Circuit board structure with large blind vias

Abstract

The utility model discloses a circuit board structure with big blind hole contains a substrate and forms on the substrate at least one side surface one base copper layer. In which the base copper layer inside forms a copper window, and the copper window has between 350 microns to 450 microns a characteristic width. In which, the substrate inside forms a blind hole, and the position of blind hole corresponds the copper window delimited ablation processing area and is located below the copper window. Therefore, through the pre-etching window design of base copper layer forms the ablation processing area, can stably realize big aperture blind hole processing demand under the condition of not changing the existing laser equipment.

Description

Technical Field

[0001] This utility model relates to a circuit board structure, and more particularly to a circuit board structure with a large blind via. Background Technology

[0002] With the development of high-density interconnect (HDI) technology, the demand for blind via diameters in circuit board structures is gradually increasing, with some applications even requiring large blind via diameters of approximately 16 mils (approximately 406 micrometers). However, existing laser drilling equipment, without upgrades or replacements, can generally only process blind via diameters up to approximately 12 mils (approximately 300 micrometers), and processes with diameters below 8 mils (approximately 200 micrometers) typically offer preferred and stable processing quality.

[0003] When the diameter of a blind hole exceeds the processing limit of the laser equipment (e.g., up to 16 mils), the quality of the blind hole after processing is often poor due to the limitations of laser processing parameters and energy distribution. For example, the hole opening shape is irregular, the residual glue residue inside the hole is difficult to remove, the copper layer at the bottom of the hole is easily damaged, or the plating of subsequent electroplating processes is uneven, which in turn affects the reliability of subsequent electrical conduction and product yield.

[0004] Therefore, how to effectively solve the quality and stability problems in the processing of large-diameter blind holes without changing the existing laser equipment has become a technical issue that the industry urgently needs to address. Utility Model Content

[0005] This utility model discloses a circuit board structure with large blind holes, mainly used to improve the technical problems existing in the prior art.

[0006] One embodiment of this utility model discloses a circuit board structure with a large blind via, comprising: a substrate; and a base copper layer formed on at least one side surface of the substrate; wherein a copper window is formed inside the base copper layer, and the copper window has a characteristic width between 350 micrometers and 450 micrometers; wherein a blind via is formed inside the substrate, and the position of the blind via corresponds to the ablation processing area defined by the copper window and is located below the copper window.

[0007] Optionally, the copper window has the characteristic width between 380 micrometers and 420 micrometers.

[0008] Optionally, the blind hole has a truncated cone profile that gradually converges from top to bottom, and the blind hole has an upper aperture and a lower aperture, wherein the upper aperture is larger than the lower aperture.

[0009] Optionally, the upper aperture is between 350 micrometers and 450 micrometers, and the ratio of the lower aperture to the upper aperture is not less than 70%.

[0010] Optionally, the upper aperture is between 380 micrometers and 420 micrometers, and the aperture ratio of the lower aperture to the upper aperture is between 75% and 100%.

[0011] Optionally, the circuit board structure with a large blind via further includes: a conductive copper layer covering the base copper layer on at least one side surface of the substrate, and extending downward along the hole wall of the blind via through the copper window, and connected to a base copper layer formed on the other side surface of the substrate.

[0012] Optionally, the width of the transverse overhang structure within the blind hole is no greater than 25 micrometers.

[0013] Optionally, the width of the lateral overhang structure is no more than 15 micrometers.

[0014] Optionally, the roundness of the blind hole is not less than 90%.

[0015] Optionally, the roundness of the blind hole is between 95% and 100%.

[0016] In summary, the circuit board structure with large blind vias of this invention, through a pre-etched window design of the base copper layer combined with laser ablation processing, can reliably meet the requirements for large-diameter blind via processing without changing existing laser equipment. Furthermore, it effectively improves problems commonly encountered in traditional laser processing, such as irregular hole contours, excessive residual adhesive residue inside the hole, and damage to the copper layer at the bottom of the hole. It also further ensures uniform metal plating and stable conductivity within the hole, enhancing the reliability of the circuit board product.

[0017] To further understand the features and technical content of this utility model, please refer to the following detailed description and drawings of this utility model. However, these descriptions and drawings are only used to illustrate this utility model and are not intended to limit the scope of protection of this utility model in any way. Attached Figure Description

[0018] Figure 1A This is a schematic diagram of the process of manufacturing a circuit board structure according to an embodiment of the present utility model (step S110).

