Manufacturing method of circuit board solder bridge and circuit board

Abstract

The invention provides a manufacturing method of a circuit board resistance welding bridge and a circuit board, and the manufacturing method comprises the following steps: carrying out the laser processing of a preset design region of the resistance welding bridge on a substrate to form a groove structure, the width of the groove structure is smaller than the preset design width of the resistance welding bridge, and the depth of the groove structure is 5-10 microns; removing residues generated by laser processing on the substrate; solder resist ink is applied to the design area, and the groove structure is filled with the solder resist ink to form a solder resist bridge with a step difference. A groove structure with specific width and depth is formed by performing laser processing on a design area of a preset solder resist bridge on a substrate, and residues generated by laser processing on the substrate are removed before solder resist ink is applied, so that a step difference is formed between the bottom of a subsequently formed solder resist bridge and the surface of the substrate due to the fact that the groove is filled. The problems of insufficient adhesive force, falling, floating, lateral erosion and the like caused by the fact that the bottom of the fine solder resist bridge and a substrate are located on the same horizontal line and are easy to permeate and erode by liquid medicine are solved.

Description

Technical Field

[0001] This invention relates to the field of circuit board manufacturing technology, and in particular to a method for manufacturing solder mask bridges for circuit boards and a circuit board thereof. Background Technology

[0002] In the field of printed circuit board (PCB) manufacturing, the solder mask is a critical cover layer that protects circuit patterns and prevents solder short circuits. Especially in the packaging areas of high-density wiring and fine-pitch devices (such as IC chips), narrow solder mask bars, or solder mask bridges or solder damage, need to be formed between adjacent pads to isolate the pads and prevent solder bridging and short circuits during soldering.

[0003] However, as electronic products move towards miniaturization and high integration, the requirements for the precision and reliability of solder mask bridges are becoming increasingly stringent. This is especially true when processing fine solder mask bridges with widths of 50 to 100 micrometers or even narrower, where existing technologies face numerous challenges:

[0004] The adhesion between solder mask bridges and the substrate has long been a challenge. Traditional solder mask bridges are formed directly on the flat substrate surface, with their bottom surface typically at the same level as the substrate. During subsequent development, the developing solution has a certain degree of aggression and penetrability, easily causing lateral erosion along the interface between the solder mask bridge and the substrate. This erosion weakens the adhesion of the solder mask bridge's bottom, and in severe cases, can lead to defects such as detachment, lifting, warping, or lateral etching, directly affecting the soldering quality and long-term reliability of the product. Especially when using mixed-color inks (such as black or white inks) or processing PCBs with thicker copper layers (e.g., ≥35 micrometers), the adhesion requirements for solder mask bridges are even more stringent due to differences in ink characteristics and copper thickness, making the aforementioned defects more likely to occur.

[0005] To improve the adhesion of solder mask bridges, several solutions have been proposed in the prior art. For example, Chinese patent application CN112911820A discloses a method for fabricating a solder mask layer on a circuit board. The core of this method is to perform an ultra-roughening treatment on the surface of the substrate to which the solder mask layer is to be formed, such as by chemical etching or mechanical polishing, to increase the surface roughness of the substrate, thereby improving the adhesion between the substrate surface and the subsequently formed solder mask layer. The aim is to reduce the degree of side etching during development and the risk of solder mask bridge detachment.

[0006] However, the technical solution disclosed in CN112911820A mainly enhances physical adhesion by increasing the overall roughness of the substrate surface. Although the ultra-roughening treatment can increase the bonding area and mechanical locking force between the solder resist ink and the substrate, it primarily improves the adhesion in the vertical direction. For the lateral penetration and erosion of the developing solution along the interface between the solder resist bridge and the substrate, this overall surface roughening treatment provides limited protection. The developing solution will still gradually penetrate along the roughened interface, and especially for long-term developing processes or highly aggressive developing solutions, it is still difficult to completely avoid side etching or bottom hollowing.

