the hole and will flow out of the hole, causing contamination of the board surface. The viscosity of the resin is adjusted by adding diluents or thickeners, and the ambient temperature and humidity are controlled during the production process to ensure the stability of the resin viscosity. The viscosity range of the low viscosity resin in this invention is 100-1000cps to adapt to thicker PCBs and smaller hole diameters.

[0038] Pre-fabricate the hole plate and drill strip. The hole plates for primary and secondary resin filling in subsequent processes are all made using film.

[0039] For a single resin-filled film, a film with the same hole positions and structure as the PCB board is created. This film is precisely drawn using design software according to the required hole positions and dimensions on the PCB board, and then produced via photoplotting. This provides accurate positioning and shape guidance for subsequent hole-filling operations. The hole-filling film is used in conjunction with drill tape. The drill tape determines the hole positions on the PCB board, while the hole-filling film identifies which holes require resin filling. This combination ensures precise resin filling of the required hole positions during production, avoiding misoperation and unnecessary hole filling, thus guaranteeing production efficiency and product quality.

[0040] For secondary resin-filled film, it is manufactured sequentially with primary resin-filled film in the same drilling process step. First, the secondary resin-filled film with a smaller hole diameter is drilled, then the secondary resin-filled film is removed, and then the primary resin-filled film is drilled. The film with two resin fillings only needs to be positioned once.

[0041] The perforated plate used in the secondary resin filling process has tangential wiping holes for venting during the filling process. The wiping holes are holes set on the plugging aluminum plate that are tangential to the holes on the PCB board. Their main function is to allow the scraper to better scrape the resin into the PCB board holes when it passes the edge of the aluminum plate holes during the resin filling process. When the scraper passes the edge of the wiping hole, the tangential design of the hole helps to expel the gas. The resin will flow more smoothly into the PCB board holes under the pressure of the scraper, which helps to improve the efficiency and quality of plugging and reduce the generation of voids in the holes.

[0042] S3 involves a single resin filling process, employing a diagonal filling method to apply low-viscosity resin to the PCB in two stages. The resin is printed onto the PCB through a perforated stencil, allowing it to flow into the vias. During the filling process, the PCB vias are subjected to high-frequency vibration. The PCB is tilted in opposite directions during the two filling stages to facilitate the process. This diagonal filling method ensures more even resin distribution throughout the vias and effectively removes air from the vias. Simultaneously, the high-frequency ultrasonic vibration causes air bubbles within the resin to burst and escape. In the compression stage, tiny air bubbles are compressed; in the rarefaction stage, these bubbles rapidly expand. When a bubble expands to a certain extent, its internal pressure exceeds the tolerance of the surrounding resin, causing it to burst. This bursting generates localized high temperature and pressure, prompting gas molecules in the resin to escape rapidly, thus achieving the effect of air bubble removal. This ensures that the resin fully and evenly fills the vias, forming a uniform resin layer on the surface, meeting the requirements for subsequent curing and leveling.

[0043] In the process of printing low-viscosity resin onto the PCB through a stencil using a diagonal filling method in two stages, the PCB tilt angle is 30°-120°. The tilt angle of the squeegee is set to better control the amount and effect of resin filling. When the squeegee is tilted at a certain angle, on the one hand, the resin can flow into the hole more smoothly under the push of the squeegee, and on the other hand, the amount of resin flowing into the hole can be controlled by adjusting the angle. If the squeegee angle is too small, the resin will not flow into the hole sufficiently, resulting in incomplete filling; if the angle is too large, too much resin will be squeezed onto the board surface, causing board surface contamination and increasing the difficulty of subsequent processing.

