A PCB manufacturing method and device for reducing electromagnetic interference

Abstract

The embodiment of the application relates to the technical field of PCB manufacturing, and particularly relates to a PCB manufacturing method and device for reducing electromagnetic interference, the method comprises a pre-process, a character printing process, a conductive paste printing process and an electrical test process, the application prints the conductive paste in the character printing process, specifically, a conductive coating is manufactured on the surface of a PCB multilayer board according to second printing data, and the conductive coating is insulated from outer layer circuits of the PCB multilayer board. The electrical performance of the conductive coating is detected, so that the electromagnetic shielding effect is ensured, the interference between the conductive layer and the circuits is avoided, and the advantages of effectively reducing electromagnetic interference, improving equipment stability and communication quality and simplifying a process flow are achieved.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a PCB manufacturing method and apparatus for reducing electromagnetic interference. Background Technology

[0002] In modern electronic devices and communication systems, electromagnetic interference (EMI) and radio frequency interference (RFI) have become critical issues affecting equipment performance, communication quality, and measurement and control accuracy. With the increasing integration of electronic devices and the widespread application of wireless communication technologies, the electromagnetic environment is becoming increasingly complex, and interference problems are becoming more prominent, posing a severe challenge to the reliability and stability of equipment.

[0003] Impact on Equipment Performance: Electromagnetic interference (EMI) can overload internal circuitry, leading to component damage or performance degradation. For example, in computer systems, EMI can interfere with the normal operation of the processor or memory, causing system crashes or data corruption, severely impacting stable equipment operation. Furthermore, high-frequency electromagnetic noise can couple to sensitive circuits, reducing signal integrity and even causing permanent hardware damage.

[0004] Impact on Communication Quality: In fields such as wireless communication, satellite communication, and avionics, electromagnetic interference can significantly degrade signal quality, leading to communication interruptions or increased bit error rates. For example, during flight, strong electromagnetic interference can disrupt communication between the pilot and ground control tower, seriously threatening flight safety. Similarly, in mobile communication and Internet of Things (IoT) applications, interference can cause data transmission delays or losses, affecting user experience and system reliability.

[0005] Impact on Measurement and Control Accuracy: High-precision electronic measuring instruments (such as oscilloscopes and spectrum analyzers) are susceptible to electromagnetic interference, leading to distorted measurement data or increased errors. In industrial automation, electromagnetic interference can cause abnormal control signals, resulting in malfunctions of actuators and even production line shutdowns, causing economic losses. For example, in intelligent manufacturing and robot control systems, weak interference signals may be misinterpreted as valid commands, thereby disrupting the entire control process.

[0006] Currently, common anti-interference technologies include shielding, filtering, and grounding optimization. However, in high-frequency, high-density electronic systems, the suppression effect of traditional methods is limited, and they may increase system complexity and cost. Summary of the Invention

[0007] In view of the above problems, embodiments of the present invention provide a PCB manufacturing method and apparatus for reducing electromagnetic interference, which solves the problem that in the prior art, the suppression effect of traditional methods in high-frequency, high-density electronic systems is limited, and may increase system complexity and cost.

[0008] According to one aspect of the present invention, a PCB manufacturing method for reducing electromagnetic interference is provided, the method comprising: Previous process: Obtaining a multilayer PCB board; Text printing process: Create a character layer on the surface of the PCB multilayer board according to the first printing data; Conductive paste printing process: A conductive coating is formed on the surface of the PCB multilayer board according to the second printing data, wherein the conductive coating is insulated from the outer layer circuit of the PCB multilayer board; Electrical testing process: The conductive coating is subjected to electrical performance testing. If the test is passed, the process proceeds to the next step; otherwise, no further processing is performed.

[0009] In some optional embodiments, the conductive paste printing process specifically includes: Pre-printing treatment of conductive paste and multilayer PCBs; The prepared conductive paste is printed onto the PCB multilayer board using a printing screen to form a conductive coating. Bake the PCB multilayer board at a baking temperature of 120℃-140℃ for 20-40 minutes; By randomly selecting PCB multilayer boards for appearance and electrical performance testing, if the test is passed, the PCB multilayer board is transferred to the next process; otherwise, the PCB multilayer boards in the same batch are remade.

[0010] In some optional embodiments, the pre-printing treatment of the conductive paste and PCB multilayer board specifically includes: Thaw the conductive paste at room temperature for at least 2 hours, and stir the conductive paste thoroughly before printing; Clean the PCB multilayer board by acid washing and / or water washing, and check to confirm that there are no oil stains or oxidation on the PCB board surface. If so, then conductive paste printing can proceed; otherwise, the PCB multilayer board needs to be cleaned.

[0011] In some optional embodiments, the treated conductive paste is printed onto the PCB multilayer board using a printing screen to form a conductive coating, specifically including: A 61T screen and a 50um water film are used to print conductive paste on the surface of a multilayer PCB board. The conductive paste is then squeegeed to form a conductive coating. The screen spacing is 5±3mm, the squeegee speed is 80-110mm / s, the squeegee pressure is 30-50kgf, and the squeegee angle is 15±10°.

[0012] In some optional embodiments, in the second printed material, the distance between the conductive paste and the PTH hole or PAD is greater than or equal to 16 mil, the distance between the conductive paste and the NPTH hole is greater than or equal to 12 mil, and the distance between the conductive paste and different networks is greater than or equal to 22 mil; the conductive coating thickness is 10um-30um, and the conductive paste is SW180T7 conductive paste.

