Circuit board blind slot edge loopless metallization molding process

Abstract

The application discloses a blind slot edge ringless metallization forming process. The process comprises the following steps: providing a circuit board, laser cutting the circuit board to form a blind slot structure in a first preset area of the circuit board; activating a second preset area at the bottom of the blind slot structure to form an activated area at the bottom of the blind slot structure; and locally depositing copper on the blind slot structure on the circuit board to form a blind slot edge metal edge covering layer. The application locally activates a target area at the bottom of the blind slot and combines a local copper deposition process to form a ringless metal edge covering layer while controlling the metallization range, thereby improving the metallization precision of the blind slot structure, the bonding reliability and the space utilization rate of the circuit board.

Description

Technical Field

[0001] This invention relates to the field of printed circuit board manufacturing technology, and in particular to a ringless metallization forming process for the edge of blind slots on circuit boards. Background Technology

[0002] In existing circuit board blind slot processing and metallization processes, laser processing is typically used to form the blind slot structure, followed by overall surface activation and chemical copper plating to form a conductive metal layer in the blind slot area. However, in existing blind slot metallization processes, resin modification layers, microporous structures, and residual active substances are easily generated on the surface and surrounding areas of the slot after laser processing. During overall activation and chemical copper plating, it is difficult to precisely define the copper plating area, easily leading to the formation of a continuous annular copper layer around the edge of the blind slot. This annular metal structure not only affects the insulation spacing around the blind slot but may also cause local electrical performance abnormalities, reducing the space utilization of the circuit board design. Furthermore, existing processes typically use overall surface activation to improve copper plating adhesion, but it is difficult to simultaneously meet the metallization requirements at the bottom of the blind slot and the insulation requirements of non-target areas. At the same time, insufficient surface activity at the bottom of the blind slot formed by laser processing can also lead to insufficient adhesion and poor continuity of subsequent copper layers, affecting the reliability of the metallized structure. Summary of the Invention

[0003] Therefore, the present invention needs to provide a ringless metallization forming process for the edge of blind slots on circuit boards to solve at least one of the above-mentioned technical problems.

[0004] To achieve the above objectives, a process for forming a ringless metallization of the edge of a blind slot on a circuit board includes the following steps: A circuit board is provided, and the circuit board is laser-cut to form a blind groove structure in a first preset area of ​​the circuit board; The second preset area at the bottom of the blind groove structure is activated to form an activated area at the bottom of the blind groove structure; Local copper plating is performed on the blind slot structure on the circuit board to form a metal cladding layer at the edge of the blind slot in the activated area.

[0005] This invention uses laser cutting to form a blind trench structure in a first predetermined area on a circuit board. A second predetermined area at the bottom of the blind trench structure is then activated, limiting the activated area to the target metallization location. A metal cladding layer is then formed at the edge of the blind trench through localized copper plating in the activated area, achieving selective metallization of the blind trench structure. This effectively controls the range of copper layer formation, preventing continuous annular copper layers from forming in non-target areas around the blind trench and improving the forming accuracy of annular metallization at the blind trench edge. Simultaneously, localized activation of the bottom of the blind trench structure provides a basis for copper plating reaction, improving the subsequent deposition of copper materials in the target area and enhancing the bonding stability between the metal cladding layer and the circuit board substrate. The localized copper plating to form the metal cladding layer at the edge of the blind trench ensures reliable conductive connections at the bottom of the blind trench structure while maintaining insulation of the blind trench sidewalls and non-activated areas, improving the insulation reliability and space utilization of the circuit board. By defining the correspondence between the activated area and the metal cladding layer, the metallization process is transformed from overall processing to regional control, reducing the risk of residual copper layer formation in non-target areas and improving the controllability and consistency of the blind trench structure metallization process. Attached Figure Description

[0006] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the process steps for the ringless metallization forming of the edge of a blind slot on a circuit board according to the present invention. Figure 2 for Figure 1 A detailed flowchart of step S3. Detailed Implementation

[0007] The technical method of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0008] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor methods and / or microcontroller methods.

[0009] It should be understood that although the terms "first," "second," etc., may be used herein to describe various units, these units should not be limited by these terms. These terms are used merely to distinguish one unit from another. For example, without departing from the scope of the exemplary embodiments, a first unit may be referred to as a second unit, and similarly, a second unit may be referred to as a first unit. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0010] To achieve the above objectives, please refer to Figure 1 This invention provides a process for forming a ringless metallization of the edge of a blind slot on a circuit board, the method comprising the following steps: Step S1: Provide a circuit board, perform laser cutting on the circuit board, and form a blind groove structure in the first preset area of ​​the circuit board; A circuit board is provided. A first preset area is determined according to a preset processing position. The circuit board is then laser-processed using laser cutting equipment to remove material from the board in certain areas, forming a blind groove structure in the first preset area. Precise forming of the blind groove structure through laser cutting improves the positional accuracy of the blind groove.

[0011] Step S2: Activate the second preset area at the bottom of the blind groove structure to form an activated area at the bottom of the blind groove structure; The second preset region at the bottom of the blind trench structure is activated, causing activated particles to adsorb onto the surface of the second preset region, forming an activated region at the bottom of the blind trench structure. By limiting the activated region, it is ensured that the activated region is located only at the target metallization location, reducing metal deposition in non-target areas and improving the control accuracy of the metallization region.

[0012] Step S3: Perform local copper plating on the blind slot structure on the circuit board to form a metal cladding layer at the edge of the blind slot in the activated area.