[0007] Therefore, it is necessary to improve the existing technologies related to the manufacturing of weld bridges in order to overcome the shortcomings of the existing technologies. Summary of the Invention

[0008] To overcome the problems existing in related technologies, one of the objectives of this invention is to provide a method for manufacturing solder mask bridges on circuit boards. This method involves laser processing a predetermined design area for the solder mask bridge on a substrate to form a groove structure with a specific width and depth. Before applying solder mask ink, residues generated during laser processing on the substrate are removed. This results in the bottom of the subsequently formed solder mask bridge filling the groove, creating a stepped difference between the bottom and the substrate surface. This overcomes the problems in existing technologies where fine solder mask bridges, due to their bottom being at the same level as the substrate, are easily penetrated and eroded by developing chemicals, leading to insufficient adhesion, detachment, lifting, and lateral etching.

[0009] A method for manufacturing solder mask bridges on a circuit board, the circuit board comprising a substrate, the manufacturing method comprising the following steps:

[0010] Laser processing is performed on the design area of ​​the predetermined solder mask bridge on the substrate to form a groove structure. The width of the groove structure is smaller than the design width of the predetermined solder mask bridge, and the depth of the groove structure is 5 micrometers to 10 micrometers.

[0011] Remove residues generated during laser processing from the substrate;

[0012] Solder resist ink is applied to the designed area, and the solder resist ink fills the groove structure to form a solder resist bridge with a stepped difference.

[0013] Furthermore, the width of the groove structure is 5 to 15 micrometers narrower than the design width of the predetermined solder mask bridge.

[0014] This ensures that after the solder resist ink fills the groove, it has sufficient contact area with the substrate surface on both sides of the groove to form an effective "anchor point," which further enhances the adhesion and resistance to lateral peeling of the solder bridge, making the stepped differential structure more stable and improving the mechanical strength and chemical corrosion resistance of the solder bridge.

[0015] Furthermore, along the width direction of the groove structure, the distance between the top edge of the opening of the groove structure and the edge of the predetermined solder mask bridge is 2.5 μm to 10 μm.

[0016] This ensures that even with some misalignment, the solder mask bridge can effectively cover and anchor to the substrate at the edge of the groove, rather than being suspended or only partially in contact. This effectively guarantees the structural integrity and adhesion stability of the solder mask bridge, especially when processing small solder mask bridges, and can more effectively prevent defects caused by insufficient overlap.

[0017] Furthermore, the length of the groove structure covers the design length of the predetermined weld bridge, and extends outward by a predetermined distance at both ends of the design length of the predetermined weld bridge.

[0018] By extending the length of the groove structure beyond the predetermined design length of the weld resist bridge to both ends, the effects of alignment errors or ink flow during processing can be effectively compensated. This ensures that a stable step difference and anchoring structure can be formed at both ends of the weld resist bridge, preventing the weld resist bridge ends from peeling or lifting due to lack of effective support. This improves the integrity and adhesion reliability of the entire weld resist bridge.

[0019] Furthermore, the preset distance is 0.1 mm.

[0020] The preset distance for extending outward from both ends of the groove is specifically limited to 0.1 mm, providing an optimized parameter that can effectively compensate for processing errors and ensure the adhesion of the solder bridge ends, while avoiding unnecessary circuit board space occupation or adverse effects on adjacent wiring due to excessive extension, thus achieving a good balance between enhancement effect and space utilization.

[0021] Furthermore, the laser processing is either carbon dioxide laser processing or UV laser processing.

[0022] These two types of lasers are mature applications in the PCB industry, enabling precise and efficient processing of substrate materials. They allow for easy control of the depth and shape of the grooves, and the heat-affected zone is relatively small, which helps ensure processing quality and compatibility with subsequent processes.

[0023] Furthermore, the groove structure includes a plurality of cylindrical grooves arranged along its length, the cylindrical grooves being tangent to each other.

