An operation method for realizing high-aspect-ratio press-contact blind holes

Abstract

The application provides a kind of operation method for realizing high aspect ratio crimping blind hole.The operation method for realizing high aspect ratio crimping blind hole includes the following steps:S1: first pressing, according to customer design data, the target crimping blind hole is disassembled into N ordinary blind hole units, and the whole PCB is disassembled into N pressing procedures at the same time, and the first pressing operation is performed;S2: first drilling, the first blind hole is processed by depth control drilling or laser processing, and the hole diameter of the first blind hole is larger than the final product hole diameter required by the customer.The operation method for realizing high aspect ratio crimping blind hole provided by the application is based on the conventional equipment and mature process of existing PCB production line, without additional special hardware investment, and each parameter has a clear quantitative rule, the process control is clear, and the mass production conversion can be quickly realized, and the coaxial accuracy of each section blind hole is high, the copper layer connection is continuous and reliable, and the conductivity and structural strength of the finished blind hole can meet the crimping requirements.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, and in particular to a method for achieving high aspect ratio crimped blind vias. Background Technology

[0002] Achieving high aspect ratio crimped blind vias refers to creating metallized blind via structures on PCBs with a depth-to-diameter ratio far exceeding the standard blind via, allowing direct crimping of connector pins. Conventional blind vias typically have an aspect ratio of no more than 1:1. This process relies on CCD-controlled precision drilling and layered electroplating to ensure uniform and complete copper layers on the inner walls of deep holes. The bottom of the hole is matched with inner layer capture pads, avoiding penetration of the entire board to save surface wiring space. During assembly, the elastic pins mechanically press the copper layer on the hole wall to form a reliable solderless connection. This solves the problem of traditional crimping only being able to use through-holes and conflicts with high-density wiring on thick boards. The entire process strictly controls the copper thickness of the hole wall, hole diameter tolerance, and hole bottom flatness, making it suitable for high-speed backplanes and miniaturized interconnection scenarios on multi-layer thick boards.

[0003] The high aspect ratio crimping blind via operation first uses a depth-controlled laser drilling machine to precisely process blind vias of a limited depth. After removing adhesive residue and activating the inner wall of the deep via, pulsed layered electroplating is used to ensure uniform copper coating in the deep via. The inner layer pads at the bottom of the via are ground and the hole diameter tolerance is controlled. After the copper thickness of the via wall is tested and found to be up to standard, the elastic pins of the connector are vertically pressed into the blind via. The mechanical interconnect is formed by the deformation of the pins pressing the copper layer of the via wall. The entire process is monitored to ensure that there are no cracks in the via wall and that the crimping pull is qualified. It is suitable for high-density interconnect processing of thick boards.

[0004] When the aspect ratio of the crimped blind via exceeds 1:1, the narrow space inside the via makes it difficult for the plating solution to be effectively exchanged at the bottom of the via during the electroplating process. This can easily lead to quality defects such as insufficient plating thickness and incomplete plating coverage at the bottom of the via, which directly affects the overall electrical performance and crimping reliability of the PCB. It cannot meet the production requirements of high aspect ratio crimped blind vias in high multilayer boards, and has become a process bottleneck restricting the development of high-speed, high multilayer PCB products.

[0005] Therefore, it is necessary to provide an operational method for achieving high aspect ratio crimped blind holes to solve the above-mentioned technical problems. Summary of the Invention

[0006] This invention provides a method for achieving high aspect ratio crimped blind vias, solving the problem that poor chemical exchange at the bottom of the via when the aspect ratio exceeds 1:1, and that plating defects can damage electrical and crimping reliability, thus restricting the production of high-multilayer PCBs.

[0007] To solve the above-mentioned technical problems, the present invention provides a method for realizing high aspect ratio press-fit blind holes, comprising the following steps:

[0008] S1: First pressing: Based on the customer's design data, the target press-fit blind hole is decomposed into N ordinary blind hole units, and the overall PCB stack is simultaneously decomposed into N pressing processes to perform the first pressing operation.