[0044] When the squeegee pushes the resin, the resin molecules are subjected to shear force applied by the squeegee. On an inclined PCB, the resin will tend to flow downward and laterally under the action of gravity. For the resin near the hole opening, due to the squeezing of the squeegee and the fluidity of the resin itself, it will gradually penetrate into the hole. In this process, the resin molecules will continuously adjust their arrangement and position to adapt to the flow requirements. Smaller molecules and low viscosity areas of resin will preferentially fill the tiny gaps and spaces in the hole. As the filling progresses, larger molecules and high viscosity areas of resin will also be squeezed into the hole under continuous pressure, thereby achieving a gradually denser filling process.

[0045] The diagonal movement creates complex flow paths for the resin on the plate surface. The intersection and superposition of these flow paths can break up any localized agglomeration or stasis of the resin, promote overall mixing and uniform distribution of the resin, and ensure that each pore can come into contact with resin with similar properties and flowability.

[0046] In the initial state, the gas inside the via adheres to the via wall or is relatively stationary due to factors such as surface tension. When the squeegee starts operating and the PCB is tilted, the flow of resin will carry the gas along with it. At the interface between resin and gas, due to the viscosity and shear force of the resin, the gas is gradually entrained and stretched into small bubbles. With the continuous flow of resin and the push of the squeegee, these small bubbles will gradually move towards the board surface or via along the flow direction of the resin.

[0047] When the PCB is tilted, the gas is more likely to rise to the board surface or be discharged from the orifice due to the combined effects of buoyancy and resin flow. At the microscopic level, gas molecules continuously diffuse from the high concentration area (inside the orifice) to the low concentration area (the atmospheric environment above the board surface), ultimately achieving effective gas discharge. This ensures that the orifice is fully filled with resin, reducing the adverse effects caused by the presence of gas.

[0048] High-frequency vibration of PCB vias during resin filling is achieved using an ultrasonic generator with a frequency of 20-40kHz. In practical applications, this 20-40kHz frequency range was chosen after extensive experimental and practical verification. Lower frequency ultrasonic waves cannot generate a sufficiently strong cavitation effect to effectively break up air bubbles, while excessively high frequency ultrasonic waves attenuate too quickly during propagation, failing to penetrate deep into the resin and significantly increasing equipment costs. The 20-40kHz frequency range ensures sufficient penetration depth while generating a sufficiently strong cavitation effect, causing air bubbles within the resin to burst and be expelled under vibration. This improves the quality of resin filling, reduces defects in the vias caused by air bubbles, and enhances the reliability and product quality of the PCB resin via filling process.

[0049] The specific operation is as follows: place the PCB on the exhaust backplate of the workbench, with the exhaust holes corresponding to the via positions. Place the primary via-plugging film on the PCB, with the hole positions corresponding. Then, use a screen printing machine to print the prepared resin onto the PCB surface through the stencil, allowing the resin to flow into the vias through the openings on the stencil. When the PCB is tilted to the right (right lower, left higher), the squeegee moves from right to left to plug the vias. When the PCB is tilted to the left (left lower, right higher), the squeegee moves diagonally from left to right to plug the vias.

[0050] The opening size, shape, and thickness of the screen printing stencil are designed according to the via parameters to ensure that the resin can smoothly fill the via and form an appropriate amount of resin layer on the surface, facilitating subsequent curing and smoothing. During the screen printing process, the squeegee pressure, speed, and angle need to be finely adjusted. Excessive squeegee pressure will cause too much resin to be squeezed in, resulting in board surface contamination or difficulty in subsequent sanding. Insufficient pressure will result in insufficient filling. The squeegee pressure should be 5-10 N / cm², the speed 20-30 mm / s, and the angle between 30° and 120°. The 30°-120° range can be adjusted according to the actual situation such as the viscosity of the resin, the size and density of the PCB board holes, etc. For example, a smaller tilt angle can be selected for thinner resin and smaller holes, and a larger tilt angle can be selected for thicker resin and larger holes.

[0051] S4, based on the curing characteristics of low-viscosity resin, the low-viscosity resin inserted into the PCB via is cured; the low-viscosity resin inserted into the PCB via is cured by light curing.