[0019] Figure 1B This is a schematic diagram of the window opening steps (step S120) of an embodiment of the present utility model.

[0020] Figure 1C This is a schematic diagram of the ablation process steps in an embodiment of the present invention (step S130).

[0021] Figure 1D This is a schematic diagram of blind hole processing completed according to an embodiment of the present invention (step S140).

[0022] Figure 1E This is a schematic diagram of the copper plating process in an embodiment of the present invention (step S150).

[0023] Figure 2 This is a top view schematic diagram of the copper window formed on the copper foil substrate in an embodiment of this utility model.

[0024] Figure 3 This is a schematic diagram of laser ablation processed in a multi-ring pattern.

[0025] Figure 4 for Figure 3 A schematic diagram showing the overlapping areas of laser drilling in a multi-ring pattern during laser ablation.

[0026] Figure 5 This is a schematic diagram of laser ablation processed in a spiral manner.

[0027] Figure 6 This is a schematic diagram of a circuit board structure with a large blind hole according to an embodiment of the present invention. Detailed Implementation

[0028] In the following description, if a specific drawing is indicated or shown in a specific drawing, it is only to emphasize that most of the relevant content mentioned in the following description appears in that specific drawing, but does not limit the following description to refer only to that specific drawing.

[0029] The following specific embodiments illustrate the implementation methods disclosed in this utility model. Those skilled in the art can understand the advantages and effects of this utility model from the content disclosed in this specification. This utility model can be implemented or applied through other different specific embodiments, and various details in this specification can also be modified and changed based on different viewpoints and applications without departing from the concept of this utility model. Furthermore, the accompanying drawings of this utility model are for simple illustrative purposes only and are not depictions of actual dimensions, as stated in advance. The following embodiments will further describe the relevant technical content of this utility model in detail, but the disclosed content is not intended to limit the scope of protection of this utility model.

[0030] It should be understood that while terms such as "first," "second," and "third" may be used in this document to describe various components or signals, these components or signals should not be limited by these terms. These terms are primarily used to distinguish one component from another, or one signal from another. Furthermore, the term "or" as used herein should, as appropriate, include any combination of one or more of the related listed items.

[0031] [Manufacturing method for circuit board structure with large blind vias]

[0032] Please see Figures 1A to 1EAs shown, this embodiment of the present invention provides a method for manufacturing a circuit board structure, which includes steps S110, S120, S130, S140, and S150. It should be noted that the order of the steps and the actual operation method described in this embodiment can be adjusted according to needs and are not limited to those described in this embodiment.

[0033] Please see Figure 1A As shown, step S110 includes: providing a copper foil substrate (CCL), which includes a substrate 1 and a base copper layer 2 formed on at least one side surface (e.g., the top surface) of the substrate 1. In this embodiment, the copper foil substrate includes two base copper layers 2, 2' respectively formed on two side surfaces (e.g., the top surface and the bottom surface) of the substrate 1.

[0034] In some embodiments, the substrate 1 may be composed of a resin material and a reinforcing material. The resin material may include at least one of epoxy resin, phenolic resin, polyimide (PI) resin, polytetrafluoroethylene (PTFE) resin, bismaleimide triazine (BT) resin, and polyester resin. The reinforcing material may include at least one of glass fiber cloth and paper. The resin material can be combined with the reinforcing material to form a substrate 1 with electrical insulation, structural support, and mechanical strength, suitable for subsequent circuit formation and blind via fabrication processes.

[0035] The two base copper layers 2, 2' are formed on two side surfaces (such as the top and bottom surfaces) of the substrate 1 by lamination or electroplating to form the copper foil substrate. In this embodiment, the base copper layer 2 on at least one side surface (such as the top surface) of the substrate 1 is also subjected to thin copper treatment, thereby having a reduced copper thickness.

[0036] For example, before the thin copper treatment, the substrate copper layer 2 has a first copper thickness of approximately 11 to 14 micrometers (e.g., 12.19 micrometers or 480 microinches). After the thin copper treatment, the substrate copper layer 2 has a second copper thickness of approximately 8 to 11 micrometers (e.g., 9.65 micrometers or 380 microinches). In other words, after the thin copper treatment, the second copper thickness is reduced by approximately 2 to 4 micrometers (e.g., 2.5 micrometers or 100 microinches) compared to the first copper thickness. However, this invention is not limited to the above-described thin copper treatment steps.