[0009] S2: Initial drilling, using controlled depth drilling or laser processing to machine the first blind hole, the diameter of the first blind hole is larger than the final finished hole diameter required by the customer;

[0010] S3: First electroplating, electroplating process for the first blind hole to form a thick copper hole wall;

[0011] S4: Resin plugging. The first blind hole is plugged with resin to keep the hole surface flat.

[0012] S5: Second lamination: A second lamination is performed on the substrate formed by the first lamination. The thickness of the insulating layer in this lamination is controlled to be less than the diameter of the blind hole, so that the aspect ratio of the blind hole in this section is less than 1:1.

[0013] S6: Secondary drilling. Blind holes are machined on the PCB board after the second lamination using a deep drilling process to ensure that the drilling is coaxial and coincident with the first blind hole.

[0014] S7: Laser Residual Adhesive Removal, using laser technology to remove the resin medium remaining at the bottom of the hole after deep drilling;

[0015] S8: Secondary electroplating, thick copper plating is performed on the second blind hole to make the copper layer on the hole wall of this section electrically connected with the copper layer of the first blind hole;

[0016] S9: Cyclic operation, repeating the process from S5 to S8 until the blind hole diameter and depth requirements of the customer are met.

[0017] Preferably, the finished manufacturing diameter of the crimped blind hole in S1 is in the range of 0.5mm to 5mm.

[0018] Preferably, the number of pressing times N in S1 is calculated by rounding up the ratio of the blind hole depth to the blind hole diameter.

[0019] Preferably, the drilling diameters in S2 and S6 are set in a gradient manner. The diameter of the Nth drilling is designed according to customer requirements, the diameter of the (N-1)th drilling is the customer-required diameter + 3mil, and so on. The diameter of the first drilling is the customer-required diameter + 3 × (N-1)mil.

[0020] Preferably, the plating thickness of the first to N-1 blind holes in S3 and S8 is 2.5mil to 3.5mil, and the plating thickness of the Nth blind hole is 0.8mil to 1.2mil.

[0021] Preferably, the drilling method in S6 is controlled depth back drilling, and the laser-processed hole diameter in S7 is 2-3 mil larger than the drilled hole diameter.

[0022] The method for achieving high aspect ratio press-fit blind holes also includes the following steps:

[0023] S10: Pre-planning of process parameters follows the original stacking and hole type disassembly rules. Based on the total hole depth of the target press-fit blind hole and the finished hole diameter, calculate the number of press-fit times N and the hole diameter gradient of each level. Simultaneously match the plasma treatment parameters corresponding to each blind hole segment. Preset the micro-etching power and processing time according to the hole diameter and step height of this segment to ensure consistent step leveling effect and no damage to the copper substrate of the hole wall.

[0024] S11: Preparation and filling of bottom blind holes. After completing the first pressing operation, the first section of large-diameter blind holes is processed. After thick copper electroplating, resin plugging and board surface grinding, a flat pressing base surface is formed, and the preparation of the bottom blind hole unit is completed.

[0025] S12: Sub-layer lamination and hole processing. The corresponding layer lamination is completed on the basis of the previous substrate. The blind hole in this section is processed by high-precision alignment and deep drilling to ensure that it is coaxial with the blind hole in the lower layer. Then, the laser process is used to burn off the PP resin remaining at the bottom of the hole, and the copper layer end face of the blind hole in the lower layer is fully exposed.

[0026] S13: The hole wall is smoothed by plasma micro-etching. Low-pressure plasma is introduced to uniformly micro-etch the inner wall of this blind hole. The annular step edges formed by the hole diameter gradient are rounded and trimmed. At the same time, the residual drilling sludge, laser residue and surface oxide layer on the hole wall are removed.

[0027] S14: The blind hole in this section is connected by electroplating. After the smoothing process is completed, the process is immediately transferred to the electroplating process to plate copper in this section of blind holes, so that the copper layer on the hole wall in this section forms a continuous and reliable electrical connection with the lower copper layer.

