PCB manufacturing method and device for improving character definition

Abstract

The embodiment of the invention relates to the technical field of PCB manufacturing, in particular to a PCB manufacturing method and device for improving character definition, and the method comprises the steps of cleaning pretreatment, solder mask treatment, character forming treatment, thermocuring treatment and post-treatment, optimizes the whole character manufacturing process, and improves the character definition. The problems of low character definition and many edge defects in the background technology are solved, the definition and edge smoothness of the characters of the printed circuit board are improved, the defects of character blurring, edge ink overflow and the like are reduced, and the overall quality is improved.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a PCB manufacturing method and apparatus for improving character clarity. Background Technology

[0002] In the electronics manufacturing industry, the characters on the surface of circuit boards carry crucial information identifying the location, model, and parameters of components. Their printing quality directly affects assembly accuracy and the convenience of subsequent maintenance. Currently, the widely used screen printing process faces several technical bottlenecks in actual production that lead to blurred characters. First, the alignment accuracy of this process is greatly affected by the wear and tear during screen making and use, easily causing character misalignment and ink overflow at the edges, resulting in jagged defects. Second, on special materials such as thick copper plates, insufficient surface flatness leads to poor adhesion between the character ink and the solder resist layer, easily causing peeling or smudging during subsequent processing. Simultaneously, during the assembly process of flexible circuit boards with reinforcing plates, the character area is easily deformed and blurred due to mechanical compression. Furthermore, improper control of traditional curing process parameters, whether insufficient or excessive curing, can lead to ink surface discoloration, cracking, or decreased contrast, affecting the clarity and durability of the characters. Although there are adjustment solutions in the existing technology for specific boards or individual processes, these improvements are often limited to a single application scenario and fail to systematically solve fundamental problems such as alignment accuracy, ink adhesion and full-process protection. They have poor versatility and cannot meet the growing production demand of various circuit boards for high-definition and stable characters.

[0003] Therefore, developing a new technology that can adapt to diverse production conditions and comprehensively improve the quality and reliability of character printing is of great industrial significance. Summary of the Invention

[0004] In view of the above problems, embodiments of the present invention provide a PCB manufacturing method and apparatus to improve character clarity, which solves the problem that the existing alignment accuracy is greatly affected by the wear and tear of the stencil during manufacturing and use, which easily causes character position displacement and edge ink overflow, forming serrated defects. Secondly, on special materials such as thick copper plates, due to insufficient surface flatness, the adhesion between the character ink and the solder mask layer is poor, which easily leads to peeling or smudging in subsequent processing.

[0005] According to one aspect of the present invention, a PCB manufacturing method for improving character clarity is provided, the method comprising:

[0006] Obtain the PCB board and perform a cleaning pretreatment on the PCB board; The PCB board is subjected to solder resist treatment to create a solder resist layer on the surface of the PCB board; The PCB board is subjected to character forming processing to create a character layer in the character reserved area of ​​the PCB board; The PCB board is subjected to thermosetting treatment to solidify and shape the character layer; The PCB board is then post-processed.

[0007] In some alternative embodiments, the PCB board undergoes a cleaning pretreatment, specifically including: Determine the type of PCB board material; When the PCB board is a rigid circuit board, the oxide layer and oil stains on the PCB board surface are removed by mechanical polishing with a roughness of 0.3μm-0.5μm followed by ultrasonic cleaning. When the PCB board is a flexible circuit board, the surface of the PCB board is cleaned by plasma cleaning. When the PCB board is made of thick copper, after plasma cleaning, a leveling process is used to adjust the flatness of the PCB board.

[0008] In some alternative embodiments, the leveling process specifically includes: The PCB is rolled and leveled using a leveling device to ensure that the flatness error of the PCB is ≤0.02mm. Then, place the PCB into a baking device and dry it at a drying temperature of 60℃-80℃ for 15-20 minutes.

[0009] In some alternative embodiments, the PCB board is subjected to solder resist treatment, specifically including: Solder resist ink is screen-printed on the surface of the PCB board; The solder resist ink is initially cured on the PCB board at a baking temperature of 100℃-120℃ for 20min-30min. The non-character reserved areas and non-line patch areas on the PCB board surface are exposed and cured with an exposure energy of 80-100mJ / cm². By developing the PCB board, the ink on the surface of the unexposed and uncured character reserved area and circuit patch area is removed to form a solder resist layer.

[0010] In some alternative embodiments, the PCB board undergoes character forming processing, specifically including: Silkscreen ink is used to print characters in the reserved character areas of the PCB board; A film with character graphics is attached to the character ink; The film-covered area of ​​the character ink layer is exposed and cured; By developing the PCB board, the unexposed and uncured character ink is removed, forming a character layer.

[0011] In some alternative embodiments, character ink is screen-printed in the character reserved area of ​​the PCB board, and the screen-printing pressure is 0.2 MPa-0.3 MPa; during the exposure and curing of the film-covered area of ​​the character ink layer, the exposure energy is 60 mJ / cm²-80 mJ / cm².

[0012] In some alternative embodiments, the PCB board is subjected to a thermosetting process, specifically including: The PCB board is baked at a baking temperature of 80℃-90℃ for 20min-40min to allow the character layer to be cured at a low temperature. The PCB board is subjected to a second stage of baking at a baking temperature of 150℃-160℃ and a baking time of 50min-70min to allow the character layer to be cured at high temperature.

[0013] In some alternative embodiments, when the PCB board is a reinforced flexible circuit board, a character layer is first fabricated on the reinforcing plate and the character layer is cured, and then the reinforcing plate is bonded and fixed to the flexible circuit board.