[0013] In some optional embodiments, the text printing process specifically includes: Pretreatment of PCB multilayer boards is performed by brush cleaning or acid cleaning. A screen printing stencil is made according to the first printing material, and the ink on the screen printing stencil is squeezed out by a squeegee to create characters on the surface of the PCB multilayer board. Place the multilayer PCB board in an oven and bake at 120℃~150℃ for 10~30 minutes for heat curing.

[0014] In some optional embodiments, the electrical testing process specifically includes: using a multimeter to test any two networks of the PCB multilayer board to determine whether they are conductive; if so, the printing is defective and the PCB multilayer boards of the same batch are remade; if they are not conductive, the test is passed and the PCB multilayer board is transferred to the next process.

[0015] In some optional embodiments, after the electrical testing step, the following is further included: Finished product inspection process: Perform AOI inspection or manual inspection on the conductive paste to determine whether the conductive paste is uniform and free of impurities. If so, the PCB multilayer board is a finished PCB product; otherwise, the PCB multilayer board is remade.

[0016] In some optional embodiments, the preceding process sequentially includes material cutting, inner layer circuitry, inner layer AOI, lamination, drilling, outer layer circuitry, outer layer AOI, and solder masking to produce a multilayer PCB board.

[0017] According to another aspect of the present invention, a PCB manufacturing apparatus for reducing electromagnetic interference is provided, characterized in that the apparatus is used to perform the above-described PCB manufacturing method for reducing electromagnetic interference to manufacture a printed circuit board.

[0018] This invention discloses a PCB manufacturing method and apparatus for reducing electromagnetic interference. The beneficial effects are as follows: The method includes a pre-process, a text printing process, a conductive paste printing process, and an electrical testing process. Specifically, the conductive paste is printed during the text printing process, forming a conductive coating on the surface of the PCB multilayer board according to second printing data. This conductive coating is insulated from the outer layer circuitry of the PCB multilayer board. The conductive coating is then subjected to electrical performance testing, thereby ensuring electromagnetic shielding effectiveness while avoiding interference between the conductive layer and the circuitry. This method effectively reduces electromagnetic interference, improves equipment stability and communication quality, and simplifies the process flow.

[0019] The above description is merely an overview of the technical solutions of the embodiments of the present invention. In order to better understand the technical means of the embodiments of the present invention and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0020] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 A flowchart illustrating the PCB fabrication method for reducing electromagnetic interference according to Embodiment 1 of the present invention is shown. Figure 2 A detailed flowchart of step 130 of Embodiment 1 provided by the present invention is shown; Figure 3 A detailed flowchart of step 120 of Embodiment 1 provided by the present invention is shown. Detailed Implementation

[0021] Exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the invention are shown in the drawings, it should be understood that the invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0022] Example 1: Figure 1 This invention illustrates a first embodiment of a PCB manufacturing method for reducing electromagnetic interference, the method comprising: 110, Pre-process: Obtaining a multilayer PCB board; In step 110, the pre-process includes sequentially performing material cutting, inner layer circuitry, inner layer AOI, lamination, drilling, outer layer circuitry, outer layer AOI, and solder masking to produce a multilayer PCB board.

[0023] 120. Text printing process: A character layer is made on the surface of the PCB multilayer board according to the first printing data; In step 120, the text printing process specifically includes: pre-treatment of the PCB multilayer board by brush cleaning or acid cleaning; making a screen printing stencil according to the first printing data, and making characters on the surface of the PCB multilayer board by squeezing the ink on the screen printing stencil with a squeegee; placing the PCB multilayer board in an oven and baking it at 120℃~150℃ for 10~30 minutes for heat curing.

[0024] 130. Conductive paste printing process: A conductive coating is formed on the surface of the PCB multilayer board according to the second printing data, wherein the conductive coating is insulated from the outer layer circuit of the PCB multilayer board; In step 130, the conductive paste printing process specifically includes: pre-printing treatment of the conductive paste and the PCB multilayer board; printing the treated conductive paste onto the PCB multilayer board through a printing screen to form a conductive coating; baking the PCB multilayer board at a baking temperature of 120℃-140℃ for 20min-40min; randomly selecting PCB multilayer boards for appearance and electrical performance testing, if the test passes, the PCB multilayer board is transferred to the next process, otherwise the PCB multilayer boards in the same batch are remade.

[0025] 140. Electrical Testing Step: Perform electrical performance testing on the conductive coating. If the test passes, proceed to the next step; otherwise, no processing is performed. Specifically, step 140 includes: using a multimeter to test any two networks on the PCB multilayer board to determine if they are conductive. If they are, the printing is defective, and the PCB multilayer boards in the same batch are remade. If they are not conductive, the test passes, and the PCB multilayer board is transferred to the next step.

[0026] This application proposes a technical solution including a pre-processing step of obtaining a multilayer PCB board, a text printing process to create a character layer, a conductive paste printing process to form a conductive coating that is insulated from the outer circuitry, and an electrical testing process to test the performance of the conductive coating. If the test is passed, the board proceeds to the next process; otherwise, processing is stopped.

[0027] In this embodiment, the preceding process refers to the fabrication of a multilayer circuit board using conventional processes such as material cutting, lamination, and drilling. This can be achieved using a standard PCB production line, providing a foundation for subsequent processing. The text printing process involves forming identification information on the board surface using screen printing technology, specifically through ink scraping, facilitating circuit debugging and maintenance. The conductive paste printing process involves forming a conductive coating in specific areas of the board surface. This coating maintains insulation from the outer circuitry, and can be achieved using screen printing combined with insulating materials, forming an electromagnetic shielding layer while preventing short circuits. The electrical testing process involves testing the conductivity of the conductive coating, which can be achieved by measuring the insulation resistance between adjacent networks using a multimeter, ensuring the electrical reliability of the shielding layer.

