High aspect ratio PCB board processing method and PCB board

Abstract

The application discloses a high-aspect-ratio PCB processing method and a PCB, and belongs to the technical field of PCB design and manufacturing. The method comprises the following steps: cleaning, film pressing, exposure, development and etching of a core plate to form a circuit pattern and a laser drilling window area on a copper coating layer; after removing glue, an insulating layer of the window area is ablated by laser to form an inverted trapezoidal laser blind hole until a target pad on the other side of the core plate is exposed; the core plate after laser drilling is laminated and pressed with PP material and copper foil to fill the laser blind hole with the PP material; drilling is performed on the PCB after pressing at a position corresponding to the laser blind hole; and finally, copper plating is performed on the hole wall to realize interlayer conduction. The application replaces the glass fiber cloth + resin at the original drilling position with PP material through inner layer laser drilling, solves the ICD (internal connection abnormality) problem caused by residue of glue after drilling of high-grade material, and guarantees the electrical function and reliability of the PCB.

Description

Technical Field

[0001] This invention relates to a high aspect ratio PCB board processing method and PCB board, belonging to the field of PCB design and manufacturing technology. Background Technology

[0002] The current standard PCB manufacturing process involves etching patterns onto the inner core board, stacking multiple core boards, bonding the prepreg (PP) sheet to the core board using a lamination process, and then performing drilling and electroplating. In high-grade materials and high aspect ratio PCBs, smear residue is easily generated after drilling. Pre-plating desmearing processes (such as plasma or desmear treatment) often fail to completely remove the residue deep within the vias, leading to inner-layer connection defects (ICD) and severely impacting the PCB's electrical functionality and product reliability. Summary of the Invention

[0003] The purpose of this invention is to provide a high aspect ratio PCB board processing method and PCB board. By pre-drilling the inner core board with laser, the glass fiber cloth + resin area that originally needed to be drilled in the outer layer after lamination is replaced with PP material, thereby solving the problem that it is difficult to completely remove adhesive residue from high-grade materials after drilling and before electroplating.

[0004] To achieve the above objectives / to solve the above technical problems, the present invention is implemented using the following technical solution.

[0005] On one hand, the present invention provides a method for processing high aspect ratio PCB boards, comprising: S1: The core board with copper cladding on both sides is cleaned and the copper surface is roughened, and one of the copper cladding layers is etched with the target pad. S2: A dry film layer is set on the copper cladding surface of the core board; S3: A film with circuit patterns is placed above the dry film layer on the side of the core board where no target pads are set. By exposing it with ultraviolet light, the dry film corresponding to the light-transmitting area on the film undergoes a photopolymerization reaction, thereby transferring the circuit patterns on the film onto the dry film layer. S4: Remove the unpolymerized dry film layer after exposure by developing; S5: Etching removes the copper coating not protected by the dry film layer, forming circuit patterns and window areas for subsequent laser drilling on the copper coating. S6: Remove the remaining polymerized dry film layer from the surface of the copper coating; S7: The insulating layer of the windowed area is ablated by laser until the target pad on the other side of the core board is exposed, forming a core board with an inverted trapezoidal laser blind hole; S8: Stack and press several sets of core boards with inverted trapezoidal laser blind holes and PP material together, so that the PP material fills the insulating layer area burned off by the laser blind holes, and obtains a high aspect ratio PCB board blank. S9: Drill holes in the high aspect ratio PCB blank at the positions corresponding to the laser blind hole area; S10: Copper plating is applied to the hole walls after drilling to achieve interlayer conductivity in high aspect ratio PCBs.

[0006] Furthermore, in S7, the inverted trapezoidal laser blind hole formed by laser ablation satisfies the ratio of the bottom diameter to the opening diameter being ≥80%.

[0007] Furthermore, the target pad is larger than the bottom diameter of the inverted trapezoidal laser blind hole.

[0008] Furthermore, in S5, the window area for laser drilling is designed to be at least 19.9mil, which facilitates the improvement of PCB layout efficiency and performance, and also facilitates mathematical modeling to optimize the functional connectivity and signal transmission of the PCB. The corresponding target pad window size is at least 3mil larger on each side than the window area, setting a safety distance to absorb laser deviation and prevent the laser from cutting the copper edge.