[0014] In some alternative embodiments, post-processing of the PCB board specifically includes: After dust removal, the PCB board is randomly inspected using a visual inspection device to check the clarity of characters and the smoothness of edges. If the PCB board passes the inspection, it proceeds to the next step; otherwise, the PCB board is repaired by localized reprinting and curing.

[0015] According to another aspect of the present invention, a PCB manufacturing apparatus for improving character clarity is provided, the apparatus being used to perform the above-described PCB manufacturing method for improving character clarity to manufacture a printed circuit board.

[0016] The PCB manufacturing method and apparatus for improving character clarity of the present invention have the following advantages: The present invention optimizes the entire character manufacturing process by including cleaning pretreatment, solder resist treatment, character forming treatment, thermosetting treatment and post-treatment, and solves the problems of low character clarity and many edge defects in the background technology. It not only improves the clarity and edge smoothness of printed circuit board characters, but also reduces defects such as character blurring and edge ink overflow, thereby improving the overall quality.

[0017] 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

[0018] 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 improving character clarity according to Embodiment 1 of the present invention is shown. Figure 2 A flowchart illustrating step 120 of Embodiment 2 provided by the present invention is shown; Figure 3 A flowchart illustrating step 130 of Embodiment 2 provided by the present invention is shown; Figure 4 A flowchart illustrating step 140 of Embodiment 2 provided by the present invention is shown. Detailed Implementation

[0019] 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.

[0020] Example 1: Figure 1 This paper presents a first embodiment of the PCB manufacturing method for improving character clarity according to the present invention. It addresses the problem that existing alignment accuracy is significantly affected by wear and tear during stencil manufacturing and use, easily leading to character position misalignment and ink overflow at the edges, resulting in jagged defects. Furthermore, on special materials such as thick copper plates, insufficient surface flatness results in poor adhesion between the character ink and the solder mask layer, easily causing peeling or smudging during subsequent processing.

[0021] According to one aspect of the present invention, a PCB manufacturing method for improving character clarity is provided, the method comprising: 110. Obtain the PCB board and perform a cleaning pretreatment on it. In step 110, the PCB board, or printed circuit board, is the support for electronic components and is used to realize the electrical connection between components. Its surface usually needs to be printed with characters to identify the location, model, or parameters of the components. The cleaning pretreatment refers to cleaning the surface of the PCB board before subsequent processing to remove contaminants that may affect subsequent processes, such as oxide layers, oil stains, or dust, to ensure the cleanliness of the board surface.

[0022] 120. The PCB board undergoes a solder resist treatment to create a solder resist layer on its surface. In step 120, the solder resist treatment refers to forming a layer of solder resist material, typically solder resist ink, in specific areas of the PCB board to prevent solder from short-circuiting to areas that should not be soldered during the soldering process and to protect the circuitry. The solder resist layer is a protective layer formed on the PCB board surface after the solder resist treatment. Its function is to isolate non-soldered areas, prevent solder short circuits, and provide a certain degree of insulation and protection for the circuitry.

[0023] 130. Perform character forming processing on the PCB board to create a character layer in the character reserved area of ​​the PCB board; in step 130, character forming processing refers to creating the required character graphics in the character reserved area of ​​the PCB board. These characters are usually used to identify information. The character layer is the character graphics formed in the character reserved area after character forming processing, and is usually formed by curing character ink.

[0024] 140. Perform thermosetting treatment on the PCB board to solidify and form the character layer; in step 140, thermosetting treatment refers to the process of heating to cause the resin in the character ink or solder resist ink to undergo a cross-linking reaction, thereby changing it from a liquid or semi-solid state to a solid state, forming a layer with certain mechanical strength and chemical stability.

[0025] 150. Post-processing of the PCB board. In step 150, post-processing refers to a series of processes performed in the final stage of PCB board manufacturing, such as cleaning, inspection, and repair, to ensure the quality and functionality of the final product.

[0026] In steps 110-150, during the PCB manufacturing process, the PCB board to be processed is first obtained and subjected to a cleaning pretreatment. This pretreatment aims to remove contaminants such as dust, fingerprints, oxides, or oil from the PCB board surface to ensure the adhesion and reliability of subsequent processes. The cleaning pretreatment can be implemented in ways including, but not limited to: manual wiping with a cleaning agent; mechanical scrubbing of the board surface using a scrubbing device; or solvent immersion to remove oil. This provides a clean substrate for subsequent solder mask and character forming processes.

[0027] After cleaning and pretreatment, the PCB board undergoes solder mask treatment to create a solder resist layer on its surface. The solder resist layer protects the circuitry, prevents short circuits, and provides insulation. Solder masking can be achieved, but is not limited to: uniformly spraying liquid solder resist ink onto the PCB surface using a spraying device; applying solder resist ink to the board surface using a roller coater; or using a curtain coating process, where the PCB board passes through an ink curtain to form a layer of solder resist ink on the board surface. After ink coating, preliminary drying or curing is usually required to allow the ink to form a stable film.

[0028] After the solder mask layer is fabricated, the PCB board undergoes character forming processing to create a character layer in the designated character areas. This character layer is used to identify component information, and its clarity is crucial for subsequent assembly and maintenance. Character forming processing can be achieved through methods including, but not limited to: inkjet printing technology to directly spray character ink onto the designated character areas of the PCB board; laser marking technology to form characters on the board surface through laser ablation or color change; or stencil printing to apply character ink to a specified area using a stencil. This precisely creates the desired character graphics on the PCB board.