[0028] Specifically, after the basic fabrication of the multilayer board is completed, a character layer is first printed on the surface to identify circuit components. Then, conductive paste is printed in the non-circuit areas to form a continuous coating. This coating is positioned using a screen to maintain a safe distance from the outer circuitry. After curing, the coating undergoes a continuity test to confirm that its conductivity meets requirements and that it is not in contact with the circuitry. Through this layered processing and testing mechanism, electromagnetic shielding is achieved while avoiding impact on the original circuitry structure. Automated equipment is used to connect each process, improving production continuity.

[0029] Compared to existing technologies, traditional solutions require embedding a metal shielding layer or adding a grounding layer within the board, necessitating modifications to the original circuit design and additional processing steps. This solution achieves electromagnetic isolation by applying an independent conductive coating to the surface, without modifying the existing circuit layout, while also simplifying the manufacturing process. The phased inspection mechanism makes it easier to trace quality issues compared to final product inspection, reducing rework costs.

[0030] Through the above technical solutions, this application can effectively suppress electromagnetic interference during high-frequency signal transmission and ensure the signal transmission stability of communication base stations. The conductive coating with insulation prevents the generation of parasitic capacitance, ensuring signal integrity. A step-by-step inspection mechanism promptly eliminates defective products with poor conductivity, improving the finished product yield. The entire manufacturing process is compatible with existing PCB production lines, requiring no additional specialized equipment, and has high feasibility.

[0031] Example 2: This embodiment is based on Embodiment 1, and further refines each step of the pre-process, text printing process, conductive paste printing process and electrical testing process of Embodiment 1.

[0032] In one embodiment of this invention, a PCB manufacturing method for reducing electromagnetic interference is proposed, and step 130 in Embodiment 1 is further described. The specific process is as follows: 131. Pre-printing treatment of conductive paste and PCB multilayer boards. 132. The prepared conductive paste is printed onto a multilayer PCB board using a printing screen to form a conductive coating. 133. Bake the PCB multilayer board at a baking temperature of 120℃-140℃ for 20min-40min; 134. Randomly select PCB multilayer boards for appearance and electrical performance testing. If the test is passed, the PCB multilayer board is transferred to the next process; otherwise, the PCB multilayer boards in the same batch are remade.

[0033] In steps 131-134, pre-printing treatment refers to the process of pre-treating the conductive paste and substrate surface. Specifically, this can be achieved by thawing the conductive paste at room temperature and stirring it, and by cleaning the PCB board surface through acid washing or water washing. This step eliminates the impact of material state differences and surface contaminants on printing quality. The printing screen refers to the graphic template used to transfer the conductive paste. Specifically, it can be implemented using a screen structure with a specific mesh count and photosensitive material. This structure allows for precise control of the coating position and thickness of the conductive paste. Baking temperature refers to the heat treatment conditions required to cure the conductive coating. Specifically, this can be achieved using a tunnel oven with segmented temperature control. This condition can prevent coating cracking or blistering and improve adhesion. Random sampling inspection refers to the process of selecting samples from the production batch for quality verification. Specifically, this can be achieved using visual inspection combined with a four-probe tester. This method can quickly identify whether the conductive coating has short circuits or uneven thickness defects.

[0034] Specifically, in the conductive paste printing process, the conductive paste is first thawed and stirred to reach a suitable viscosity for printing, while the PCB surface is cleaned to remove oxide layers and residues. Next, screen printing technology is used to transfer the conductive paste to designated areas, and a uniform coating is formed by precisely controlling the squeegee parameters. The printed substrate is then baked at a specific temperature and time to cure the coating. Finally, batches of products are sampled and tested, and only qualified products are allowed to proceed to subsequent processes.

[0035] Compared with existing technologies, traditional methods often neglect the pretreatment of conductive paste, leading to a high printing defect rate, and the lack of temperature gradient control during the curing process easily causes stress concentration. This invention, through systematically setting printing parameters and detection mechanisms, improves coating consistency while avoiding material performance degradation caused by localized overheating.

[0036] Through the above technical solution, this application effectively solves the problem of electromagnetic shielding failure caused by poor printing of conductive coating. By standardizing the process, the coating thickness deviation is controlled within a reasonable range, reducing signal crosstalk caused by uneven distribution of conductive paste, thereby improving the anti-interference ability of the finished product in complex electromagnetic environments.

[0037] In step 131, the present invention proposes a specific method for pre-printing treatment of conductive paste and PCB multilayer boards, including thawing the conductive paste at room temperature for at least 2 hours and stirring it thoroughly before printing; cleaning the PCB multilayer board by acid washing or water washing, and checking to confirm that the board surface is free of oil stains and oxidation. If the conditions are met, conductive paste printing is performed; otherwise, the board is cleaned again.

[0038] In this embodiment, thawing at room temperature refers to the conductive paste naturally returning to room temperature without heating. This can be achieved by placing it in a well-ventilated environment. This step avoids stratification or abnormal viscosity of the conductive paste components due to sudden temperature changes. Thorough mixing refers to uniformly mixing the components of the conductive paste mechanically or manually. Specifically, a mixer can be used to periodically rotate the paste at a fixed speed. This operation eliminates air bubbles or uneven concentrations that may occur after the conductive paste has settled. Acid washing refers to removing residual organic contaminants from the PCB board surface using an acidic solution. This can be achieved by soaking in a diluted sulfuric acid solution followed by rinsing. This treatment enhances the adhesion between the conductive paste and the board surface. Water washing refers to removing acid washing residue and particulate impurities by rinsing with running clean water. This can be achieved by using a high-pressure spray device for multi-angle rinsing. This step avoids chemical residues affecting the quality of the conductive coating.