[0037] Please see Figure 1B See also Figure 2As shown, step S120 includes performing a windowing step, which includes selectively etching the base copper layer 2 on at least one side surface (e.g., the top surface) of the substrate 1 to remove at least a portion of the base copper layer 2, thereby forming a copper window 3. The copper window 3 partially exposes the at least one side surface (e.g., the top surface) of the substrate 1 and defines an ablation processing area R1. Furthermore, the base copper layer 2 that is not etched away can protect the side surface (e.g., the top surface) of the substrate 1 during subsequent laser ablation processing, thereby facilitating the formation of an ideal hole shape for the subsequently formed blind via 4.

[0038] In this embodiment, the copper window 3 is circular and has a characteristic width W (i.e., the diameter of the copper window) between 350 micrometers and 450 micrometers, and preferably between 380 micrometers and 420 micrometers, but the present invention is not limited to this. In some embodiments of the present invention, the copper window 3 may also be, for example, elliptical, rectangular, or polygonal. The characteristic width W of the copper window refers to the lateral width of the copper window in the maximum extension direction corresponding to its shape. For example, if the copper window is circular, its characteristic width W is its diameter; if it is elliptical, rectangular, or polygonal, it can be defined as its longest diagonal or its largest circumscribed dimension.

[0039] Furthermore, in some embodiments of this invention, the selective etching can be achieved through pattern transfer and wet etching processes. Specifically, a photoresist pattern (not shown) can first be formed on the base copper layer 2, corresponding to the predetermined location for forming the copper window 3. Then, an acidic or alkaline copper etching solution (e.g., copper chloride etching solution, persulfate etching solution, hydrogen peroxide phosphoric acid etching solution) is used to etch the areas not protected by the photoresist, thereby removing the corresponding base copper layer 2 and forming the copper window 3. After etching, a photoresist removal process is performed, and preparations are made for subsequent laser ablation steps.

[0040] Please see Figure 1C , Figure 1D Please refer to the following as well. Figures 3 to 5 As shown, step S130 includes: performing an ablation step, which includes: using multiple laser beams L in a laser drilling manner, performing a laser ablation operation (multiple laser drilling) on ​​the portion of the substrate 1 located in the ablation processing area R1 defined by the copper window 3, thereby removing at least a portion of the substrate 1 (e.g., Figure 1C The material, and after the laser ablation process is completed, a blind hole 4 is formed in the substrate 1 (e.g., Figure 1D The blind hole 4 is located below the copper window 3.

[0041] The laser ablation process can be performed by using multiple laser beams L to ablate outwards from the center of the copper window 3 in a multi-ring ablation manner (e.g., ...). Figure 3 and Figure 4 ) or spiral ablation along a spiral path RS (e.g. Figure 5 Laser ablation is performed.

[0042] Among them, the multiple laser drilling profiles corresponding to the multiple laser beams L (such as...) Figures 3 to 5 The multiple circular dashed areas shown are arranged in an overlapping pattern to form a laser drilling area (i.e., the overall processing area covered by the overlap of all beams). This laser drilling area corresponds to the ablation processing area R1, completely overlapping the outline of the copper window 3, and its coverage is slightly larger than the area of ​​the ablation processing area R1 defined by the copper window 3. It is worth noting that this laser drilling area is slightly extended compared to the area of ​​the copper window 3, which helps compensate for the energy reduction effect at the laser processing boundary and avoids the generation of residual substrate material that is not completely removed. This design helps ensure that the substrate material within the ablation processing area R1 is fully removed and ensures the integrity of the hole boundary and the roundness of the hole shape.

[0043] like Figure 3 As shown, in this embodiment, the plurality of laser drilling profiles (e.g.) Figures 3 to 5 In the multiple circular dashed areas shown, the outermost laser-drilled holes are located near the boundary of the copper window 3. A portion of the circular laser-drilled hole outline extends to the outside of the copper window 3, while another portion overlaps the inside of the copper window 3. This arrangement ensures that the entire laser-drilled area completely covers the ablation processing area R1 defined by the copper window 3, and extends slightly outwards to ensure the integrity of the processing boundary and the consistency of the hole formation.