[0052] Based on the curing characteristics of the selected low-viscosity resin, a photocuring method is chosen to cure the resin filling the PCB vias. Ultraviolet (UV) or visible light of a specific wavelength is used for irradiation, and the uniformity of light intensity is controlled within ±10%. This allows the photoinitiator in the resin to efficiently generate free radicals, initiating rapid resin curing. The photocuring process ensures good resin light transmittance and uniform light irradiation.

[0053] If thermosetting is used, place the resin-filled PCB in a constant temperature oven and slowly heat it to the precise temperature range required for resin curing at a rate of 1-3℃ / min according to the preset heating curve. Set the temperature to 150℃-160℃ and strictly control the holding time to 100-120 minutes to ensure that the resin is fully cross-linked and cured, and avoid stress concentration inside the resin caused by excessive heating, which may result in cracks or delamination.

[0054] S5, perform secondary resin filling, use diagonal filling method to fill the resin on the PCB in two stages, print the resin on the PCB through the stencil, let the resin flow into the via through the opening on the stencil, and fill the end of the via with resin.

[0055] The diagonal filling method used during secondary resin filling is primarily to ensure more even resin distribution throughout the holes and to effectively expel air from within the holes. When filling diagonally, the resin flows gradually from the diagonal towards the center, driving air out of the holes and preventing the formation of sealed spaces. If sealed gas exists within the holes, it will expand during subsequent curing, causing voids or bulges on the board surface after filling, affecting product quality. The diagonal filling method effectively avoids these problems. Furthermore, due to excessive diluent added to the resin during curing, the resin undergoes volume shrinkage, causing it to recede from the hole opening into the hole. Applying resin to the ends of the through-holes can compensate for this receding resin.

[0056] The thickness of the filler adhesive is equal to the sum of the thickness of the copper plating in the subsequent process and the thickness to be ground. Considering the copper plating and grinding in the subsequent process, the thickness of the filler adhesive is controlled in advance so that the surface of the copper plating is flush with the surface of the resin.

[0057] In the secondary resin filling process, the aperture of the plate used is smaller than that of the via, and the difference between the aperture of the plate and the aperture of the via is equal to the thickness of the copper plating. By reducing the aperture of the plate, such as by 5 micrometers, the hole wall can be thickened when the copper plating is thickened in the subsequent process, so that the resin can better bond with the via.

[0058] S6, the resin filled with secondary resin is cured using the method in S4;

[0059] S7, Demolding and smoothing: Use grinding to smooth the cured resin end face;

[0060] After curing, the resin forms a protrusion on the PCB surface. After filling the holes, due to surface tension, the resin at the hole opening tends to expand outwards. During the curing process, the resin's fluidity gradually decreases until it completely loses its fluidity. Without external force or special processing, the resin will naturally form a protrusion higher than the board surface at the hole opening. In this process, due to the addition of too much diluent to the resin, the resin will shrink in volume during the curing process, causing the resin to sink from the hole opening into the hole. Therefore, it is necessary to perform a grinding process to restore the board surface to flatness. A grinding machine is used to grind the resin end face to meet the requirements of subsequent solder mask, character creation, and surface mount processes. During the grinding process, the grinding pressure, speed, and cooling method are controlled to prevent the board surface from overheating and deforming or damaging the circuit. The grinding pressure is 2-5 N / cm², the speed is 10-20 m / min, and air cooling is used.

[0061] Removing the film involves removing the stencil used to fill the secondary resin layer, with the aim of restoring the PCB surface to a state suitable for subsequent solder mask processing.

[0062] S8, thicken the copper plating on the vias; the thickness of the thickening corresponds to the reduction in the aperture of the via during secondary resin filling, such as 5 micrometers.

[0063] S9 performs a first solder mask on the PCB, where the resin-filled vias are not exposed to the light. After the first solder mask is formed, the solder mask layer is flush with the resin surface. The purpose of not exposing the vias is to protect the resin at the via filling area. If exposed, it would cause an adverse reaction between the resin and the solder mask ink, affecting the quality of the via filling and subsequent soldering processes. At the same time, not exposing allows the solder mask ink at the via filling area to be removed during the subsequent development process, keeping the via filling area flat and clean, which is beneficial for the subsequent installation and soldering of components.