[0039] Specifically, after thawing, the conductive paste is stirred to restore its homogeneous state. Simultaneously, the PCB board undergoes a dual cleaning process of acid pickling and water washing to remove surface contaminants, and the cleanliness of the board surface is confirmed visually or through instrumental inspection. If oil stains or oxidation residues are detected, the cleaning process is repeated until printing conditions are met. This ensures stable contact between the conductive paste and the board surface during printing, preventing coating peeling or localized conductive abnormalities caused by contaminants.

[0040] Compared with existing technologies, conventional processes use conductive paste directly without thawing and stirring, which can easily lead to uneven coating thickness due to unstable material conditions. Furthermore, PCB board cleaning often employs a single method, making it difficult to completely remove the oxide layer. This method ensures the fluidity of the conductive paste through a thawing and stirring process. Combined with the synergistic effect of acid washing and water washing, it significantly improves the cleanliness of the board surface, thereby reducing the risk of electromagnetic leakage caused by impurities in the conductive coating.

[0041] Through the above technical solution, this application can solve the problem of performance fluctuation of conductive paste caused by changes in storage environment, while eliminating the negative impact of PCB board surface contaminants on conductive coating, ensuring uniform and complete conductive coating, and effectively reducing abnormal radiation of electromagnetic interference signals during board surface conduction.

[0042] In step 132, the present invention proposes to print the treated conductive paste onto a PCB multilayer board using a printing screen to form a conductive coating. Specifically, this includes: printing conductive paste onto the surface of the PCB multilayer board using a 61T screen and a 50um water film, and then applying the conductive paste with a squeegee to form a conductive coating. The screen spacing is 5±3mm, the squeegee speed is 80-110mm / s, the squeegee pressure is 30-50kgf, and the squeegee angle is 15±10°.

[0043] In this embodiment, a 61T screen refers to a screen printing screen with a mesh count of 61T, specifically made of polyester or stainless steel. The mesh count is chosen to match the conductive paste particle size and printing precision requirements, controlling the amount of conductive paste transferred. A 50µm water-soluble photosensitive adhesive layer refers to a 50µm thick water-soluble photosensitive adhesive layer, specifically formed on the screen surface through a coating process, used to define the printing area of ​​the conductive coating. Screen spacing refers to the vertical distance between the printing screen and the PCB board surface, which can be adjusted by the printing equipment to avoid pattern deformation caused by contact between the screen and the board surface. Squeegee speed refers to the moving speed of the squeegee during the printing process; squeegee pressure refers to the vertical force applied by the squeegee to the screen; and squeegee angle refers to the angle between the squeegee and the screen plane. These three parameters work together to control the uniformity and thickness consistency of the conductive paste filling. Furthermore, the conductive paste can be an SW180T7 conductive coating. In this invention, the conductive paste printing production parameters are shown in Table 1 below:

[0044] Table 1 Specifically, during the printing process, a printing template formed by combining a 61T screen and a 50µm water-based film is fixed on the printing equipment. Conductive paste is evenly spread on the screen surface using a squeegee. As the squeegee moves at a specific speed, pressure, and angle, the conductive paste is squeezed through the opening area of ​​the screen onto the PCB board, forming a conductive coating of a predetermined thickness. The screen spacing is carefully designed to prevent direct friction between the screen and the board surface during the squeegee process, avoiding blurring or misalignment of the pattern. The combination of squeegee parameters optimizes the flowability and filling effect of the conductive paste, ensuring that the coating thickness meets electromagnetic shielding requirements while preventing paste overflow or uneven thickness due to excessive squeezing.

[0045] Compared with existing technologies, the traditional conductive paste printing process typically sets the screen mesh count and squeegee parameters based on experience, without precise matching to the specific requirements of the electromagnetic shielding coating. For example, a conventional screen mesh count that is too low may lead to uneven distribution of conductive particles, while excessive squeegee pressure can easily damage the water-film structure. This solution, by defining the screen type, water-film thickness, and squeegee parameter range, establishes standardized operating procedures, thus solving the coating defect problem caused by poor parameter adaptability in traditional processes.

[0046] Through the above technical solution, this application achieves precise control of parameters during the conductive coating printing process, effectively improving the uniformity of coating thickness and edge clarity, thereby enhancing the stability of electromagnetic shielding performance. Simultaneously, the parameter range setting reduces the operator's reliance on technical expertise, avoids quality fluctuations caused by individual operational differences, and improves product yield and batch consistency.

[0047] Furthermore, this invention proposes that in the second printed material, the distance between the conductive paste and the PTH hole or PAD is greater than or equal to 16 mil, the distance between the conductive paste and the NPTH hole is greater than or equal to 12 mil, and the distance between the conductive paste and different networks is greater than or equal to 22 mil; the conductive coating thickness is 10um-30um, and the conductive paste is SW180T7 conductive paste.

[0048] In this embodiment, PTH vias refer to metallized vias, whose inner walls are electroplated to form a conductive layer to achieve electrical connection between different layers. Specifically, this can be achieved by mechanical drilling followed by chemical copper plating. This via structure requires the conductive paste to maintain a safe spacing to avoid short circuits. NPTH vias refer to non-metallized vias, whose walls are not electroplated and do not possess conductivity. Specifically, this can be achieved by mechanical drilling without copper plating. This via structure has lower requirements for the spacing of the conductive paste but must prevent the coating material from penetrating. The distance between different networks refers to the interval between conductive coatings belonging to different electrical circuits. This can be achieved through the design of the printing stencil pattern to avoid electromagnetic coupling between different signal paths. The conductive coating thickness refers to the vertical height of the coating after printing and curing. This can be controlled by adjusting the stencil mesh count, squeegee parameters, and baking process. This thickness range balances conductivity and adhesion. SW180T7 conductive paste refers to a silver paste material with a specific viscosity and conductive particle ratio. Specifically, it can be achieved using an epoxy resin-based conductive adhesive with a silver powder content of 70%-80%. The conductive pathways formed after curing can effectively shield high-frequency electromagnetic interference.