[0029] After the character layer is fabricated, the PCB board undergoes a thermosetting process to solidify the character layer, thereby improving its adhesion, abrasion resistance, and chemical stability. Thermosetting is typically performed using heating equipment. For example, the PCB board can be placed in a constant-temperature oven and baked at a set temperature and time for a single cycle to fully cure the character ink; alternatively, infrared heating equipment can be used to radiate heat the character layer, promoting rapid curing. The curing parameters need to be adjusted according to the type of character ink used and the characteristics of the PCB board to ensure the character layer achieves the desired physical and chemical properties.

[0030] After the character layer has cured, the PCB board undergoes post-processing. This post-processing is the final step in the entire manufacturing process and aims to ensure the final quality of the product. Post-processing may include final cleaning of the PCB board, such as removing residual dust or impurities from the surface; it may also include visual inspection of the character appearance to confirm the integrity and clarity of the characters; or it may involve packaging qualified PCB boards for storage and transportation. Implementing post-processing helps improve the overall quality of the product.

[0031] This application utilizes a systematic PCB manufacturing process, including pre-treatment cleaning, solder mask treatment, character forming treatment, thermosetting treatment, and post-treatment, to effectively improve the clarity of characters on PCB boards. This method ensures board surface cleanliness, optimizes the formation of the solder mask and character layers, and ensures thorough curing. This reduces problems such as character misalignment, edge ink overflow, poor ink adhesion, and blurring, deformation, or damage caused by improper curing, which are common in traditional processes. Ultimately, it improves the printing quality and reliability of characters, meeting the production requirements for high-definition, stable characters.

[0032] Example 2: Based on Embodiment 1, the present invention provides a second embodiment of a PCB manufacturing method for improving character clarity, to further illustrate steps 110-150 in Embodiment 1.

[0033] In step 110, the PCB board undergoes a cleaning pretreatment, specifically including: Determine the type of PCB board material; When the PCB board is a rigid circuit board, it is mechanically polished with a roughness of 0.3μm-0.5μm and then ultrasonically cleaned to remove the oxide layer and oil stains on the PCB board surface. When the PCB board is a flexible circuit board, the surface of the PCB board is cleaned by plasma cleaning. When the PCB board is made of thick copper, after plasma cleaning, a leveling process is used to adjust the flatness of the PCB board.

[0034] Specifically, before performing cleaning pretreatment, it is first necessary to determine the type of PCB board. Identifying the substrate type of the PCB board is a prerequisite for implementing differentiated pretreatment. Different boards have different tolerances to mechanical stress, chemical reagents, and heat, and their surface characteristics also vary. Accurately determining the board type ensures that the most suitable cleaning method is selected, avoiding damage to the board or incomplete cleaning. This determination can be made in various ways, such as obtaining the board specifications by reading the PCB board's production batch information or bill of materials; or analyzing the surface texture, color, and other characteristics of the board using an optical recognition system; or initially distinguishing between rigid and flexible boards through simple physical tests.

[0035] When the PCB board is a rigid circuit board, the pre-treatment cleaning includes mechanical polishing with a roughness of 0.3μm-0.5μm, followed by ultrasonic cleaning, to remove the oxide layer and oil stains from the PCB board surface. Mechanical polishing is mainly used to remove the oxide layer, burrs, and some stubborn stains from the surface of the rigid circuit board. Simultaneously, by creating micro-roughness, it increases the adhesion between the board surface and subsequent coating materials. A roughness of 0.3μm-0.5μm is a key parameter, ensuring that surface defects are effectively removed without excessively damaging the substrate or leaving excessively deep scratches, thus providing an ideal adhesion base for subsequent solder mask and character layers. This polishing is typically performed using a brush polisher; the material, speed, pressure, and abrasive particle size of the brush polisher collectively determine the roughness. After mechanical polishing, fine abrasive shavings, dust, and oil stains generated during the polishing process may remain on the board surface; in this case, ultrasonic cleaning is performed. Ultrasonic cleaning utilizes high-frequency sound waves to create cavitation in the cleaning solution, forming countless tiny bubbles that rapidly burst, generating a powerful impact that peels away dirt adhering to the board surface and micropores, achieving thorough cleaning. Typically, the PCB board is immersed in an ultrasonic cleaning tank containing a specialized cleaning agent. An ultrasonic generator produces ultrasonic waves of a specific frequency, and the cleaning time usually lasts several minutes, ensuring that all residues are effectively removed.

[0036] When the PCB board is a flexible circuit board, the pre-treatment cleaning involves plasma cleaning to remove surface contaminants. Flexible circuit boards are typically thin and susceptible to mechanical damage, making traditional mechanical polishing unsuitable. Plasma cleaning is a dry cleaning technology that uses plasma to generate plasma by exciting gas in a vacuum environment. The active particles in the plasma react chemically or physically with organic contaminants on the board surface, decomposing and vaporizing them, thus achieving an ultra-clean surface treatment. Simultaneously, it activates the surface, improving the wettability and adhesion of subsequent materials, without causing mechanical stress or thermal damage to the flexible substrate. This process typically involves placing the flexible PCB board in a vacuum chamber within a plasma cleaning device, evacuating the chamber, introducing a working gas, and then exciting the gas to form plasma using an radio frequency or microwave power supply. Cleaning parameters such as gas type, flow rate, power, and processing time need to be optimized based on the specific material and degree of contamination of the flexible board.