[0064] S10, secondary solder mask, includes exposure of the resin-filled vias to protect the resin and thickened copper plating at the vias; secondary solder masking of the PCB, including exposure of the filled vias to protect the resin at the filled vias. After the previous resin filling and primary solder masking operations, the filled vias are in an exposed state, so secondary solder masking achieves more comprehensive protection. The secondary solder masking operation is similar to the primary solder masking operation, and is also achieved through processes such as applying solder mask ink, exposure, and development. Through secondary solder masking, the solder masking effect of the PCB board can be further improved, and the reliability and quality of the product can be enhanced.

[0065] The resin plugging device comprises at least the following components:

[0066] The feeding system includes a resin storage tank, conveying pipelines, and a flow control device, which can accurately control the resin supply to ensure a stable and appropriate amount of resin for each plugging operation, avoiding too much or too little resin.

[0067] Coating system: The core components are the doctor blade and doctor blade drive device. The doctor blade can adjust the angle, pressure and stroke. The drive device ensures that the doctor blade moves at a uniform speed and smoothly, so as to achieve uniform coating of resin on the board surface. It also has an automatic doctor blade cleaning function to prevent resin residue from affecting the quality of resin plugging in the next time.

[0068] Worktable and positioning device: The worktable supports the PCB board and has the function of adjusting its tilt angle. Its surface is flat and has a certain anti-stick property to prevent resin from adhering. The positioning device adopts mechanical positioning pins or vision positioning system to accurately fix the position of the PCB board and ensure that the positional accuracy of each hole plugging is within ±0.05mm, which meets the requirements of high-precision PCB manufacturing. The worktable also includes an ultrasonic vibration generator, which is set at the bottom of the worktable and transmits the vibration force to the PCB board through the worktable.

[0069] Example 2

[0070] In this embodiment of the invention, such as Figure 1 As shown, a PCB resin via plugging process is provided, including:

[0071] S1, use chemical cleaning agents to thoroughly clean the PCB to be plugged, remove contaminants inside the vias, and form a micro-etched surface on the inner wall of the vias;

[0072] S2, select a low viscosity resin according to the application requirements of the PCB;

[0073] S3, perform one resin filling. Use a diagonal filling method to fill the resin in two stages to print the low viscosity resin onto the PCB through the stencil. The low viscosity resin flows into the via through the opening on the stencil. During the filling process, the via on the PCB is subjected to high-frequency vibration.

[0074] During the two glue application processes, the PCB is tilted in opposite directions to facilitate the two glue application processes.

[0075] S4, based on the curing characteristics of low-viscosity resin, the low-viscosity resin inserted into the PCB via is cured;

[0076] S5, perform secondary resin filling, use diagonal filling method to fill the resin on the PCB in two stages, print the resin on the PCB through the stencil, let the resin flow into the via through the opening on the stencil, and fill the end of the via with resin.

[0077] The thickness of the adhesive filler is equal to the sum of the copper plating thickness in the subsequent process and the thickness to be ground.

[0078] S6, the resin filled with secondary resin is cured using the method in S4;

[0079] S7, Demolding and smoothing: Use grinding to smooth the cured resin end face;

[0080] Among them, the film removal process involves using a suction cup tool to remove the perforated plate made of aluminum plate, which can be reused for the next resin plugging process.

[0081] S8, thicken the copper plating on the via;

[0082] S9, a solder mask is applied to the PCB, in which the resin-filled holes are not exposed, and the solder mask layer is flush with the resin surface after the first solder mask is formed.

[0083] S10, secondary solder mask, includes exposure of the resin-filled vias to protect the resin and thickened copper plating at the resin-filled vias.