[0049] Specifically, during the printing of conductive coatings, a 16mil isolation band around the PTH vias prevents short circuits caused by contact between the conductive paste and the metal layer inside the vias, while also preventing stress cracking of the metallized vias due to thermal expansion during high-temperature baking. A 12mil spacing for NPTH vias prevents conductive paste from seeping into the vias and contaminating the board, while also reducing material waste. A 22mil spacing between different networks effectively blocks crosstalk paths of high-frequency signals between adjacent conductive coatings. Controlling the conductive coating thickness within the 10-30 micrometer range ensures electromagnetic shielding effectiveness while avoiding problems such as reduced adhesion or poor heat dissipation caused by excessively thick coatings. When using SW180T7 conductive paste, its unique fine-grained silver powder distribution allows the cured coating to form a continuous conductive grid, and the appropriate resin content maintains stable dielectric properties under high-frequency conditions.

[0050] Compared to existing technologies, traditional conductive coating processes often employ uniform spacing standards, failing to differentiate the protection requirements of PTH and NPTH vias, which can easily lead to potential short-circuit risks around metallized vias. Existing technologies typically use conductive coatings thicker than 30 micrometers to improve conductivity, but this increases coating brittleness and susceptibility to cracking during thermal cycling. This application, through graded spacing control, ensures the insulation reliability of critical areas while optimizing material utilization. Compared to conventional conductive paste materials, SW180T7 conductive paste achieves lower surface resistance at the same thickness, and its unique curing properties reduce volume shrinkage during baking, thereby improving the bonding strength between the coating and the substrate.

[0051] Through the above technical solution, this application effectively solves the signal short circuit problem caused by the contact between the conductive coating and the metallized via in high-frequency circuits, and reduces crosstalk caused by electromagnetic coupling between different networks. By precisely controlling the geometric parameters and material properties of the conductive coating, the electromagnetic shielding effect is ensured while avoiding the decrease in mechanical reliability caused by excessive coating thickness. It is particularly suitable for PCB manufacturing of high-frequency electronic products such as 5G communication equipment and millimeter-wave radar.

[0052] In one embodiment of this example, step 120 in Example 1 is further described. The specific process is as follows: 121. In the text printing process, brush cleaning or acid washing is used as a pretreatment for PCB multilayer boards. 122. Based on the first printing data, a screen printing stencil is made, and characters are formed by pressing ink through a squeegee. 123, a technical solution for thermosetting PCB multilayer boards by placing them in an oven and baking them at 120°C to 150°C for 10 to 30 minutes.

[0053] In steps 121-123, brush cleaning refers to removing residues from the PCB board surface through mechanical friction, specifically using nylon or ceramic brushes with a cleaning agent. Its purpose is to eliminate surface contaminants and improve ink adhesion. Acid cleaning involves using an acidic solution to corrode the oxide layer of the PCB board surface, such as immersion in diluted hydrochloric acid or sulfuric acid solutions. Its purpose is to remove the oxide film and enhance the bonding strength between the ink and the substrate. The screen printing stencil is a template used to carry the ink pattern, specifically made of metal or polyester material through laser engraving. Its purpose is to accurately transfer character graphics to the PCB surface. Squeegee ink extrusion involves applying pressure with a squeegee to force the ink through the stencil's apertures, for example, using a polyurethane squeegee with constant pressure and uniform speed. Its purpose is to form a uniform and continuous character layer. Thermal curing involves accelerating the ink cross-linking reaction through heating, such as using a tunnel oven for continuous heating. Its purpose is to rapidly form a cured layer resistant to mechanical stress.

[0054] Specifically, this process first involves cleaning the PCB surface using physical or chemical methods to eliminate the impact of oil and oxide layers on printing quality. Next, the designed character pattern is created into a high-precision screen, and squeegee parameters are controlled to ensure that ink evenly fills the mesh openings and is completely transferred to the substrate surface. Finally, a stepped heating and baking process allows the resin components in the ink to fully polymerize, forming a cured character layer that is tightly bonded to the substrate. This process effectively avoids character defects caused by incomplete pretreatment in traditional processes, while precise temperature-controlled curing improves the mechanical stability of the character layer.

[0055] Compared with existing technologies, traditional text printing processes often employ a single cleaning method and lack strict control over curing parameters, which can easily lead to insufficient character adhesion or incomplete curing. This solution combines a composite cleaning method with precise temperature and time control, enabling the character layer to effectively resist mechanical scratching during subsequent conductive paste printing processes, thus avoiding the risk of short circuits in the conductive coating caused by character detachment.

[0056] Through the above technical solution, this application achieves a reliable bond between the character layer and the substrate, preventing metal debris contamination caused by character detachment during subsequent conductive coating fabrication. Simultaneously, the resulting smooth character surface provides a uniform base for conductive paste printing, effectively reducing coating thickness variations caused by substrate unevenness, thereby improving the stability of the electromagnetic shielding effect.

[0057] In one embodiment of this invention, the electrical testing process specifically includes using a multimeter to test any two networks on the PCB multilayer board to determine whether they are conductive. If they are, the printing is defective and the PCB multilayer boards of the same batch are remade. If they are not conductive, the test is passed and the PCB multilayer board is transferred to the next process.