[0009] Furthermore, the thickness of the PP material is greater than or equal to the thickness of the copper coating on the core board surface. By selecting a PP material that is the same as or thicker than the copper coating on the core board surface, the laser ablation area and other etched areas can be well filled during the lamination process.

[0010] Furthermore, in S7, laser drilling is performed using a burn-through method until the insulation layer is completely burned away.

[0011] Furthermore, in S10, the hole walls are cleaned before electroplating to ensure the adhesion of the plating layer.

[0012] Secondly, the present invention provides a high aspect ratio PCB board, which is formed by the above-mentioned high aspect ratio PCB board processing method.

[0013] Compared with existing technologies, the beneficial effects achieved by this invention are as follows: By introducing laser drilling technology in the inner core board stage, the glass fiber cloth + resin area that originally needed to be drilled in the outer layer after lamination can be removed and replaced with PP material before lamination. Since the PP material is bonded to the core board after lamination, the adhesive residue generated during subsequent drilling has different characteristics from that of traditional glass fiber cloth + resin material, and is easier to remove in the pre-plating treatment. The innovative design of this invention effectively solves the problem of difficult removal of adhesive residue after drilling, during Plasma and Desmear processes of high-grade materials, thereby eliminating the ICD (Interconnection Disorder) problem after electroplating and ensuring the electrical function of the PCB and product reliability. Attached Figure Description

[0014] Figure 1 The diagram shown is a flowchart of the present invention. Detailed Implementation

[0015] It should be noted that: The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of the present invention and the specific features in the embodiments are detailed descriptions of the technical solution of the present invention, rather than limitations thereof. In the absence of conflict, the embodiments of the present invention and the technical features in the embodiments can be combined with each other.

[0016] The term "and / or" simply describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. Additionally, the character " / " generally indicates that the preceding and following related objects have an "or" relationship. Example

[0017] like Figure 1 The embodiment shown provides a method for processing a high aspect ratio PCB board, and the specific steps are as follows: S1. Pre-treatment: The core board with copper cladding on both sides is cleaned and the copper surface is roughened. One of the copper cladding layers is etched with a target pad to enhance the adhesion between the subsequent dry film layer and the copper surface. The target pad refers to the pad-shaped copper structure retained by etching process on the copper cladding layer on one side of the core board, which corresponds to the window area on the other side of the core board and serves as a laser stop layer during the laser drilling process. S2. Lamination: A dry film layer is laminated onto the copper cladding surface of the core board to prepare for subsequent image transfer; S3. Exposure: A film with circuit patterns is placed above the dry film layer on the side of the core board without target pads. By exposing it with ultraviolet light, the dry film corresponding to the light-transmitting area on the film undergoes a photopolymerization reaction, thereby transferring the circuit patterns on the film onto the dry film layer. S4. Development: The unpolymerized dry film layer from the exposure process is removed by the developer to expose the copper surface area to be etched; S5. Etching: Etching removes the copper coating not protected by the dry film layer, forming circuit patterns and window areas for subsequent laser drilling on the copper coating; the areas requiring laser drilling are also etched to remove the copper coating in this step, exposing the insulating layer. S6. Removal of adhesive: Remove the polymerized dry film layer from the core board surface to expose the complete circuit pattern and the laser-drilled window area; S7. Laser Drilling: By adjusting the appropriate pulse width, energy, number of shots, and mask parameters, the laser beam is used to ablate the insulating layer in the windowed area using a burning-around method until the target pad on the other side of the core board is exposed, forming an inverted trapezoidal laser blind via. Due to the Gaussian beam characteristics of the laser, the energy density is high and the ablation rate is fast in the center of the hole, while the energy density at the edge of the hole wall decreases and the ablation rate slows down, ultimately forming a core board with an inverted trapezoidal laser blind via. The ratio of the bottom diameter to the opening diameter of the hole is required to be ≥80%. Because the required laser hole diameter is relatively large, a burning-around method is required to gradually remove the insulating layer through multiple ablations to ensure that the bottom of the hole is clean and exposes the target pad without any residue. S8. Lamination: Several sets of core boards with inverted trapezoidal laser blind holes and PP material are stacked and laminated. During the lamination process, the PP material is heated and flows, filling the insulating layer area that has been ablated by the laser drilling, thus playing the role of lamination and filling, and obtaining a high aspect ratio PCB board blank. The thickness of the selected PP material should be greater than or equal to the thickness of the copper coating on the surface of the core board to ensure that the laser ablation area and the remaining etched area can be completely filled during the lamination process. S9. Drilling: Mechanical drilling is performed at the position corresponding to the laser blind hole area on the high aspect ratio PCB board blank; S10. Electroplating: Clean the hole walls after drilling, and then plate copper on the hole walls to achieve interlayer conductivity of high aspect ratio PCB boards. Since laser drilling openings need to be etched on one side of the core board and corresponding target pads need to be etched on the other side; taking the traditional 7.9mil drilling size as an example, considering the alignment accuracy of subsequent lamination and drilling, the laser drilling area on the corresponding inner core board should be designed to be at least 19.9mil in size; the design of the corresponding target pads needs to reserve sufficient alignment tolerance, so the size of the target pad opening should be at least 3mil larger on one side than the laser drilling opening. By using the above processing method, the fiberglass cloth and resin that originally needed to be drilled after pressing were replaced with PP material before pressing, which fundamentally solved the problem of difficult-to-remove adhesive residue after drilling high-grade materials. Example