[0084] The difference between this second embodiment and the first embodiment is that the hole plate in the primary and secondary resin filling processes is made of aluminum plate. Compared with film, it has a stronger supporting effect, which can prevent the PCB board from deforming during the hole filling process. It also has better heat dissipation. When drilling at high speed on the PCB board, the aluminum plate can help absorb and dissipate heat, preventing the PCB board from being damaged due to local overheating. Under normal use and maintenance, the aluminum plate can be reused multiple times.

[0085] The above are merely preferred embodiments of this application and do not constitute any limitation on this application. Any person skilled in the art can make many possible variations and modifications to the technical solution of this application, or modify it into equivalent embodiments, without departing from the scope of the technical solution of this application. Therefore, all equivalent changes made based on the shape, structure, and principle of this application without departing from the content of the technical solution of this application should be covered within the protection scope of this application.

Claims

1. A PCB resin via plugging process, characterized in that, include: S1, use chemical cleaning agents to thoroughly clean the PCB to be plugged, remove contaminants inside the vias, and form a micro-etched surface on the inner wall of the vias; S2, select a low viscosity resin according to the application requirements of the PCB; S3, perform one resin filling, and use a diagonal filling method to fill the resin in two stages to print the low viscosity resin onto the PCB through the stencil, so that the low viscosity resin flows into the via through the opening on the stencil, and the via of the PCB is subjected to high frequency vibration during the filling process. During the two glue application processes, the PCB is tilted in opposite directions to facilitate the two glue application processes. S4, according to the curing characteristics of the low viscosity resin, the low viscosity resin inserted into the PCB via is cured; S5, perform secondary resin filling, use diagonal filling method to fill the resin on the PCB in two stages, print the resin on the PCB through the stencil, let the resin flow into the via through the opening on the stencil, and fill the end of the via with resin. The thickness of the adhesive filler is equal to the sum of the copper plating thickness and the thickness to be ground in the subsequent process. S6, the resin filled with secondary resin is cured using the method described in S4; S7, Demolding and smoothing: Use grinding to smooth the cured resin end face; S8, thicken the copper plating on the via; S9, a solder mask is applied to the PCB, in which the resin-filled holes are not exposed, and the solder mask layer is flush with the resin surface after the first solder mask is formed. S10, secondary solder mask, includes exposure of the resin-filled vias to protect the resin and thickened copper plating at the resin-filled vias.

2. The PCB resin via plugging process according to claim 1, characterized in that: During the process of thoroughly cleaning the PCB to be plugged with chemical cleaning agents, ultrasonic cleaning is also used as an auxiliary process.

3. The PCB resin via plugging process according to claim 1, characterized in that: The viscosity range of the low-viscosity resin is 100-1000 cps.

4. The PCB resin via plugging process according to claim 1, characterized in that: During the process of printing the low-viscosity resin onto the PCB through a stencil using a diagonal glue-applying method in two stages, the tilt angle of the PCB is 30°-120°.

5. The PCB resin via plugging process according to claim 1, characterized in that: The high-frequency vibration of the PCB vias during the filling process is achieved by using an ultrasonic generator with a frequency of 20-40kHz to generate high-frequency vibration.

6. The PCB resin via plugging process according to claim 1, characterized in that: The aperture of the stencil used in the secondary resin filling process is smaller than the aperture of the via, and the difference between the aperture of the stencil and the aperture of the via is equal to the thickness of the copper plating.

7. The PCB resin via plugging process according to claim 1, characterized in that: The perforated plate used in the secondary resin filling process has tangential edge-wiping holes for venting during the filling process.

8. The PCB resin via plugging process according to claim 1, characterized in that: The stencils for primary and secondary resin filling are made using film.

9. The PCB resin via plugging process according to claim 1, characterized in that: The perforated plates for primary and secondary resin filling are made of aluminum plates.

10. The PCB resin via plugging process according to claim 1, characterized in that: The low-viscosity resin inserted into the PCB via is cured by photocuring.

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