[0058] In this embodiment, multimeter testing refers to using a testing instrument with resistance measurement capabilities to verify the electrical isolation performance of the conductive coating-covered area. Specifically, a digital multimeter in low-resistance mode can be used to determine the presence of short-circuit defects by measuring the resistance values ​​between different networks. Batch rework refers to the batch rework of PCBs with conductive coating printing defects. This can be achieved by re-performing the conductive paste printing and baking processes, thereby preventing defective products from entering subsequent assembly stages.

[0059] Specifically, after the conductive coating is formed, the continuity between any two independent networks is sampled and tested using a multimeter. If continuity exists between the two networks, it indicates that the conductive coating has failed to effectively isolate adjacent lines, potentially causing electromagnetic interference or signal crosstalk; in this case, all PCBs in the same batch must be returned to the conductive paste printing process for rework. If no continuity is detected, the insulation performance of the conductive coating is confirmed to be qualified, and it is allowed to proceed to the subsequent processing steps.

[0060] Compared to existing technologies, traditional methods often rely on visual inspection or single-network testing, which cannot effectively identify short circuits across networks in conductive coatings. This solution, through systematic inter-network continuity detection, can quickly locate coating printing defects. Simultaneously, combined with a batch management mechanism, it prevents localized defects from spreading to the entire production batch, significantly improving the efficiency of defective product interception.

[0061] Through the above technical solution, this application effectively solves the electromagnetic interference risk caused by abnormal conductive coating printing, ensuring the insulation reliability between different networks. By linking continuity testing with batch rework, it avoids overall scrapping due to localized defects, reduces rework costs, and improves the finished product qualification rate.

[0062] In one embodiment of this invention, after the electrical testing process, a finished product inspection process is also included: AOI testing or manual inspection of the conductive paste to determine whether the conductive paste is uniform and free of impurities. If so, the PCB multilayer board is a finished PCB product; otherwise, the PCB multilayer board is remade.

[0063] In this embodiment, AOI inspection refers to the automated image acquisition and analysis of the conductive paste surface using optical imaging equipment. Specifically, a high-resolution camera combined with image recognition algorithms can be used to identify the presence of bubbles, scratches, or foreign matter in the coating. Manual inspection refers to the operator visually inspecting the surface quality using magnifying equipment, such as a microscope or magnifying glass, to supplement and verify subtle defects that may be missed by the AOI equipment. The finished product inspection process, through a dual inspection mechanism, can cover the blind spots of automated inspection and avoid a decrease in electromagnetic shielding performance due to uneven coating or foreign matter residue.

[0064] Specifically, after the electrical testing process is completed and the conductive coating has passed conductivity verification, a final product inspection process is added to confirm the physical morphology of the coating. For example, in AOI inspection, the equipment scans the surface of the conductive coating and compares it with a preset standard image to identify areas of abnormal thickness or impurity particles. For suspicious areas marked by AOI inspection, further manual re-inspection is conducted to eliminate false judgments. If both inspections confirm that the coating meets the uniformity requirements, it is judged as a qualified finished product; if defects are detected in the coating, the batch of PCB boards is reprocessed to prevent defective products from entering subsequent application stages.

[0065] Compared to existing technologies, traditional methods typically only verify the electrical performance of the conductive coating during the electrical testing phase, without systematically testing the coating's physical morphology. This invention, by adding a finished product inspection step, can effectively identify issues such as uneven coating thickness or impurity intrusion caused by fluctuations in the printing process. While these issues do not affect conductivity, they can reduce the coating's electromagnetic shielding effect. For example, in existing technologies, uncured conductive paste residue particles may generate parasitic capacitance under high-frequency environments; this invention, through a dual detection mechanism, can eliminate such potential problems in advance.

[0066] Through the above technical solutions, this application can ensure the physical integrity and surface cleanliness of the conductive coating, avoid local electromagnetic field distortion caused by coating defects, and thus improve the anti-interference capability of the PCB product in a high-frequency environment. For example, detected impurity particles can prevent them from forming electromagnetic coupling points in the circuit, and uniform coating thickness can maintain stable shielding effectiveness, ultimately reducing the risk of signal distortion of equipment in complex electromagnetic environments.

[0067] In one embodiment of this invention, the preceding processes sequentially include material cutting, inner layer circuitry, inner layer AOI, lamination, drilling, outer layer circuitry, outer layer AOI, and solder masking to fabricate a multilayer PCB board.

[0068] In this embodiment, cutting refers to the process of cutting the copper-clad substrate into a set size. Specifically, it can be achieved by using a CNC cutting machine to cut the FR-4 material. By precisely controlling the cutting size, the basic accuracy of subsequent processes can be ensured.

[0069] The inner layer circuit refers to the process of forming conductive patterns on the surface of a substrate. Specifically, it can be achieved by dry film lamination followed by exposure and development to form circuit patterns. This step uses photochemical etching to form a precise circuit layout.

[0070] Inner layer AOI refers to the process of detecting defects in inner layer circuits using automated optical inspection equipment. Specifically, it can be implemented using line width and spacing measurement and open / short circuit detection modules to eliminate line misalignment or residual copper defects.

[0071] Pressing refers to the process of bonding multiple layers of substrates with thermosetting resin. Specifically, it can be achieved by laminating and bonding layers under high temperature and high pressure using a vacuum hot press to ensure interlayer insulation and structural stability.

[0072] Drilling refers to the process of creating through holes in a laminate, which can be achieved using mechanical drill bits or laser drilling equipment, providing a channel for subsequent metallization hole processes.

[0073] The outer layer circuitry refers to the process of creating an outer conductive pattern on the surface of the laminated substrate. Specifically, it can be achieved by selectively depositing a copper layer using a pattern electroplating process to form an outer electrical connection structure.