[0013] After activation, the circuit board undergoes localized copper plating, which preferentially deposits copper in the activated area, forming a metal cladding layer at the edge of the blind trench. This localized copper plating method limits the range of copper layer formation, preventing the formation of continuous annular copper layers around the blind trench and achieving annular-free metallization at the edge of the blind trench.

[0014] In one embodiment, a circuit board is provided, and the step of laser cutting the circuit board to form a blind groove structure in a first predetermined area of ​​the circuit board includes: A circuit board is provided, and the circuit board is laser-cut to form a blind groove structure in a first preset area of ​​the circuit board. The second preset area of ​​the blind groove structure is roughened by laser to form a rough surface in the second preset area.

[0015] In this embodiment, after locating the circuit board processing area, the circuit board is fixed on the processing platform of the laser processing equipment. The laser processing path is controlled according to the position parameters of the first preset area to perform laser cutting on the circuit board, removing the substrate material within the first preset area and forming a blind groove structure on the circuit board. During the formation of the blind groove structure, the laser energy density, pulse frequency, and scanning speed are adjusted according to the position parameters of the second preset area, so that the laser acts on the second preset area at the bottom of the blind groove structure, performing microscale ablation on the surface of the second preset area, forming a rough surface with a microscopic uneven structure. By controlling the laser processing parameters, the morphology and size of the rough surface meet the activation treatment requirements, improving the bonding ability between the second preset area and the activated particles.

[0016] By simultaneously performing laser roughening treatment on the second preset region during the formation of the blind trench structure, a rough surface is created in the second preset region, increasing its surface area and enhancing the adsorption capacity of activated particles, thereby improving the effect of subsequent activation treatment. At the same time, limiting the roughening treatment to the second preset region avoids excessive roughening in other areas of the blind trench structure, reduces the risk of metal deposition in non-target areas, improves the positional control precision of the subsequent activation region formation, and results in a final blind trench edge metal cladding layer with better bonding strength and regional consistency.

[0017] In one embodiment, the step of laser cutting a circuit board to form a blind groove structure in a first predetermined area of ​​the circuit board includes: The circuit board is laser-cut once to form a blind hole structure in the second preset area of ​​the circuit board. The bottom of the blind hole structure is pulsed and burned by the laser to form a rough surface at the bottom of the blind hole structure. The step of activating the second preset region at the bottom of the blind groove structure to form an activated region at the bottom of the blind groove structure includes: The bottom of the blind hole structure is activated to form an activated region at the bottom of the blind hole structure; The step of laser cutting the circuit board to form a blind groove structure in the first preset area of ​​the circuit board further includes: The circuit board is laser-cut a second time to form a blind groove structure in the first preset area of ​​the circuit board, so that the activation area is located within the bottom range of the blind groove structure. The second preset area is located within the first preset area, and the depth of the blind groove structure is the same as the depth of the blind hole structure.

[0018] In this embodiment, after locating the circuit board processing area, the circuit board is fixed on a laser processing device. The laser processing path is controlled according to the position parameters of the second preset area, and the circuit board is laser-cut once to remove material within the second preset area, forming a blind via structure on the circuit board. Subsequently, the bottom of the blind via structure is pulse-burned using a laser device. By controlling the laser pulse energy, pulse frequency, and action time, microscale melting and resolidification occur on the surface of the material at the bottom of the blind via structure, forming a rough surface at the bottom of the blind via structure. The range of rough surface formation is controlled by the pulse-burning method.

[0019] After the circuit board has undergone roughening, it is positioned to ensure full contact between the bottom of the blind via structure and the activation solution, while preventing other parts of the circuit board from contacting the solution. The activation process allows the rough surface to adsorb activation particles, forming an activation region at the bottom of the blind via structure. During activation, the activation range is controlled according to the position of the blind via structure, ensuring that the activation particles preferentially bind to the rough surface to form a catalytic region, thus enabling copper deposition at the bottom of the blind via structure. Simultaneously, the pre-formed rough surface enhances the adhesion stability of the activation particles, improving the continuity and uniformity of the activation region.

[0020] After the bottom activation treatment of the blind via structure is completed, the circuit board is subjected to secondary laser cutting according to the position parameters of the first preset area. This further removes material from the first preset area and forms a blind groove structure. The second preset area is located inside the first preset area, and by controlling the depth of the secondary laser cutting, the depth of the formed blind groove structure is made consistent with the depth of the blind via structure, thus ensuring that the activated area at the bottom of the original blind via structure is completely preserved within the bottom range of the blind groove structure. The unactivated areas within the first preset area are removed through secondary laser expansion processing.

[0021] By first forming a blind via structure and then pulse-burning the bottom of the blind via structure, followed by activation treatment and secondary laser cutting to form a blind trench structure, the metallized area is precisely defined before processing, avoiding the problem of difficulty in controlling the bottom activation range after directly processing the blind trench. Simultaneously, a rough surface is used to enhance the adhesion of activation particles, improving the stability of the activation area; secondary laser cutting removes non-target areas, ensuring that copper plating only affects the activation area, thereby reducing the formation of annular copper layers around the blind trench and improving the forming accuracy of annular metallization at the blind trench edge. This process, by changing the laser processing sequence, achieves precise matching between the blind trench structure and the metallized area, improving the reliability of the circuit board structure.