[0044] In some embodiments of this invention, the laser drilling profile (i.e., the profile corresponding to the plurality of laser beams L on the surface of the substrate 1) is... Figures 3 to 5 The circular dashed areas shown are arranged along a ring or spiral path (the number of encirclements can be 2 to 5 layers) and overlapped with a certain aperture overlap rate. Specifically, the laser drilling profile corresponding to each single laser beam L has an aperture overlap rate of about 30% to 70% with the drilling range corresponding to the adjacent laser beam L, more preferably about 40% to 60%, and more preferably about 45% to 55%. The above aperture overlap rate design can effectively improve the roundness and edge smoothness of blind holes, and ensure that the laser energy is evenly distributed in the processing area, which helps to improve the consistency of hole diameter and process stability.

[0045] Furthermore, the laser drilling profile corresponding to each individual laser beam L has a laser drilling diameter between 60 micrometers and 140 micrometers, preferably 80 micrometers and 120 micrometers, and particularly preferably 90 micrometers and 110 micrometers. The laser drilling profiles corresponding to the plurality of laser beams L on the surface of the substrate 1 (i.e., Figures 3 to 5 The number of the circular dashed areas shown is between 10 and 80, and preferably between 30 and 50, but this utility model is not limited thereto.

[0046] It is worth mentioning that in step S120, the base copper layer 2 that has not been etched away remains on the side surface (e.g., top surface) of the substrate 1, serving as a protective layer during the laser ablation process to prevent the protected parts of the substrate 1 from being directly ablated by laser energy. This ensures that the laser ablation operation is limited to the ablation processing area R1 defined by the copper window 3, and avoids damage to non-processed areas.

[0047] In some embodiments of this utility model, the laser ablation process can be performed using a laser processing device: the wavelength of the laser beam L can be an ultraviolet laser (UV Laser) of about 355 nanometers (nm), which has high absorption of the substrate resin material and high reflectivity of the copper layer, and can selectively ablate the substrate material without damaging the unetched base copper layer.

[0048] The single pulse energy of each laser beam L can be set between about 10 millijoules (mJ) and about 100 millijoules (mJ), and preferably between 20 millijoules (mJ) and 50 millijoules (mJ). The pulse width of the laser can be between about 1 microsecond (μs) and about 20 microseconds (μs), and preferably between 1 microsecond (μs) and 10 microseconds (μs). The pulse frequency of the laser can be set between about 10 kHz and about 200 kHz, preferably between 20 kHz and 100 kHz, but the present invention is not limited thereto.

[0049] During the ablation process, each laser beam L is shielded to adjust its aperture, so that the diameter of the laser-drilled hole formed by a single laser beam L on the surface of the substrate 1 can be between approximately 60 micrometers (μm) and approximately 140 micrometers (μm), and preferably between approximately 80 micrometers (μm) and approximately 120 micrometers (μm). The total number of laser-drilled holes required for the processing positions of the blind vias 4 can be set to approximately 10 to approximately 80, preferably between 30 and 60. The above parameters can be appropriately adjusted according to the type of substrate material, copper layer thickness, required hole size, and quality requirements to achieve a high-quality and stable laser ablation processing effect.

[0050] In one specific embodiment of this invention, the laser processing can be set to multiple different pulse width levels, such as internally encoded pulse settings of level 1, level 2, or level 6. The actual corresponding laser pulse width can be between approximately 1 microsecond (μs) and 20 microseconds (μs), preferably 2 to 10 microseconds. The specific value can be adjusted according to the laser equipment model and material compatibility. In actual operation, for example, a 2.5x mask can be used with different pulse width and number combinations, such as level 6 pulse width with 1 pulse, level 2 pulse width with 3 pulses, level 1 pulse width with 10 pulses, etc., and combined with light-gathering conditions (such as Coll. 237) to achieve the required drilling depth, contour, and hole diameter quality.