[0024] By using a groove structure composed of several mutually tangent cylindrical grooves, and taking advantage of the processing characteristics of laser point-by-point scanning, it is not only easy to design and implement precisely through laser engineering files, but also the microscopic wavy or serrated sidewalls and bottom of this groove can further increase the contact surface area between the solder resist ink and the substrate compared to a smooth groove, providing more mechanical locking points, thereby significantly improving the adhesion and shear resistance of the solder bridge.

[0025] Furthermore, the step of removing the residue generated by laser processing on the substrate is performed using a film stripping process.

[0026] Removing residues from laser processing on the substrate using a stripping process is a highly efficient and targeted cleaning method. This process effectively peels off or dissolves carbides, slag, and other contaminants adhering to the substrate surface and grooves after laser ablation, ensuring the cleanliness of the grooves and providing ideal interface conditions for subsequent filling and curing of solder resist ink. It avoids reduced adhesion or solder resist defects caused by residue isolation, significantly improving the quality and reliability of the solder resist bridge.

[0027] Furthermore, the film removal process includes chemical dissolution and physical stripping of toner and particulate contaminants.

[0028] Combining chemical dissolution and physical stripping mechanisms in the stripping process enables a more thorough and comprehensive removal of laser processing residues of various properties. Chemical dissolution effectively removes soluble organic matter or inorganic salt contaminants, while physical stripping (such as ultrasonic cleaning and high-pressure spray-assisted methods) effectively removes firmly attached carbon particles and micro-debris. This composite cleaning mechanism ensures effective cleaning and avoids the limitations that may exist with a single cleaning method, thereby maximizing the bonding strength between the solder mask bridge and the substrate and the purity of the interface.

[0029] A second objective of this invention is to provide a circuit board, comprising a substrate and solder mask bridges formed on the substrate.

[0030] The substrate has a groove structure at a corresponding position below the solder mask bridge. The width of the groove structure is smaller than the width of the solder mask bridge, and the depth of the groove is 5 micrometers to 10 micrometers.

[0031] The solder resist ink of the solder bridge is filled within the groove structure;

[0032] The bottom of the solder resist bridge and the surface of the substrate are separated by a stepped difference through the wall of the groove.

[0033] This circuit board features a groove structure of a specific size on the substrate beneath the solder mask bridge. The solder mask ink fills this groove, creating a stepped difference that results in a strong physical bond between the solder mask bridge and the substrate. This significantly enhances the adhesion of the solder mask bridge and effectively prevents it from detaching, floating, or breaking due to stress, temperature changes, or chemical corrosion during subsequent processing, soldering, or long-term use. This structural design improves the overall reliability and durability of the circuit board, especially for high-density, fine-pitch circuit boards, ensuring the stability of electrical connections and the long-term performance of the product.

[0034] The beneficial effects of this invention are as follows:

[0035] This invention provides a method for manufacturing solder mask bridges for circuit boards. This method involves pre-laser processing to form a groove structure of a specific size at the bottom of the solder mask bridge, and then creating a stepped difference after ink filling. This significantly enhances the physical bonding force between the solder mask bridge and the substrate, effectively preventing the lateral penetration and erosion of chemical agents such as developer along the interface between the solder mask bridge and the substrate. This greatly reduces the risk of the solder mask bridge detaching, floating, or lateral etching during manufacturing or subsequent use. Simultaneously, by removing laser processing residues, a good bonding interface between the solder mask ink and the substrate is ensured, improving the overall quality and reliability of the solder mask bridge. This method is particularly suitable for manufacturing solder mask bridges with fine pitch, improving the processing yield and long-term stability of circuit boards. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the manufacturing method of the solder mask bridge for circuit boards provided in this application.

[0037] Figure 2 This is a schematic diagram of the groove structure provided in Embodiment 1 of this application.

[0038] Figure 3 This is a schematic diagram of the groove structure provided in Embodiment 2 of this application. Detailed Implementation

[0039] Preferred embodiments of the invention will now be described in more detail with reference to the accompanying drawings. While preferred 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. Rather, these embodiments are provided so that the invention will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

[0040] To better understand the technical solution of this application, the following explanations are provided for the terms used in this application:

[0041] 1. Circuit board: In this application, it refers to a plate-like structure that carries electronic components and provides electrical connections, such as printed circuit boards, flexible circuit boards, and rigid-flex boards.