[0037] When the PCB board is made of thick copper, the pre-treatment cleaning process, after plasma cleaning, involves a leveling process to adjust the flatness of the PCB board. Thick copper boards may also have oxide layers and organic contaminants on their surface. Plasma cleaning effectively removes these microscopic contaminants, activates the copper surface, and provides a good adhesion base for subsequent solder mask and character layers. Similar to flexible boards, plasma cleaning avoids potential chemical corrosion or mechanical damage to the thick copper layer. Due to the thicker copper layer, thick copper boards are more prone to localized unevenness or warping during manufacturing, which can affect the uniformity and clarity of subsequent screen-printed characters. The leveling process aims to eliminate these microscopic or macroscopic unevennesses, ensuring a high degree of flatness on the PCB board surface, providing a flat base for character screen printing, thereby guaranteeing the printing quality and clarity of the characters. Leveling can be performed using methods such as mechanical rolling, hot pressing, or vacuum adsorption.

[0038] Through the above technical solutions, the most suitable surface treatment process can be intelligently selected and implemented according to the type of PCB board during the cleaning pretreatment stage of PCB manufacturing. Specifically, for rigid circuit boards, mechanical grinding combined with ultrasonic cleaning can efficiently remove stubborn oxide layers and oil stains, while creating a suitable surface roughness, significantly enhancing the adhesion of subsequent solder mask and character layers. For flexible circuit boards, gentle yet efficient plasma cleaning avoids mechanical damage, ensuring surface cleanliness and activation effects. For thick copper boards, after plasma cleaning, further leveling treatment eliminates any potential surface unevenness. This targeted pretreatment strategy effectively solves the problem of incomplete cleaning or surface damage caused by differences in board materials, greatly optimizing the surface condition of the PCB board and providing an ideal substrate for subsequent character forming. Ultimately, this allows the character ink to adhere more evenly and firmly to the PCB board, significantly improving the printing clarity, edge smoothness, and overall durability of the characters, thereby enhancing the quality and reliability of the PCB product.

[0039] In the above steps, the leveling process specifically includes: rolling and leveling the PCB using a leveling device to ensure that the flatness error of the PCB board is ≤0.02mm; and then placing the PCB into a baking equipment for drying at a drying temperature of 60℃-80℃ for 15-20 minutes.

[0040] Specifically, a leveling device is a tool used to physically correct surface unevenness of a PCB board. Roll leveling is a mechanical processing method that deforms the PCB board by applying pressure, thereby achieving the desired flatness. This leveling device may include one or more pairs of high-precision rollers. The PCB board passes between the rollers, and the PCB board is uniformly rolled by adjusting the gap between the rollers and the applied pressure. To ensure that the flatness error of the PCB board is ≤0.02mm, the leveling device is usually equipped with a high-precision displacement sensor or laser measurement system to monitor the flatness of the PCB board in real time and adjust the rolling parameters based on the feedback signal. For example, a precision roller system driven by a servo motor can be used to achieve micron-level flatness control of the PCB board by precisely controlling the roller speed and spacing. Furthermore, the material properties of the PCB board, such as the elastic modulus and yield strength, need to be considered during the rolling process to avoid excessive deformation or damage.

[0041] The PCB is then placed in a baking device for drying. This device is used to dry the rolled and leveled PCB. The purpose of drying is to remove any residual moisture or other volatile substances from the surface or interior of the PCB, which can cause defects in subsequent processes, such as bubbles, delamination, or affecting ink adhesion. Baking equipment is typically an oven or tunnel furnace with precise temperature control. Drying within a temperature range of 60°C-80°C effectively removes moisture while avoiding excessive heat stress or deformation of the PCB material. A drying time of 15-20 minutes is an empirical value determined based on factors such as PCB thickness, material type, and ambient humidity, aiming to ensure thorough drying. The baking equipment should maintain a uniform temperature and have good dehumidification capabilities to prevent condensation. For example, a forced convection oven can be used, with a fan circulating hot air within the oven to ensure uniform heating of all parts of the PCB and accelerate moisture evaporation.

[0042] The above technical solution employs a leveling device to precisely roll and level the PCB board, strictly controlling the flatness error to ≤0.02mm. This effectively eliminates warping, unevenness, or localized stress that may occur during the manufacturing process of thick copper plates, providing a highly flat and uniform substrate for subsequent solder resist processing and character molding. Following this, the PCB board is placed in a baking device and dried at 60℃-80℃ for 15-20 minutes. This thoroughly removes any trace moisture or surface residue that may have been introduced during the rolling process, ensuring a clean and dry PCB surface. This significantly improves the adhesion, leveling properties, and curing uniformity of the solder resist and character inks. This refined combination of leveling and drying not only lays a solid foundation for character clarity but also avoids problems such as blurred, broken, or uneven edges caused by uneven board surfaces, ultimately ensuring high-definition characters and excellent visual effects on the PCB board.

[0043] In step 120, see Figure 2 Solder resist treatment is applied to the PCB board, specifically including: 210. Screen printing solder resist ink onto the surface of the PCB board; In step 210, liquid solder resist ink is uniformly coated onto the entire surface of the PCB board using screen printing technology, providing a base material for the subsequent formation of the solder resist layer. During the screen printing process, parameters such as ink viscosity, screen mesh count, squeegee pressure, and speed must be precisely controlled to ensure uniform ink layer thickness, no bubbles, and no missed printing, thus providing a good foundation for subsequent exposure and development.

[0044] Step 220 involves pre-curing the solder resist ink on the PCB board at a baking temperature of 100℃-120℃ for 20-30 minutes. In step 220, the aim is to allow the solvent in the screen-printed solder resist ink to fully evaporate and to achieve a certain viscosity and hardness for subsequent exposure operations. Baking within the set temperature and time range ensures that the ink layer forms a stable film without over-curing, effectively preventing problems such as dripping, deformation, or insufficient adhesion in subsequent operations. This is crucial for improving the uniformity and stability of the solder resist layer.