[0028] S15: Multi-stage iterative molding, repeating the process flow from S3 to S5, sequentially completing the stacking, drilling, laser removal of residual adhesive, hole wall smoothing and electroplating connection of the remaining blind holes at each level, until all N-stage blind holes are processed, finally forming a complete high aspect ratio press-fit blind hole.

[0029] By matching the micro-etching energy to the step height and aperture difference of each section, a 10% increase in RF power is applied for every 0.5 mil increase in step height to avoid insufficient finishing of high steps or over-etching of low steps that could damage the copper layer. After grinding the bottom blind holes, a contact profilometer is used to detect the hole opening recess, which is controlled within 0.3 mil to prevent residual air in the hole position during secondary pressing from causing interlayer delamination. The second layer drilling is equipped with a CCD vision alignment system, which is coaxially calibrated with the first blind hole as the reference target. The alignment data is fed back to the drilling machine's main control terminal in real time. Plasma micro-etching uses an RF plasma cleaning machine. The equipment consists of a vacuum chamber, an RF power supply, a gas flow meter, and a vacuum unit connected in series. A 9:1 argon-oxygen mixed gas is introduced to excite plasma. Step finishing and cleaning are achieved through physical bombardment combined with slight oxidation. After processing, the process needs to be transferred in a dust-free environment. In the cycle process, the morphology of the hole wall rounded corners and the uniformity of copper thickness are checked after every two sections are completed to avoid cumulative deviations exceeding the control range.

[0030] Preferably, the working pressure of the low-pressure plasma micro-etching process in S13 is 10~30Pa, the processing time for a single blind hole is 60~120s, and the micro-etching depth of the copper surface of the hole wall is controlled at 0.5~1.5mil.

[0031] Preferably, in step S13, after plasma micro-etching, the transition radius of the annular steps at each level of the hole wall is not less than 0.8 mil, the difference in hole diameter of the steps after etching does not exceed 2 mil, and the hole wall has no obvious sharp edges.

[0032] Preferably, after laser removal of residual adhesive from each blind hole in S12, plasma micro-etching treatment must be completed within 30 minutes. After the treatment is completed, the hole is directly transferred to the electroplating process without the need for an additional water washing process.

[0033] Compared with related technologies, the method for achieving high aspect ratio crimped blind holes provided by the present invention has the following beneficial effects:

[0034] This invention provides a method for producing high aspect ratio press-fit blind vias. This method, through segmented pressing and segmented hole-making process design, overcomes the traditional limitation that the aspect ratio of press-fit blind vias cannot exceed 1:1. It enables stable mass production of high aspect ratio press-fit blind vias, effectively meeting the product design requirements of high-speed, high-multilayer PCBs. From a quality perspective, by breaking down high aspect ratio deep holes into multiple segments of conventional aspect ratio shallow holes, the plating solution within each segment can achieve sufficient circulation and exchange, resulting in uniform and complete plating thickness at the bottom of the hole. This thoroughly improves the problem of poor plating at the bottom of the hole in traditional processes, significantly enhancing product yield and electrical reliability. In terms of adaptability, the solution supports flexible disassembly with N-fold lamination. It can calculate the corresponding number of laminations based on different hole depths and diameters, adapting to various N+M stacked high-multilayer PCB designs. It provides process support for the structural optimization of high-speed products. In terms of mass production feasibility, the overall process is based on existing PCB production line conventional equipment and mature procedures, without the need for additional special hardware investment. Moreover, all parameters have clear quantitative rules, and the process control is clear, facilitating rapid mass production conversion. At the same time, the coaxial precision of each blind via is high, the copper layer connection is continuous and reliable, and the conductivity and structural strength of the finished blind vias can meet the requirements for lamination. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of a first embodiment of the method for achieving high aspect ratio crimped blind holes provided by the present invention;

[0036] Figure 2 This is a flowchart provided for the present invention;

[0037] Figure 3 A schematic diagram of the first pressing step is provided for this invention;

[0038] Figure 4 A schematic diagram of the first drilling is provided for this invention;

[0039] Figure 5 A schematic diagram of the first electroplating step is provided for this invention;