[0042] 2. Substrate / Base Material: Refers to the insulating base material used in circuit boards to form conductive patterns and mount components, such as FR-4, CEM-3, polyimide (PI), etc.

[0043] 3. Solder mask bridge: refers to a narrow strip of solder mask material formed between two or more adjacent pads (or other conductive patterns) on a circuit board. Its main function is to isolate adjacent pads during the soldering process and prevent short circuits (solder bridging) caused by solder flow.

[0044] 4. Design area of ​​the pre-designed solder mask bridge / Pre-designed solder mask bridge: refers to the specific geometric area planned in the circuit board design stage that will be formed into a solder mask bridge through the solder mask process in the future, including its preset width, length and position.

[0045] 5. Groove Structure: This refers to a recessed structure with a specific depth and width formed by selectively removing a portion of the substrate below the predetermined solder mask bridge design area on the substrate. The purpose of this groove is to provide a physical bonding base for the subsequent filling of solder mask ink and to create a stepped difference with the surrounding unprocessed substrate surface.

[0046] 6. Tangent circular array: A method of forming a groove in which the overall shape of the groove is composed of a series of circular (or nearly circular) laser ablation points (or very short line segments) that are closely arranged in the length direction and whose edges overlap (such as being tangent or slightly overlapping).

[0047] Existing technologies improve the adhesion between the solder mask and the substrate by "roughening" the substrate surface (such as chemical etching or mechanical polishing). The essence of this method is to increase the physical contact area and provide more microscopic anchoring points, aiming to improve the adhesion of solder bridges and indirectly reduce side etching. However, this "roughening" has the following inherent limitations:

[0048] 1. Non-selectivity and uncontrollability: "Ultra-roughening" is usually an indiscriminate treatment of a region or even the entire substrate surface, making it difficult to precisely control the morphology, depth, and location of the roughening, especially in the area under tiny solder mask bridges. This uncontrollability may lead to uneven roughening or excessive roughening that damages the substrate.

[0049] 2. Limited resistance to lateral penetration: Despite increased vertical adhesion, the roughened interface remains inherently open. For highly penetrating developing solutions, their ability to penetrate laterally along the "zigzag" path between the solder bridge bottom and the substrate is not structurally eliminated or significantly weakened. The solution can still "penetrate," especially during prolonged development or when the solution is highly aggressive; bottom hollowing and side etching problems remain difficult to eradicate.

[0050] This application fundamentally alters the bonding method and interface characteristics between the weld bridge and the substrate by precisely constructing a "groove-step difference" microstructure with specific geometric parameters at the bottom of the weld bridge, and supplementing it with a targeted "laser post-cleaning process," thereby achieving a dual and synergistic improvement in adhesion and resistance to chemical corrosion. This is not a simple surface modification, but rather a proactive design and reconstruction of the key interface.

[0051] Example 1: A method for manufacturing solder mask bridges on circuit boards using precision groove formation with carbon dioxide (CO2) laser and the circuit boards manufactured by this method.

[0052] like Figure 1 , Figure 2 As shown, this embodiment provides a method for manufacturing solder mask bridges on a PCB substrate using a CO2 laser.

[0053] Step 1: Project Document Design

[0054] Based on the design requirements of the solder mask bridges to be formed on the circuit board, the laser processing engineering documents are designed. The specific design is as follows:

[0055] 1. Groove structure design:

[0056] A groove structure is designed on the substrate surface corresponding to the predetermined solder mask bridge position. Based on the processing characteristics of CO2 laser, the groove is designed using a tangent circular array method, that is, the groove is composed of a series of closely arranged and partially overlapping (tangent) circular laser ablation points in the length direction, forming a continuous groove structure.