[0045] 230. For non-character reserved areas and non-wire patch areas on the PCB board surface, exposure energy of 80 mJ / cm²-100 mJ / cm² is used for curing. In step 230, ultraviolet (UV) light is used to irradiate the photosensitive solder resist ink, causing it to undergo a photopolymerization reaction and cure. A preset photomask (e.g., film) is used to expose only the non-character reserved areas and non-wire patch areas on the PCB board surface. Precise control of the exposure energy within the range of 80 mJ / cm²-100 mJ / cm² aims to ensure that the solder resist ink in these areas is fully cured, forming a hard, corrosion-resistant solder resist layer. Precise exposure energy helps ensure the clarity of the solder resist pattern and the sharpness of its edges, avoiding defects caused by underexposure or overexposure.

[0046] 240. By developing the PCB board, the ink on the unexposed and uncured character reservation areas and circuit surface mount areas is removed to form a solder resist layer. In step 240, a specific developer is used to dissolve and remove the unexposed and uncured solder resist ink on the PCB board. During the exposure step, the character reservation areas and circuit surface mount areas are blocked by a photomask and are not exposed to ultraviolet light, so the ink in these areas remains uncured. Through development, this uncured ink is selectively removed, thereby exposing the underlying copper foil or substrate and forming a solder resist layer with precise patterns. This step is crucial for forming a clear solder resist pattern and directly affects the accuracy of the character reservation areas and circuit surface mount areas.

[0047] In steps 210-240, the aforementioned refined solder resist processing scheme ensures a highly controllable solder resist layer formation process on the PCB board. This includes uniform coating of screen printing ink, precise control of temperature and time for initial curing, accurate exposure energy control for non-character reserved areas and non-line surface mount areas, and final development processing. This effectively solves problems such as blurred edges and uneven thickness in traditional solder resist processes, significantly improving the accuracy and stability of the solder resist pattern. Consequently, it provides a flat, clear, and well-defined substrate for subsequent character layer fabrication, thus guaranteeing the clarity and overall aesthetics of the characters on the PCB board.

[0048] In step 130, see Figure 3 The PCB board undergoes character forming processing, specifically including: 310. Screen printing character ink onto the reserved character area on the PCB board; in step 310, the aim is to precisely coat the reserved area on the PCB board for displaying characters with photosensitive character ink. The screen printing process uses a squeegee to evenly press the ink across the screen with the character pattern, allowing it to penetrate the PCB board surface. Parameters such as screen printing pressure, screen mesh count, and ink viscosity must be strictly controlled to ensure uniform ink layer thickness and no missed printing or clogging, laying the foundation for subsequent character forming.

[0049] 320. Attach the film with the character graphic onto the character ink; in step 320, the film serves as a photomask, on which the desired character graphic is precisely etched. It is then tightly attached to the surface of the PCB board with the screen-printed character ink, ensuring there are no air bubbles or gaps between the film and the ink layer to avoid light scattering during exposure, thereby guaranteeing the clarity and accuracy of the character graphic.

[0050] 330. Exposure and curing are performed on the film-covered area of ​​the character ink layer. In step 330, ultraviolet light irradiation causes the character ink below the transparent area of ​​the film to undergo a photopolymerization reaction and cure. Exposure energy and exposure time are key parameters and need to be precisely set according to the characteristics of the ink used and the thickness of the ink layer to ensure that the ink in the character graphic area is fully cured, while the ink in the film-masked area remains uncured.

[0051] 340. The PCB board is developed to remove uncured character ink and form a character layer. In step 340, the development process typically uses a specific developer to selectively dissolve and wash away the character ink on the PCB board that has not been cured by ultraviolet light. After development, rinsing, and drying, only a cured and precisely shaped character layer remains on the PCB board, with clear edges and complete graphics.

[0052] In steps 310-340, the above-described technical solution utilizes photolithography to selectively cure and develop the character ink, effectively solving problems such as blurred character edges and graphic distortion in traditional character forming. This method ensures the formation of a high-definition, smooth-edge, and accurately graphic character layer in the reserved character area of ​​the PCB board, significantly improving the readability and overall aesthetics of the characters on the PCB board. This not only provides clear and reliable identification information for subsequent assembly, testing, and maintenance but also improves product quality and reliability.

[0053] In the above steps, character ink is screen-printed in the reserved area of ​​the PCB board, and the screen-printing pressure is 0.2Mpa-0.3Mpa; in the exposure and curing of the film-covered area of ​​the character ink layer, the exposure energy is 60mJ / cm²-80mJ / cm².

[0054] Specifically, screen printing pressure refers to the force applied by the squeegee to the screen during the screen printing process. This pressure directly affects the amount and uniformity of ink transferred from the screen to the designated character area on the PCB board. Controlling the screen printing pressure within the range of 0.2 MPa to 0.3 MPa ensures that the ink adheres to the PCB surface with appropriate thickness and uniformity. If the pressure is too low, insufficient ink transfer may result in broken or blurred characters; if the pressure is too high, excessive ink diffusion may occur, leading to blurred character edges or even damage to the screen or PCB board. Therefore, this pressure range helps to form a uniformly thick ink layer with clear edges.

[0055] Exposure energy refers to the energy density of ultraviolet light irradiating the character ink layer during the exposure curing process. This energy is a key parameter for initiating the polymerization reaction of photosensitive ink. Controlling the exposure energy within the range of 60mJ / cm²-80mJ / cm² ensures that the character ink layer is fully and appropriately cured. If the exposure energy is insufficient, the character ink may not cure completely, leading to character detachment or uneven edges during development; if the exposure energy is too high, it may cause over-curing of the ink, making the character layer brittle and prone to cracking, or reducing its adhesion to the substrate, and may also damage the film. This energy range aims to achieve complete polymerization of the character ink, thereby forming a character layer with a stable structure, strong adhesion, and sharp edges.