[0040] Figure 6 A schematic diagram of resin plugging is provided for the present invention;

[0041] Figure 7 A schematic diagram of the second pressing is provided for this invention;

[0042] Figure 8 A schematic diagram of secondary drilling is provided for this invention;

[0043] Figure 9 A schematic diagram of laser removal of residual adhesive is provided for this invention;

[0044] Figure 10 A schematic diagram of secondary electroplating is provided for this invention;

[0045] Figure 11 This is a schematic diagram of a second embodiment of the method for achieving high aspect ratio crimped blind holes provided by the present invention. Detailed Implementation

[0046] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0047] First Embodiment

[0048] Please refer to the following: Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 10 ,in, Figure 1 This is a schematic diagram of a first embodiment of the method for achieving high aspect ratio crimped blind holes provided by the present invention; Figure 2 This is a flowchart provided for the present invention; Figure 3 A schematic diagram of the first pressing step is provided for this invention; Figure 4 A schematic diagram of the first drilling is provided for this invention; Figure 5 A schematic diagram of the first electroplating step is provided for this invention; Figure 6 A schematic diagram of resin plugging is provided for the present invention; Figure 7 A schematic diagram of the second pressing is provided for this invention; Figure 8 A schematic diagram of secondary drilling is provided for this invention; Figure 9 A schematic diagram of laser removal of residual adhesive is provided for this invention; Figure 10 A schematic diagram of secondary electroplating is provided for this invention. The method for achieving high aspect ratio press-fit blind vias includes the following steps:

[0049] S1: First pressing: Based on the customer's design data, the target press-fit blind hole is decomposed into N ordinary blind hole units, and the overall PCB stack is simultaneously decomposed into N pressing processes to perform the first pressing operation.

[0050] S2: Initial drilling, using controlled depth drilling or laser processing to machine the first blind hole, the diameter of the first blind hole is larger than the final finished hole diameter required by the customer;

[0051] S3: First electroplating, electroplating process for the first blind hole to form a thick copper hole wall;

[0052] S4: Resin plugging. The first blind hole is plugged with resin to keep the hole surface flat.

[0053] S5: Second lamination: A second lamination is performed on the substrate formed by the first lamination. The thickness of the insulating layer in this lamination is controlled to be less than the diameter of the blind hole, so that the aspect ratio of the blind hole in this section is less than 1:1.

[0054] S6: Secondary drilling. Blind holes are machined on the PCB board after the second lamination using a deep drilling process to ensure that the drilling is coaxial with the first blind hole.

[0055] S7: Laser Residual Adhesive Removal, using laser technology to remove the resin medium remaining at the bottom of the hole after deep drilling;

[0056] S8: Secondary electroplating, thick copper plating is performed on the second blind hole to make the copper layer on the hole wall of this section electrically connected with the copper layer of the first blind hole;

[0057] S9: Cyclic operation, repeating the process from S5 to S8 until the blind hole diameter and depth requirements of the customer are met.

[0058] During the execution of this method, corresponding equipment and meticulous process control are required. The pressing operation utilizes a vacuum hot press, equipped with independently temperature-controlled upper and lower hot plates and a vacuum chamber. Pressing is performed in stages, increasing pressure and temperature to melt and bond the prepreg, achieving a tight interlayer bond. When disassembling the stack, the adhesive content of each pressed layer's prepreg must be matched synchronously to avoid uneven adhesive overflow or pressing depressions at the resin plugging points. In the drilling process, a depth-controlled drill uses an air-bearing spindle with a depth feedback sensor to monitor the drill bit's feed depth in real time to ensure depth control accuracy. Laser drilling uses an ultraviolet nanosecond laser, achieving precise hole shaping through galvanometer scanning. After the first drilling stage is completed, [further steps are required]. The reference hole position deviation is checked using an optical hole position detector, and the coaxiality deviation must be controlled within 2 mil. Resin plugging is performed using a horizontal plugging machine, where resin is filled into the hole by applying pressure with a scraper. After plugging, the board surface is polished with a belt grinder to ensure that the flatness deviation of the board surface does not exceed 0.5 mil. Laser removal of residual glue uses a CO2 laser, equipped with a CCD vision alignment system to align the hole position. During ablation, a circular scan is performed along the hole wall to avoid overburning and damaging the underlying copper surface. Electroplating uses a vertical rack plating line, and the exchange of chemicals in the hole is enhanced by cathode oscillation. The current density is set separately for each section. In the cycle process, the copper thickness and conductivity of the hole must be checked after each section is completed to avoid cumulative deviation.