[0051] Please see Figure 1D As shown, after the laser ablation process is completed to form the blind hole 4, step S140 includes a de-smear step. This step aims to remove resin melt or carbonized residue generated inside or at the opening of the blind hole during the laser processing, thereby improving the cleanliness of the hole and the quality of subsequent plating. The de-smear step can employ oxidants (such as KMnO4), plasma treatment, or laser desmearing to decompose and remove residual resin or carbides inside the hole. According to the above configuration, the resin residue inside the blind hole 4 can be removed, and there is no significant copper powder residue. Furthermore, the blind hole 4 exposes the base copper layer 2' located on the other side surface (such as the bottom surface) of the substrate 1 to the external environment.

[0052] Furthermore, the blind via 4 has a large aperture. Specifically, the blind via 4 has an upper aperture D1 between 350 micrometers and 450 micrometers, and preferably between 380 micrometers and 420 micrometers, and the aperture ratio of the lower aperture D2 to the upper aperture D1 (i.e., D2 / D1) of the blind via 4 is not less than 70%, and preferably between 75% and 100%. This blind via design with a large aperture and high aperture ratio can help improve the electroplating coverage, reduce the risk of bottom plating voids, and stabilize the subsequent conductivity quality, making it particularly suitable for applications requiring both shielding effect and structural consistency.

[0053] In some embodiments of this utility model, after laser ablation processing, the bottom region of the blind hole 4 may form a transverse overhang structure. The width of the overhang structure can be controlled within about 25 micrometers (μm), preferably within about 15 micrometers, in order to maintain the stability of the hole bottom profile and reduce the risk of electroplating voids.

[0054] The lateral overhang structure refers to the maximum horizontal distance extending from the hole wall outwards from the bottom of the blind hole due to the localized lateral melting and expansion of the substrate material around the bottom of the blind hole caused by the laser thermal effect. This structure mainly appears at the boundary between the blind hole and the unprocessed area and can be effectively controlled by optimizing the laser energy and beam overlap conditions.

[0055] Furthermore, the blind hole 4 has high hole roundness, and the deviation of its outline shape from the ideal circle can be controlled within 10%, with a corresponding roundness value of not less than 90%, preferably in the range of 95% to 100%. This feature helps to improve the uniformity of the hole opening, the electroplating coverage, and the consistency of the process.

[0056] In this paper, roundness refers to the deviation of the upper hole profile from an ideal circle when viewed vertically from the copper window 3 side. The roundness can be calculated by acquiring an image of the hole opening using an optical microscope or image measurement system and analyzing the difference between its maximum circumscribed circle and minimum inscribed circle.

[0057] By controlling the lateral overhang structure and the roundness of the hole, it is possible to ensure that the blind hole has a stable and symmetrical structural morphology, thereby reducing the risk of uneven plating and empty plating inside the hole in the subsequent electroplating stage, and improving the electrical conductivity quality and overall process yield.

[0058] In some embodiments of this invention, the blind hole 4 has a controlled aperture size and upper / lower aperture ratio. Specifically, the upper aperture D1 of the blind hole 4 is approximately 16 mils (approximately 406 micrometers), with an error within ±1 mil. The ratio of the lower aperture D2 to the upper aperture D1 (i.e., D2 / D1) of the blind hole 4 is not less than 80%.

[0059] Regarding process stability, the process capability index (Cpk) corresponding to the structure of the blind hole 4 is not less than 1, preferably not less than 2 (e.g., 2.15), indicating that the aperture control has high consistency and low variability, meeting the requirements for high-yield mass production. The Cpk value refers to the Process Capability Index, which is used to measure whether the actual processing results stably fall within the predetermined specification range.

[0060] Please see Figure 1EAs shown, step S150 includes performing a copper plating step to form a conductive copper layer 5 on the substrate 1. Specifically, the conductive copper layer 5 is deposited on the unetched base copper layer 2 on one side surface (e.g., the top surface) of the substrate 1 by electroplating, chemical plating, sputtering, or other methods, and extends from the edge of the copper window 3, turning to cover the hole wall and bottom of the blind hole 4. Finally, the conductive copper layer 5 can extend downward along the hole shape of the blind hole 4 and contact the base copper layer 2' disposed on the other side surface (e.g., the bottom surface) of the substrate 1 to achieve electrical connection, thereby forming a complete conductive structure. This conductive copper layer 5 provides an effective conductive path, which is beneficial to subsequent copper plating and the electrical quality of the finished product.