[0056] Through the above technical solution, when performing character forming on a PCB board, precisely controlling the screen printing pressure of the ink within the range of 0.2 MPa to 0.3 MPa ensures that the ink is deposited evenly and appropriately in the designated character areas on the PCB board, preventing ink accumulation or loss due to improper pressure and laying a solid foundation for subsequent character forming. Simultaneously, when exposing and curing the film-covered area of ​​the ink layer, precisely setting the exposure energy between 60 mJ / cm² and 80 mJ / cm² ensures that the ink can fully and evenly polymerize and cure, preventing both blurring or peeling due to insufficient exposure and embrittlement or decreased adhesion due to overexposure. Through the synergistic optimization and control of these two key parameters, this application significantly improves the clarity, edge smoothness, and overall stability of the produced characters, making the markings on the PCB board clearer and more legible, meeting the manufacturing requirements of high-reliability electronic products.

[0057] In step 140, see Figure 4 The PCB board undergoes thermosetting treatment, specifically including: 410. The PCB board is baked at a baking temperature of 80℃-90℃ for 20min-40min to allow the character layer to be cured at a low temperature. 420, the PCB board is baked in a second stage at a baking temperature of 150℃-160℃ and a baking time of 50min-70min to allow the character layer to be cured at high temperature.

[0058] In steps 410-420, thermosetting is a crucial step in PCB manufacturing. Its purpose is to induce a cross-linking reaction in the resin within the character ink through heating, transforming the liquid or semi-solid ink into a hard, wear-resistant, and highly adhesive solid character layer. This process directly impacts the physicochemical properties of the character layer and the final visual effect. The first baking stage aims to cure the character layer on the PCB at a low temperature. During this stage, a relatively low baking temperature (e.g., 80℃-90℃) and a short baking time (e.g., 20min-40min) are used. The main purpose is to allow the solvent in the character ink to evaporate slowly and initiate a preliminary cross-linking reaction, thus initially shaping the character layer. Low-temperature curing gently removes volatile components from the ink, reducing internal stress in the ink layer caused by rapid solvent evaporation. This effectively prevents cracking, blistering, or decreased adhesion during subsequent high-temperature processing, helping to maintain the integrity and flatness of the character layer and avoiding defects such as ink flow, deformation, or bubble formation caused by sudden temperature changes, laying the foundation for subsequent high-temperature curing.

[0059] The subsequent second-stage baking, performed after the first low-temperature curing, aims to cure the character layer at a high temperature. In this stage, a higher baking temperature (e.g., 150℃-160℃) and a longer baking time (e.g., 50min-70min) are used to further accelerate the cross-linking reaction of the ink resin, allowing the character layer to reach a fully cured state. High-temperature curing ensures that all active components in the character ink react fully, forming a dense cross-linked network structure. This imparts excellent mechanical properties and environmental stability to the character layer, enabling it to withstand various stresses during subsequent assembly, use, and maintenance, and maintain a clear and stable visual effect over a long period. It also significantly improves the character layer's hardness, abrasion resistance, chemical corrosion resistance, and adhesion to the PCB board.

[0060] The above technical solution divides the thermosetting process of the character layer into two stages: low-temperature curing and high-temperature curing. First, a low-temperature baking process is performed at 80℃-90℃ for 20-40 minutes. This stage gently removes solvents from the character ink, preventing ink defects caused by rapid heating, and allowing the character layer to initially set and enhancing its internal structural stability. Then, a second stage of high-temperature curing is performed at 150℃-160℃ for 50-70 minutes. This stage ensures that the character ink is fully cross-linked, forming a dense and robust character layer. This segmented thermosetting strategy effectively solves problems such as uneven curing, poor adhesion, or blurred characters that may result from a single curing method. By using a gradual curing process—first low temperature and then high temperature—not only can the deformation and defects of the character layer during curing be minimized, but the hardness, wear resistance, chemical corrosion resistance, and bonding strength with the PCB board of the character layer can also be significantly improved, ensuring that the characters on the final PCB board have higher clarity, smoother edges, and more durable stability.

[0061] In some alternative implementations, when the PCB board is a reinforced flexible circuit board, a character layer is first fabricated on the reinforcing plate and then cured. The reinforcing plate is then bonded and fixed to the flexible circuit board.

[0062] Specifically, when the PCB is a reinforced flexible circuit board, it refers to a special type of printed circuit board structure. Flexible printed circuit boards (FPCs) themselves have excellent bending and folding capabilities, making them suitable for electronic products requiring miniaturization, lightweight design, and three-dimensional space utilization. The stiffener is a rigid material, such as FR-4, polyimide (PI), or a metal plate, added to provide additional mechanical support in specific areas of the flexible circuit board, increase thickness to match connector height, or improve heat dissipation. During the manufacturing process of this composite structure, the differences in material properties between the flexible circuit board and the stiffener place higher demands on the character layer fabrication process.

[0063] This application proposes to fabricate the character layer on the reinforcing plate first. This means that the various fabrication processes of the character layer are completed independently on the surface of the reinforcing plate before it is bonded to the flexible circuit board. The fabrication of the character layer typically includes steps such as screen printing character ink, attaching a film with the character graphic attached, exposing and curing the character ink layer, and subsequent development processing. Fabricating the character layer on a reinforcing plate with rigidity, flatness, and dimensional stability provides an ideal and stable substrate for the accurate screen printing and exposure of the character ink, thereby ensuring the fineness, edge smoothness, and overall clarity of the character graphic.