[0074] Outer layer AOI refers to the process of performing secondary optical inspection on the outer layer circuitry. Specifically, it can be achieved by using three-dimensional imaging technology to detect the flatness of the circuitry, preventing circuit warping from affecting the subsequent application of conductive paste.

[0075] Solder resist refers to the process of covering the surface of a substrate with a solder resist layer. Specifically, it can be achieved by screen printing liquid photosensitive solder resist ink, which is then selectively cured to form an insulating protective layer.

[0076] Specifically, in the substrate pretreatment stage, the substrate size is standardized through the blanking process. Then, the core conductive layer is formed through inner layer circuitry, and potential circuit defects are eliminated through inner layer AOI inspection. After the multilayer structure is built through lamination, the drilling process forms interlayer conductive paths, and the outer layer circuitry completes surface electrical connections. The outer layer AOI inspection ensures the integrity of the outer layer circuitry. Finally, the solder mask process covers the insulating layer, forming a multilayer PCB board with a complete interlayer structure. The cascading execution of these processes effectively controls interlayer insulation performance, reduces the risk of potential short circuits between conductive layers, and thus creates stable substrate conditions for subsequent printing of the conductive coating.

[0077] Compared with existing technologies, current PCB manufacturing processes often employ a phased, independent processing model, with quality control points scattered between each process. This can easily lead to residual stress or interlayer misalignment defects within the laminate. This application, by strictly limiting the execution sequence of preceding processes and placing inner-layer AOI and outer-layer AOI before and after the lamination process respectively, forms a dual detection mechanism. This can promptly eliminate interlayer alignment errors caused by inner-layer circuit deformation. In particular, the outer-layer AOI process is performed after drilling, allowing simultaneous detection of drilling quality and circuit integrity, avoiding conductive paste printing defects caused by drilling burrs in traditional processes.

[0078] Through the above technical solutions, this application can improve the flatness and alignment accuracy of the interlayer structure of PCB multilayer boards, effectively reducing the electromagnetic interference conduction path caused by internal substrate defects. The dual detection mechanism of inner and outer layer AOI reduces the risk of interlayer insulation failure, and precise control of the lamination process improves the uniformity of the interlayer dielectric, thereby fundamentally suppressing electromagnetic leakage during high-frequency signal transmission. The final coverage of the solder mask process further blocks the possibility of accidental conduction between surface conductive layers, providing a stable and reliable foundation for the electromagnetic shielding function of the conductive coating.

[0079] Example 3: Based on Embodiments 1 and 2, this embodiment proposes a PCB manufacturing apparatus for reducing electromagnetic interference. The apparatus is used to perform a method for manufacturing printed circuit boards. The method includes obtaining a multilayer PCB board, performing text printing, conductive paste printing, electrical testing, and finished product inspection processes, and sequentially manufacturing the multilayer PCB board through material cutting, inner layer circuitry, inner layer AOI, lamination, drilling, outer layer circuitry, outer layer AOI, and solder mask.

[0080] In this embodiment, the conductive paste printing process involves printing conductive paste onto the surface of a multilayer PCB to form a conductive coating. This can be achieved using a printing stencil and squeegee parameter control, such as a stencil spacing of 5±3mm and a squeegee speed of 80-110mm / s. This process, by controlling the distance between the conductive paste and the via structure and the coating thickness, forms an insulating conductive layer, thereby preventing electrical interference between the outer circuitry and the conductive coating. The baking process involves curing the printed multilayer PCB, specifically using a temperature range of 120℃-140℃ and a baking time of 20min-40min. This step eliminates volatile components in the conductive paste, ensuring the stability of the coating structure. The electrical testing process involves detecting the electrical performance of the conductive coating, specifically using a multimeter to test the continuity between the interconnects. This step filters out poorly conductive PCBs, preventing electromagnetic shielding failure due to coating defects. The finished product inspection process involves inspecting the surface quality of the conductive coating, specifically using AOI equipment or manual visual inspection. This step ensures the integrity of the conductive layer and maintains the shielding effect by judging the coating uniformity and impurities.

[0081] Specifically, this device integrates printing, baking, and inspection modules, sequentially executing the conductive paste defrosting and stirring, board surface cleaning, screen printing, parametric squeegee application, and layer detection processes. The printing module uses a combination of screen and water-based film to form a conductive coating of predetermined thickness under controlled squeegee speed and angle. The inspection module links electrical testing with visual inspection to assess the quality of PCBs in the same batch, selecting boards with poor conductivity or coating defects for remanufacturing. Thus, this device can form a uniform, insulating conductive shielding layer in high-frequency, high-density electronic systems, avoiding the structural complexity problems of traditional shielding technologies.

[0082] Compared to existing technologies, traditional anti-interference methods rely on external shielding covers or filter circuits, which not only increase system size but also struggle to cope with high-frequency interference. This invention, however, integrates the conductive shielding layer directly during the PCB manufacturing stage, forming an insulating coating on the board surface through a printing process. This reduces the assembly requirements of external shielding structures and improves coating yield through in-process inspection. Furthermore, existing technologies lack coordinated control over conductive paste printing parameters, easily leading to uneven coating thickness or insufficient adhesion. This device, through optimized combinations of stencil spacing, squeegee angle, and baking conditions, ensures a tighter bond between the coating and the PCB board surface, thereby enhancing electromagnetic shielding stability.