[0057] 2. Groove width design:

[0058] The width of the groove is designed to be 5 to 15 micrometers narrower than the designed width of the predetermined solder mask bridge. For example, if the designed width of the predetermined solder mask bridge is 50 micrometers, the width of the groove below it is designed to be between 35 and 45 micrometers; if the designed width of the predetermined solder mask bridge is 75 micrometers, the width of the groove is designed to be between 60 and 70 micrometers; if the designed width of the predetermined solder mask bridge is 100 micrometers, the width of the groove is designed to be between 85 and 95 micrometers.

[0059] 3. Groove length design:

[0060] The overall length of the groove is designed to cover the entire design length of the predetermined weld bridge, and extends outward by 0.1 mm at both ends of the predetermined weld bridge design length as compensation to ensure that an effective step difference and anchorage can also be formed at both ends of the weld bridge.

[0061] 4. Groove depth design:

[0062] The depth of the groove is designed and controlled between 5 and 10 micrometers. This is achieved by precisely controlling the energy and number of scans in subsequent laser processing.

[0063] The width of the groove is designed to be strictly smaller than the intended width of the solder mask bridge, specifically limited to a narrow range of 5μm to 15μm. This design is not arbitrary but based on the following considerations: First, it forms a "shoulder" support, ensuring that a sufficiently wide "shoulder" area is retained on the original substrate surface on both sides of the groove. When solder mask ink is applied, the main body of the solder mask bridge can firmly "sit" on these two shoulders, while the ink in the groove forms an embedded portion. This is fundamentally different from the prior art where the entire bottom is in contact with a rough surface; Second, it optimizes stress distribution. This "shoulder" support structure helps to disperse the stress generated by the solder mask bridge under curing shrinkage, thermal shock, or mechanical stress, avoiding stress concentration at weak bonding interfaces.

[0064] The groove depth is controlled between 5μm and 10μm. This depth is sufficient to create effective physical fit and step difference to block the chemicals, while avoiding potential reduction in local mechanical strength of the substrate or potential impact on the underlying circuitry that might result from excessively deep grooves. This represents a balance between enhancing performance and maintaining substrate integrity.

[0065] The continuous grooves are constructed using a tangent circular array design. This not only optimizes the laser processing path, but more importantly, the inner wall and bottom of the grooves, which are composed of a series of tiny arc surfaces, can further increase the contact area and interlocking complexity between the ink and the substrate in three-dimensional space compared to straight groove walls, forming a stronger "microscopic mechanical lock," which goes beyond simple two-dimensional roughening.

[0066] At both ends of the designed length of the weld resist bridge, the grooves extend outward by 0.1mm. This seemingly minor extension is actually a special reinforcement for the "weakest link" in the traditional process of weld resist bridge manufacturing. The ends are often the first to be subjected to stress or chemical corrosion, resulting in warping or peeling. By extending the grooves, it is ensured that the "heel" of the weld resist bridge is also firmly anchored within the grooves, forming full-length protection.

[0067] Step 2: AOI (Automated Optical Inspection)

[0068] AOI inspection is performed on semi-finished circuit boards that have undergone previous processes (such as etching of circuit patterns, cleaning and drying) to ensure that the circuit patterns are complete and free of defects and meet the requirements of subsequent processing.

[0069] Step 3: Laser processing to form the groove structure

[0070] A carbon dioxide (CO2) laser processing device (e.g., a "Mitsubishi 6th Generation Laser Machine" or an equivalent device) is used to laser process the design area of ​​the predetermined solder mask bridge on the substrate to form the groove structure designed in the above engineering documents.

[0071] As shown in the examples below, the laser frequency, mask size (effective working area), energy density, and number of scans were carefully optimized and matched for weld resist bridges of different widths. For example, for a 50μm weld resist bridge, a 0.9mm mask, 1.35mJ energy, and one scan were used to form a groove with a width of 38.2-40.2μm and a depth of approximately 6μm. This parameter combination is the result of multiple experiments and process optimizations, aiming to achieve efficient, precise, and damage-controlled ablation. In the table, the mask size increases accordingly with the increase of the weld resist bridge width, reflecting the adaptive adjustments made by the laser system for different processing targets to ensure energy distribution and processing efficiency. A significant feature of laser processing is its high degree of localization and controllability. Compared with "ultra-roughening," a process that affects the entire surface and whose morphology cannot be precisely predicted, the laser ablation of this invention precisely "carves" microstructures with specific geometries and sizes at the micrometer level.