[0064] Subsequently, the character layer undergoes a curing process. This step involves heat-curing the character layer on the reinforcing board according to the baking temperature and time specified above after the character layer is fabricated. The purpose of the curing process is to promote the full cross-linking and polymerization of the resin components in the character ink, forming a strong, wear-resistant, and highly adhesive character layer. Because the character layer is cured on an independent reinforcing board at this stage, the flexibility of the flexible circuit board can be prevented from adversely affecting the character layer due to thermal stress or deformation during the curing process. This ensures that the character layer is fully cured under optimal conditions, thereby significantly improving the durability and scratch resistance of the characters.

[0065] Finally, the reinforcing plate is bonded and secured to the flexible circuit board. This step, performed after the character layer on the reinforcing plate has been fabricated and cured, involves precise alignment and appropriate bonding, pressing, or other connection processes to firmly secure the reinforcing plate with its high-quality character layer to the designated area of ​​the flexible circuit board. Since the character layer has been completed and cured before bonding, this subsequent bonding and securing step will not negatively affect the integrity, clarity, or adhesion of the character layer.

[0066] By employing the aforementioned technical solution, the character layer fabrication and curing process is transferred from the flexible circuit board to a more rigid and stable reinforcing board. This effectively avoids potential deformation issues that may occur on the flexible circuit board during character fabrication and curing, thereby significantly improving the screen printing accuracy and exposure effect. Curing the character layer on the reinforcing board ensures that the character layer forms under optimal conditions, resulting in stronger adhesion, abrasion resistance, and clarity. Subsequently, the reinforcing board with the high-quality character layer is bonded to the flexible circuit board, avoiding potential damage to the formed characters in subsequent bonding processes. This simplifies the overall manufacturing process and ultimately guarantees that the characters on the reinforced flexible circuit board possess excellent clarity, smooth edges, and long-term reliability.

[0067] In step 150, the PCB board is post-processed, specifically including: after dust removal, the PCB board is randomly inspected by a visual inspection device to check the clarity of characters and the smoothness of edges. If the PCB board passes the inspection, it proceeds to the next step; otherwise, the PCB board is repaired by local reprinting and curing.

[0068] Specifically, the dust removal process aims to remove dust, fibers, or other particulate matter that may have adhered to the PCB board surface during production, ensuring a clean PCB board surface and providing a good foundation for subsequent accurate inspection and repair operations. This process can be achieved in various ways. For example, high-pressure airflow can be used to blow loose dust particles away from the PCB board surface; or a sticky roller can be used for contact cleaning, adsorbing fine particles through an adhesive surface; or electrostatic dust removal technology can be used to remove charged dust using the principle of electrostatic adsorption.

[0069] Subsequently, the PCB boards are randomly inspected using visual inspection equipment. This equipment typically consists of a high-resolution industrial camera, a light source, an image acquisition system, and image processing software. The equipment automatically captures high-definition images of the character areas on the PCB board and analyzes the images using a preset image recognition algorithm. The inspection primarily focuses on character clarity and edge smoothness. Character clarity refers to the integrity and contrast of character strokes, as well as the presence of defects such as blurriness, breaks, or missing parts, ensuring the readability of the character information. Edge smoothness focuses on the flatness of the edges of characters or solder mask layers, avoiding burrs, jagged edges, or irregular edges that affect the appearance quality and reliability of the PCB board. The sampling ratio and rules can be flexibly configured according to production batches, product importance, or quality control requirements.

[0070] When the PCB board is deemed qualified by the visual inspection equipment, that is, the character clarity and edge smoothness both meet the preset standards, the PCB board will smoothly enter the subsequent production steps, such as final testing, packaging or assembly, thereby ensuring the smooth progress of the production process.

[0071] Otherwise, if the visual inspection equipment detects character defects or uneven edges on the PCB board, a repair process will be initiated. This repair process is performed through localized reprinting and curing. Specifically, the system accurately identifies and locates the defective area, and then uses a high-precision inkjet printhead or a micro-screen printing device to precisely reprint character ink onto the defective area. After reprinting, the localized area is then cured, for example, by using ultraviolet (UV) light irradiation or localized heating, causing the reprinted character ink to quickly solidify and form a solid shape, thereby repairing the character defects and bringing it up to quality standards.

[0072] The above technical solution involves effective dust removal after character forming and curing on the PCB board to ensure a clean testing environment. Subsequently, automated visual inspection equipment performs high-precision and high-efficiency inspections on the character clarity and edge smoothness of the PCB board, enabling timely detection of potential character defects during production. PCB boards that pass inspection can quickly proceed to subsequent production stages, ensuring production efficiency. PCB boards with detected character defects are not directly scrapped but undergo precise repair through localized reprinting and curing, effectively compensating for localized defects in the character layer and bringing them up to quality standards. This targeted repair mechanism significantly improves the overall yield of PCB boards, reduces the scrap rate due to localized defects, effectively saves production costs, and ensures the character quality and reliability of the finished products.

[0073] Example 3: According to another aspect of the present invention, a PCB manufacturing apparatus for improving character clarity is provided. This apparatus is used to perform the PCB manufacturing method for improving character clarity described in Embodiment 1 or Embodiment 2 to manufacture a printed circuit board.