[0083] Through the above technical solutions, this application can achieve more reliable electromagnetic interference suppression in wireless communication equipment and industrial control systems. For example, in aircraft electronic equipment, the PCB board fabricated by this device can effectively isolate radio frequency interference between airborne radar and communication modules, preventing communication interruptions caused by signal crosstalk; in intelligent manufacturing equipment, the uniform conductive coating can reduce the electromagnetic noise impact of motor drive circuits on high-precision sensors, avoiding malfunctions caused by abnormal control signals. Thus, while maintaining the compactness of the PCB structure, this device improves the operational stability and signal integrity of electronic equipment in complex electromagnetic environments.

[0084] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. Similarly, for the sake of brevity and to aid in understanding one or more aspects of the invention, in the description of exemplary embodiments of the invention above, various features of the embodiments are sometimes grouped together in a single embodiment, figure, or description thereof. The claims, which follow the detailed description, are hereby expressly incorporated into that detailed description, wherein each claim itself is a separate embodiment of the invention.

[0085] Those skilled in the art will understand that the modules in the device of the embodiment can be adaptively changed and placed in one or more devices different from that embodiment. Modules, units, or components in the embodiment can be combined into a single module, unit, or component, and further, they can be divided into multiple sub-modules, sub-units, or sub-components, except that at least some of such features and / or processes or units are mutually exclusive.

[0086] It should be noted that the above embodiments are illustrative of the invention and not restrictive, and that those skilled in the art can devise alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses should not be construed as limiting the claims. The word "comprising" does not exclude the presence of elements or steps not listed in the claims. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In the unit claims enumerating several systems, several of these systems may be embodied by the same item of hardware. The use of the words first, second, and third, etc., does not indicate any order. These words can be interpreted as names. The steps in the above embodiments, unless otherwise specified, should not be construed as limiting the order of execution.

Claims

1. A PCB manufacturing method for reducing electromagnetic interference, characterized in that, The method includes: Previous process: Obtaining a multilayer PCB board; Text printing process: Create a character layer on the surface of the PCB multilayer board according to the first printing data; Conductive paste printing process: A conductive coating is formed on the surface of the PCB multilayer board according to the second printing data, wherein the conductive coating is insulated from the outer layer circuit of the PCB multilayer board; Electrical testing process: The conductive coating is subjected to electrical performance testing. If the test is passed, the process proceeds to the next step; otherwise, no further processing is performed. The prepared conductive paste is printed onto the PCB multilayer board using a printing screen to form a conductive coating, specifically including: A 61T screen and a 50um water film are used to print conductive paste on the surface of a multilayer PCB board. The conductive paste is then squeegeed to form a conductive coating. The screen spacing is 5±3mm, the squeegee speed is 80-110mm / s, the squeegee pressure is 30-50kgf, and the squeegee angle is 15±10°. In the second printed material, the distance between the conductive paste and the PTH hole or PAD is greater than or equal to 16 mil, the distance between the conductive paste and the NPTH hole is greater than or equal to 12 mil, and the distance between the conductive paste and different networks is greater than or equal to 22 mil; the conductive coating thickness is 10um-30um, and the conductive paste is SW180T7 conductive paste.

2. The PCB manufacturing method for reducing electromagnetic interference according to claim 1, characterized in that, The conductive paste printing process specifically includes: Pre-printing treatment of conductive paste and multilayer PCBs; The prepared conductive paste is printed onto the PCB multilayer board using a printing screen to form a conductive coating. Bake the PCB multilayer board at a baking temperature of 120℃-140℃ for 20-40 minutes; By randomly selecting PCB multilayer boards for appearance and electrical performance testing, if the test is passed, the PCB multilayer board is transferred to the next process; otherwise, the PCB multilayer boards in the same batch are remade.

3. The PCB manufacturing method for reducing electromagnetic interference according to claim 2, characterized in that, The pre-printing treatment of the conductive paste and PCB multilayer board specifically includes: Thaw the conductive paste at room temperature for at least 2 hours, and stir the conductive paste thoroughly before printing; Clean the PCB multilayer board by acid washing and / or water washing, and check to confirm that there are no oil stains or oxidation on the PCB board surface. If so, then conductive paste printing can proceed; otherwise, the PCB multilayer board needs to be cleaned.

4. The PCB manufacturing method for reducing electromagnetic interference according to claim 1, characterized in that, The text printing process specifically includes: Pretreatment of PCB multilayer boards is performed by brush cleaning or acid cleaning. A screen printing stencil is made according to the first printing material, and the ink on the screen printing stencil is squeezed out by a squeegee to create characters on the surface of the PCB multilayer board. Place the multilayer PCB board in an oven and bake at 120℃~150℃ for 10~30 minutes for heat curing.

5. The PCB manufacturing method for reducing electromagnetic interference according to claim 1, characterized in that, The electrical testing process specifically includes: using a multimeter to test any two networks on the PCB multilayer board to determine whether they are conductive. If they are, the printing is defective and the PCB multilayer boards in the same batch are remade. If they are not conductive, the test is passed and the PCB multilayer board is transferred to the next process.

6. The PCB manufacturing method for reducing electromagnetic interference according to claim 1, characterized in that, Following the electrical testing procedure, the following is also included: Finished product inspection process: Perform AOI or manual inspection on the conductive paste to determine whether the conductive paste is uniform and free of impurities. If so, the PCB multilayer board is a finished PCB product; otherwise, the PCB multilayer board is remade.

7. The PCB manufacturing method for reducing electromagnetic interference according to claim 1, characterized in that, The preceding processes sequentially include material cutting, inner layer circuitry, inner layer AOI, lamination, drilling, outer layer circuitry, outer layer AOI, and solder masking to produce a multilayer PCB board.

8. A PCB manufacturing apparatus for reducing electromagnetic interference, characterized in that, The apparatus is used to perform the PCB manufacturing method for reducing electromagnetic interference as described in any one of claims 1-7, and to manufacture a printed circuit board.

Images