[0061] In some embodiments of this invention, after the formation of the conductive copper layer 5 is completed, the manufacturing method of the circuit board structure may selectively include a via-plugging step and an outer layer circuit fabrication step. Specifically, the via-plugging step may include plugging the blind via 4 with a filler material (e.g., resin adhesive) to fill the interior of the blind via and flatten its surface. The filler may include thermosetting epoxy resin, depending on the subsequent application requirements.

[0062] Subsequently, after the via plugging is completed, the outer layer circuit pattern can be fabricated. This outer layer circuit fabrication step may include pattern transfer processes such as photoresist attachment, exposure and development, and etching, thereby forming a predetermined conductive circuit pattern on the conductive copper layer 5. Through the above steps, the outer layer structure integration and conductive path configuration required for the multilayer circuit board can be completed.

[0063] The above-described via plugging and circuit pattern fabrication steps can effectively encapsulate blind vias and enhance structural flatness, improve board surface flatness and reliability, and make subsequent electrical testing and assembly processes more stable.

[0064] The circuit board structure manufacturing method provided by this invention can achieve blind via structures with large apertures, high aperture-to-diameter ratios, and high roundness, while effectively controlling the overhang range and aperture consistency. Combined with steps such as pre-etching copper windows, laser ablation drilling, removal of adhesive residue, and electroplating for conductivity, a circuit board structure with good conductivity, process consistency, and mass production capability can be stably manufactured. This structure is suitable for high-end packaging or high-frequency signal shielding applications, and can be further combined with resin-filled vias and outer layer circuitry to achieve board surface flatness and functional integration, improving product reliability and manufacturing yield.

[0065] [Circuit board structure with large blind vias]

[0066] The above is a description of the manufacturing method for the circuit board structure. Please refer to [link / reference]. Figure 6As shown, another embodiment of the present invention also provides a circuit board structure 100 with a large blind hole, comprising a substrate 1, a base copper layer 2 formed on at least one side surface (e.g., the top surface) of the substrate 1, and another base copper layer 2' formed on the other side surface (e.g., the bottom surface) of the substrate 1.

[0067] The inner side of the base copper layer 2 formed on at least one surface (e.g., the top surface) of the substrate 1 is selectively etched away to form a copper window 3 (the ablation processing area R1 is defined as described above). The copper window 3 is circular and has a characteristic width W (i.e., the diameter of the copper window) between 350 micrometers and 450 micrometers, and preferably between 380 micrometers and 420 micrometers, but the present invention is not limited thereto.

[0068] Furthermore, a blind hole 4 is formed on the inner side of the substrate 1, corresponding to the area below the copper window 3, and the blind hole 4 is spatially connected to the copper window 3.

[0069] As described in the above embodiment, the blind hole 4 is formed by using multiple laser beams L in a laser drilling manner. Based on the ablation processing area R1 defined by the copper window 3, a laser ablation process is performed on the portion of the substrate 1 located in the ablation processing area R1 to remove at least a portion of the substrate 1 (e.g., ...). Figure 1C The material is used to form the blind hole 4.

[0070] like Figure 6 As shown, the blind hole 4 has a truncated cone profile (such as a frustum of a cone) that gradually converges from top to bottom. The blind hole 4 has an upper diameter D1 and a lower diameter D2 (please refer to both). Figure 1D The upper aperture D1 is adjacent to the side of the copper window 3, and the lower aperture D2 is adjacent to the bottom of the blind hole 4. The upper aperture D1 is larger than the lower aperture D2.

[0071] The blind hole 4 has an upper aperture D1 between 350 micrometers and 450 micrometers, and preferably between 380 micrometers and 420 micrometers, and the aperture ratio of the lower aperture D2 to the upper aperture D1 (i.e., D2 / D1) of the blind hole 4 is not less than 70%, and preferably between 75% and 100%.

[0072] In some embodiments of this utility model, after the blind hole 4 is laser ablated, a transverse overhang structure may be formed in its bottom region. The width of the overhang structure can be controlled within about 25 micrometers (μm), preferably within about 15 micrometers.

[0073] Furthermore, the roundness value of the blind hole 4 is not less than 90%, preferably in the range of 95% to 100%.