[0022] In one embodiment, activating the bottom of the blind hole structure to form an activation region at the bottom of the blind hole structure includes: The circuit board is placed in an activation solution so that the bottom of the blind via structure comes into contact with the activation solution, forming an activation region at the bottom of the blind via structure.

[0023] In this embodiment, after processing the rough surface of the bottom of the blind hole structure, the circuit board is positioned and fixed, and then placed in an activation solution. The area parallel to the first preset area is immersed in the activation area, ensuring full contact between the bottom of the blind hole structure and the activation solution, while preventing the circuit board area outside the first preset area from being immersed in the activation area. During the activation process, the immersion time is controlled according to the position and depth of the blind hole structure, allowing the activation solution to penetrate the interior of the blind hole structure and act on the rough surface, causing the rough surface to adsorb activation particles. By controlling the concentration of the activation solution, the processing temperature, and the processing time, the activation particles are uniformly bonded to the bottom of the blind hole structure, forming a continuously distributed activation area at the bottom of the blind hole structure. This activation area corresponds to the second preset area.

[0024] By placing the circuit board in an activation solution, the bottom of the blind via structure directly contacts the solution, achieving directional activation of the bottom of the blind via structure. Since a rough surface is formed at the bottom of the blind via structure, the adsorption capacity of the activation particles is enhanced, resulting in a more stable and uniform activated area. Simultaneously, by controlling the contact range between the activation solution and the bottom of the blind via structure, ineffective activation in other areas of the blind via structure is avoided, reducing the risk of copper deposition in non-target areas and improving the reliability of acyclic metallization at the edges of the blind via.

[0025] In one embodiment, the circuit board is placed in an activation solution, so that the bottom of the blind via structure comes into contact with the activation solution, allowing the rough surface of the bottom of the blind via structure to adsorb activation particles, thereby forming an activation region at the bottom of the blind via structure. Position the circuit board so that the edge area of ​​the circuit board where the blind slot structure is located is immersed in the activation solution; By using a shielding structure to cover the area outside the blind groove structure, the activation solution only comes into contact with the corresponding area of ​​the blind groove structure.

[0026] In this embodiment, after processing the rough surface of the bottom of the blind via structure, a protective dry film is applied to the circuit board surface parallel to the first preset area according to the spatial position of the first preset area. This protective dry film covers other areas parallel to the first preset area and forms a tight bond with the circuit board surface. The circuit board with the protective dry film applied is then installed in a positioning fixture and clamped from above. The circuit board is positioned according to the position parameters of the blind slot structure, ensuring that the edge area of ​​the circuit board containing the blind slot structure faces the activation treatment area. The circuit board is controlled to move vertically downwards, immersing the first preset area in the edge area of ​​the circuit board into the activation solution, with the first preset area located at the bottom of the circuit board, maintaining full contact between the bottom of the blind via structure and the activation solution. During the activation process, the protective dry film adheres tightly to the circuit board surface, preventing the activation solution from penetrating into other areas parallel to the first preset area, ensuring that the activation solution only contacts the corresponding position of the first preset area. Simultaneously, other areas above the circuit board are naturally isolated as they are not immersed in the activation solution and do not come into contact with it. By controlling the immersion range, immersion time, and flow state of the activation solution in the edge area of ​​the circuit board, the activation solution can stably enter the interior of the blind hole structure and act on the rough surface at the bottom of the blind hole structure, causing the rough surface to adsorb activation particles, thereby forming an activation area at the bottom of the blind hole structure.

[0027] By attaching a protective dry film to the circuit board surface parallel to the first preset area, and using the dry film to isolate and protect the parallel area, combined with the vertical immersion method of the circuit board, the activation process is transformed from whole-board processing to targeted area processing, improving the positional control of the activation area. The protective dry film adheres tightly to the circuit board surface, effectively preventing the activation solution from diffusing into the parallel area, reducing the risk of activation particle residue in non-target areas, thereby avoiding the formation of an ineffective copper layer during copper plating. Other areas above the circuit board are naturally removed from the activation solution's effective range by controlling the immersion depth, achieving isolation without additional shielding. At the same time, the localized activation method reduces activation solution consumption, improves process stability, and ensures that the formed activation area is aligned with the metal cladding layer at the bottom of the blind trench structure, improving the forming accuracy of the ringless metallization at the blind trench edge.

[0028] In one embodiment, the circuit board is subjected to secondary laser cutting to form a blind groove structure in a first predetermined area of ​​the circuit board, such that the activation area is located within the range of the bottom of the blind groove structure, including: The circuit board is mechanically positioned based on the positional parameters of the blind via structure and the relative positional relationship between the first and second preset areas. The laser beam parameters and scanning path of the laser cutting equipment are controlled so that the laser beam scans and removes material layer by layer along the contour boundary of the first preset area, and the laser cutting depth is controlled to be the same as the depth of the blind hole structure, removing only the material in the first preset area other than the second preset area.

[0029] In this embodiment, after the bottom activation treatment of the blind hole structure is completed and the activation area is formed, the circuit board is transferred from the activation treatment station to the laser processing station. Based on the positional parameters of the blind hole structure and the relative positional relationship between the first and second preset areas, the circuit board is mechanically positioned. The circuit board is fixed on the processing platform of the laser processing equipment, clamped and fixed by a mechanical fixture. Based on the spatial coordinates of the blind hole structure on the circuit board, the horizontal position and angle of the circuit board on the processing platform are adjusted so that the first preset area is aligned with the laser emission port of the laser processing equipment, and the second preset area is located at the internal center of the first preset area, thereby establishing a precise positional correspondence between the blind hole structure and the blind groove structure to be cut.