[0059] The finished manufacturing diameter of the crimped blind hole in S1 ranges from 0.5mm to 5mm.

[0060] The number of pressing times N in S1 is calculated by rounding up the ratio of the blind hole depth to the blind hole diameter.

[0061] In S2 and S6, the borehole diameter is set in a gradient. The borehole diameter of the Nth borehole is designed according to the customer's requirements, the borehole diameter of the N-1th borehole is the customer's required diameter + 3mil, and so on. The borehole diameter of the first borehole is the customer's required diameter + 3×(N-1)mil.

[0062] The plating thickness of the first to N-1 blind holes in S3 and S8 is 2.5mil to 3.5mil, and the plating thickness of the Nth blind hole is 0.8mil to 1.2mil.

[0063] The drilling method in S6 is controlled depth back drilling, and the laser-processed hole diameter in S7 is 2-3 mil larger than the drilled hole diameter.

[0064] The working principle of the method for achieving high aspect ratio press-fit blind holes provided by this invention is as follows:

[0065] This design approach, employing a modular, layered approach, breaks through the aspect ratio limitations of traditional one-time hole-forming processes. Traditional processes involve drilling the entire board at a controlled depth to create blind holes in a single operation. As the hole depth increases, the internal space gradually narrows, making it difficult for the electroplating solution to circulate sufficiently at the bottom of the hole. This easily leads to quality defects such as thin plating at the bottom, incomplete coverage, or even exposed substrate. Therefore, conventional mass production processes in the industry can only cover blind hole fabrication with aspect ratios up to 1:1. This method breaks down a single, deep, high aspect ratio blind hole into multiple shallow blind hole units with smaller depths along the board thickness direction. Simultaneously, it matches this with N step-by-step pressing processes, ensuring that the aspect ratio of each blind hole segment is controlled within the mature 1:1 process range. This method fundamentally solves the problem of chemical exchange in deep hole electroplating. In actual production, processing begins with the bottom layer of blind holes. After drilling and thick copper electroplating, resin is used to plug the holes and fill them, forming a flat and dense base surface to support subsequent pressing operations. This avoids the risk of depressions or delamination during the pressing process. After each layer pressing is completed, the corresponding layer of blind holes is drilled with high precision to ensure that the hole positions of each segment are coaxial and coincident. Then, the residual insulating resin at the bottom of the hole is burned off with a laser process to fully expose the copper end face of the lower layer of blind holes. Finally, electroplating is used to form a continuous and reliable conductive whole with copper layers on the hole walls of each segment. This combines multiple conventional blind holes into a high aspect ratio press-fit blind hole with a complete structure and continuous electrical performance.

[0066] Compared with related technologies, the method for achieving high aspect ratio crimped blind holes provided by the present invention has the following beneficial effects:

[0067] This method, through segmented lamination and segmented hole fabrication, overcomes the traditional limitation that the aspect ratio of crimped blind vias cannot exceed 1:1. It enables stable mass production of high aspect ratio crimped blind vias, effectively meeting the product design requirements of high-speed, high-multilayer PCBs. From a quality perspective, by breaking down high aspect ratio deep holes into multiple segments of conventional aspect ratio shallow holes, the plating solution within each segment can achieve sufficient circulation and exchange, resulting in uniform and complete plating thickness at the bottom of the hole. This thoroughly improves the problem of poor plating at the bottom of the hole in traditional processes, significantly enhancing product yield and electrical reliability. From a design adaptability perspective, the solution supports N times... The flexible disassembly of the lamination process allows for the calculation of the corresponding number of laminations based on different hole depths and diameters. It is compatible with various N+M stacked high-multilayer PCB designs, providing process support for the structural optimization of high-speed products. From the perspective of mass production feasibility, the overall process is based on existing PCB production line conventional equipment and mature procedures, requiring no additional special hardware investment. Moreover, all parameters have clear quantitative rules, and the process control is clear, facilitating rapid mass production conversion. At the same time, the coaxial precision of each blind via is high, the copper layer connection is continuous and reliable, and the conductivity and structural strength of the finished blind vias can meet the requirements for lamination.