[0018] Based on the same inventive concept as Embodiment 1, this embodiment provides a high aspect ratio PCB board, which is formed by processing the high aspect ratio PCB board processing method described in Embodiment 1.

[0019] In summary, this embodiment fundamentally solves the ICD problem of high aspect ratio, high-grade material PCBs by creating laser blind holes in the inner core board and filling them with PP, thereby replacing the fiberglass cloth + resin area that is prone to adhesive residue in high-grade material PCBs with PP material in advance. It has significant innovation and practical value.

[0020] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for processing high aspect ratio PCB boards, characterized in that, include: S1: The core board with copper cladding on both sides is cleaned and the copper surface is roughened, and one of the copper cladding layers is etched with the target pad. S2: A dry film layer is set on the copper cladding surface of the core board; S3: A film with circuit patterns is placed above the dry film layer on the side of the core board where no target pads are set. By exposing it with ultraviolet light, the dry film corresponding to the light-transmitting area on the film undergoes a photopolymerization reaction, thereby transferring the circuit patterns on the film onto the dry film layer. S4: Remove the unpolymerized dry film layer after exposure by developing; S5: Etching removes the copper coating not protected by the dry film layer, forming circuit patterns and window areas for subsequent laser drilling on the copper coating. S6: Remove the remaining polymerized dry film layer from the surface of the copper coating; S7: The insulating layer of the windowed area is ablated by laser until the target pad on the other side of the core board is exposed, forming a core board with an inverted trapezoidal laser blind hole; S8: Stack and press several sets of core boards with inverted trapezoidal laser blind holes and PP material together, so that the PP material fills the insulating layer area burned off by the laser blind holes, and obtains a high aspect ratio PCB board blank. S9: Drill holes in the high aspect ratio PCB blank at the positions corresponding to the laser blind hole area; S10: Copper plating is applied to the hole walls after drilling to achieve interlayer conductivity in high aspect ratio PCBs.

2. The high aspect ratio PCB board processing method according to claim 1, characterized in that, In S7, the inverted trapezoidal laser blind hole formed by laser ablation satisfies the ratio of the bottom diameter to the opening diameter being ≥80%.

3. The high aspect ratio PCB board processing method according to claim 1, characterized in that, The target pad is larger than the bottom diameter of the inverted trapezoidal laser blind hole.

4. The high aspect ratio PCB board processing method according to claim 3, characterized in that, In S5, the window area for laser drilling is designed to be at least 19.9 mil, and the corresponding target pad window size is at least 3 mil larger on each side than the window area.

5. The high aspect ratio PCB board processing method according to claim 1, characterized in that, The thickness of the PP material is greater than or equal to the thickness of the copper cladding on the core board surface.

6. The high aspect ratio PCB board processing method according to claim 1, characterized in that, In the S7, laser drilling is performed using a burn-through method until the insulation layer is completely burned away.

7. The high aspect ratio PCB board processing method according to claim 1, characterized in that, In S10, the hole walls are cleaned before electroplating.

8. A high aspect ratio PCB board, characterized in that, It is formed by processing a high aspect ratio PCB board using any one of claims 1 to 7.

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