[0072]

[0073] Step 4: Remove the residue generated during laser processing from the substrate.

[0074] Laser ablation (especially on organic substrates) inevitably produces micro-particle contaminants such as carbides and slag. If these residues are not thoroughly removed, they will seriously affect the bonding between the ink and the substrate, and may even become a source of defects.

[0075] Specific chemical cleaning agents (such as special film stripping solutions containing ingredients that can effectively dissolve or disperse organic carbon compounds) are used to soften and dissolve some of the contaminants.

[0076] Using physical methods such as high-pressure spraying and ultrasonic waves, loose or undissolved solid particles (such as toner) are peeled off and removed from the substrate surface and the inner wall of the groove.

[0077] Thoroughly peel off and remove the toner at the interface between the sidewall of the solder mask bridge and the substrate. This eliminates the blackening defect at the edge of the solder mask bridge after subsequent development that may be caused by toner adsorption. At the same time, it prevents the risk of toner residue causing micro-short circuits in subsequent surface treatment processes and improves the linewidth accuracy of the solder mask bridge.

[0078] Step 5: Apply solder resist ink

[0079] The circuit board, after laser processing and residue removal, is then coated with solder resist ink. Conventional solder resist inks (such as green, black, white, or other liquid photosensitive solder resist inks) are applied evenly to the circuit board surface, including the predetermined solder bridge design area, through screen printing, spraying, or other coating methods.

[0080] Under applied pressure (such as the pressure of a screen printing squeegee), the solder resist ink fully fills the groove structure previously formed by laser processing. Because the width of the groove is less than the width of the predetermined solder resist bridge and has a certain depth, after filling the groove, the portion of the solder resist ink within the groove is lower than the surrounding unprocessed substrate surface, while the ink at the edge of the groove extending to the predetermined width of the solder resist bridge is higher than the ink within the groove. In this way, a stepped structure formed by the groove walls is naturally created at the bottom of the solder resist bridge.

[0081] Due to the complex mechanical interlocking between the inner wall of the groove (especially the micro-undulating surface formed by the tangent circular array) and the ink, a "three-dimensional anchoring" effect far exceeding planar adhesion is achieved. The stepped difference structure forms a physical barrier at the bottom edge of the solder mask bridge. When subsequent developing solutions attempt to penetrate from the side, this "step" effectively blocks or significantly delays the lateral penetration path of the solution, making it difficult for the solution to directly attack the bonding interface at the bottom of the solder mask bridge.

[0082] Step 7: Surface treatment and subsequent processes

[0083] After the solder mask bridges are formed, the circuit board undergoes subsequent surface treatment (such as electroless gold plating, tin plating, OSP, etc.) and final inspection.

[0084] This embodiment also provides a circuit board obtained by the above manufacturing method, which has the following structural features in each area where solder mask bridges need to be formed:

[0085] The substrate of the circuit board (such as FR-4) has an integrally formed groove structure below each solder mask bridge at the corresponding position, created by precision ablation using a CO2 laser. This groove is a structural change to the substrate itself, rather than an additional layer.

[0086] The width of the groove is smaller than the final width of the solder mask bridge formed above it, specifically 5 to 15 micrometers narrower; the depth of the groove is controlled between 5 and 10 micrometers. A tangent circular array design is used, and the inner wall of the groove exhibits a micro-wavy or serrated shape. The overall length of the groove covers the solder mask bridge and extends 0.1 millimeters at each end.