[0030] After mechanical positioning is completed, the laser beam parameters of the laser cutting equipment are set according to the size difference between the first and second preset areas and the characteristics of the substrate material. The pulse energy density, pulse frequency, and spot diameter of the laser beam are controlled to ensure that the laser beam has sufficient energy to ablate and remove the substrate material in the first preset area. At the same time, the single pulse energy of the laser beam is controlled not to exceed the damage threshold of the activated area at the bottom of the blind hole structure, so as to avoid thermal damage or mechanical peeling to the roughened surface and activated area at the bottom of the blind hole structure during laser action.

[0031] After the laser beam parameters are set, the scanning path of the laser beam is controlled, causing the laser beam to scan and remove material layer by layer along the contour boundary of the first preset region. Specifically, the laser beam starts from the outer boundary of the first preset region's contour and performs a circular scan along the contour boundary, advancing layer by layer towards the center of the first preset region, or it performs a spiral scan from the outside in along the contour of the first preset region, gradually removing the substrate material within the first preset region. During the scanning process, the scanning depth and interlayer feed rate of each layer are controlled, allowing the laser beam to ablate and remove material layer by layer. The cumulative depth of the laser cutting is controlled in real time to ensure that the final depth of the blind groove structure is the same as the depth of the blind hole structure.

[0032] Since the second preset region is located inside the first preset region, and the scanning range of the laser beam is limited to the area between the contour boundaries of the first and second preset regions, the laser beam removes only the material within the first preset region (excluding the second preset region) during the layer-by-layer scanning removal process, without affecting the bottom of the blind hole structure where the second preset region is located. When the laser cutting depth reaches the same as the depth of the blind hole structure, the substrate material within the first preset region (excluding the second preset region) is completely removed, forming a blind groove structure. The roughened surface and activated area at the bottom of the original blind hole structure, being located within the second preset region and not directly affected by the laser beam, are thus completely preserved within the bottom area of ​​the blind groove structure.

[0033] By mechanically positioning the circuit board during the secondary laser cutting process and precisely controlling the laser beam parameters, scanning path, and cutting depth, a precise spatial match is achieved between the blind groove structure and the activated area at the bottom of the blind via structure. A layer-by-layer scanning removal method is used to control the material removal range, preventing laser energy from diffusing to the bottom of the blind via structure, thus protecting the integrity of the roughened surface and activated area. Simultaneously, by controlling the cutting depth to be the same as the blind via structure depth, the bottom of the blind groove structure and the bottom of the blind via structure are placed on the same plane, ensuring a smooth deposition base for the subsequently formed metal cladding layer. This process, through physical positioning and manual adjustment of laser parameters, achieves precise forming of the blind groove structure, improving the forming accuracy and structural reliability of the ringless metallization at the blind groove edge.

[0034] In one embodiment, controlling the laser beam parameters and scanning path of the laser cutting equipment specifically involves: The pulse energy density and action time of the laser beam are controlled so that the laser beam only ablates the substrate material to be removed in the first preset area, without penetrating the activated area at the bottom of the damaged blind hole structure; Control the scanning path of the laser beam so that the laser beam scans gradually from the edge of the first preset area to the center area, or scans spirally from the outside to the inside along the contour of the first preset area, removing material layer by layer until a blind groove structure is formed; During laser cutting, inert gas is sprayed into the laser-affected area to blow away any residue generated during the cutting process.

[0035] In this embodiment, after the mechanical positioning of the circuit board is completed and the first preset area is aligned with the laser emission port, the laser beam parameters of the laser cutting equipment are set according to the physicochemical properties of the substrate material to be removed within the first preset area and the depth dimensions of the blind hole structure. The pulse energy density of the laser beam is controlled to be above the ablation threshold of the substrate material and far below the damage threshold of the activated area material at the bottom of the blind hole structure. At the same time, the duration of the laser pulse is controlled so that the laser energy is mainly concentrated on the surface area of ​​the substrate material to be removed within the first preset area. Through the photothermal effect, the surface material is instantaneously melted and vaporized and removed, while the heat-affected zone of the laser energy is confined to the interior of the surface material and does not penetrate to the activated area at the bottom of the blind hole structure. In particular, by adjusting the pulse width and peak power of the laser beam, the duration of a single pulse is insufficient to allow heat to accumulate to the bottom of the blind hole structure, thereby avoiding thermal damage, structural destruction, or detachment of activated particles from the roughened surface and activated area at the bottom of the blind hole structure due to heat conduction or laser penetration.

[0036] After the laser beam parameters are set, the scanning method of the laser beam is controlled so that it starts from the edge contour of the first preset area and gradually scans towards the center area along the contour boundary; or it performs a spiral continuous scan from the outside to the inside along the contour boundary of the first preset area. During the scanning process, the scanning depth of each layer of the laser beam is controlled to be a preset layer thickness, and after completing one layer, the laser beam is controlled to advance vertically downwards at a preset interlayer distance to scan and remove the next layer. The substrate material in the first preset area is gradually removed by accumulating layers. In particular, by controlling the overlap rate between adjacent scanning trajectories and the interlayer feed amount, the scanning range of the laser beam completely covers the area to be removed in the first preset area except for the second preset area, and the scanning trajectories of each layer are seamlessly connected to avoid unremoved residues or excessive ablation, until the layer-by-layer scanning removes the material to a predetermined depth that is the same as the depth of the blind hole structure, forming a blind groove structure with a regular contour.