[0068] Second Embodiment

[0069] Please refer to the following: Figure 11 , Figure 11 This is a schematic diagram of a second embodiment of the method for realizing high aspect ratio crimped blind holes provided by the present invention. Based on the method for realizing high aspect ratio crimped blind holes provided by the first embodiment of this application, the second embodiment of this application proposes another method for realizing high aspect ratio crimped blind holes. The second embodiment is merely a preferred embodiment of the first embodiment, and the implementation of the second embodiment will not affect the separate implementation of the first embodiment.

[0070] Specifically, the difference in the method for realizing a high aspect ratio press-fit blind hole provided in the second embodiment of this application is that the method for realizing a high aspect ratio press-fit blind hole further includes the following steps:

[0071] S10: Pre-planning of process parameters follows the original stacking and hole type disassembly rules. Based on the total hole depth of the target press-fit blind hole and the finished hole diameter, calculate the number of press-fit times N and the hole diameter gradient of each level. Simultaneously match the plasma treatment parameters corresponding to each blind hole segment. Preset the micro-etching power and processing time according to the hole diameter and step height of this segment to ensure consistent step leveling effect and no damage to the copper substrate of the hole wall.

[0072] S11: Preparation and filling of bottom blind holes. After completing the first pressing operation, the first section of large-diameter blind holes is processed. After thick copper electroplating, resin plugging and board surface grinding, a flat pressing base surface is formed, and the preparation of the bottom blind hole unit is completed.

[0073] S12: Sub-layer lamination and hole processing. The corresponding layer lamination is completed on the basis of the previous substrate. The blind hole in this section is processed by high-precision alignment and deep drilling to ensure that it is coaxial with the blind hole in the lower layer. Then, the laser process is used to burn off the PP resin remaining at the bottom of the hole, and the copper layer end face of the blind hole in the lower layer is fully exposed.

[0074] S13: The hole wall is smoothed by plasma micro-etching. Low-pressure plasma is introduced to uniformly micro-etch the inner wall of this blind hole. The annular step edges formed by the hole diameter gradient are rounded and trimmed. At the same time, the residual drilling sludge, laser residue and surface oxide layer on the hole wall are removed.

[0075] S14: The blind hole in this section is connected by electroplating. After the smoothing process is completed, the process is immediately transferred to the electroplating process to plate copper in this section of blind holes, so that the copper layer on the hole wall in this section forms a continuous and reliable electrical connection with the lower copper layer.

[0076] S15: Multi-stage iterative molding, repeating the process flow from S3 to S5, sequentially completing the stacking, drilling, laser removal of residual adhesive, hole wall smoothing and electroplating connection of the remaining blind holes at each level, until all N-stage blind holes are processed, finally forming a complete high aspect ratio press-fit blind hole.

[0077] By matching the micro-etching energy to the step height and aperture difference of each section, a 10% increase in RF power is applied for every 0.5 mil increase in step height to avoid insufficient finishing of high steps or over-etching of low steps that could damage the copper layer. After grinding the bottom blind holes, a contact profilometer is used to detect the hole opening depression, which is controlled within 0.3 mil to prevent residual air in the hole position during secondary pressing from causing interlayer delamination. The second layer drilling is equipped with a CCD vision alignment system, which is coaxially calibrated with the first blind hole as the reference target. The alignment data is fed back to the drilling machine's main control terminal in real time. Plasma micro-etching uses an RF plasma cleaning machine, which consists of a vacuum chamber, RF power supply, gas flow meter and vacuum unit connected in series. A 9:1 argon-oxygen mixed gas is introduced to excite plasma. Step finishing and cleaning are achieved through physical bombardment combined with slight oxidation. After processing, the process needs to be transferred in a dust-free environment. In the cycle process, the morphology of the hole wall rounded corners and the uniformity of copper thickness are checked after every two sections are completed to avoid cumulative deviations exceeding the control range.