[0074] In one example, the PCB is a rigid circuit board. Character fabrication includes the following steps: A standard FR-4 rigid circuit board is selected as the substrate, and the following steps are followed: Pre-treatment: After sanding the board surface, it is placed in an ultrasonic cleaning tank. A neutral cleaning agent is used, and the cleaning time is 10 minutes. The drying temperature is 70℃, and the time is 18 minutes. Layered solder mask: After screen printing solder mask ink, it is pre-baked at 110℃ for 25 minutes. The exposure energy is 90mJ / cm² to complete the zoned solder mask exposure. After development, the character pre-reserved area is exposed. Character forming: After screen printing character ink, a film is attached, exposed at 70mJ / cm², and after development, the formed character is obtained. Segmented curing: Low-temperature curing at 85℃ for 30 minutes, and high-temperature curing at 155℃ for 60 minutes. Post-treatment: After cleaning and inspection, the character clarity meets the standard, there is no blurring or ink overflow at the edges, and the character blurring defect rate is reduced from 8% in traditional processes to below 0.5%.

[0075] In another example, the PCB board is a reinforced flexible circuit board with character fabrication, specifically including: Reinforcement board processing: After the reinforcement board is cut, it is drilled, cleaned, and the characters are screen-printed, exposed, developed, and cured in sections according to the character forming steps described above; Flexible board processing: The flexible board is cleaned before the reinforcement is attached, and the characters in its own area are screen-printed and cured; Lamination and curing: The reinforced board with characters is precisely laminated to the flexible board, with a pressing pressure of 0.3MPa, a pressing temperature of 120℃, and a time of 20 minutes; Inspection and shipment: After inspection, the characters at the joint between the reinforcement board and the flexible board are not squeezed or blurred, and the defect rate is reduced to 0.3%.

[0076] In this embodiment of the invention, the above-described solution significantly improves the character blurring problem. Through film alignment and layered exposure, the character edge precision is improved to the 0.01mm level, and even small characters (≤0.1mm) can be clearly formed. The character ink adheres firmly to the circuit board, and after high and low temperature cycling tests (-40℃ to 125℃, 50 cycles), there is no peeling or blurring. It is compatible with various circuit board types, has strong versatility, and improves production efficiency by 20%-35% compared to traditional processes. The character production defect rate is reduced from the traditional 5%-10% to below 0.5%. The process steps are clear and can be adapted to existing circuit board production lines without large-scale equipment modifications, thus reducing production modification costs.

[0077] 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.

[0078] 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.

[0079] 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 method for improving character definition in PCB fabrication, comprising: The method comprises: acquiring a PCB board and performing cleaning pretreatment on the PCB board; performing solder mask treatment on the PCB board to make a solder mask layer on the surface of the PCB board; performing character forming treatment on the PCB board to make a character layer on the character reserved area of the PCB board; performing heat curing treatment on the PCB board to make the character layer cured and formed; performing post-treatment on the PCB board.

2. The method of claim 1, wherein the method further comprises: The cleaning pretreatment on the PCB board specifically comprises: judging the board material type of the PCB board; when the board material type of the PCB board is rigid circuit board, performing mechanical polishing with a polishing roughness of 0.3-0.5 μm and then performing ultrasonic cleaning to remove the oxidation layer and oil stains on the surface of the PCB board; when the board material type of the PCB board is flexible circuit board, performing surface cleaning on the PCB board by plasma cleaning; when the board material type of the PCB board is thick copper board, performing leveling treatment to adjust the flatness of the PCB board after plasma cleaning.

3. The method of claim 2, wherein the method further comprises: The leveling treatment specifically comprises: performing roller leveling on the PCB by a leveling device to make the flatness error of the PCB board less than or equal to 0.02 mm; then placing the PCB into a baking equipment to perform drying treatment at a drying temperature of 60-80 °C and a drying time of 15-20 min.

4. The PCB manufacturing method for improving character definition according to claim 1, wherein the solder mask treatment on the PCB board specifically comprises: screen printing solder mask ink on the surface of the PCB board; performing preliminary curing of the solder mask ink on the PCB board at a baking temperature of 100-120 °C and a baking time of 20-30 min; exposing and curing the non-character reserved area and the non-circuit patch area on the surface of the PCB board at an exposure energy of 80-100 mJ / cm²; performing developing treatment on the PCB board to remove the ink on the surface of the non-exposed and cured character reserved area and circuit patch area, thereby forming a solder mask layer.

5. The method of claim 4, wherein the method further comprises: The character forming treatment on the PCB board specifically comprises: screen printing character ink on the character reserved area of the PCB board; attaching a film with character patterns on the character ink; exposing and curing the film covered area of the character ink layer; performing developing treatment on the PCB board to remove the non-exposed and cured character ink, thereby forming a character layer.

6. The method of claim 4, wherein the method further comprises: The screen printing pressure of the character ink on the character reserved area of the PCB board is 0.2-0.3 MPa, and the exposure energy of the film covered area of the character ink layer during the exposure and curing is 60-80 mJ / cm².

7. The method of claim 5, wherein the method further comprises: The heat curing treatment on the PCB board specifically comprises: performing first baking on the PCB board at a baking temperature of 80-90 °C and a baking time of 20-40 min to make the character layer cured at low temperature; performing second baking on the PCB board at a baking temperature of 150-160 °C and a baking time of 50-70 min to make the character layer cured at high temperature.

8. The method of claim 7, wherein the method further comprises: When the PCB is a flexible circuit board with reinforcement, the character layer is first made on the reinforcement plate, and the character layer is cured, and then the reinforcement plate is fixed with the flexible circuit board.

9. The method of claim 1, wherein the method further comprises: The PCB is post-processed, specifically including: After the dust removal treatment of the PCB, the PCB is sampled and inspected by a visual inspection device to detect the character definition and edge smoothness of the PCB. When the PCB passes the detection, it proceeds to the next step, otherwise it is repaired by local re-inking and curing.

10. A PCB manufacturing apparatus for improving character legibility, characterized by comprising: The device is used to perform the PCB manufacturing method for improving character definition according to any one of claims 1-9 to manufacture a printed circuit board.

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