[0037] During laser cutting, an inert protective gas is continuously sprayed into the laser-affected area. The inert protective gas is at least one of nitrogen or argon, injected through a gas nozzle at a preset pressure and flow rate into the interaction area between the laser beam and the substrate material, forming a directional airflow field within the laser-affected area. This directional airflow field promptly blows away molten resin slag, fiber carbonization products, and gaseous decomposition products generated by laser ablation from the laser-affected area, guiding them towards the external opening of the blind hole structure. By controlling the injection angle, injection pressure, and gas flow rate of the inert protective gas, the airflow field covers the laser-affected area while preventing direct impact on the roughened surface and activated area surface at the bottom of the blind hole structure. This prevents the blown-off slag and carbonization products from falling back and adhering to the roughened surface and activated area surface under airflow disturbance, thus maintaining the surface activity and cleanliness of the activated area.

[0038] By controlling the pulse energy density and duration of the laser beam, the effective range of the laser energy is strictly limited to the surface layer of the substrate material to be removed, avoiding damage to the activated area at the bottom of the blind hole structure caused by laser penetration or heat conduction. This ensures the integrity of the activated area and the active basis for subsequent copper plating reactions. By employing a layer-by-layer removal method that scans progressively from the edge to the center or uses a spiral scanning technique, the forming process of the blind hole structure is controllable and the contour is precise, avoiding the heat accumulation effect and material chipping defects caused by deep cutting in a single operation. By spraying inert protective gas into the laser action area, cutting byproducts are promptly removed, preventing slag and carbide products from falling back and contaminating the roughened surface and activated area at the bottom of the blind hole structure, thus maintaining the cleanliness of the activated area.

[0039] In one embodiment, see Figure 2 The process of locally depositing copper on the blind slot structure on the circuit board and forming a metal cladding layer at the edge of the blind slot in the activated area includes: Step S31: Clean the circuit board after activation treatment to remove residues from the surface of the blind slot structure; Step S32: Cover the inactive area using a masking structure; Step S33: Place the circuit board in the solution to allow the activated area to adsorb the copper catalyst and generate initial copper crystal nuclei in the activated area; Step S34: Based on the initial copper crystal nucleus, continue the chemical copper deposition process to allow copper metal to extend and deposit along the activation region at the bottom of the blind trench structure to form a continuous copper seed layer; Step S35: Thickening process is performed based on the continuous copper seed layer to form a continuous metal cladding layer at the bottom of the blind slot structure.

[0040] In this embodiment, after the activation treatment is completed and the activated area is formed, the circuit board is transferred to the cleaning station. The cleaning parameters are adjusted according to the position of the blind trench structure to ensure the cleaning medium can fully act on the surface of the blind trench structure. The surface of the blind trench structure is treated by spray cleaning, immersion cleaning, or ultrasonic-assisted cleaning to remove impurities, unbound activated particles, and activation solution residues remaining on the surface of the blind trench structure during the activation treatment. During the cleaning process, the flow rate of the cleaning medium and the treatment time are controlled to keep the activated area at the bottom of the blind trench structure intact and avoid damage to the activated area during the cleaning process. After cleaning, the circuit board is dried to ensure that the surface of the blind trench structure meets the adsorption conditions for copper plating catalysts.

[0041] After cleaning, the circuit board is positioned, and an inactive area is covered using a shielding structure to isolate it from the copper plating catalyst, leaving only the activated area in a reactive state. The circuit board is then placed in a solution containing the copper plating catalyst, bringing the activated area into contact with it. During the process, the activated particles in the activated area adsorb the copper plating catalyst, causing it to preferentially bind to the surface of the activated area. This catalytic reaction induces initial reduction deposition of copper ions in the activated area, forming continuously distributed initial copper nuclei. The shielding structure limits the effective range of the copper plating catalyst, ensuring that the initial copper nuclei form only in the target metallization region.

[0042] After the initial copper nucleus is formed, the circuit board remains immersed in the chemical copper deposition solution to allow the chemical copper deposition reaction to continue. Using the initial copper nucleus as the starting point for copper deposition, the copper metal is guided to gradually expand and deposit along the direction of the activation region, covering the surface of the activation region and forming a continuous copper seed layer at the bottom of the blind trench structure. During the chemical copper deposition process, the copper deposition process is kept uniform and stable by controlling the concentration of the copper deposition solution, the reaction temperature, and the processing time, avoiding localized insufficient deposition or overgrowth. Simultaneously, because the unactivated areas are isolated by the shielding structure, the copper material mainly expands along the activation region, thus ensuring that the continuous copper seed layer maintains a corresponding relationship with the target metallization region.

[0043] After forming a continuous copper seed layer, the circuit board is placed in an electroplating machine for thickening, using the continuous copper seed layer as a conductive base. By controlling the electroplating current density, electroplating time, and electroplating solution circulation, copper ions are continuously reduced and deposited on the surface of the continuous copper seed layer, gradually growing along the bottom of the blind trench structure, thus increasing the thickness of the continuous copper seed layer. During the thickening process, copper metal gradually fills the microscopic gaps in the continuous copper seed layer, improving the continuity and density of the copper layer, ultimately forming a continuous metal cladding layer at the bottom of the blind trench structure. Through electroplating thickening, the metal cladding layer meets the requirements for conductivity and structural strength, while ensuring that the metal cladding layer is only distributed within the activated area.