[0078] The working pressure of the low-pressure plasma micro-etching process in S13 is 10~30Pa, the processing time for a single blind hole is 60~120s, and the micro-etching depth of the copper surface of the hole wall is controlled at 0.5~1.5mil.

[0079] After plasma micro-etching in S13, the transition radius of the annular steps of each level of the hole wall is not less than 0.8 mil, the difference in hole diameter of the steps after repair does not exceed 2 mil, and there are no obvious sharp edges on the hole wall.

[0080] After laser removal of residual adhesive from each blind hole in S12, plasma micro-etching treatment must be completed within 30 minutes. After the treatment is completed, the hole is directly transferred to the electroplating process without the need for an additional water washing process.

[0081] Compared with related technologies, the method for achieving high aspect ratio crimped blind holes provided by the present invention has the following beneficial effects:

[0082] Based on the pore size gradient structure characteristics of the original segmented hole-making process, and addressing the annular step defects formed on the hole walls by the progressively narrowing pore size, this method utilizes the isotropic bombardment of low-pressure plasma to precisely micro-etch the inner walls of each blind hole before electroplating. By controlling the amount of micro-etching, the sharp edge of the step is smoothed into a rounded corner, while simultaneously removing drilling residue and resin debris from drilling and laser processes. This activates the surface energy of the hole walls, improving the wetting and deposition uniformity of the electroplating solution within the hole. This addresses issues such as thin plating, pinholes, and insufficient adhesion caused by uneven electric field distribution at the steps at the substrate level. This method achieves breakthroughs while fully preserving the original process. Under the premise of limiting the core capabilities by aspect ratio, the hole wall quality and long-term reliability of blind vias are further improved. The smoothing of the steps eliminates the stress concentration points of the plating, and the copper layer is less likely to be scratched and fall off during crimping and insertion, which effectively improves the crimping durability. After the hole wall cleanliness and activation are improved, the proportion of plating voids and poor coverage can be significantly reduced, which further improves the product yield. At the same time, the process is highly compatible, adding only one processing step to the original process, without changing the core equipment and main parameter system. It can be quickly adapted to existing production lines for mass production and can flexibly match the production needs of different products with ordinary quality and high reliability requirements.

[0083] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for achieving high aspect ratio crimped blind holes, characterized in that, Includes the following steps: S1: First pressing: Based on the customer's design data, the target press-fit blind hole is decomposed into N ordinary blind hole units, and the overall PCB stack is simultaneously decomposed into N pressing processes to perform the first pressing operation. S2: Initial drilling, using controlled depth drilling or laser processing to machine the first blind hole, the diameter of the first blind hole is larger than the final finished hole diameter required by the customer; S3: First electroplating, electroplating process for the first blind hole to form a thick copper hole wall; S4: Resin plugging. The first blind hole is plugged with resin to keep the hole surface flat. S5: Second lamination: A second lamination is performed on the substrate formed by the first lamination. The thickness of the insulating layer in this lamination is controlled to be less than the diameter of the blind hole, so that the aspect ratio of the blind hole in this section is less than 1:

1. S6: Secondary drilling. Blind holes are machined on the PCB board after the second lamination using a deep drilling process to ensure that the drilling is coaxial and coincident with the first blind hole. S7: Laser Residual Adhesive Removal, using laser technology to remove the resin medium remaining at the bottom of the hole after deep drilling; S8: Secondary electroplating, thick copper plating is performed on the second blind hole to make the copper layer on the hole wall of this section electrically connected with the copper layer of the first blind hole; S9: Cyclic operation, repeating the process from S5 to S8 until the blind hole diameter and depth requirements of the customer are met.

2. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, The finished manufacturing diameter of the crimped blind hole in S1 ranges from 0.5mm to 5mm.

3. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, The number of pressing times N in S1 is calculated by rounding up the ratio of the blind hole depth to the blind hole diameter.

4. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, In S2 and S6, the borehole diameter is set in a gradient. The borehole diameter of the Nth borehole is designed according to the customer's requirements, the borehole diameter of the N-1th borehole is the customer's required diameter + 3mil, and so on. The borehole diameter of the first borehole is the customer's required diameter + 3×(N-1)mil.

5. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, The plating thickness of the first to N-1 blind holes in S3 and S8 is 2.5mil to 3.5mil, and the plating thickness of the Nth blind hole is 0.8mil to 1.2mil.

6. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, The drilling method in S6 is controlled depth back drilling, and the laser-processed hole diameter in S7 is 2-3 mil larger than the drilled hole diameter.

7. The method for achieving high aspect ratio crimped blind holes according to claim 1, characterized in that, It also includes the following steps: S10: Pre-planning of process parameters follows the original stacking and hole type disassembly rules. Based on the total hole depth of the target press-fit blind hole and the finished hole diameter, calculate the number of press-fit times N and the hole diameter gradient of each level. Simultaneously match the plasma treatment parameters corresponding to each blind hole segment. Preset the micro-etching power and processing time according to the hole diameter and step height of this segment to ensure consistent step leveling effect and no damage to the copper substrate of the hole wall. S11: Preparation and filling of bottom blind holes. After completing the first pressing operation, the first section of large-diameter blind holes is processed. After thick copper electroplating, resin plugging and board surface grinding, a flat pressing base surface is formed, and the preparation of the bottom blind hole unit is completed. S12: Sub-layer lamination and hole processing. The corresponding layer lamination is completed on the basis of the previous substrate. The blind hole in this section is processed by high-precision alignment and deep drilling to ensure that it is coaxial with the blind hole in the lower layer. Then, the laser process is used to burn off the PP resin remaining at the bottom of the hole, and the copper layer end face of the blind hole in the lower layer is fully exposed. S13: The hole wall is smoothed by plasma micro-etching. Low-pressure plasma is introduced to uniformly micro-etch the inner wall of this blind hole. The annular step edges formed by the hole diameter gradient are rounded and trimmed. At the same time, the residual drilling sludge, laser residue and surface oxide layer on the hole wall are removed. S14: The blind hole in this section is connected by electroplating. After the smoothing process is completed, the process is immediately transferred to the electroplating process to plate copper in this section of blind holes, so that the copper layer on the hole wall in this section forms a continuous and reliable electrical connection with the lower copper layer. S15: Multi-stage iterative molding, repeating the process flow from S3 to S5, sequentially completing the stacking, drilling, laser removal of residual adhesive, hole wall smoothing and electroplating connection of the remaining blind holes at each level, until all N-stage blind holes are processed, finally forming a complete high aspect ratio press-fit blind hole.

8. The method for achieving high aspect ratio crimped blind holes according to claim 7, characterized in that, The working pressure of the low-pressure plasma micro-etching process in S13 is 10~30Pa, the processing time for a single blind hole is 60~120s, and the micro-etching depth of the copper surface of the hole wall is controlled at 0.5~1.5mil.

9. The method for achieving high aspect ratio crimped blind holes according to claim 7, characterized in that, After plasma micro-etching in S13, the transition radius of the annular steps of each level of the hole wall is not less than 0.8 mil, the difference in hole diameter of the steps after repair does not exceed 2 mil, and there are no obvious sharp edges on the hole wall.

10. The method for achieving high aspect ratio crimped blind holes according to claim 7, characterized in that, After laser removal of residual adhesive from each blind hole in S12, plasma micro-etching treatment must be completed within 30 minutes. After the treatment is completed, the hole is directly transferred to the electroplating process without the need for an additional water washing process.

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