[0087] The solder mask bridge is composed of solder mask ink. The ink not only covers the substrate surface of the predetermined solder mask bridge area, but a portion of it is also deeply embedded and filled within the aforementioned groove structure, forming a strong embedded bond. Due to the presence of the groove, a step difference of 5 to 10 micrometers in height is formed between the bottom of the solder mask bridge (the ink portion within the groove) and the surrounding unprocessed original surface of the substrate through the walls of the groove.

[0088] Because a thorough carbon black removal process is performed before ink application, the interface between the solder resist ink and the inner wall of the groove and the surface of the substrate is highly clean and free of contaminants, ensuring maximum chemical bonding and physical adsorption between the ink and the substrate.

[0089] The key advantages of this circuit board product:

[0090] 1. Extremely high adhesion reliability of solder mask bridges: Through the "three-dimensional interlocking" and "shoulder support" structure, the bonding force between the solder mask bridge and the substrate far exceeds that of traditional planar adhesion. It can effectively resist various stresses in the manufacturing process and the usage environment, and prevent detachment and breakage.

[0091] 2. Excellent resistance to chemical corrosion: The stepped differential structure forms an effective physical barrier, which greatly weakens the attack of chemicals such as developer on the root of the solder mask bridge, and significantly reduces the risk of side corrosion and bottom hollowing.

[0092] 3. Suitable for high-density fine lines: It can stably manufacture fine solder mask bridges of 50-100μm, meeting the stringent requirements of high-density interconnect (HDI) and fine-pitch device packaging for PCBs.

[0093] 4. Improved overall yield and long-term stability: Due to the performance improvements brought about by the above structure, the first-pass yield of the circuit board during the manufacturing process is significantly improved, while the long-term reliability and electrical stability during use are also strongly guaranteed.

[0094] Example 2: A method for manufacturing solder mask bridges on circuit boards using UV laser precision engraving and the circuit boards manufactured by this method.

[0095] like Figure 1 , Figure 3 As shown, this embodiment provides a method for manufacturing solder mask bridges on a PCB substrate using a UV laser. Due to its extremely small spot size and excellent focusing, the UV laser typically performs linear etching using a high-speed galvanometer scanning method, resulting in linear grooves with clear contours and steep edges. This manufacturing method mainly includes the following steps:

[0096] Step 1 to Step 2:

[0097] The engineering design principles (groove width 5-15μm narrower than the weld bridge, depth 5-10μm, and length extended by 0.1mm at both ends) and AOI inspection are similar to those in Example 1. Considering the characteristics of UV lasers, the groove is designed as a linear groove with straight sidewalls and a bottom.

[0098] Step 3: UV laser fine engraving

[0099] A UV laser cutting machine is used to precisely linearly scan and etch along the length of a predetermined solder mask bridge by controlling the laser beam, thereby forming a linear groove with a set width and depth.

[0100] UV laser processing typically employs high frequencies (e.g., 1000 kHz) combined with precisely controlled scanning speeds (e.g., 300-800 mm / s) and power coefficients. The laser beam is precisely guided by a high-speed galvanometer system, removing the substrate along a straight path. UV laser processing is a "cold processing" method, resulting in a minimal heat-affected zone. This leads to very steep, well-defined edges and relatively smooth sidewalls and bottoms in the formed linear grooves. The processing parameters are illustrated in the following example:

[0101]

[0102] Steps 4 through 7:

[0103] The removal of residues (UV laser ablation products, although less than those from CO2 laser ablation, still need to be removed through a stripping process combining chemical dissolution and physical peeling to ensure the highest cleanliness), ink filling, subsequent processes, and beneficial effects are all based on the same principles and implementation methods as in Example 1.

[0104] This embodiment also provides a circuit board obtained by the above manufacturing method, whose structural features in the solder mask bridge area are similar to those of the product described in Embodiment 1 in macroscopic function, but differ in microscopic morphology:

[0105] The substrate has an integrally formed linear groove structure with flat sidewalls and bottom, which is formed by the above-mentioned UV laser linear scanning etching at the corresponding position below each solder bridge.