[0044] Cleaning the activated circuit board reduces the impact of residues on the copper deposition process and improves the stability of initial copper nucleus formation. A shielding structure isolates unactivated areas, ensuring the copper deposition catalyst acts only on the activated areas, achieving precise control over copper deposition location. The initial copper nuclei induce the formation of a continuous copper seed layer, which is further thickened to form a continuous metal cladding layer, resulting in good continuity, bonding strength, and conductivity. Simultaneously, this process avoids copper deposition in unactivated areas, reducing the formation of annular copper layers around the blind trench from the source, achieving annular metallization at the blind trench edge.

[0045] In one embodiment, placing the circuit board in a solution allows the activated region to adsorb copper deposition catalyst, and the generation of initial copper crystal nuclei in the activated region includes: The circuit board is immersed in a catalytic activation solution to allow the activated area to adsorb catalytically active particles and form a catalytic activation layer on the surface of the activated area. The circuit board after the formation of the catalytic activation layer is washed with water to remove residual catalysts that are not bound to the surface of the activation area; The circuit board is placed in a reduction solution for reduction treatment, which activates the catalytic active particles in the catalytic activation layer and induces copper ions to be reduced and deposited in the activation area to form initial copper crystal nuclei.

[0046] In this embodiment, after the activation region is formed, the circuit board is positioned and immersed in a catalytic activation solution to ensure full contact between the solution and the activation region. During immersion, the immersion time, solution temperature, and solution concentration are controlled according to the location of the activation region, allowing the catalytically active particles in the solution to preferentially adsorb onto the surface of the activation region. Since the surface of the activation region provides a basis for particle adhesion, the catalytically active particles can form a stable bond with the activation region, resulting in a continuously distributed catalytic activation layer. By controlling the flow state of the catalytic activation solution, the catalytically active particles can fully cover the activation region, improving the uniformity of the catalytic activation layer.

[0047] After the catalytic activation layer is formed, the circuit board is transferred to a water washing station for washing to remove residual catalysts not bonded to the surface of the activated areas. During the washing process, the water flow rate, water pressure, and washing time are controlled to detach weakly adhered residual catalysts from the circuit board surface while maintaining the integrity of the catalytic activation layer structure already bonded to the activated areas. By directionally removing residual catalysts, the impact of residual catalysts in unactivated areas on the copper deposition process is reduced, ensuring that the copper ion reduction deposition process mainly occurs in the activated areas, thus improving the accuracy of the initial copper crystal nucleus formation location.

[0048] After washing, the circuit board is placed in a reduction solution for reduction treatment, transforming the inactive catalytic particles in the catalytic activation layer into an active state with catalytic capabilities. During the reduction process, the reducing components in the reduction solution act on the catalytic activation layer, activating the catalytic particles and making them catalytic centers for the reduction reaction of copper ions. Subsequently, the catalytic particles induce copper ions in the reduction solution to undergo reduction deposition on the surface of the activated region, causing copper atoms to gradually aggregate and form initial copper crystal nuclei. By controlling the reduction treatment conditions, the initial copper crystal nuclei are uniformly distributed in the activated region.

[0049] By first forming a catalytic activation layer in the activation region, then removing residual catalysts through water washing, and finally activating the catalytically active particles through reduction treatment, the initial copper crystal nuclei can be precisely formed in the activation region. This process improves the controllability of the copper deposition initiation location and reduces ineffective copper deposition in non-activated regions due to catalyst residues. Simultaneously, the catalytic activation layer enhances the bonding between the activation region and the copper material, improving the uniformity of the initial copper crystal nuclei distribution.

[0050] In one embodiment, thickening based on a continuous copper seed layer to form a continuous metal cladding layer at the bottom of the blind slot structure includes: The circuit board forming the continuous copper seed layer is placed in a chemical copper plating solution for the first copper plating thickening treatment, so that copper ions are deposited on the surface of the continuous copper seed layer to form the first thickened copper layer. The circuit board with the first thickened copper layer is cleaned and then activated. The activated circuit board is placed in a chemical copper plating solution for a second copper plating thickening treatment, so that copper ions continue to deposit on the surface of the first thickened copper layer to form a second thickened copper layer. The cleaning, activation, and copper plating processes are repeated to stack multiple thickened copper layers one after another and fill the micro-gaps in the continuous copper seed layer to form a continuous metal cladding layer of the target thickness.

[0051] In this embodiment, after the continuous copper seed layer is formed, the circuit board is positioned and placed in a chemical copper plating solution for the first round of chemical copper plating treatment, ensuring full contact between the continuous copper seed layer and the solution. During the first round of chemical copper plating, the initial copper nuclei formed on the surface of the continuous copper seed layer serve as autocatalytic reaction centers. By controlling the temperature, solution concentration, pH value, and treatment time of the chemical copper plating solution, copper ions in the plating solution undergo autocatalytic reduction deposition on the surface of the initial copper nuclei. Since the continuous copper seed layer corresponds to the activation region, copper ions preferentially deposit on the surface of the continuous copper seed layer corresponding to the activation region and gradually extend and grow along the direction of the activation region, gradually increasing the thickness of the copper layer at the bottom of the blind trench structure, forming a first thickened copper layer covering the surface of the continuous copper seed layer. During the first round of chemical copper plating, by adjusting the parameters of the copper plating solution, the copper ion deposition rate is kept stable, avoiding localized excessive or insufficient thickness of the copper layer and improving the uniformity of the thickness of the first thickened copper layer.