[0074] Furthermore, the circuit board structure 100 with large blind vias further includes a conductive copper layer 5. The conductive copper layer 5 is deposited on an unetched base copper layer 2 on at least one side surface (such as the top surface) of the substrate 1 by electroplating, chemical plating, sputtering, or other methods, and extends from the copper window 3 to cover the hole wall and bottom of the blind via 4.

[0075] The conductive copper layer 5 extends downward along the shape of the blind hole 4 through the copper window 3 and contacts the base copper layer 2' disposed on the other side surface (such as the bottom surface) of the substrate 1 to achieve electrical connection and form a complete conductive structure.

[0076] The aforementioned circuit board structure utilizes pre-etching of copper windows combined with laser ablation to create large-sized blind vias with specific geometric morphologies. The upper diameter of these blind vias is set between approximately 350 and 450 micrometers, with a diameter-to-diameter ratio exceeding 70%, facilitating uniform deposition of the conductive layer within the via and reliable electrical connection to the underlying copper layer. Furthermore, the conical profile of the blind via and the lateral overhang dimensions of the via walls are effectively controlled to within approximately 25 micrometers, ensuring clear via edges and preventing over-processing of the internal structure or damage to adjacent materials. The high roundness (≥90%) of the via opening ensures process stability and consistency, which is particularly important for improving subsequent electroplating quality and structural reliability.

[0077] [Beneficial Effects of the Embodiments of this Utility Model]

[0078] Overall, the technical solution provided by this utility model embodiment, through the pre-etched window design of the base copper layer combined with laser ablation processing, can stably meet the processing requirements of large-diameter blind holes (16 mils, about 406 micrometers) without changing the existing laser equipment.

[0079] The technical solution provided by this utility model embodiment can effectively improve the problems commonly encountered in traditional laser processing, such as irregular hole contours, excessive residual adhesive residue in the hole, and damage to the copper layer at the bottom of the hole. It can further ensure uniform coating and stable conductivity of the metal plating layer in the hole, improve the reliability, process stability and overall production yield of circuit board products, and is especially suitable for electronic product applications with high density and high performance requirements.

[0080] The above description is only a preferred embodiment of the present utility model and does not limit the patent scope of the present utility model. Therefore, all equivalent technical changes made based on the contents of the present utility model specification and drawings are included within the protection scope of the present utility model.

Claims

1. A circuit board structure with a large blind via, characterized in that, The circuit board structure includes: A substrate; and A base copper layer is formed on at least one side surface of the substrate; wherein a copper window is formed inside the base copper layer, and the copper window has a characteristic width between 350 micrometers and 450 micrometers; A blind hole is formed on the inner side of the substrate, and the blind hole is located below the copper window, corresponding to the ablation processing area defined by the copper window.

2. The circuit board structure with a large blind via according to claim 1, characterized in that, The copper window has the characteristic width between 380 micrometers and 420 micrometers.

3. The circuit board structure with a large blind via according to claim 1, characterized in that, The blind hole has a truncated cone profile that gradually converges from top to bottom, and the blind hole has an upper diameter and a lower diameter, wherein the upper diameter is larger than the lower diameter.

4. The circuit board structure with a large blind via according to claim 3, characterized in that, The upper aperture is between 350 micrometers and 450 micrometers, and the ratio of the lower aperture to the upper aperture is not less than 70%.

5. The circuit board structure with a large blind via according to claim 4, characterized in that, The upper pore size is between 380 micrometers and 420 micrometers, and the ratio of the lower pore size to the upper pore size is between 75% and 100%.

6. The circuit board structure with a large blind via according to claim 1, characterized in that, The circuit board structure further includes: A conductive copper layer covers the base copper layer on at least one side surface of the substrate and extends downward along the hole wall of the blind hole through the copper window, connecting to a base copper layer formed on the other side surface of the substrate.

7. The circuit board structure with a large blind via according to any one of claims 1 to 6, characterized in that, The width of the transverse overhang structure within the blind hole is no greater than 25 micrometers.

8. The circuit board structure with a large blind via according to claim 7, characterized in that, The width of the lateral overhang structure is no more than 15 micrometers.

9. The circuit board structure with a large blind via according to any one of claims 1 to 6, characterized in that, The roundness of the blind hole is not less than 90%.

10. The circuit board structure with a large blind via according to claim 9, characterized in that, The roundness of the blind hole is between 95% and 100%.

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