[0106] The groove width is smaller than the width of the solder mask bridge above it (narrow 5-15μm), the depth is 5-10μm, and the length covers the solder mask bridge and extends 0.1 mm at each end.

[0107] Solder resist ink is filled into the linear grooves formed by UV laser, thus creating an embedded bond and a stepped structure. Because the grooves formed by UV laser processing have clear contours and steep edges, the stepped structure formed after ink filling is also more regular and has distinct edge boundaries.

[0108] Through a targeted residue removal process, a pure bond between the ink and the UV laser-processed surface is ensured.

[0109] The key advantages of this circuit board product:

[0110] In addition to possessing the common advantages of the circuit board products described in Example 1 (such as high adhesion, resistance to chemical corrosion, and suitability for high density), the product of this embodiment has further advantages in the following aspects due to the characteristics of UV laser linear etching:

[0111] 1. UV lasers can form linear grooves with steep edges and straight sidewalls, making the stepped difference structure formed after ink filling more standard and consistent. This is more advantageous for applications that require precise control of the edge contour of the solder mask bridge.

[0112] 2. UV laser has a smaller heat-affected zone, resulting in less thermal and physical damage to the substrate, better preservation of the substrate's original electrical and mechanical properties, and higher flatness at the bottom of the groove.

[0113] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of this application. Any specific values ​​in all examples shown and discussed herein should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0114] Furthermore, it should be noted that the use of terms such as "first" and "second" is merely for ease of distinction, and unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for manufacturing a solder mask bridge on a circuit board, the circuit board comprising a substrate, characterized in that, The manufacturing method includes the following steps: Laser processing is performed on the design area of ​​the predetermined solder mask bridge on the substrate to form a groove structure. The width of the groove structure is smaller than the design width of the predetermined solder mask bridge, and the depth of the groove structure is 5 micrometers to 10 micrometers. Remove residues generated during laser processing from the substrate; Solder resist ink is applied to the designed area, and the solder resist ink fills the groove structure to form a solder resist bridge with a stepped difference.

2. The method for manufacturing a solder mask bridge on a circuit board according to claim 1, characterized in that: The width of the groove structure is 5 to 15 micrometers narrower than the design width of the predetermined weld bridge.

3. The method for manufacturing a solder mask bridge on a circuit board according to claim 1, characterized in that: Along the width direction of the groove structure, the distance between the top edge of the opening of the groove structure and the edge of the predetermined solder mask bridge is 2.5 μm to 10 μm.

4. The method for manufacturing a solder mask bridge on a circuit board according to any one of claims 1 to 3, characterized in that: The length of the groove structure covers the design length of the predetermined weld bridge, and extends outward by a predetermined distance at both ends of the design length of the predetermined weld bridge.

5. The method for manufacturing a solder mask bridge on a circuit board according to claim 4, characterized in that: The preset distance is 0.1 mm.

6. The method for manufacturing a solder mask bridge on a circuit board according to claim 1, characterized in that: The laser processing is either carbon dioxide laser processing or UV laser processing.

7. The method for manufacturing a solder mask bridge on a circuit board according to claim 1, characterized in that: The groove structure includes several cylindrical grooves arranged along its length, with adjacent cylindrical grooves being tangent to each other.

8. The method for manufacturing a solder mask bridge on a circuit board according to claim 1, characterized in that: The step of removing the residue generated by laser processing on the substrate is performed using a film stripping process.

9. The method for manufacturing a solder mask bridge on a circuit board according to claim 8, characterized in that: The film removal process includes chemical dissolution and physical stripping of toner and particulate contaminants.

10. A circuit board, comprising a substrate and solder mask bridges formed on the substrate, characterized in that: The substrate has a groove structure at a corresponding position below the solder mask bridge. The width of the groove structure is smaller than the width of the solder mask bridge, and the depth of the groove is 5 micrometers to 10 micrometers. The solder resist ink of the solder bridge is filled within the groove structure; The bottom of the solder resist bridge and the surface of the substrate are separated by a stepped difference through the wall of the groove.

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