[0052] After the first thickened copper layer is formed, the circuit board is removed from the chemical copper plating solution and transferred to a cleaning station for cleaning. By controlling the flow rate, pressure, and time of the cleaning medium, the surface of the circuit board and the interior of the blind trench structure are thoroughly cleaned to remove chemical copper plating solution residues, deposition byproducts, and unreacted solution components adhering to the surface of the first thickened copper layer and the blind trench structure. During the cleaning process, the temperature and flow rate of the cleaning medium are controlled to effectively remove impurities from the surface of the first thickened copper layer while avoiding mechanical damage or chemical corrosion to the deposited copper layer. After cleaning, the circuit board is dried to ensure that the surface of the first thickened copper layer meets the conditions for micro-etching activation treatment.

[0053] After cleaning, the surface of the first thickened copper layer undergoes micro-etching activation treatment. The circuit board is placed in a micro-etching activation solution, and by controlling the component concentration, treatment temperature, and treatment time of the solution, a micro-etching reaction occurs on the surface of the first thickened copper layer. This removes the oxide layer formed on the copper layer surface during storage and cleaning, and creates a micro-rough structure on the surface of the first thickened copper layer, increasing the number of surface active sites. The micro-etching depth is controlled to limit the etching to the surface area of ​​the copper layer without damaging the overall continuity of the first thickened copper layer. After micro-etching activation treatment, the surface of the first thickened copper layer exposes a clean copper substrate with increased surface active sites, providing a good catalytic reaction basis for the next round of chemical copper plating.

[0054] After the micro-etching activation treatment is completed, the circuit board, which has undergone micro-etching activation, is placed again in the chemical copper plating solution for the next round of chemical copper plating. During this round of chemical copper plating, the surface of the first thickened copper layer, which has been micro-etched and activated, serves as a self-catalytic reaction center, allowing copper ions in the chemical copper plating solution to continue to undergo self-catalytic reduction deposition on the already formed thickened copper layer surface, forming a new thickened copper layer. Because the micro-etching activation treatment removes the surface oxide layer and increases surface active sites, a tight metallurgical bond is formed between the new copper deposition layer and the first thickened copper layer, and copper ions continue to expand and deposit along the activation region, further increasing the thickness of the copper layer at the bottom of the blind trench structure.

[0055] Repeat the cleaning, micro-etching activation, and chemical copper plating thickening steps described above, determining the number of cycles based on the target thickness requirement, allowing the thickened copper layer to accumulate and grow layer by layer along the thickness direction. In each cycle, residues and byproducts from the previous deposition are removed by cleaning, the surface activity of the copper layer is restored by micro-etching activation, and then the copper layer thickness is continuously increased by chemical copper plating. As the number of cycles increases, the thickened copper layer gradually fills the micro-gaps existing within the continuous copper seed layer, causing the original microporous structure to gradually close and improving the overall density of the copper layer. During this process, by controlling the processing time and copper plating solution parameters for each round of chemical copper plating, a stable bond is formed between the thickened copper layers, and the copper metal continues to expand along the activated area at the bottom of the blind trench structure, ultimately forming a continuous metal cladding layer that meets the thickness requirements.

[0056] By placing a continuous copper seed layer in a chemical copper plating solution and thickening it through multiple cycles, copper ions can be continuously reduced and deposited along the surface of the continuous copper seed layer, improving the copper layer thickness and structural stability. Using the continuous copper seed layer and subsequent thickened copper layers as a self-catalytic basis, the new thickened copper layer grows along the direction of the activated region, ensuring that the formation position of the continuous metal cladding layer is consistent with the target area. Simultaneously, micro-etching activation treatment in multiple cycles enhances interlayer bonding, and by progressively filling the microscopic gaps in the continuous copper seed layer, the density and bonding strength of the continuous metal cladding layer are improved, reducing the risk of copper layer fracture or local defects, and achieving stable formation of a ring-free metallized structure at the edge of the blind trench. This method requires no electricity, relying entirely on the self-catalytic reaction of chemical copper plating to thicken the copper layer, avoiding the overall metallization of non-activated areas, improving circuit board space utilization and structural reliability.

[0057] Therefore, the embodiments should be considered as exemplary and non-limiting in all respects, and the scope of the invention is not limited by the foregoing description. Thus, all changes falling within the meaning and scope of the equivalents of the application are intended to be included within the scope of the invention.

[0058] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features of the invention herein.

Claims

1. A process for forming a ringless metallization of the edge of a blind slot on a circuit board, characterized in that, Includes the following steps: A circuit board is provided, and the circuit board is laser-cut to form a blind groove structure in a first preset area of ​​the circuit board; The second preset area at the bottom of the blind groove structure is activated to form an activated area at the bottom of the blind groove structure; Local copper plating is performed on the blind slot structure on the circuit board to form a metal cladding layer at the edge of the blind slot in the activated area.

2. The circuit board blind slot edge annular metallization forming process according to claim 1, characterized in that, The step of providing the circuit board and laser-cutting the circuit board to form a blind groove structure in a first preset area of ​​the circuit board includes: A circuit board is provided, and the circuit board is laser-cut to form a blind groove structure in a first preset area of ​​the circuit board. The second preset area of ​​the blind groove structure is roughened by laser to form a rough surface in the second preset area.

3. The circuit board blind slot edge annular metallization forming process according to claim 2, characterized in that, The step of laser cutting the circuit board to form a blind groove structure in the first preset area of ​​the circuit board includes: The circuit board is laser-cut once to form a blind hole structure in the second preset area of ​​the circuit board. The bottom of the blind hole structure is pulsed and burned by the laser to form a rough surface at the bottom of the blind hole structure. The step of activating the second preset region at the bottom of the blind groove structure to form an activated region at the bottom of the blind groove structure includes: The bottom of the blind hole structure is activated to form an activated region at the bottom of the blind hole structure; The step of laser cutting the circuit board to form a blind groove structure in the first preset area of ​​the circuit board further includes: The circuit board is laser-cut a second time to form a blind groove structure in the first preset area of ​​the circuit board, so that the activation area is located within the bottom range of the blind groove structure. The second preset area is located within the first preset area, and the depth of the blind groove structure is the same as the depth of the blind hole structure.

4. The circuit board blind slot edge annular metallization forming process according to claim 3, characterized in that, The activation treatment of the bottom of the blind hole structure, forming an activation region at the bottom of the blind hole structure, includes: The circuit board is placed in an activation solution so that the bottom of the blind via structure comes into contact with the activation solution, forming an activation region at the bottom of the blind via structure.

5. The circuit board blind slot edge annular metallization forming process according to claim 4, characterized in that, The step of placing the circuit board in the activation solution, so that the bottom of the blind via structure comes into contact with the activation solution, and so that the rough surface of the bottom of the blind via structure adsorbs activation particles, forming an activation region at the bottom of the blind via structure, includes: Position the circuit board so that the edge area of ​​the circuit board where the blind slot structure is located is immersed in the activation solution; By using a shielding structure to cover the area outside the blind groove structure, the activation solution only comes into contact with the corresponding area of ​​the blind groove structure.

6. The circuit board blind slot edge annular metallization forming process according to claim 3, characterized in that, The process of performing secondary laser cutting on the circuit board to form a blind groove structure in a first preset area of ​​the circuit board, such that the activation area is located within the range of the bottom of the blind groove structure, includes: The circuit board is mechanically positioned based on the positional parameters of the blind via structure and the relative positional relationship between the first and second preset areas. The laser beam parameters and scanning path of the laser cutting equipment are controlled so that the laser beam scans and removes material layer by layer along the contour boundary of the first preset area, and the laser cutting depth is controlled to be the same as the depth of the blind hole structure, removing only the material in the first preset area other than the second preset area.

7. The circuit board blind slot edge annular metallization forming process according to claim 6, characterized in that, The laser beam parameters and scanning path of the laser cutting equipment are specifically as follows: The pulse energy density and action time of the laser beam are controlled so that the laser beam only ablates the substrate material to be removed in the first preset area, without penetrating the activated area at the bottom of the damaged blind hole structure; Control the scanning path of the laser beam so that the laser beam scans gradually from the edge of the first preset area to the center area, or scans spirally from the outside to the inside along the contour of the first preset area, removing material layer by layer until a blind groove structure is formed; During laser cutting, inert gas is sprayed into the laser-affected area to blow away any residue generated during the cutting process.

8. The circuit board blind slot edge annular metallization forming process according to any one of claims 1 to 7, characterized in that, The process of locally depositing copper on the blind slot structure on the circuit board and forming a metal cladding layer at the edge of the blind slot in the activated region includes: The circuit board after activation treatment is cleaned to remove residues from the surface of the blind slot structure. Use shielding structures to cover inactive areas; The circuit board is placed in a solution, which allows the activated area to adsorb copper catalyst and generate initial copper crystal nuclei in the activated area. Based on the initial copper crystal nucleus, chemical copper deposition treatment is continued, allowing copper metal to extend and deposit along the activated region at the bottom of the blind trench structure to form a continuous copper seed layer; A continuous metal cladding layer is formed at the bottom of the blind slot structure by thickening the continuous copper seed layer.

9. The circuit board blind slot edge annular metallization forming process according to claim 8, characterized in that, The step of placing the circuit board in a solution to allow the activated region to adsorb the copper deposition catalyst and generate initial copper crystal nuclei in the activated region includes: The circuit board is immersed in a catalytic activation solution to allow the activated area to adsorb catalytically active particles and form a catalytic activation layer on the surface of the activated area. The circuit board after the formation of the catalytic activation layer is washed with water to remove residual catalysts that are not bound to the surface of the activation area; The circuit board is placed in a reduction solution for reduction treatment, which activates the catalytic active particles in the catalytic activation layer and induces copper ions to be reduced and deposited in the activation area to form initial copper crystal nuclei.

10. The circuit board blind slot edge annular metallization forming process according to claim 8, characterized in that, The thickening process based on a continuous copper seed layer to form a continuous metal cladding layer at the bottom of the blind slot structure includes: The circuit board forming the continuous copper seed layer is placed in a chemical copper plating solution for the first copper plating thickening treatment, so that copper ions are deposited on the surface of the continuous copper seed layer to form the first thickened copper layer. The circuit board with the first thickened copper layer is cleaned and then activated. The activated circuit board is placed in a chemical copper plating solution for a second copper plating thickening treatment, so that copper ions continue to deposit on the surface of the first thickened copper layer to form a second thickened copper layer. The cleaning, activation, and copper plating processes are repeated to stack multiple thickened copper layers one after another and fill the micro-gaps in the continuous copper seed layer to form a continuous metal cladding layer of the target thickness.

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